Author: "Berger, E" - Searchworks@Jio Institute Digital Library Search Results

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4,573 results on '"Berger, E"'

101. The GALEX Time Domain Survey. II. Wavelength-Dependent Variability of Active Galactic Nuclei in the Pan-STARRS1 Medium Deep Survey

Author: Hung, T., Gezari, S., Jones, D. O., Kirshner, R. P., Chornock, R., Berger, E., Rest, A., Huber, M., Narayan, G., Scolnic, D., Waters, C., Wainscoat, R., Martin, D. C., Forster, K., and Neill, J. D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We analyze the wavelength-dependent variability of a sample of spectroscopically confirmed active galactic nuclei (AGN) selected from near-UV ($NUV$) variable sources in the GALEX Time Domain Survey that have a large amplitude of optical variability (difference-flux S/N $>$ 3) in the Pan-STARRS1 Medium Deep Survey (PS1 MDS). By matching GALEX and PS1 epochs in 5 bands ($NUV$, $g_{P1}$, $r_{P1}$, $i_{P1}$, $z_{P1}$) in time, and taking their flux difference, we create co-temporal difference-flux spectral energy distributions ($\Delta f$SEDs) using two chosen epochs for each of the 23 objects in our sample on timescales of about a year. We confirm the "bluer-when-brighter" trend reported in previous studies, and measure a median spectral index of the $\Delta f$SEDs of $\alpha_{\lambda}$ = 2.1 that is consistent with an accretion disk spectrum. We further fit the $\Delta f$SEDs of each source with a standard accretion disk model in which the accretion rate changes from one epoch to the other. In our sample, 17 out of 23 ($\sim$74 %) sources are well described by this variable accretion-rate disk model, with a median average characteristic disk temperature $\bar{T}^*$ of $1.2\times 10^5$~K that is consistent with the temperatures expected given the distribution of accretion rates and black hole masses inferred for the sample. Our analysis also shows that the variable accretion rate model is a better fit to the $\Delta f$SEDs than a simple power law., Comment: 16 pages, 11 figures, Accepted for publication in The Astrophysical Journal September, 20, 2016
Published: 2016
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102. Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5

Author: Williams, P. K. G., Gizis, J. E., and Berger, E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Route & Wolszczan (2016) recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ~17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission possibly with a period of 116 minutes, although our observation lasted only 162 minutes and so more data are needed to confirm it. Our proposed periodicity is typical of other radio-active ultracool dwarfs. The handedness of the circular polarization alternates with time and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object's magnetic dipole axis may be highly misaligned relative to its rotation axis., Comment: 9 pages, 5 figures, AAS submitted
Published: 2016
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103. Superluminous supernova 2015bn in the nebular phase: evidence for the engine-powered explosion of a stripped massive star

Author: Nicholl, M., Berger, E., Margutti, R., Chornock, R., Blanchard, P. K., Jerkstrand, A., Smartt, S. J., Arcavi, I., Challis, P., Chambers, K. C., Chen, T. -W., Cowperthwaite, P. . S., Gal-Yam, A., Hosseinzadeh, G., Howell, D. A., Inserra, C., Kankare, E., Magnier, E. A., Maguire, K., Mazzali, P. A., McCully, C., Milisavljevic, D., Smith, K. W., Taubenberger, S., Valenti, S., Wainscoat, R. J., Yaron, O., and Young, D. R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova SN 2015bn, at redshift z=0.1136, spanning +250-400 d after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag/(100 d) to 1.7 mag/(100 d), suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium and magnesium. There are no obvious signatures of circumstellar interaction or large nickel mass. We show that the spectrum at +400 d is virtually identical to a number of energetic Type Ic supernovae such as SN 1997dq, SN 2012au, and SN 1998bw, indicating similar core conditions and strengthening the link between `hypernovae'/long gamma-ray bursts and superluminous supernovae. A single explosion mechanism may unify these events that span absolute magnitudes of -22 < M_B < -17. Both the light curve and spectrum of SN 2015bn are consistent with an engine-driven explosion ejecting 7-30 M$_\odot$ of oxygen-dominated ejecta (for reasonable choices in temperature and opacity). A strong and relatively narrow O II $\lambda$7774 line, seen in a number of these energetic events but not in normal supernovae, may point to an inner shell that is the signature of a central engine., Comment: Updated to match published version
Published: 2016
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104. A DECam Search for an Optical Counterpart to the LIGO Gravitational Wave Event GW151226

Author: Cowperthwaite, P. S., Berger, E., Soares-Santos, M., Annis, J., Brout, D., Brown, D. A., Buckley-Geer, E., Cenko, S. B., Chen, H. Y., Chornock, R., Diehl, H. T., Doctor, Z., Drlica-Wagner, A., Drout, M. R., Farr, B., Finley, D. A., Foley, R. J., Fong, W., Fox, D. B., Frieman, J., Garcia-Bellido, J., Gill, M. S. S., Gruendl, R. A., Herner, K., Holz, D. E., Kasen, D., Kessler, R., Lin, H., Margutti, R., Marriner, J., Matheson, T., Metzger, B. D., Neilsen Jr., E. H., Quataert, E., Rest, A., Sako, M., Scolnic, D., Smith, N., Sobreira, F., Strampelli, G. M., Villar, V. A., Walker, A. R., Wester, W., Williams, P. K. G., Yanny, B., Abbott, T. M. C., Abdalla, F. B., Allam, S., Armstrong, R., Bechtol, K., Benoit-Levy, A., Bertin, E., Brooks, D., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Castander, F. J., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Desai, S., Dietrich, J. P., Evrard, A. E., Neto, A. Fausti, Fosalba, P., Gerdes, D. W., Giannantonio, T., Goldstein, D. A., Gruen, D., Gutierrez, G., Honscheid, K., James, D. J., Johnson, M. W. G., Johnson, M. D., Krause, E., Kuehn, K., Kuropatkin, N., Lima, M., Maia, M. A. G., Marshall, J. L., Menanteau, F., Miquel, R., Mohr, J. J., Nichol, R. C., Nord, B., Ogando, R., Plazas, A. A., Reil, K., Romer, A. K., Sanchez, E., Scarpine, V., Sevilla-Noarbe, I., Smith, R. C., Suchyta, E., Tarle, G., Thomas, D., Thomas, R. C., Tucker, D. L., and Weller, J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We report the results of a Dark Energy Camera (DECam) optical follow-up of the gravitational wave (GW) event GW151226, discovered by the Advanced LIGO detectors. Our observations cover 28.8 deg$^2$ of the localization region in the $i$ and $z$ bands (containing 3% of the BAYESTAR localization probability), starting 10 hours after the event was announced and spanning four epochs at $2-24$ days after the GW detection. We achieve $5\sigma$ point-source limiting magnitudes of $i\approx21.7$ and $z\approx21.5$, with a scatter of $0.4$ mag, in our difference images. Given the two day delay, we search this area for a rapidly declining optical counterpart with $\gtrsim 3\sigma$ significance steady decline between the first and final observations. We recover four sources that pass our selection criteria, of which three are cataloged AGN. The fourth source is offset by $5.8$ arcsec from the center of a galaxy at a distance of 187 Mpc, exhibits a rapid decline by $0.5$ mag over $4$ days, and has a red color of $i-z\approx 0.3$ mag. These properties roughly match the expectations for a kilonova. However, this source was detected several times, starting $94$ days prior to GW151226, in the Pan-STARRS Survey for Transients (dubbed as PS15cdi) and is therefore unrelated to the GW event. Given its long-term behavior, PS15cdi is likely a Type IIP supernova that transitioned out of its plateau phase during our observations, mimicking a kilonova-like behavior. We comment on the implications of this detection for contamination in future optical follow-up observations., Comment: 7 Pages, 2 Figures, 1 Table. Accepted to ApJL, updated to better match published version
Published: 2016
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105. PS1-14bj: A Hydrogen-Poor Superluminous Supernova With a Long Rise and Slow Decay

