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582 results on '"Nousek, J"'

1. Swift/UVOT discovery of Swift J221951-484240: a UV luminous ambiguous nuclear transient

Author: Oates, S. R., Kuin, N. P. M., Nicholl, M., Marshall, F., Ridley, E., Boutsia, K., Breeveld, A. A., Buckley, D. A. H., Cenko, S. B., De Pasquale, M., Edwards, P. G., Gromadzki, M., Gupta, R., Laha, S., Morrell, N., Orio, M., Pandey, S. B., Page, M. J., Page, K. L., Parsotan, T., Rau, A., Schady, P., Stevens, J., Brown, P. J., Evans, P. A., Gronwall, C., Kennea, J. A., Klingler, N. J., Siegel, M. H., Tohuvavohu, A., Ambrosi, E., Barthelmy, S. D., Beardmore, A. P., Bernardini, M. G., Bonnerot, C., Campana, S., Caputo, R., Ciroi, S., Cusumano, G., D'Ai, A., D'Avanzo, P., D'Elia, V., Giommi, P., Hartmann, D. H., Krimm, H. A., Malesani, D. B., Melandri, A., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Pagani, C., Palmer, D. M., Perri, M., Racusin, J. L., Sakamoto, T., Sbarufatti, B., Schlieder, J. E., Tagliaferri, G., Troja, E., and Xu, D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of Swift J221951-484240 (hereafter: J221951), a luminous slow-evolving blue transient that was detected by the Neil Gehrels Swift Observatory Ultra-violet/Optical Telescope (Swift/UVOT) during the follow-up of Gravitational Wave alert S190930t, to which it is unrelated. Swift/UVOT photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking black body with an approximately constant temperature of T~2.5x10^4 K. At a redshift z=0.5205, J221951 had a peak absolute magnitude of M_u,AB = -23 mag, peak bolometric luminosity L_max=1.1x10^45 erg s^-1 and a total radiated energy of E>2.6x10^52 erg. The archival WISE IR photometry shows a slow rise prior to a peak near the discovery date. Spectroscopic UV observations display broad absorption lines in N V and O VI, pointing toward an outflow at coronal temperatures. The lack of emission in the higher H~Lyman lines, N I and other neutral lines is consistent with a viewing angle close to the plane of the accretion or debris disc. The origin of J221951 can not be determined with certainty but has properties consistent with a tidal disruption event and the turn-on of an active galactic nucleus., Comment: 37 pages (25 main + 12 supplementary), submitted to MNRAS
Published: 2023

2. Swift/UVOT follow-up of Gravitational Wave Alerts in the O3 era

Author: Oates, S. R., Marshall, F. E., Breeveld, A. A., Kuin, N. P. M., Brown, P. J., De Pasquale, M., Evans, P. A., Fenney, A. J., Gronwall, C., Kennea, J. A., Klingler, N. J., Page, M. J., Siegel, M. H., Tohuvavohu, A., Ambrosi, E., Barthelmy, S. D., Beardmore, A. P., Bernardini, M. G., Campana, S., Caputo, R., Cenko, S. B., Cusumano, G., D'Aì, A., D'Avanzo, P., D'Elia, V., Giommi, P., Hartmann, D. H., Krimm, H. A., Laha, S., Malesani, D. B., Melandri, A., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Pagani, C., Page, K. L., Palmer, D. M., Perri, M., Racusin, J. L., Sakamoto, T., Sbarufatti, B., Schlieder, J. E., Tagliaferri, G., and Troja, E.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: In this paper, we report on the observational performance of the Swift Ultra-violet/Optical Telescope (UVOT) in response to the Gravitational Wave alerts announced by the Advanced Laser Interferometer Gravitational Wave Observatory and the Advanced Virgo detector during the O3 period. We provide the observational strategy for follow-up of GW alerts and provide an overview of the processing and analysis of candidate optical/UV sources. For the O3 period, we also provide a statistical overview and report on serendipitous sources discovered by Swift/UVOT. Swift followed 18 gravitational-wave candidate alerts, with UVOT observing a total of 424 deg^2. We found 27 sources that changed in magnitude at the 3 sigma level compared with archival u or g-band catalogued values. Swift/UVOT also followed up a further 13 sources reported by other facilities during the O3 period. Using catalogue information, we divided these 40 sources into five initial classifications: 11 candidate active galactic nuclei (AGN)/quasars, 3 Cataclysmic Variables (CVs), 9 supernovae, 11 unidentified sources that had archival photometry and 6 uncatalogued sources for which no archival photometry was available. We have no strong evidence to identify any of these transients as counterparts to the GW events. The 17 unclassified sources are likely a mix of AGN and a class of fast-evolving transient, and one source may be a CV., Comment: 25 pages, 6 figures and 5 tables. Submitted to MNRAS. Supplementary contains 23 pages with 8 figures and 1 table
Published: 2021
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3. Swift Multiwavelength Follow-up of LVC S200224ca and the Implications for Binary Black Hole Mergers

Author: Klingler, N. J., Lien, A., Oates, S. R., Kennea, J. A., Evans, P. A., Tohuvavohu, A., Zhang, B., Page, K. L., Cenko, S. B., Barthelmy, S. D., Beardmore, A. P., Bernardini, M. G., Breeveld, A. A., Brown, P. J., Burrows, D. N., Campana, S., Cusumano, G., D'Aì, A., D'Avanzo, P., D'Elia, V., de Pasquale, M., Emery, S. W. K., Garcia, J., Giommi, P., Gronwall, C., Hartmann, D. H., Krimm, H. A., Kuin, N. P. M., Malesani, D. B., Marshall, F. E., Melandri, A., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Palmer, D. M., Page, M. J., Perri, M., Racusin, J. L., Sakamoto, T., Sbarufatti, B., Schlieder, J. E., Siegel, M. H., Tagliaferri, G., and Troja, E.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: On 2020 February 24, during their third observing run ("O3"), the Laser Interferometer Gravitational-wave Observatory and Virgo Collaboration (LVC) detected S200224ca: a candidate gravitational wave (GW) event produced by a binary black hole (BBH) merger. This event was one of the best-localized compact binary coalescences detected in O3 (with 50%/90% error regions of 13/72 deg$^2$), and so the Neil Gehrels Swift Observatory performed rapid near-UV/X-ray follow-up observations. Swift-XRT and UVOT covered approximately 79.2% and 62.4% (respectively) of the GW error region, making S200224ca the BBH event most thoroughly followed-up in near-UV (u-band) and X-ray to date. No likely EM counterparts to the GW event were found by the Swift BAT, XRT, or UVOT, nor by other observatories. Here we report on the results of our searches for an EM counterpart, both in the BAT data near the time of the merger, and in follow-up UVOT/XRT observations. We also discuss the upper limits we can place on EM radiation from S200224ca, and the implications these limits have on the physics of BBH mergers. Namely, we place a shallow upper limit on the dimensionless BH charge, $\hat{q} < 1.4 \times10^{-4}$, and an upper limit on the isotropic-equivalent energy of a blast wave $E < 4.1\times10^{51}$ erg (assuming typical GRB parameters)., Comment: 14 pages, 6 figures, accepted for publication in ApJ
Published: 2020
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4. Space Telescope and Optical Reverberation Mapping Project. XII. Broad-Line Region Modeling of NGC 5548

Author: Williams, P. R., Pancoast, A., Treu, T., Brewer, B. J., Peterson, B. M., Barth, A. J., Malkan, M. A., De Rosa, G., Horne, Keith, Kriss, G. A., Arav, N., Bentz, M. C., Cackett, E. M., Bontà, E. Dalla, Dehghanian, M., Done, C., Ferland, G. J., Grier, C. J., Kaastra, J., Kara, E., Kochanek, C. S., Mathur, S., Mehdipour, M., Pogge, R. W., Proga, D., Vestergaard, M., Waters, T., Adams, S. M., Anderson, M. D., Arévalo, P., Beatty, T. G., Bennert, V. N., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Deason, A. J., De Lorenzo-Cáceres, A., Denney, K. D., Dietrich, M., Edelson, R., Efimova, N. V., Ely, J., Evans, P. A., Fausnaugh, M. M., Filippenko, A. V., Flatland, K., Fox, O. D., Gardner, E., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Greene, J. E., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaspi, S., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Knigge, C., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, Manne-Nicholas, E. R., MacInnis, F., Mauerhan, J. C., McGurk, R., Hardy, I. M. Mc, Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Müller-Sánchez, F., Nazarov, S. V., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Papadakis, I., Parks, J. R., Pei, L., Penny, M. T., Pizzella, A., Poleski, R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Tejos, N., Turner, C. S., Uttley, P., Van Saders, J., Vaughan, S. A., Vican, L., Villanueva Jr., S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We present geometric and dynamical modeling of the broad line region for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The dataset includes photometric and spectroscopic monitoring in the optical and ultraviolet, covering the H$\beta$, C IV, and Ly$\alpha$ broad emission lines. We find an extended disk-like H$\beta$ BLR with a mixture of near-circular and outflowing gas trajectories, while the C IV and Ly$\alpha$ BLRs are much less extended and resemble shell-like structures. There is clear radial structure in the BLR, with C IV and Ly$\alpha$ emission arising at smaller radii than the H$\beta$ emission. Using the three lines, we make three independent black hole mass measurements, all of which are consistent. Combining these results gives a joint inference of $\log_{10}(M_{\rm BH}/M_\odot) = 7.64^{+0.21}_{-0.18}$. We examine the effect of using the $V$ band instead of the UV continuum light curve on the results and find a size difference that is consistent with the measured UV-optical time lag, but the other structural and kinematic parameters remain unchanged, suggesting that the $V$ band is a suitable proxy for the ionizing continuum when exploring the BLR structure and kinematics. Finally, we compare the H$\beta$ results to similar models of data obtained in 2008 when the AGN was at a lower luminosity state. We find that the size of the emitting region increased during this time period, but the geometry and black hole mass remain unchanged, which confirms that the BLR kinematics suitably gauge the gravitational field of the central black hole., Comment: 26 pages, 19 figures, 1 table, accepted for publication in ApJ
Published: 2020
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5. Swift-XRT follow-up of gravitational wave triggers during the third aLIGO/Virgo observing run

Author: Page, K. L., Evans, P. A., Tohuvavohu, A., Kennea, J. A., Klingler, N. J., Cenko, S. B., Oates, S. R., Ambrosi, E., Barthelmy, S. D., Beardmore, A. P., Bernardini, M. G., Breeveld, A. A., Brown, P. J., Burrows, D. N., Campana, S., Caputo, R., Cusumano, G., D'Ai, A., D'Avanzo, P., D'Elia, V., De Pasquale, M., Emery, S. W. K., Giommi, P., Gronwall, C., Hartmann, D. H., Krimm, H. A., Kuin, N. P. M., Malesani, D. B., Marshall, F. E., Melandri, A., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Pagani, C., Page, M. J., Palmer, D. M., Perri, M., Racusin, J. L., Sakamoto, T., Sbarufatti, B., Schlieder, J. E., Siegel, M. H., Tagliaferri, G., and Troja, E.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Neil Gehrels Swift Observatory followed up 18 gravitational wave (GW) triggers from the LIGO/Virgo collaboration during the O3 observing run in 2019/2020, performing approximately 6500 pointings in total. Of these events, four were finally classified (if real) as binary black hole (BH) triggers, six as binary neutron star (NS) events, two each of NSBH and Mass Gap triggers, one an unmodelled (Burst) trigger, and the remaining three were subsequently retracted. Thus far, four of these O3 triggers have been formally confirmed as real gravitational wave events. While no likely electromagnetic counterparts to any of these GW events have been identified in the X-ray data (to an average upper limit of 3.60 x 10^{-12} erg cm^{-2} s^{-1} over 0.3-10 keV), or at other wavelengths, we present a summary of all the Swift-XRT observations performed during O3, together with typical upper limits for each trigger observed. The majority of X-ray sources detected during O3 were previously uncatalogued; while some of these will be new (transient) sources, others are simply too faint to have been detected by earlier survey missions such as ROSAT. The all-sky survey currently being performed by eROSITA will be a very useful comparison for future observing runs, reducing the number of apparent candidate X-ray counterparts by up to 95 per cent., Comment: 23 pages (including 4 pages of references, and a 4 page table in the appendix), 5 figures (4 in colour), accepted for publication in MNRAS. (Replaced due to annoying spelling typo in the abstract.)
Published: 2020
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6. Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548

Author: Horne, Keith, De Rosa, G., Peterson, B. M., Barth, A. J., Ely, J., Fausnaugh, M. M., Kriss, G. A., Pei, L., Adams, S. M., Anderson, M. D., Arevalo, P., Beatty, T G., Bennert, V. N., Bentz, M. C., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Bonta, E. Dalla, Deason, A. J., Dehghanian, M., De Lorenzo-Caceres, A., Denney, K. D., Dietrich, M., Done, C., Edelson, R., Efimova, N. V., Eracleous, M., Evans, P. A., Ferland, G. J., Filippenko, A. V., Flatland, K., Fox, O. D., Gardner, E., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Goad, M. R., Gonzalez, L., Gorjian, V., Greene, J. E., Grier, C. J., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Kochanek, C. S., Korista, K. T., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, MacInnis, F., Malkan, M. A., Manne-Nicholas, E. R., Mathur, S., Mauerhan, J. C., McGurk, R., Hardy, I. M. Mc, Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Mueller-Sanchez, F., Nazarov, S. V., Netzer, H., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Pancoast, A., Papadakis, I., Parks, J. R., Penny, M. T., Pizzella, A., Pogge, R. W., Poleski, R., Pott, J. -U., Proga, D., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnuelle, K., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Strauss, M. A., Sung, H. -I., Tayar, J., Teems, K. G., Tejos, N., Treu, T., Turner, C. S., Uttley, P., Van Saders, J ., Vestergaard, M., Vican, L., Villanueva Jr, S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zakamska, N. L., Zheng, W., Zhu, W., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We report velocity-delay maps for prominent broad emission lines, Ly_alpha, CIV, HeII and H_beta, in the spectrum of NGC5548. The emission-line responses inhabit the interior of a virial envelope. The velocity-delay maps reveal stratified ionization structure. The HeII response inside 5-10 light-days has a broad single-peaked velocity profile. The Ly_alpha, CIV, and H_beta responses peak inside 10 light-days, extend outside 20 light-days, and exhibit a velocity profile with two peaks separated by 5000 km/s in the 10 to 20 light-day delay range. The velocity-delay maps show that the M-shaped lag vs velocity structure found in previous cross-correlation analysis is the signature of a Keplerian disk with a well-defined outer edge at R=20 light-days. The outer wings of the M arise from the virial envelope, and the U-shaped interior of the M is the lower half of an ellipse in the velocity-delay plane. The far-side response is weaker than that from the near side, so that we see clearly the lower half, but only faintly the upper half, of the velocity--delay ellipse. The delay tau=(R/c)(1-sin(i))=5 light-days at line center is from the near edge of the inclined ring, giving the inclination i=45 deg. A black hole mass of M=7x10^7 Msun is consistent with the velocity-delay structure. A barber-pole pattern with stripes moving from red to blue across the CIV and possibly Ly_alpha line profiles suggests the presence of azimuthal structure rotating around the far side of the broad-line region and may be the signature of precession or orbital motion of structures in the inner disk. Further HST observations of NGC 5548 over a multi-year timespan but with a cadence of perhaps 10 days rather than 1 day could help to clarify the nature of this new AGN phenomenon., Comment: 19 pages, 9 figures, ApJ in press
Published: 2020
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7. Swift-XRT Follow-up of Gravitational Wave Triggers in the Second Advanced LIGO/Virgo Observing Run

