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A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247

Feng, Hua and Ho, Luis C. and Kaaret, Philip and Tao, Lian and Yamaoka, Kazutaka and Zhang, Shuo and Grisé, Fabien (2015) A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247. Astrophysical Journal, 807 (2). Art. No. 185. ISSN 0004-637X.

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NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity of up to 2 x 10^(39) erg s^(−1) in the 0.3–10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3–4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by a factor of almost 20. The spectral and temporal behaviors of the nuclear source are consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to accretion onto a possible low-mass nuclear black hole, fed by a tidally disrupted star or a gas cloud; the Monitor of All-sky X-ray Image observations limit the peak luminosity of the flare to less than ~10^(43) erg s^(-1), suggesting that it is either a low-mass black hole or an inefficient tidal disruption event.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Feng, Hua0000-0001-7584-6236
Ho, Luis C.0000-0001-6947-5846
Kaaret, Philip0000-0002-3638-0637
Zhang, Shuo0000-0002-2967-790X
Additional Information:© 2015 American Astronomical Society. Received 2015 March 15; accepted 2015 June 1; published 2015 July 10. We thank the anonymous referee for helpful comments that improved the paper, the Chandra director for granting discretionary time and the Swift PI for approving the ToO program, and the XMM-Newton/Chandra/Swift teams for successful executions of the observations. H.F. acknowledges funding support from the National Natural Science Foundation of China under grant No.11222327 and the Tsinghua University Initiative Scientific Research Program. L.C.H. acknowledges support by the Chinese Academy of Science through grant No. XDB09030102 (Emergence of Cosmological Structures) from the Strategic Priority Research Program and by the National Natural Science Foundation of China through grant No.11473002. Facilities: XMM, CXO, Swift
Funding AgencyGrant Number
National Natural Science Foundation of China11222327
Tsinghua University Initiative Scientific Research ProgramUNSPECIFIED
Chinese Academy of ScienceXDB09030102
National Natural Science Foundation of China11473002
Subject Keywords: galaxies: nuclei; X-rays: galaxies; black hole physics
Issue or Number:2
Record Number:CaltechAUTHORS:20150831-121211457
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Official Citation:A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247 Hua Feng et al. 2015 ApJ 807 185
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59992
Deposited By: Ruth Sustaita
Deposited On:31 Aug 2015 21:06
Last Modified:09 Mar 2020 13:19

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