R
Roopesh Ojha
Researcher at Goddard Space Flight Center
Publications - 177
Citations - 5735
Roopesh Ojha is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Blazar & Active galactic nucleus. The author has an hindex of 36, co-authored 175 publications receiving 5113 citations. Previous affiliations of Roopesh Ojha include Brandeis University & Commonwealth Scientific and Industrial Research Organisation.
Papers
More filters
Journal ArticleDOI
The spectral energy distribution of fermi bright blazars
A. A. Abdo,A. A. Abdo,Markus Ackermann,Ivan Agudo,Marco Ajello,Hugh D. Aller,Margo F. Aller,Emmanouil Angelakis,A. A. Arkharov,Magnus Axelsson,Magnus Axelsson,Uwe Bach,Luca Baldini,Jean Ballet,Guido Barbiellini,Denis Bastieri,B. M. Baughman,Keith Bechtol,Ronaldo Bellazzini,Erika Benítez,Andrei Berdyugin,B. Berenji,Roger Blandford,E. D. Bloom,Markus Boettcher,Emanuele Bonamente,A. W. Borgland,Johan Bregeon,A. Brez,M. Brigida,P. Bruel,T. H. Burnett,David N. Burrows,S. Buson,G. A. Caliandro,L. Calzoletti,R. A. Cameron,M. Capalbi,P. A. Caraveo,D. Carosati,J. M. Casandjian,E. Cavazzuti,C. Cecchi,Omer Celik,Omer Celik,E. Charles,Sylvain Chaty,A. Chekhtman,A. Chekhtman,Wen Ping Chen,James Chiang,G. Chincarini,Stefano Ciprini,R. Claus,Johann Cohen-Tanugi,S. Colafrancesco,L. R. Cominsky,Jan Conrad,Jan Conrad,L. Costamante,S. Cutini,F. D'Ammando,R. Deitrick,V. D'Elia,Charles D. Dermer,A. De Angelis,F. de Palma,Seth Digel,I. Donnarumma,E. Do Couto E Silva,Persis S. Drell,R. Dubois,Deborah Dultzin,D. Dumora,A. D. Falcone,C. Farnier,C. Favuzzi,S. J. Fegan,W. B. Focke,E. Forné,P. Fortin,Marco Frailis,Lars Fuhrmann,Yasushi Fukazawa,Stefan Funk,P. Fusco,José L. Gómez,F. Gargano,Dario Gasparrini,Neil Gehrels,S. Germani,B. Giebels,Nicola Giglietto,Paolo Giommi,F. Giordano,A. Giuliani,T. Glanzman,G. Godfrey,I. A. Grenier,Caryl Gronwall,J. E. Grove,L. Guillemot,L. Guillemot,Sylvain Guiriec,Mark Gurwell,D. Hadasch,Y. Hanabata,Alice K. Harding,M. Hayashida,E. Hays,S. E. Healey,Jochen Heidt,David Hiriart,D. Horan,E. A. Hoversten,R. E. Hughes,Ryosuke Itoh,Miranda Jackson,Miranda Jackson,Gudlaugur Johannesson,A. S. Johnson,W. N. Johnson,Svetlana G. Jorstad,Matthias Kadler,T. Kamae,Hideaki Katagiri,Jun Kataoka,Nobuyuki Kawai,J. A. Kennea,Matthew Kerr,Givi N. Kimeridze,Jürgen Knödlseder,M. L. Kocian,E. N. Kopatskaya,Ekaterina Koptelova,Tatiana S. Konstantinova,Yuri Y. Kovalev,Yu. A. Kovalev,Omar M. Kurtanidze,M. Kuss,J. Lande,Valeri M. Larionov,Luca Latronico,Paolo Leto,Elina Lindfors,Francesco Longo,F. Loparco,Benoit Lott,M. N. Lovellette,P. Lubrano,Grzegorz Madejski,A. Makeev,A. Makeev,P. Marchegiani,Alan P. Marscher,F. E. Marshall,Walter Max-Moerbeck,M. N. Mazziotta,W. McConville,W. McConville,Julie McEnery,Julie McEnery,C. Meurer,Peter F. Michelson,W. Mitthumsiri,Tsunefumi Mizuno,A. A. Moiseev,A. A. Moiseev,C. Monte,M. E. Monzani,A. Morselli,Igor V. Moskalenko,S. Murgia,I. Nestoras,K. Nilsson,N. A. Nizhelsky,P. L. Nolan,J. P. Norris,E. Nuss,T. Ohsugi,Roopesh Ojha,Nicola Omodei,E. Orlando,Jonathan F. Ormes,J. P. Osborne,M. Ozaki,L. Pacciani,Paolo Padovani,C. Pagani,K. L. Page,David Paneque,J. H. Panetta,D. Parent,M. Pasanen,Vasiliki Pavlidou,V. Pelassa,M. Pepe,M. Perri,Melissa