Author: Klingler, N. J., Kennea, J. A., Evans, P. A., Tohuvavohu, A., Cenko, S. B., Barthelmy, S. D., Beardmore, A. P., Breeveld, A. A., Brown, P. J., Burrows, D. N., Campana, S., Cusumano, G., D'Aì, A., D'Avanzo, P., D'Elia, V., de Pasquale, M., Emery, S. W. K., Garcia, J., Giommi, P., Gronwall, C., Hartmann, D. H., Krimm, H. A., Kuin, N. P. M., Lien, A., Malesani, D. B., Marshall, F. E., Melandri, A., Nousek, J. A., Oates, S. R., O'Brien, P. T., Osborne, J. P., Page, K. L., Palmer, D. M., Perri, M., Racusin, J. L., Siegel, M. H., Sakamoto, T., Sbarufatti, B., Tagliaferri, G., and Troja, E.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Neil Gehrels Swift Observatory carried out prompt searches for gravitational wave (GW) events detected by the LIGO/Virgo Collaboration (LVC) during the second observing run ("O2"). Swift performed extensive tiling of eight LVC triggers, two of which had very low false-alarm rates (GW 170814 and the epochal GW 170817), indicating a high confidence of being astrophysical in origin; the latter was the first GW event to have an electromagnetic counterpart detected. In this paper we describe the follow-up performed during O2 and the results of our searches. No GW electromagnetic counterparts were detected; this result is expected, as GW 170817 remained the only astrophysical event containing at least one neutron star after LVC's later retraction of some events. A number of X-ray sources were detected, with the majority of identified sources being active galactic nuclei. We discuss the detection rate of transient X-ray sources and their implications in the O2 tiling searches. Finally, we describe the lessons learned during O2, and how these are being used to improve the \swift\ follow-up of GW events. In particular, we simulate a population of GRB afterglows to evaluate our source ranking system's ability to differentiate them from unrelated and uncatalogued X-ray sources. We find that $\approx$60-70% of afterglows whose jets are oriented towards Earth will be given high rank (i.e., "interesting" designation) by the completion of our second follow-up phase (assuming their location in the sky was observed), but that this fraction can be increased to nearly 100% by performing a third follow-up observation of sources exhibiting fading behavior., Comment: 18 pages, 4 figures, 2 tables, accepted for publication in ApJS
Published: 2019
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8. Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum

Author: Kriss, G. A., De Rosa, G., Ely, J., Peterson, B. M., Kaastra, J., Mehdipour, M., Ferland, G. J., Dehghanian, M., Mathur, S., Edelson, R., Korista, K. T., Arav, N., Barth, A. J., Bentz, M. C., Brandt, W. N., Crenshaw, D. M., Bontà, E. Dalla, Denney, K. D., Done, C., Eracleous, M., Fausnaugh, M. M., Gardner, E., Goad, M. R., Grier, C. J., Horne, Keith, Kochanek, C. S., Mchardy, I. M., Netzer, H., Pancoast, A., Pei, L., Pogge, R. W., Proga, D., Silva, C., Tejos, N., Vestergaard, M., Adams, S. M., Anderson, M. D., Arévalo, P., Beatty, T G., Behar, E., Bennert, V. N., Bianchi, S., Bigley, A., Bisogni, S., Boissay-Malaquin, R., Borman, G. A., Bottorff, M. C., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Cappi, M., Carini, M. T., Clubb, K. I., Comerford, J. M., Coker, C. T., Corsini, E. M., Costantini, E., Croft, S., Croxall, K. V., Deason, A. J., De Lorenzo-Cáceres, A., De Marco, B., Dietrich, M., Di Gesu, L., Ebrero, J., Evans, P. A., Filippenko, A. V., Flatland, K., Gates, E. L., Gehrels, N., Geier, Z S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T. A., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Kaspi, S., Kelly, B. C., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S. C., Kim, S. Y., King, A., Klimanov, S. A., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, Macinnis, F., Malkan, M. A., Manne-Nicholas, E. R., Matt, G., Mauerhan, J. C., Mcgurk, R., Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Müller-Sánchez, F., Nazarov, S. V., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Paltani, S., Parks, J. R., Pinto, C., Pizzella, A., Poleski, R., Ponti, G., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnülle, K., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Teems, K. G., Treu, T., Turner, C. S., Uttley, P., Van Saders, J ., Vican, L., Villforth, C., Villanueva Jr., S., Walton, D. J., Waters, T., Weiss, Y., Woo, J. -H., Yan, H., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We model the ultraviolet spectra of the Seyfert 1 galaxy NGC~5548 obtained with the Hubble Space Telescope during the 6-month reverberation-mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly$\alpha$ and C IV, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly$\alpha$ and C IV have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show delayed response to continuum variations corresponding to recombination in gas with a density of $\sim 10^5~\rm cm^{-3}$. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in $\sim\,2012$ corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state., Comment: 50 pages, 30 figures, uses aastex62.cls. Accepted for publication in ApJ, 07/06/2019. High-level products page in MAST will go live after 7/15/2019. Replaced Figure 4 on 7/12/2019 to be more red/green color-blind friendly
Published: 2019
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9. The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey

Author: Edelson, R., Gelbord, J., Cackett, E., Peterson, B. M., Horne, K., Barth, A. J., Starkey, D. A., Bentz, M., Brandt, W. N., Goad, M., Joner, M., Korista, K., Netzer, H., Page, K., Uttley, P., Vaughan, S., Breeveld, A., Cenko, S. B., Done, C., Evans, P., Fausnaugh, M., Ferland, G., Gonzalez-Buitrago, D., Gropp, J., Grupe, D., Kaastra, J., Kennea, J., Kriss, G., Mathur, S., Mehdipour, M., Mudd, D., Nousek, J., Schmidt, T., Vestergaard, M., and Villforth, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled $\sim$200-350 times in 0.3-10 keV X-ray and six UV/optical bands. Uniform reduction and cross-correlation analysis of these datasets yields three main results: 1) The X-ray/UV correlations are much weaker than those within the UV/optical, posing severe problems for the lamp-post reprocessing model in which variations in a central X-ray corona drive and power those in the surrounding accretion disk. 2) The UV/optical interband lags are generally consistent with $ \tau \propto \lambda^{4/3} $ as predicted by the centrally illuminated thin accretion disk model. While the average interband lags are somewhat larger than predicted, these results alone are not inconsistent with the thin disk model given the large systematic uncertainties involved. 3) The one exception is the U band lags, which are on average a factor of $\sim$2.2 larger than predicted from the surrounding band data and fits. This excess appears due to diffuse continuum emission from the broad-line region (BLR). The precise mixing of disk and BLR components cannot be determined from these data alone. The lags in different AGN appear to scale with mass or luminosity. We also find that there are systematic differences between the uncertainties derived by javelin vs. more standard lag measurement techniques, with javelin reporting smaller uncertainties by a factor of 2.5 on average. In order to be conservative only standard techniques were used in the analyses reported herein., Comment: 25 pages, 9 tables, 6 figures, published in ApJ. The paper has been revised to conform to the published version. Please note that the data (Table 2) are available at the Digital Repository at the University of Maryland, https://drum.lib.umd.edu/handle/1903/21536
Published: 2018
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10. The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey

Author: Edelson, R, Gelbord, J, Cackett, E, Peterson, BM, Horne, K, Barth, AJ, Starkey, DA, Bentz, M, Brandt, WN, Goad, M, Joner, M, Korista, K, Netzer, H, Page, K, Uttley, P, Vaughan, S, Breeveld, A, Cenko, SB, Done, C, Evans, P, Fausnaugh, M, Ferland, G, Gonzalez-Buitrago, D, Gropp, J, Grupe, D, Kaastra, J, Kennea, J, Kriss, G, Mathur, S, Mehdipour, M, Mudd, D, Nousek, J, Schmidt, T, Vestergaard, M, and Villforth, C
Subjects: galaxies: active, galaxies: nuclei, galaxies: Seyfert, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract: Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled ∼200-350 times in 0.3-10 keV X-ray and six UV/optical bands. Uniform reduction and cross-correlation analysis of these data sets yields three main results: (1) The X-ray/UV correlations are much weaker than those within the UV/optical, posing severe problems for the lamp-post reprocessing model in which variations in a central X-ray corona drive and power those in the surrounding accretion disk. (2) The UV/optical interband lags are generally consistent with as predicted by the centrally illuminated thin accretion disk model. While the average interband lags are somewhat larger than predicted, these results alone are not inconsistent with the thin disk model given the large systematic uncertainties involved. (3) The one exception is the U band lags, which are on average a factor of ∼2.2 larger than predicted from the surrounding band data and fits. This excess appears to be due to diffuse continuum emission from the broad-line region (BLR). The precise mixing of disk and BLR components cannot be determined from these data alone. The lags in different AGN appear to scale with mass or luminosity. We also find that there are systematic differences between the uncertainties derived by JAVELIN versus more standard lag measurement techniques, with JAVELIN reporting smaller uncertainties by a factor of 2.5 on average. In order to be conservative only standard techniques were used in the analyses reported herein.
Published: 2019

11. Swift and NuSTAR observations of GW170817: detection of a blue kilonova

Author: Evans, P. A., Cenko, S. B., Kennea, J. A., Emery, S. W. K., Kuin, N. P. M., Korobkin, O., Wollaeger, R. T., Fryer, C. L., Madsen, K. K., Harrison, F. A., Xu, Y., Nakar, E., Hotokezaka, K., Lien, A., Campana, S., Oates, S. R., Troja, E., Breeveld, A. A., Marshall, F. E., Barthelmy, S. D., Beardmore, A. P., Burrows, D. N., Cusumano, G., D'Ai, A., D'Avanzo, P., D'Elia, V., de Pasquale, M., Even, W. P., Fontes, C. J., Forster, K., Garcia, J., Giommi, P., Grefenstette, B., Gronwall, C., Hartmann, D. H., Heida, M., Hungerford, A. L., Kasliwal, M. M., Krimm, H. A., Levan, A. J., Malesani, D., Melandri, A., Miyasaka, H., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Pagani, C., Page, K. L., Palmer, D. M., Perri, M., Pike, S., Racusin, J. L., Rosswog, S., Siegel, M. H., Sakamoto, T., Sbarufatti, B., Tagliaferri, G., Tanvir, N. R., and Tohuvavohu, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: With the first direct detection of merging black holes in 2015, the era of gravitational wave (GW) astrophysics began. A complete picture of compact object mergers, however, requires the detection of an electromagnetic (EM) counterpart. We report ultraviolet (UV) and X-ray observations by Swift and the Nuclear Spectroscopic Telescope ARray (NuSTAR) of the EM counterpart of the binary neutron star merger GW170817. The bright, rapidly fading ultraviolet emission indicates a high mass ($\approx0.03$ solar masses) wind-driven outflow with moderate electron fraction ($Y_{e}\approx0.27$). Combined with the X-ray limits, we favor an observer viewing angle of $\approx 30^{\circ}$ away from the orbital rotation axis, which avoids both obscuration from the heaviest elements in the orbital plane and a direct view of any ultra-relativistic, highly collimated ejecta (a gamma-ray burst afterglow)., Comment: Science, in press; 56 pages, 12 figures
Published: 2017
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12. Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the UV anomaly in NGC 5548 with X-Ray Spectroscopy

Author: Mathur, S., Gupta, A., Page, K., Pogge, R. W., Krongold, Y., Goad, M. R., Adams, S. M., Anderson, M. D., Arevalo, P., Barth, A. J., Bazhaw, C., Beatty, T. G., Bentz, M. C., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Coker, C. T., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Bonta, E. Dalla, Deason, A. J., Denney, K. D., De Lorenzo-Caceres, A., De Rosa, G., Dietrich, M., Edelson, R., Ely, J., Eracleous, M., Evans, P. A., Fausnaugh, M. M., Ferland, G. J., Filippenko, A. V., Flatland, K., Fox, O. D., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Gorjian, V., Greene, J. E., Grier, C. J., Grupe, D., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Horenstein, D., Horne, Keith, Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, B. C., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Kochanek, C. S., Korista, K. T., Kriss, G. A., Lau, M. W., Lee, J. C., Leonard, D. C., Li, M., Lira, P., Ma, Z., MacInnis, F., Manne-Nicholas, E. R., Malkan, M. A., Mauerhan, J. C., McGurk, R., McHardy, I. M., Montouri, C., Morelli, L., Mosquera, A., Mudd, D., Muller-Sanchez, F., Musso, R., Nazarov, S. V., Netzer, H., Nguyen, M. L., Norris, R. P., Nousek, J. A., Ochner, P., Okhmat, D. N., Ou-Yang, B., Pancoast, A., Papadakis, I., Parks, J. R., Pei, L., Peterson, B. M., Pizzella, A., Poleski, R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnülle, K., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Tejos, N., Turner, C. S., Uttley, P., Van Saders, J., Vestergaard, M., Vican, L., VillanuevaJr., S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: During the Space Telescope and Optical Reverberation Mapping Project (STORM) observations of NGC 5548, the continuum and emission-line variability became de-correlated during the second half of the 6-month long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as a part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than being due to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all the three observations: the UV emission line flux decrease, the soft-excess increase, and the emission line anomaly., Comment: ApJ in press. Replaced with the accepted version
Published: 2017
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13. Swift monitoring of NGC 4151: Evidence for a Second X-ray/UV Reprocessing

Author: Edelson, R., Gelbord, J., Cackett, E., Connolly, S., Done, C., Fausnaugh, M., Gardner, E., Gehrels, N., Goad, M., Horne, K., McHardy, I., Peterson, B. M., Vaughan, S., Vestergaard, M., Breeveld, A., Barth, A. J., Bentz, M., Bottorff, M., Brandt, W. N., Crawford, S. M., Bonta, E. Dalla, Emmanoulopoulos, D., Evans, P., Jaimes, R. Figuera, Filippenko, A. V., Ferland, G., Grupe, D., Joner, M., Kennea, J., Korista, K. T., Krimm, H. A., Kriss, G., Leonard, D. C., Mathur, S., Netzer, H., Nousek, J., Page, K., Romero-Colmenero, E., Siegel, M., Starkey, D. A., Treu, T., Vogler, H. A., Winkler, H., and Zheng, W.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Swift monitoring of NGC 4151 with ~6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50 keV) and six in the ultraviolet (UV)/optical (1900-5500 A). The three hardest X-ray bands (>2.5 keV) are all strongly correlated with no measurable interband lag while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ~3-4 days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by ~0.5-1 day. This combination of >~3 day lags between the X-rays and UV and <~1 day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component which illuminates the disk and drives its variability., Comment: 14 pages, 6 figures, 7 tables. To appear in ApJ April 2017 issue. This version incorporates minor revisions to conform to published version and corrects the links to the author names above
Published: 2017
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14. Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548

