Ultraluminous X-ray sources in the Chandra and XMM-Newton era

Abstract Ultraluminous X-ray sources (ULXs) are accreting black holes that may contain the missing population of intermediate mass black holes or reflect super-Eddington accretion physics. Ten years of Chandra and XMM-Newton observations of ULXs, integrated by multiband studies of their counterparts, have produced a wealth of observational data and phenomenological classifications. We review the properties of their host galaxies, list popular spectral models and implications for standard and supercritical accretion physics, demonstrate how X-ray timing of these objects places constraints on their masses. We also review multiwavelength studies of ULXs, including the optical emission of the binary system and nebulosity around them. We summarize that three classes of black holes could power ULXs: normal stellar mass black holes (∼10M⊙), massive stellar black holes (≲100M⊙), and intermediate mass black holes (102–104M⊙). We collect evidence for the presence of these three types of compact objects, including caveat of each interpretation, and briefly review their formation processes.

[1]  Marat Gilfanov,et al.  Low-mass X-ray binaries as a stellar mass indicator for the host galaxy , 2004 .

[2]  D. Psaltis,et al.  Tracing the power-law component in the energy spectrum of black hole candidates as a function of the QPO frequency , 2002, astro-ph/0210517.

[3]  T. P. Roberts,et al.  Challenging times: a re-analysis of NGC 5408 X-1 , 2010, 1009.2686.

[4]  S. E. Woosley,et al.  The Nucleosynthetic Signature of Population III , 2002 .

[5]  M. Reid,et al.  THE MASS OF THE BLACK HOLE IN CYGNUS X-1 , 2011, 1106.3689.

[6]  P. Kaaret,et al.  Origin of the X-Ray Quasi-periodic Oscillations and Identification of a Transient Ultraluminous X-Ray Source in M82 , 2007, 0706.3233.

[7]  Key results from an XMM-Newton and Chandra study of a new sample of extreme ULXs from the 2XMM catalogue , 2010, 1011.4460.

[8]  S. E. Woosley,et al.  How Massive Single Stars End Their Life , 2003 .

[9]  P. Casella,et al.  The ABC of low-frequency quasi-periodic oscillations in Black-Hole Candidates: analogies with Z-sources , 2005, astro-ph/0504318.

[10]  James R. Graham,et al.  Kinematic Masses of Super-Star Clusters in M82 from High-Resolution Near-Infrared Spectroscopy , 2003, astro-ph/0306373.

[11]  R. Di Stefano,et al.  An Unusual Spectral State of an Ultraluminous Very Soft X-Ray Source during Outburst , 2005, astro-ph/0509567.

[12]  Jay M. Pasachoff,et al.  The X‐Ray Universe , 1985 .

[13]  Roeland P. van der Marel,et al.  NEW LIMITS ON AN INTERMEDIATE-MASS BLACK HOLE IN OMEGA CENTAURI. I. HUBBLE SPACE TELESCOPE PHOTOMETRY AND PROPER MOTIONS , 2009, 0905.0627.

[14]  T. Quinn,et al.  WANDERING BLACK HOLES IN BRIGHT DISK GALAXY HALOS , 2010, 1008.5147.

[15]  Shiro Ueno,et al.  Chandra observations of the luminous infrared galaxy NGC 3256 , 2001, astro-ph/0109198.

[16]  Philip Kaaret,et al.  Radio Emission from an Ultraluminous X-ray Source , 2003, Science.

[17]  D. Raine,et al.  Accretion power in astrophysics , 1985 .

[18]  M. Mori,et al.  Supercritical Accretion Flows around Black Holes: Two-dimensional, Radiation Pressure-dominated Disks with Photon Trapping , 2005, astro-ph/0504168.

[19]  G. Trinchieri,et al.  X-ray observations of spiral galaxies. II. Images and spectral parameters of 13 galaxies , 1987 .

[20]  Heidelberg,et al.  Runaway collisions in young star clusters - II. Numerical results , 2005, astro-ph/0503130.

[21]  J. Ostriker,et al.  The Luminosity Function of Galactic X-Ray Sources - a Cutoff and a , 1973 .

[22]  Martin J. Ward,et al.  ROSAT PSPC observations of the extragalactic H II region NGC 5408 , 1993 .

[23]  S. Ravindranath,et al.  BL Lac identification for the ultraluminous X-ray source observed in the direction of NGC 4698 , 2002, astro-ph/0209500.

[24]  J. Stocke,et al.  A luminous X-ray binary in M82 , 1991 .

[25]  P. Kaaret,et al.  Confirmation of the 62 Day X-Ray Periodicity from M82 , 2007, 0707.2055.

[26]  Richard Mushotzky,et al.  The star-forming environment of an ultraluminous X-ray source in NGC 4559: an optical study , 2004 .