Pesce-Rollins,S. Piranomonte,F. Piron,C. Pittori,T. A. Porter,Simonetta Puccetti,Farid Rahoui,S. Rainò,C. M. Raiteri,Robert R. Rando,M. Razzano,A. Reimer,A. Reimer,Olaf Reimer,Olaf Reimer,T. Reposeur,Joseph L. Richards,Steven Ritz,L.S. Rochester,A. Y. Rodriguez,Roger W. Romani,J. A. Ros,M. Roth,P. Roustazadeh,Felix Ryde,Felix Ryde,H. F.W. Sadrozinski,A. C. Sadun,David Sánchez,A. Sander,P. M. Saz Parkinson,Jeffrey D. Scargle,A. Sellerholm,Carmelo Sgrò,M. S. Shaw,Lorand A. Sigua,E. J. Siskind,David A. Smith,P. D. Smith,Gloria Spandre,P. Spinelli,Jean-Luc Starck,Mark Stevenson,G. Stratta,M. S. Strickman,D. J. Suson,H. Tajima,Hiromitsu Takahashi,Tadayuki Takahashi,L. O. Takalo,Takaaki Tanaka,J. B. Thayer,J. G. Thayer,D. J. Thompson,L. Tibaldo,Diego F. Torres,Gino Tosti,A. Tramacere,A. Tramacere,Yasunobu Uchiyama,T. L. Usher,V. Vasileiou,V. Vasileiou,F. Verrecchia,N. Vilchez,M. Villata,V. Vitale,A. P. Waite,Paul J. Wang,Brian L Winer,K. S. Wood,T. Ylinen,T. Ylinen,J. A. Zensus,G. V. Zhekanis,M. Ziegler +273 more
Abstract: We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log nu-log nu F-nu representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low-and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(ro), and optical to X-ray, alpha(ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (nu(S)(peak)) is positioned between 10(12.5) and 10(14.5) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(13) and 10(17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter gamma-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum gamma-ray sources, the correlation between nu(S)(peak) and gamma-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars.
Journal ArticleDOI
The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
Markus Ackermann,Marco Ajello,W. B. Atwood,Luca Baldini,Jean Ballet,Guido Barbiellini,Guido Barbiellini,Denis Bastieri,Denis Bastieri,J. Becerra González,J. Becerra González,Ronaldo Bellazzini,Elisabetta Bissaldi,Roger Blandford,E. D. Bloom,R. Bonino,R. Bonino,Eugenio Bottacini,T. J. Brandt,Johan Bregeon,R. J. Britto,P. Bruel,R. Buehler,S. Buson,S. Buson,G. A. Caliandro,R. A. Cameron,M. Caragiulo,P. A. Caraveo,Bryce Carpenter,Bryce Carpenter,J. M. Casandjian,E. Cavazzuti,Claudia Cecchi,Claudia Cecchi,Eric Charles,A. Chekhtman,C. C. Cheung,James Chiang,G. Chiaro,Stefano Ciprini,Stefano Ciprini,Stefano Ciprini,R. Claus,Johann Cohen-Tanugi,L. R. Cominsky,Jan Conrad,S. Cutini,S. Cutini,S. Cutini,Raffaele D'Abrusco,Filippo D'Ammando,Filippo D'Ammando,A. De Angelis,R. Desiante,R. Desiante,Seth Digel,L. Di Venere,Persis S. Drell,C. Favuzzi,C. Favuzzi,S. J. Fegan,Elizabeth C. Ferrara,Justin D. Finke,W. B. Focke,A. Franckowiak,Lars Fuhrmann,Yasushi Fukazawa,A. K. Furniss,P. Fusco,P. Fusco,F. Gargano,Dario Gasparrini,Dario Gasparrini,Dario Gasparrini,Nicola Giglietto,Nicola Giglietto,Paolo Giommi,Francesco Giordano,Francesco Giordano,Marcello Giroletti,T. Glanzman,G. Godfrey,I. A. Grenier,J. E. Grove,Sylvain Guiriec,John W. Hewitt,John W. Hewitt,A. B. Hill,A. B. Hill,D. Horan,Ryosuke Itoh,Gudlaugur Johannesson,A. S. Johnson,W. N. Johnson,Jun Kataoka,T. Kawano,Felicia Krauss,M. Kuss,G. La Mura,Stefan