Author: Pei, L., Fausnaugh, M. M., Barth, A. J., Peterson, B. M., Bentz, M. C., De Rosa, G., Denney, K. D., Goad, M. R., Kochanek, C. S., Korista, K. T., Kriss, G. A., Pogge, R. W., Bennert, V. N., Brotherton, M., Clubb, K. I., Bontà, E. Dalla, Filippenko, A. V., Greene, J. E., Grier, C. J., Vestergaard, M., Zheng, W., Adams, Scott M., Beatty, Thomas G., Bigley, A., Brown, Jacob E., Brown, Jonathan S., Canalizo, G., Comerford, J. M., Coker, Carl T., Corsini, E. M., Croft, S., Croxall, K. V., Deason, A. J., Eracleous, Michael, Fox, O. D., Gates, E. L., Henderson, C. B., Holmbeck, E., Holoien, T. W. -S., Jensen, J. J., Johnson, C. A., Kelly, P. L., Kim, S., King, A., Lau, M. W., Li, Miao, Lochhaas, Cassandra, Ma, Zhiyuan, Manne-Nicholas, E. R., Mauerhan, J. C., Malkan, M. A., McGurk, R., Morelli, L., Mosquera, Ana, Mudd, Dale, Sanchez, F. Muller, Nguyen, M. L., Ochner, P., Ou-Yang, B., Pancoast, A., Penny, Matthew T., Pizzella, A., Poleski, Radosław, Runnoe, Jessie, Scott, B., Schimoia, Jaderson S., Shappee, B. J., Shivvers, I., Simonian, Gregory V., Siviero, A., Somers, Garrett, Stevens, Daniel J., Strauss, M. A., Tayar, Jamie, Tejos, N., Treu, T., Van Saders, J., Vican, L., Villanueva Jr., S., Yuk, H., Zakamska, N. L., Zhu, W., Anderson, M. D., Arévalo, P., Bazhaw, C., Bisogni, S., Borman, G. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Cackett, E. M., Carini, M. T., Crenshaw, D. M., De Lorenzo-Cáceres, A., Dietrich, M., Edelson, R., Efimova, N. V., Ely, J., Evans, P. A., Ferland, G. J., Flatland, K., Gehrels, N., Geier, S., Gelbord, J. M., Grupe, D., Gupta, A., Hall, P. B., Hicks, S., Horenstein, D., Horne, Keith, Hutchison, T., Im, M., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, B. C., Kennea, J. A., Kim, M., Kim, S. C., Klimanov, S. A., Lee, J. C., Leonard, D. C., Lira, P., MacInnis, F., Mathur, S., McHardy, I. M., Montouri, C., Musso, R., Nazarov, S. V., Netzer, H., Norris, R. P., Nousek, J. A., Okhmat, D. N., Papadakis, I., Parks, J. R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Saylor, D. A., Schnülle, K., Sergeev, S. G., Siegel, M., Skielboe, A., Spencer, M., Starkey, D., Sung, H. -I., Teems, K. G., Turner, C. S., Uttley, P., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multi-wavelength reverberation mapping campaign. The campaign spanned six months and achieved an almost daily cadence with observations from five ground-based telescopes. The H$\beta$ and He II $\lambda$4686 broad emission-line light curves lag that of the 5100 $\AA$ optical continuum by $4.17^{+0.36}_{-0.36}$ days and $0.79^{+0.35}_{-0.34}$ days, respectively. The H$\beta$ lag relative to the 1158 $\AA$ ultraviolet continuum light curve measured by the Hubble Space Telescope is roughly $\sim$50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is $\sim$50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for H$\beta$ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the H$\beta$ and He II $\lambda$4686 emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C IV, Ly $\alpha$, He II(+O III]), and Si IV(+O IV]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured H$\beta$ lag is a factor of five shorter than the expected value implied by the $R_\mathrm{BLR} - L_\mathrm{AGN}$ relation based on the past behavior of NGC 5548., Comment: 22 pages, 13 figures, accepted to ApJ
Published: 2017
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15. Space Telescope and Optical Reverberation Mapping Project VI: reverberating Disk Models for NGC 5548

Author: Starkey, D., Horne, Keith, Fausnaugh, M. M., Peterson, B. M., Bentz, M. C., Kochanek, C. S., Denney, K. D., Edelson, R., Goad, M. R., De Rosa, G., Anderson, M. D., Arevalo, P., Barth, A. J., Bazhaw, C., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Cackett, E. M., Carini, M. T., Croxall, K. V., Crenshaw, D. M., Bonta, E. Dalla, De Lorenzo-Caceres, A., Dietrich, M., Efimova, N. V., Ely, J., Evans, P. A., Filippenko, A. V., Flatland, K., Gehrels, N., Geier, S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Grier, C. J., Grupe, D., Hall, P. B., Hicks, S., Horenstein, D., Hutchison, T., Im, M., Jensen, J. J., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, B. C., Kennea, J. A., Kim, S. C., Kim, M., Klimanov, S. A., Korista, K. T., Kriss, G. A., Lee, J. C., Leonard, D. C., Lira, P., MacInnis, F., Manne-Nicholas, E. R., Mathur, S., McHardy, I. M., Montouri, C., Musso, R., Nazarov, S. V., Norris, R. P., Nousek, J. A., Okhmat, D. N., Pancoast, A., Parks, J. R., Pei, L., Pogge, R. W., Pott, J. -U., Rafter, S. E., Rix, H. W., Saylor, D. A., Schimoia, J. S., Schnulle, K., Sergeev, S. G., Siegel, M. H., Spencer, M., Sung, H. -I., Teems, K. G., Turner, C. S., Uttley, P., Vestergaard, M., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Zheng, W., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves (1158 to 9157 angstroms) combine simultaneous HST , Swift , and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination, i, temperature T1 at 1 light day from the black hole, and a temperature-radius slope, alpha. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at L/LEdd = 0.1, Comment: V2: Oops wrong title! V1: Accepted for publication in ApJ, 20 Pages, 11 Figures
Published: 2016
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16. Evidence for the magnetar nature of 1E 161348-5055 in RCW 103

Author: D'Aì, A., Evans, P. A., Burrows, D. N., Kuin, N. P. M., Kann, D. A., Campana, S., Maselli, A., Romano, P., Cusumano, G., La Parola, V., Barthelmy, S. D., Beardmore, A. P., Cenko, S. B., De Pasquale, M., Gehrels, N., Greiner, J., Kennea, J. A., Klose, S., Melandri, A., Nousek, J. A., Osborne, J. P., Palmer, D. M., Sbarufatti, B., Schady, P., Siegel, M. H., Tagliaferri, G., Yates, R., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the detection of a bright, short, structured X-ray burst coming from the supernova remnant RCW 103 on 2016 June 22 caught by the Swift/BAT monitor, and on the follow-up campaign made with Swift/XRT, Swift/UVOT and the optical/NIR GROND detector. The characteristics of this flash, such as duration, and spectral shape, are consistent with typical short bursts observed from soft gamma repeaters. The BAT error circle at 68 per cent confidence range encloses the point-like X-ray source at the centre of the nebula, 1E161348-5055. Its nature has been long debated due to a periodicity of 6.67 hr in X-rays, which could indicate either an extremely slow pulsating neutron star, or the orbital period of a very compact X-ray binary system. We found that 20 min before the BAT trigger, the soft X-ray emission of 1E161348-5055 was a factor of ~100 higher than measured 2 yr earlier, indicating that an outburst had already started. By comparing the spectral and timing characteristics of the source in the two years before the outburst and after the BAT event, we find that, besides a change in luminosity and spectral shape, also the 6.67 hr pulsed profile has significantly changed with a clear phase shift with respect to its low-flux profile. The UV/optical/NIR observations did not reveal any counterpart at the position of 1E161348-5055. Based on these findings, we associate the BAT burst with 1E161348-5055, we classify it as a magnetar, and pinpoint the 6.67 hr periodicity as the magnetar spin period., Comment: 12 pages, accepted for publication in MNRAS on 2016 August 08
Published: 2016
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17. Supplement: Localization and broadband follow-up of the gravitational-wave transient GW150914

Author: Abbott, B. P., Abbott, R., Abbott, T. D., Abernathy, M. R., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allocca, A., Altin, P. A., Anderson, S. B., Anderson, W. G., Arai, K., Araya, M. C., Arceneaux, C. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Babak, S., Bacon, P., Bader, M. K. M., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Barthelmy, S., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bavigadda, V., Bazzan, M., Behnke, B., Bejger, M., Bell, A. S., Bell, C. J., Berger, B. K., Bergman, J., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Birch, J., Birney, R., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bodiya, T. P., Boer, M., Bogaert, G., Bogan, C., Bohe, A., Bojtos, P., Bond, C., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cadonati, L., Cagnoli, G., Cahillane, C., Bustillo, J. C., Callister, T., Calloni, E., Camp, J. B., Cannon, K. C., Cao, J., Capano, C. D., Capocasa, E., Carbognani, F., Caride, S., Diaz, J. C., Casentini, C., Caudill, S., Cavaglià, M., Cavalier, F., Cavalieri, R., Cella, G., Cepeda, C. B., Baiardi, L. C., Cerretani, G., Cesarini, E., Chakraborty, R., Chalermsongsak, T., Chamberlin, S. J., Chan, M., Chao, S., Charlton, P., Chassande-Mottin, E., Chen, H. Y., Chen, Y., Cheng, C., Chincarini, A., Chiummo, A., Cho, H. S., Cho, M., Chow, J. H., Christensen, N., Chu, Q., Chua, S., Chung, S., Ciani, G., Clara, F., Clark, J. A., Cleva, F., Coccia, E., Cohadon, P. -F., Colla, A., Collette, C. G., Cominsky, L., Constancio Jr., M., Conte, A., Conti, L., Cook, D., Corbitt, T. R., Cornish, N., Corsi, A., Cortese, S., Costa, C. A., Coughlin, M. W., Coughlin, S. B., Coulon, J. -P., Countryman, S. T., Couvares, P., Cowan, E. E., Coward, D. M., Cowart, M. J., Coyne, D. C., Coyne, R., Craig, K., Creighton, J. D. E., Cripe, J., Crowder, S. G., Cumming, A., Cunningham, L., Cuoco, E., Canton, T. Dal, Danilishin, S. L., D'Antonio, S., Danzmann, K., Darman, N. 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J., Lipunov, V., Gorbovskoy, E., Tyurina, N., Kornilov, V., Balanutsa, P., Kuznetsov, A., Buckley, D., Rebolo, R., Serra-Ricart, M., Israelian, G., Budnev, N. M., Gress, O., Ivanov, K., Poleshuk, V., Tlatov, A., Yurkov, V., Kawai, N., Serino, M., Negoro, H., Nakahira, S., Mihara, T., Tomida, H., Ueno, S., Tsunemi, H., Matsuoka, M., Croft, S., Feng, L., Franzen, T. M. O., Gaensler, B. M., Johnston-Hollitt, M., Kaplan, D. L., Morales, M. F., Tingay, S. J., Wayth, R. B., Williams, A., Smartt, S. J., Chambers, K. C., Smith, K. W., Huber, M. E., Young, D. R., Wright, D. E., Schultz, A., Denneau, L., Flewelling, H., Magnier, E. A., Primak, N., Rest, A., Sherstyuk, A., Stalder, B., Stubbs, C. W., Tonry, J., Waters, C., Willman, M., E., F. Olivares, Campbell, H., Kotak, R., Sollerman, J., Smith, M., Dennefeld, M., Anderson, J. P., Botticella, M. T., Chen, T. -W., Valle, M. D., Elias-Rosa, N., Fraser, M., Inserra, C., Kankare, E., Kupfer, T., Harmanen, J., Galbany, L., Guillou, L. Le, Lyman, J. D., Maguire, K., Mitra, A., Nicholl, M., Razza, A., Terreran, G., Valenti, S., Gal-Yam, A., Ćwiek, A., Ćwiok, M., Mankiewicz, L., Opiela, R., Zaremba, M., Żarnecki, A. F., Onken, C. A., Scalzo, R. A., Schmidt, B. P., Wolf, C., Yuan, F., Evans, P. A., Kennea, J. A., Burrows, D. N., Campana, S., Cenko, S. B., Marshall, F. E., Nousek, J., O'Brien, P., Osborne, J. P., Palmer, D., Perri, M., Siegel, M., Tagliaferri, G., Klotz, A., Turpin, D., Laugier, R., Beroiz, M., Peñuela, T., Macri, L. M., Oelkers, R. J., Lambas, D. G., Vrech, R., Cabral, J., Colazo, C., Dominguez, M., Sanchez, B., Gurovich, S., Lares, M., Marshall, J. L., DePoy, D. L., Padilla, N., Pereyra, N. A., Benacquista, M., Tanvir, N. R., Wiersema, K., Levan, A. J., Steeghs, D., Hjorth, J., Fynbo, J. P. U., Malesani, D., Milvang-Jensen, B., Watson, D., Irwin, M., Fernandez, C. G., McMahon, R. G., Banerji, M., Gonzalez-Solares, E., Schulze, S., Postigo, A. de U., Thoene, C. C., Cano, Z., and Rosswog, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: This Supplement provides supporting material for arXiv:1602.08492 . We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands., Comment: For the main Letter, see arXiv:1602.08492
Published: 2016
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18. Space Telescope and Optical Reverberation Mapping Project. IV. Anomalous behavior of the broad ultraviolet emission lines in NGC 5548

Author: Goad, M. R., Korista, K. T., De Rosa, G., Kriss, G. A., Edelson, R., Barth, A. J., Ferland, G. J., Kochanek, C. S., Netzer, H., Peterson, B. M., Bentz, M. C., Bisogni, S., Crenshaw, D. M., Denney, K. D., Ely, J., Fausnaugh, M. M., Grier, C. J., Gupta, A., Horne, K. D., Kaastra, J., Pancoast, A., Pei, L., Pogge, R. W., Skielboe, A., Starkey, D., Vestergaard, M., Zu, Y., Anderson, M. D., Arevalo, P., Bazhaw, C., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brewer, B. J., Cackett, E. M., Carini, M. T., Croxall, K. V., Bonta, E. Dalla, de Lorenzo-Caceres, A., Dietrich, M., Efimova, N. V., Evans, P. A., Filippenko, A. V., Flatland, K., Gehrels, N., Geier, S., Gelbord, G. M., Gonzalez, L., Gorjian, V., Grupe, D., Hall, P. B., Hicks, S., Horenstein, D., Hutchison, T., Im, M., Jensen, J. J., Joner, M. D., Jones, J., Kaspi, S., Kelly, B. C., Kennea, J. A., Kim, M., Kim, S. C., Klimanov, S. A., Larionov, V. M., Lee, J. C., Leonard, D. C., Lira, P., MacInnis, F., Manne-Nicholas, E. R., Mathur, S., McHardy, I. M., Montouri, C., Musso, R., Nazarov, S. V., Norris, R. P., Nousek, J. A., Okhmat, D. N., Papadakis, I., Parks, J. R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Saylor, D. A., Schimoia, J. S., Schnulle, K., Sergeev, S. G., Siegel, M., Spencer, M., Sung, H. -I., Teems, K. G., Treu, T., Turner, C. S., Uttley, P., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., and Zheng, W. -K.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: During an intensive Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) UV monitoring campaign of the Seyfert~1 galaxy NGC 5548 performed from 2014 February to July, the normally highly correlated far-UV continuum and broad emission-line variations decorrelated for ~60 to 70 days, starting ~75 days after the first HST/COS observation. Following this anomalous state, the flux and variability of the broad emission lines returned to a more normal state. This transient behavior, characterised by significant deficits in flux and equivalent width of the strong broad UV emission lines, is the first of its kind to be unambiguously identified in an active galactic nucleus reverberation mapping campaign. The largest corresponding emission-line flux deficits occurred for the high-ionization collisionally excited lines, C IV and Si IV(+O IV]), and also He II(+O III]), while the anomaly in Ly-alpha was substantially smaller. This pattern of behavior indicates a depletion in the flux of photons with E_{\rm ph} > 54 eV, relative to those near 13.6 eV. We suggest two plausible mechanisms for the observed behavior: (i) temporary obscuration of the ionizing continuum incident upon BLR clouds by a moving veil of material lying between the inner accretion disk and inner BLR, perhaps resulting from an episodic ejection of material from the disk, or (ii) a temporary change in the intrinsic ionizing continuum spectral energy distribution resulting in a deficit of ionizing photons with energies > 54 eV, possibly due to a transient restructuring of the Comptonizing atmosphere above the disk. Current evidence appears to favor the latter explanation., Comment: 12 pages, 2 figures, accepted for publication in ApJ, Friday 25th March 2016. A movie of the anomalous emission-line behavior can be found in the ancilliary documents
Published: 2016
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19. Localization and broadband follow-up of the gravitational-wave transient GW150914

