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TOPIC: 2XMM J011028.1-460421


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Date:
HLX-1
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Title: Outbursts of the intermediate-mass black hole HLX-1: a wind instability scenario
Author: Roberto Soria, Aina Musaeva, Kinwah Wu, Luca Zampieri, Sara Federle, Ryan Urquhart, Edwin van der Helm, Sean Farrell

We model the intermediate-mass black hole HLX-1, using the Hubble Space Telescope, XMM-Newton and Swift. We quantify the relative contributions of a bluer component, function of X-ray irradiation, and a redder component, constant and likely coming from an old stellar population. We estimate a black hole mass of about (2^{+2}_{-1}) x 10^4 M_{sun}, a spin parameter a/M ~ 0.9 for moderately face-on view, and a peak outburst luminosity of about 0.3 times the Eddington luminosity. We discuss the discrepancy between the characteristic sizes inferred from the short X-ray timescale (R ~ a few 10^{11} cm) and from the optical emitter (R sqrt[cos theta] ~ 2.2 x 10^{13} cm). One possibility is that the optical emitter is a circumbinary disk; however, we disfavour this scenario because it would require a very small donor star. A more plausible scenario is that the disk is large but only the inner annuli are involved in the X-ray outburst. We propose that the recurrent outbursts are caused by an accretion-rate oscillation driven by wind instability in the inner disk. We argue that the system has a long-term-average accretion rate of a few percent Eddington, just below the upper limit of the low/hard state; a wind-driven oscillation can trigger transitions to the high/soft state, with a recurrence period of ~1 year (much longer than the binary period, which we estimate as ~10 days). The oscillation that dominated the system in the last decade is now damped such that the accretion rate no longer reaches the level required to trigger a transition. Finally, we highlight similarities between disk winds in HLX-1 and in the Galactic black hole V404 Cyg.

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Posts: 130165
Date:
ESO 243-49 HLX-1
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ATel 10289: A new outburst of ESO 243-49 HLX-1 after being in quiescence for two years



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RE: 2XMM J011028.1-460421
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Title: Investigating the mass of the intermediate mass black hole candidate HLX-1 with the SLIMBH model
Author: Odele Straub, Olivier Godet, Natalie Webb, Mathieu Servillat, Didier Barret

In this paper we present a comprehensive study of the mass of the intermediate mass black hole candidate HLX-1 in the galaxy ESO 243-49. We analyse the continuum X-ray spectra collected by Swift, XMM-Newton, and Chandra with the slim disc model, SLIMBH, and estimate the black hole mass for the full range of inclination (inc = 0 - 85) and spin (a* = 0 - 0.998). The relativistic SLIMBH model is particularly suited to study high luminosity disc spectra as it incorporates the effects of advection, such as the shift of the inner disc edge towards smaller radii and the increasing height of the disc photosphere (including relativistic ray-tracing from its proper location rather than the mid-plane of the disc). We find for increasing values of inclination that a zero spin black hole has a mass range of 6,300 - 50,900 solar masses and a maximally spinning black hole has a mass between 16,900 - 191,700 solar masses. This is consistent with previous estimates and reinforces the idea that HLX-1 contains an intermediate mass black hole.

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Title: Kinematics of the intermediate mass black hole candidate HLX-1
Authors: Roberto Soria (ICRAR-Curtin), George K. T. Hau (ESO-Santiago), Manfred W. Pakull (Strasbourg University)

We studied the optical spectrum of HLX-1 during its latest outburst, using the FORS2 spectrograph on the Very Large Telescope. We detect an Halpha emission line centered at lambda = (6718.9 0.9) Ang and find that its projected radial velocity with respect to the nucleus of ESO243-49 is (424 27) km/s, while the maximum rotational velocity of the stars in that galaxy is ~209 km/s. This suggests that HLX-1 and its surrounding stars were not formed in situ, but came either from a disrupted dwarf galaxy or from a nuclear recoil. We also find that the Halpha emission line is resolved with full width at half maximum ~400 km/s, suggesting a nebular rather than disk origin for the emission. Its luminosity (L_{Halpha} ~ a few 10^{37} erg/s, equivalent width ~70 Ang) is also consistent with emission from a nebula photo-ionised by HLX-1.

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Posts: 130165
Date:
HLX-1
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Title: Accretion disk parameters in HLX-1
Authors: Roberto Soria (ICRAR-Curtin), George Hau (ESO, Santiago)

We estimate the outer radius of the accretion disk in HLX-1 from its optical brightness and from the exponential timescale of the decline in the X-ray lightcurve after an outburst. We find that the disk is an order of magnitude smaller than the semimajor axis of the orbit. If the disk size is determined by the circularisation radius near periastron, the eccentricity of the binary system must be >~ 0.95. We report on the discovery of H-alpha emission during the 2012 outburst, with a single-peaked, narrow profile (consistent with a nearly face-on view), and a central velocity displaced by ~490 km/s from that of the host galaxy.