[27]  A. Loeb,et al.  Stellar black holes at the dawn of the universe , 2011, 1102.1891.

[28]  Ray A. Lucas,et al.  Nonnuclear Hyper/Ultraluminous X-Ray Sources in the Starbursting Cartwheel Ring Galaxy , 2003, astro-ph/0309253.

[29]  J. N. Reeves,et al.  A deep XMM-Newton observation of the ultraluminous X-ray source HoII X-1 : the case against a 1000 solar mass black hole , 2005 .

[30]  M. Pakull,et al.  Detection of an X-ray-ionized nebula around the black hole candidate binary LMC X-l , 1986, Nature.

[31]  T. Kallman,et al.  THE FIRST DETECTION OF [O iv] FROM AN ULTRALUMINOUS X-RAY SOURCE WITH SPITZER. I. OBSERVATIONAL RESULTS FOR HOLMBERG II ULX , 2009, 0904.1837.

[32]  R. Fiorito,et al.  Spectral Index and Quasi-Periodic Oscillation Frequency Correlation in Black Hole Sources: Observational Evidence of Two Phases and Phase Transition in Black Holes , 2004, astro-ph/0405360.

[33]  T. P. Roberts,et al.  XMM–Newton observations of the brightest ultraluminous X-ray sources , 2006, astro-ph/0601651.

[34]  C. Done,et al.  X-ray spectral variability in the ultraluminous X-ray source Holmberg IX X−1 , 2009, 0912.2906.

[35]  Tom Oosterloo,et al.  A dark jet dominates the power output of the stellar black hole Cygnus X-1 , 2005, Nature.

[36]  Ralf S. Klessen,et al.  American Institute of Physics Conference Series , 2010 .

[37]  Gravitational Radiation from Intermediate-Mass Black Holes , 2002, astro-ph/0206404.

[38]  I. Papadakis,et al.  The scaling of X-ray variability with luminosity in Ultra-luminous X-ray sources , 2010, 1010.2904.

[39]  M. Servillat,et al.  X-RAY VARIABILITY AND HARDNESS OF ESO 243–49 HLX-1: CLEAR EVIDENCE FOR SPECTRAL STATE TRANSITIONS , 2011, 1108.4405.

[40]  E. Colbert,et al.  A Catalog of Candidate Intermediate-Luminosity X-Ray Objects , 2002, astro-ph/0204002.

[41]  Richard F. Mushotzky,et al.  XMM-Newton Observations of an Intermediate X-Ray Object in NGC 2276 , 2004 .

[42]  M. Mori,et al.  Does the Slim-Disk Model Correctly Consider Photon-trapping Effects? , 2002, astro-ph/0203425.

[43]  Mitchell C. Begelman,et al.  Super-Eddington Fluxes from Thin Accretion Disks? , 2002, astro-ph/0203030.

[44]  Allyn Tennant,et al.  CHANDRA DISCOVERY OF LUMINOUS SUPERSOFT X-RAY SOURCES IN M81 , 2002 .

[45]  F. Yuan.  Luminous hot accretion discs , 2000, astro-ph/0009207.

[46]  P. Kaaret,et al.  COMPACT OPTICAL COUNTERPARTS OF ULTRALUMINOUS X-RAY SOURCES , 2011, 1106.0315.

[47]  Philip Kaaret,et al.  Optical Counterpart of the Ultraluminous X-Ray Source IC 342 X-1 , 2007, 0711.4131.

[48]  L. Zampieri,et al.  Low metallicity natal environments and black hole masses in Ultraluminous X-ray Sources , 2009, 0909.1017.

[49]  C. Motch,et al.  A 300-parsec-long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793 , 2010, Nature.

[50]  M. Colpi,et al.  Low metallicity and ultra-luminous X-ray sources in the Cartwheel galaxy , 2009, 0902.3540.

[51]  T. P. Roberts E.J.M. Colbert.  Chandra reveals a black-hole X-ray binary within the ultraluminous supernova remnant MF 16 , 2003 .

[52]  U. Durham,et al.  A systematic study of variability in a sample of ultraluminous X-ray sources , 2009, 0905.1265.

[53]  Aya Kubota,et al.  Disc-corona energetics in the very high state of Galactic black holes , 2006 .

[54]  The Open University,et al.  The X-Ray Properties of M101 ULX-1 = CXOKM101 J140332.74+542102 , 2005 .

[55]  Didier Barret,et al.  An intermediate-mass black hole of over 500 solar masses in the galaxy ESO 243-49 , 2009, Nature.

[56]  P. Kaaret,et al.  Spectral State Transitions of the Ultraluminous X-Ray Sources X-1 and X-2 in NGC 1313 , 2006, astro-ph/0608066.

[57]  J. McClintock,et al.  Compact Stellar X-Ray Sources: Black hole binaries , 2006 .