Author: Abbott, B. P., Abbott, R., Abbott, T. D., Abernathy, M. R., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allocca, A., Altin, P. A., Anderson, S. B., Anderson, W. G., Arai, K., Araya, M. C., Arceneaux, C. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Babak, S., Bacon, P., Bader, M. K. M., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Barthelmy, S., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bavigadda, V., Bazzan, M., Behnke, B., Bejger, M., Bell, A. S., Bell, C. J., Berger, B. K., Bergman, J., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Birch, J., Birney, R., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bodiya, T. P., Boer, M., Bogaert, G., Bogan, C., Bohe, A., Bojtos, P., Bond, C., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cadonati, L., Cagnoli, G., Cahillane, C., Bustillo, J. C., Callister, T., Calloni, E., Camp, J. B., Cannon, K. C., Cao, J., Capano, C. D., Capocasa, E., Carbognani, F., Caride, S., Diaz, J. C., Casentini, C., Caudill, S., Cavaglià, M., Cavalier, F., Cavalieri, R., Cella, G., Cepeda, C. B., Baiardi, L. C., Cerretani, G., Cesarini, E., Chakraborty, R., Chalermsongsak, T., Chamberlin, S. J., Chan, M., Chao, S., Charlton, P., Chassande-Mottin, E., Chen, H. Y., Chen, Y., Cheng, C., Chincarini, A., Chiummo, A., Cho, H. S., Cho, M., Chow, J. H., Christensen, N., Chu, Q., Chua, S., Chung, S., Ciani, G., Clara, F., Clark, J. A., Cleva, F., Coccia, E., Cohadon, P. -F., Colla, A., Collette, C. G., Cominsky, L., Constancio Jr., M., Conte, A., Conti, L., Cook, D., Corbitt, T. R., Cornish, N., Corsi, A., Cortese, S., Costa, C. A., Coughlin, M. W., Coughlin, S. B., Coulon, J. -P., Countryman, S. T., Couvares, P., Cowan, E. E., Coward, D. M., Cowart, M. J., Coyne, D. C., Coyne, R., Craig, K., Creighton, J. D. E., Cripe, J., Crowder, S. G., Cumming, A., Cunningham, L., Cuoco, E., Canton, T. Dal, Danilishin, S. L., D'Antonio, S., Danzmann, K., Darman, N. S., Dattilo, V., Dave, I., Daveloza, H. P., Davier, M., Davies, G. S., Daw, E. J., Day, R., DeBra, D., Debreczeni, G., Degallaix, J., De Laurentis, M., Deléglise, S., Del Pozzo, W., Denker, T., Dent, T., Dereli, H., Dergachev, V., DeRosa, R. T., De Rosa, R., DeSalvo, R., Dhurandhar, S., Díaz, M. C., Di Fiore, L., Di Giovanni, M., Di Lieto, A., Di Pace, S., Di Palma, I., Di Virgilio, A., Dojcinoski, G., Dolique, V., Donovan, F., Dooley, K. L., Doravari, S., Douglas, R., Downes, T. P., Drago, M., Drever, R. W. P., Driggers, J. C., Du, Z., Ducrot, M., Dwyer, S. E., Edo, T. B., Edwards, M. C., Effler, A., Eggenstein, H. -B., Ehrens, P., Eichholz, J., Eikenberry, S. S., Engels, W., Essick, R. C., Etzel, T., Evans, M., Evans, T. M., Everett, R., Factourovich, M., Fafone, V., Fair, H., Fairhurst, S., Fan, X., Fang, Q., Farinon, S., Farr, B., Farr, W. M., Favata, M., Fays, M., Fehrmann, H., Fejer, M. M., Ferrante, I., Ferreira, E. 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S., Radkins, H., Raffai, P., Raja, S., Rakhmanov, M., Rapagnani, P., Raymond, V., Razzano, M., Re, V., Read, J., Reed, C. M., Regimbau, T., Rei, L., Reid, S., Reitze, D. H., Rew, H., Reyes, S. D., Ricci, F., Riles, K., Robertson, N. A., Robie, R., Robinet, F., Rocchi, A., Rolland, L., Rollins, J. G., Roma, V. J., Romano, R., Romanov, G., Romie, J. H., Rosińska, D., Rowan, S., Rüdiger, A., Ruggi, P., Ryan, K., Sachdev, S., Sadecki, T., Sadeghian, L., Salconi, L., Saleem, M., Salemi, F., Samajdar, A., Sammut, L., Sanchez, E. J., Sandberg, V., Sandeen, B., Sanders, J. R., Sassolas, B., Sathyaprakash, B. S., Saulson, P. R., Sauter, O., Savage, R. L., Sawadsky, A., Schale, P., Schilling, R., Schmidt, J., Schmidt, P., Schnabel, R., Schofield, R. M. S., Schönbeck, A., Schreiber, E., Schuette, D., Schutz, B. F., Scott, J., Scott, S. M., Sellers, D., Sentenac, D., Sequino, V., Sergeev, A., Serna, G., Setyawati, Y., Sevigny, A., Shaddock, D. A., Shah, S., Shahriar, M. S., Shaltev, M., Shao, Z., Shapiro, B., Shawhan, P., Sheperd, A., Shoemaker, D. H., Shoemaker, D. M., Siellez, K., Siemens, X., Sigg, D., Silva, A. D., Simakov, D., Singer, A., Singh, A., Singh, R., Singhal, A., Sintes, A. M., Slagmolen, B. J. J., Smith, J. R., Smith, N. D., Smith, R. J. E., Son, E. J., Sorazu, B., Sorrentino, F., Souradeep, T., Srivastava, A. K., Staley, A., Steinke, M., Steinlechner, J., Steinlechner, S., Steinmeyer, D., Stephens, B. C., Stone, R., Strain, K. A., Straniero, N., Stratta, G., Strauss, N. A., Strigin, S., Sturani, R., Stuver, A. L., Summerscales, T. Z., Sun, L., Sutton, P. J., Swinkels, B. L., Szczepańczyk, M. J., Tacca, M., Talukder, D., Tanner, D. B., Tápai, M., Tarabrin, S. P., Taracchini, A., Taylor, R., Theeg, T., Thirugnanasambandam, M. P., Thomas, E. G., Thomas, M., Thomas, P., Thorne, K. A., Thorne, K. S., Thrane, E., Tiwari, S., Tiwari, V., Tokmakov, K. V., Tomlinson, C., Tonelli, M., Torres, C. V., Torrie, C. I., Töyrä, D., Travasso, F., Traylor, G., Trifirò, D., Tringali, M. C., Trozzo, L., Tse, M., Turconi, M., Tuyenbayev, D., Ugolini, D., Unnikrishnan, C. S., Urban, A. L., Usman, S. A., Vahlbruch, H., Vajente, G., Valdes, G., van Bakel, N., van Beuzekom, M., Brand, J. F. J. van den, Broeck, C. Van Den, Vander-Hyde, D. C., van der Schaaf, L., van Heijningen, J. V., van Veggel, A. A., Vardaro, M., Vass, S., Vasúth, M., Vaulin, R., Vecchio, A., Vedovato, G., Veitch, J., Veitch, P. J., Venkateswara, K., Verkindt, D., Vetrano, F., Viceré, A., Vinciguerra, S., Vine, D. J., Vinet, J. -Y., Vitale, S., Vo, T., Vocca, H., Vorvick, C., Voss, D., Vousden, W. D., Vyatchanin, S. P., Wade, A. R., Wade, L. E., Wade, M., Walker, M., Wallace, L., Walsh, S., Wang, G., Wang, H., Wang, M., Wang, X., Wang, Y., Ward, R. L., Warner, J., Was, M., Weaver, B., Wei, L. -W., Weinert, M., Weinstein, A. J., Weiss, R., Welborn, T., Wen, L., Weßels, P., Westphal, T., Wette, K., Whelan, J. T., White, D. J., Whiting, B. 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D., Páta, P., Vitek, S., Adame, J. A., Konig, S., Rendón, F., Sanguino, T. de J. Mateo, Fernández-Muñoz, R., Yock, P. C., Rattenbury, N., Allen, W. H., Querel, R., Jeong, S., Park, I. H., Bai, J., Cui, Ch., Fan, Y., Wang, Ch., Hiriart, D., Lee, W. H., Claret, A., Sánchez-Ramírez, R., Pandey, S. B., Mediavilla, T., Sabau-Graziati, L., Abbott, T. M. C., Abdalla, F. B., Allam, S., Annis, J., Armstrong, R., Benoit-Lévy, A., Berger, E., Bernstein, R. A., Bertin, E., Brout, D., Buckley-Geer, E., Burke, D. L., Capozzi, D., Carretero, J., Castander, F. J., Chornock, R., Cowperthwaite, P. S., Crocce, M., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Desai, S., Diehl, H. T., Dietrich, J. P., Doctor, Z., Drlica-Wagner, A., Drout, M. R., Eifler, T. F., Estrada, J., Evrard, A. E., Fernandez, E., Finley, D. A., Flaugher, B., Foley, R. J., Fong, W. -F., Fosalba, P., Fox, D. B., Frieman, J., Fryer, C. L., Gaztanaga, E., Gerdes, D. W., Goldstein, D. A., Gruen, D., Gruendl, R. A., Gutierrez, G., Herner, K., Honscheid, K., James, D. J., Johnson, M. D., Johnson, M. W. G., Karliner, I., Kasen, D., Kent, S., Kessler, R., Kim, A. G., Kind, M. C., Kuehn, K., Kuropatkin, N., Lahav, O., Li, T. S., Lima, M., Lin, H., Maia, M. A. G., Margutti, R., Marriner, J., Martini, P., Matheson, T., Melchior, P., Metzger, B. D., Miller, C. J., Miquel, R., Neilsen, E., Nichol, R. C., Nord, B., Nugent, P., Ogando, R., Petravick, D., Plazas, A. A., Quataert, E., Roe, N., Romer, A. K., Roodman, A., Rosell, A. C., Rykoff, E. S., Sako, M., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Scolnic, D., Sevilla-Noarbe, I., Sheldon, E., Smith, N., Smith, R. C., Soares-Santos, M., Sobreira, F., Stebbins, A., Suchyta, E., Swanson, M. E. C., Tarle, G., Thaler, J., Thomas, D., Thomas, R. C., Tucker, D. L., Vikram, V., Walker, A. R., Wechsler, R. H., Wester, W., Yanny, B., Zuntz, J., Connaughton, V., Burns, E., Goldstein, A., Briggs, M. S., Zhang, B. -B., Hui, C. M., Jenke, P., Wilson-Hodge, C. A., Bhat, P. N., Bissaldi, E., Cleveland, W., Fitzpatrick, G., Giles, M. M., Gibby, M. H., Greiner, J., von Kienlin, A., Kippen, R. M., McBreen, S., Mailyan, B., Meegan, C. A., Paciesas, W. S., Preece, R. D., Roberts, O., Sparke, L., Stanbro, M., Toelge, K., Veres, P., Yu, H. -F., Blackburn, L., Ackermann, M., Ajello, M., Albert, A., Anderson, B., Atwood, W. B., Axelsson, M., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bruel, P., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Charles, E., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Cohen-Tanugi, J., Cominsky, L. R., Costanza, F., Cuoco, A., D'Ammando, F., de Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Domínguez, A., Drell, P. S., Dubois, R., Favuzzi, C., Ferrara, E. C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Gomez-Vargas, G. A., Green, D., Grenier, I. A., Grove, J. E., Guiriec, S., Hadasch, D., Harding, A. K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Jogler, T., Jóhannesson, G., Johnson, A. S., Kensei, S., Kocevski, D., Kuss, M., La Mura, G., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J., Maldera, S., Manfreda, A., Marelli, M., Mayer, M., Mazziotta, M. N., McEnery, J. E., Meyer, M., Michelson, P. F., Mirabal, N., Mizuno, T., Moiseev, A. A., Monzani, M. E., Moretti, E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Racusin, J. L., Rainò, S., Rando, R., Razzaque, S., Reimer, A., Reimer, O., Salvetti, D., Parkinson, P. M. Saz, Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Torres, D. F., Troja, E., Uchiyama, Y., Venters, T. M., Vianello, G., Wood, K. S., Wood, M., Zhu, S., Zimmer, S., Brocato, E., Cappellaro, E., Covino, S., Grado, A., Nicastro, L., Palazzi, E., Pian, E., Amati, L., Antonelli, L. A., Capaccioli, M., D'Avanzo, P., D'Elia, V., Getman, F., Giuffrida, G., Iannicola, G., Limatola, L., Lisi, M., Marinoni, S., Marrese, P., Melandri, A., Piranomonte, S., Possenti, A., Pulone, L., Rossi, A., Stamerra, A., Stella, L., Testa, V., Tomasella, L., Yang, S., Bazzano, A., Bozzo, E., Brandt, S., Courvoisier, T. J. -L., Ferrigno, C., Hanlon, L., Kuulkers, E., Laurent, P., Mereghetti, S., Roques, J. P., Savchenko, V., Ubertini, P., Kasliwal, M. M., Singer, L. P., Cao, Y., Duggan, G., Kulkarni, S. R., Bhalerao, V., Miller, A. A., Barlow, T., Bellm, E., Manulis, I., Rana, J., Laher, R., Masci, F., Surace, J., Rebbapragada, U., Van Sistine, A., Sesar, B., Perley, D., Ferreti, R., Prince, T., Kendrick, R., Horesh, A., Hurley, K., Golenetskii, S. V., Aptekar, R. L., Frederiks, D. D., Svinkin, D. S., Rau, A., Zhang, X., Smith, D. M., Cline, T., Krimm, H., Abe, F., Doi, M., Fujisawa, K., Kawabata, K. S., Morokuma, T., Motohara, K., Tanaka, M., Ohta, K., Yanagisawa, K., Yoshida, M., Baltay, C., Rabinowitz, D., Ellman, N., Rostami, S., Bersier, D. F., Bode, M. F., Collins, C. A., Copperwheat, C. M., Darnley, M. J., Galloway, D. K., Gomboc, A., Kobayashi, S., Mazzali, P., Mundell, C. G., Piascik, A. S., Pollacco, Don, Steele, I. A., Ulaczyk, K., Broderick, J. W., Fender, R. P., Jonker, P. G., Rowlinson, A., Stappers, B. W., Wijers, R. A. M. J., Lipunov, V., Gorbovskoy, E., Tyurina, N., Kornilov, V., Balanutsa, P., Kuznetsov, A., Buckley, D., Rebolo, R., Serra-Ricart, M., Israelian, G., Budnev, N. M., Gress, O., Ivanov, K., Poleshuk, V., Tlatov, A., Yurkov, V., Kawai, N., Serino, M., Negoro, H., Nakahira, S., Mihara, T., Tomida, H., Ueno, S., Tsunemi, H., Matsuoka, M., Croft, S., Feng, L., Franzen, T. M. O., Gaensler, B. M., Johnston-Hollitt, M., Kaplan, D. L., Morales, M. F., Tingay, S. J., Wayth, R. B., Williams, A., Smartt, S. J., Chambers, K. C., Smith, K. W., Huber, M. E., Young, D. R., Wright, D. E., Schultz, A., Denneau, L., Flewelling, H., Magnier, E. A., Primak, N., Rest, A., Sherstyuk, A., Stalder, B., Stubbs, C. W., Tonry, J., Waters, C., Willman, M., E., F. Olivares, Campbell, H., Kotak, R., Sollerman, J., Smith, M., Dennefeld, M., Anderson, J. P., Botticella, M. T., Chen, T. -W., Valle, M. D., Elias-Rosa, N., Fraser, M., Inserra, C., Kankare, E., Kupfer, T., Harmanen, J., Galbany, L., Guillou, L. Le, Lyman, J. D., Maguire, K., Mitra, A., Nicholl, M., Razza, A., Terreran, G., Valenti, S., Gal-Yam, A., Ćwiek, A., Ćwiok, M., Mankiewicz, L., Opiela, R., Zaremba, M., Żarnecki, A. F., Onken, C. A., Scalzo, R. A., Schmidt, B. P., Wolf, C., Yuan, F., Evans, P. A., Kennea, J. A., Burrows, D. N., Campana, S., Cenko, S. B., Marshall, F. E., Nousek, J., O'Brien, P., Osborne, J. P., Palmer, D., Perri, M., Siegel, M., Tagliaferri, G., Klotz, A., Turpin, D., Laugier, R., Beroiz, M., Peñuela, T., Macri, L. M., Oelkers, R. J., Lambas, D. G., Vrech, R., Cabral, J., Colazo, C., Dominguez, M., Sanchez, B., Gurovich, S., Lares, M., Marshall, J. L., DePoy, D. L., Padilla, N., Pereyra, N. A., Benacquista, M., Tanvir, N. R., Wiersema, K., Levan, A. J., Steeghs, D., Hjorth, J., Fynbo, J. P. U., Malesani, D., Milvang-Jensen, B., Watson, D., Irwin, M., Fernandez, C. G., McMahon, R. G., Banerji, M., Gonzalez-Solares, E., Schulze, S., Postigo, A. de U., Thoene, C. C., Cano, Z., and Rosswog, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams., Comment: For Supplement, see https://arxiv.org/abs/1604.07864
Published: 2016
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20. Swift follow-up of the Gravitational Wave source GW150914

