Browsing by Author "Harvard-Smithsonian Center for Astrophysics"

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    2FHL: The SECOND CATALOG of HARD FERMI-LAT SOURCES
    (2016-01-01) M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; J. Becerra Gonzalez; R. Bellazzini; E. Bissaldi; R. D. Blandford; E. D. Bloom; R. Bonino; E. Bottacini; T. J. Brandt; J. Bregeon; P. Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; R. Caputo; M. Caragiulo; P. A. Caraveo; E. Cavazzuti; C. Cecchi; E. Charles; A. Chekhtman; C. C. Cheung; J. Chiang; G. Chiaro; S. Ciprini; J. M. Cohen; J. Cohen-Tanugi; L. R. Cominsky; J. Conrad; A. Cuoco; S. Cutini; F. D'Ammando; A. De Angelis; F. De Palma; R. Desiante; M. Di Mauro; L. Di Venere; A. Domínguez; P. S. Drell; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; P. Fortin; A. Franckowiak; Y. Fukazawa; S. Funk; A. K. Furniss; P. Fusco; F. Gargano; D. Gasparrini; N. Giglietto; P. Giommi; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; I. A. Grenier; M. H. Grondin; L. Guillemot; S. Guiriec; A. K. Harding; E. Hays; J. W. Hewitt; A. B. Hill; D. Horan; Deutsche Elektronen-Synchrotron; Clemson University; Santa Cruz Institute for Particle Physics; Istituto Nazionale Di Fisica Nucleare, Sezione di Pisa; Kavli Institute for Particle Astrophysics and Cosmology; Institut de Recherche sur les Lois Fondamentales de l'Univers; Istituto Nazionale di Fisica Nucleare, Roma; Universita degli Studi di Trieste; Istituto Nazionale Di Fisica Nucleare, Sezione di Padova; Università degli Studi di Padova; NASA Goddard Space Flight Center; University of Maryland; Università degli Studi di Torino; Laboratoire Univers et Particules de Montpellier; Laboratoire Leprince-Ringuet; University of Maryland, Baltimore County; Consorzio Interuniversitario per la Fisica Spaziale (CIFS); Università degli Studi di Bari; INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan; Agenzia Spaziale Italiana; Universita degli Studi di Perugia; George Mason University, Fairfax Campus; Naval Research Laboratory; Sonoma State University; Stockholms universitet; Oskar Klein Centre for Cosmoparticle Physics; Osservatorio Astronomico di Roma; Istituto Di Radioastronomia, Bologna; Alma Mater Studiorum Università di Bologna; Università degli Studi di Napoli Federico II; Universita degli Studi di Udine; Harvard-Smithsonian Center for Astrophysics; Hiroshima University; Erlangen Centre for Astroparticle Physics; IN2P3 Institut National de Physique Nucleaire et de Physique des Particules; Universite d'Orleans; Institut National des Sciences de l'Univers; University of North Florida; University of Southampton; Osservatorio Astronomico di Trieste; University Science Institute Reykjavik; University of Tokyo; Waseda University; CNRS Centre National de la Recherche Scientifique; Universite de Toulouse; Medizinische Universitat Innsbruck; The Royal Institute of Technology (KTH); Universitat Autònoma de Barcelona
    © 2016. The American Astronomical Society. All rights reserved. We present a catalog of sources detected above 50 GeV by the Fermi-Large Area Telescope (LAT) in 80 months of data. The newly delivered Pass 8 event-level analysis allows the detection and characterization of sources in the 50 GeV-2 TeV energy range. In this energy band, Fermi-LAT has detected 360 sources, which constitute the second catalog of hard Fermi-LAT sources (2FHL). The improved angular resolution enables the precise localization of point sources (∼1.′7 radius at 68% C. L.) and the detection and characterization of spatially extended sources. We find that 86% of the sources can be associated with counterparts at other wavelengths, of which the majority (75%) are active galactic nuclei and the rest (11%) are Galactic sources. Only 25% of the 2FHL sources have been previously detected by Cherenkov telescopes, implying that the 2FHL provides a reservoir of candidates to be followed up at very high energies. This work closes the energy gap between the observations performed at GeV energies by Fermi-LAT on orbit and the observations performed at higher energies by Cherenkov telescopes from the ground.
