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3,401 results on '"Harding, A K"'

101. Search for extended sources in the Galactic Plane using 6 years of Fermi-Large Area Telescope Pass 8 data above 10 GeV

Author: The Fermi LAT Collaboration, Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Castro, D., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Cheung, C. C., Chiaro, G., Ciprini, S., Cohen, J. M., Costantin, D., Costanza, F., Cutini, S., D'Ammando, F., de Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Green, D., Grenier, I. A., Grondin, M. -H., Guillemot, L., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Horan, D., Hou, X., Jóhannesson, G., Kamae, T., Kuss, M., La Mura, G., Larsson, S., Lemoine-Goumard, M., Li, J., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Malyshev, D., Manfreda, A., Mazziotta, M. N., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paliya, V. S., Paneque, D., Perkins, J. S., Persic, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Porter, T. A., Principe, G., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Reposeur, T., Sgro, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tak, D., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The spatial extension of a gamma-ray source is an essential ingredient to determine its spectral properties as well as its potential multi-wavelength counterpart. The capability to spatially resolve gamma-ray sources is greatly improved by the newly delivered Fermi-Large Area Telescope (LAT) Pass 8 event-level analysis which provides a greater acceptance and an improved point spread function, two crucial factors for the detection of extended sources. Here, we present a complete search for extended sources located within 7 degrees from the Galactic plane, using 6 years of LAT data above 10 GeV. We find 46 extended sources and provide their morphological and spectral characteristics. This constitutes the first catalog of hard LAT extended sources, named the Fermi Galactic Extended Source Catalog, which allows a thorough study of the properties of the Galactic plane in the sub-TeV domain., Comment: 33 pages, 22 figures & 3 tables. Published by The Astrophysical Journal. Available on the Fermi Science Support Center (FSSC) together with the 3FHL catalog
Published: 2017
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102. The effect of an offset polar cap dipolar magnetic field on the modeling of the Vela pulsar's $\gamma$-ray light curves

Author: Barnard, Monica, Venter, Christo, and Harding, Alice K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We performed geometric pulsar light curve modeling using static, retarded vacuum, and offset polar cap (PC) dipole $B$-fields (the latter is characterized by a parameter $\epsilon$), in conjunction with standard two-pole caustic (TPC) and outer gap (OG) emission geometries. The offset-PC dipole $B$-field mimics deviations from the static dipole (which corresponds to $\epsilon=0$). In addition to constant-emissivity geometric models, we also considered a slot gap (SG) $E$-field associated with the offset-PC dipole $B$-field and found that its inclusion leads to qualitatively different light curves. Solving the particle transport equation shows that the particle energy only becomes large enough to yield significant curvature radiation at large altitudes above the stellar surface, given this relatively low $E$-field. Therefore, particles do not always attain the radiation-reaction limit. Our overall optimal light curve fit is for the retarded vacuum dipole field and OG model, at an inclination angle $\alpha=78{_{-1}^{+1}}^{\circ}$ and observer angle $\zeta=69{_{-1}^{+2}}^{\circ}$. For this $B$-field, the TPC model is statistically disfavored compared to the OG model. For the static dipole field, neither model is significantly preferred. We found that smaller values of $\epsilon$ are favored for the offset-PC dipole field when assuming constant emissivity, and larger $\epsilon$ values favored for variable emissivity, but not significantly so. When multiplying the SG $E$-field by a factor of 100, we found improved light curve fits, with $\alpha$ and $\zeta$ being closer to best fits from independent studies, as well as curvature radiation reaction at lower altitudes., Comment: 42 pages, 17 figures
Published: 2017
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103. Implementation of a goodness-of-fit test for finding optimal concurrent radio and {\gamma}-ray pulsar light curves

Author: Seyffert, A. S., Venter, C., Harding, A. K., Allison, J., and Schutte, W. D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Since the launch of the Fermi Large Area Telescope in 2008 the number of known ${\gamma}$-ray pulsars has increased immensely to over 200, many of which are also visible in the radio and X-ray bands. Seyffert et al. (2011) demonstrated how constraints on the viewing geometries of some of these pulsars could be obtained by comparing their observed radio and ${\gamma}$-ray light curves by eye to light curves from geometric models. While these constraints compare reasonably well with those yielded by more rigorous single-wavelength approaches, they are still a somewhat subjective representation of how well the models reproduce the observed radio and ${\gamma}$-ray light curves. Constructing a more rigorous approach is, however, made difficult by the large uncertainties associated with the ${\gamma}$-ray light curves as compared to those associated with the radio light curves. Naively applying a ${\chi}^{2}$-like goodness-of-fit test to both bands invariably results in constraints dictated by the radio light curves. A number of approaches have been proposed to address this issue. In this paper we investigate these approaches and evaluate the results they yield. Based on what we learn, we implement our own version of a goodness-of-fit test, which we then use to investigate the behaviour of the geometric models in multi-dimensional phase space., Comment: 6 pages, 3 figures, Part of the proceedings of the South African Institute of Physics (SAIP) conference for 2015. ISBN: 978-0-620-70714-5
Published: 2016

104. A New, Low Braking Index For the LMC Pulsar B0540-69

Author: Marshall, F. E., Guillemot, L., Harding, A. K., Martin, P., and Smith, D. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the results of a 16-month monitoring campaign using the Swift satellite of PSR B0540-69, a young pulsar in the Large Magellanic Cloud. Phase connection was maintained throughout the campaign so that a reliable ephemeris could be determined, and the length of the campaign is adequate to accurately determine the spin frequency and its first and second derivatives. The braking index is 0.031 +/- 0.013 (90% confidence), a value much lower than previously reported for B0540-69 and almost all other young pulsars. We use data from the extensive monitoring campaign with RXTE to show that timing noise is unlikely to significantly affect the measurement. This is the first measurement of the braking index in the pulsar's recently discovered high spin-down state. We discuss possible mechanisms for producing the low braking index., Comment: 6 pages, 1 figure accepted for publication in ApJ Letters
Published: 2016
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105. Very-high energy emission from pulsars

Author: Breed, M., Venter, C., and Harding, A. K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The vast majority of pulsars detected by the Fermi Large Area Telescope (LAT) display exponentially cutoff spectra with cutoffs falling in a narrow band around a few GeV. Early spectral modelling predicted spectral cutoffs at energies of up to 100 GeV, assuming curvature radiation. It was therefore not expected that pulsars would be visible in the very-high energy (VHE) regime (>100 GeV). The VERITAS announcement of the detection of pulsed emission from the Crab pulsar at energies up to 400 GeV (and now up to 1.5 TeV as detected by MAGIC) therefore raised important questions about our understanding of the electrodynamics and local environment of pulsars. H.E.S.S. has now detected pulsed emission from the Vela pulsar down to tens of GeV, making this the second pulsar detected by a ground-based Cherenkov telescope. Deep upper limits have also been obtained by VERITAS and MAGIC for the Geminga pulsar. We will review the latest developments in VHE pulsar science, including an overview of the latest observations, refinements, and extensions to radiation models and magnetic field structures, and the implementation of new radiation mechanisms. This will assist us in understanding the VHE emission detected from the Crab pulsar, and predicting the level of VHE emission expected from other pulsars, which is very important for the upcoming CTA., Comment: 6 pages, 4 figures, conference proceedings of SAIP 2015
Published: 2016

106. Searching the Gamma-ray Sky for Counterparts to Gravitational Wave Sources: Fermi GBM and LAT Observations of LVT151012 and GW151226

Author: Racusin, J. L., Burns, E., Goldstein, A., Connaughton, V., Wilson-Hodge, C. A., Jenke, P., Blackburn, L., Briggs, M. S., Broida, J., Camp, J., Christensen, N., Hui, C. M., Littenberg, T., Shawhan, P., Singer, L., Veitch, J., Bhat, P. N., Cleveland, W., Fitzpatrick, G., Gibby, M. H., von Kienlin, A., McBreen, S., Mailyan, B., Meegan, C. A., Paciesas, W. S., Preece, R. D., Roberts, O. J., Stanbro, M., Veres, P., Zhang, B. -B., Ackermann, M., Albert, A., Atwood, W. B., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Baring, M. G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bregeon, J., Bruel, P., Buson, S., Caliandro, G. A., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Charles, E., Chiang, J., Ciprini, S., Costanza, F., Cuoco, A., Cutini, S., D'Ammando, F., de Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Drell, P. S., Favuzzi, C., Ferrara, E. C., Focke, W. B., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Gill, R., Giroletti, M., Glanzman, T., Granot, J., Green, D., Grove, J. E., Guillemot, L., Guiriec, S., Harding, A. K., Jogler, T., Johannesson, G., Kamae, T., Kensei, S., Kocevski, D., Kuss, M., Larsson, S., Latronico, L., Li, J., Longo, F., Loparco, F., Lubrano, P., Magill, J. D., Maldera, S., Malyshev, D., McEnery, J. E., Michelson, P. F., Mizuno, T., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Principe, G., Raino, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Parkinson, P. M. Saz, Scargle, J. D., Sgro, C., Simone, D., Siskind, E. J., Smith, D. A., Spada, F., Spinelli, P., Suson, D. J., Tajima, H., Thayer, J. B., Torres, D. F., Troja, E., Uchiyama, Y., Vianello, G., Wood, K. S., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candi- date LVT151012. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for char- acterizing the upper limits across a large area of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, dif- ferences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914., Comment: 27 pages, 1 table, 11 figures, Submitted to ApJ
Published: 2016
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107. 3FGL Demographics Outside the Galactic Plane using Supervised Machine Learning: Pulsar and Dark Matter Subhalo Interpretations