[58]  Takamitsu Miyaji,et al.  Multiple Components of the Luminous Compact X-Ray Source at the Edge of Holmberg II Observed by ASCA and ROSAT , 2001 .

[59]  P. Kaaret,et al.  IDENTIFICATION OF THE X-RAY THERMAL DOMINANT STATE IN AN ULTRALUMINOUS X-RAY SOURCE IN M82 , 2010, 1003.0283.

[60]  M. D. Caballero-Garcia,et al.  X-ray reflection in a sample of X-ray bright ultraluminous X-ray sources , 2009, 0910.2418.

[61]  C. Steinhardt,et al.  The quasar mass-luminosity plane - I. A sub-Eddington limit for quasars , 2009, 0911.1355.

[62]  D. Swartz,et al.  Do Ultraluminous X-Ray Sources Exist in Dwarf Galaxies? , 2008, 0803.1984.

[63]  Harvard-Smithsonian Center for Astrophysics,et al.  Discovery of a Luminous, Variable, Off-Center Source in the Nucleus of M82 with the Chandra High-Resolution Camera , 2000, astro-ph/0009250.

[64]  Mass Limits For Black Hole Formation , 1999, astro-ph/9902315.

[65]  Marat Gilfanov,et al.  Lx-SFR relation in star-forming galaxies , 2003 .

[66]  L. Ho,et al.  XMM–Newton observations of ultraluminous X–ray sources in nearby galaxies , 2002, astro-ph/0206418.

[67]  M. B. Davies,et al.  Ultraluminous X-Ray Sources in External Galaxies , 2001 .

[68]  T. P. Roberts,et al.  The Ultraluminous State , 2009, 0905.4076.

[69]  S. Kitamoto,et al.  TIME-DEPENDENT DISK ACCRETION IN X-RAY NOVA MUSCAE 1991 , 1994 .

[70]  N. Gehrels,et al.  FIRST EVIDENCE FOR SPECTRAL STATE TRANSITIONS IN THE ESO 243-49 HYPERLUMINOUS X-RAY SOURCE HLX-1 , 2009, 0909.4458.

[71]  J. M. Miller,et al.  X-Ray Spectroscopic Evidence for Intermediate-Mass Black Holes: Cool Accretion Disks in Two Ultraluminous X-Ray Sources , 2003 .

[72]  Luca Zampieri,et al.  Optical emission from massive donors in ultraluminous X-ray source binary systems , 2007, 0710.2815.

[73]  QSO-Galaxy Association and Gravitational Lensing , 2004, astro-ph/0409009.

[74]  L. Ho,et al.  An Intermediate-Mass Black Hole in the Globular Cluster G1: Improved Significance from New Keck and Hubble Space Telescope Observations , 2005, astro-ph/0508251.

[75]  R. Soria.  Bridging the gap between stellar-mass black holes and ultraluminous X-ray sources , 2007, 0707.2049.

[76]  M. Servillat,et al.  THE COOL ACCRETION DISK IN ESO 243-49 HLX-1: FURTHER EVIDENCE OF AN INTERMEDIATE-MASS BLACK HOLE , 2011, 1104.2614.

[77]  A. Zdziarski,et al.  Black hole accretion disks with coronae , 1994 .

[78]  S. Mineshige,et al.  Supercritical accretion and ULXs , 2011 .

[79]  J. Lasota,et al.  Slim Accretion Disks , 1988 .

[80]  Philip Kaaret,et al.  A 62 Day X-Ray Periodicity and an X-Ray Flare from the Ultraluminous X-Ray Source in M82 , 2006, astro-ph/0604029.

[81]  C. Motch,et al.  The supergiant optical counterpart of ULX P13 in NGC 7793 , 2010, 1011.4215.

[82]  P. Kaaret,et al.  X-RAY SPECTRAL STATE IS NOT CORRELATED WITH LUMINOSITY IN HOLMBERG II X-1 , 2010, 1011.2231.

[83]  Richard E. Griffiths,et al.  A transition to a low/soft state in the ultraluminous compact X-ray source Holmberg II X-1 , 2004 .

[84]  Jifeng Liu.  No Periodicity Revealed for an “Eclipsing” Ultraluminous Supersoft X-Ray Source in M81 , 2008, 0802.2966.

[85]  Shuang-Nan Zhang,et al.  COMPARING THE ACCRETION DISK EVOLUTION OF BLACK HOLE AND NEUTRON STAR X-RAY BINARIES FROM LOW TO SUPER-EDDINGTON LUMINOSITY , 2011, 1107.5171.

[86]  A. M. Read.  Chandra observations of the Mice , 2003 .

[87]  C. Carilli,et al.  A RELATIONSHIP BETWEEN AGN JET POWER AND RADIO POWER , 2010, 1006.5699.

[88]  W. M. Goss,et al.  A High-Resolution Radio Study of the W50-SS 433 System and the Surrounding Medium , 1998 .