Author: Lunnan, R., Chornock, R., Berger, E., Milisavljevic, D., Jones, D. O., Rest, A., Fong, W., Fransson, C., Margutti, R., Drout, M. R., Blanchard, P. K., Challis, P., Cowperthwaite, P. S., Foley, R. J., Kirshner, R. P., Morrell, N., Riess, A. G., Roth, K. C., Scolnic, D., Smartt, S. J., Smith, K. W., Villar, V. A., Chambers, K. C., Draper, P. W., Huber, M. E., Kaiser, N., Kudritzki, R. -P., Magnier, E. A., Metcalfe, N., and Waters, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present photometry and spectroscopy of PS1-14bj, a hydrogen-poor superluminous supernova (SLSN) at redshift $z=0.5215$ discovered in the last months of the Pan-STARRS1 Medium Deep Survey. PS1-14bj stands out by its extremely slow evolution, with an observed rise of $\gtrsim 125$ rest-frame days, and exponential decline out to $\sim 250$ days past peak at a measured rate of $0.01~{\rm mag~day}^{-1}$, consistent with fully-trapped $^{56}$Co decay. This is the longest rise time measured in a SLSN to date, and the first SLSN to show a rise time consistent with pair-instability supernova (PISN) models. Compared to other slowly-evolving SLSNe, it is spectroscopically similar to the prototype SN2007bi at maximum light, though lower in luminosity ($L_{\rm peak} \simeq 4.6 \times 10^{43} {\rm erg s}^{-1}$) and with a flatter peak than previous events. PS1-14bj shows a number of peculiar properties, including a near-constant color temperature for $>200$ days past peak, and strong emission lines from [O III] $\lambda$5007 and [O III] $\lambda$4363 with a velocity width of $\sim$3400 km/s, in its late-time spectra. These both suggest there is a sustained source of heating over very long timescales, and are incompatible with a simple $^{56}$Ni-powered/PISN interpretation. A modified magnetar model including emission leakage at late times can reproduce the light curve, in which case the blue continuum and [O III] features are interpreted as material heated and ionized by the inner pulsar wind nebula becoming visible at late times. Alternatively, the late-time heating could be due to interaction with a shell of H-poor circumstellar material., Comment: Accepted by ApJ August 25, 2016. Minor changes following referee report; conclusions unchanged
Published: 2016
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106. 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. 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. C., Ferrini, F., Fidecaro, F., Fiori, I., Fiorucci, D., Fisher, R. P., Flaminio, R., Fletcher, M., Fournier, J. -D., Franco, S., Frasca, S., Frasconi, F., Frei, Z., Freise, A., Frey, R., Frey, V., Fricke, T. T., Fritschel, P., Frolov, V. V., Fulda, P., Fyffe, M., Gabbard, H. A. G., Gair, J. R., Gammaitoni, L., Gaonkar, S. G., Garufi, F., Gatto, A., Gaur, G., Gehrels, N., Gemme, G., Gendre, B., Genin, E., Gennai, A., George, J., Gergely, L., Germain, V., Ghosh, A., Ghosh, S., Giaime, J. A., Giardina, K. D., Giazotto, A., Gill, K., Glaefke, A., Goetz, E., Goetz, R., Gondan, L., González, G., Castro, J. M. G., Gopakumar, A., Gordon, N. A., Gorodetsky, M. L., Gossan, S. E., Gosselin, M., Gouaty, R., Graef, C., Graff, P. B., Granata, M., Grant, A., Gras, S., Gray, C., Greco, G., Green, A. C., Groot, P., Grote, H., Grunewald, S., Guidi, G. M., Guo, X., Gupta, A., Gupta, M. K., Gushwa, K. E., Gustafson, E. K., Gustafson, R., Hacker, J. J., Hall, B. R., Hall, E. D., Hammond, G., Haney, M., Hanke, M. M., Hanks, J., Hanna, C., Hannam, M. D., Hanson, J., Hardwick, T., Haris, K., Harms, J., Harry, G. M., Harry, I. W., Hart, M. J., Hartman, M. T., Haster, C. -J., Haughian, K., Heidmann, A., Heintze, M. C., Heitmann, H., Hello, P., Hemming, G., Hendry, M., Heng, I. S., Hennig, J., Heptonstall, A. W., Heurs, M., Hild, S., Hoak, D., Hodge, K. A., Hofman, D., Hollitt, S. E., Holt, K., Holz, D. E., Hopkins, P., Hosken, D. J., Hough, J., Houston, E. A., Howell, E. J., Hu, Y. M., Huang, S., Huerta, E. A., Huet, D., Hughey, B., Husa, S., Huttner, S. H., Huynh-Dinh, T., Idrisy, A., Indik, N., Ingram, D. R., Inta, R., Isa, H. N., Isac, J. -M., Isi, M., Islas, G., Isogai, T., Iyer, B. R., Izumi, K., Jacqmin, T., Jang, H., Jani, K., Jaranowski, P., Jawahar, S., Jiménez-Forteza, F., Johnson, W. W., Jones, D. I., Jones, R., Jonker, R. J. G., Ju, L., Kalaghatgi, C. V., Kalogera, V., Kandhasamy, S., Kang, G., Kanner, J. B., Karki, S., Kasprzack, M., Katsavounidis, E., Katzman, W., Kaufer, S., Kaur, T., Kawabe, K., Kawazoe, F., Kéfélian, F., Kehl, M. S., Keitel, D., Kelley, D. B., Kells, W., Kennedy, R., Key, J. S., Khalaidovski, A., Khalili, F. Y., Khan, I., Khan, S., Khan, Z., Khazanov, E. A., Kijbunchoo, N., Kim, C., Kim, J., Kim, K., Kim, N., Kim, Y. -M., King, E. J., King, P. J., Kinzel, D. L., Kissel, J. S., Kleybolte, L., Klimenko, S., Koehlenbeck, S. M., Kokeyama, K., Koley, S., Kondrashov, V., Kontos, A., Korobko, M., Korth, W. Z., Kowalska, I., Kozak, D. B., Kringel, V., Królak, A., Krueger, C., Kuehn, G., Kumar, P., Kuo, L., Kutynia, A., Lackey, B. D., Landry, M., Lange, J., Lantz, B., Lasky, P. D., Lazzarini, A., Lazzaro, C., Leaci, P., Leavey, S., Lebigot, E. O., Lee, C. H., Lee, H. K., Lee, H. M., Lee, K., Lenon, A., Leonardi, M., Leong, J. R., Leroy, N., Letendre, N., Levin, Y., Levine, B. M., Li, T. G. F., Libson, A., Littenberg, T. B., Lockerbie, N. A., Logue, J., Lombardi, A. L., Lord, J. E., Lorenzini, M., Loriette, V., Lormand, M., Losurdo, G., Lough, J. D., Lück, H., Lundgren, A. P., Luo, J., Lynch, R., Ma, Y., MacDonald, T., Machenschalk, B., MacInnis, M., Macleod, D. M., Magaña-Sandoval, F., Magee, R. M., Mageswaran, M., Majorana, E., Maksimovic, I., Malvezzi, V., Man, N., Mandel, I., Mandic, V., Mangano, V., Mansell, G. L., Manske, M., Mantovani, M., Marchesoni, F., Marion, F., Márka, S., Márka, Z., Markosyan, A. S., Maros, E., Martelli, F., Martellini, L., Martin, I. W., Martin, R. M., Martynov, D. V., Marx, J. N., Mason, K., Masserot, A., Massinger, T. J., Masso-Reid, M., Matichard, F., Matone, L., Mavalvala, N., Mazumder, N., Mazzolo, G., McCarthy, R., McClelland, D. E., McCormick, S., McGuire, S. C., McIntyre, G., McIver, J., McManus, D. J., McWilliams, S. T., Meacher, D., Meadors, G. D., Meidam, J., Melatos, A., Mendell, G., Mendoza-Gandara, D., Mercer, R. A., Merilh, E., Merzougui, M., Meshkov, S., Messenger, C., Messick, C., Meyers, P. M., Mezzani, F., Miao, H., Michel, C., Middleton, H., Mikhailov, E. E., Milano, L., Miller, J., Millhouse, M., Minenkov, Y., Ming, J., Mirshekari, S., Mishra, C., Mitra, S., Mitrofanov, V. P., Mitselmakher, G., Mittleman, R., Moggi, A., Mohan, M., Mohapatra, S. R. P., Montani, M., Moore, B. C., Moore, C. J., Moraru, D., Moreno, G., Morriss, S. R., Mossavi, K., Mours, B., Mow-Lowry, C. M., Mueller, C. L., Mueller, G., Muir, A. W., Mukherjee, A., Mukherjee, D., Mukherjee, S., Mukund, N., Mullavey, A., Munch, J., Murphy, D. J., Murray, P. G., Mytidis, A., Nardecchia, I., Naticchioni, L., Nayak, R. K., Necula, V., Nedkova, K., Nelemans, G., Neri, M., Neunzert, A., Newton, G., Nguyen, T. T., Nielsen, A. B., Nissanke, S., Nitz, A., Nocera, F., Nolting, D., Normandin, M. E. N., Nuttall, L. K., Oberling, J., Ochsner, E., O'Dell, J., Oelker, E., Ogin, G. H., Oh, J. J., Oh, S. H., Ohme, F., Oliver, M., Oppermann, P., Oram, R. J., O'Reilly, B., O'Shaughnessy, R., Ottaway, D. J., Ottens, R. S., Overmier, H., Owen, B. J., Pai, A., Pai, S. A., Palamos, J. R., Palashov, O., Palliyaguru, N., Palomba, C., Pal-Singh, A., Pan, H., Pankow, C., Pannarale, F., Pant, B. C., Paoletti, F., Paoli, A., Papa, M. A., Paris, H. R., Parker, W., Pascucci, D., Pasqualetti, A., Passaquieti, R., Passuello, D., Patricelli, B., Patrick, Z., Pearlstone, B. L., Pedraza, M., Pedurand, R., Pekowsky, L., Pele, A., Penn, S., Perreca, A., Phelps, M., Piccinni, O., Pichot, M., Piergiovanni, F., Pierro, V., Pillant, G., Pinard, L., Pinto, I. M., Pitkin, M., Poggiani, R., Popolizio, P., Post, A., Powell, J., Prasad, J., Predoi, V., Premachandra, S. S., Prestegard, T., Price, L. R., Prijatelj, M., Principe, M., Privitera, S., Prodi, G. A., Prokhorov, L., Puncken, O., Punturo, M., Puppo, P., Pürrer, M., Qi, H., Qin, J., Quetschke, V., Quintero, E. A., Quitzow-James, R., Raab, F. J., Rabeling, D. 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. 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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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107. SN 2015bn: a detailed multi-wavelength view of a nearby superluminous supernova

Author: Nicholl, M., Berger, E., Smartt, S. J., Margutti, R., Kamble, A., Alexander, K. D., Chen, T. -W., Inserra, C., Arcavi, I., Blanchard, P. K., Cartier, R., Chambers, K. C., Childress, M. J., Chornock, R., Cowperthwaite, P. S., Drout, M., Flewelling, H. A., Fraser, M., Gal-Yam, A., Galbany, L., Harmanen, J., Holoien, T. W. -S., Hosseinzadeh, G., Howell, D. A., Huber, M. E., Jerkstrand, A., Kankare, E., Kochanek, C. S., Lin, Z. -Y., Lunnan, R., Magnier, E. A., Maguire, K., McCully, C., McDonald, M., Metzger, B. D., Milisavljevic, D., Mitra, A., Reynolds, T., Saario, J., Shappee, B. J., Smith, K. W., Valenti, S., Villar, V. A., Waters, C., and Young, D. R.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift $z=0.1136$. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter ($M_U\approx-23.1$) and in a fainter galaxy ($M_B\approx-16.0$) than other SLSNe at $z\sim0.1$. We used this opportunity to collect the most extensive dataset for any SLSN I to date, including densely-sampled spectroscopy and photometry, from the UV to the NIR, spanning $-$50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits surprising undulations in the light curve on a timescale of 30-50 days, especially in the UV. The spectrum shows extraordinarily slow evolution except for a rapid transformation between +7 and +20-30 days. No narrow emission lines from slow-moving material are observed at any phase. We derive physical properties including the bolometric luminosity, and find slow velocity evolution and non-monotonic temperature and radial evolution. A deep radio limit rules out a healthy off-axis gamma-ray burst, and places constraints on the pre-explosion mass loss. The data can be consistently explained by a $\gtrsim10\,{\rm M}_\odot$ stripped progenitor exploding with $\sim 10^{51}\,$erg kinetic energy, forming a magnetar with a spin-down timescale of $\sim20$ days (thus avoiding a gamma-ray burst) that reheats the ejecta and drives ionization fronts. The most likely alternative scenario -- interaction with $\sim20\,{\rm M}_\odot$ of dense, inhomogeneous circumstellar material -- can be tested with continuing radio follow-up., Comment: Slightly updated to match published version
Published: 2016
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108. 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. 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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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109. No precise localization for FRB 150418: claimed radio transient is AGN variability

Author: Williams, P. K. G. and Berger, E.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Keane et al. have recently claimed to have obtained the first precise localization for a Fast Radio Burst (FRB) thanks to the identification of a contemporaneous fading slow (~week-timescale) radio transient. They use this localization to pinpoint the FRB to a galaxy at z ~ 0.49 that exhibits no discernable star formation activity. We argue that the transient is not genuine and that the host candidate, WISE J071634.59-190039.2, is instead a radio variable: the available data did not exclude this possibility; a random radio variable consistent with the observations is not unlikely to have a redshift compatible with the FRB dispersion measure; and the proposed transient light curve is better explained as a scintillating steady source, perhaps also showing an active galactic nucleus (AGN) flare, than a synchrotron-emitting blastwave. The radio luminosity of the host candidate implies that it is an AGN and we present new late-time Very Large Array observations showing that the galaxy is indeed variable at a level consistent with the claimed transient. Therefore the claimed precise localization and redshift determination for FRB 150418 cannot be justified., Comment: ApJL in press; 7 pages, 3 figures, 2 tables. v2: resubmitted version; v1 was an early arxiv-only note
Published: 2016
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110. A Dark Energy Camera Search for an Optical Counterpart to the First Advanced LIGO Gravitational Wave Event GW150914

Author: Soares-Santos, M., Kessler, R., Berger, E., Annis, J., Brout, D., Buckley-Geer, E., Chen, H., Cowperthwaite, P. S., Diehl, H. T., Doctor, Z., Drlica-Wagner, A., Farr, B., Finley, D. A., Flaugher, B., Foley, R. J., Frieman, J., Gruendl, R. A., Herner, K., Holz, D., Lin, H., Marriner, J., Neilsen, E., Rest, A., Sako, M., Scolnic, D., Sobreira, F., Walker, A. R., Wester, W., Yanny, B., Abbott, T. M. C., Abdalla, F. B., Allam, S., Armstrong, R., Banerji, M., Benoit-Lévy, A., Bernstein, R. A., Bertin, E., Brown, D. A., Burke, D. L., Capozzi, D., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Castander, F. J., Cenko, S. B., Chornock, R., Crocce, M., D'Andrea, C. B., da Costa, L. N., Desai, S., Dietrich, J. P., Drout, M. R., Eifler, T. F., Estrada, J., Evrard, A. E., Fairhurst, S., Fernandez, E., Fischer, J., Fong, W., Fosalba, P., Fox, D. B., Fryer, C. L., Garcia-Bellido, J., Gaztanaga, E., Gerdes, D. W., Goldstein, D. A., Gruen, D., Gutierrez, G., Honscheid, K., James, D. J., Karliner, I., Kasen, D., Kent, S., Kuropatkin, N., Kuehn, K., Lahav, O., Li, T. S., Lima, M., Maia, M. A. G., Margutti, R., Martini, P., Matheson, T., McMahon, R. G., Metzger, B. D., Miller, C. J., Miquel, R., Mohr, J. J., Nichol, R. C., Nord, B., Ogando, R., Peoples, J., Plazas, A. A., Quataert, E., Romer, A. K., Roodman, A., Rykoff, E. S., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Sheldon, E., Smith, M., Smith, N., Smith, R. C., Stebbins, A., Sutton, P. J., Swanson, M. E. C., Tarle, G., Thaler, J., Thomas, R. C., Tucker, D. L., Vikram, V., Wechsler, R. H., and Weller, J.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We report initial results of a deep search for an optical counterpart to the gravitational wave event GW150914, the first trigger from the Advanced LIGO gravitational wave detectors. We used the Dark Energy Camera (DECam) to image a 102 deg$^2$ area, corresponding to 38% of the initial trigger high-probability sky region and to 11% of the revised high-probability region. We observed in i and z bands at 4-5, 7, and 24 days after the trigger. The median $5\sigma$ point-source limiting magnitudes of our search images are i=22.5 and z=21.8 mag. We processed the images through a difference-imaging pipeline using templates from pre-existing Dark Energy Survey data and publicly available DECam data. Due to missing template observations and other losses, our effective search area subtends 40 deg$^{2}$, corresponding to 12% total probability in the initial map and 3% of the final map. In this area, we search for objects that decline significantly between days 4-5 and day 7, and are undetectable by day 24, finding none to typical magnitude limits of i= 21.5,21.1,20.1 for object colors (i-z)=1,0,-1, respectively. Our search demonstrates the feasibility of a dedicated search program with DECam and bodes well for future research in this emerging field., Comment: 6 pages, 1 figure. Updated references. Submitted to ApJL
Published: 2016
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111. A Dark Energy Camera Search for Missing Supergiants in the LMC After the Advanced LIGO Gravitational Wave Event GW150914