Author: Mirabal, N., Charles, E., Ferrara, E. C., Gonthier, P. L., Harding, A. K., Sánchez-Conde, M. A., and Thompson, D. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Nearly 1/3 of the sources listed in the Third Fermi Large Area Telescope (LAT) catalog (3FGL) remain unassociated. It is possible that predicted and even unanticipated gamma-ray source classes are present in these data waiting to be discovered. Taking advantage of the excellent spectral capabilities achieved by the Fermi LAT, we use machine learning classifiers (Random Forest and XGBoost) to pinpoint potentially novel source classes in the unassociated 3FGL sample outside the Galactic plane. Here we report a total of 34 high-confidence Galactic candidates at |b| > 5 degrees. The currently favored standard astrophysical interpretations for these objects are pulsars or low-luminosity globular clusters hosting millisecond pulsars (MSPs). Yet, these objects could also be interpreted as dark matter annihilation taking place in ultra-faint dwarf galaxies or dark matter subhalos. Unfortunately, Fermi LAT spectra are not sufficient to break degeneracies between the different scenarios. Careful visual inspection of archival optical images reveals no obvious evidence for low-luminosity globular clusters or ultra-faint dwarf galaxies inside the 95% error ellipses. If these are pulsars, this would bring the total number of MSPs at |b| > 5 degrees to 106. We find this number to be in excellent agreement with predictions from a new population synthesis of MSPs that predicts 100-126 high-latitude 3FGL MSPs depending on the choice of high-energy emission model. If, however, these are dark matter substructures, we can place upper limits on the number of Galactic subhalos surviving today and on dark matter annihilation cross sections. These limits are beginning to approach the canonical thermal relic cross section for dark matter particle masses below ~100 GeV in the bottom quark annihilation channel., Comment: 9 pages, 6 figures, 3 tables, accepted for publication in ApJ
Published: 2016
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108. 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. 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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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109. Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope

Author: Ackermann, M., Ajello, M., Albert, A., Atwood, W. B., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Costanza, F., Cuoco, A., Cutini, S., D'Ammando, F., de Angelis, A., de Palma, F., Desiante, R., Digel, S. W., Di Venere, L., Drell, P. S., Favuzzi, C., Fegan, S. J., Focke, W. B., Franckowiak, A., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Harding, A. K., Hewitt, J. W., Horan, D., Hou, X., Iafrate, G., Johannesson, G., Kamae, T., Kuss, M., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J., Maldera, S., Manfreda, A., Mayer, M., Mazziotta, M. N., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Murgia, S., Nuss, E., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Petrosian, V., Piron, F., Pivato, G., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Reposeur, T., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Takahashi, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Winer, B. L., Wood, K. S., Yassine, M., Cerutti, F., Ferrari, A., and Sala, P. R.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract: We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first 7 years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data., Comment: Published by PRD, 16 pages, 11 figures, corresponding authors: F. Loparco and M. N. Mazziotta
Published: 2016
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110. Pulsar emission in the very-high-energy regime

Author: Breed, M., Venter, C., and Harding, A. K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The vast majority of the pulsars detected by the Fermi Large Area Telescope (LAT) display spectra with exponential cutoffs falling in a narrow range around a few GeV. Early spectral modelling predicted spectral cutoff energies of up to 100 GeV. More modern studies estimated spectral cutoff energies in the 1-20 GeV range. It was therefore not expected that pulsars would be visible in the very-high-energy (VHE; >100 GeV) regime. The VERITAS detection (confirmed by MAGIC) of pulsed emission from the Crab pulsar up to 400 GeV (and now possibly up to 1 TeV) therefore raised important questions about our understanding of the electrodynamics and local environment of pulsars. H.E.S.S. has now detected pulsed emission from the Vela pulsar in the 20-120 GeV range, making this the second pulsar detected by a ground-based Cherenkov telescope. We will review the latest developments in VHE pulsar science, including an overview of recent observations and refinements to radiation models and magnetic field structures. This will assist us in interpreting the VHE emission detected from the Crab and Vela pulsars, and predicting the level of VHE emission expected from other pulsars, which will be very important for the upcoming CTA., Comment: 10 pages, 5 figures, "To appear in the Proceedings of the 3rd Annual Conference on High Energy Astrophysics in Southern Africa (HEASA2015), 18-20 June 2015, Johannesburg, South Africa, Eds. M. Boettcher, D. Buckley, S. Colafrancesco, P. Meintjes and S. Razzaque."
Published: 2016

111. A Systematic Review and Meta-analysis of Adjuncts to Minimally Invasive Treatment of Urethral Stricture in Men

Author: Pang, Karl H., Chapple, Christopher R., Chatters, Robin, Downey, Alison P., Harding, Christopher K., Hind, Daniel, Watkin, Nick, and Osman, Nadir I.
Published: 2021
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112. 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. 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C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Gomez-Vargas, G. A., Green, D., Grenier, I. A., Grove, J. E., Guiriec, S., Hadasch, D., Harding, A. K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Jogler, T., Jóhannesson, G., Johnson, A. S., Kensei, S., Kocevski, D., Kuss, M., La Mura, G., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J., Maldera, S., Manfreda, A., Marelli, M., Mayer, M., Mazziotta, M. N., McEnery, J. E., Meyer, M., Michelson, P. F., Mirabal, N., Mizuno, T., Moiseev, A. A., Monzani, M. E., Moretti, E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Racusin, J. L., Rainò, S., Rando, R., Razzaque, S., Reimer, A., Reimer, O., Salvetti, D., Parkinson, P. M. Saz, Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Torres, D. F., Troja, E., Uchiyama, Y., Venters, T. M., Vianello, G., Wood, K. S., Wood, M., Zhu, S., Zimmer, S., Brocato, E., Cappellaro, E., Covino, S., Grado, A., Nicastro, L., Palazzi, E., Pian, E., Amati, L., Antonelli, L. A., Capaccioli, M., D'Avanzo, P., D'Elia, V., Getman, F., Giuffrida, G., Iannicola, G., Limatola, L., Lisi, M., Marinoni, S., Marrese, P., Melandri, A., Piranomonte, S., Possenti, A., Pulone, L., Rossi, A., Stamerra, A., Stella, L., Testa, V., Tomasella, L., Yang, S., Bazzano, A., Bozzo, E., Brandt, S., Courvoisier, T. J. -L., Ferrigno, C., Hanlon, L., Kuulkers, E., Laurent, P., Mereghetti, S., Roques, J. P., Savchenko, V., Ubertini, P., Kasliwal, M. M., Singer, L. P., Cao, Y., Duggan, G., Kulkarni, S. R., Bhalerao, V., Miller, A. A., Barlow, T., Bellm, E., Manulis, I., Rana, J., Laher, R., Masci, F., Surace, J., Rebbapragada, U., Van Sistine, A., Sesar, B., Perley, D., Ferreti, R., Prince, T., Kendrick, R., Horesh, A., Hurley, K., Golenetskii, S. V., Aptekar, R. L., Frederiks, D. D., Svinkin, D. S., Rau, A., Zhang, X., Smith, D. M., Cline, T., Krimm, H., Abe, F., Doi, M., Fujisawa, K., Kawabata, K. S., Morokuma, T., Motohara, K., Tanaka, M., Ohta, K., Yanagisawa, K., Yoshida, M., Baltay, C., Rabinowitz, D., Ellman, N., Rostami, S., Bersier, D. F., Bode, M. F., Collins, C. A., Copperwheat, C. M., Darnley, M. J., Galloway, D. K., Gomboc, A., Kobayashi, S., Mazzali, P., Mundell, C. G., Piascik, A. S., Pollacco, Don, Steele, I. A., Ulaczyk, K., Broderick, J. W., Fender, R. P., Jonker, P. G., Rowlinson, A., Stappers, B. W., Wijers, R. A. M. J., Lipunov, V., Gorbovskoy, E., Tyurina, N., Kornilov, V., Balanutsa, P., Kuznetsov, A., Buckley, D., Rebolo, R., Serra-Ricart, M., Israelian, G., Budnev, N. M., Gress, O., Ivanov, K., Poleshuk, V., Tlatov, A., Yurkov, V., Kawai, N., Serino, M., Negoro, H., Nakahira, S., Mihara, T., Tomida, H., Ueno, S., Tsunemi, H., Matsuoka, M., Croft, S., Feng, L., Franzen, T. M. O., Gaensler, B. M., Johnston-Hollitt, M., Kaplan, D. L., Morales, M. F., Tingay, S. J., Wayth, R. B., Williams, A., Smartt, S. J., Chambers, K. C., Smith, K. W., Huber, M. E., Young, D. R., Wright, D. E., Schultz, A., Denneau, L., Flewelling, H., Magnier, E. A., Primak, N., Rest, A., Sherstyuk, A., Stalder, B., Stubbs, C. W., Tonry, J., Waters, C., Willman, M., E., F. Olivares, Campbell, H., Kotak, R., Sollerman, J., Smith, M., Dennefeld, M., Anderson, J. P., Botticella, M. T., Chen, T. -W., Valle, M. D., Elias-Rosa, N., Fraser, M., Inserra, C., Kankare, E., Kupfer, T., Harmanen, J., Galbany, L., Guillou, L. Le, Lyman, J. D., Maguire, K., Mitra, A., Nicholl, M., Razza, A., Terreran, G., Valenti, S., Gal-Yam, A., Ćwiek, A., Ćwiok, M., Mankiewicz, L., Opiela, R., Zaremba, M., Żarnecki, A. F., Onken, C. A., Scalzo, R. A., Schmidt, B. P., Wolf, C., Yuan, F., Evans, P. A., Kennea, J. A., Burrows, D. N., Campana, S., Cenko, S. B., Marshall, F. E., Nousek, J., O'Brien, P., Osborne, J. P., Palmer, D., Perri, M., Siegel, M., Tagliaferri, G., Klotz, A., Turpin, D., Laugier, R., Beroiz, M., Peñuela, T., Macri, L. M., Oelkers, R. J., Lambas, D. G., Vrech, R., Cabral, J., Colazo, C., Dominguez, M., Sanchez, B., Gurovich, S., Lares, M., Marshall, J. L., DePoy, D. L., Padilla, N., Pereyra, N. A., Benacquista, M., Tanvir, N. R., Wiersema, K., Levan, A. J., Steeghs, D., Hjorth, J., Fynbo, J. P. U., Malesani, D., Milvang-Jensen, B., Watson, D., Irwin, M., Fernandez, C. G., McMahon, R. G., Banerji, M., Gonzalez-Solares, E., Schulze, S., Postigo, A. de U., Thoene, C. C., Cano, Z., and Rosswog, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams., Comment: For Supplement, see https://arxiv.org/abs/1604.07864
Published: 2016
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113. Development of the Model of Galactic Interstellar Emission for Standard Point-Source Analysis of Fermi Large Area Telescope Data

