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Title: SAX J1808.4$-$3658, an accreting millisecond pulsar shining in gamma rays?

We report the detection of a possible gamma-ray counterpart of the accreting millisec- ond pulsar SAXJ1808.4–3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a re- gion of 15° radius around the position of the pulsar reveals a point gamma-ray source detected at a significance of ~6σ (Test Statistic TS = 32), with position compatible with that of SAXJ1808.4–3658 within 95% Confidence Level. The energy flux in the energy range between 0.6 GeV and 10 GeV amounts to (2.1 ± 0.5) × 10 -12 erg cm -2 s -1 and the spectrum is well-represented by a power-law function with photon index 2.1±0.1. We searched for significant variation of the flux at the spin frequency of the pulsar and for orbital modulation, taking into account the trials due to the uncertain- ties in the position, the orbital motion of the pulsar and the intrinsic evolution of the pulsar spin. No significant deviation from a constant flux at any time scale was found, preventing a firm identification via time variability. Nonetheless, the association of the LAT source as the gamma-ray counterpart of SAXJ1808.4–3658 would match the emission expected frommore » the millisecond pulsar, if it switches on as a rotation-powered source during X-ray quiescence.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [4] ;  [4]
  1. Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona (Spain)
  2. Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona (Spain); Univ. of Amsterdam (Netherlands)
  3. Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona (Spain); Univ. Autonoma de Barcelona (Spain). Inst. Catalana de Recerca i Estudis Avancats (ICREA)
  4. Univ. degli Studi di Cagliari (Italy)
  5. Univ. of Palermo (Italy)
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 456; Journal Issue: 3; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1355681

de Oña Wilhelmi, E., Papitto, A., Li, J., Rea, N., Torres, D. F., Burderi, L., Di Salvo, T., Iaria, R., Riggio, A., and Sanna, A.. SAX J1808.4$-$3658, an accreting millisecond pulsar shining in gamma rays?. United States: N. p., Web. doi:10.1093/mnras/stv2695.
de Oña Wilhelmi, E., Papitto, A., Li, J., Rea, N., Torres, D. F., Burderi, L., Di Salvo, T., Iaria, R., Riggio, A., & Sanna, A.. SAX J1808.4$-$3658, an accreting millisecond pulsar shining in gamma rays?. United States. doi:10.1093/mnras/stv2695.
de Oña Wilhelmi, E., Papitto, A., Li, J., Rea, N., Torres, D. F., Burderi, L., Di Salvo, T., Iaria, R., Riggio, A., and Sanna, A.. 2015. "SAX J1808.4$-$3658, an accreting millisecond pulsar shining in gamma rays?". United States. doi:10.1093/mnras/stv2695. https://www.osti.gov/servlets/purl/1355681.
@article{osti_1355681,
title = {SAX J1808.4$-$3658, an accreting millisecond pulsar shining in gamma rays?},
author = {de Oña Wilhelmi, E. and Papitto, A. and Li, J. and Rea, N. and Torres, D. F. and Burderi, L. and Di Salvo, T. and Iaria, R. and Riggio, A. and Sanna, A.},
abstractNote = {We report the detection of a possible gamma-ray counterpart of the accreting millisec- ond pulsar SAXJ1808.4–3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a re- gion of 15° radius around the position of the pulsar reveals a point gamma-ray source detected at a significance of ~6σ (Test Statistic TS = 32), with position compatible with that of SAXJ1808.4–3658 within 95% Confidence Level. The energy flux in the energy range between 0.6 GeV and 10 GeV amounts to (2.1 ± 0.5) × 10-12 erg cm-2 s-1 and the spectrum is well-represented by a power-law function with photon index 2.1±0.1. We searched for significant variation of the flux at the spin frequency of the pulsar and for orbital modulation, taking into account the trials due to the uncertain- ties in the position, the orbital motion of the pulsar and the intrinsic evolution of the pulsar spin. No significant deviation from a constant flux at any time scale was found, preventing a firm identification via time variability. Nonetheless, the association of the LAT source as the gamma-ray counterpart of SAXJ1808.4–3658 would match the emission expected from the millisecond pulsar, if it switches on as a rotation-powered source during X-ray quiescence.},
doi = {10.1093/mnras/stv2695},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 3,
volume = 456,
place = {United States},
year = {2015},
month = {12}
}