Author: Evans, P. A., Kennea, J. A., Barthelmy, S. D., Beardmore, A. P., Burrows, D. N., Campana, S., Cenko, S. B., Gehrels, N., Giommi, P., Gronwall, C., Marshall, F. E., Malesani, D., Markwardt, C. B., Mingo, B., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Pagani, C., Page, K. L., Palmer, D. M., Perri, M., Racusin, J. L., Siegel, M. H., Sbarufatti, B., and Tagliaferri, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Advanced LIGO observatory recently reported the first direct detection of gravitational waves (GW) which triggered ALIGO on 2015 September 14. We report on observations taken with the Swift satellite two days after the trigger. No new X-ray, optical, UV or hard X-ray sources were detected in our observations, which were focussed on nearby galaxies in the GW error region and covered 4.7 square degrees (~2% of the probability in the rapidly-available GW error region; 0.3% of the probability from the final GW error region, which was produced several months after the trigger). We describe the rapid Swift response and automated analysis of the X-ray telescope and UV/Optical Telescope data, and note the importance to electromagnetic follow up of early notification of the progenitor details inferred from GW analysis., Comment: 5 pages, 2 figures, 2 tables; accepted by MNRAS Letters. Modified to improve the location and shape of the BAT field of view in Fig. 1
Published: 2016
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21. Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing

Author: Edelson, R, Gelbord, J, Cackett, E, Connolly, S, Done, C, Fausnaugh, M, Gardner, E, Gehrels, N, Goad, M, Horne, K, McHardy, I, Peterson, BM, Vaughan, S, Vestergaard, M, Breeveld, A, Barth, AJ, Bentz, M, Bottorff, M, Brandt, WN, Crawford, SM, Bontà, E Dalla, Emmanoulopoulos, D, Evans, P, Jaimes, R Figuera, Filippenko, AV, Ferland, G, Grupe, D, Joner, M, Kennea, J, Korista, KT, Krimm, HA, Kriss, G, Leonard, DC, Mathur, S, Netzer, H, Nousek, J, Page, K, Romero-Colmenero, E, Siegel, M, Starkey, DA, Treu, T, Vogler, HA, Winkler, H, and Zheng, W
Subjects: galaxies: active, galaxies: individual, galaxies: nuclei, galaxies: Seyfert, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract: Swift monitoring of NGC 4151 with an ∼6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50 keV) and six in the ultraviolet (UV)/optical (1900-5500 Å). The three hardest X-ray bands (>2.5 keV) are all strongly correlated with no measurable interband lag, while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ∼3-4 days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by ∼0.5-1 days. This combination of ≳3 day lags between the X-rays and UV and ≲1 day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.
Published: 2017

22. Swift/UVOT discovery of Swift J221951-484240:a UV luminous ambiguous nuclear transient

Author: Oates, S R, Kuin, N P M, Nicholl, M, Marshall, F, Ridley, E, Boutsia, K, Breeveld, A A, Buckley, D A H, Cenko, S B, De pasquale, M, Edwards, P G, Gromadzki, M, Gupta, R, Laha, S, Morrell, N, Orio, M, Pandey, S B, Page, M J, Page, K L, Parsotan, T, Rau, A, Schady, P, Stevens, J, Brown, P J, Evans, P A, Gronwall, C, Kennea, J A, Klingler, N J, Siegel, M H, Tohuvavohu, A, Ambrosi, E, Barthelmy, S D, Beardmore, A P, Bernardini, M G, Bonnerot, C, Campana, S, Caputo, R, Ciroi, S, Cusumano, G, D’aì, A, D’avanzo, P, D’elia, V, Giommi, P, Hartmann, D H, Krimm, H A, Malesani, D B, Melandri, A, Nousek, J A, O’brien, P T, Osborne, J P, Pagani, C, Palmer, D M, Perri, M, Racusin, J L, Sakamoto, T, Sbarufatti, B, Schlieder, J E, Tagliaferri, G, Troja, E, Xu, D, Oates, S R, Kuin, N P M, Nicholl, M, Marshall, F, Ridley, E, Boutsia, K, Breeveld, A A, Buckley, D A H, Cenko, S B, De pasquale, M, Edwards, P G, Gromadzki, M, Gupta, R, Laha, S, Morrell, N, Orio, M, Pandey, S B, Page, M J, Page, K L, Parsotan, T, Rau, A, Schady, P, Stevens, J, Brown, P J, Evans, P A, Gronwall, C, Kennea, J A, Klingler, N J, Siegel, M H, Tohuvavohu, A, Ambrosi, E, Barthelmy, S D, Beardmore, A P, Bernardini, M G, Bonnerot, C, Campana, S, Caputo, R, Ciroi, S, Cusumano, G, D’aì, A, D’avanzo, P, D’elia, V, Giommi, P, Hartmann, D H, Krimm, H A, Malesani, D B, Melandri, A, Nousek, J A, O’brien, P T, Osborne, J P, Pagani, C, Palmer, D M, Perri, M, Racusin, J L, Sakamoto, T, Sbarufatti, B, Schlieder, J E, Tagliaferri, G, Troja, E, and Xu, D
Published: 2024

23. Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548

Author: Fausnaugh, M. M., Denney, K. D., Barth, A. J., Bentz, M. C., Bottorff, M. C., Carini, M. T., Croxall, K. V., De Rosa, G., Goad, M. R., Horne, Keith, Joner, M. D., Kaspi, S., Kim, M., Klimanov, S. A., Kochanek, C. S., Leonard, D. C., Netzer, H., Peterson, B. M., Schnulle, K., Sergeev, S. G., Vestergaard, M., Zheng, W. -K., Zu, Y., Anderson, M. D., Arevalo, P., Bazhaw, C., Borman, G. A., Boroson, T. A., Brandt, W. N., Breeveld, A. A., Brewer, B. J., Cackett, E. M., Crenshaw, D. M., Bonta, E. Dalla, De Lorenzo-Caceres, A., Dietrich, M., Edelson, R., Efimova, N. V., Ely, J., Evans, P. A., Filippenko, A. V., Flatland, K., Gehrels, N., Geier, S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Grier, C. J., Grupe, D., Hall, P. B., Hicks, S., Horenstein, D., Hutchison, T., Im, M., Jensen, J. J., Jones, J., Kaastra, J., Kelly, B. C., Kennea, J. A., Kim, S. C., Korista, K. T., Kriss, G. A., Lee, J. C., Lira, P., MacInnis, F., Manne-Nicholas, E. R., Mathur, S., McHardy, I. M., Montouri, C., Musso, R., Nazarov, S. V., Norris, R. P., Nousek, J. A., Okhmat, D. N., Pancoast, A., Papadakis, I., Parks, J. R., Pei, L., Pogge, R. W., Pott, J. -U., Rafter, S. E., Rix, H. -W., Saylor, D. A., Schimoia, J. S., Siegel, M., Spencer, M., Starkey, D., Sung, H. -I., Teems, K. G., Treu, T., Turner, C. S., Uttley, P., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., and Young, S.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multi-wavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters (\emph{BVRI} and \emph{ugriz}). Combined with ultraviolet data from the \emph{Hubble Space Telescope} and \emph{Swift}, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from 1158\,\AA\ to the $z$ band ($\sim\!9160$\,\AA). We find that the lags at wavelengths longer than the {\it V} band are equal to or greater than the lags of high-ionization-state emission lines (such as He\,{\sc ii}\,$\lambda 1640$ and $\lambda 4686$), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with $\tau \propto \lambda^{4/3}$. However, the lags also imply a disk radius that is 3 times larger than the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10\% of the Eddington luminosity ($L = 0.1L_{\rm Edd}$). Using optical spectra from the Large Binocular Telescope, we estimate the bias of the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with high levels of BLR contamination ($\sim\! 20\%$) can be important for the shortest continuum lags, and likely has a significant impact on the {\it u} and {\it U} bands owing to Balmer continuum emission., Comment: 26 pages, 10 figures, accepted to ApJ. For a brief video describing the main results of this paper, please see: https://www.youtube.com/watch?v=yaYtcDvIoP0&feature=youtu.be
Published: 2015
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24. Space Telescope and Optical Reverberation Mapping Project. I. Ultraviolet Observations of the Seyfert 1 Galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope

Author: De Rosa, G., Peterson, B. M., Ely, J., Kriss, G. A., Crenshaw, D. M., Horne, Keith, Korista, K. T., Netzer, H., Pogge, R. W., Arevalo, P., Barth, A. J., Bentz, M. C., Brandt, W. N., Breeveld, A. A., Brewer, B. J., Bonta, E. Dalla, De Lorenzo-Caceres, A., Denney, K. D., Dietrich, M., Edelson, R., Evans, P. A., Fausnaugh, M. M., Gehrels, N., Gelbord, J. M., Goad, M. R., Grier, C. J., Grupe, D., Hall, P. B., Kaastra, J., Kelly, B. C., Kennea, J. A., Kochanek, C. S., Lira, P., Mathur, S., McHardy, I. M., Nousek, J. A., Pancoast, A., Papadakis, I., Pei, L., Schimoia, J. S., Siegel, M., Starkey, D., Treu, T., Uttley, P., Vaughan, S., Vestergaard, M., Villforth, C., Yan, H., Young, S., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 170 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correlated variability is found in the continuum and broad emission lines, with amplitudes ranging from ~30% to a factor of two in the emission lines and a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He II 1640 lagging behind the continuum by ~2.5 days and Lyman alpha 1215, C IV 1550, and Si IV 1400 lagging by ~5-6 days. The relationship between the continuum and emission lines is complex. In particular, during the second half of the campaign, all emission-line lags increased by a factor of 1.3-2 and differences appear in the detailed structure of the continuum and emission-line light curves. Velocity-resolved cross-correlation analysis shows coherent structure in lag versus line-of-sight velocity for the emission lines; the high-velocity wings of C IV respond to continuum variations more rapidly than the line core, probably indicating higher velocity BLR clouds at smaller distances from the central engine. The velocity-dependent response of Lyman alpha, however, is more complex and will require further analysis., Comment: Accepted for publication in The Astrophysical Journal. 20 pages, 6 figures, 4 tables. See also STORM Paper II "Space telescope and optical reverberation mapping project. II. Reverberation mapping of the accretion disk with SWIFT and HST" by R. Edelson et al
Published: 2015
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25. Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548

Author: Edelson, R., Gelbord, J. M., Horne, K., McHardy, I. M., Peterson, B. M., Arevalo, P., Breeveld, A. A., De Rosa, G., Evans, P. A., Goad, M. R., Kriss, G. A., Brandt, W. N., Gehrels, N., Grupe, D., Kennea, J. A., Kochanek, C. S., Nousek, J. A., Papadakis, I., Siegel, M., Starkey, D., Uttley, P., Vaughan, S., Young, S., Barth, A. J., Bentz, M. C., Brewer, B. J., Crenshaw, D. M., Bonta, E. Dalla, De Lorenzo-Caceres, A., Denney, K. D., Dietrich, M., Ely, J., Fausnaugh, M. M., Grier, C. J., Hall, P. B., Kaastra, J., Kelly, B. C., Korista, K. T., Lira, P., Mathur, S., Netzer, H., Pancoast, A., Pei, L., Pogge, R. W., Schimoia, J. S., Treu, T., Vestergaard, M., Villforth, C., Yan, H., and Zu, Y.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended AGN UV/optical continuum sampling ever obtained, with a mean sampling rate <0.5 day. Approximately daily HST UV sampling was also obtained. The UV/optical light curves show strong correlations (r_max = 0.57 - 0.90) and the clearest measurement to date of interband lags. These lags are well-fit by a \tau propto \lambda^4/3 wavelength dependence, with a normalization that indicates an unexpectedly large disk radius of 0.35 +/- 0.05 lt-day at 1367 A, assuming a simple face-on model. The U-band shows a marginally larger lag than expected from the fit and surrounding bands, which could be due to Balmer continuum emission from the broad-line region as suggested by Korista and Goad. The UV/X-ray correlation is weaker (r_max < 0.45) and less consistent over time. This indicates that while Swift is beginning to measure UV/optical lags in general agreement with accretion disk theory (although the derived size is larger than predicted), the relationship with X-ray variability is less well understood. Combining this accretion disk size estimate with those from quasar microlensing studies suggests that AGN disk sizes scale approximately linearly with central black hole mass over a wide range of masses., Comment: Accepted for publication in the Astrophysical Journal. Seventeen pages, 10 figures, 6 tables. See also STORM Paper I: "Space Telescope and Optical Reverberation Mapping Project. I. Ultraviolet Observations of the Seyfert 1 Galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope" by G. De Rosa et al., http://arxiv.org/abs/1501.05954
Published: 2015
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26. GRB 130427A: a Nearby Ordinary Monster