Author: Acero, F., Ackermann, M., Ajello, M., Albert, A., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Conrad, J., Cuoco, A., Cutini, S., D'Ammando, F., de Angelis, A., de Palma, F., Desiante, R., Digel, S. W., Di Venere, L., Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Franckowiak, A., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Guiriec, S., Hadasch, D., Harding, A. K., Hayashi, K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Hou, X., Jogler, T., Jóhannesson, G., Kamae, T., Kuss, M., Landriu, D., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Maldera, S., Malyshev, D., Manfreda, A., Martin, P., Mayer, M., Mazziotta, M. N., McEnery, J. E., Michelson, P. F., Mirabal, N., Mizuno, T., Monzani, M. E., Morselli, A., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Pesce-Rollins, M., Piron, F., Pivato, G., Rainò, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Remy, Q., Renault, N., Sánchez-Conde, M., Schaal, M., Schulz, A., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Strong, A. W., Suson, D. J., Tajima, H., Takahashi, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Tinivella, M., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Werner, M., Wood, K. S., Wood, M., Zaharijas, G., and Zimmer, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Most of the celestial gamma rays detected by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point and extended source studies rely on the modeling of this diffuse emission for accurate characterization. We describe here the development of the Galactic Interstellar Emission Model (GIEM) that is the standard adopted by the LAT Collaboration and is publicly available. The model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse Compton emission produced in the Galaxy. We also include in the GIEM large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20 degrees and we observe an enhanced emission toward their base extending in the North and South Galactic direction and located within 4 degrees of the Galactic Center., Comment: Accepted for publication in ApJS
Published: 2016
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114. The Aid of Optical Studies in Understanding Millisecond Pulsar Binaries

Author: Wadiasingh, Zorawar, Harding, Alice K., Venter, Christo, and Boettcher, Markus
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: A large number of new "black widow" and "redback" energetic millisecond pulsars with irradiated stellar companions have been discovered through radio and optical searches of unidentified \textit{Fermi} sources. Synchrotron emission, from particles accelerated up to several TeV in the intrabinary shock, exhibits modulation at the binary orbital period. Our simulated double-peaked X-ray light curves modulated at the orbital period, produced by relativistic Doppler-boosting along the intrabinary shock, are found to qualitatively match those observed in many sources. In this model, redbacks and transitional pulsar systems where the double-peaked X-ray light curve is observed at inferior conjunction have intrinsically different shock geometry than other millisecond pulsar binaries where the light curve is centered at superior conjunction. We discuss, and advocate, how current and future optical observations may aid in constraining the emission geometry, intrabinary shock and the unknown physics of pulsar winds., Comment: 7 pages, 1 figure. Conference proceedings of SALT Science Conference 2015. Accepted for publication in PoS SSC2015
Published: 2016

115. Young and middle age pulsar light-curve morphology: Comparison of Fermi observations with gamma-ray and radio emission geometries

Author: Pierbattista, M., Harding, A. K., Gonthier, P. L., and Grenier, I. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Thanks to the huge amount of gamma-ray pulsar photons collected by the Fermi Large Area Telescope since June 2008, it is now possible to constrain gamma-ray geometrical models by comparing simulated and observed light-curve morphological characteristics. We assumed vacuum-retarded dipole pulsar magnetic field and tested simulated and observed morphological light-curve characteristics in the framework of two pole emission geometries, Polar Cap (PC), radio, and Slot Gap (SG), and Outer Gap (OG)/One Pole Caustic (OPC) emission geometries. We compared simulated and observed/estimated light-curve morphological parameters as a function of observable and non-observable pulsar parameters. The PC model gives the poorest description of the LAT pulsar light-curve morphology. The OPC best explains both the observed gamma-ray peak multiplicity and shape classes. The OPC and SG models describe the observed gamma-ray peak-separation distribution for low- and high-peak separations, respectively. This suggests that the OPC geometry best explains the single-peak structure but does not manage to describe the widely separated peaks predicted in the framework of the SG model as the emission from the two magnetic hemispheres. The OPC radio-lag distribution shows higher agreement with observations suggesting that assuming polar radio emission, the gamma-ray emission regions are likely to be located in the outer magnetosphere. The larger agreement between simulated and LAT estimations in the framework of the OPC suggests that the OPC model best predicts the observed variety of profile shapes. The larger agreement between observations and the OPC model jointly with the need to explain the abundant 0.5 separated peaks with two-pole emission geometries, calls for thin OPC gaps to explain the single-peak geometry but highlights the need of two-pole caustic emission geometry to explain widely separated peaks., Comment: 28 pages, 20 figures, 8 tables; accepted for publication in Astronomy and Astrophysics
Published: 2016
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116. CHIMERA: a wide-field, multi-color, high-speed photometer at the prime focus of the Hale telescope

Author: Harding, Leon K., Hallinan, Gregg, Milburn, Jennifer, Gardner, Paul, Konidaris, Nick, Singh, Navtej, Shao, Michael, Sandhu, Jagmit, Kyne, Gillian, and Schlichting, Hilke E.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Caltech HIgh-speed Multi-color camERA (CHIMERA) is a new instrument that has been developed for use at the prime focus of the Hale 200-inch telescope. Simultaneous optical imaging in two bands is enabled by a dichroic beam splitter centered at 567 nm, with Sloan u' and g' bands available on the blue arm and Sloan r', i' and z_s' bands available on the red arm. Additional narrow-band filters will also become available as required. An Electron Multiplying CCD (EMCCD) detector is employed for both optical channels, each capable of simultaneously delivering sub-electron effective read noise under multiplication gain and frame rates of up to 26 fps full frame (several 1000 fps windowed), over a fully corrected 5 x 5 arcmin field of view. CHIMERA was primarily developed to enable the characterization of the size distribution of sub-km Kuiper Belt Objects via stellar occultation, a science case that motivates the frame-rate, the simultaneous multi-color imaging and the wide field of view of the instrument. In addition, it also has unique capability in the detection of faint near-Earth asteroids and will be used for the monitoring of short duration transient and periodic sources, particularly those discovered by the intermediate Palomar Transient Factory (iPTF), and the upcoming Zwicky Transient Facility (ZTF)., Comment: Accepted to Mon. Not. R. Astron. Soc. (MNRAS), 15 pages, 9 figures, 3 tables
Published: 2016
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117. Technology advancement of the CCD201-20 EMCCD for the WFIRST coronagraph instrument: sensor characterization and radiation damage

