Mass Measurements of Stellar and Intermediate Mass Black-Holes

Abstract

We discuss the method, and potential systematic effects therein, used for measuring the mass of stellar-mass black holes in X-ray binaries. We restrict our discussion to the method that relies on the validity of Kepler's laws; we refer to this method as the dynamical method. We briefly discuss the implications of the mass distribution of stellar-mass black holes and provide an outlook for future measurements. Further, we investigate the evidence for the existence of intermediate-mass black holes i.e. black holes with masses above 100 Msun, the limit to the black hole mass that can be produced by stellar evolution in the current Universe.

28 pages, 12 figures. Accepted for publication in Space Science Reviews (DOI 10.1007/s11214-013-0030-6). Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher). Replaced with a new version including a new Fig.1, fixed two references, some typos and minor style changes

References in corpus (125)

• A Fundamental Relation Between Supermassive Black Holes and Their Host Galaxies
• X-ray Properties of Black-Hole Binaries
• A fundamental plane of black hole activity
• Compact Remnant Mass Function: Dependence on the Explosion Mechanism and Metallicity
• Massive Black Holes as Population III Remnants
• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• The Nuclear Equation of State and Neutron Star Masses
• A Scheme to Unify Low-Power Accreting Black Holes - Jet-Dominated Accretion Flows and the Radio/X-Ray Correlation
• The Black Hole Mass Distribution in the Galaxy
• The runaway growth of intermediate-mass black holes in dense star clusters
• The Nature of Accreting Black Holes in Nearby Galaxy Nuclei
• On The Maximum Mass of Stellar Black Holes
• Theoretical Black Hole Mass Distributions
• The Mass Distribution of Stellar-Mass Black Holes
• An Intermediate-mass Black Hole of Over 500 Solar Masses in the Galaxy ESO 243-49
• Production of Intermediate-Mass Black Holes in Globular Clusters
• MERLIN observations of relativistic ejections from GRS 1915+105
• Super-Eddington Fluxes from Thin Accretion Disks?
• Effect of Primordial Black Holes on the Cosmic Microwave Background and Cosmological Parameter Estimates
• A New Sample of Low-mass Black Holes in Active Galaxies
• Global Structure of Three Distinct Accretion Flows and Outflows around Black Holes through Two-Dimensional Radiation-Magnetohydrodynamic Simulations
• The Mass of the Black Hole in Cygnus X-1
• On the formation and evolution of black-hole binaries
• ULTRACAM: an ultra-fast, triple-beam CCD camera for high-speed astrophysics
• The distances to Galactic low-mass X-ray binaries: consequences for black hole luminosities and kicks
• An unusually massive stellar black hole in the Galaxy
• The Formation and Evolution of Massive Black Holes
• Optical Observations of GRO J1655-40 in Quiescence I: A Precise Mass for the Black Hole Primary
• An Intermediate-Mass Black Hole in the Globular Cluster G1: Improved Significance from New Keck and Hubble Space Telescope Observations
• Missing Black Holes Unveil The Supernova Explosion Mechanism
• Mass Measurements of Black Holes in X-Ray Transients: Is There a Mass Gap?
• A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33
• Dynamical Evidence for a Black Hole in GX 339-4
• Primordial Black Holes as Dark Matter: The Power Spectrum and Evaporation of Early Structures
• Two stellar-mass black holes in the globular cluster M22
• Dynamical Evidence for a Black Hole in the Microquasar XTE J1550-564
• Discovery of X-ray QPOs from an Ultra-luminous X-ray Source in M82: Evidence Against Beaming
• A Black Hole in the Superluminal source SAX J1819.3-2525 (V4641 Sgr)
• Optical and Infrared Photometry of the Micro-Quasar GRO J1655-40 in Quiescence
• A 20 Thousand Solar Mass Black Hole in the Stellar Cluster G1
• Population X: Are the super-Eddington X-ray sources beamed jets in microblazars or intermediate mass black holes?
• The Trigonometric Parallax of Cygnus X-1
• An Improved Dynamical Model for the Microquasar XTE J1550-564
• The mass donor of Scorpius X-1 revealed
• A Dynamical Model for the Globular Cluster G1
• A New Dynamical Model for the Black Hole Binary LMC X-1
• Formation of a Black Hole in the Dark
• On IC 10 X-1, the Most Massive Known Stellar-Mass Black Hole
• The Inclination of the Soft X-ray Transient A0620--00 and the Mass of its Black Hole
• 2XMM Ultraluminous X-Ray Source Candidates in Nearby Galaxies
• Near-Infrared Spectroscopy of Low Mass X-ray Binaries : Accretion Disk Contamination and Compact Object Mass Determination in V404 Cyg and Cen X-4
• Revisiting a fundamental test of the disc instability model for X-ray binaries
• The quiescent light curve and evolutionary state of GRO J1655-40
• Orbital Parameters for the Soft X-ray Transient 4U 1543-47: Evidence for a Black Hole
• Stellar Mass Black Hole Binaries as ULXs
• Identification of the donor in the X-ray binary GRS 1915+105
• On the masses and evolutionary status of the black hole binary GX 339-4. A twin system of XTE J1550-564?
• Evolutionary constraints on the masses of the components of HDE 226868/Cyg X-1 binary system