[89]  A. Treves,et al.  X-Ray and Optical Variability of the Ultraluminous X-Ray Source NGC 1313 X-2 , 2006, 1011.2043.

[90]  R. McCray,et al.  X-ray nebular models , 1982 .

[91]  J. Orosz,et al.  CORRELATIONS BETWEEN LOW-FREQUENCY QUASI-PERIODIC OSCILLATIONS AND SPECTRAL PARAMETERS IN XTE J1550(564 AND GRO J1655(40 , 1999, astro-ph/9910519.

[92]  Toshikazu Ebisuzaki,et al.  UvA-DARE ( Digital Academic Repository ) Missing Link Found ? The " Runaway " Path to Supermassive Black Holes , 2001 .

[93]  A. King.  Outflows from quasars and Ultra-Luminous X-ray sources , 2003, astro-ph/0309524.

[94]  Philip Kaaret,et al.  XMM-Newton Observations of Ultraluminous X-Ray Sources in Nearby Galaxies , 2005, astro-ph/0507562.

[95]  G. Ferland,et al.  CLOUDY 90: Numerical Simulation of Plasmas and Their Spectra , 1998 .

[96]  Yasushi Fukazawa,et al.  Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342 , 2000, astro-ph/0011232.

[97]  P. Kaaret,et al.  High-resolution imaging of the He II λ4686 emission line nebula associated with the ultraluminous X-ray source in Holmberg II , 2004, astro-ph/0407031.

[98]  Junichiro Makino,et al.  Formation of massive black holes through runaway collisions in dense young star clusters , 2004, Nature.

[99]  Tsunefumi Mizuno,et al.  Slim-Disk Model for Ultraluminous X-Ray Sources , 2000, astro-ph/0011434.

[100]  P. Kaaret,et al.  SWIFT OBSERVATIONS OF THE ULTRALUMINOUS X-RAY SOURCE HOLMBERG IX X-1 , 2010, ECSA 2010.

[101]  Tod E. Strohmayer,et al.  EVIDENCE FOR AN INTERMEDIATE-MASS BLACK HOLE IN NGC 5408 X-1 , 2009, 0911.1076.

[102]  R. S. Warwick,et al.  A Chandra observation of the interacting pair of galaxies NGC 4485/4490 , 2002 .

[103]  A. Zezas,et al.  The Orbital Period of the Wolf-Rayet Binary IC 10 X-1: Dynamic Evidence that the Compact Object Is a Black Hole , 2007, 0709.2892.

[104]  Andrew King,et al.  Accretion Power in Astrophysics: Third Edition , 2002 .

[105]  M. Cropper,et al.  Quasi-periodic Variability in NGC 5408 X-1 , 2007, astro-ph/0701390.

[106]  Robert A. Gruendl,et al.  An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources , 2005, astro-ph/0511540.

[107]  Richard F. Mushotzky,et al.  XMM Observations of an IXO in NGC 2276 , 2003 .

[108]  T. P. Roberts,et al.  X-ray observations of ultraluminous X-ray sources , 2007, 0706.2562.

[109]  Jochen Greiner,et al.  RXTE Observations of QPOs in the Black Hole Candidate GRS 1915+105 , 1997 .

[110]  Aya Kubota,et al.  An optically thick inner corona geometry for the Very High State Galactic Black Hole XTE J1550-564 , 2005, astro-ph/0511030.

[111]  T. Belloni,et al.  A Unified Model for Black Hole X-Ray Binary Jets? , 2004, astro-ph/0506469.

[112]  S. Komissarov,et al.  Magnetic acceleration of relativistic active galactic nucleus jets , 2007 .

[113]  Aya Kubota,et al.  The Nature of Ultraluminous Compact X-Ray Sources in Nearby Spiral Galaxies , 2000, astro-ph/0001009.

[114]  Sera Markoff,et al.  A jet model for the broadband spectrum of XTE J1118+480. Synchrotron emission from radio to X-rays in the , 2000, astro-ph/0010560.

[115]  A. de Koter,et al.  On the evolution and fate of super-massive stars , 2007, 0710.1181.

[116]  M. Dopita,et al.  Radiative shock wave theory. III. The nature of the optical emission in young supernova remnants , 1984 .

[117]  R. Price,et al.  Accretion disk coronae and Cygnus X-1 , 1977 .

[118]  Lin F. Yang,et al.  THE OPTICAL COUNTERPART OF NGC 1313 X-1 , 2011, 1103.5281.

[119]  R. Narayan,et al.  Advection-Dominated Accretion and the Spectral States of Black Hole X-Ray Binaries: Application to Nova Muscae 1991 , 1997 .

[120]  A. R. Rao,et al.  Associated spectral and temporal state transition of the bright ULX NGC 1313 X-1 , 2009, 0905.3819.