Author: Harding, Leon K., Demers, Richard T., Hoenk, Michael, Peddada, Pavani, Nemati, Bijan, Cherng, Michael, Michaels, Darren, Neat, Leo S., Loc, Anthony, Bush, Nathan, Hall, David, Murray, Neil, Gow, Jason, Burgon, Ross, Holland, Andrew, Reinheimer, Alice, Jorden, Paul R., and Jordand, Douglas
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset (WFIRST-AFTA) mission is a 2.4-m class space telescope that will be used across a swath of astrophysical research domains. JPL will provide a high-contrast imaging coronagraph instrument - one of two major astronomical instruments. In order to achieve the low noise performance required to detect planets under extremely low flux conditions, the electron multiplying charge-coupled device (EMCCD) has been baselined for both of the coronagraph's sensors - the imaging camera and integral field spectrograph. JPL has established an EMCCD test laboratory in order to advance EMCCD maturity to technology readiness level-6. This plan incorporates full sensor characterization, including read noise, dark current, and clock-induced charge. In addition, by considering the unique challenges of the WFIRST space environment, degradation to the sensor's charge transfer efficiency will be assessed, as a result of damage from high-energy particles such as protons, electrons, and cosmic rays. Science-grade CCD201-20 EMCCDs have been irradiated to a proton fluence that reflects the projected WFIRST orbit. Performance degradation due to radiation displacement damage is reported, which is the first such study for a CCD201-20 that replicates the WFIRST conditions. In addition, techniques intended to identify and mitigate radiation-induced electron trapping, such as trap pumping, custom clocking, and thermal cycling, are discussed., Comment: Published in the J. Astron. Telesc. Instrum. Syst. 2(1), 011007 (2016), 31 pages, 18 figures, 9 tables
Published: 2016
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118. High Energy Emission from Black Widows and Redbacks

Author: Wadiasingh, Zorawar, Harding, Alice K., Venter, Christo, and Böttcher, Markus
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: A large number of new black widow and redback energetic millisecond pulsars with irradiated stellar companions have been discovered through radio searches of unidentified \emph{Fermi} sources. We construct a 3D emission model of these systems to predict the high-energy emission components from particles accelerated to several TeV in the intrabinary shocks, and its predicted modulation at the binary orbital period. Synchrotron emission is expected at X-ray energies and such modulated emission has already been detected by \emph{Chandra} and \emph{XMM-Newton} in some systems. Synchrotron and inverse Compton emission from relativistic particles in the pulsar wind and intrabinary shock can probe the unknown physics of pulsar winds and relativistic shock acceleration in these compact binaries. Orbitally-modulated emission in the GeV and TeV bands may be detectable under some favorable conditions., Comment: 8 pages, 3 figures. Proceedings of HEASA 2015, June 18-20, 2015. To be published in PoS
Published: 2015

119. The 1st Fermi Lat Supernova Remnant Catalog

Author: Acero, Fabio, Ackermann, Markus, Ajello, Marco, Baldini, Luca, Ballet, Jean, Barbiellini, Guido, Bastieri, Denis, Bellazzini, Ronaldo, Bissaldi, E., Blandford, Roger, Bloom, E. D., Bonino, Raffaella, Bottacini, Eugenio, Bregeon, J., Bruel, Philippe, Buehler, Rolf, Buson, S., Caliandro, G. A., Cameron, Rob A., Caputo, R, Caragiulo, Micaela, Caraveo, Patrizia A., Casandjian, Jean Marc, Cavazzuti, Elisabetta, Cecchi, Claudia, Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, Stefano, Claus, R., Cohen, J. M., Cohen-Tanugi, Johann, Cominsky, L. R., Condon, B., Conrad, Jan, Cutini, S., D'Ammando, F., Angelis, A., Palma, F., Desiante, Rachele, Digel, S. W., Venere, L., Drell, Persis S, Drlica-Wagner, Alex, Favuzzi, C., Ferrara, E. C., Franckowiak, Anna, Fukazawa, Prof. Yasushi, Funk, Prof. Stefan, Fusco, P., Gargano, Fabio, Gasparrini, Dario, Giglietto, Nicola, Giommi, Paolo, Giordano, Francesco, Giroletti, Marcello, Glanzman, Tom, Godfrey, Gary, Gomez-Vargas, G A., Grenier, I. A., Grondin, M. -H., Guillemot, L., Guiriec, Sylvain, Gustafsson, M, Hadasch, D., Harding, A. K., Hayashida, M., Hays, Elizabeth, Hewitt, J. W., Hill, A. B., Horan, Deirdre, Hou, X., Iafrate, Giulia, Jogler, Tobias, J'ohannesson, G., Johnson, Anthony S., Kamae, T., Katagiri, Hideaki, Kataoka, Prof. Jun, Katsuta, Junichiro, Kerr, Matthew, Knodlseder, J., Kocevski, Prof. Dale, Kuss, M., Laffon, Helene, Lande, J., Larsson, S., Latronico, Luca, Lemoine-Goumard, Marianne, Li, J., Li, L., Longo, Francesco, Loparco, Francesco, Lovellette, Michael N., Lubrano, Pasquale, Magill, J., Maldera, S., Marelli, Martino, Mayer, Michael, Mazziotta, M. N., Michelson, Peter F., Mitthumsiri, Warit, Mizuno, Tsunefumi, Moiseev, Alexander A., Monzani, Maria Elena, Moretti, E., Morselli, Aldo, Moskalenko, Igor V., Murgia, Prof. Simona, Nemmen, Prof. Rodrigo, Nuss, Eric, Ohsugi, Takashi, Omodei, Nicola, Orienti, Monica, Orlando, Elena, Ormes, Jonathan F., Paneque, David, Perkins, J. S., Pesce-Rollins, Melissa, Petrosian, Prof. Vahe', Piron, Frederic, Pivato, Giovanna, Porter, Troy, Rain`o, S., Rando, Riccardo, Razzano, Massimiliano, Razzaque, Soebur, Reimer, Anita, Reimer, Prof. Olaf, Renaud, Matthieu, Reposeur, Thierry, Rousseau, Mr. Romain, Parkinson, P. M., Schmid, J., Schulz, A., Sgr`o, C., Siskind, Eric J, Spada, Francesca, Spandre, Gloria, Spinelli, Paolo, Strong, Andrew W., Suson, Daniel, Tajima, Hiro, Takahashi, Hiromitsu, Tanaka, T., Thayer, Jana B., Thompson, D. J., Tibaldo, L., Tibolla, Omar, Torres, Prof. Diego F., Tosti, Gino, Troja, Eleonora, Uchiyama, Yasunobu, Vianello, G., Wells, B., Wood, Kent, Wood, M., Yassine, Manal, and Zimmer, Stephan
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope. Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude, allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, demonstrates the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays., Comment: Resubmitted to ApJS
Published: 2015
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120. Gamma-ray pulsars: a gold mine

Author: Grenier, Isabelle A. and Harding, Alice K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The most energetic neutron stars, powered by their rotation, are capable of producing pulsed radiation from the radio up to gamma rays with nearly TeV energies. These pulsars are part of the universe of energetic and powerful particle accelerators, using their uniquely fast rotation and formidable magnetic fields to accelerate particles to ultra-relativistic speed. The extreme properties of these stars provide an excellent testing ground, beyond Earth experience, for nuclear, gravitational, and quantum-electrodynamical physics. A wealth of gamma-ray pulsars has recently been discovered with the Fermi Gamma-Ray Space Telescope. The energetic gamma rays enable us to probe the magnetospheres of neutron stars and particle acceleration in this exotic environment. We review the latest developments in this field, beginning with a brief overview of the properties and mysteries of rotation-powered pulsars, and then discussing gamma-ray observations and magnetospheric models in more detail., Comment: 24-page review for the book 'High-energy gamma-ray astronomy', eds. B. Degrange, G. Fontaine, volume 1, Comptes Rendus Physique, Elsevier, C. R. Physique 16, 2015
Published: 2015
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121. Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113

Author: The Fermi LAT collaboration, Ackermann, M., Ajello, M., Albert, A., Atwood, W. B., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Cohen-Tanugi, J., Conrad, J., Cutini, S., D'Ammando, F., De Angelis, A., De Palma, F., Desiante, R., Di Venere, L., Dominguez, A., Drell, P. S., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Fuhrmann, L., Fukazawa, Y., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Godfrey, G., Green, D., Grenier, I. A., Grove, J. E., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Jogler, T., Johannesson, G., Johnson, A. S., Kamae, T., Kuss, M., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lott, B., Lovellette, M. N., Lubrano, P., Magill, J., Maldera, S., Manfreda, A., Max-Moerbeck, W., Mayer, M., Mazziotta, M. N., Mcenery, J. E., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nuss, E., Ohno, M., Ohsugi, T., Ojha, R., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Pearson, T. J., Perkins, J. S., Perri, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Pivato, G., Porter, T. A., Raino', S., Rando, R., Razzano, M., Readhead, A., Reimer, A., Reimer, O., Schulz, A., Sgro', C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Takahashi, H., Thayer, J. B., Thompson, D. J., Tibaldo, L., Torres, D. F., Tosti, G., Troja, E., Uchiyama, Y., Vianello, G., Wood, K. S., Wood, M., Zimmer, S., Berdyugin, A., Corbet, R. H. D., Hovatta, T., Lindfors, E., Nilsson, K., Reinthal, R., Sillanpaa, A., Stamerra, A., Takalo, L. O., and Valtonen, M. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report for the first time a gamma-ray and multi-wavelength nearly-periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope (LAT) we have discovered an apparent quasi-periodicity in the gamma-ray flux (E >100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 +/-0.08 year-period gamma-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle appearing in ~10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity., Comment: 8 pages, 5 figures. Accepted to The Astrophysical Journal Letters. Corresponding authors: S. Ciprini (ASDC/INFN), S. Cutini (ASDC/INFN), S. Larsson (Stockholm Univ/KTH), A. Stamerra (INAF/SNS), D. J. Thompson (NASA GSFC)
Published: 2015
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122. Synchrotron Self-Compton Emission from the Crab and Other Pulsars

