X-Ray Imaging Observations of the High-mass γ-Ray Binary HESS J0632+057

• Published in: The Astrophysical journal Vol. 925; no. 1; pp. 20 - 33
• Main Authors: Kargaltsev, O., Klingler, N. J., Hare, J., Volkov, I.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 01.01.2022; IOP Publishing for the American Astronomical Society; IOP Publishing
• Subjects: Astronomy; Astrophysics; Compact objects; Emission; Emissions; Gamma-ray sources; High mass x-ray binary stars; Imaging spectrometers; Near infrared radiation; Space telescopes; Thermal plasmas; X ray imagery; X ray telescopes; X-ray astronomy; X-ray sources
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac3822

The Chandra X-ray Observatory (CXO)imaged the high-massγ-ray binary (HMGB) HESS8J0632+057 with the Advanced CCD Imaging Spectrometer (ACIS). We analyzed the CXO data to-9gether with 967 ks of archival imaging Swift-XRT observations. On arcsecond scales we find a hint10of asymmetric extended emission. On arcminute scales, there is a region of extended emission (“the11blob”) which is located≈5.5′east of the binary. The blob is seen in both the CXO-ACIS and the12Swift-XRT images but it does not have a counterpart in the radio, NIR, IR, or optical images. The13ACIS spectrum of the blob fits either an absorbed power-law model with Γ'2.6, or a thermal plasma14model withkT'3 keV. Since the blob’s NH is significantly larger than that of the binary we conclude15that the blob and binary are not directly related. The somewhat larger very deep XRT image suggests16that the binary may be located within a shell (or cavity). The four ACIS spectra taken within the∼2017day interval near the light curve minimum suggests that the NH is varying on timescales of days, pos-18sibly due to the inhomogenous circumbinary environment. The XRT spectra extracted from the wider19orbital phase intervals support significant changes in NH near the light curve maximum/minimum,20which may be responsible for the substantial systematic residuals seen near 1 keV, and provide tenta-21tive evidence for a Fe line at 6.4 keV. We find no significant periodic signal in the ACIS data up to 0.156 Hz.