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X-ray outbursts of ESO 243-49 HLX-1: comparison with galactic low-mass x-ray binary transients

X-ray outbursts of ESO 243-49 HLX-1: comparison with galactic low-mass x-ray binary transients
X-ray outbursts of ESO 243-49 HLX-1: comparison with galactic low-mass x-ray binary transients
We studied the outburst properties of the hyper-luminous X-ray source ESO 243-49 HLX-1, using the full set of Swift monitoring observations. We quantified the increase in the waiting time, recurrence time, and e-folding rise timescale along the outburst sequence, and the corresponding decrease in outburst duration, total radiated energy, and e-folding decay timescale, which confirms previous findings. HLX-1 spends less and less time in outburst and more and more time in quiescence, but its peak luminosity remains approximately constant. We compared the HLX-1 outburst properties with those of bright Galactic low-mass X-ray binary transients (LMXBTs). Our spectral analysis strengthens the similarity between state transitions in HLX-1 and those in Galactic LMXBTs. We also found that HLX-1 follows the nearly linear correlations between the hard-to-soft state transition luminosity and the peak luminosity, and between the rate of change of X-ray luminosity during the rise phase and the peak luminosity, which indicates that the occurrence of the hard-to-soft state transition of HLX-1 is similar to those of Galactic LMXBTs during outbursts. We found that HLX-1 does not follow the correlations between total radiated energy and peak luminosity, and between total radiated energy and e-folding rise/decay timescales we had previously identified in Galactic LMXBTs. HLX-1 would follow those correlations if the distance were several hundreds of kiloparsecs. However, invoking a much closer distance for HLX-1 is not a viable solution to this problem, as it introduces other, more serious inconsistencies with the observations.
1538-4357
1-11
Zhen, Yan
f9d1e585-3c1c-4cdb-b1b6-86aa915aebf5
Zhang, Wenda
69a28cc7-9841-49a5-b481-4f4b3afc9e82
Soria, Roberto
5c123193-2dcd-49b7-a20d-4ddbf878a886
Altamirano, Diego
d5ccdb09-0b71-4303-9538-05b467be075b
Yu, Wenfei
7db79bcb-a03f-463c-8609-9476f9bc177a
Zhen, Yan
f9d1e585-3c1c-4cdb-b1b6-86aa915aebf5
Zhang, Wenda
69a28cc7-9841-49a5-b481-4f4b3afc9e82
Soria, Roberto
5c123193-2dcd-49b7-a20d-4ddbf878a886
Altamirano, Diego
d5ccdb09-0b71-4303-9538-05b467be075b
Yu, Wenfei
7db79bcb-a03f-463c-8609-9476f9bc177a

Zhen, Yan, Zhang, Wenda, Soria, Roberto, Altamirano, Diego and Yu, Wenfei (2015) X-ray outbursts of ESO 243-49 HLX-1: comparison with galactic low-mass x-ray binary transients. The Astrophysical Journal, 811 (1), 1-11. (doi:10.1088/0004-637x/811/1/23).

Record type: Article

Abstract

We studied the outburst properties of the hyper-luminous X-ray source ESO 243-49 HLX-1, using the full set of Swift monitoring observations. We quantified the increase in the waiting time, recurrence time, and e-folding rise timescale along the outburst sequence, and the corresponding decrease in outburst duration, total radiated energy, and e-folding decay timescale, which confirms previous findings. HLX-1 spends less and less time in outburst and more and more time in quiescence, but its peak luminosity remains approximately constant. We compared the HLX-1 outburst properties with those of bright Galactic low-mass X-ray binary transients (LMXBTs). Our spectral analysis strengthens the similarity between state transitions in HLX-1 and those in Galactic LMXBTs. We also found that HLX-1 follows the nearly linear correlations between the hard-to-soft state transition luminosity and the peak luminosity, and between the rate of change of X-ray luminosity during the rise phase and the peak luminosity, which indicates that the occurrence of the hard-to-soft state transition of HLX-1 is similar to those of Galactic LMXBTs during outbursts. We found that HLX-1 does not follow the correlations between total radiated energy and peak luminosity, and between total radiated energy and e-folding rise/decay timescales we had previously identified in Galactic LMXBTs. HLX-1 would follow those correlations if the distance were several hundreds of kiloparsecs. However, invoking a much closer distance for HLX-1 is not a viable solution to this problem, as it introduces other, more serious inconsistencies with the observations.

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__soton.ac.uk_UDE_PersonalFiles_Users_skr1c15_mydocuments_eprints_Altamirano_X-RAY OUTBURSTS OF ESO 243-49 HLX-1 COMPARISON WITH GALACTIC LOW-MASS X-RAY BINARY TRANSIENTS.pdf - Accepted Manuscript
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Accepted/In Press date: 12 August 2015
Published date: 16 September 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 396169
URI: http://eprints.soton.ac.uk/id/eprint/396169
ISSN: 1538-4357
PURE UUID: ab3c8e05-993d-4b20-b230-4184dfa1b86d
ORCID for Diego Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 02 Jun 2016 15:42
Last modified: 21 Nov 2021 03:10

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Contributors

Author: Yan Zhen
Author: Wenda Zhang
Author: Roberto Soria
Author: Wenfei Yu

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