Author: Harding, Alice K. and Kalapotharakos, Constantinos
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Results of a simulation of synchrotron-self Compton (SSC) emission from a rotation-powered pulsar are presented. The radiating particles are assumed to be both accelerated primary electrons and a spectrum of electron-positron pairs produced in cascades near the polar cap. They follow trajectories in a slot gap using 3D force-free magnetic field geometry, gaining pitch angles through resonant cyclotron absorption of radio photons, radiating and scattering synchrotron emission at high altitudes out to and beyond the light cylinder. Full angular dependence of the synchrotron photon density is simulated in the scattering and all processes are treated in the inertial observer frame. Spectra for the Crab and Vela pulsars as well as two energetic millisecond pulsars, B1821-24 and B1937+21 are simulated using this model. The simulation of the Crab pulsar radiation can reproduce both the flux level and the shape of the observed optical to hard X-ray emission assuming a pair multiplicity of $M_+ = 3 \times 10^5$, as well as the very-high-energy emission above 50 GeV detected by MAGIC and VERITAS, with both the synchrotron and SSC components reflecting the shape of the pair spectrum. Simulations of Vela, B1821$-$24 and B1937+21, for $M_+$ up to $10^5$, do not produce pair SSC emission that is detectable by current telescopes, indicating that only Crab-like pulsars produce significant SSC components. The pair synchrotron emission matches the observed X-ray spectrum of the millisecond pulsars and the predicted peak of this emission at 1 - 10 MeV would be detectable with planned Compton telescopes., Comment: 35 pages, 8 figures, accepted for publication in ApJ
Published: 2015
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123. The millisecond pulsar contribution to the rising positron fraction

Author: Venter, Christo, Kopp, Andreas, Harding, Alice K, Gonthier, Peter L, and Buesching, Ingo
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Pair cascades from millisecond pulsars (MSPs) may be a primary source of Galactic electrons and positrons that contribute to the increase in positron flux above 10 GeV as observed by PAMELA and AMS-02. The Fermi Large Area Telescope (LAT) has increased the number of detected gamma-ray MSPs tremendously. Light curve modelling furthermore favours abundant pair production in MSP magnetospheres, so that models of primary cosmic-ray positrons from pulsars should include the contribution from the larger numbers of MSPs and their potentially higher positron output per source. We model the contribution of Galactic MSPs to the terrestrial cosmic-ray electron / positron flux by using a population synthesis code to predict the source properties of present-day MSPs. We simulate pair spectra assuming an offset-dipole magnetic field which boosts pair creation rates. We also consider positrons and electrons that have additionally been accelerated to very high energies in the strong intrabinary shocks in black widow (BW) and redback (RB) binary systems. We transport these particles to Earth by calculating their diffusion and the radiative energy losses they suffer in the Galaxy using a model. Our model particle flux increases for non-zero offsets of the magnetic polar caps. We find that pair cascades from MSP magnetospheres contribute only modestly around a few tens of GeV to the measured fluxes. BW and RB fluxes may reach a few tens of percent of the observed flux up to a few TeV. Future observations should constrain the source properties in this case., Comment: 8 pages, 2 figures, presented at the 34th ICRC, the Hague, the Netherlands
Published: 2015

124. PSR J1906+0722: An Elusive Gamma-ray Pulsar

Author: Clark, C. J., Pletsch, H. J., Wu, J., Guillemot, L., Ackermann, M., Allen, B., de Angelis, A., Aulbert, C., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bock, O., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cecchi, C., Champion, D. J., Charles, E., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Cuéllar, A., Cutini, S., D'Ammando, F., Desiante, R., Drell, P. S., Eggenstein, H. B., Favuzzi, C., Fehrmann, H., Ferrara, E. C., Focke, W. B., Franckowiak, A., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Harding, A. K., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Hou, X., Jogler, T., Johnson, A. S., Jóhannesson, G., Kramer, M., Krauss, F., Kuss, M., Laffon, H., Larsson, S., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Machenschalk, B., Manfreda, A., Marelli, M., Mayer, M., Mazziotta, M. N., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nuss, E., Ohsugi, T., Orienti, M., Orlando, E., de Palma, F., Paneque, D., Pesce-Rollins, M., Piron, F., Pivato, G., Rainò, S., Rando, R., Razzano, M., Reimer, A., Parkinson, P. M. Saz, Schaal, M., Schulz, A., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Takahashi, H., Thayer, J. B., Tibaldo, L., Torne, P., Torres, D. F., Tosti, G., Troja, E., Vianello, G., Wood, K. S., Wood, M., and Yassine, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of PSR J1906+0722, a gamma-ray pulsar detected as part of a blind survey of unidentified Fermi Large Area Telescope (LAT) sources being carried out on the volunteer distributed computing system, Einstein@Home. This newly discovered pulsar previously appeared as the most significant remaining unidentified gamma-ray source without a known association in the second Fermi-LAT source catalog (2FGL) and was among the top ten most significant unassociated sources in the recent third catalog (3FGL). PSR J1906+0722 is a young, energetic, isolated pulsar, with a spin frequency of $8.9$ Hz, a characteristic age of $49$ kyr, and spin-down power $1.0 \times 10^{36}$ erg s$^{-1}$. In 2009 August it suffered one of the largest glitches detected from a gamma-ray pulsar ($\Delta f / f \approx 4.5\times10^{-6}$). Remaining undetected in dedicated radio follow-up observations, the pulsar is likely radio-quiet. An off-pulse analysis of the gamma-ray flux from the location of PSR J1906+0722 revealed the presence of an additional nearby source, which may be emission from the interaction between a neighboring supernova remnant and a molecular cloud. We discuss possible effects which may have hindered the detection of PSR J1906+0722 in previous searches and describe the methods by which these effects were mitigated in this survey. We also demonstrate the use of advanced timing methods for estimating the positional, spin and glitch parameters of difficult-to-time pulsars such as this., Comment: 7 pages, 4 figures, accepted for publication in Astrophysical Journal Letters
Published: 2015
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125. Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence

Author: Hallinan, G., Littlefair, S. P., Cotter, G., Bourke, S., Harding, L. K., Pineda, J. S., Butler, R. P., Golden, A., Basri, G., Doyle, J. G., Kao, M. M., Berdyugina, S. V., Kuznetsov, A., Rupen, M. P., and Antonova, A.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere. Here we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower atmospheres, these aurorae are powered by processes originating much further out in the magnetosphere of the dwarf star that couple energy into the lower atmosphere. The dissipated power is at least four orders of magnitude larger than what is produced in the Jovian magnetosphere, revealing aurorae to be a potentially ubiquitous signature of large-scale magnetospheres that can scale to luminosities far greater than those observed in our Solar System. These magnetospheric current systems may also play a part in powering some of the weather phenomena reported on brown dwarfs., Comment: Accepted for publication in the 30 July 2015 issue of Nature. 27 pages, 2 figures, 2 extended data figures
Published: 2015
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126. Discovery of a Spin-Down State Change in the LMC Pulsar B0540-69

Author: Marshall, F. E., Guillemot, L., Harding, A. K., Martin, P., and Smith, D. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of a large, sudden, and persistent increase in the spin-down rate of B0540-69, a young pulsar in the Large Magellanic Cloud, using observations from the Swift and RXTE satellites. The relative increase in the spin-down rate of 36% is unprecedented for B0540-69. No accompanying change in the spin rate is seen, and no change is seen in the pulsed X-ray emission from B0540-69 following the change in the spin-down rate. Such large relative changes in the spin-down rate are seen in the recently discovered class of 'intermittent pulsars', and we compare the properties of B0540-69 to such pulsars. We consider possible changes in the magnetosphere of the pulsar that could cause such a large change in the spin-down rate., Comment: 6 pages, 2 figures, accepted for publication in ApJ Letters
Published: 2015
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127. Search for Early Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi LAT

