A LOW-MASS MAIN-SEQUENCE STAR AND ACCRETION DISK IN THE VERY FAINT X-RAY TRANSIENT M15 X-3

作者：Arnason R M^*; Sivakoff G R; Heinke C O; Cohn H N; Lugger P M

来源：Astrophysical Journal, 2015, 807(1): 52.

DOI：10.1088/0004-637X/807/1/52

• accretion, accretion disks
• galaxies: clusters: individual (M15)
• stars: neutron
• techniques: photometric
• X-rays: binaries
• X-rays: individual (M15 X-3)

We present near-simultaneous Chandra/Hubble Space Telescope (HST) observations of the very faint (L-x < 10(36) erg s(-1)) X-ray transient source M15 X-3, as well as unpublished archival Chandra observations of M15 X-3. The Chandra observations constrain the luminosity of M15 X-3 to be < 10(34) erg s(-1) in all observed epochs. The X-ray spectrum shows evidence of curvature, and prefers a fit to a broken power law with break energy E-break =2.7(-0.6)(+0.4) keV, and power-law indices of Gamma(1) =1.3(-0.2)(+0.1) and Gamma(2) = 1.92(-0.2)(+0.2) over a single power law. We fit our new F438W (B), F606W (broad V), and F814W (I) HST data on the blue optical counterpart with a model for an accretion disk and a metal-poor main-sequence star. From this fit, we determine the companion to be consistent with a main-sequence star of mass 0.440(-0.060)(+0.035) M-circle dot in a similar to 4 hr orbit. X-ray irradiation of the companion is likely to be a factor in the optical emission from the system, which permits the companion to be smaller than calculated above, but larger than 0.15 M-circle dot at the 3 sigma confidence level. M15 X-3 seems to be inconsistent with all suggested hypotheses explaining very faint transient behavior, except for magnetospherically inhibited accretion.

• 出版日期2015-7-1