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Article: Long-term X-ray variability study of IC342 from XMM-Newton observations

TitleLong-term X-ray variability study of IC342 from XMM-Newton observations
Authors
KeywordsGalaxies: individual (IC342)
Galaxies: starburst
X-rays: galaxies
Issue Date2011
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 2011, v. 728 n. 1 How to Cite?
AbstractWe presented the results of an analysis of four XMM-Newton observations of the starburst galaxy IC342 taken over a four-year span from 2001 to 2005, with an emphasis on investigating the long-term flux and spectral variability of the X-ray point sources. We detected a total of 61 X-ray sources within 35′ × 30′ of the galaxy down to a luminosity of (1-2) × 10 37 ergs-1 depending on the local background. We found that 39 of the 61 detected sources showed long-term variability, in which 26 of them were classified as X-ray transients. We also found 19 sources exhibiting variations in hardness ratios or undergoing spectral transitions among observations, and were identified as spectral variables. In particular, eight of the identified X-ray transients showed spectral variability in addition to flux variability. The diverse patterns of variability observed are indicative of a population of X-ray binaries. We used X-ray colors, flux and spectral variability, and in some cases the optical or radio counterparts to classify the detected X-ray sources into several stellar populations. We identified a total of 11 foreground stars, 1 supersoft source (SSS), 3 quasisoft sources (QSSs), and 2 supernova remnants (SNRs). The identified SSS/QSSs are located near or on the spiral arms, associated with young stellar populations; the 2 SNRs are very close to the starburst nucleus where current star formation activities are dominated. We also discovered a spectral change in the nuclear source of IC342 for the first time by a series of X-ray spectrum analysis. © 2011. The American Astronomical Society.
Persistent Identifierhttp://hdl.handle.net/10722/139638
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369
ISI Accession Number ID
Funding AgencyGrant Number
ESA Member States
NASA
HKU
government of the Hong Kong SAR
National Science Council, TaiwanNSC96-2112-M-007-037-MY3
Funding Information:

We thank Dr David Burrows and his collaborators for generously providing the source code to compute the Bayesian confidence intervals. We also thank the referee for very helpful comments and suggestions to improve the manuscript. This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. D.S.Y. Mak acknowledges support from HKU under the grant of Postgraduate Studentship. C.S.J. Pun acknowledges support of an RGC grant from the government of the Hong Kong SAR. A.K.H. Kong acknowledges support from the National Science Council, Taiwan, through a grant NSC96-2112-M-007-037-MY3.

References

 

DC FieldValueLanguage
dc.contributor.authorMak, DSYen_HK
dc.contributor.authorPun, CSJen_HK
dc.contributor.authorKong, AKHen_HK
dc.date.accessioned2011-09-23T05:52:49Z-
dc.date.available2011-09-23T05:52:49Z-
dc.date.issued2011en_HK
dc.identifier.citationAstrophysical Journal Letters, 2011, v. 728 n. 1en_HK
dc.identifier.issn2041-8205en_HK
dc.identifier.urihttp://hdl.handle.net/10722/139638-
dc.description.abstractWe presented the results of an analysis of four XMM-Newton observations of the starburst galaxy IC342 taken over a four-year span from 2001 to 2005, with an emphasis on investigating the long-term flux and spectral variability of the X-ray point sources. We detected a total of 61 X-ray sources within 35′ × 30′ of the galaxy down to a luminosity of (1-2) × 10 37 ergs-1 depending on the local background. We found that 39 of the 61 detected sources showed long-term variability, in which 26 of them were classified as X-ray transients. We also found 19 sources exhibiting variations in hardness ratios or undergoing spectral transitions among observations, and were identified as spectral variables. In particular, eight of the identified X-ray transients showed spectral variability in addition to flux variability. The diverse patterns of variability observed are indicative of a population of X-ray binaries. We used X-ray colors, flux and spectral variability, and in some cases the optical or radio counterparts to classify the detected X-ray sources into several stellar populations. We identified a total of 11 foreground stars, 1 supersoft source (SSS), 3 quasisoft sources (QSSs), and 2 supernova remnants (SNRs). The identified SSS/QSSs are located near or on the spiral arms, associated with young stellar populations; the 2 SNRs are very close to the starburst nucleus where current star formation activities are dominated. We also discovered a spectral change in the nuclear source of IC342 for the first time by a series of X-ray spectrum analysis. © 2011. The American Astronomical Society.en_HK
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_HK
dc.relation.ispartofAstrophysical Journal Lettersen_HK
dc.rightsThe Astrophysical Journal. Copyright © Institute of Physics Publishing, Inc.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectGalaxies: individual (IC342)en_HK
dc.subjectGalaxies: starbursten_HK
dc.subjectX-rays: galaxiesen_HK
dc.titleLong-term X-ray variability study of IC342 from XMM-Newton observationsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0004-637X&volume=728&issue=1, article no. 10&spage=&epage=&date=2011&atitle=Long-term+X-ray+variability+study+of+IC342+from+XMM-Newton+observations-
dc.identifier.emailPun, CSJ: jcspun@hkucc.hku.hken_HK
dc.identifier.authorityPun, CSJ=rp00772en_HK
dc.description.naturepostprint-
dc.identifier.doi10.1088/0004-637X/728/1/10en_HK
dc.identifier.scopuseid_2-s2.0-84891240116en_HK
dc.identifier.hkuros195550en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-79960279714&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume728en_HK
dc.identifier.issue1en_HK
dc.identifier.isiWOS:000286655500010-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridMak, DSY=23967776400en_HK
dc.identifier.scopusauthoridPun, CSJ=7003931846en_HK
dc.identifier.scopusauthoridKong, AKH=35185316600en_HK

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