2015/02/03 by Yi Xing, Zhongxiang Wang, Xing, Yi +3
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astrophysical Phenomena and Observations #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research #astro-ph.HE
paper · pdf · doi:10.48550/arxiv.1502.00733
11 page, 4 figures, submitted to PASJ
arxiv created 2015/02/03 · openalex publication_date 2015/02/03 · arxiv updated 2015/02/04 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We report the Fermi Large Area Telescope (LAT) detection of a γ-ray source at the position of SAX J1808.4-3658. This transient low-mass X-ray binary contains an accreting millisecond puslar, which is only seen during its month-long outbursts and likely switches to be rotation powered during its quiescent state. Emission from the γ-ray source can be described by a power law with an exponential cutoff, the characteristic form for pulsar emission. Folding the source's 2.0--300 GeV photons at the binary orbital period, a weak modulation is seen (with an H-test value of ∼17). In addition, three sets of archival XMM-Newton data for the source field are analyzed, and we find only one X-ray source with 3--4σ flux variations in the 2σ error circle of the γ-ray source. However based on the X-ray properties, this X-ray source is not likely a background AGN, the major class of Fermi sources detected by LAT. These results support the possible association between the γ-ray source and SAX J1808.4-3658 and thus the scenario that the millisecond pulsar is rotation powered in the quiescent state. Considering a source distance of 3.5 kpc for SAX J1808.4-3658, the 0.1--300 GeV luminosity is 5.7× 1033 erg s-1, implying a γ-ray conversion efficiency of 63% for the pulsar in this binary.