A variable ULX and possible IMBH candidate in M51a

Earnshaw, Hannah P.; Roberts, T. P.; Heil, L.; Mezcua, Mar; Walton, D. J.; Done, Chris; Harrison, Fiona A.; Lansbury, G. B.; Middleton, Matthew; Sutton, Andrew D.

doi:10.1093/mnras/stv2945

Cited by 42 publications

(59 citation statements)

References 82 publications

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“…The presence of IMBHs was also suggested in the HLXs 2XMM J011942.7+032421 (Sutton et al 2012;Gutiérrez & Moon 2014) and CXO J122518.6+144545 (Jonker et al 2010;Heida et al 2015), and in the ULXs NGC 1313 X-1 (e.g., Pasham et al 2015), NGC 5408 X-1 (e.g., Dheeraj & Strohmayer 2012), and M51 ULX-7 (Earnshaw et al 2016), among others. The HLX 2XMM J011942.7+032421, with a peak X-ray luminosity of 1.53 ×10 41 erg s −1 , presents short-term variability and its X-ray spectrum can be fitted by multicolor disk emission with a mass ≥ 1900 M (Sutton et al 2012).…”

Section: Ultraluminous X-ray Sourcesmentioning

confidence: 90%

“…The recent detection of an ultra-fast outflow in the X-ray spectrum of NGC 5408 X-1 finally confirmed the super-Eddington accreting nature of this source ). Last but not least, the ULX-7 in the spiral galaxy M51 is suggested to be powered by an IMBH based on its hard spectrum, high rms variability, and the lower limit on the BH mass of 1.6 × 10 3 M derived using the relationship between BH mass and high frequency break in the power spectrum (Earnshaw et al 2016). However, a pulsar nature for this ULX cannot be ruled out.…”

Section: Ultraluminous X-ray Sourcesmentioning

confidence: 99%

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Observational evidence for intermediate-mass black holes

Mezcua

2017

Int. J. Mod. Phys. D

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254

219

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Intermediate-mass black holes (IMBHs), with masses in the range 100 − 10 6 M , are the link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the seeds from which SMBHs grow, which would explain the existence of quasars with BH masses of up to 10 10 M when the Universe was only 0.8 Gyr old. The detection and study of IMBHs has thus strong implications for understanding how SMBHs form and grow, which is ultimately linked to galaxy formation and growth, as well as for studies of the universality of BH accretion or the epoch of reionisation. Proving the existence of seed BHs in the early Universe is not yet feasible with the current instrumentation; however, those seeds that did not grow into SMBHs can be found as IMBHs in the nearby Universe. In this review I summarize the different scenarios proposed for the formation of IMBHs and gather all the observational evidence for the few hundreds of nearby IMBH candidates found in dwarf galaxies, globular clusters, and ultraluminous X-ray sources, as well as the possible discovery of a few seed BHs at high redshift. I discuss some of their properties, such as X-ray weakness and location in the BH mass scaling relations, and the possibility to discover IMBHs through high velocity clouds, tidal disruption events, gravitational waves, or accretion disks in active galactic nuclei. I finalize with the prospects for the detection of IMBHs with up-coming observatories.

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Section: Ultraluminous X-ray Sourcesmentioning

confidence: 90%

Section: Ultraluminous X-ray Sourcesmentioning

confidence: 99%

Observational evidence for intermediate-mass black holes

Mezcua

2017

Int. J. Mod. Phys. D

Self Cite

254

219

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show abstract

“…The class of ultraluminous X-ray sources (ULX) have Lx ∼ 10 39 − 10 42 erg s −1 (Swartz et al 2004), and it is thought that some of these are powered by pulsars, stellarmass black holes, and possibly intermediate-mass black holes for the most luminous of them (Mezcua et al 2013;Earnshaw et al 2016;Mezcua et al 2016;Bachetti 2016). The pulsars and stellar-mass black holes are associated with highmass star formation, and hence with molecular clouds.…”

Section: Discussionmentioning

confidence: 99%

Non-equilibrium chemistry and destruction of CO by X-ray flares

Mackey

Walch

Seifried

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Sources of X-rays such as active galactic nuclei and X-ray binaries are often variable by orders of magnitude in luminosity over timescales of years. During and after these flares the surrounding gas is out of chemical and thermal equilibrium. We introduce a new implementation of X-ray radiative transfer coupled to a time-dependent chemical network for use in 3D magnetohydrodynamical simulations. A static fractal molecular cloud is irradiated with X-rays of different intensity, and the chemical and thermal evolution of the cloud are studied. For a simulated 10 5 M fractal cloud, an X-ray flux < 0.01 erg cm −2 s −1 allows the cloud to remain molecular, whereas most of the CO and H 2 are destroyed for a flux of ≥ 1 erg cm −2 s −1 . The effects of an X-ray flare, which suddenly increases the X-ray flux by 10 5 × are then studied. A cloud exposed to a bright flare has 99% of its CO destroyed in 10-20 years, whereas it takes > 10 3 years for 99% of the H 2 to be destroyed. CO is primarily destroyed by locally generated far-UV emission from collisions between non-thermal electrons and H 2 ; He + only becomes an important destruction agent when the CO abundance is already very small. After the flare is over, CO re-forms and approaches its equilibrium abundance after 10 3 -10 5 years. This implies that molecular clouds close to Sgr A in the Galactic Centre may still be out of chemical equilibrium, and we predict the existence of clouds near flaring X-ray sources in which CO has been mostly destroyed but H is fully molecular.

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“…Pasham et al, 2014;Wrobel et al, 2016;Earnshaw et al, 2016;Arca-Sedda, 2016). Kiziltan et al (2017) found an indirect evidence for an IMBH of about 2200 M ⊙ at the center of the globular cluster 47 Tucanae based on the dynamical state constrained by the timing data of millisecond pulsars.…”

Section: Working Definition Of a (Supermassive) Black Holementioning

confidence: 99%

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

Eckart

Hüttemann²,

Kiefer³

et al. 2017

Found Phys

122

105

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The compact and, with 4.3±0.3×106 M ⊙ , very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity. The strongest evidence for this is provided by measurements of stellar orbits, variable X-ray emission, and strongly variable polarized near-infrared emission from the location of the radio source Sagittarius A* (SgrA*) in the middle of the central stellar cluster. Simultaneous near-infrared and X-ray observations of SgrA* have revealed insights into the emission mechanisms responsible for the powerful near-infrared and X-ray flares from within a few tens to one hundred Schwarzschild radii of such a putative SMBH at the center of the Milky Way. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target of the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) observations currently being prepared. These observations in combination with the infrared interferometry experiment GRAVITY at the Very Large Telescope Interferometer (VLTI) and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. The large body of evidence continues to discriminate the identification of SgrA* as a SMBH from alternative possibilities. It is, however, unclear when the ever mounting evidence for SgrA* being associated with a SMBH will suffice as a convincing proof. Additional compelling evidence may come from future gravitational wave observatories. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about "(Anti)Realism and Underdetermination", as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts.

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A variable ULX and possible IMBH candidate in M51a

Cited by 42 publications

References 82 publications

Observational evidence for intermediate-mass black holes

Observational evidence for intermediate-mass black holes

Non-equilibrium chemistry and destruction of CO by X-ray flares

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?

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