Author: Maselli, A., Melandri, A., Nava, L., Mundell, C. G., Kawai, N., Campana, S., Covino, S., Cummings, J. R., Cusumano, G., Evans, P. A., Ghirlanda, G., Ghisellini, G., Guidorzi, C., Kobayashi, S., Kuin, P., La Parola, V., Mangano, V., Oates, S., Sakamoto, T., Serino, M., Virgili, F., Zhang, B. -B., Barthelmy, S., Beardmore, A., Bernardini, M. G., Bersier, D., Burrows, D., Calderone, G., Capalbi, M., Chiang, J., D'Avanzo, P., D'Elia, V., De Pasquale, M., Fugazza, D., Gehrels, N., Gomboc, A., Harrison, R., Hanayama, H., Japelj, J., Kennea, J., Kopac, D., Kouveliotou, C., Kuroda, D., Levan, A., Malesani, D., Marshall, F., Nousek, J., O'Brien, P., Osborne, J. P., Pagani, C., Page, K. L., Page, M., Perri, M., Pritchard, T., Romano, P., Saito, Y., Sbarufatti, B., Salvaterra, R., Steele, I., Tanvir, N., Vianello, G., Wiegand, B., Wiersema, K., Yatsu, Y., Yoshii, T., and Tagliaferri, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Long-duration Gamma-Ray Bursts (GRBs) are an extremely rare outcome of the collapse of massive stars, and are typically found in the distant Universe. Because of its intrinsic luminosity ($L\sim 3 \times 10^{53}$ erg s$^{-1}$) and its relative proximity ($z=0.34$), GRB 130427A was a unique event that reached the highest fluence observed in the gamma-ray band. Here we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-m Liverpool and Faulkes telescopes and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early Universe and over the full range of GRB isotropic energies., Comment: 64 pages, 11 figures; published in Science. Update for a few references and correction of a typo in the name of one of the authors
Published: 2013
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27. The seven year Swift-XRT point source catalog (1SWXRT)

Author: D'Elia, V., Perri, M., Puccetti, S., Capalbi, M., Giommi, P., Burrows, D. N., Campana, S., Tagliaferri, G., Cusumano, G., Evans, P., Gehrels, N., Kennea, J., Moretti, A., Nousek, J. A., Osborne, J. P., Romano, P., and Stratta, G.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Swift is a multi-wavelength observatory specifically designed for gamma-ray burst (GRB) astronomy that is operational since 2004. Swift is also a very flexible multi-purpose facility that supports a wide range of scientific fields such as active galactic nuclei, supernovae, cataclysmic variables, Galactic transients, active stars and comets. The Swift X-ray Telescope (XRT) has collected more than 150 Ms of observations in its first seven years of operations. We present the list of all the X-ray point sources detected in XRT imaging data taken in photon counting mode during the first seven years of Swift operations. All these point-like sources, excluding the Gamma-Ray Bursts (GRB), will be stored in a catalog publicly available (1SWXRT). We consider all XRT observations with exposure time > 500 s taken in the period 2005-2011. Data were reduced and analyzed with standard techniques and a list of detected sources for each observation was produced. A careful visual inspection was performed to remove extended, spurious and piled-up sources. Positions, count rates, fluxes and the corresponding uncertainties were computed. We have analyzed more than 35,000 XRT fields, with exposures ranging between 500 s and 100 ks, for a total exposure time of 140 Ms. The catalog includes ~ 89,000 entries, of which almost 85,000 are not affected by pile-up and are not GRBs. Since many XRT fields were observed several times, we have a total of ~36,000 distinct celestial sources. We computed count rates in three energy bands: 0.3-10 keV (Full, or F), 0.3-3 keV (Soft, or S) and 2-10 keV (Hard, or H). Each entry has a detection in at least one of these bands. In particular, we detect ~ 80,000, ~ 70,000 and ~ 25,500$ in the F, S and H band, respectively. Count rates were converted into fluxes in the 0.5-10, 0.5-2 and 2-10 keV bands. Some possible scientific uses of the catalog are also highlighted., Comment: 11 pages, 15 ps figures, accepted for publication in A&A. Abstract shortened with respect to the original version
Published: 2013
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28. The prompt-afterglow connection in Gamma-Ray Bursts: a comprehensive statistical analysis of Swift X-ray light-curves

Author: Margutti, R., Zaninoni, E., Bernardini, M. G., Chincarini, G., Pasotti, F., Guidorzi, C., Angelini, L., Burrows, D. N., Capalbi, M., Evans, P. A., Gehrels, N., Kennea, J., Mangano, V., Moretti, A., Nousek, J., Osborne, J. P., Page, K. L., Perri, M., Racusin, J., Romano, P., Sbarufatti, B., Stafford, S., and Stamatikos, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present a comprehensive statistical analysis of Swift X-ray light-curves of Gamma-Ray Bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the REST FRAME X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30 keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: i) Does the X-ray emission retain any kind of "memory"of the prompt gamma-ray phase? ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt gamma-ray parameters in long GRBs; short GRBs are outliers of the majority of these 2-parameter relations. However and more importantly, we report on the existence of a universal 3-parameter scaling that links the X-ray and the gamma-ray energy to the prompt spectral peak energy of BOTH long and short GRBs: E_{X,iso}\propto E_{gamma,iso}^{1.00\pm 0.06}/E_{pk}^{0.60\pm 0.10}., Comment: MNRAS Accepted. 15 pages. On-line tables available
Published: 2012
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29. The Swift Serendipitous Survey in deep XRT GRB fields (SwiftFT) I. The X-ray catalog and number counts

Author: Puccetti, S., Capalbi, M., Giommi, P., Perri, M., Stratta, G., Angelini, L., Burrows, D. N., Campana, S., Chincarini, G., Cusumano, G., Gehrels, N., Moretti, A., Nousek, J., Osborne, J. P., and Tagliaferri, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We searched for X-ray serendipitous sources in over 370 Swift-XRT fields centered on gamma ray bursts detected between 2004 and 2008 and observed with total exposures ranging from 10 ks to over 1 Ms. This defines the Swift Serendipitous Survey in deep XRT GRB fields, which is quite broad compared to existing surveys (~33 square degrees) and medium depth, with a faintest flux limit of 7.2e-16 erg cm^-2 s^-1 in the 0.5 to 2 keV energy range. The survey has a high degree of uniformity thanks to the stable point spread function and small vignetting correction factors of the XRT, moreover is completely random on the sky as GRBs explode in totally unrelated parts of the sky. In this paper we present the sample and the X-ray number counts of the high Galactic-latitude sample, estimated with high statistics over a wide flux range (i.e., 7.2e-16 to ~5e-13 erg cm^-2 s^-1 in the 0.5-2 keV band and 3.4e-15 to ~6e-13 erg cm^-2 s^-1 in the 2-10 keV band). We detect 9387 point-like sources, while 7071 point-like sources are found at high Galactic-latitudes (i.e. >=20 deg). The large number of detected sources resulting from the combination of large area and deep flux limits make this survey a new important tool for investigating the evolution of AGN. In particular, the large area permits finding rare high-luminosity objects like QSO2, which are poorly sampled by other surveys, adding precious information for the luminosity function bright end. The high Galactic-latitude logN-logS relation is well determined over all the flux coverage, and it is nicely consistent with previous results at 1 sigma confidence level. By the hard X-ray color analysis, we find that the Swift Serendipitous Survey in deep XRT GRB fields samples relatively unobscured and mildly obscured AGN, with a fraction of obscured sources of ~37% (~15%) in the 2-10 (0.3-3 keV) band., Comment: Accepted for publication in A&A
Published: 2011
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30. A Statistical Comparison of the Optical/UV and X-ray Afterglows of Gamma-Ray Bursts using the Swift Ultra-violet Optical and X-ray Telescopes

Author: Oates, S. R., Page, M. J., Schady, P., De Pasquale, M., Evans, P. A., Page, K. L., Chester, M. M., Curran, P. A., Koch, T. S., Kuin, N. P. M., Roming, P. W. A., Siegel, M. H., Zane, S., and Nousek, J. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the systematic analysis of the UVOT and XRT light curves for a sample of 26 Swift Gamma-Ray Bursts (GRBs). By comparing the optical/UV and X-ray light curves, we found that they are remarkably different during the first 500s after the BAT trigger, while they become more similar during the middle phase of the afterglow, i.e. between 2000s and 20000s. If we take literally the average properties of the sample, we find that the mean temporal indices observed in the optical/UV and X-rays after 500s are consistent with a forward-shock scenario, under the assumptions that electrons are in the slow cooling regime, the external medium is of constant density and the synchrotron cooling frequency is situated between the optical/UV and X-ray observing bands. While this scenario describes well the averaged observed properties, some individual GRB afterglows require different or additional assumptions, such as the presence of late energy injection. We show that a chromatic break (a break in the X-ray light curve that is not seen in the optical) is present in the afterglows of 3 GRBs and demonstrate evidence for chromatic breaks in a further 4 GRBs. The average properties of these breaks cannot be explained in terms of the passage of the synchrotron cooling frequency through the observed bands, nor a simple change in the external density. It is difficult to reconcile chromatic breaks in terms of a single component outflow and instead, more complex jet structure or additional emission components are required., Comment: 20 pages, 5 figures and 4 tables. Accepted for publication by MNRAS
Published: 2010
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31. GRB 090423 at a redshift of z~8.1

Author: Salvaterra, R., Della Valle, M., Campana, S., Chincarini, G., Covino, S., D'Avanzo, P., Fernandez-Soto, A., Guidorzi, C., Mannucci, F., Margutti, R., Thoene, C. C., Antonelli, L. A., Barthelmy, S. D., De Pasquale, M., D'Elia, V., Fiore, F., Fugazza, D., Hunt, L. K., Maiorano, E., Marinoni, S., Marshall, F. E., Molinari, E., Nousek, J., Pian, E., Racusin, J. L., Stella, L., Amati, L., Andreuzzi, G., Cusumano, G., Fenimore, E. E., Ferrero, P., Giommi, P., Guetta, D., Holland, S. T., Hurley, K., Israel, G. L., Mao, J., Markwardt, C. B., Masetti, N., Pagani, C., Palazzi, E., Palmer, D. M., Piranomonte, S., Tagliaferri, G., and Testa, V.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Gamma-ray bursts (GRBSs) are produced by rare types of massive stellar explosions. Their rapidly fading afterglows are often bright enough at optical wavelengths, that they are detectable up to cosmological distances. Hirtheto, the highest known redshift for a GRB was z=6.7, for GRB 080913, and for a galaxy was z=6.96. Here we report observations of GRB 090423 and the near-infrared spectroscopic measurement of its redshift z=8.1^{+0.1}_{-0.3}. This burst happened when the Universe was only ~4% of its current age. Its properties are similar to those of GRBs observed at low/intermediate redshifts, suggesting that the mechanisms and progenitors that gave rise to this burst about 600 million years after the Big Bang are not markedly different from those producing GRBs ~10 billion years later., Comment: Published in Nature. The astro-ph paper includes the main text (8 pages, 2 figures) and supplementary material (13 pages, 6 figures)
Published: 2009
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32. The Collimation and Energetics of the Brightest Swift Gamma-Ray Bursts

Author: Cenko, S. B., Frail, D. A., Harrison, F. A., Kulkarni, S. R., Nakar, E., Chandra, P., Butler, N. R., Fox, D. B., Gal-Yam, A., Kasliwal, M. M., Kelemen, J., Moon, D. -S., Price, P. A., Rau, A., Soderberg, A. M., Teplitz, H. I., Werner, M. W., Bock, D. C. -J., Bloom, J. S., Starr, D. A., Filippenko, A. V., Chevalier, R. A., Gehrels, N., Nousek, J. N., and Piran, T.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Long-duration gamma-ray bursts (GRBs) are widely believed to be highly-collimated explosions (opening angle theta ~ 1-10 deg). As a result of this beaming factor, the true energy release from a GRB is usually several orders of magnitude smaller than the observed isotropic value. Measuring this opening angle, typically inferred from an achromatic steepening in the afterglow light curve (a "jet" break), has proven exceedingly difficult in the Swift era. Here we undertake a study of five of the brightest (in terms of the isotropic prompt gamma-ray energy release, E(gamma, iso)) GRBs in the Swift era to search for jet breaks and hence constrain the collimation-corrected energy release. We present multi-wavelength (radio through X-ray) observations of GRBs 050820A, 060418, and 080319B, and construct afterglow models to extract the opening angle and beaming-corrected energy release for all three events. Together with results from previous analyses of GRBs 050904 and 070125, we find evidence for an achromatic jet break in all five events, strongly supporting the canonical picture of GRBs as collimated explosions. The most natural explanation for the lack of observed jet breaks from most Swift GRBs is therefore selection effects. However, the opening angles for the events in our sample are larger than would be expected if all GRBs had a canonical energy release of ~ 10e51 erg. The total energy release we measure for those "hyper-energetic" (E(total) >~ 10e52 erg) events in our sample is large enough to start challenging models with a magnetar as the compact central remnant., Comment: Submitted to ApJ, comments welcome
Published: 2009
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33. A statistical study of gamma-ray burst afterglows measured by the Swift Ultra-violet Optical Telescope

Author: Oates, S. R., Page, M. J., Schady, P., de Pasquale, M., Koch, T. S., Breeveld, A. A., Brown, P. J., Chester, M. M., Holland, S. T., Hoversten, E. A., Kuin, N. P. M., Marshall, F. E., Roming, P. W. A., Still, M., Berk, D. E. Vanden, Zane, S., and Nousek, J. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the first statistical analysis of 27 UVOT optical/ultra-violet lightcurves of GRB afterglows. We have found, through analysis of the lightcurves in the observer's frame, that a significant fraction rise in the first 500s after the GRB trigger, that all lightcurves decay after 500s, typically as a power-law with a relatively narrow distribution of decay indices, and that the brightest optical afterglows tend to decay the quickest. We find that the rise could either be produced physically by the start of the forward shock, when the jet begins to plough into the external medium, or geometrically where an off-axis observer sees a rising lightcurve as an increasing amount of emission enters the observers line of sight, which occurs as the jet slows. We find that at 99.8% confidence, there is a correlation, in the observed frame, between the apparent magnitude of the lightcurves at 400s and the rate of decay after 500s. However, in the rest frame a Spearman Rank test shows only a weak correlation of low statistical significance between luminosity and decay rate. A correlation should be expected if the afterglows were produced by off-axis jets, suggesting that the jet is viewed from within the half-opening angle theta or within a core of uniform energy density theta_c. We also produced logarithmic luminosity distributions for three rest frame epochs. We find no evidence for bimodality in any of the distributions. Finally, we compare our sample of UVOT lightcurves with the XRT lightcurve canonical model. The range in decay indices seen in UVOT lightcurves at any epoch is most similar to the range in decay of the shallow decay segment of the XRT canonical model. However, in the XRT canonical model there is no indication of the rising behaviour observed in the UVOT lightcurves., Comment: 16 pages, 9 figures, accepted MNRAS
Published: 2009
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34. A new measurement of the cosmic X-ray background