[121]  Ucsd,et al.  The variability plane of accreting compact objects , 2007, 0706.2959.

[122]  Martin J. Rees,et al.  ApJ, in press Preprint typeset using L ATEX style emulateapj v. 04/03/99 MASSIVE BLACK HOLES AS POPULATION III REMNANTS , 2001 .

[123]  Chris L. Fryer,et al.  ON THE MAXIMUM MASS OF STELLAR BLACK HOLES , 2009, 0904.2784.

[124]  Roberto Soria,et al.  On the weakness of disc models in bright ULXs , 2006 .

[125]  T. Roberts,et al.  X-ray spectral evolution in the ultraluminous X-ray source M33 X-8 , 2011 .

[126]  P. Kaaret,et al.  DISCOVERY OF MILLIHERTZ X-RAY OSCILLATIONS IN A TRANSIENT ULTRALUMINOUS X-RAY SOURCE IN M82 , 2010, 1001.3456.

[127]  Olivier Schnurr,et al.  The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M⊙ stellar mass limit , 2010, 1007.3284.

[128]  E. T. Harlaftis,et al.  The rotational broadening and the mass of the donor star of GRS 1915+105 , 2004 .

[129]  R. S. Warwick,et al.  XMM–Newton EPIC observations of the ultraluminous X‐ray source NGC 5204 X‐1 , 2004 .

[131]  T. Strohmayer.  DISCOVERY OF A 115 DAY ORBITAL PERIOD IN THE ULTRALUMINOUS X-RAY SOURCE NGC 5408 X-1 , 2009, 0911.1339.

[132]  S. F. Sanchez,et al.  Integral field spectroscopy of the ultraluminous X-ray source Holmberg II X-1 , 2005 .

[133]  Heidelberg,et al.  Formation of Massive Black Holes in Dense Star Clusters , 2003 .

[134]  Philipp Podsiadlowski,et al.  On the formation and evolution of black hole binaries , 2003 .

[135]  University of Leicester,et al.  No) dynamical constraints on the mass of the black hole in two ULXs , 2010, 1011.2155.

[136]  D. Swartz,et al.  A Complete Sample of ULX Host Galaxies , 2011, 1108.1372.

[137]  P. Mucciarelli,et al.  A variable Quasi‐Periodic Oscillation in M82 X‐1. Timing and spectral analysis of XMM–Newton and RossiXTE observations , 2005, astro-ph/0509796.

[138]  B. Miller,et al.  The Optical Counterpart to the Extremely Luminous X-Ray Source near Holmberg IX: A Possible Supershell in a Tidal Tail , 1995 .

[139]  Philip Kaaret,et al.  submitted to ApJ Preprint typeset using L ATEX style emulateapj v. 10/09/06 A PHOTOIONIZED NEBULA SURROUNDING AND VARIABLE OPTICAL CONTINUUM EMISSION FROM THE ULTRALUMINOUS X-RAY SOURCE IN NGC 5408 , 2022 .

[140]  Yet another galaxy identification for an ultraluminous X-ray source , 2003, astro-ph/0305452.

[141]  R. Weaver,et al.  Interstellar bubbles. II - Structure and evolution , 1977 .

[142]  Edward Colbert,et al.  Old and Young X-Ray Point Source Populations in Nearby Galaxies , 2003, astro-ph/0305476.

[143]  Spectroscopy of optical counterparts of ultraluminous X-ray sources , 2006, astro-ph/0612765.

[144]  The jet‐powered optical nebula of Cygnus X–1 , 2007, astro-ph/0701645.

[145]  Giuseppina Fabbiano,et al.  X Rays From Normal Galaxies , 1989 .

[146]  Simon F. Portegies Zwart,et al.  The Runaway Growth of Intermediate-Mass Black Holes in Dense Star Clusters , 2002, astro-ph/0201055.

[147]  T. P. Roberts,et al.  The unusual supernova remnant surrounding the ultraluminous X-ray source IC 342 X-1 , 2003, astro-ph/0303110.

[148]  S. L. Snowden,et al.  Chandra X-Ray Sources in M101 , 2001, astro-ph/0107133.

[149]  R. Sunyaev,et al.  X-ray emission from star-forming galaxies – I. High-mass X-ray binaries , 2011, 1105.4610.

[150]  Philip Kaaret,et al.  Optical Studies of the Ultraluminous X-Ray Source NGC 1313 X-2 , 2007, astro-ph/0703697.

[151]  Low-frequency constraints on the spectra of the lobes of the microquasar GRS 1758–258 , 2005, astro-ph/0501060.

[152]  V. Kalogera,et al.  Theoretical Black Hole Mass Distributions , 1999, astro-ph/9911312.

[153]  Roberto Soria,et al.  DIFFERENT TYPES OF ULTRALUMINOUS X-RAY SOURCES IN NGC 4631 , 2009, 0901.4302.