• Orbital Parameters for the Black Hole Binary XTE J1650-500
• A Black Hole of > 6 Solar Masses in the X-ray Nova XTE J1118+480
• Populating the Galaxy with low-mass X-ray binaries
• No Evidence for Intermediate-Mass Black Holes in Globular Clusters: Strong Constraints from the JVLA
• The not-so-massive black hole in the microquasar GRS1915+105
• The optical counterpart of an Ultra-luminous X-Ray Source in NGC 5204
• The rotational broadening and the mass of the donor star of GRS 1915+105
• The Halo Black-Hole X-ray Transient XTE J1118+480
• Understanding Compact Object Formation and Natal Kicks. III. The case of Cygnus X-1
• The Inclination Angle of and Mass of the Black Hole in XTE J1118+480
• A Black Hole Nova Obscured by an Inner Disk Torus
• GRO J0422+32: The Lowest Mass Black Hole?
• NGC 300 X-1 is a Wolf-Rayet/Black-Hole binary
• A Black Hole in the X-Ray Nova Velorum 1993
• Determination of Black Hole Mass in Cyg X-1 by Scaling of Spectral Index-QPO Frequency Correlation
• A Multi-Wavelength, Multi-Epoch Study of the Soft X-Ray Transient Prototype, V616 Mon (A0620-00)
• Radio Emission from the Intermediate-mass Black Hole in the Globular Cluster G1
• The origin and fate of short-period low-mass black-hole binaries
• Detection of superhumps in XTE J1118+480 approaching quiescence
• Evidence for quiescent synchrotron emission in the black hole X-ray transient Swift J1357.2-0933
• The Galactic Bulge Survey: outline and X-ray observations
• Why Low-Mass Black-Hole Binaries Are Transient
• Optical emission of the ultraluminous X-ray source NGC 5408 X-1: donor star or irradiated accretion disk?
• X-rays from the Globular Cluster G1: Intermediate Mass Black Hole or Low Mass X-ray Binary?
• A four-year baseline Swift study of enigmatic X-ray transients located near the Galactic center
• Multiwavelength spectral evolution during the 2011 outburst of the very faint X-ray transient Swift J1357.2-0933
• Correlated X-ray and Optical Variability in V404 Cyg in Quiescence
• Formation of the black-hole binary M33 X-7 via mass-exchange in a tight massive system
• The absence of radio emission from the globular cluster G1
• The Mass of the Black Hole in XTE J1118+480
• MMT Observations of the Black Hole Candidate XTE J1118+480 near and in Quiescence
• Inclination Effects and Beaming in Black Hole X-ray Binaries
• A Redshift for the Intermediate Mass Black Hole Candidate HLX-1: Confirmation of its Association with the Galaxy ESO 243-49
• M 33 X-7: ChASeM33 reveals the first eclipsing black hole X-ray binary
• The Ultraviolet Spectrum and Physical Properties of the Mass Donor Star in HD 226868 = Cygnus X-1
• The Birth of an Ultra-Luminous X-ray Source in M83
• A TiO study of the black-hole binary GRO J0422+32 in a very low state
• A Doppler Map and Mass-ratio Constraint for the Black-Hole X-ray Nova Ophiuchi 1977
• The M_BH - sigma relation for intermediate-mass black holes in globular clusters
• Evidence for a Black Hole in the X-ray transient GS 1354-64 (=BW Cir)
• Irradiation models for ULXs and fits to optical data
• Chemical Abundances of the Secondary Star in the Black Hole X-ray Binary XTE J1118+480
• Optical and Infrared Signatures of ULX's
• The Eccentric Accretion Disc of the Black Hole A0620-00
• (No) dynamical constraints on the mass of the black hole in two ULXs
• Fast Photometry of Quiescent Soft X-ray Transients with the Gemini-South Acquisition Camera
• New Hubble Space Telescope imaging of the counterparts to six ultraluminous X-ray sources
• The fast spiral-in of the companion star to the black hole XTE J1118+480
• Multicolour observations of V404 Cyg with ULTRACAM
• Determining the spectroscopic mass ratio in interacting binaries: Application to X-Ray Nova Sco 1994
• Doppler tomography of the black hole binary A0620-00 and the origin of chromospheric emission in quiescent X-ray binaries
• The Black Hole Binary Nova Scorpii 1994 (GRO J1655-40): An improved chemical analysis
• Doppler and modulation tomography of XTE J1118+480 in quiescence
• The nature of the bright ULX X-2 in NGC3921: a Chandra position and HST candidate counterpart
• Keck Infrared Observations of GRO J0422+32 in Quiescence
• Echoes from the companion star in Sco X-1
• Radiation pressure, absorption and AGN feedback in the Chandra Deep Fields
• Near-Infrared Light Curves of the Black Hole Binary A0620-00
• Observations of the X-ray Nova GRO~J0422+32: II: Optical Spectra Approaching Quiescence
• Localization of the X-ray Source in the Globular Cluster G1 with Chandra
• The mass of the black hole in GRS 1915+105: new constraints from IR spectroscopy
• Observations of the quiescent X-ray transients GRS 1124-684 (=GU Mus) and Cen X-4 (=V822 Cen) taken with ULTRACAM on the VLT
• Recoiled star clusters in the Milky Way halo: N-body simulations and a candidate search through SDSS
• Dynamical mass constraints on the ultraluminous X-ray Source NGC 1313 X-2
• The mass of the black hole in LMC X-3
• Variable O VI and N V Emission from the X-ray Binary LMC X-3: Heating of the Black Hole Companion
• Bowen blend echo-tomography of low mass X-ray binaries

