MASS MEASUREMENTS OF BLACK HOLES IN X-RAY TRANSIENTS: IS THERE A MASS GAP?

By Laura Kreidberg, C. Bailyn, W. Farr, Vicky Kalogera. 2012

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We explore possible systematic errors in the mass measurements of stellar mass black holes (BHs). We find that significant errors can arise from the assumption of zero or constant emission from the accretion flow, which is commonly used when determining orbital inclination by modeling ellipsoidal variations. For A0620−00, the system with the best available data, we show that typical data sets and analysis procedures can lead to systematic underestimates of the inclination by 10° or more. A careful examination of the available data for the 15 other X-ray transients with low-mass donors suggests that this effect may significantly reduce the BH mass estimates in several other cases, most notably that of GRO J0422+32. Assuming that GRO J0422+32 behaves similarly to A0620−00, the reduction in the mass of GRO J0422+32 fills the mass gap between the low end of the distribution and the maximum theoretical neutron star mass, as has been identified in previous studies. Otherwise, we find that the mass distribution retains other previously identified characteristics, namely a peak around 8 M☉, a paucity of sources with masses below 5 M☉, and a sharp drop-off above 10 M☉.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Instrumentation

View Paper: https://www.semanticscholar.org/paper/64abed4cdb1b34700f367f2710b5cfbc870a9562

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Citations in the corpus

THE RATE OF BINARY BLACK HOLE MERGERS INFERRED FROM ADVANCED LIGO OBSERVATIONS SURROUNDING GW150914 (2016, background): “…there are indications of a mass gap between the heaviest neutron stars and the lightest BHs (Özel et al. 2010; Farr et al. 2011); however, see Kreidberg et al. (2012) for an alternative explanation for the dearth of BH mass estimates 140 The source- and observer-frame masses are related by a…”
Precise mass and spin measurements for a stellar-mass black hole through X-ray timing: the case of GRO J1655-40 (2013, background): “…for a limited number of binary systems (about 15) with particular characteristics (i.e. detectable companion star and relatively high orbital inclination) through dynamical studies of their binary motion requiring long and often difficult multiwavelength observations (see Kreidberg et al. 2012).”
MISSING BLACK HOLES UNVEIL THE SUPERNOVA EXPLOSION MECHANISM (2011, background): “According to Kreidberg et al. (2012), this leads to a systematic bias in the inclination measurements and hence the BH masses, and may mistakenly push low-mass BHs out of the mass gap.”
DOUBLE COMPACT OBJECTS. II. COSMOLOGICAL MERGER RATES (2013, background): “As suggested by Kreidberg et al. (2012), the presence of the mass gap feature may be a result of systematic errors arising from misinterpretation of the BH binary light curve analyses.”
DOUBLE COMPACT OBJECTS. III. GRAVITATIONAL-WAVE DETECTION RATES (2015, unknown): “When used in the context of binary evolution models, this SN engine successfully reproduces the mass gap (Belczynski et al. 2012b) observed in Galactic X-ray binaries (Bailyn et al. 1998; Özel et al. 2010; but see also Kreidberg et al. 2012).”
Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo (2018, background): “While the existence and nature of this gap are still uncertain(Kreidberg et al. 2012), it is proposed to exist between the most massive neutron stars (Freire et al. 2008; Özel & Freire 2016; Margalit & Metzger 2017; 2.1–2.5 M ) and the lightest BHs (∼5 M ).”
BlackCAT: A catalogue of stellar-mass black holes in X-ray transients (2015, background): “However, Kreidberg et al. (2012) warn about a large source of systematic errors that arise from a possible underestimation of the inclination angle i.”
Binary Black Hole Mergers in the First Advanced LIGO Observing Run (2016, background): “[84]).”
Where Are LIGO’s Big Black Holes? (2017, methodology): “…sample of ∼ 20 BHs in X-ray binary systems was used to infer the BH mass distribution (Özel et al. 2010; Farr et al. 2011), providing strong evidence for the existence of a mass gap between the heaviest neutron star (NS) (∼ 2–3M ) and the lightest BH (∼ 4–5M ) (but see also Kreidberg et al. 2012).”
COMPACT BINARY MERGER RATES: COMPARISON WITH LIGO/VIRGO UPPER LIMITS (2015, background): “It has been proposed that the gap is just an ob- servational artifact (Kreidberg et al. 2012).”
The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes (2014, methodology): “solar mass in their lifetimes. For an early list of estimated black hole mass functions, see [115]; for 22 more recent updates, see [116, 117], and for an object-by-object discussion see Section 5 of [9]. At face value it appears that there is a gap between the masses of neutron stars and black hole”
The effect of pair-instability mass loss on black-hole mergers (2016, background): “It has been explained either in terms of observational bias on BH mass measurements (Kreidberg et al. 2012), or in the context of the supernova explosion engine (Belczynski et al. 2012), or in terms of the transition of compressible nuclear matter into incompressible quark-superfluid that…”
THE LANDSCAPE OF THE NEUTRINO MECHANISM OF CORE-COLLAPSE SUPERNOVAE: NEUTRON STAR AND BLACK HOLE MASS FUNCTIONS, EXPLOSION ENERGIES, AND NICKEL YIELDS (2014, background): “The gap between neutron star and black hole masses is found in black-hole low-mass X-ray binaries, where the probability distribution peaks at ∼ 5M⊙ (e.g. Bailyn et al. 1998; Özel et al. 2010; Farr et al. 2011; Kreidberg et al. 2012).”