Larsson,Luca Latronico,C. Leto,J. Li,Liang Li,Liang Li,Francesco Longo,Francesco Longo,F. Loparco,F. Loparco,B. Lott,M. N. Lovellette,P. Lubrano,P. Lubrano,G. M. Madejski,M. Mayer,M. N. Mazziotta,Julie McEnery,Julie McEnery,Peter F. Michelson,Tsunefumi Mizuno,A. A. Moiseev,A. A. Moiseev,M. E. Monzani,A. Morselli,Igor V. Moskalenko,S. Murgia,E. Nuss,Masanori Ohno,T. Ohsugi,Roopesh Ojha,Nicola Omodei,M. Orienti,E. Orlando,Alessandro Paggi,David Paneque,David Paneque,J. S. Perkins,Melissa Pesce-Rollins,F. Piron,G. Pivato,T. A. Porter,S. Rainò,S. Rainò,Riccardo Rando,Riccardo Rando,M. Razzano,Soebur Razzaque,A. Reimer,Olaf Reimer,Roger W. Romani,David Salvetti,M. Schaal,Frank K. Schinzel,André Schulz,Carmelo Sgrò,E. J. Siskind,Kirill Sokolovsky,Kirill Sokolovsky,F. Spada,Gloria Spandre,P. Spinelli,P. Spinelli,Lukasz Stawarz,Lukasz Stawarz,D. J. Suson,Hiromitsu Takahashi,Tadayuki Takahashi,Yasuyuki T. Tanaka,J. G. Thayer,J. B. Thayer,L. Tibaldo,Diego F. Torres,Diego F. Torres,Eleonora Torresi,Gino Tosti,Gino Tosti,Eleonora Troja,Eleonora Troja,Yasunobu Uchiyama,Giacomo Vianello,Brian L Winer,K. S. Wood,Stephan Zimmer +183 more
TL;DR: The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented in this paper, which is based on the 3FGL of sources detected between 100 MeV and 300 GeV.
Journal ArticleDOI
The second realization of the international celestial reference frame by very long baseline interferometry
A. L. Fey,David Gordon,Christopher S. Jacobs,C. Ma,Ralph A. Gaume,E. F. Arias,Giuseppe Bianco,David A. Boboltz,S. Böckmann,S. Bolotin,Patrick Charlot,A. Collioud,G. Engelhardt,John Gipson,A. M. Gontier,Robert Heinkelmann,S. Kurdubov,Sébastien Lambert,S. O. Lytvyn,Daniel MacMillan,Zinovy Malkin,Axel Nothnagel,Roopesh Ojha,E. Skurikhina,J. R. Sokolova,J. Souchay,Ojars J. Sovers,Volker Tesmer,Oleg Titov,Gang Wang,Vladimir Zharov +30 more
TL;DR: The second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths is presented, adopted by the International Astronomical Union as the new fundamental celestial reference frame, replacing ICRF1 as of 2010 January 1.
Journal ArticleDOI
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event
Matthias Kadler,Felicia Krauß,Felicia Krauß,Karl Mannheim,Roopesh Ojha,Roopesh Ojha,Roopesh Ojha,C. Müller,C. Müller,R. Schulz,R. Schulz,Gisela Anton,W. Baumgartner,T. Beuchert,T. Beuchert,S. Buson,S. Buson,Bryce Carpenter,Thomas Eberl,Philip G. Edwards,D. Eisenacher Glawion,Dominik Elsässer,N. Gehrels,C. Gräfe,C. Gräfe,Sergei Gulyaev,H. Hase,Shinji Horiuchi,C. W. James,Alexander Kappes,Uli Katz,A. Kreikenbohm,A. Kreikenbohm,M. Kreter,M. Kreter,I. Kreykenbohm,M. Langejahn,M. Langejahn,K. Leiter,K. Leiter,E. Litzinger,E. Litzinger,Francesco Longo,Francesco Longo,James E. J. Lovell,Julie McEnery,Tim Natusch,Chris Phillips,Christian Plötz,J. F. H. Quick,Eduardo Ros,Eduardo Ros,F. W. Stecker,F. W. Stecker,T. Steinbring,T. Steinbring,Jamie Stevens,D. J. Thompson,J. Trüstedt,J. Trüstedt,Anastasios Tzioumis,Stuart Weston,Jörn Wilms,J. A. Zensus +63 more
TL;DR: In this paper, the IceCube neutrino telescope in the South Pole has observed several high-energy neutrinos of undetermined origin from blazar PKS B1424-418.