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• Properties of OB star-black hole systems derived from detailed binary evolution models
• Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters
• Dynamical confirmation of a black hole in MAXI J1820+070
• Cosmological Simulations of Early Blackhole Formation: Halo Mergers, Tidal Disruption, and the Conditions for Direct Collapse
• Constraining the formation of black-holes in short-period Black-Hole Low-Mass X-ray Binaries
• PRECESSION: Dynamics of spinning black-hole binaries with python
• Search for ultralight bosons in Cygnus X-1 with Advanced LIGO
• Synthetic catalog of black holes in the Milky Way
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• High Resolution Chandra HETG spectroscopy of V404 Cygni in Outburst
• Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries
• Radiation hydrodynamics simulations of the formation of direct-collapse supermassive stellar systems
• Apples and Oranges: Comparing black holes in X-ray binaries and gravitational-wave sources
• Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak
• Multi-mode black hole spectroscopy
• Importance of transient resonances in extreme-mass-ratio inspirals
• Revealing the structure of the outer disks of Be stars
• The merger history of primordial-black-hole binaries
• A FWHM-K2 correlation in Black-Hole transients
• The Formation of a 70 Msun Black Hole at High Metallicity
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• Swift J1357.2-0933: a massive black hole in the Galactic thick disc
• Gravitational Wave Astronomy With TianQin
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• Black hole mass and spin measurements through the Relativistic Precession Model: XTE J1859+226
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• Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE
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• It's written in the massive stars: The role of stellar physics in the formation of black holes
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