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    3FHL: The Third Catalog of Hard Fermi-LAT Sources
    (2017-10-01) M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; R. Bellazzini; E. Bissaldi; R. D. Blandford; E. D. Bloom; R. Bonino; J. Bregeon; R. J. Britto; P. Bruel; R. Buehler; S. Buson; R. A. Cameron; R. Caputo; M. Caragiulo; P. A. Caraveo; E. Cavazzuti; C. Cecchi; E. Charles; A. Chekhtman; C. C. Cheung; G. Chiaro; S. Ciprini; J. M. Cohen; D. Costantin; F. Costanza; A. Cuoco; S. Cutini; F. D'Ammando; F. De Palma; R. Desiante; S. W. Digel; N. Di Lalla; M. Di Mauro; L. Di Venere; A. Domnguez; P. S. Drell; D. Dumora; C. Favuzzi; S. J. Fegan; E. C. Ferrara; P. Fortin; A. Franckowiak; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Giglietto; P. Giommi; F. Giordano; M. Giroletti; T. Glanzman; D. Green; I. A. Grenier; M. H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; A. K. Harding; E. Hays; J. W. Hewitt; D. Horan; G. Jóhannesson; S. Kensei; M. Kuss; G. La Mura; S. Larsson; L. Latronico; M. Lemoine-Goumard; J. Li; F. Longo; Clemson University; Santa Cruz Institute for Particle Physics; Università di Pisa; Universite Paris 7- Denis Diderot; Istituto Nazionale di Fisica Nucleare, Roma; Università degli Studi di Trieste; Istituto Nazionale Di Fisica Nucleare, Sezione di Padova; Università degli Studi di Padova; Istituto Nazionale Di Fisica Nucleare, Sezione di Pisa; Università degli Studi di Bari; Kavli Institute for Particle Astrophysics and Cosmology; Università degli Studi di Torino; Laboratoire Univers et Particules de Montpellier; University of the Free State; Laboratoire Leprince-Ringuet; Deutsche Elektronen-Synchrotron; NASA Goddard Space Flight Center; INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan; Agenzia Spaziale Italiana; Università degli Studi di Perugia; George Mason University, Fairfax Campus; Naval Research Laboratory; University of Maryland; Rheinisch-Westfälische Technische Hochschule Aachen; Istituto Di Radioastronomia, Bologna; Alma Mater Studiorum Università di Bologna; Università degli Studi di Napoli Federico II; Università degli Studi di Udine; Universidad Complutense de Madrid; IN2P3 Institut National de Physique Nucleaire et de Physique des Particules; Harvard-Smithsonian Center for Astrophysics; Hiroshima University; Erlangen Centre for Astroparticle Physics; Universite d'Orleans; Institut National des Sciences de l'Univers; University of North Florida; University Science Institute Reykjavik; Nordisk Institut for Teoretisk Atomtysik; The Royal Institute of Technology (KTH); Oskar Klein Centre for Cosmoparticle Physics; Universitat Autònoma de Barcelona; Stockholms universitet; Mahidol University
    © 2017. The American Astronomical Society. All rights reserved.. We present a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in the first 7 years of data using the Pass 8 event-level analysis. This is the Third Catalog of Hard Fermi-LAT Sources (3FHL), containing 1556 objects characterized in the 10 GeV-2 TeV energy range. The sensitivity and angular resolution are improved by factors of 3 and 2 relative to the previous LAT catalog at the same energies (1FHL). The vast majority of detected sources (79%) are associated with extragalactic counterparts at other wavelengths, including 16 sources located at very high redshift (z > 2). Of the sources, 8% have Galactic counterparts and 13% are unassociated (or associated with a source of unknown nature). The high-latitude sky and the Galactic plane are observed with a flux sensitivity of 4.4 to 9.5 ×10-11 ph cm-2 s-1, respectively (this is approximately 0.5% and 1% of the Crab Nebula flux above 10 GeV). The catalog includes 214 new γ-ray sources. The substantial increase in the number of photons (more than 4 times relative to 1FHL and 10 times to 2FHL) also allows us to measure significant spectral curvature for 32 sources and find flux variability for 163 of them. Furthermore, we estimate that for the same flux limit of 10-12 erg cm-2 s-1, the energy range above 10 GeV has twice as many sources as the range above 50 GeV, highlighting the importance, for future Cherenkov telescopes, of lowering the energy threshold as much as possible.