Author: Ackermann, M., Arcavi, I., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Cutini, S., D'Ammando, F., de Angelis, A., de Palma, F., Desiante, R., Di Venere, L., Drell, P. S., Favuzzi, C., Fegan, S. J., Franckowiak, A., Funk, S., Fusco, P., Gal-Yam, A., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Grenier, I. A., Grove, J. E., Guiriec, S., Harding, A. K., Hayashi, K., Hewitt, J. W., Hill, A. B., Horan, D., Jogler, T., Jóhannesson, G., Kocevski, D., Kuss, M., Larsson, S., Lashner, J., Latronico, L., Li, J., Li, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Malyshev, D., Mayer, M., Mazziotta, M. N., McEnery, J. E., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Murase, K., Nugent, P., Nuss, E., Ofek, E., Ohsugi, T., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Pesce-Rollins, M., Piron, F., Pivato, G., Rainò, S., Rando, R., Razzano, M., Reimer, A., Reimer, O., Schulz, A., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Suson, D. J., Takahashi, H., Thayer, J. B., Tibaldo, L., Torres, D. F., Troja, E., Vianello, G., Werner, M., Wood, K. S., and Wood, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. We perform the first systematic search for gamma-ray emission in Fermi LAT data in the energy range from 100 MeV to 300 GeV from the ensemble of 147 SNe Type IIn exploding in dense CSM. We search for a gamma-ray excess at each SNe location in a one year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months and 3 months). For the most promising source of the sample, SN 2010jl (PTF10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in gamma rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we derive limits on the gamma-ray luminosity and the ratio of gamma-ray-to-optical luminosity ratio as a function of the index of the proton injection spectrum assuming a generic gamma-ray production model. Furthermore, we present detailed flux predictions based on multi-wavelength observations and the corresponding flux upper limit at 95% confidence level (CL) for the source SN 2010jl (PTF10aaxf)., Comment: Accepted for publication in ApJ. Corresponding author: A. Franckowiak (afrancko@slac.stanford.edu), updated author list and acknowledgements
Published: 2015
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128. Cosmic-ray positrons from millisecond pulsars

Author: Venter, C., Kopp, A., Harding, A. K., Gonthier, P. L., and Büsching, I.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Observations by the Fermi Large Area Telescope of gamma-ray millisecond pulsar light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ~10 GeV. Fermi has also uncovered many new millisecond pulsars, impacting Galactic stellar population models. We investigate the contribution of Galactic millisecond pulsars to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day millisecond pulsars. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow and redback systems. Since millisecond pulsars are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of millisecond pulsars are only modest contributors around a few tens of GeV to the lepton fluxes measured by AMS-02, PAMELA, and Fermi, after which this component cuts off. The contribution by black widows and redbacks may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters., Comment: 71 pages, 22 figures, 2 tables, accepted for publication in ApJ
Published: 2015
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129. The effect of an offset-dipole magnetic field on the Vela pulsar's gamma-ray light curves

Author: Breed, M., Venter, C., Harding, A. K., and Johnson, T. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Over the past six years, the Fermi Large Area Telescope has detected more than 150 gamma-ray pulsars, discovering a variety of light curve trends and classes. Such diversity hints at distinct underlying magnetospheric and/or emission geometries. We implemented an offset-dipole magnetic field, with an offset characterised by parameters epsilon and magnetic azimuthal angle, in an existing geometric pulsar modelling code which already includes static and retarded vacuum dipole fields. We use these different magnetic field solutions in conjunction with standard emission geometries, namely the two-pole caustic and outer gap models (the latter only for non-offset dipoles), and construct intensity maps and light curves for several pulsar parameters. We compare our model light curves to the Vela data from the second pulsar catalogue of Fermi. We use a refined chi-square grid search method for finding best-fit light curves for each of the different models. Our best fit is for the retarded vacuum dipole field and the outer gap model., Comment: 6 pages, 5 figures, 1 table
Published: 2015

130. On the polar cap cascade pair multiplicity of young pulsars

Author: Timokhin, A. N. and Harding, A. K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ~few x 10^5. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae., Comment: 27 pages, 23 figures; ApJ, 810, 144 (2015)
Published: 2015
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131. Testing dissipative magnetosphere model light curves and spectra with FERMI pulsars

Author: Brambilla, Gabriele, Kalapotharakos, Constantinos, Harding, Alice K., and Kazanas, Demosthenes
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We explore the emission properties of a dissipative pulsar magnetosphere model introduced by Kalapotharakos et al. (2014), comparing its high energy light curves and spectra, due to curvature radiation, with data collected by the Fermi LAT. The magnetosphere structure is assumed to be near the force-free solution. The accelerating electric field, inside the light-cylinder, is assumed to be negligible, while outside the light-cylinder it rescales with a finite conductivity ({\sigma}). In our approach we calculate the corresponding high energy emission by integrating the trajectories of test particles that originate from the stellar surface, taking into account both the accelerating electric field components and the radiation reaction forces. First we explore the parameter space assuming different value sets for the stellar magnetic field, stellar period, and conductivity. We show that the general properties of the model are in a good agreement with observed emission characteristics of young {\gamma}-ray pulsars, including features of the phase resolved spectra. Second we find model parameters that fit each pulsar belonging to a group of eight bright pulsars that have a published phase-resolved spectrum. The {\sigma} values that best describe each of the pulsars in this group show an increase with the spin-down rate $(\dot{E})$ and a decrease with the pulsar age, expected if pair cascades are providing the magnetospheric conductivity. Finally, we explore the limits of our analysis and suggest future directions for improving such models., Comment: 17 pages, 14 figures
Published: 2015
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132. Discovery of Gamma-ray Pulsations from the Transitional Redback PSR J1227-4853

Author: Johnson, T. J., Ray, P. S., Roy, J., Cheung, C. C., Harding, A. K., Pletsch, H. J., Fort, S., Camilo, F., Deneva, J., Bhattacharyya, B., Stappers, B. W., and Kerr, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The 1.69 ms spin period of PSR J1227-4853 was recently discovered in radio observations of the low-mass X-ray binary XSS J12270-4859 following the announcement of a possible transition to a rotation-powered millisecond pulsar state, inferred from decreases in optical, X-ray, and gamma-ray flux from the source. We report the detection of significant (5$\sigma$) gamma-ray pulsations after the transition, at the known spin period, using ~1 year of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The gamma-ray light curve of PSR J1227-4853 can be fit by one broad peak, which occurs at nearly the same phase as the main peak in the 1.4 GHz radio profile. The partial alignment of light-curve peaks in different wavebands suggests that at least some of the radio emission may originate at high altitude in the pulsar magnetosphere, in extended regions co-located with the gamma-ray emission site. We folded the LAT data at the orbital period, both pre- and post-transition, but find no evidence for significant modulation of the gamma-ray flux. Analysis of the gamma-ray flux over the mission suggests an approximate transition time of 2012 November 30. Continued study of the pulsed emission and monitoring of PSR J1227-4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems., Comment: 5 figures, 1 table, accepted for publication in ApJ, updated to reflect accepted version and add additional coauthor
Published: 2015
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133. The anatomy of $\gamma$-ray pulsar light curves

Author: Seyffert, A. S., Venter, C., Johnson, T. J., and Harding, A. K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We previously obtained constraints on the viewing geometries of 6 Fermi LAT pulsars using a multiwavelength approach (Seyffert et al., 2011). To obtain these constraints we compared the observed radio and $\gamma$-ray light curves (LCs) for those 6 pulsars by eye to LCs predicted by geometric models detailing the location and extent of emission regions in a pulsar magnetosphere. As a precursor to obtaining these constraints, a parameter study was conducted to reinforce our qualitative understanding of how the underlying model parameters effect the LCs produced by the geometric models. Extracting useful trends from the $\gamma$-ray model LCs proved difficult though due to the increased complexity of the geometric models for the $\gamma$-ray emission relative to those for the radio emission. In this paper we explore a second approach to investigating the interplay between the model parameters and the LC atlas. This approach does not attempt to understand how the set of model parameters influences the LC shapes directly, but rather, more fundamentally, investigates how the set of model parameters effects the sky maps from which the latter are extracted. This allows us to also recognise structure within the atlas itself, as we are now able to attribute certain features of the LCs to specific features on the sky map, meaning that we not only understand how the structure of single LCs come about, but also how their structure changes as we move through the geometric solution space., Comment: 6 pages, 4 figures. Part of the proceedings of the South African Institute of Physics (SAIP) conference for 2012. ISBN: 978-1-77592-070-0
Published: 2015

134. The Effect of Different Magnetospheric Structures on Predictions of Gamma-ray Pulsar Light Curves

Author: Breed, M., Venter, C., Harding, A. K., and Johnson, T. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The second pulsar catalogue of the Fermi Large Area Telescope (LAT) will contain in excess of 100 gamma-ray pulsars. The light curves (LCs) of these pulsars exhibit a variety of shapes, and also different relative phase lags with respect to their radio pulses, hinting at distinct underlying emission properties (e.g., inclination and observer angles) for the individual pulsars. Detailed geometric modelling of the radio and gamma-ray LCs may provide constraints on the B-field structure and emission geometry. We used different B-field solutions, including the static vacuum dipole and the retarded vacuum dipole, in conjunction with an existing geometric modelling code, and constructed radiation sky maps and LCs for several different pulsar parameters. Standard emission geometries were assumed, namely the two-pole caustic (TPC) and outer gap (OG) models. The sky maps and LCs of the various B-field and radiation model combinations were compared to study their effect on the resulting LCs. As an application, we compared our model LCs with Fermi LAT data for the Vela pulsar, and inferred the most probable configuration in this case, thereby constraining Vela's high-altitude magnetic structure and system geometry., Comment: 6 pages, 4 figures, conference article, appears in Proceedings of SAIP2012, the 57th Annual Conference of the South African Institute of Physics, edited by Johan Janse van Rensburg, ISBN: 978-1-77592-070-0
Published: 2015