Author: Annis, J., Soares-Santos, M., Berger, E., Brout, D., Chen, H., Chornock, R., Cowperthwaite, P. S., Diehl, H. T., Doctor, Z., Drlica-Wagner, A., Drout, M. R., Farr, B., Finley, D. A., Flaugher, B., Foley, R. J., Frieman, J., Gruendl, R. A., Herner, K., Holz, D., Kessler, R., Lin, H., Marriner, J., Neilsen, E., Rest, A., Sako, M., Smith, M., Smith, N., Sobreira, F., Walker, A. R., Yanny, B., Abbott, T. M. C., Abdalla, F. B., Allam, S., Benoit-Levy, A., Bernstein, R. A., Bertin, E., Buckley-Geer, E., Burke, D. L., Capozzi, D., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Castander, F. J., Cenko, S. B., Crocce, M., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Desai, S., Dietrich, J. P., Eifler, T. F., Evrard, A. E., Fernandez, E., Fischer, J., Fong, W., Fosalba, P., Fox, D. B., Fryer, C. L., Garcia-Bellido, J., Gaztanaga, E., Gerdes, D. W., Goldstein, D. A., Gruen, D., Gutierrez, G., Honscheid, K., James, D. J., Karliner, I., Kasen, D., Kent, S., Kuehn, K., Kuropatkin, N., Lahav, O., Li, T. S., Lima, M., Maia, M. A. G., Martini, P., Metzger, B. D., Miller, C. J., Miquel, R., Mohr, J. J., Nichol, R. C., Nord, B., Ogando, R., Peoples, J., Plazas, A. A., Quataert, E., Romer, A. K., Roodman, A., Rykoff, E. S., Sanchez, E., Santiago, B., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Sheldon, E., Smith, R. C., Stebbins, A., Swanson, M. E. C., Tarle, G., Thaler, J., Thomas, R. C., Tucker, D. L., Vikram, V., Wechsler, R. H., Weller, J., and Wester, W.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The collapse of the core of a star is expected to produce gravitational radiation. While this process will usually produce a luminous supernova, the optical signatue could be subluminous and a direct collapse to a black hole, with the star just disappearing, is possible. The gravitational wave event GW150914 reported by the LIGO Virgo Collaboration (LVC) on 2015 September 16, was detected by a burst analysis and whose high probability spatial localization included the Large Magellanic Cloud. Shortly after the announcement of the event, we used the Dark Energy Camera to observe 102 deg$^2$ of the localization area, including a 38 deg$^2$ area centered on the LMC. Using a catalog of 152 LMC luminous red supergiants, candidates to undergo a core collapse without a visible supernova, we find that the positions of 144 of these are inside our images, and that all are detected - none have disappeared. There are other classes of candidates: we searched existing catalogs of red supergiants, yellow supergiants, Wolf-Rayet stars, and luminous blue variable stars, recovering all that were inside the imaging area. Based on our observations, we conclude that it is unlikely that GW150914 was caused by the core collapse of a supergiant in the LMC, consistent with the LIGO Collaboration analyses of the gravitational wave form as best described by a binary black hole merger. We discuss how to generalize this search for future very nearby core collapse candidates., Comment: 6 pages, 3 figures, as submitted
Published: 2016
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112. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South

Author: Chornock, R, Berger, E, Kasen, D, Cowperthwaite, PS, Nicholl, M, Villar, VA, Alexander, KD, Blanchard, PK, Eftekhari, T, Fong, W, Margutti, R, Williams, PKG, Annis, J, Brout, D, Brown, DA, Chen, H-Y, Drout, MR, Farr, B, Foley, RJ, Frieman, JA, Fryer, CL, Herner, K, Holz, DE, Kessler, R, Matheson, T, Metzger, BD, Quataert, E, Rest, A, Sako, M, Scolnic, DM, Smith, N, and Soares-Santos, M
Subjects: binaries: close, nuclear reactions, nucleosynthesis, abundances, stars: neutron, astro-ph.HE, astro-ph.GA, astro-ph.SR, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract: We present a near-infrared spectral sequence of the electromagnetic counterpart to the binary neutron star merger GW170817 detected by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo. Our data set comprises seven epochs of J+H spectra taken with FLAMINGOS-2 on Gemini-South between 1.5 and 10.5 days after the merger. In the initial epoch, the spectrum is dominated by a smooth blue continuum due to a high-velocity, lanthanide-poor blue kilonova component. Starting the following night, all of the subsequent spectra instead show features that are similar to those predicted in model spectra of material with a high concentration of lanthanides, including spectral peaks near 1.07 and 1.55 μm. Our fiducial model with 0.04 M o of ejecta, an ejection velocity of v = 0.1c, and a lanthanide concentration of X lan = 10-2 provides a good match to the spectra taken in the first five days, although it over-predicts the late-time fluxes. We also explore models with multiple fitting components, in each case finding that a significant abundance of lanthanide elements is necessary to match the broad spectral peaks that we observe starting at 2.5 days after the merger. These data provide direct evidence that binary neutron star mergers are significant production sites of even the heaviest r-process elements.
Published: 2017

113. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models

Author: Cowperthwaite, PS, Berger, E, Villar, VA, Metzger, BD, Nicholl, M, Chornock, R, Blanchard, PK, Fong, W, Margutti, R, Soares-Santos, M, Alexander, KD, Allam, S, Annis, J, Brout, D, Brown, DA, Butler, RE, Chen, H-Y, Diehl, HT, Doctor, Z, Drout, MR, Eftekhari, T, Farr, B, Finley, DA, Foley, RJ, Frieman, JA, Fryer, CL, García-Bellido, J, Gill, MSS, Guillochon, J, Herner, K, Holz, DE, Kasen, D, Kessler, R, Marriner, J, Matheson, T, Neilsen, EH, Quataert, E, Palmese, A, Rest, A, Sako, M, Scolnic, DM, Smith, N, Tucker, DL, Williams, PKG, Balbinot, E, Carlin, JL, Cook, ER, Durret, F, Li, TS, Lopes, PAA, Lourenço, ACC, Marshall, JL, Medina, GE, Muir, J, Muñoz, RR, Sauseda, M, Schlegel, DJ, Secco, LF, Vivas, AK, Wester, W, Zenteno, A, Zhang, Y, Abbott, TMC, Banerji, M, Bechtol, K, Benoit-Lévy, A, Bertin, E, Buckley-Geer, E, Burke, DL, Capozzi, D, Rosell, A Carnero, Kind, M Carrasco, Castander, FJ, Crocce, M, Cunha, CE, D’Andrea, CB, da Costa, LN, Davis, C, DePoy, DL, Desai, S, Dietrich, JP, Drlica-Wagner, A, Eifler, TF, Evrard, AE, Fernandez, E, Flaugher, B, Fosalba, P, Gaztanaga, E, Gerdes, DW, Giannantonio, T, Goldstein, DA, Gruen, D, Gruendl, RA, Gutierrez, G, Honscheid, K, Jain, B, James, DJ, Jeltema, T, Johnson, MWG, and Johnson, MD
Subjects: Space Sciences, Astronomical Sciences, Physical Sciences, binaries: close, catalogs, gravitational waves, stars: neutron, surveys, astro-ph.HE, Astronomical and Space Sciences, Astronomy & Astrophysics, Astronomical sciences, Space sciences
Abstract: We present UV, optical, and near-infrared (NIR) photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at 0.47-18.5 days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2 (GS/F2), and the Hubble Space Telescope (HST). The spectral energy distribution (SED) inferred from this photometry at 0.6 days is well described by a blackbody model with T ≈ 8300 K, a radius of R ≈ 4.5 × 1014cm (corresponding to an expansion velocity of v ≈ 0.3c), and a bolometric luminosity of Lbol ≈ 5 × 1041 erg s-1. At 1.5 days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/NIR colors. Modeling the entire data set, we find that models with heating from radioactive decay of 56Ni, or those with only a single component of opacity from r-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data; the resulting "blue" component has Mblueej 0.1 M⊙ and vblueej ≈ 0.3c, and the "red" component has and Mredej ≈ 0.04 M⊙ and vredej ≈ 0.1 c. These ejecta masses are broadly consistent with the estimated r-process production rate required to explain the Milky Way r-process abundances, providing the first evidence that binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.
Published: 2017

114. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera

Author: Soares-Santos, M, Holz, DE, Annis, J, Chornock, R, Herner, K, Berger, E, Brout, D, Chen, H-Y, Kessler, R, Sako, M, Allam, S, Tucker, DL, Butler, RE, Palmese, A, Doctor, Z, Diehl, HT, Frieman, J, Yanny, B, Lin, H, Scolnic, D, Cowperthwaite, P, Neilsen, E, Marriner, J, Kuropatkin, N, Hartley, WG, Paz-Chinchón, F, Alexander, KD, Balbinot, E, Blanchard, P, Brown, DA, Carlin, JL, Conselice, C, Cook, ER, Drlica-Wagner, A, Drout, MR, Durret, F, Eftekhari, T, Farr, B, Finley, DA, Foley, RJ, Fong, W, Fryer, CL, García-Bellido, J, Gill, MSS, Gruendl, RA, Hanna, C, Kasen, D, Li, TS, Lopes, PAA, Lourenço, ACC, Margutti, R, Marshall, JL, Matheson, T, Medina, GE, Metzger, BD, Muñoz, RR, Muir, J, Nicholl, M, Quataert, E, Rest, A, Sauseda, M, Schlegel, DJ, Secco, LF, Sobreira, F, Stebbins, A, Villar, VA, Vivas, K, Walker, AR, Wester, W, Williams, PKG, Zenteno, A, Zhang, Y, Abbott, TMC, Abdalla, FB, Banerji, M, Bechtol, K, Benoit-Lévy, A, Bertin, E, Brooks, D, Buckley-Geer, E, Burke, DL, Rosell, A Carnero, Kind, M Carrasco, Carretero, J, Castander, FJ, Crocce, M, Cunha, CE, D’Andrea, CB, da Costa, LN, Davis, C, Desai, S, Dietrich, JP, Doel, P, Eifler, TF, Fernandez, E, Flaugher, B, Fosalba, P, Gaztanaga, E, Gerdes, DW, and Giannantonio, T
Subjects: binaries: close, catalogs, gravitational waves, stars: neutron, surveys, astro-ph.HE, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract: We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5 hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hr post-merger we detected a bright optical transient located from the nucleus of NGC 4993 at redshift z = 0.0098, consistent (for km s-1 Mpc-1) with the distance of 40 ±8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of and , and thus an absolute magnitude of , in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.
Published: 2017

115. X-Rays from the Location of the Double-humped Transient ASASSN-15lh

Author: Margutti, R, Metzger, BD, Chornock, R, Milisavljevic, D, Berger, E, Blanchard, PK, Guidorzi, C, Migliori, G, Kamble, A, Lunnan, R, Nicholl, M, Coppejans, DL, Dall'Osso, S, Drout, MR, Perna, R, and Sbarufatti, B
Subjects: supernovae: individual, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract: We present the detection of persistent soft X-ray radiation with Lx ~ 1041-1042 erg s-1 at the location of the extremely luminous, double-humped transient ASASSN-15lh as revealed by Chandra and Swift. We interpret this finding in the context of observations from our multiwavelength campaign, which revealed the presence of weak narrow nebular emission features from the host-galaxy nucleus and clear differences with respect to superluminous supernova optical spectra. Significant UV flux variability on short timescales detected at the time of the rebrightening disfavors the shock interaction scenario as the source of energy powering the long-lived UV emission, while deep radio limits exclude the presence of relativistic jets propagating into a low-density environment. We propose a model where the extreme luminosity and double-peaked temporal structure of ASASSN-15lh is powered by a central source of ionizing radiation that produces a sudden change in the ejecta opacity at later times. As a result, UV radiation can more easily escape, producing the second bump in the light curve. We discuss different interpretations for the intrinsic nature of the ionizing source. We conclude that, if the X-ray source is physically associated with the optical-UV transient, then ASASSN-15lh most likely represents the tidal disruption of a main-sequence star by the most massive spinning black hole detected to date. In this case, ASASSN-15lh and similar events discovered in the future would constitute the most direct probes of very massive, dormant, spinning, supermassive black holes in galaxies. Future monitoring of the X-rays may allow us to distinguish between the supernova hypothesis and the hypothesis of a tidal disruption event.
Published: 2017

116. Navigating school belonging in Qatari schools: A mixed-methods study of student perspectives

Author: Allen, K-A, McCarthy, S, Sawalhi, R, Berger, E, May, F, Patlamazoglou, L, Gamble, N, Grove, C, Wurf, G, Arango, EJ, Warton, W, Reupert, A, Allen, K-A, McCarthy, S, Sawalhi, R, Berger, E, May, F, Patlamazoglou, L, Gamble, N, Grove, C, Wurf, G, Arango, EJ, Warton, W, and Reupert, A
Abstract: A sense of school belonging is essential for adolescent development, though there is limited research investigating ways to improve students' sense of school belonging in Qatar. With 116 Qatari secondary school students, the current study explored student perspectives of ways teachers and schools could improve their sense of school belonging. Students responded to a survey including open‐ended questions and a descriptive scale measuring the usefulness of established belonging strategies during remote learning, in‐person, or all the time (both). Encouragement and support from teachers were found to be useful all the time, with school activities during breaks and opportunities to make friends only being useful during school‐based learning. From the examination of open‐ended responses using a hybrid qualitative approach with inductive and deductive coding, two overarching themes each at the teacher‐level and school‐level were found, defined by several subthemes. Belonging practices at the teacher‐level included caring and supportive teachers and teachers treating students as people. Belonging practices at the school‐level included student engagement and a positive and supportive school environment. For Qatari students practices such as prioritising supportive student–teacher relationships, introducing policies which promote a respectful, fair and safe environment, and offering school wide‐extracurricular activities that encourage peer connections are important to develop their sense of school belonging.
Published: 2024