Author: Moretti, A., Pagani, C., Cusumano, G., Campana, S., Perri, M., Abbey, A., Ajello, M., Beardmore, A. P., Burrows, D., Chincarini, G., Godet, O., Guidorzi, C., Hill, J. E., Kennea, J., Nousek, J., Osborne, J. P., and Tagliaferri, G.
Subjects: Astrophysics
Abstract: We present a new measurement of the cosmic X-ray background (CXRB) in the 1.5-7 keV energy band, performed by exploiting the Swift X-ray telescope (XRT) data archive. We also present a CXRB spectral model in a wider energy band (1.5-200 keV), obtained by combining these data with the recently published Swift-BAT measurement. From the XRT archive we collect a complete sample of 126 high Galactic latitude gamma-ray burst (GRB) follow-up observations. This provides a total exposure of 7.5 Ms and a sky-coverage of 7 square degrees which represents a serendipitous survey, well suited for a direct measurement of the CXRB in the 1.5-10 keV interval. Our work is based on a complete characterization of the instrumental background and an accurate measurement of the stray-light contamination and vignetting calibration. We find that the CXRB spectrum in the 1.5-7 keV energy band can be equally well fitted by a single power-law with photon index Gamma=1.47+/-0.07 or a single power-law with photon index Gamma=1.41+/-0.06 and an exponential roll-off at 41 keV. The measured flux in the 2-10 keV energy band is 2.18+/-0.13 E-11 erg/(cm2 s deg2) in the 2-10 keV band. Combining Swift-XRT with Swift-BAT (15-200 keV) we find that, in the 1.5-200 keV band, the CXRB spectrum can be well described by two smoothly-joined power laws with the energy break at 29.0+/-0.5 keV corresponding to a nu F_nu peak located at 22.4+/-0.4 keV. Taking advantage of both the Swift high energy instruments (XRT and BAT), we produce an analytical description of the CXRB spectrum over a wide (1.5-200 keV) energy band. This model is marginally consistent with the HEAO1 measurement (~10% higher at energies higher than 20 keV, while it is significantly (30%) higher at low energies (2-10 keV)., Comment: Accepted for publication by A&A; 9 pages, 11 figures. Typo corrected in units of Tab. 2; update Fig. 11
Published: 2008
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35. INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables

Author: Landi, R., Bassani, L., Dean, A. J., Bird, A. J., Fiocchi, M., Bazzano, A., Nousek, J. A., and Osborne, J. P.
Subjects: Astrophysics
Abstract: The analysis of the third INTEGRAL/IBIS survey has revealed several new cataclysmic variables, most of which turned out to be intermediate polars, thus confirming that these objects are strong emitters in hard X-rays. Here we present high energy spectra of all 22 cataclysmic variables detected in the 3rd IBIS survey and provide the first average spectrum over the 20-100 keV band for this class. Our analysis indicates that the best-fit model is a thermal bremsstrahlung with an average temperature of ~22 keV. Recently, eleven (ten intermediate polars and one polar) of these systems have been followed-up by Swift/XRT (operating in the 0.3-10 keV energy band), thus allowing us to investigate their spectral behaviour over the range ~0.3-100 keV. Thanks to this wide energy coverage, it was possible for these sources to simultaneously measure the soft and hard components and estimate their temperatures. The soft emission, thought to originate in the irradiated poles of the white dwarf atmosphere, is well described by a blackbody model with temperatures in the range ~60-120 eV. The hard emission, which is supposed to be originated from optically thin plasma in the post-shock region above the magnetic poles, is indeed well modelled with a bremsstrahlung model with temperatures in the range ~16-33 keV, similar to the values obtained from the INTEGRAL data alone. In several cases we also find the presence of a complex absorber: one totally (with NH ~(0.4-28) x 10^{21} cm^{-2}) and one partially (with NH ~(0.7-9) x 10^{23} cm^{-2}) covering the source. Only in four cases (V709 Cas, GK Per, IGR J06253+7334 and IGR J17303-0601), we find evidence for the presence of an iron line at 6.4 keV. We discuss our findings in the light of the systems parameters and cataclysmic variables/intermediate polars modelling scenario., Comment: 16 pages, including 6 figures and 5 tables. Accepted for publication in MNRAS
Published: 2008
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36. Optimal Coaddition of Imaging Data for Rapidly Fading Gamma-Ray Burst Afterglows

Author: Morgan, A. N., Berk, D. E. Vanden, Roming, P. W. A., Nousek, J. A., Koch, T. S., Breeveld, A. A., de Pasquale, M., Holland, S. T., Kuin, N. P. M., Page, M. J., and Still, M.
Subjects: Astrophysics
Abstract: We present a technique for optimal coaddition of image data for rapidly varying sources, with specific application to gamma-ray burst (GRB) afterglows. Unweighted coaddition of rapidly fading afterglow lightcurve data becomes counterproductive relatively quickly. It is better to stop coaddition of the data once noise dominates late exposures. A better alternative is to optimally weight each exposure to maximize the signal-to-noise ratio (S/N) of the final coadded image data. By using information about GRB lightcurves and image noise characteristics, optimal image coaddition increases the probability of afterglow detection and places the most stringent upper limits on non-detections. For a temporal power law flux decay typical of GRB afterglows, optimal coaddition has the greatest potential to improve the S/N of afterglow imaging data (relative to unweighted coaddition), when the decay rate is high, the source count rate is low, and the background rate is high. The optimal coaddition technique is demonstrated with applications to Swift Ultraviolet/Optical Telescope (UVOT) data of several GRBs, with and without detected afterglows., Comment: 17 pages, accepted for publication in ApJ
Published: 2008
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37. Swift and Chandra Detections of Supernova 2006jc: Evidence for Interaction of the Supernova Shock with a Circumstellar Shell

Author: Immler, S., Modjaz, M., Landsman, W., Bufano, F., Brown, P. J., Milne, P., Dessart, L., Holland, S. T., Koss, M., Pooley, D., Kirshner, R. P., Filippenko, A. V., Panagia, N., Chevalier, R. A., Mazzali, P. A., Gehrels, N., Petre, R., Burrows, D. N., Nousek, J. A., Roming, P. W. A., Pian, E., Soderberg, A. M., and Greiner, J.
Subjects: Astrophysics
Abstract: The peculiar Type Ib supernova (SN) 2006jc has been observed with the UV/Optical Telescope (UVOT) and X-Ray Telescope (XRT) on board the Swift observatory over a period of 19 to 183 days after the explosion. Signatures of interaction of the outgoing SN shock with dense circumstellar material (CSM) are detected, such as strong X-ray emission (L_{0.2-10} > E39 erg/s) and the presence of MgII 2800A line emission visible in the UV spectra. In combination with a Chandra observation obtained on day 40 after the explosion, the X-ray light curve is constructed, which shows a unique rise of the X-ray emission by a factor of ~5 over a period of ~4 months, followed by a rapid decline. We interpret the unique X-ray and UV properties as a result of the SN shock interacting with a shell of material that was deposited by an outburst of the SN progenitor two years prior to the explosion. Our results are consistent with the explosion of a Wolf-Rayet star that underwent an episodic mass ejection qualitatively similar to those of luminous blue variable stars prior to its explosion. This led to the formation of a dense (>E7 cm**-3) shell at a distance of ~E16 cm from the site of the explosion, which expands with the WR wind at a velocity of (1300+/-300) km/s., Comment: 4 pages, 4 figures, submitted to ApJL (v2)
Published: 2007
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38. The in-flight spectroscopic performance of the Swift XRT CCD camera during 2006-2007

Author: Godet, O., Beardmore, A. P., Abbey, A. F., Osborne, J. P., Page, K. L., Tyler, L., Burrows, D. N., Evans, P., Starling, R., Wells, A. A., Angelini, L., Campana, S., Chincarini, G., Citterio, O., Cusumano, G., Giommi, P., Hill, J. E., Kennea, J., LaParola, V., Mangano, V., Mineo, T., Moretti, A., Nousek, J. A., Pagani, C., Perri, M., Capalbi, M., Romano, P., Tagliaferri, G., and Tamburelli, F.
Subjects: Astrophysics
Abstract: The Swift X-ray Telescope focal plane camera is a front-illuminated MOS CCD, providing a spectral response kernel of 135 eV FWHM at 5.9 keV as measured before launch. We describe the CCD calibration program based on celestial and on-board calibration sources, relevant in-flight experiences, and developments in the CCD response model. We illustrate how the revised response model describes the calibration sources well. Comparison of observed spectra with models folded through the instrument response produces negative residuals around and below the Oxygen edge. We discuss several possible causes for such residuals. Traps created by proton damage on the CCD increase the charge transfer inefficiency (CTI) over time. We describe the evolution of the CTI since the launch and its effect on the CCD spectral resolution and the gain., Comment: 8 pages, 5 colour figures, submitted to SPIE
Published: 2007
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39. The exceptionally extended flaring activity in the X-ray afterglow of GRB 050730 observed with Swift and XMM-Newton

Author: Perri, M., Guetta, D., Antonelli, L. A., Cucchiara, A., Mangano, V., Reeves, J., Angelini, L., Beardmore, A. P., Boyd, P., Burrows, D. N., Campana, S., Capalbi, M., Chincarini, G., Cusumano, G., Giommi, P., Hill, J. E., Holland, S. T., La Parola, V., Mineo, T., Moretti, A., Nousek, J. A., Osborne, J. P., Pagani, C., Romano, P., Roming, P. W. A., Starling, R. L. C., Tagliaferri, G., Troja, E., Vetere, L., and Gehrels, N.
Subjects: Astrophysics
Abstract: We present the results of a detailed spectral and temporal analysis of Swift and XMM-Newton observations of the high redshift (z=3.969) GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with superimposed intense flaring activity that extended over more than two orders of magnitude in time. Seven distinct re-brightening events starting from 236 s up to 41.2 ks after the burst were observed. The underlying decay of the afterglow was well described by a double broken power-law model with breaks at t_1= 237 +/- 20 s and t_2 = 10.1 (-2.2) (+4.6) ks. The temporal decay slopes before, between and after these breaks were alpha_1 = 2.1 +/- 0.3, alpha_2 = 0.44 (-0.08) (+0.14) and alpha_3 = 2.40 (+0.07) (-0.09), respectively. The spectrum of the X-ray afterglow was well described by a photoelectrically absorbed power-law with an absorbing column density N_H=(1.28 +/- 0.26) 10^22 cm^-2 in the host galaxy. Strong X-ray spectral evolution during the flaring activity was present. In the majority of the flares (6/7) the ratio Delta_t/t_p between the duration of the event and the time when the flare peaks was nearly constant and about 0.6-0.7. We showed that the observed spectral and temporal properties of the first three flares are consistent with being due both to high-latitude emission, as expected if the flares were produced by late internal shocks, or to refreshed shocks, i.e. late time energy injections into the main afterglow shock by slow moving shells ejected from the central engine during the prompt phase. The event fully satisfies the E_p-E_iso Amati relation while is not consistent with the E_p-E_jet Ghirlanda relation., Comment: 12 pages, 5 figures, accepted for publication in A&A
Published: 2007
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40. X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission

Author: Immler, S., Brown, P. J., Milne, P., Dessart, L., Mazzali, P. A., Landsman, W., Gehrels, N., Petre, R., Burrows, D. N., Nousek, J. A., Chevalier, R. A., Williams, C. L., Koss, M., Stockdale, C. J., Kelley, M. T., Weiler, K. W., Holland, S. T., Pian, E., Roming, P. W. A., Pooley, D., Nomoto, K., Greiner, J., Campana, S., and Soderberg, A. M.
Subjects: Astrophysics
Abstract: We present results on the X-ray and optical/UV emission from the type IIP SN 2006bp and the interaction of the SN shock with its environment, obtained with the X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) on-board the Swift observatory. SN 2006bp is detected in X-rays at a 4.5 sigma level of significance in the merged XRT data from days 1 to 12 after the explosion. If the X-ray luminosity of (1.8+/-0.4)E39 ergs/s is caused by interaction of the SN shock with circumstellar material (CSM), deposited by a stellar wind from the progenitor's companion star, a mass-loss rate of ~E-05 M_sun/yr is inferred. The mass-loss rate is consistent with the non-detection in the radio with the VLA on days 2, 9, and 11 after the explosion and characteristic of a red supergiant progenitor with a mass around 12-15 M_sun prior to the explosion. In combination with a follow-up XMM-Newton observation obtained on day 21 after the explosion, an X-ray rate of decline with index 1.2+/-0.6 is inferred. Since no other SN has been detected in X-rays prior to the optical peak and since type IIP SNe have an extended 'plateau' phase in the optical, we discuss the scenario that the X-rays might be due to inverse Compton scattering of photospheric optical photons off relativistic electrons produced in circumstellar shocks. However, due to the high required value of the Lorentz factor (~10-100) we conclude that Inverse Compton scattering is an unlikely explanation for the observed X-ray emission. The fast evolution of the optical/ultraviolet spectral energy distribution and the spectral changes observed with Swift reveal the onset of metal line-blanketing and cooling of the expanding photosphere during the first few weeks after the outburst., Comment: 8 pages, 5 figures, accepted for publication in ApJ
Published: 2007
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41. GRB 060505: A possible short-duration gamma-ray burst in a star forming region at redshift of 0.09

Author: Ofek, E. O., Cenko, S. B., Gal-Yam, A., Fox, D. B., Nakar, E., Rau, A., Frail, D. A., Kulkarni, S. R., Price, P. A., Schmidt, B. P., Soderberg, A. M., Peterson, B., Berger, E., Sharon, K., Shemmer, O., Penprase, B. E., Chevalier, R. A., Brown, P. J., Burrows, D. N., Gehrels, N., Harrison, F., Holland, S. T., Mangano, V., McCarthy, P. J., Moon, D. -S., Nousek, J. A., Persson, S. E., Piran, T., and Sari, R.
Subjects: Astrophysics
Abstract: On 2006 May 5, a four second duration, low energy, ~10^49 erg, Gamma-Ray Burst (GRB) was observed, spatially associated with a z=0.0894 galaxy. Here, we report the discovery of the GRB optical afterglow and observations of its environment using Gemini-south, Hubble Space Telescope (HST), Chandra, Swift and the Very Large Array. The optical afterglow of this GRB is spatially associated with a prominent star forming region in the Sc-type galaxy 2dFGRS S173Z112. Its proximity to a star forming region suggests that the progenitor delay time, from birth to explosion, is smaller than about 10 Myr. Our HST deep imaging rules out the presence of a supernova brighter than an absolute magnitude of about -11 (or -12.6 in case of ``maximal'' extinction) at about two weeks after the burst, and limits the ejected mass of radioactive Nickel 56 to be less than about 2x10^-4 solar mass (assuming no extinction). Although it was suggested that GRB 060505 may belong to a new class of long-duration GRBs with no supernova, we argue that the simplest interpretation is that the physical mechanism responsible for this burst is the same as for short-duration GRBs., Comment: 7 pages, 3 figures, ApJ submitted
Published: 2007
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42. The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology

Author: Chincarini, G., Moretti, A., Romano, P., Falcone, A. D., Morris, D., Racusin, J., Campana, S., Guidorzi, C., Tagliaferri, G., Burrows, D. N., Pagani, C., Stroh, M., Grupe, D., Capalbi, M., Cusumano, G., Gehrels, N., Giommi, P., La Parola, V., Mangano, V., Mineo, T., Nousek, J. A., O'Brien, P. T., Page, K. L., Perri, M., Troja, E., Willingale, R., and Zhang, B.
Subjects: Astrophysics
Abstract: We present the first systematic investigation of the morphological and timing properties of flares in GRBs observed by Swift/XRT. We consider a large sample drawn from all GRBs detected by Swift, INTEGRAL and HETE-2 prior to 2006 Jan 31, which had an XRT follow-up and which showed significant flaring. Our sample of 33 GRBs includes long and short, at low and high redshift, and a total of 69 flares. The strongest flares occur in the early phases, with a clear anti-correlation between the flare peak intensity and the flare time of occurrence. Fitting each X-ray flare with a Gaussian model, we find that the mean ratio of the width and peak time is = 0.13+/-0.10, albeit with a large scatter. Late flares at times > 2000 seconds have long durations, Delta t>300 s, and can be very energetic compared to the underlying continuum. We further investigated if there is a clear link between the number of pulses detected in the prompt phase by BAT and the number of X-ray flares detected by XRT, finding no correlation. However, we find that the distribution of intensity ratios between successive BAT prompt pulses and that between successive XRT flares is the same, an indication of a common origin for gamma-ray pulses and X-ray flares. All evidence indicates that flares are indeed related to the workings of the central engine and, within the standard fireball scenario, originate from internal shocks rather than external shocks. While all flares can be explained by long-lasting engine activity, 29/69 flares may also be explained by refreshed shocks. However, 10 can only be explained by prolonged activity of the central engine., Comment: submitted to ApJ
Published: 2007
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43. Swift multi-wavelength observations of the bright flaring burst GRB051117A