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RE: 2XMM J011028.1-460421
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Title: Eccentricity of HLX-1
Authors: Roberto Soria (ICRAR-Curtin University)

I compare the outer radius of the accretion disc in the intermediate-mass black hole candidate HLX-1 as estimated from the UV/optical continuum, with the values estimated from its outburst decline timescales. I fit the Swift 2010 outburst decline lightcurve with an exponential decay, a knee and a linear decay. I find that the disk has an outer radius 10^{12} cm <~ R_{out} <~ 10^{13} cm, only an order of magnitude larger than typical accretion discs in the high/soft state of Galactic black holes. By contrast, the semimajor axis is ~ a few times 10^{14} cm. This discrepancy can be explained with a highly eccentric orbit. I estimate the tidal truncation radius and circularisation radius around the black hole at periastron, and impose that they are similar to or smaller than the outer disk radius. I obtain that e >~ 0.95, that the radius of the donor star is <~ a few solar radii, and that the donor star is not at risk of tidal disruption. If the companion star fills its Roche lobe and impulsively transfers mass only around periastron, secular evolution of the orbit is expected to increase eccentricity and semimajor axis even further. I speculate that such extremely eccentric systems may have the same origin as the S stars in the Galactic centre.

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Date:
HLX-1
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Belching black hole proves a biggie

Outbursts of super-hot gas observed with a CSIRO radio telescope have clinched the identity of the first known "middleweight" black hole, Science Express reports online today.
Called HLX-1 ("hyper-luminous X-ray source 1"), the black hole lies in a galaxy called ESO 243-49, about 300 million light-years away.
Before it was found, astronomers had good evidence for only supermassive black holes - ones a million to a billion times the mass of the Sun - and "stellar mass" ones, three to thirty times the mass of the Sun.

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Posts: 130165
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RE: 2XMM J011028.1-460421
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Title: Investigating slim disk solutions for HLX-1 in ESO 243-49
Authors: O. Godet, B. Plazolles, T. Kawaguchi, J.-P. Lasota, D. Barret, S. A. Farrell, V. Braito, M. Servillat, N. Webb, N. Gehrels

The hyper luminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate mass black hole candidate, displays spectral transitions similar to those observed in Galactic black hole binaries, but with a luminosity 100-1000 times higher. We investigated the X-ray properties of this unique source fitting multi-epoch data collected by Swift, XMM-Newton & Chandra with a disk model computing spectra for a wide range of sub- and super-Eddington accretion rates assuming a non-spinning black hole and a face-on disk (i = 0 deg). Under these assumptions we find that the black hole in HLX-1 is in the intermediate mass range (~2 x 10^4 solar masses) and the accretion flow is in the sub-Eddington regime. The disk radiation efficiency is eta = 0.11 0.03. We also show that the source does follow the L_X ~ T^4 relation for our mass estimate. At the outburst peaks, the source radiates near the Eddington limit. The accretion rate then stays constant around 4 x 10^(-4) solar masses yr^(-1) for several days and then decreases exponentially. Such "plateaus" in the accretion rate could be evidence that enhanced mass transfer rate is the driving outburst mechanism in HLX-1. We also report on the new outburst observed in August 2011 by the Swift-X-ray Telescope. The time of this new outburst further strengthens the ~1 year recurrence timescale.

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Posts: 130165
Date:
ESO 243-49 HLX-1
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Title: A minor merger scenario for the ultraluminous X-ray source ESO 243-49 HLX-1
Authors: M. Mapelli, L. Zampieri, L. Mayer

The point-like X-ray source HLX-1 is the brightest known ultraluminous X-ray source and likely the strongest intermediate-mass black hole candidate. HLX-1 is hosted in the S0 galaxy ESO 243-49, but offset with respect to the nucleus, and its optical counterpart was identified with a massive star cluster. In this paper, we study, through N-body/smoothed particle hydrodynamics simulations, the scenario where ESO 243-49 is undergoing (or just underwent) a minor merger with a gas-rich low-mass late-type galaxy. The simulations suggest that the observed star formation rate (SFR) in ESO 243-49 is a consequence of the interaction and that the companion galaxy already underwent the second pericentre passage. We propose that the counterpart of HLX-1 coincides with the nucleus (and possibly with the nuclear star cluster) of the secondary galaxy. We estimate that, if the minor merger scenario is correct, the number density of X-ray sources similar to HLX-1 is ~10^-6 Mpc^-3.

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Posts: 130165
Date:
RE: 2XMM J011028.1-460421
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NASA's Hubble Spots a Relic from a Shredded Galaxy

Astronomers using NASA's Hubble Space Telescope may have found evidence for a cluster of young, blue stars encircling HLX-1, one of the first intermediate-mass black holes ever discovered. Astronomers believe the black hole may once have been at the core of a now-disintegrated dwarf galaxy. The discovery of the black hole and the possible star cluster has important implications for understanding the evolution of supermassive black holes and galaxies.

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