135. Impact of Electron Precipitation on Brown Dwarf Atmospheres and the Missing Auroral H3+ Emission

Author: Pineda, J. Sebastian, primary, Hallinan, Gregg, additional, Desert, Jean-Michel, additional, and Harding, Leon K., additional
Published: 2024
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136. The Influence of Turnover among Other Top Executives on Financial Reporting Risk

Author: Bills, Kenneth L., primary, Harding, Michelle K., additional, Seidel, Timothy A., additional, and Truelson, J. Mike, additional
Published: 2024
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137. Establishing a national linked database for fetal alcohol spectrum disorder (FASD) in the UK: multi-method public and professional involvement to determine acceptability and feasibility

Author: Harding, Sarah K, primary, Samways, Beverley, additional, Dillon, Amy, additional, Butcher, Sandra, additional, Boyd, Andy, additional, Mukherjee, Raja, additional, Cook, Penny A., additional, and McQuire, Cheryl, additional
Published: 2024
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138. Broadband X-ray burst spectroscopy of the fast-radio-burst-emitting Galactic magnetar

Author: Younes, G., Baring, M. G., Kouveliotou, C., Arzoumanian, Z., Enoto, T., Doty, J., Gendreau, K. C., Göğüş, E., Guillot, S., Güver, T., Harding, A. K., Ho, W. C. G., van der Horst, A. J., Hu, C.-P., Jaisawal, G. K., Kaneko, Y., LaMarr, B. J., Lin, L., Majid, W., Okajima, T., Pope, J., Ray, P. S., Roberts, O. J., Saylor, M., Steiner, J. F., and Wadiasingh, Z.
Published: 2021
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139. The Emission Physics of Millisecond Pulsars

Author: Harding, Alice K., primary
Published: 2021
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140. Inflammation and Infection

Author: Hall, Judith, primary and Harding, Christopher K., additional
Published: 2021
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141. Discovery of PSR J1227-4853: A transition from a low-mass X-ray binary to a redback millisecond pulsar

Author: Roy, Jayanta, Ray, Paul S., Bhattacharyya, Bhaswati, Stappers, Ben, Chengalur, Jayaram N., Deneva, Julia, Camilo, Fernando, Johnson, Tyrel J., Wolff, Michael, Hessels, Jason W. T., Bassa, Cees G., Keane, Evan F., Ferrara, Elizabeth C., Harding, Alice K., and Wood, Kent S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: XSS J12270-4859 is an X-ray binary associated with the Fermi LAT gamma-ray source 1FGL J1227.9-4852. In 2012 December, this source underwent a transition where the X-ray and optical luminosity dropped and the spectral signatures of an accretion disc disappeared. We report the discovery of a 1.69 millisecond pulsar (MSP), PSR J1227-4853, at a dispersion measure of 43.4 pc cm$^{-3}$ associated with this source, using the GMRT at 607 MHz. This demonstrates that, post-transition, the system hosts an active radio MSP. This is the third system after PSR J1023+0038 and PSR J1824-2452I showing evidence of state switching between radio MSP and low-mass X-ray binary (LMXB) states. We report timing observations of PSR J1227-4853 with the GMRT and Parkes, which give a precise determination of the rotational and orbital parameters of the system. The companion mass measurement of 0.17 to 0.46 M$_{sun}$ suggests that this is a redback system. PSR J1227-4853 is eclipsed for about 40% of its orbit at 607 MHz; with additional short-duration eclipses at all orbital phases. We also find that the pulsar is very energetic, with a spin-down luminosity of ~ 10$^{35}$ erg s$^{-1}$. We report simultaneous imaging and timing observations with the GMRT, which suggests that eclipses are caused by absorption, rather than dispersion smearing or scattering., Comment: 16 pages, 3 figures, accepted for publication in ApJ Letters
Published: 2014
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142. Implementation of an offset-dipole magnetic field in a pulsar modelling code

Author: Breed, M., Venter, C., Harding, A. K., and Johnson, T. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The light curves of gamma-ray pulsars detected by the Fermi Large Area Telescope show great variety in profile shape and position relative to their radio profiles. Such diversity hints at distinct underlying magnetospheric and/or emission geometries for the individual pulsars. We implemented an offset-dipole magnetic field in an existing geometric pulsar modelling code which already includes static and retarded vacuum dipole fields. In our model, this offset is characterised by a parameter epsilon (with epsilon = 0 corresponding to the static dipole case). We constructed sky maps and light curves for several pulsar parameters and magnetic fields, studying the effect of an offset dipole on the resulting light curves. A standard two-pole caustic emission geometry was used. As an application, we compared our model light curves with Fermi data for the bright Vela pulsar., Comment: 6 pages, 4 figures, conference article. appears in Proceedings of SAIP2013, the 58th Annual Conference of the South African Institute of Physics, edited by Roelf Botha and Thulani Jili, ISBN: 978-0-620-62819-8
Published: 2014

143. Modelling the $\gamma$-ray and radio light curves of the double pulsar system

Author: Seyffert, A. S., Venter, C., Harding, A. K., and Johnson, T. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Guillemot et al. recently reported the discovery of $\gamma$-ray pulsations from the 22.7ms pulsar (pulsar A) in the famous double pulsar system J0737-3039A/B. The $\gamma$-ray light curve (LC) of pulsar A has two peaks separated by approximately half a rotation, and these are non-coincident with the observed radio and X-ray peaks. This suggests that the $\gamma$-ray emission originates in a part of the magnetosphere distinct from where the radio and X-ray radiation is generated. Thus far, three different methods have been applied to constrain the viewing geometry of pulsar A (its inclination and observer angles $\alpha$ and $\zeta$): geometric modelling of the radio and $\gamma$-ray light curves, modelling of the position angle sweep in phase seen in the radio polarisation data, and independent studies of the time evolution of the radio pulse profile of pulsar A. These three independent, complementary methods have yielded consistent results: pulsar A's rotation axis is likely perpendicular to the orbital plane of the binary system, and its magnetic axis close to lying in the orbital plane (making this pulsar an orthogonal rotator). The observer is furthermore observing emission close to the magnetic axis. Thus far, however, current models could not reproduce all the characteristics of the radio and $\gamma$-ray light curves, specifically the large radio-to-$\gamma$ phase lag. In this paper we discuss some preliminary modelling attempts to address this problem, and offer ideas on how the LC fits may be improved by adapting the standard geometric models in order to reproduce the profile positions more accurately., Comment: 5 pages, 2 figures, 1 table. Part of the proceedings of the South African Institute of Physics (SAIP) conference for 2013
Published: 2014

144. The Contribution of Millisecond Pulsars to the Galactic Cosmic-Ray Lepton Spectrum

Author: Venter, C., Kopp, A., Gonthier, P. L., Harding, A. K., and Büsching, I.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Pulsars are believed to be sources of relativistic electrons and positrons. The abundance of detections of gamma-ray millisecond pulsars by Fermi Large Area Telescope coupled with their light curve characteristics that imply copious pair production in their magnetospheres, motivated us to investigate this old pulsar population as a source of Galactic electrons and positrons and their contribution to the enhancement in cosmic-ray positron flux at GeV energies. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic millisecond pulsars, taking into account the latest Fermi and radio observations to calibrate the model output. Next, we simulate pair cascade spectra from these pulsars using a model that invokes an offset-dipole magnetic field. We assume free escape of the pairs from the pulsar environment. We then compute the cumulative spectrum of transported electrons and positrons at Earth, following their diffusion and energy losses as they propagate through the Galaxy. Our results indicate that the predicted particle flux increases for non-zero offsets of the magnetic polar caps. Comparing our predicted spectrum and positron fraction to measurements by AMS-02, PAMELA, and Fermi, we find that millisecond pulsars are only modest contributors at a few tens of GeV, after which this leptonic spectral component cuts off. The positron fraction is therefore only slightly enhanced above 10 GeV relative to a background flux model. This implies that alternative sources such as young, nearby pulsars and supernova remnants should contribute additional primary positrons within the astrophysical scenario., Comment: 19 pages, 3 figures, accepted for publication in Advances in Space Research
Published: 2014
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145. Constraints on the Emission Geometries and Spin Evolution of Gamma-ray Millisecond Pulsars

Author: Johnson, T. J., Venter, C., Harding, A. K., Guillemot, L., Smith, D. A., Kramer, M., Celik, O., Hartog, P. R. den, Ferrara, E. C., Hou, X., Lande, J., and Ray, P. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II) or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed., Comment: Accepted for publication in ApJS, auxiliary files can be found at the entry for this paper at http://www-glast.stanford.edu/cgi-bin/pubpub
Published: 2014
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146. Inferred cosmic-ray spectrum from ${\it Fermi}$-LAT $\gamma$-ray observations of the Earth's limb