Journal ArticleDOI
The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
Marco Ajello,R. Angioni,R. Angioni,Magnus Axelsson,Magnus Axelsson,Jean Ballet,Guido Barbiellini,Guido Barbiellini,Denis Bastieri,Denis Bastieri,J. Becerra González,Ronaldo Bellazzini,Elisabetta Bissaldi,Elisabetta Bissaldi,Elliott D. Bloom,R. Bonino,R. Bonino,Eugenio Bottacini,Eugenio Bottacini,P. Bruel,S. Buson,Fabio Cafardo,R. A. Cameron,E. Cavazzuti,Sina Chen,Sina Chen,C. C. Cheung,Stefano Ciprini,Stefano Ciprini,D. Costantin,S. Cutini,Filippo D'Ammando,P. de la Torre Luque,R. de Menezes,R. de Menezes,F. de Palma,Abhishek Desai,N. Di Lalla,L. Di Venere,L. Di Venere,Aaron Dominguez,F. Fana Dirirsa,Elizabeth C. Ferrara,Justin D. Finke,Anna Franckowiak,Yasushi Fukazawa,Stefan Funk,P. Fusco,P. Fusco,F. Gargano,S. Garrappa,Dario Gasparrini,Dario Gasparrini,Nicola Giglietto,Nicola Giglietto,Francesco Giordano,Francesco Giordano,Marcello Giroletti,David A. Green,I. A. Grenier,Sylvain Guiriec,Sylvain Guiriec,S. Harita,E. Hays,D. Horan,R. Itoh,G. Jóhannesson,G. Jóhannesson,Miloš Kovačević,Felicia Krauss,Michael Kreter,Michael Kreter,M. Kuss,Stefan Larsson,Stefan Larsson,Stefan Larsson,C. Leto,J. Li,Ioannis Liodakis,Francesco Longo,Francesco Longo,F. Loparco,F. Loparco,B. Lott,M. N. Lovellette,P. Lubrano,G. M. Madejski,S. Maldera,Alberto Manfreda,G. Martí-Devesa,Francesco Massaro,Francesco Massaro,Mn Mazziotta,I. Mereu,I. Mereu,Manuel Meyer,Giulia Migliori,Nestor Mirabal,Nestor Mirabal,Tsunefumi Mizuno,M. E. Monzani,A. Morselli,Igor V. Moskalenko,M. Negro,M. Negro,Rodrigo Nemmen,E. Nuss,L. S. Ojha,Roopesh Ojha,Nicola Omodei,M. Orienti,E. Orlando,E. Orlando,J. F. Ormes,Vaidehi S. Paliya,Z. Pei,H. A. Peña-Herazo,Massimo Persic,Melissa Pesce-Rollins,Leonid Petrov,F. Piron,H. Poon,Giacomo Principe,S. Rainò,S. Rainò,Riccardo Rando,Riccardo Rando,Bindu Rani,Bindu Rani,M. Razzano,Soebur Razzaque,A. Reimer,Olaf Reimer,Frank K. Schinzel,Frank K. Schinzel,D. Serini,Carmelo Sgrò,E. J. Siskind,Gloria Spandre,P. Spinelli,P. Spinelli,D. J. Suson,Yutaro Tachibana,D. J. Thompson,Diego F. Torres,Eleonora Torresi,E. Troja,E. Troja,J. Valverde,P. van Zyl,P. van Zyl,M. Yassine,M. Yassine +152 more
TL;DR: The 4LAC catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains 2863 objects located at high Galactic latitudes (|b|>10°deg}).