[154]  Marta Volonteri,et al.  Formation of supermassive black holes , 2010, 1003.4404.

[155]  M. Gierliński,et al.  Black hole accretion discs: reality confronts theory , 2003, astro-ph/0307333.

[156]  R. Soria.  Hard and soft spectral states of ULXs , 2010, 1009.5986.

[157]  C. Urry,et al.  Luminosity enhancement in relativistic jets and altered luminosity functions for beamed objects , 1984 .

[158]  Arnold H. Rots,et al.  Chandra Observations of “The Antennae” Galaxies (NGC 4038/4039). III. X-Ray Properties and Multiwavelength Associations of the X-Ray Source Population , 2002 .

[159]  P. Kaaret,et al.  X-RAY MONITORING OF ULTRALUMINOUS X-RAY SOURCES , 2009, 0907.5415.

[160]  B. Patel,et al.  Populations of supersoft X-ray sources: Novae, tidal disruption, Type Ia supernovae, accretion-induced collapse, ionization, and intermediatemass black holes? , 2009, 0909.2046.

[161]  G. Trinchieri,et al.  The Cartwheel galaxy with XMM-Newton , 2009, 0905.1230.

[162]  Alexei V. Filippenko,et al.  On IC 10 X-1, the Most Massive Known Stellar-Mass Black Hole , 2008, 0802.2716.

[163]  P. Kaaret,et al.  OPTICAL PROPERTIES OF THE ULTRALUMINOUS X-RAY SOURCE HOLMBERG IX X-1 AND ITS STELLAR ENVIRONMENT , 2011, 1104.5523.

[164]  C. Leitherer,et al.  A LIBRARY OF THEORETICAL ULTRAVIOLET SPECTRA OF MASSIVE, HOT STARS FOR EVOLUTIONARY SYNTHESIS , 2010, 1006.5624.

[165]  Charles D. Bailyn,et al.  A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33 , 2007, Nature.

[166]  Lev Titarchuk,et al.  The Extended Power Law as an Intrinsic Signature for a Black Hole , 1997, astro-ph/9708255.

[167]  Douglas A. Swartz,et al.  The Ultraluminous X-Ray Source Population from the Chandra Archive of Galaxies , 2004, astro-ph/0405498.

[168]  N. Madhusudhan,et al.  Models for the Observable System Parameters of Ultraluminous X-Ray Sources , 2007, 0710.3854.

[169]  J. R. Bond,et al.  The Evolution and fate of Very Massive Objects , 1984 .

[170]  Denis Foo Kune,et al.  Starburst99: Synthesis Models for Galaxies with Active Star Formation , 1999, astro-ph/9902334.

[171]  L. Titarchuk,et al.  DETERMINATION OF BLACK HOLE MASSES IN GALACTIC BLACK HOLE BINARIES USING SCALING OF SPECTRAL AND VARIABILITY CHARACTERISTICS , 2009, 0902.2852.

[172]  S. Cenko,et al.  LARGE HIGHLY IONIZED NEBULAE AROUND ULTRA-LUMINOUS X-RAY SOURCES , 2011, 1103.2773.

[173]  Diego Altamirano,et al.  The long-term evolution of the accreting millisecond X-ray pulsar Swift J1756.9−2508 , 2009, 0910.2920.

[174]  Chandra X-Ray Imaging of the Interacting Starburst Galaxy System NGC 7714/7715: Tidal Ultraluminous X-Ray Sources, Emergent Wind, and Resolved H II Regions , 2004, astro-ph/0412039.

[175]  G. Trinchieri,et al.  On the compact nature of the most luminous ULX in the Cartwheel ring , 2006, astro-ph/0610586.

[176]  P. Kaaret,et al.  TRANSITION TO THE DISK DOMINANT STATE OF A NEW ULTRALUMINOUS X-RAY SOURCE IN M82 , 2010, 1005.0469.

[177]  Stephen S. Eikenberry,et al.  The Ultraluminous X-Ray Source X-37 Is a Background Quasar in the Antennae Galaxies , 2005 .

[178]  V. La Parola,et al.  The Ultraluminous M81 X-9 Source: 20 Years’ Variability and Spectral States , 2001, astro-ph/0103250.

[179]  Isabella M. Gioia,et al.  The Einstein Observatory Extended Medium-Sensitivity Survey. II - The optical identifications , 1991 .

[180]  A. Athey,et al.  X-Ray Spectral Properties of Low-Mass X-Ray Binaries in Nearby Galaxies , 2003 .

[181]  Douglas A. Swartz,et al.  ULTRALUMINOUS X-RAY SOURCE CORRELATIONS WITH STAR-FORMING REGIONS , 2009, 0907.4718.

