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Title: Long-Term Monitoring Of The High-Energy γ-Ray Emission From Ls I +61°303 And Ls 5039

Journal Article · · The Astrophysical Journal
 [1];  [2];  [3];  [4];  [5];  [3];  [6];  [3];  [7];  [8];  [8];  [8];  [1];  [3];  [9];  [9];  [9];  [10]
  1. Inst. de Ciencies de l'Espai, Barcelona (Spain)
  2. Inst. de Ciencies de l'Espai, Barcelona (Spain); Univ. Autonoma de Barcelona (Spain). Inst. Catalana de Recerca i Estudis Avancats (ICREA)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States)
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of Southampton (United Kingdom)
  6. Inst. de Planetologie et d'Astrophysique de Grenoble (France)
  7. Univ. Paris, Gif-sur-Yvette (France)
  8. Chinese Academy of Sciences (CAS), Beijing (China)
  9. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  10. Univ. of Cambridge (United Kingdom). Cavendish Lab.
+ Show Author Affiliations

The Fermi Large Area Telescope (LAT) reported the first definitive GeV detections of the binaries LS I +61°303 and LS 5039 in the first year after its launch in 2008 June. These detections were unambiguous as a consequence of the reduced positional uncertainty and the detection of modulated γ-ray emission on the corresponding orbital periods. An analysis of new data from the LAT, comprising 30 months of observations, identifies a change in the γ-ray behavior of LS I +61°303. An increase in flux is detected in 2009 March and a steady decline in the orbital flux modulation is observed. Significant emission up to 30 GeV is detected by the LAT; prior data sets led to upper limits only. Contemporaneous TeV observations no longer detected the source, or found it—in one orbit—close to periastron, far from the phases at which the source previously appeared at TeV energies. The detailed numerical simulations and models that exist within the literature do not predict or explain many of these features now observed at GeV and TeV energies. New ideas and models are needed to fully explain and understand this behavior. A detailed phase-resolved analysis of the spectral characterization of LS I +61°303 in the GeV regime ascribes a power law with an exponential cutoff spectrum along each analyzed portion of the system's orbit. The on-source exposure of LS 5039 is also substantially increased with respect to our prior publication. In this case, whereas the general γ-ray properties remain consistent, the increased statistics of the current data set allows for a deeper investigation of its orbital and spectral evolution.

Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1356750
Journal Information:
The Astrophysical Journal, Vol. 749, Issue 1; ISSN 0004-637X
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 60 works
Citation information provided by
Web of Science

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Variability in the orbital profiles of the X-ray emission of the gamma-ray binary LS I +61 303 text January 2010
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Unveiling the super-orbital modulation of LSI +61 303 in X-rays text January 2012
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Discovery of very high energy gamma-rays associated with an X-ray binary text January 2005
3.9 day orbital modulation in the TeV gamma-ray flux and spectrum from the X-ray binary LS 5039 text January 2006

Cited By (20)

Gamma-ray binaries and related systems journal August 2013
Modelling Jets, Tori and Flares in Pulsar Wind Nebulae journal March 2017
Phenomenology of gamma-ray emitting binaries journal February 2019
X-ray follow-ups of XSS J12270-4859: a low-mass X-ray binary with gamma-ray Fermi -LAT association journal January 2013
H α observations of the γ -ray-emitting Be/X-ray binary LSI+61°303: orbital modulation, disk truncation, and long-term variability journal November 2013
Super-orbital variability of LS I +61°303 at TeV energies journal June 2016
Overview of non-transient γ -ray binaries and prospects for the Cherenkov Telescope Array journal November 2019
H.E.S.S. and Fermi -LAT observations of PSR B1259–63/LS 2883 during its 2014 and 2017 periastron passages journal January 2020
GeV Detection of HESS J0632+057 journal September 2017
The Likely Fermi Detection of the Be X-Ray Binary GRO J1008-57 journal September 2019
Discovery of the Galactic High-mass Gamma-Ray Binary 4FGL J1405.1−6119 journal October 2019
Discovery of the Galactic High-Mass Gamma-ray Binary 4FGL J1405.1-6119 collection January 2019
Super-orbital variability of LS I +61°303 at TeV energies text January 2016
Modelling Jets, Tori and Flares in Pulsar Wind Nebulae text January 2017
H.E.S.S. and Fermi-LAT observations of PSR B1259-63/LS 2883 during its 2014 and 2017 periastron passages text January 2019
H-alpha observations of the gamma-ray-emitting Be/X-ray binary LSI+61303: orbital modulation, disk truncation, and long-term variability text January 2013
Super-orbital variability of LS I +61°303 at TeV energies text January 2016
Phenomenology of gamma-ray emitting binaries preprint January 2019
Overview of non-transient gamma-ray binaries and prospects for the Cherenkov Telescope Array text January 2019
H.E.S.S. and Fermi-LAT observations of PSR B1259–63/LS 2883 during its 2014 and 2017 periastron passages text January 2020

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