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    An extreme-mass ratio, short-period eclipsing binary consisting of a B dwarf primary and a pre-main-sequence M star companion discovered by KELT
    (2020-12-01) Daniel J. Stevens; George Zhou; Marshall C. Johnson; Aaron C. Rizzuto; Joseph E. Rodriguez; Allyson Bieryla; Karen A. Collins; Steven Villanueva; Jason T. Wright; B. Scott Gaudi; David W. Latham; Thomas G. Beatty; Michael B. Lund; Robert J. Siverd; Adam L. Kraus; Patcharapol Wachiraphan; Perry Berlind; Michael L. Calkins; Gilbert A. Esquerdo; John F. Kielkopf; Rudolf B. Kuhn; Mark Manner; Joshua Pepper; Keivan G. Stassun; MIT Kavli Institute for Astrophysics and Space Research; Las Cumbres Observatory Global Telescope Network, Inc; Gemini Observatory; California Institute of Technology; Harvard-Smithsonian Center for Astrophysics; University of Louisville; The University of Texas at Austin; Mahidol University; The University of Arizona; Vanderbilt University; The Ohio State University; South African Astronomical Observatory; Pennsylvania State University; Fisk University; Lehigh University; Spot Observatory; Observatory
    © 2020 The Author(s) We present the discovery of KELT J072709 + 072007 (HD 58730), a very low mass ratio (q ≡ M2/M1 ≈ 0.07) eclipsing binary (EB) identified by the Kilodegree Extremely Little Telescope (KELT) survey. We present the discovery light curve and perform a global analysis of four high-precision ground-based light curves, the Transiting Exoplanets Survey Satellite (TESS) light curve, radial velocity (RV) measurements, Doppler Tomography (DT) measurements, and the broad-band spectral energy distribution. Results from the global analysis are consistent with a fully convective (M2 = 0.22 ± 0.02 M☉) M star transiting a late-B primary (M1 = 3.34+−000709 M☉ and Teff,1 = 11960+−430520 K). We infer that the primary star is 183+−3330 Myr old and that the companion star's radius is inflated by 26 ± 8 per cent relative to the predicted value from a low-mass isochrone of similar age. We separately and analytically fit for the variability in the out-of-eclipse TESS phase curve, finding good agreement between the resulting stellar parameters and those from the global fit. Such systems are valuable for testing theories of binary star formation and understanding how the environment of a star in a close-but-detached binary affects its physical properties. In particular, we examine how a star's properties in such a binary might differ from the properties it would have in isolation.
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    A Large Ground-based Observing Campaign of the Disintegrating Planet K2-22b
    (2018-11-01) Knicole D. Colón; George Zhou; Avi Shporer; Karen A. Collins; Allyson Bieryla; Néstor Espinoza; Felipe Murgas; Petchara Pattarakijwanich; Supachai Awiphan; James D. Armstrong; Jeremy Bailey; Geert Barentsen; Daniel Bayliss; Anurak Chakpor; William D. Cochran; Vikram S. Dhillon; Keith Horne; Michael Ireland; Lucyna Kedziora-Chudczer; John F. Kielkopf; Siramas Komonjinda; David W. Latham; Tom R. Marsh; David E. Mkrtichian; Enric Pallé; David Ruffolo; Ramotholo Sefako; Chris G. Tinney; Suwicha Wannawichian; Suraphong Yuma; Bay Area Environmental Research Institute; Pontificia Universidad Católica de Chile; University of Hawaii System; University of New South Wales (UNSW) Australia; Massachusetts Institute of Technology; University of St Andrews; The University of Warwick; Harvard-Smithsonian Center for Astrophysics; University of Louisville; University of Texas at Austin; Mahidol University; Instituto Astrofisico de Canarias; Australian National University; Max Planck Institut für Astronomie; NASA Goddard Space Flight Center; NASA Ames Research Center; Universidad de la Laguna; South African Astronomical Observatory; University of Sheffield; Chiang Mai University; Millennium Institute of Astrophysics; National Astronomical Research Institute of Thailand
    © 2018. The American Astronomical Society. All rights reserved. We present 45 ground-based photometric observations of the K2-22 system collected between 2016 December and 2017 May, which we use to investigate the evolution of the transit of the disintegrating planet K2-22b. Last observed in early 2015, in these new observations we recover the transit at multiple epochs and measure a typical depth of <1.5%. We find that the distribution of our measured transit depths is comparable to the range of depths measured in observations from 2014 and 2015. These new observations also support ongoing variability in the K2-22b transit shape and time, although the overall shallowness of the transit makes a detailed analysis of these transit parameters difficult. We find no strong evidence of wavelength-dependent transit depths for epochs where we have simultaneous coverage at multiple wavelengths, although our stacked Las Cumbres Observatory data collected over days-to-months timescales are suggestive of a deeper transit at blue wavelengths. We encourage continued high-precision photometric and spectroscopic monitoring of this system in order to further constrain the evolution timescale and to aid comparative studies with the other few known disintegrating planets.