[182]  P. Kaaret,et al.  XMM-NEWTON OBSERVATIONS OF NGC 247: X-RAY POPULATION AND A SUPERSOFT ULTRALUMINOUS X-RAY SOURCE , 2011, 1101.3363.

[183]  W. Blair,et al.  The optical counterpart to the luminous X-ray supernova remnant in NGC 6946 , 1994 .

[184]  P. Kaaret,et al.  DETECTION OF STRONG SHORT-TERM VARIABILITY IN NGC 6946 X-1 , 2010, 1008.2065.

[185]  P. Kaaret,et al.  A Comparison of Ultraluminous X-Ray Sources in NGC 1399 and the Antennae Galaxies (NGC 4038/4039) , 2006, astro-ph/0608024.

[186]  Roberto Soria,et al.  A variable ultra-luminous X-ray source in the colliding galaxy NGC 7714 , 2004 .

[187]  M. Dopita,et al.  Spectral Signatures of Fast Shocks. II. Optical Diagnostic Diagrams , 1995 .

[188]  Ph. Podsiadlowski,et al.  Stellar-mass black hole binaries as ultraluminous X-ray sources , 2005 .

[189]  A. Athey,et al.  The lack of very ultraluminous X-ray sources in early-type galaxies , 2003, astro-ph/0312393.

[190]  J. Krolik,et al.  Detailed Atmosphere Model Fits to Disk-dominated ULX Spectra , 2008, 0803.3607.

[191]  K. Wiersema,et al.  New observations of ULX supershells, and their implications , 2010, 1011.0598.

[192]  Usa,et al.  The evolution of the timing properties of the black-hole transient GX 339-4 during its 2002/2003 outburst , 2005, astro-ph/0504577.

[193]  C. Lang,et al.  A Radio Nebula Surrounding the Ultraluminous X-Ray Source in NGC 5408 , 2007, 0705.1978.

[194]  Chris M. Copperwheat,et al.  Optical and infrared signatures of ultra-luminous X-ray sources , 2005 .

[195]  Giuseppina Fabbiano,et al.  Chandra Observations of “The Antennae” Galaxies (NGC 4038/4039). IV. The X-Ray Source Luminosity Function and the Nature of Ultraluminous X-Ray Sources , 2002 .

[196]  Aya Kubota,et al.  Accretion Disk Spectra of Ultraluminous X-Ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources , 2003 .

[197]  G. Fabbiano,et al.  A Variable Ultraluminous Supersoft X-Ray Source in ``The Antennae'': Stellar-Mass Black Hole or White Dwarf? , 2003 .

[198]  Ling Zhu,et al.  CALIBRATING THE CORRELATION BETWEEN BLACK HOLE MASS AND X-RAY VARIABILITY AMPLITUDE: X-RAY ONLY BLACK HOLE MASS ESTIMATES FOR ACTIVE GALACTIC NUCLEI AND ULTRA-LUMINOUS X-RAY SOURCES , 2009, 0912.2636.

[199]  Walter Dehnen,et al.  Hierarchical merging, ultraluminous and hyperluminous X-ray sources , 2004 .

[200]  Kinwah Wu,et al.  Populations of X-ray Binaries and the Dynamical History of their Host Galaxies , 2001, Publications of the Astronomical Society of Australia.

[201]  C. M. Copperwheat,et al.  Irradiation models for ULXs and fits to optical data , 2007 .

[202]  A. Zezas,et al.  ROSAT observations of the dwarf star‐forming galaxy Holmberg II (UGC 4305) , 1999, astro-ph/9903355.

[203]  R. Perna,et al.  How rapidly do neutron stars spin at birth , 2007, 0712.1040.

[204]  S. Rappaport,et al.  Models of Ultraluminous X-Ray Sources with Intermediate-Mass Black Holes , 2005, astro-ph/0511393.

[205]  E. Salpeter,et al.  The interaction of X-ray sources with optically thin environments. , 1969 .

[206]  P. Kaaret.  Optical Sources near the Bright X-Ray Source in NGC 1073 , 2005, astro-ph/0505031.

[208]  G. Trinchieri,et al.  A thorough study of the intriguing X-ray emission from the Cartwheel ring , 2004, astro-ph/0407446.

[209]  R. Larson.  Early star formation and the evolution of the stellar initial mass function in galaxies , 1998, astro-ph/9808145.

[210]  K. Holley-Bockelmann,et al.  INTERPRETATION OF THE 115 DAY PERIODIC MODULATION IN THE X-RAY FLUX OF NGC 5408 X-1 , 2010, 1010.5247.

[211]  I. Mirabel,et al.  A catalogue of ultraluminous X-ray sources in external galaxies , 2005 .

[212]  P. Kaaret.  Open questions on black hole binaries , 2008 .

[213]  Z. Kuncic,et al.  THE XMM-NEWTON LONG LOOK OF NGC 1365: LACK OF A HIGH/SOFT STATE IN ITS ULTRALUMINOUS X-RAY SOURCES , 2009, 0901.3750.