117. Time-varying double-peaked emission lines following the sudden ignition of the dormant galactic nucleus AT2017bcc

Author: Ridley, E J, Nicholl, M, Ward, C A, Blanchard, P K, Chornock, R, Fraser, M, Gomez, S, Mattila, S, Oates, S R, Pratten, G, Runnoe, J C, Schmidt, P, Alexander, K D, Gromadzki, M, Lawrence, A, Reynolds, T M, Smith, K W, Wyrzykowski, Ł, Aamer, A, Anderson, J P, Benetti, S, Berger, E, De boer, T, Chambers, K C, Chen, T -w, Gao, H, Gutiérrez, C P, Inserra, C, Kangas, T, Leloudas, G, Magnier, E A, Makrygianni, L, Moore, T, Müller-bravo, T E, Smartt, S J, Sokolovsky, K V, Wainscoat, R, Young, D R, Ridley, E J, Nicholl, M, Ward, C A, Blanchard, P K, Chornock, R, Fraser, M, Gomez, S, Mattila, S, Oates, S R, Pratten, G, Runnoe, J C, Schmidt, P, Alexander, K D, Gromadzki, M, Lawrence, A, Reynolds, T M, Smith, K W, Wyrzykowski, Ł, Aamer, A, Anderson, J P, Benetti, S, Berger, E, De boer, T, Chambers, K C, Chen, T -w, Gao, H, Gutiérrez, C P, Inserra, C, Kangas, T, Leloudas, G, Magnier, E A, Makrygianni, L, Moore, T, Müller-bravo, T E, Smartt, S J, Sokolovsky, K V, Wainscoat, R, and Young, D R
Published: 2024

118. PS1-10jh Continues to Follow the Fallback Accretion Rate of a Tidally Disrupted Star

Author: Gezari, S., Chornock, R., Lawrence, A., Rest, A., Jones, D. O., Berger, E., Challis, P. M., and Narayan, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present late-time observations of the tidal disruption event candidate PS1-10jh. UV and optical imaging with HST/WFC3 localize the transient to be coincident with the host galaxy nucleus to an accuracy of 0.023 arcsec, corresponding to 66 pc. The UV flux in the F225W filter, measured 3.35 rest-frame years after the peak of the nuclear flare, is consistent with a decline that continues to follow a $t^{-5/3}$ power-law with no spectral evolution. Late epochs of optical spectroscopy obtained with MMT ~ 2 and 4 years after the peak, enable a clean subtraction of the host galaxy from the early spectra, revealing broad helium emission lines on top of a hot continuum, and placing stringent upper limits on the presence of hydrogen line emission. We do not measure Balmer H\delta absorption in the host galaxy strong enough to be indicative of a rare, post-starburst "E+A" galaxy as reported by Arcavi et al. (2014). The light curve of PS1-10jh over a baseline of 3.5 yr is best modeled by fallback accretion of a tidally disrupted star. Its strong broad helium emission relative to hydrogen (He II \lambda 4686/H\alpha > 5) could be indicative of either the hydrogen-poor chemical composition of the disrupted star, or certain conditions in the tidal debris of a solar-composition star in the presence of an optically-thick, extended reprocessing envelope., Comment: Accepted for publication in ApJ Letters
Published: 2015
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119. The First Millimeter Detection of a Non-Accreting Ultracool Dwarf

Author: Williams, P. K. G., Casewell, S. L., Stark, C. R., Littlefair, S. P., Helling, Ch., and Berger, E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: The well-studied M9 dwarf TVLM 513-46546 is a rapid rotator (P_rot ~ 2 hr) hosting a stable, dipolar magnetic field of ~3 kG surface strength. Here we report its detection with ALMA at 95 GHz at a mean flux density of $56 \pm 12$ uJy, making it the first ultracool dwarf detected in the millimeter band, excluding young, disk-bearing objects. We also report flux density measurements from unpublished archival VLA data and new optical monitoring data from the Liverpool Telescope. The ALMA data are consistent with a power-law radio spectrum that extends continuously between centimeter and millimeter wavelengths. We argue that the emission is due to the synchrotron process, excluding thermal, free-free, and electron cyclotron maser emission as possible sources. During the interval of the ALMA observation that phases with the maximum of the object's optical variability, the flux density is higher at a ~1.8 sigma significance level. These early results show how ALMA opens a new window for studying the magnetic activity of ultracool dwarfs, particularly shedding light on the particle acceleration mechanism operating in their immediate surroundings., Comment: 7 pages, 3 figures, 1 table; ApJ in press
Published: 2015
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120. Swift J1112.2-8238: A Candidate Relativistic Tidal Disruption Flare

Author: Brown, G. C., Levan, A. J., Stanway, E. R., Tanvir, N. R., Cenko, S. B., Berger, E., Chornock, R., and Cucchiaria, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare (rTDF). The outburst was first detected by Swift/BAT in June 2011 as an unknown, long-lived (order of days) $\gamma$-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of $z=0.89$ based on a single emission line that we interpret as the blended [OII]$\lambda3727$ doublet. At this redshift, the peak X/$\gamma$-ray luminosity exceeded $10^{47}$ ergs s$^{-1}$, while a spatially coincident optical transient source had $i^{\prime} \sim 22$ (M$_g \sim -21.4$ at $z=0.89$) during early observations, $\sim 20$ days after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while late time observations, almost 3 years post-outburst, demonstrate that it has now switched off. Swift J1112.2-8238 brings the total number of such events observed by Swift to three, interestingly all detected by Swift over a $\sim$3 month period ($<3\%$ of its total lifetime as of March 2015). While this suggests the possibility that further examples may be uncovered by detailed searches of the BAT archives, the lack of any prime candidates in the years since 2011 means these events are undoubtedly rare., Comment: 11 pages, 5 figures, accepted for publication by MNRAS
Published: 2015
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121. The Swift GRB Host Galaxy Legacy Survey - II. Rest-Frame NIR Luminosity Distribution and Evidence for a Near-Solar Metallicity Threshold

Author: Perley, D. A., Tanvir, N. R., Hjorth, J., Laskar, T., Berger, E., Chary, R., Postigo, A. de Ugarte, Fynbo, J. P. U., Krühler, T., Levan, A. J., Michałowski, M. J., and Schulze, S.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present rest-frame NIR luminosities and stellar masses for a large and uniformly-selected population of GRB host galaxies using deep Spitzer Space Telescope imaging of 119 targets from the Swift GRB Host Galaxy Legacy Survey spanning 0.03 < z < 6.3, and determine the effects of galaxy evolution and chemical enrichment on the mass distribution of the GRB host population across cosmic history. We find strong evolution in the host luminosity distribution between z~0.5 (median absolute NIR AB magnitude ~ -18.5, corresponding to M* ~ 3x10^8 M_sun and z~1.5), but negligible variation between z~1.5 and z~5 (median magnitude ~ -21.2, corresponding to M* ~ 5x10^9 M_sun). Dust-obscured GRBs dominate the massive host population but are only rarely seen associated with low-mass hosts, indicating that massive star-forming galaxies are universally and (to some extent) homogeneously dusty at high-redshift while low-mass star-forming galaxies retain little dust in their ISM. Comparing our luminosity distributions to field surveys and measurements of the high-z mass-metallicity relation, our results have good consistency with a model in which the GRB rate per unit star-formation is constant in galaxies with gas-phase metallicity below approximately the Solar value but heavily suppressed in more metal-rich environments. This model also naturally explains the previously-reported "excess" in the GRB rate beyond z>2; metals stifle GRB production in most galaxies at z<1.5 but have only minor impact at higher redshifts. The metallicity threshold we infer is much higher than predicted by single-star models and favors a binary progenitor. Our observations also constrain the fraction of cosmic star-formation in low-mass galaxies undetectable to Spitzer to be a small minority at most redshifts (~10% at z~2, ~25% at z~3, and ~50% at z=3.5-6.0)., Comment: Published in ApJ
Published: 2015
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122. The Swift Gamma-Ray Burst Host Galaxy Legacy Survey - I. Sample Selection and Redshift Distribution

Author: Perley, D. A., Krühler, T., Schulze, S., Postigo, A. de Ugarte, Hjorth, J., Berger, E., Cenko, S. B., Chary, R., Cucchiara, A., Ellis, R., Fong, W., Fynbo, J. P. U., Gorosabel, J., Greiner, J., Jakobsson, P., Kim, S., Laskar, T., Levan, A. J., Michałowski, M. J., Milvang-Jensen, B., Tanvir, N. R., Thöne, C. C., and Wiersema, K.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey ("SHOALS"), a multi-observatory high-redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host-galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly-deep, multi-color optical/NIR photometry, plus spectroscopy of events without pre-existing redshifts. Our optimized selection cuts combined with host-galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust-obscured, and at most 2% originate from z>5.5. Using this sample we estimate the redshift-dependent GRB rate density, showing it to peak at z~2.5 and fall by about an order of magnitude towards low (z=0) redshift, while declining more gradually towards high (z~7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star-formation occurring in undetectable galaxies at all redshifts., Comment: Published in ApJ
Published: 2015
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123. A Comprehensive Study of Detectability and Contamination in Deep Rapid Optical Searches for Gravitational Wave Counterparts

Author: Cowperthwaite, P. S. and Berger, E.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The first direct detection of gravitational waves (GW) by the ground-based interferometers is expected to occur within the next few years. These interferometers will detect the mergers of compact object binaries composed of neutron stars and/or black holes to a fiducial distance of ~200 Mpc and a localization region of ~100 sq. deg. To maximize the science gains from such GW detections it is essential to identify electromagnetic (EM) counterparts. The most promising such counterpart is optical/IR emission powered by the radioactive decay of r-process elements synthesized in the neutron-rich merger ejecta - a "kilonova". Here we present detailed simulated observations that encompass a range of strategies for kilonova searches during GW follow-up. We assess both the detectability of kilonovae and our ability to distinguish them from a wide range of contaminating transients. We find that if pre-existing template images for the localization region are available, then nightly observations to a depth of i=24 mag and z=23 mag are required to achieve a 95% detection rate; observations that commence within 12 hours of trigger will also capture the kilonova peak and provide stronger constraints on the ejecta properties. We also find that kilonovae can be robustly separated from other types of transients utilizing cuts on color (i-z > 0 mag) and rise time (< 4 days). In the absence of a pre-existing template the observations must reach ~1 mag deeper to achieve the same kilonova detection rate, but robust rejection of contaminants can still be achieved. Motivated by the results of our simulations we discuss the expected performance of current and future wide-field telescopes in achieving these observational goals, and find that prior to LSST the Dark Energy Camera on the Blanco 4-m telescope and Hyper Suprime-Cam on the Subaru 8-m telescope offer the best kilonova discovery potential., Comment: Emulate ApJ Format. 28 Pages, 20 Figures, 4 Tables. Submitted to ApJ
Published: 2015
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124. GALEX Detection of Shock Breakout in Type II-P Supernova PS1-13arp: Implications for the Progenitor Star Wind

Author: Gezari, S., Jones, D. O., Sanders, N. E., Soderberg, A. M., Hung, T., Heinis, S., Smartt, S. J., Rest, A., Scolnic, D., Chornock, R., Berger, E., Foley, R. J., Huber, M. E., Stubbs, P. Price C. W., Riess, A. G., Kirshner, R. P., Smith, K., Wood-Vasey, W. M., Schiminovich, D., Martin, D. C., Burgett, W. S., Chambers, K. C., Flewelling, H., Kaiser, N., Tonry, J. L., and Wainscoat, R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the GALEX detection of a UV burst at the time of explosion of an optically normal Type II-P supernova (PS1-13arp) from the Pan-STARRS1 survey at z=0.1665. The temperature and luminosity of the UV burst match the theoretical predictions for shock breakout in a red supergiant, but with a duration a factor of ~50 longer than expected. We compare the $NUV$ light curve of PS1-13arp to previous GALEX detections of Type IIP SNe, and find clear distinctions that indicate that the UV emission is powered by shock breakout, and not by the subsequent cooling envelope emission previously detected in these systems. We interpret the ~ 1 d duration of the UV signal with a shock breakout in the wind of a red supergiant with a pre-explosion mass-loss rate of ~ 10^-3 Msun yr^-1. This mass-loss rate is enough to prolong the duration of the shock breakout signal, but not enough to produce an excess in the optical plateau light curve or narrow emission lines powered by circumstellar interaction. This detection of non-standard, potentially episodic high mass-loss in a RSG SN progenitor has favorable consequences for the prospects of future wide-field UV surveys to detect shock breakout directly in these systems, and provide a sensitive probe of the pre-explosion conditions of SN progenitors., Comment: Accepted for Publication in ApJ
Published: 2015
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125. The Rotation Period and Magnetic Field of the T Dwarf 2MASSI J1047539+212423 Measured From Periodic Radio Bursts