Author: Collaboration, Fermi-LAT, Ackermann, M., Ajello, M., Albert, A., Allafort, A., Baldini, L., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Blandford, R. D., Bloom, E. D., Bonamente, E., Bottacini, E., Bouvier, A., Brandt, T. J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caraveo, P. A., Cecchi, C., Charles, E., Chaves, R. C. G., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen-Tanugi, J., Conrad, J., Cutini, S., Dalton, M., D'Ammando, F., de Angelis, A., de Palma, F., Dermer, C. D., Digel, S. W., Di Venere, L., Silva, E. do Couto e, Drell, P. S., Drlica-Wagner, A., Favuzzi, C., Fegan, S. J., Ferrara, E. C., Focke, W. B., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Germani, S., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Gomez-Vargas, G. A., Grenier, I. A., Grove, J. E., Guiriec, S., Gustafsson, M., Hadasch, D., Hanabata, Y., Harding, A. K., Hayashida, M., Hayashi, K., Hewitt, J. W., Horan, D., Hou, X., Hughes, R. E., Inoue, Y., Jackson, M. S., Jogler, T., Jóhannesson, G., Johnson, A. S., Kamae, T., Kawano, T., Knödlseder, J., Kuss, M., Lande, J., Larsson, S., Latronico, L., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Mayer, M., Mazziotta, M. N., McEnery, J. E., Mehault, J., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monte, C., Monzani, M. E., Morselli, A., Moskalenko, I. V., Murgia, S., Nemmen, R., Nuss, E., Ohsugi, T., Okumura, A., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Panetta, J. H., Perkins, J. S., Pesce-Rollins, M., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Ritz, S., Roth, M., Schaal, M., Schulz, A., Sgrò, C., Siskind, E. J., Spandre, G., Spinelli, P., Strong, A. W., Takahashi, H., Takeuchi, Y., Thayer, J. G., Thayer, J. B., Thompson, D. J., Tibaldo, L., Tinivella, M., Torres, D. F., Tosti, G., Troja, E., Tronconi, V., Usher, T. L., Vandenbroucke, J., Vasileiou, V., Vianello, G., Vitale, V., Werner, M., Winer, B. L., Wood, K. S., Wood, M., and Yang, Z.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly-discovered features may offer a clue to the origin of high-energy CRs. We use the ${\it Fermi}$ Large Area Telescope observations of the $\gamma$-ray emission from the Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range $\sim 90~$GeV-$6~$TeV (derived from a photon energy range $15~$GeV-$1~$TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index $2.68 \pm 0.04$ and $2.61 \pm 0.08$ above $\sim 200~$GeV, respectively., Comment: Accepted by PRL for publication; Contact authors: Stefan Funk, Warit Mitthumsiri, Igor Moskalenko; 2 figures
Published: 2014

147. Detection of a faint fast-moving near-Earth asteroid using synthetic tracking technique

Author: Zhai, Chengxing, Shao, Michael, Nemati, Bijan, Werne, Thomas A., Zhou, Hanying, Turyshev, Slava G., Sandhu, Jagmit, Hallinan, Gregg W., and Harding, Leon K.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: We report a detection of a faint near-Earth asteroid (NEA), which was done using our synthetic tracking technique and the CHIMERA instrument on the Palomar 200-inch telescope. This asteroid, with apparent magnitude of 23, was moving at 5.97 degrees per day and was detected at a signal-to-noise ratio (SNR) of 15 using 30 sec of data taken at a 16.7 Hz frame rate. The detection was confirmed by a second observation one hour later at the same SNR. The asteroid moved 7 arcseconds in sky over the 30 sec of integration time because of its high proper motion. The synthetic tracking using 16.7 Hz frames avoided the trailing loss suffered by conventional techniques relying on 30-sec exposure, which would degrade the surface brightness of image on CCD to an approximate magnitude of 25. This detection was a result of our 12-hour blind search conducted on the Palomar 200-inch telescope over two nights on September 11 and 12, 2013 scanning twice over six 5.0 deg x 0.043 deg fields. The fact that we detected only one NEA, is consistent with Harris's estimation of the asteroid population distribution, which was used to predict the detection of 1--2 asteroids of absolute magnitude H=28--31 per night. The design of experiment, data analysis method, and algorithms for estimating astrometry are presented. We also demonstrate a milli-arcsecond astrometry using observations of two bright asteroids with the same system on Apr 3, 2013. Strategies of scheduling observations to detect small and fast-moving NEAs with the synthetic tracking technique are discussed.
Published: 2014
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148. Light-curve modelling constraints on the obliquities and aspect angles of the young Fermi pulsars

Author: Pierbattista, M., Harding, A. K., Grenier, I. A., Johnson, T. J., Caraveo, P. A., Kerr, M., and Gonthier, P. L.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: In more than four years of observation the Large Area Telescope on board the Fermi satellite has identified pulsed $\gamma$-ray emission from more than 80 young pulsars, providing light curves with high statistics. Fitting the observations with geometrical models can provide estimates of the magnetic obliquity $\alpha$ and aspect angle $\zeta$, yielding estimates of the radiation beaming factor and luminosity. Using $\gamma$-ray emission geometries (Polar Cap, Slot Gap, Outer Gap, One Pole Caustic) and radio emission geometry, we fit $\gamma$-ray light curves for 76 young pulsars and we jointly fit their $\gamma$-ray plus radio light curves when possible. We find that a joint radio plus $\gamma$-ray fit strategy is important to obtain ($\alpha$, $\zeta$) estimates that can explain simultaneous radio and $\gamma$-ray emission. The intermediate-to-high altitude magnetosphere models, Slot Gap, Outer Gap, and One pole Caustic, are favoured in explaining the observations. We find no evolution of $\alpha$ on a time scale of a million years. For all emission geometries our derived $\gamma$-ray beaming factors are generally less than one and do not significantly evolve with the spin-down power. A more pronounced beaming factor vs. spin-down power correlation is observed for Slot Gap model and radio-quiet pulsars and for the Outer Gap model and radio-loud pulsars. For all models, the correlation between $\gamma$-ray luminosity and spin-down power is consistent with a square root dependence. The $\gamma$-ray luminosities obtained by using our beaming factors not exceed the spin-down power. This suggests that assuming a beaming factor of one for all objects, as done in other studies, likely overestimates the real values. The data show a relation between the pulsar spectral characteristics and the width of the accelerator gap that is consistent with the theoretical prediction for the Slot Gap model., Comment: 90 pages, 80 figures (63 in Appendices), accepted for publication in Astronomy and Astrophysics
Published: 2014
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149. PTF1 J191905.19+481506.2 - A Partially Eclipsing AM CVn System Discovered in the Palomar Transient Factory

Author: Levitan, David, Kupfer, Thomas, Groot, Paul J., Margon, Bruce, Prince, Thomas A., Kulkarni, Shrinivas R., Hallinan, Gregg, Harding, Leon K., Kyne, Gillian, Laher, Russ, Ofek, Eran O., Rutten, René G. M., Sesar, Branimir, and Surace, Jason
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: We report on PTF1 J191905.19+481506.2, a newly discovered, partially eclipsing, outbursting AM CVn system found in the Palomar Transient Factory synoptic survey. This is only the second known eclipsing AM CVn system. We use high-speed photometric observations and phase-resolved spectroscopy to establish an orbital period of 22.4559(3) min. We also present a long-term light curve and report on the normal and super-outbursts regularly seen in this system, including a super-outburst recurrence time of 36.8(4) d. We use the presence of the eclipse to place upper and lower limits on the inclination of the system and discuss the number of known eclipsing AM CVn systems versus what would be expected., Comment: 13 pages, 10 figures, accepted to ApJ
Published: 2014
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150. High-Time-Resolution Measurements of the Polarization of the Crab Pulsar at 1.38 GHz

Author: Slowikowska, Agnieszka, Stappers, Benjamin W., Harding, Alice K., O'Dell, Stephen L., Elsner, Ronald F., van der Horst, Alexander J., and Weisskopf, Martin C.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Using the Westerbork Synthesis Radio Telescope (WSRT), we obtained high-time-resolution measurements of the full (linear and circular) polarization of the Crab pulsar. Taken at a resolution of 1/8192 of the 34-ms pulse period (i.e., $4.1~\mu{\rm s}$), the 1.38-GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4-GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about $24\%$ and $21\%$, with no discernible difference in polarization position angle. However, and contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in polarization position angle over the MP, the IP, or the LFC. Although, the main pulse exhibits a small but statistically significant quadratic variation in the degree of linear polarization. We discuss the implications which appear to be in contradiction to theoretical expectations. In addition, we detect weak circular polarization in the main pulse and interpulse, and strong ($\approx 20\%$) circular polarization in the low-frequency component, which also exhibits very strong ($\approx 98\%$) linear polarization at a position angle about $40\degree$ from that of the MP or IP. The pulse-mean polarization properties are consistent with the LFC being a low-altitude component and the MP and IP being high-altitude caustic components. Nevertheless, current models for the MP and IP emission do not readily account for the observed absence of pronounced polarization changes across the pulse. Finally, we measure IP and LFC pulse phases relative to the MP that are consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time., Comment: 28 pages, 10 figures, accepted by the Astrophysical Journal
Published: 2014
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