Author: Goad, M. R., Page, K. L., Godet, O., Beardmore, A., Osborne, J. P., O'Brien, P. T., Starling, R., Holland, S., Band, D., Gehrels, N., Falcone, A., Burrows, D. N., Nousek, J. A., Roming, P. W. A., Moretti, A., and Perri, M.
Subjects: Astrophysics
Abstract: We report on the temporal and spectral characteristics of the early X-ray emission from the Gamma Ray Burst 051117A as observed by Swift. The superb quality of the early X-ray light-curve and spectra of this source, one of the brightest seen by the X-ray Telescope at such early times, allows an unprecedented look at the spectral and temporal evolution of the prompt and early afterglow emission for this GRB and allows us to place stringent limits on the detection of lines. The X-ray light-curve at early times is characteristic of a shot-noise process, with individual shots well-modelled by a fast-rise and exponential decay spanning a broad range in rise-times and decay rates. A temporal spectral analysis of the early light-curve shows that the photon index and source intensity are highly correlated with the spectrum being significantly harder when brighter, consistent with the movement of the peak of the Band function to lower energies following individual flares. The high quality spectrum obtained from the first orbit of WT mode data, enables us to place a 3 sigma upper limit on the strength of any emission line features of EW < 15 eV, assuming a narrow emission-line of 100 eV at the peak of the effective area (abridged)., Comment: Accepted 15/3/2007 - To appear in A&A
Published: 2006
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44. Panchromatic study of GRB 060124: from precursor to afterglow

Author: Romano, P., Campana, S., Chincarini, G., Cummings, J., Cusumano, G., Holland, S. T., Mangano, V., Mineo, T., Page, K. L., Pal'shin, V., Rol, E., Sakamoto, T., Zhang, B., Aptekar, R., Barbier, S., Barthelmy, S., Beardmore, A. P., Boyd, P., Burrows, D. N., Capalbi, M., Fenimore, E. E., Frederiks, D., Gehrels, N., Giommi, P., Goad, M. R., Godet, O., Golenetskii, S., Guetta, D., Kennea, J. A., La Parola, V., Malesani, D., Marshall, F., Moretti, A., Nousek, J. A., O'Brien, P. T., Osborne, J. P., Perri, M., and Tagliaferri, G.
Subjects: Astrophysics
Abstract: We present observations of GRB 060124, the first event for which both the prompt and the afterglow emission could be observed simultaneously and in their entirety by the three Swift instruments and by Konus-Wind. Thanks to these exceptional circumstances, the temporal and spectral properties of the prompt emission could be studied in the optical, X-ray and gamma-ray ranges (up to 2 MeV). While the X-ray emission (0.2-10 keV) clearly tracks the gamma-ray burst, the optical component follows a different pattern, likely indicating a different origin, possibly the onset of external shocks. The prompt GRB spectrum shows significant spectral evolution, with both the peak energy and the spectral index varying. As observed in several long GRBs, significant lags are measured between the hard- and low-energy components, showing that this behaviour extends over 3 decades in energy. The GRB peaks are also much broader at soft energies. This is related to the temporal evolution of the spectrum, and can be accounted for by the softening of the electron spectral index with time. The burst energy (E_iso~5x10^{53} erg at z=2.297) and average peak energy (E_p~300 keV) make GRB 060124 consistent with the Amati relation. The X-ray afterglow is characterized by a decay which presents a break at t_b~10^5s., Comment: 4 pages, 2 figures. Proceedings of `SWIFT and GRBs: Unveiling the Relativistic Universe', June 5-9, 2006 Venice (Italy), to appear in Il Nuovo Cimento
Published: 2006
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45. Swift detects a remarkable gamma-ray burst, GRB 060614, that introduces a new classification scheme

Author: Gehrels, N., Norris, J. P., Mangano, V., Barthelmy, S. D., Burrows, D. N., Granot, J., Kaneko, Y., Kouveliotou, C., Markwardt, C. B., Meszaros, P., Nakar, E., Nousek, J. A., O'Brien, P. T., Page, M., Palmer, D. M., Parsons, A. M., Roming, P. W. A., Sakamoto, T., Sarazin, C. L., Schady, P., Stamatikos, M., and Woosley, S. E.
Subjects: Astrophysics
Abstract: Gamma ray bursts (GRBs) are known to come in two duration classes, separated at ~2 s. Long bursts originate from star forming regions in galaxies, have accompanying supernovae (SNe) when near enough to observe and are likely caused by massive-star collapsars. Recent observations show that short bursts originate in regions within their host galaxies with lower star formation rates consistent with binary neutron star (NS) or NS - black hole (BH) mergers. Moreover, although their hosts are predominantly nearby galaxies, no SNe have been so far associated with short GRBs. We report here on the bright, nearby GRB 060614 that does not fit in either class. Its ~102 s duration groups it with long GRBs, while its temporal lag and peak luminosity fall entirely within the short GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova, similar to short GRBs. This combination of a long duration event without accompanying SN poses a challenge to both a collapsar and merging NS interpretation and opens the door on a new GRB classification scheme that straddles both long and short bursts., Comment: 13 pages, 2 figures, accepted in Nature
Published: 2006
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46. Swift observations of GRB050904: the most distant cosmic explosion ever observed

Author: Cusumano, G., Mangano, V., Chincarini, G., Panaitescu, A., Burrows, D. N., La Parola, V., Sakamoto, T., Campana, S., Mineo, T., Tagliaferri, G., Angelini, L., Barthelemy, S. D., Beardmore, A. P., Boyd, P. T., Cominsky, L., Gronwall, C., Fenimore, E. E., Gehrels, N., Giommi, P., Goad, M., Hurley, K., Immler, S., Kennea, J. A., Mason, K. O., Marshall, F., Meszaros, P., Nousek, J. A., Osborne, J. P., Palmer, D. M., Roming, P. W. A., Wells, A., White, N. E., and Zhang, B.
Subjects: Astrophysics
Abstract: Swift discovered the high redshift (z=6.29) GRB050904 with the Burst Alert Telescope (BAT) and began observing with its narrow field instruments 161 s after the burst onset. This gamma-ray burst is the most distant cosmic explosion ever observed. Because of its high redshift, the X-ray Telescope (XRT) and BAT simultaneous observations provide 4 orders of magnitude of spectral coverage (0.2-150 keV; 1.4-1090 keV in the source rest frame) at a very early source-frame time (22 s). GRB050904 was a long, multi-peaked, bright GRB with strong variability during its entire evolution. The light curve observed by the XRT is characterized by the presence of a long flaring activity lasting up to 1-2 hours after the burst onset in the burst rest frame, with no evidence of a smooth power-law decay following the prompt emission as seen in other GRBs. However, the BAT tail extrapolated to the XRT band joins the XRT early light curve and the overall behavior resembles that of a very long GRB prompt. The spectral energy distribution softens with time, with the photon index decreasing from -1.2 during the BAT observation to -1.9 at the end of the XRT observation. The dips of the late X-ray flares may be consistent with an underlying X-ray emission arising from the forward shock and with the properties of the optical afterglow reported by Tagliaferri et al. (2005b). We interpret the BAT and XRT data as a single continuous observation of the prompt emission from a very long GRB. The peculiarities observed in GRB050904 could be due to its origin within one of the first star-forming regions in the Universe; very low metallicities of the progenitor at these epochs may provide an explanation., Comment: 9 pages, 2 table, 6 figures, accepted for publication on A&A
Published: 2006
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47. UVES/VLT high resolution spectroscopy of GRB 050730 afterglow: probing the features of the GRB environment

Author: D'Elia, V., Fiore, F., Meurs, E., Chincarini, G., Melandri, A., Norci, L., Pellizza, L., Perna, R., Piranomonte, S., Sbordone, L., Stella, L., Tagliaferri, G., Vergani, S., Ward, P., Angelini, L., Antonelli, L. A., Burrows, D. N., Campana, S., Capalbi, M., Caraveo, P. A., Cimatti, A., Costa, E., Cusumano, G., D'Avanzo, P., Della Valle, M., Filliatre, P., Frontera, A. Fontana F., Fugazza, D., Gehrels, N., Giannini, T., Giommi, P., Goldoni, P., Guetta, D., Israel, G., Lazzati, D., Malesani, D., Marconi, G., Mason, K., Mereghetti, S., Molinari, E., Moretti, A., Nousek, J., Perri, M., Piro, L., Stratta, G., Testa, V., and Vietri, M.
Subjects: Astrophysics
Abstract: We analyze high resolution spectroscopic observations of the optical afterglow of GRB050730, obtained with UVES@VLT about hours after the GRB trigger. The spectrum shows that the ISM of the GRB host galaxy at z = 3.967 is complex, with at least five components contributing to the main absorption system. We detect strong CII*, SiII*, OI* and FeII* fine structure absorption lines associated to the second and third component. For the first three components we derive information on the relative distance from the site of the GRB explosion. Component 1, which has the highest redshift, does not present any fine structure nor low ionization lines; it only shows very high ionization features, such as CIV and OVI, suggesting that this component is very close to the GRB site. From the analysis of low and high ionization lines and fine structure lines, we find evidences that the distance of component 2 from the site of the GRB explosion is 10-100 times smaller than that of component 3. We evaluated the mean metallicity of the z=3.967 system obtaining values about 0.01 of the solar metallicity or less. However, this should not be taken as representative of the circumburst medium, since the main contribution to the hydrogen column density comes from the outer regions of the galaxy while that of the other elements presumably comes from the ISM closer to the GRB site. Furthermore, difficulties in evaluating dust depletion correction can modify significantly these values. The mean [C/Fe] ratio agrees well with that expected by single star-formation event models. Interestingly the [C/Fe] of component 2 is smaller than that of component 3, in agreement with GRB dust destruction scenarios, if component 2 is closer than component 3 to the GRB site., Comment: 11 pages, 15 postscript figures, accepted for pubblication in A&A
Published: 2006
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48. Swift and Suzaku Observations of the X-Ray Afterglow from the GRB 060105

Author: Tashiro, M. S., Abe, K., Angelini, L., Barthelmy, S., Gehrels, N., Ishikawa, N., Kaluzienski, L. J., Kawai, N., Kelley, R. L., Kinugasa, K., Kodaira, H., Kohmura, T., Kubota, K., Maeda, Y., Maeno, S., Murakami, H., Murakami, T., Nakagawa, Y. E., Nakazawa, K., Nousek, J., Okuno, S., Onda, K., Reeves, J. N., Ricker, G., Sato, G., Sonoda, E., Suzuki, M., Takahashi, T., Tamagawa, T., Torii, K., Ueda, Y., Urata, Y., Yamaoka, K., Yamauchi, M., Yonetoku, D., Yoshida, A., and Yoshinari, S.
Subjects: Astrophysics
Abstract: Results are presented of early X-ray afterglow observations of GRB 060105 by Swift and Suzaku. The bright, long gamma-ray burst GRB 060105 triggered the Swift Burst Alert Telescope (BAT) at 06:49:28 on 5 January 2006. The Suzaku team commenced a pre-planned target of opportunity observation at 19 ks (5.3 hr) after the Swift trigger. Following the prompt emission and successive very steep decay, a shallow decay was observed from T_0+187 s to T_0+1287 s. After an observation gap during T_0 +(1.5-3) ks, an extremely early steep decay was observed in T_0+(4-30) ks. The lightcurve flattened again at T_0+30 ks, and another steep decay followed from T_0+50 ks to the end of observations. Both steep decays exhibited decay indices of 2.3 - 2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below 1 degree. The unique Suzaku/XIS data allow us to set very tight upper limits on line emission or absorption in this GRB. For the reported pseudo-redshift of z=4.0+/-1.3 the upper limit on the iron line equivalent width is 50 eV., Comment: 8 pages, 5 figures, Accepted for publication in PASJ Suzaku Special Issue (vol. 58)
Published: 2006
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49. The gamma-ray burst GRB060614 requires a novel explosive process

Author: Gal-Yam, A., Fox, D., Price, P., Davis, M., Leonard, D., Soderberg, A., Nakar, E., Ofek, E., Schmidt, B., Lewis, K., Peterson, B., Kulkarni, S., Berger, E., Cenko, B., Sari, R., Sharon, K., Frail, D., Gehrels, N., Nousek, J., Burrows, D., Mangano, V., Holland, S., Brown, P., Moon, D. -S., Harrison, F., Piran, T., McCarthy, P., Penprase, B., and Chevalier, R.
Subjects: Astrophysics
Abstract: Over the past decade our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (T < 2 s) GRBs are associated with the explosive deaths of massive stars (``collapsars''), which produce accompanying supernovae, while the short-duration (T > 2 s) GRBs arise from a different origin, which has been argued to be the merger of two compact objects, either neutron stars or black holes. Here we present observations of GRB060614, a 100-s long burst discovered by the Swift satellite, which require the invocation of a new explosive process: either a massive ``collapsar'' that powers a GRB without any associated supernova, or a new type of engine, as long-lived as the collapsar but without any such massive stellar host. We also discuss the properties of this burst's redshift z=0.125 host galaxy, which distinguish it from other long-duration GRBs and suggest that an entirely new type of GRB progenitor may be required.
Published: 2006
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50. Multi-Wavelength Observations of GRB 050820A: An Exceptionally Energetic Event Followed from Start to Finish

Author: Cenko, S. B., Kasliwal, M., Harrison, F. A., Pal'shin, V., Frail, D. A., Cameron, P. B., Berger, E., Fox, D. B., Gal-Yam, A., Kulkarni, S. R., Moon, D. -S., Nakar, E., Ofek, E. O., Penprase, B. E., Price, P. A., Sari, R., Schmidt, B. P., Soderberg, A. M., Aptekar, R., Frederiks, D., Golenetskii, S., Burrows, D. N., Chevalier, R. A., Gehrels, N., McCarthy, P. J., Nousek, J. A., Persson, S. E., and Piran, T.
Subjects: Astrophysics
Abstract: We present observations of the unusually bright and long gamma-ray burst GRB 050820A, one of the best-sampled broadband data sets in the Swift era. The gamma-ray light curve is marked by a soft precursor pulse some 200 s before the main event; the lack of any intervening emission suggests that it is due to a physical mechanism distinct from the GRB itself. The large time lag between the precursor and the main emission enabled simultaneous observations in the gamma-ray, X-ray, and optical band-passes, something only achieved for a handful of events to date. While the contemporaneous X-rays are the low-energy tail of the prompt emission, the optical does not directly track the gamma-ray flux. Instead, the early-time optical data appear mostly consistent with the forward shock synchrotron peak passing through the optical, and are therefore likely the beginning of the afterglow. On hour time scales after the burst, the X-ray and optical light curves are inconsistent with an adiabatic expansion of the shock into the surrounding region, but rather indicate that there is a period of energy injection. Observations at late times allow us to constrain the collimation angle of the relativistic outflow to theta = 6.8 - 9.3 degrees. Our estimates of both the kinetic energy of the afterglow and the prompt gamma-ray energy release make GRB 050820A one of the most energetic events for which such values could be determined., Comment: Accepted to ApJ; 18 pages, 8 figures; High resolution version available at http://www.srl.caltech.edu/~cenko/public/papers/grb050820a.ps
Published: 2006
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