Author: Williams, P. K. G. and Berger, E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Periodic radio bursts from very low mass stars and brown dwarfs simultaneously probe their magnetic and rotational properties. The brown dwarf 2MASSI J1047539+212423 (2M 1047+21) is currently the only T dwarf (T6.5) detected at radio wavelengths. Previous observations of this source with the Arecibo observatory revealed intermittent, 100%-polarized radio pulses similar to those detected from other brown dwarfs, but were unable to constrain a pulse periodicity; previous VLA observations detected quiescent emission a factor of ~100 times fainter than the Arecibo pulses but no additional events. Here we present 14 hours of Very Large Array observations of this object that reveal a series of pulses at ~6 GHz with highly variable profiles, showing that the pulsing behavior evolves on time scales that are both long and short compared to the rotation period. We measure a periodicity of ~1.77 hr and identify it with the rotation period. This is just the sixth rotation period measurement in a late T dwarf, and the first obtained in the radio. We detect a pulse at 10 GHz as well, suggesting that the magnetic field strength of 2M 1047+21 reaches at least 3.6 kG. Although this object is the coolest and most rapidly-rotating radio-detected brown dwarf to date, its properties appear continuous with those of other such objects, suggesting that the generation of strong magnetic fields and radio emission may continue to even cooler objects. Further studies of this kind will help to clarify the relationships between mass, age, rotation, and magnetic activity at and beyond the end of the main sequence, where both theories and observational data are currently scarce. A video of a short talk discussing this work is at http://youtu.be/OqCtFxcBB2s, and an experimental Web-native version of the paper may be viewed at http://purl.org/net/pkgwpub/goreham., Comment: ApJ submitted; 8 emulateapj pages, 4 figures
Published: 2015
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126. Selection of Burst-like Transients and Stochastic Variables Using Multi-Band Image Differencing in the Pan-STARRS1 Medium-Deep Survey

Author: Kumar, S., Gezari, S., Heinis, S., Chornock, R., Berger, E., Rest, A., Huber, M. E., Foley, R. J., Narayan, G., Marion, G. H., Scolnic, D., Soderberg, A., Lawrence, A., Stubbs, C. W., Kirshner, R. P., Riess, A. G., Smartt, S. J., Smith, K., Wood-Vasey, W. M, Burgett, W. S., Chambers, K. C., Flewelling, H., Kaiser, N., Metcalfe, N., Price, P. A., Tonry, J. L., and Wainscoat, R. J.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: We present a novel method for the light-curve characterization of Pan-STARRS1 Medium Deep Survey (PS1 MDS) extragalactic sources into stochastic variables (SV) and burst-like (BL) transients, using multi-band image-differencing time-series data. We select detections in difference images associated with galaxy hosts using a star/galaxy catalog extracted from the deep PS1 MDS stacked images, and adopt a maximum a posteriori formulation to model their difference-flux time-series in four Pan-STARRS1 photometric bands g,r,i, and z. We use three deterministic light-curve models to fit burst-like transients and one stochastic light curve model, the Ornstein-Uhlenbeck process, in order to fit variability that is characteristic of active galactic nuclei (AGN). We assess the quality of fit of the models band-wise source-wise, using their estimated leave-out-one cross-validation likelihoods and corrected Akaike information criteria. We then apply a K-means clustering algorithm on these statistics, to determine the source classification in each band. The final source classification is derived as a combination of the individual filter classifications. We use our clustering method to characterize 4361 extragalactic image difference detected sources in the first 2.5 years of the PS1 MDS, into 1529 BL, and 2262 SV, with a purity of 95.00% for AGN, and 90.97% for SN based on our verification sets. We combine our light-curve classifications with their nuclear or off-nuclear host galaxy offsets, to define a robust photometric sample of 1233 active galactic nuclei and 812 supernovae. We use these samples to identify simple photometric priors that would enable their real-time identification in future wide-field synoptic surveys., Comment: Accepted for publication in ApJ
Published: 2015
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127. Artificial intelligence to predict clinical disability in patients with multiple sclerosis using FLAIR MRI

Author: Brochet, B., Casey, R., Cotton, F., De Sèze, J., Douek, P., Guillemin, F., Laplaud, D., Lebrun-Frenay, C., Mansuy, L., Moreau, T., Olaiz, J., Pelletier, J., Rigaud-Bully, C., Stankoff, B., Vukusic, S., Marignier, R., Debouverie, M., Edan, G., Ciron, J., Ruet, A., Collongues, N., Lubetzki, C., Vermersch, P., Labauge, P., Defer, G., Cohen, M., Fromont, A., Wiertlewsky, S., Berger, E., Clavelou, P., Audoin, B., Giannesini, C., Gout, O., Thouvenot, E., Heinzlef, O., Al-Khedr, A., Bourre, B., Casez, O., Cabre, P., Montcuquet, A., Créange, A., Camdessanché, J.-P., Faure, J., Maurousset, A., Patry, I., Hankiewicz, K., Pottier, C., Maubeuge, N., Labeyrie, C., Nifle, C., Ameli, R., Anxionnat, R., Attye, A., Bannier, E., Barillot, C., Ben Salem, D., Boncoeur-Martel, M.-P., Bonneville, F., Boutet, C., Brisset, J.-C., Cervenanski, F., Claise, B., Commowick, O., Constans, J.-M., Dardel, P., Desal, H., Dousset, Vincent, Durand-Dubief, F., Ferre, J.-C., Gerardin, E., Glattard, T., Grand, S., Grenier, T., Guillevin, R., Guttmann, C., Krainik, A., Kremer, S., Lion, S., Menjot de Champfleur, N., Mondot, L., Outteryck, O., Pyatigorskaya, N., Pruvo, J.-P., Rabaste, S., Ranjeva, J.-P., Roch, J.-A., Sadik, J.C., Sappey-Marinier, D., Savatovsky, J., Tanguy, J.-Y., Tourbah, A., Tourdias, T., Roca, P., Colas, L., Tucholka, A., Rubini, P., Cackowski, S., Ding, J., Budzik, J.-F., Renard, F., Doyle, S., Barbier, E.L., Bousaid, I., Lassau, N., and Verclytte, S.
Published: 2020
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128. Measuring the ejecta velocities of type Ia supernovae from the pan-STARRS1 medium deep survey.

Author: Pan, Y -C, Jheng, Y -S, Jones, D O, Lee, I -Y, Foley, R J, Chornock, R, Scolnic, D M, Berger, E, Challis, P M, Drout, M, Huber, M E, Kirshner, R P, Kotak, R, Lunnan, R, Narayan, G, Rest, A, Rodney, S, and Smartt, S
Subjects: TYPE I supernovae, VELOCITY
Abstract: There is growing evidence that Type Ia supernovae (SNe Ia) may originate from multiple explosion channels. Previous studies have indicated that the ejecta velocity of SNe Ia is one powerful tool to discriminate between different channels. In this work, we study ∼400 confirmed SNe Ia discovered by the Pan-STARRS1 Medium Deep Survey (PS1-MDS), and obtain a sample of ∼50 SNe Ia that have near-peak |$\mathrm{Si}\, {\small II}\, \lambda 6355$| velocity (⁠|$v_{\mathrm{Si}\, {\small II}}$|⁠) measurements. We investigate the relationships between |$v_{\mathrm{Si}\, {\small II}}$| and various parameters, including SN light-curve width, colour, host galaxy properties, and redshift. No significant trends are identified between |$v_{\mathrm{Si}\, {\small II}}$| and light-curve parameters. Regarding the host-galaxy properties, we see a significant trend that high-velocity (HV) SNe Ia (⁠|$v_{\mathrm{Si}\, {\small II}}\gtrsim 12000$| km s |$^{-1}$|⁠) tend to reside in more massive galaxies compared to normal velocity (NV) SNe Ia (⁠|$v_{\mathrm{Si}\, {\small II}}\lt 12000$| km s |$^{-1}$|⁠) when combining both the PS1-MDS data set and those from previous low- z studies. While we do not see a significant trend between |$v_{\mathrm{Si}\, {\small II}}$| and redshift, HV SNe Ia appear to be more prevalent in low- z samples than in high- z samples. We discuss several possibilities that could potentially contribute to this trend. Furthermore, we investigate the potential bias on SN Ia distances and find no significant difference in Hubble residuals between HV and NV subgroups. [ABSTRACT FROM AUTHOR]
Published: 2024
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129. Trasfusione di prodotti sanguigni labili nelle strutture d’urgenza

Author: Avondo, A., Berger, E., and Ray, P.
Published: 2020
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130. A DECAM SEARCH FOR AN OPTICAL COUNTERPART TO THE LIGO GRAVITATIONAL-WAVE EVENT GW151226

Author: Cowperthwaite, PS, Berger, E, Soares-Santos, M, Annis, J, Brout, D, Brown, DA, Buckley-Geer, E, Cenko, SB, Chen, HY, Chornock, R, Diehl, HT, Doctor, Z, Drlica-Wagner, A, Drout, MR, Farr, B, Finley, DA, Foley, RJ, Fong, W, Fox, DB, Frieman, J, Garcia-Bellido, J, Gill, MSS, Gruendl, RA, Herner, K, Holz, DE, Kasen, D, Kessler, R, Lin, H, Margutti, R, Marriner, J, Matheson, T, Metzger, BD, Neilsen, EH, Quataert, E, Rest, A, Sako, M, Scolnic, D, Smith, N, Sobreira, F, Strampelli, GM, Villar, VA, Walker, AR, Wester, W, Williams, PKG, Yanny, B, Abbott, TMC, Abdalla, FB, Allam, S, Armstrong, R, Bechtol, K, Benoit-Lévy, A, Bertin, E, Brooks, D, Burke, DL, Rosell, A Carnero, Kind, M Carrasco, Carretero, J, Castander, FJ, Cunha, CE, D’Andrea, CB, da Costa, LN, Desai, S, Dietrich, JP, Evrard, AE, Neto, A Fausti, Fosalba, P, Gerdes, DW, Giannantonio, T, Goldstein, DA, Gruen, D, Gutierrez, G, Honscheid, K, James, DJ, Johnson, MWG, Johnson, MD, Krause, E, Kuehn, K, Kuropatkin, N, Lima, M, Maia, MAG, Marshall, JL, Menanteau, F, Miquel, R, Mohr, JJ, Nichol, RC, Nord, B, Ogando, R, Plazas, AA, Reil, K, Romer, AK, Sanchez, E, Scarpine, V, Sevilla-Noarbe, I, Smith, RC, Suchyta, E, Tarle, G, Thomas, D, Thomas, RC, Tucker, DL, and Weller, J
Subjects: binaries: close, catalogs, gravitational waves, stars: neutron, surveys, astro-ph.HE, astro-ph.CO, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract: We report the results of a Dark Energy Camera optical follow-up of the gravitational-wave (GW) event GW151226, discovered by the Advanced Laser Interferometer Gravitational-wave Observatory detectors. Our observations cover 28.8 deg2 of the localization region in the i and z bands (containing 3% of the BAYESTAR localization probability), starting 10 hr after the event was announced and spanning four epochs at 2-24 days after the GW detection. We achieve point-source limiting magnitudes of and , with a scatter of 0.4 mag, in our difference images. Given the two-day delay, we search this area for a rapidly declining optical counterpart with significance steady decline between the first and final observations. We recover four sources that pass our selection criteria, of which three are cataloged active galactic nuclei. The fourth source is offset by 5.8 arcsec from the center of a galaxy at a distance of 187 Mpc, exhibits a rapid decline by 0.5 mag over 4 days, and has a red color of mag. These properties could satisfy a set of cuts designed to identify kilonovae. However, this source was detected several times, starting 94 days prior to GW151226, in the Pan-STARRS Survey for Transients (dubbed as PS15cdi) and is therefore unrelated to the GW event. Given its long-term behavior, PS15cdi is likely a Type IIP supernova that transitioned out of its plateau phase during our observations, mimicking a kilonova-like behavior. We comment on the implications of this detection for contamination in future optical follow-up observations.
Published: 2016