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    VERITAS and Fermi-LAT Observations of TeV Gamma-Ray Sources Discovered by HAWC in the 2HWC Catalog
    (2018-10-10) A. U. Abeysekara; A. Archer; W. Benbow; R. Bird; R. Brose; M. Buchovecky; J. H. Buckley; V. Bugaev; A. J. Chromey; M. P. Connolly; W. Cui; M. K. Daniel; A. Falcone; Q. Feng; J. P. Finley; L. Fortson; A. Furniss; M. Hütten; D. Hanna; O. Hervet; J. Holder; G. Hughes; T. B. Humensky; C. A. Johnson; P. Kaaret; P. Kar; M. Kertzman; D. Kieda; M. Krause; F. Krennrich; S. Kumar; M. J. Lang; T. T.Y. Lin; S. McArthur; P. Moriarty; R. Mukherjee; S. O'Brien; R. A. Ong; A. N. Otte; N. Park; A. Petrashyk; M. Pohl; E. Pueschel; J. Quinn; K. Ragan; P. T. Reynolds; G. T. Richards; E. Roache; C. Rulten; I. Sadeh; M. Santander; G. H. Sembroski; K. Shahinyan; I. Sushch; J. Tyler; S. P. Wakely; A. Weinstein; R. M. Wells; P. Wilcox; A. Wilhelm; D. A. Williams; T. J. Williamson; B. Zitzer; S. Abdollahi; M. Ajello; L. Baldini; G. Barbiellini; D. Bastieri; R. Bellazzini; B. Berenji; E. Bissaldi; R. D. Blandford; R. Bonino; E. Bottacini; T. J. Brandt; P. Bruel; R. Buehler; R. A. Cameron; R. Caputo; P. A. Caraveo; D. Castro; E. Cavazzuti; E. Charles; G. Chiaro; S. Ciprini; J. Cohen-Tanugi; D. Costantin; S. Cutini; F. D'Ammando; F. De Palma; N. Di Lalla; M. Di Mauro; L. Di Venere; A. Dominguez; C. Favuzzi; S. J. Fegan; A. Franckowiak; Y. Fukazawa; S. Funk; P. Fusco; Istituto Nazionale di Fisica Nucleare, Sezione di Trieste; Istituto Nazionale di Fisica Nucleare, Sezione di Perugia; Istituto Nazionale di Fisica Nucleare, Sezione di Bari; Istituto Nazionale di Fisica Nucleare, Sezione di Torino; Istituto Nazionale di Fisica Nucleare, Sezione di Pisa; Istituto Nazionale Di Fisica Nucleare, Sezione di Padova; Laboratoire Univers et Particules de Montpellier; Laboratoire Leprince-Ringuet; Kavli Institute for Particle Astrophysics and Cosmology; Santa Cruz Institute for Particle Physics; INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna; INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan; University of Wisconsin-Madison; Agenzia Spaziale Italiana; California State University, East Bay; Hiroshima University; California State University, Los Angeles; Deutsches Elektronen-Synchrotron (DESY); Columbia University in the City of New York; University of Minnesota Twin Cities; Università di Pisa; Alma Mater Studiorum Università di Bologna; University of California, Los Angeles; Universidad Complutense de Madrid; Clemson University; The Enrico Fermi Institute; University of Utah; The University of Alabama; Tsinghua University; University of Iowa; Università degli Studi di Bari; Universität Potsdam; Harvard-Smithsonian Center for Astrophysics; Georgia Institute of Technology; Università degli Studi di Trieste; Università degli Studi di Napoli Federico II; Università degli Studi di Torino; Washington University in St. Louis; Barnard College; Purdue University; National University of Ireland Galway; NASA Goddard Space Flight Center; DePauw University; University College Dublin; Iowa State University; McGill University; Pennsylvania State University; Cork Institute of Technology; Friedrich-Alexander-Universität Erlangen-Nürnberg; Bartol Research Institute; Università degli Studi di Padova
    © 2018. The American Astronomical Society. All rights reserved. The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not associated with previously known teraelectronvolt (TeV) gamma-ray sources. We have studied 14 of these sources without known counterparts with VERITAS and Fermi-LAT. VERITAS detected weak gamma-ray emission in the 1 TeV-30 TeV band in the region of DA 495, a pulsar wind nebula coinciding with 2HWC J1953+294, confirming the discovery of the source by HAWC. We did not find any counterpart for the selected 14 new HAWC sources from our analysis of Fermi-LAT data for energies higher than 10 GeV. During the search, we detected gigaelectronvolt (GeV) gamma-ray emission coincident with a known TeV pulsar wind nebula, SNR G54.1+0.3 (VER J1930+188), and a 2HWC source, 2HWC J1930+188. The fluxes for isolated, steady sources in the 2HWC catalog are generally in good agreement with those measured by imaging atmospheric Cherenkov telescopes. However, the VERITAS fluxes for SNR G54.1+0.3, DA 495, and TeV J2032+4130 are lower than those measured by HAWC, and several new HAWC sources are not detected by VERITAS. This is likely due to a change in spectral shape, source extension, or the influence of diffuse emission in the source region.