[214]  R. Mushotzky.  Ultra-luminous sources in nearby galaxies , 2006 .

[215]  N. Langer,et al.  Wind modelling of very massive stars up to 300 solar masses , 2011, 1105.0556.

[216]  S. Corbel,et al.  Radio lobes and X‐ray hotspots in the microquasar S26 , 2010, 1008.0394.

[217]  Zhen Yan,et al.  STATE TRANSITIONS IN BRIGHT GALACTIC X-RAY BINARIES: LUMINOSITIES SPAN BY TWO ORDERS OF MAGNITUDE , 2009, 0907.3515.

[218]  R. S. Warwick,et al.  A ROSAT High Resolution Imager survey of bright nearby galaxies , 2000 .

[219]  H. Arp,et al.  New optical spectra and general discussion on the nature of ULXs , 2004, astro-ph/0401103.

[220]  G. Fabbiano.  The X-ray emission of M81 and its nucleus , 1988 .

[221]  D. Wong,et al.  DIRECT DETECTION OF AN ULTRALUMINOUS ULTRAVIOLET SOURCE , 2010, 1003.4257.

[222]  M. Bottcher,et al.  The ultraluminous X-ray source NGC 1313 X-2. Its optical counterpart and environment , 2008, 0805.4011.

[223]  P. Uttley,et al.  Active galactic nuclei as scaled-up Galactic black holes , 2006, Nature.

[224]  R. Fender,et al.  An ultraluminous X-ray microquasar in NGC 5408? , 2006 .

[225]  S. Mineshige,et al.  GLOBAL STRUCTURE OF THREE DISTINCT ACCRETION FLOWS AND OUTFLOWS AROUND BLACK HOLES FROM TWO-DIMENSIONAL RADIATION-MAGNETOHYDRODYNAMIC SIMULATIONS , 2011, 1105.5474.

[226]  D. Steeghs,et al.  THE 2003 OUTBURST OF THE X-RAY TRANSIENT H1743−322: COMPARISONS WITH THE BLACK HOLE MICROQUASAR XTE J1550−564 , 2007, 0705.1034.

[227]  Xiang-Dong Li,et al.  A Fallback Disk Model for Ultraluminous X-Ray Sources , 2003, astro-ph/0309321.

[228]  N. Gehrels,et al.  THE ORIGIN OF VARIABILITY OF THE INTERMEDIATE-MASS BLACK-HOLE ULX SYSTEM HLX-1 IN ESO 243-49 , 2011, 1102.4336.

[229]  A. R. King,et al.  The nature of SS433 and the ultraluminous X-ray sources , 2006, astro-ph/0604497.

[230]  Ronald A. Remillard,et al.  X-Ray Properties of Black-Hole Binaries , 2006, astro-ph/0606352.

[231]  G. Di Cocco,et al.  XMM–Newton observations of the ultraluminous nuclear X-ray source in M 33 , 2004 .

[232]  Sera Markoff,et al.  Population X: Are the super-Eddington X-ray sources beamed jets in microblazars or intermediate mass black holes? , 2002 .

[233]  A. Zezas,et al.  A Minisurvey of X-Ray Point Sources in Starburst and Nonstarburst Galaxies , 2002 .

[234]  Marat Gilfanov,et al.  High mass x-ray binaries as a star formation rate indicator in distant galaxies , 2002 .

[235]  U. Cambridge,et al.  Weighing the black holes in ultraluminous X‐ray sources through timing , 2008, 0804.3378.

[236]  Juri Poutanen,et al.  Supercritically accreting stellar mass black holes as ultraluminous X-ray sources , 2006, astro-ph/0609274.

[237]  S. McMillan,et al.  INTERMEDIATE-MASS BLACK HOLES IN EARLY GLOBULAR CLUSTERS , 2010, 1003.3470.

[238]  T. Roberts,et al.  Testing the Paradigm that Ultraluminous X-Ray Sources as a Class Represent Accreting Intermediate-Mass Black Holes , 2008, 0807.1547.

[239]  L. Winter,et al.  XMM-Newton Archival Study of the Ultraluminous X-Ray Population in Nearby Galaxies , 2005, astro-ph/0512480.

[240]  China.,et al.  SPECTRAL STATES AND EVOLUTION OF ULTRALUMINOUS X-RAY SOURCES , 2009, 0902.2607.

[241]  P. Kaaret,et al.  Spectral Evolution of NGC 1313 X-2: Evidence against the Cool Disk Model , 2007, astro-ph/0703598.

[242]  Jifeng Liu,et al.  HUBBLE SPACE TELESCOPE MONITORING REVEALS A 6.1 DAY PERIOD FOR AN ULTRALUMINOUS X-RAY SOURCE IN NGC 1313 , 2008 .