131. A DARK ENERGY CAMERA SEARCH FOR AN OPTICAL COUNTERPART TO THE FIRST ADVANCED LIGO GRAVITATIONAL WAVE EVENT GW150914

Author: Soares-Santos, M, Kessler, R, Berger, E, Annis, J, Brout, D, Buckley-Geer, E, Chen, H, Cowperthwaite, PS, Diehl, HT, Doctor, Z, Drlica-Wagner, A, Farr, B, Finley, DA, Flaugher, B, Foley, RJ, Frieman, J, Gruendl, RA, Herner, K, Holz, D, Lin, H, Marriner, J, Neilsen, E, Rest, A, Sako, M, Scolnic, D, Sobreira, F, Walker, AR, Wester, W, Yanny, B, Abbott, TMC, Abdalla, FB, Allam, S, Armstrong, R, Banerji, M, Benoit-Levy, A, Bernstein, RA, Bertin, E, Brown, DA, Burke, DL, Capozzi, D, Carnero Rosell, A, Carrasco Kind, M, Carretero, J, Castander, FJ, Cenko, SB, Chornock, R, Crocce, M, D'Andrea, CB, da Costa, LN, Desai, S, Dietrich, JP, Drout, MR, Eifler, TF, Estrada, J, Evrard, AE, Fairhurst, S, Fernandez, E, Fischer, J, Fong, W, Fosalba, P, Fox, DB, Fryer, CL, Garcia-Bellido, J, Gaztanaga, E, Gerdes, DW, Goldstein, DA, Gruen, D, Gutierrez, G, Honscheid, K, James, DJ, Karliner, I, Kasen, D, Kent, S, Kuropatkin, N, Kuehn, K, Lahav, O, Li, TS, Lima, M, Maia, MAG, Margutti, R, Martini, P, Matheson, T, McMahon, RG, Metzger, BD, Miller, CJ, Miquel, R, Mohr, JJ, Nichol, RC, Nord, B, Ogando, R, Peoples, J, Plazas, AA, Quataert, E, Romer, AK, Roodman, A, Rykoff, ES, Sanchez, E, Scarpine, V, Schindler, R, and Schubnell, M
Subjects: binaries: close, catalogs, gravitational waves, stars: neutron, surveys, Astronomy & Astrophysics, Astronomical and Space Sciences
Published: 2016

132. A DARK ENERGY CAMERA SEARCH FOR MISSING SUPERGIANTS IN THE LMC AFTER THE ADVANCED LIGO GRAVITATIONAL-WAVE EVENT GW150914

Author: Annis, J, Soares-Santos, M, Berger, E, Brout, D, Chen, H, Chornock, R, Cowperthwaite, PS, Diehl, HT, Doctor, Z, Drlica-Wagner, A, Drout, MR, Farr, B, Finley, DA, Flaugher, B, Foley, RJ, Frieman, J, Gruendl, RA, Herner, K, Holz, D, Kessler, R, Lin, H, Marriner, J, Neilsen, E, Rest, A, Sako, M, Smith, M, Smith, N, Sobreira, F, Walker, AR, Yanny, B, Abbott, TMC, Abdalla, FB, Allam, S, Benoit-Levy, A, Bernstein, RA, Bertin, E, Buckley-Geer, E, Burke, DL, Capozzi, D, Carnero Rosell, A, Carrasco Kind, M, Carretero, J, Castander, FJ, Cenko, SB, Crocce, M, Cunha, CE, D'Andrea, CB, da Costa, LN, Desai, S, Dietrich, JP, Eifler, TF, Evrard, AE, Fernandez, E, Fischer, J, Fong, W, Fosalba, P, Fox, DB, Fryer, CL, Garcia-Bellido, J, Gaztanaga, E, Gerdes, DW, Goldstein, DA, Gruen, D, Gutierrez, G, Honscheid, K, James, DJ, Karliner, I, Kasen, D, Kent, S, Kuehn, K, Kuropatkin, N, Lahav, O, Li, TS, Lima, M, Maia, MAG, Martini, P, Metzger, BD, Miller, CJ, Miquel, R, Mohr, JJ, Nichol, RC, Nord, B, Ogando, R, Peoples, J, Petravic, D, Plazas, AA, Quataert, E, Romer, AK, Roodman, A, Rykoff, ES, Sanchez, E, Santiago, B, Scarpine, V, Schindler, R, Schubnell, M, Sevilla-Noarbe, I, Sheldon, E, Smith, RC, Stebbins, A, and Swanson, MEC
Subjects: galaxies: individual, gravitational waves, Magellanic Clouds, supergiants, supernovae: general, Astronomy & Astrophysics, Astronomical and Space Sciences
Published: 2016

133. XIPE: the x-ray imaging polarimetry explorer

Author: Soffitta, Paolo, Bellazzini, Ronaldo, Bozzo, Enrico, Burwitz, Vadim, Castro Tirado, Alberto, Costa, Enrico, Courvoisier, Thierry, Feng, Hua, Gburek, Szymon, Goosmann, Rene', Karas, Vladimir, Matt, Giorgio, Muleri, Fabio, Nandra, Kirpal, Pearce, Mark, Poutanen, Juri, Reglero, Victor, Graziati, Maria Dolores, Santangelo, Andrea, Tagliaferri, Gianpiero, Tenzer, Christopher, Vink, Jacco, Weisskopf, Martin, Zane, Silvia, Agudo, I, Antonelli, A, Attina, P, Baldini, L, Bykov, A, Carpentiero, R, Cavazzuti, E, Churazov, E, Del Monte, E, De Martino, D, Donnarumma, I, Doroshenko, V, Evangelista, Y, Ferreira, I, Gallo, E, Grosso, N, Kaaret, P, Kuulkers, E, Laranaga, J, Latronico, L, Lumb, DH, Macian, J, Malzac, J, Marin, F, Massaro, E, Minuti, M, Mundell, C, Ness, JU, Oosterbroek, T, Paltani, S, Pareschi, G, Perna, R, Petrucci, P-O, Pinazo, HB, Pinchera, M, Rodriguez, JP, Roncadelli, M, Santovincenzo, A, Sazonov, S, Sgro, C, Spiga, D, Svoboda, J, Theobald, C, Theodorou, T, Turolla, R, Wilhelmi de Ona, E, Winter, B, Akbar, AM, Allan, H, Aloisio, R, Altamirano, D, Amati, L, Amato, E, Angelakis, E, Arezu, J, Atteia, J-L, Axelsson, M, Bachetti, M, Ballo, L, Balman, S, Bandiera, R, Barcons, X, Basso, S, Baykal, A, Becker, W, Behar, E, Beheshtipour, B, Belmont, R, Berger, E, Bernardini, F, Bianchi, S, Bisnovatyi-Kogan, G, Blasi, P, Blay, P, Bodaghee, A, and Boer, M
Subjects: X-ray Astronomy, Polarimetry, X-ray optics, Gas Pixel Detector
Abstract: XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially-resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden.
Published: 2016

134. XIPE: The X-ray imaging polarimetry explorer

Author: Soffitta, P, Bellazzini, R, Bozzo, E, Burwitz, V, Castro-Tirado, AJ, Costa, E, Courvoisier, T, Feng, H, Gburek, S, Goosmann, R, Karas, V, Matt, G, Muleri, F, Nandra, K, Pearce, M, Poutanen, J, Reglero, V, Sabau Maria, D, Santangelo, A, Tagliaferri, G, Tenzer, C, Vink, J, Weisskopf, MC, Zane, S, Agudo, I, Antonelli, A, Attina, P, Baldini, L, Bykov, A, Carpentiero, R, Cavazzuti, E, Churazov, E, Del Monte, E, De Martino, D, Donnarumma, I, Doroshenko, V, Evangelista, Y, Ferreira, I, Gallo, E, Grosso, N, Kaaret, P, Kuulkers, E, Laranaga, J, Latronico, L, Lumb, DH, Macian, J, Malzac, J, Marin, F, Massaro, E, Minuti, M, Mundell, C, Ness, JU, Oosterbroek, T, Paltani, S, Pareschi, G, Perna, R, Petrucci, PO, Pinazo, HB, Pinchera, M, Rodriguez, JP, Roncadelli, M, Santovincenzo, A, Sazonov, S, Sgro, C, Spiga, D, Svoboda, J, Theobald, C, Theodorou, T, Turolla, R, Wilhelmi De Ona, E, Winter, B, Akbar, AM, Allan, H, Aloisio, R, Altamirano, D, Amati, L, Amato, E, Angelakis, E, Arezu, J, Atteia, JL, Axelsson, M, Bachetti, M, Ballo, L, Balman, S, Bandiera, R, Barcons, X, Basso, S, Baykal, A, Becker, W, Behar, E, Beheshtipour, B, Belmont, R, Berger, E, Bernardini, F, Bianchi, S, Bisnovatyi-Kogan, G, Blasi, P, Blay, P, Bodaghee, A, and Boer, M
Subjects: X-ray Astronomy, Polarimetry, X-ray optics, Gas Pixel Detector
Abstract: XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially-resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden.
Published: 2016

135. Zooming In on the Progenitors of Superluminous Supernovae With the HST

Author: Lunnan, R., Chornock, R., Berger, E., Rest, A., Fong, W., Scolnic, D., Jones, D., Soderberg, A. M., Challis, P. M., Drout, M. R., Foley, R. J., Huber, M. E., Kirshner, R. P., Leibler, C., Marion, G. H., McCrum, M., Milisavljevic, D., Narayan, G., Sanders, N. E., Smartt, S. J., Smith, K. W., Tonry, J. L., Burgett, W. S., Chambers, K. C., Flewelling, H., Kudritzki, R. -P., Wainscoat, R. J., and Waters, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present Hubble Space Telescope (HST) rest-frame ultraviolet imaging of the host galaxies of 16 hydrogen-poor superluminous supernovae (SLSNe), including 11 events from the Pan-STARRS Medium Deep Survey. Taking advantage of the superb angular resolution of HST, we characterize the galaxies' morphological properties, sizes and star formation rate (SFR) densities. We determine the supernova (SN) locations within the host galaxies through precise astrometric matching, and measure physical and host-normalized offsets, as well as the SN positions within the cumulative distribution of UV light pixel brightness. We find that the host galaxies of H-poor SLSNe are irregular, compact dwarf galaxies, with a median half-light radius of just 0.9 kpc. The UV-derived SFR densities are high ( ~ 0.1 M_sun/yr/kpc^2), suggesting that SLSNe form in overdense environments. Their locations trace the UV light of their host galaxies, with a distribution intermediate between that of long-duration gamma-ray bursts (LGRBs) (which are strongly clustered on the brightest regions of their hosts) and a uniform distribution (characteristic of normal core-collapse SNe), though cannot be statistically distinguished from either with the current sample size. Taken together, this strengthens the picture that SLSN progenitors require different conditions than those of ordinary core-collapse SNe to form, and that they explode in broadly similar galaxies as do LGRBs. If the tendency for SLSNe to be less clustered on the brightest regions than are LGRBs is confirmed by a larger sample, this would indicate a different, potentially lower-mass progenitor for SLSNe than LRGBs., Comment: ApJ in press; matches published version. Minor changes following referee's comments; conclusions unchanged
Published: 2014
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136. Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. IV. The Active, Young Binary NLTT 33370 AB (=2MASS J13142039+1320011)

Author: Williams, P. K. G., Berger, E., Irwin, J., Berta-Thompson, Z. K., and Charbonneau, D.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: We present multi-epoch simultaneous radio, optical, H{\alpha}, UV, and X-ray observations of the active, young, low-mass binary NLTT 33370 AB (blended spectral type M7e). This system is remarkable for its extreme levels of magnetic activity: it is the most radio-luminous ultracool dwarf (UCD) known, and here we show that it is also one of the most X-ray luminous UCDs known. We detect the system in all bands and find a complex phenomenology of both flaring and periodic variability. Analysis of the optical light curve reveals the simultaneous presence of two periodicities, 3.7859 $\pm$ 0.0001 and 3.7130 $\pm$ 0.0002 hr. While these differ by only ~2%, studies of differential rotation in the UCD regime suggest that it cannot be responsible for the two signals. The system's radio emission consists of at least three components: rapid 100% polarized flares, bright emission modulating periodically in phase with the optical emission, and an additional periodic component that appears only in the 2013 observational campaign. We interpret the last of these as a gyrosynchrotron feature associated with large-scale magnetic fields and a cool, equatorial plasma torus. However, the persistent rapid flares at all rotational phases imply that small-scale magnetic loops are also present and reconnect nearly continuously. We present an SED of the blended system spanning more than 9 orders of magnitude in wavelength. The significant magnetism present in NLTT 33370 AB will affect its fundamental parameters, with the components' radii and temperatures potentially altered by ~+20% and ~-10%, respectively. Finally, we suggest spatially resolved observations that could clarify many aspects of this system's nature., Comment: emulateapj, 22 pages, 15 figures, ApJ in press; v2: fixes low-impact error in Figure 15; v3: now in-press
Published: 2014
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137. ALMA Observations of the Host Galaxy of GRB090423 at z=8.23: Deep Limits on Obscured Star Formation 630 Million Years After the Big Bang

