A 2-hr binary period for the black hole transient MAXI J0637-430

Abstract

We revisit various sets of published results from X-ray and optical studies of the Galactic black hole (BH) candidate MAXI J0637-430, which went into outburst in 2019. Combining the previously reported values of peak outburst luminosity, best-fitting radii of inner and outer accretion disk, viewing angle, exponential decay timescale and peak-to-peak separation of the He II 4686 disk emission line, we improve the constraints on the system parameters. We estimate a heliocentric distance d = (8.7 +/- 2.3) kpc, a projected Galactocentric distance R = (13.2 +/- 1.8) kpc and a height |z| = (3.1 +/- 0.8) kpc from the Galactic plane. It is the currently known Milky Way BH candidate located farthest from the Galactic Centre. We infer a BH mass M_1 = (5.1 +/- 1.6) M_{sun}, a spin parameter a* <~ 0.25, a donor star mass M_2 = (0.25 +/- 0.07) M_{sun}, a peak Eddington ratio lambda = 0.17 +/- 0.11 and a binary period P_{orb} = 2.2^{+0.8}_{-0.6} hr. This is the shortest period measured or estimated so far for any Galactic BH X-ray binary. If the donor star is a main-sequence dwarf, such a period corresponds to the evolutionary stage where orbital shrinking is driven by gravitational radiation and the star has regained contact with its Roche lobe (low end of the period gap). The three Galactic BHs with the shortest period (<~3 hr) are also those with the highest vertical distance from the Galactic plane (>~2 kpc). This is probably because binaries with higher binding energies can survive faster natal kicks.

8 pages, 300 kB, accepted by MNRAS on 2022 July 4

References in corpus (12)

• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The Donor Stars of Cataclysmic Variables
• A Grid of Relativistic, non-LTE Accretion Disk Models for Spectral Fitting of Black Hole Binaries
• The Galactic distribution of X-ray binaries and its implications for compact object formation and natal kicks
• Angular Momentum Transport in Accretion Disks and its Implications for Spin Estimates in Black Hole Binaries
• Mass transfer during low mass X-ray transient decays
• Phase-dependent study of near-infrared disk emission lines in LB-1
• Delimiting the black hole mass in the X-ray transient MAXI J1659-152 with H$\alpha$ spectroscopy
• Selection Effects on the Orbital Period Distribution of Low Mass Black Hole X-ray Binaries
• The peculiar spectral evolution of the new X-ray transient MAXI J0637-430
• Using Optical Spectroscopy to Map the Geometry and Structure of the Irradiated Accretion Discs in Low-mass X-ray Binaries: The Pilot-Study of MAXI J0637$-$430
• The long-term optical evolution of the black hole candidate MAXI J1659-152

Cited by in corpus (6)

• Back to business: SLX 1746--331 after 13 years of silence
• The bright black hole X-ray binary 4U 1543--47 during 2021 outburst: a thick accretion disk inflated by high luminosity
• A Dependable Distance Estimator to Black Hole Low-Mass X-ray Binaries
• The spin measurement of MAXI J0637-430: a black hole candidate with high disk density
• Empirical correlation between masses of black holes and Wolf-Rayet stars derived from their mass distributions in spectroscopic binaries
• A search for optical counterparts in quiescent black hole X-ray transients