Author: Berger, E., Zauderer, B. A., Chary, R. -R., Laskar, T., Chornock, R., Tanvir, N. R., Stanway, E. R., Levan, A. J., Levesque, E. M., and Davies, J. E.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We present rest-frame far-infrared (FIR) and optical observations of the host galaxy of GRB090423 at z=8.23 from the Atacama Large Millimeter Array (ALMA) and the Spitzer Space Telescope, respectively. The host remains undetected to 3-sigma limits of Fnu(222 GHz)<33 microJy and Fnu(3.6 micron)<81 nJy. The FIR limit is about 20 times fainter than the luminosity of the local ULIRG Arp220, and comparable to the local starburst M82. Comparing to model spectral energy distributions we place a limit on the IR luminosity of L_IR(8-1000 micron)<3e10 Lsun, corresponding to a limit on the obscured star formation rate of SFR_IR<5 Msun/yr; for comparison, the limit on the unobscured star formation rate from Hubble Space Telescope rest-frame UV observations is SFR_UV<1 Msun/yr. We also place a limit on the host galaxy stellar mass of <5e7 Msun (for a stellar population age of 100 Myr and constant star formation rate). Finally, we compare our millimeter observations to those of field galaxies at z>4 (Lyman break galaxies, Ly-alpha emitters, and submillimeter galaxies), and find that our limit on the FIR luminosity is the most constraining to date, although the field galaxies have much larger rest-frame UV/optical luminosities than the host of GRB090423 by virtue of their selection techniques. We conclude that GRB host galaxies at z>4, especially those with measured interstellar medium metallicities from afterglow spectroscopy, are an attractive sample for future ALMA studies of high redshift obscured star formation., Comment: Submitted to ApJ; 9 pages, 3 figures, 2 tables
Published: 2014
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138. GRB 140515A at z=6.33: Constraints on the End of Reionization From a Gamma-ray Burst in a Low Hydrogen Column Density Environment

Author: Chornock, R., Berger, E., Fox, D. B., Fong, W., Laskar, T., and Roth, K. C.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the discovery and subsequent spectroscopy with Gemini-North of the optical afterglow of the Swift gamma-ray burst (GRB) 140515A. The spectrum exhibits a well-detected continuum at wavelengths longer than 8915 Angs with a steep decrement to zero flux blueward of 8910 Angs due to Ly-alpha absorption at redshift z~6.33. Some transmission through the Lyman-alpha forest is present at 5.2~6., Comment: submitted to ApJ Letters, 6 pages, 4 figures, 1 table
Published: 2014

139. Rapidly-Evolving and Luminous Transients from Pan-STARRS1

Author: Drout, M. R., Chornock, R., Soderberg, A. M., Sanders, N. E., McKinnon, R., Rest, A., Foley, R. J., Milisavljevic, D., Margutti, R., Berger, E., Calkins, M., Fong, W., Gezari, S., Huber, M. E., Kankare, E., Kirshner, R. P., Leibler, C., Lunnan, R., Mattila, S., Marion, G. H., Narayan, G., Riess, A. G., Roth, K. C., Scolnic, D., Smartt, S. J., Tonry, J. L., Burgett, W. S., Chambers, K. C., Hodapp, K. W., Jedicke, R., Kaiser, N., Magnier, E. A., Metcalfe, N., Morgan, J. S., Price, P. A., and Waters, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: In the past decade, several rapidly-evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SN) models. The sample size of these objects has remained small due, at least in part, to the challenge of detecting short timescale transients with traditional survey cadences. Here we present the results from a search within the Pan-STARRS1 Medium Deep Survey (PS1-MDS) for rapidly-evolving and luminous transients. We identify 10 new transients with a time above half-maximum of less than 12 days and -16.5 > M > -20 mag. This increases the number of known events in this region of SN phase space by roughly a factor of three. The median redshift of the PS1-MDS sample is z=0.275 and they all exploded in star forming galaxies. In general, the transients possess faster rise than decline timescale and blue colors at maximum light (g - r < -0.2). Best fit blackbodies reveal photospheric temperatures/radii that expand/cool with time and explosion spectra taken near maximum light are dominated by a blue continuum, consistent with a hot, optically thick, ejecta. We find it difficult to reconcile the short timescale, high peak luminosity (L > 10^43 erg/s), and lack of UV line blanketing observed in many of these transients with an explosion powered mainly by the radioactive decay of Ni-56. Rather, we find that many are consistent with either (1) cooling envelope emission from the explosion of a star with a low-mass extended envelope which ejected very little (<0.03 M_sun) radioactive material, or (2) a shock breakout within a dense, optically thick, wind surrounding the progenitor star. After calculating the detection efficiency for objects with rapid timescales in the PS1-MDS we find a volumetric rate of 4800 - 8000 events/yr/Gpc^3 (4-7% of the core-collapse SN rate at z=0.2)., Comment: Accepted for Publication in ApJ
Published: 2014
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140. Towards Characterization of the Type IIP Supernova Progenitor Population: a Statistical Sample of Light Curves from Pan-STARRS1

Author: Sanders, N. E., Soderberg, A. M., Gezari, S., Betancourt, M., Chornock, R., Berger, E., Foley, R. J., Challis, P., Drout, M., Kirshner, R. P., Lunnan, R., Marion, G. H., Margutti, R., McKinnon, R., Milisavljevic, D., Narayan, G., Rest, A., Kankare, E., Mattila, S., Smartt, S. J., Huber, M. E., Burgett, W. S., Draper, P. W., Hodapp, K. W., Kaiser, N., Kudritzki, R. P., Magnier, E. A., Metcalfe, N., Morgan, J. S., Price, P. A., Tonry, J. L., Wainscoat, R. J., and Waters, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: In recent years, wide-field sky surveys providing deep multi-band imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SN): systematic light curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4 years and classified using both spectroscopy and machine learning-based photometric techniques. We develop and apply a new Bayesian model for the full multi-band evolution of each light curve in the sample. We find no evidence of a sub-population of fast-declining explosions (historically referred to as "Type IIL" SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for supernova cosmology, offering a standardizable candle good to an intrinsic scatter of 0.2 mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light curve properties and an expanded grid of progenitor properties, are needed to enable robust progenitor inferences from multi-band light curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide field transient searches., Comment: 25 pages plus tables, 19 figures, V2 matches version published in ApJ
Published: 2014
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141. Selecting superluminous supernovae in faint galaxies from the first year of the Pan-STARRS1 Medium Deep Survey

Author: McCrum, M., Smartt, S. J., Rest, A., Smith, K., Kotak, R., Rodney, S. A., Young, D. R., Chornock, R., Berger, E., Foley, R. J., Fraser, M., Wright, D., Scolnic, D., Tonry, J. L., Urata, Y., Huang, K., Pastorello, A., Botticella, M. T., Valenti, S., Mattila, S., Kankare, E., Farrow, D. J., Huber, M. E., Stubbs, C. W., Kirshner, R. P., Bresolin, F., Burgett, W. S., Chambers, K. C., Draper, P. W., Flewelling, H., Jedicke, R., Kaiser, N., Magnier, E. A., Metcalfe, N., Morgan, J. S., Price, P. A., Sweeney, W., Wainscoat, R. J., and Waters, C.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Pan-STARRS1 (PS1) survey has obtained imaging in 5 bands (grizy_P1) over 10 Medium Deep Survey (MDS) fields covering a total of 70 square degrees. This paper describes the search for apparently hostless supernovae (SNe) within the first year of PS1 MDS data with an aim of discovering new superluminous supernovae (SLSNe). A total of 249 hostless transients were discovered down to a limiting magnitude of M_AB ~ 23.5, of which 76 were classified as Type Ia SNe. There were 57 SNe with complete light curves that are likely core-collapse SNe (CCSNe) or SLSNe and 12 of these have had spectra taken. Of these 12 hostless, non-Type Ia SNe, 7 were SLSNe of Type Ic at redshifts between 0.5-1.4. This illustrates that the discovery rate of Type Ic SLSNe can be maximised by concentrating on hostless transients and removing normal SNe Ia. We present data for two new possible SLSNe; PS1-10pm (z = 1.206) and PS1-10ahf (z = 1.1), and estimate the rate of SLSNe-Ic to be between 3^{+3}_{-2} * 10^{-5} and 8^{+2}_{-1} * 10^{-5} of the CCSNe rate within 0.3 <= z <= 1.4 by applying a Monte-Carlo technique. The rate of slowly evolving, SN2007bi-like explosions is estimated as a factor of 10 lower than this range., Comment: 26 pages, 16 figures, Accepted for publication in MNRAS
Published: 2014
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142. Characterization of the Benchmark Binary NLTT 33370

Author: Schlieder, J. E., Bonnefoy, M., Herbst, T. M., Lepine, S., Berger, E., Henning, Th., Skemer, A., Chauvin, G., Rice, E., Biller, B., Girard, J. H. V., Lagrange, A. M., Hinz, P., Defrere, D., Bergfors, C., Brandner, W., Lacour, S., Skrutskie, M., and Leisenring, J.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: We report the confirmation of the binary nature of the nearby, very low-mass system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show significant orbital motion between 2013 February and 2013 April. Optical spectra reveal weak, gravity sensitive alkali lines and strong lithium 6708 Angstrom absorption that indicate the system is younger than field age. VLT-SINFONI near-IR spectra also show weak, gravity sensitive features and spectral morphology that is consistent with other young, very low-mass dwarfs. We combine the constraints from all age diagnostics to estimate a system age of ~30-200 Myr. The 1.2-4.7 micron spectral energy distribution of the components point toward T_eff=3200 +/- 500 K and T_eff=3100 +/- 500 K for NLTT 33370 A and B, respectively. The observed spectra, derived temperatures, and estimated age combine to constrain the component spectral types to the range M6-M8. Evolutionary models predict masses of 113 +/- 8 M_Jup and 106 +/- 7 M_Jup from the estimated luminosities of the components. KPNO-Phoenix spectra allow us to estimate the systemic radial velocity of the binary. The Galactic kinematics of NLTT 33370AB are broadly consistent with other young stars in the Solar neighborhood. However, definitive membership in a young, kinematic group cannot be assigned at this time and further follow-up observations are necessary to fully constrain the system's kinematics. The proximity, age, and late-spectral type of this binary make it very novel and an ideal target for rapid, complete orbit determination. The system is one of only a few model calibration benchmarks at young ages and very low-masses., Comment: 25 pages, 3 tables, 13 figures, accepted for publication in The Astrophysical Journal
Published: 2014
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143. New constraints on GRB jet geometry and relativistic shock physics

Author: Guidorzi, C., Mundell, C. G., Harrison, R., Margutti, R., Sudilovsky, V., Zauderer, B. A., Kobayashi, S., Cucchiara, A., Melandri, A., Pandey, S. B., Berger, E., Bersier, D., D'Elia, V., Gomboc, A., Greiner, J., Japelj, J., Kopac, D., Kumar, B., Malesani, D., Mottram, C. J., O'Brien, P. T., Rau, A., Smith, R. J., Steele, I. A., Tanvir, N. R., and Virgili, F.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We use high--quality, multi-band observations of Swift GRB120404A, from gamma-ray to radio frequencies, together with the new hydrodynamics code of van Eerten et al. (2012) to test the standard synchrotron shock model. The evolution of the radio and optical afterglow, with its prominent optical rebrightening at t_rest 260-2600 s, is remarkably well modelled by a decelerating jet viewed close to the jet edge, combined with some early re-energization of the shock. We thus constrain the geometry of the jet with half-opening and viewing angles of 23 and 21 deg respectively and suggest that wide jets viewed off-axis are more common in GRBs than previously thought. We also derive the fireball microphysics parameters epsilon_B=2.4e-4 and epsilon_e=9.3e-2 and a circumburst density of n=240 cm^-3. The ability to self-consistently model the microphysics parameters and jet geometry in this way offers an alternative to trying to identify elusive canonical jet breaks at late times. The mismatch between the observed and model-predicted X-ray fluxes is explained by the local rather than the global cooling approximation in the synchrotron radiation model, constraining the microphysics of particle acceleration taking place in a relativistic shock and, in turn, emphasising the need for a more realistic treatment of cooling in future developments of theoretical models. Finally, our interpretation of the optical peak as due to the passage of the forward shock synchrotron frequency highlights the importance of high quality multi-band data to prevent some optical peaks from being erroneously attributed to the onset of fireball deceleration., Comment: 21 pages, 8 figures, 7 tables, accepted to MNRAS
Published: 2013
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144. Hydrogen-Poor Superluminous Supernovae and Long-Duration Gamma-Ray Bursts Have Similar Host Galaxies

Author: Lunnan, R., Chornock, R., Berger, E., Laskar, T., Fong, W., Rest, A., Sanders, N. E., Challis, P. M., Drout, M. R., Foley, R. J., Huber, M. E., Kirshner, R. P., Leibler, C., Marion, G. H., McCrum, M., Milisavljevic, D., Narayan, G., Scolnic, D., Smartt, S. J., Smith, K. W., Soderberg, A. M., Tonry, J. L., Burgett, W. S., Chambers, K. C., Flewelling, H., Hodapp, K. W., Kaiser, N., Magnier, E. A., Price, P. A., and Wainscoat, R. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present optical spectroscopy and optical/near-IR photometry of 31 host galaxies of hydrogen-poor superluminous supernovae (SLSNe), including 15 events from the Pan-STARRS1 Medium Deep Survey. Our sample spans the redshift range 0.1 < z < 1.6 and is the first comprehensive host galaxy study of this specific subclass of cosmic explosions. Combining the multi-band photometry and emission-line measurements, we determine the luminosities, stellar masses, star formation rates and metallicities. We find that as a whole, the hosts of SLSNe are a low-luminosity ( ~ -17.3 mag), low stellar mass ( ~ 2 x 10^8 M_sun) population, with a high median specific star formation rate ( ~ 2 Gyr^-1). The median metallicity of our spectroscopic sample is low, 12 + log(O/H}) ~ 8.35 ~ 0.45 Z_sun, although at least one host galaxy has solar metallicity. The host galaxies of H-poor SLSNe are statistically distinct from the hosts of GOODS core-collapse SNe (which cover a similar redshift range), but resemble the host galaxies of long-duration gamma-ray bursts (LGRBs) in terms of stellar mass, SFR, sSFR and metallicity. This result indicates that the environmental causes leading to massive stars forming either SLSNe or LGRBs are similar, and in particular that SLSNe are more effectively formed in low metallicity environments. We speculate that the key ingredient is large core angular momentum, leading to a rapidly-spinning magnetar in SLSNe and an accreting black hole in LGRBs., Comment: ApJ in press; updated to match accepted version. Some additional data added, discussion of selection effects expanded; conclusions unchanged. 22 pages in emulateapj format
Published: 2013
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145. Trends in Ultracool Dwarf Magnetism. I. X-Ray Suppression and Radio Enhancement

Author: Williams, P. K. G., Cook, B. A., and Berger, E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Although ultracool dwarfs (UCDs) are now known to generate and dissipate strong magnetic fields, a clear understanding of the underlying dynamo is still lacking. We have performed X-ray and radio observations of seven UCDs in a narrow range of spectral type (M6.5-M9.5) but spanning a wide range of projected rotational velocities (v sin i ~ 3-40 km/s). We have also analyzed unpublished archival Chandra observations of four additional objects. All of the newly-observed targets are detected in the X-ray, while only one is detected in the radio, with the remainder having sensitive upper limits. We present a database of UCDs with both radio and X-ray measurements and consider the data in light of the so-called G\"udel-Benz relation (GBR) between magnetic activity in these bands. Some UCDs have very bright radio emission and faint X-ray emission compared to what would be expected for rapid rotators, while others show opposite behavior. We show that UCDs would still be radio-over-luminous relative to the GBR even if their X-ray emission were at standard rapid-rotator "saturation" levels. Recent results from Zeeman-Doppler imaging and geodynamo simulations suggest that rapidly-rotating UCDs may harbor a bistable dynamo that supports either a stronger, axisymmetric magnetic field or a weaker, non-axisymmetric field. We suggest that the data can be explained in a scenario in which strong-field objects obey the GBR while weak-field objects are radio-over-luminous and X-ray-under-luminous, possibly because of a population of gyrosynchrotron-emitting coronal electrons that is continuously replenished by low-energy reconnection events., Comment: 24 pages, 12 figures; ApJ in press; v2: accepted version, including new figure
Published: 2013
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146. Trends in Ultracool Dwarf Magnetism. II. The Inverse Correlation Between X-ray Activity and Rotation as Evidence for a Bimodal Dynamo

Author: Cook, B. A., Williams, P. K. G., and Berger, E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Observations of magnetic activity indicators in solar-type stars exhibit a relationship with rotation with an increase until a "saturation" level and a moderate decrease in activity in the very fastest rotators ("supersaturation"). While X-ray data have suggested that this relationship is strongly violated in ultracool dwarfs (UCDs; spectral type >M7), the limited number of X-ray detections has prevented firm conclusions. In this paper, we analyze the X-ray activity-rotation relation in 38 ultracool dwarfs. Our sample represents the largest catalog of X-ray active ultracool dwarfs to date, including seven new and four previously-unpublished Chandra observations presented in a companion paper. We identify a substantial number of rapidly-rotating UCDs with X-ray activity extending two orders of magnitude below the expected saturation level and measure a "supersaturation"-type anticorrelation between rotation and X-ray activity. The scatter in UCD X-ray activity at a fixed rotation is ~3 times larger than that in earlier-type stars. We discuss several mechanisms that have been proposed to explain the data, including centrifugal stripping of the corona, and find them to be inconsistent with the observed trends. Instead, we suggest that an additional parameter correlated with both X-ray activity and rotation is responsible for the observed effects. Building on the results of Zeeman-Doppler imaging of UCD magnetic fields and our companion study of radio/X-ray flux ratios, we argue that this parameter is the magnetic field topology, and that the large scatter in UCD X-ray fluxes reflects the presence of two dynamo modes that produce distinct topologies., Comment: 11 pages, 5 figures, 3 tables; ApJ in press
Published: 2013
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147. The superluminous supernova PS1-11ap: bridging the gap between low and high redshift

Author: McCrum, M., Smartt, S. J., Kotak, R., Rest, A., Jerkstrand, A., Inserra, C., Rodney, S. A., Chen, T. -W., Howell, D. A., Huber, M. E., Pastorello, A., Tonry, J. L., Bresolin, F., Kudritzki, R. -P., Chornock, R., Berger, E., Smith, K., Botticella, M. T., Foley, R. J., Fraser, M., Milisavljevic, D., Nicholl, M., Riess, A. G., Stubbs, C. W., Valenti, S., Wood-Vasey, W. M., Wright, D., Young, D. R., Drout, M., Czekala, I., Burgett, W. S., Chambers, K. C., Draper, P., Flewelling, H., Hodapp, K. W., Kaiser, N., Magnier, E. A., Metcalfe, N., Sweeney, W., and Wainscoat, R. J.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of M_u = -21.4 mag and bolometric luminosity of 8 x 10^43 ergs^-1 before settling onto a relatively shallow gradient of decline. The observed decline is significantly slower than those of the superluminous type Ic SNe which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay timescale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 days before peak to 230 days after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining superluminous Ic supernovae and the lightcurve evolution can also be quantitatively explained by the magnetar spin down model. At a redshift of z = 0.524 the observer frame optical coverage provides comprehensive restframe UV data and allows us to compare it with the superluminous SNe recently found at high redshifts between z = 2-4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient., Comment: 19 pages, 10 figures, Accepted for publication in MNRAS
Published: 2013
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148. Slowly fading super-luminous supernovae that are not pair-instability explosions

Author: Nicholl, M., Smartt, S. J., Jerkstrand, A., Inserra, C., McCrum, M., Kotak, R., Fraser, M., Wright, D., Chen, T. -W., Smith, K., Young, D. R., Sim, S. A., Valenti, S., Howell, D. A., Bresolin, F., Kudritzki, R. P., Tonry, J. L., Huber, M. E., Rest, A., Pastorello, A., Tomasella, L., Cappellaro, E., Benetti, S., Mattila, S., Kankare, E., Kangas, T., Leloudas, G., Sollerman, J., Taddia, F., Berger, E., Chornock, R., Narayan, G., Stubbs, C. W., Foley, R. J., Lunnan, R., Soderberg, A., Sanders, N., Milisavljevic, D., Margutti, R., Kirshner, R. P., Elias-Rosa, N., Morales-Garoffolo, A., Taubenberger, S., Botticella, M. T., Gezari, S., Urata, Y., Rodney, S., Riess, A. G., Scolnic, D., Wood-Vasey, W. M., Burgett, W. S., Chambers, K., Flewelling, H. A., Magnier, E. A., Kaiser, N., Metcalfe, N., Morgan, J., Price, P. A., Sweeney, W., and Waters, C.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: Super-luminous supernovae that radiate more than 10^44 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-30 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of 56Ni are synthesized; this isotope decays to 56Fe via 56Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6x10^-6 times that of the core-collapse rate., Comment: Originally published in Nature, Oct 2013. Updated Oct 2016 to correct an error
Published: 2013
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149. Systematic Uncertainties Associated with the Cosmological Analysis of the First Pan-STARRS1 Type Ia Supernova Sample

Author: Scolnic, D., Rest, A., Riess, A., Huber, M. E., Foley, R. J., Brout, D., Chornock, R., Narayan, G., Tonry, J. L., Berger, E., Soderberg, A. M., Stubbs, C. W., Kirshner, R. P., Rodney, S., Smartt, S. J., Schlafly, E., Botticella, M. T., Challis, P., Czekal, I., Drout, M., Hudson, M. J., Kotak, R., Leibler, C., Lunnan, R., Marion, G. H., McCrum, M., Milisavljevic, D., Pastorello, A., Sanders, N. E., Smith, K., Stafford, E., Thilker, D., Valenti, S., Wood-Vasey, W. M., Zheng, Z., Burgett, W. S., Chambers, K. C., Denneau, L., Draper, P. W., Flewelling, H., Hodapp, K. W., Kaiser, N., Kudritzki, R. P., Magnier, E. A., Metcalfe, N., Price, P. A., Sweeney, W., Wainscoat, R., and Waters, C.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We probe the systematic uncertainties from 113 Type Ia supernovae (SNIa) in the Pan-STARRS1 (PS1) sample along with 197 SN Ia from a combination of low-redshift surveys. The companion paper by Rest et al. (2013) describes the photometric measurements and cosmological inferences from the PS1 sample. The largest systematic uncertainty stems from the photometric calibration of the PS1 and low-z samples. We increase the sample of observed Calspec standards from 7 to 10 used to define the PS1 calibration system. The PS1 and SDSS-II calibration systems are compared and discrepancies up to ~0.02 mag are recovered. We find uncertainties in the proper way to treat intrinsic colors and reddening produce differences in the recovered value of w up to 3%. We estimate masses of host galaxies of PS1 supernovae and detect an insignificant difference in distance residuals of the full sample of 0.037\pm0.031 mag for host galaxies with high and low masses. Assuming flatness in our analysis of only SNe measurements, we find $w = {-1.120^{+0.360}_{-0.206}\textrm{(Stat)} ^{+0.269}_{-0.291}\textrm{(Sys)}}$. With additional constraints from BAO, CMB(Planck) and H0 measurements, we find $w = -1.166^{+0.072}_{-0.069}$ and $\Omega_M=0.280^{+0.013}_{-0.012}$ (statistical and systematic errors added in quadrature). Significance of the inconsistency with $w=-1$ depends on whether we use Planck or WMAP measurements of the CMB: $w_{\textrm{BAO+H0+SN+WMAP}}=-1.124^{+0.083}_{-0.065}$., Comment: 24 pages, 20 figures. Accepted by ApJ
Published: 2013
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150. Cosmological Constraints from Measurements of Type Ia Supernovae discovered during the first 1.5 years of the Pan-STARRS1 Survey

Author: Rest, A., Scolnic, D., Foley, R. J., Huber, M. E., Chornock, R., Narayan, G., Tonry, J. L., Berger, E., Soderberg, A. M., Stubbs, C. W., Riess, A., Kirshner, R. P., Smartt, S. J., Schlafly, E., Rodney, S., Botticella, M. T., Brout, D., Challis, P., Czekala, I., Drout, M., Hudson, M. J., Kotak, R., Leibler, C., Lunnan, R., Marion, G. H., McCrum, M., Milisavljevic, D., Pastorello, A., Sanders, N. E., Smith, K., Stafford, E., Thilker, D., Valenti, S., Wood-Vasey, W. M., Zheng, Z., Burgett, W. S., Chambers, K. C., Denneau, L., Draper, P. W., Flewelling, H., Hodapp, K. W., Kaiser, N., Kudritzki, R. P., Magnier, E. A., Metcalfe, N., Price, P. A., Sweeney, W., Wainscoat, R., and Waters, C.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present griz light curves of 146 spectroscopically confirmed Type Ia Supernovae ($0.03 < z <0.65$) discovered during the first 1.5 years of the Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is determined by a combination of on-site measurements of the instrument response function and observations of spectrophotometric standard stars. We find that the systematic uncertainties in the photometric system are currently 1.2\% without accounting for the uncertainty in the HST Calspec definition of the AB system. A Hubble diagram is constructed with a subset of 113 out of 146 SNe Ia that pass our light curve quality cuts. The cosmological fit to 310 SNe Ia (113 PS1 SNe Ia + 222 light curves from 197 low-z SNe Ia), using only SNe and assuming a constant dark energy equation of state and flatness, yields $w=-1.120^{+0.360}_{-0.206}\textrm{(Stat)} ^{+0.269}_{-0.291}\textrm{(Sys)}$. When combined with BAO+CMB(Planck)+$H_0$, the analysis yields $\Omega_{\rm M}=0.280^{+0.013}_{-0.012}$ and $w=-1.166^{+0.072}_{-0.069}$ including all identified systematics (see also Scolnic et al. 2014). The value of $w$ is inconsistent with the cosmological constant value of $-1$ at the 2.3$\sigma$ level. Tension endures after removing either the BAO or the $H_0$ constraint, though it is strongest when including the $H_0$ constraint. If we include WMAP9 CMB constraints instead of those from Planck, we find $w=-1.124^{+0.083}_{-0.065}$, which diminishes the discord to $<2\sigma$. We cannot conclude whether the tension with flat $\Lambda$CDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full Pan-STARRS1 supernova sample with $\sim\!\!$3 times as many SNe should provide more conclusive results., Comment: 38 pages, 16 figures, 14 tables, ApJ in press
Published: 2013
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