Earnshaw, H. M. (2016) An intermediate-mass black hole candidate in M51? Astronomische Nachrichten, 337 (4-5). pp. 448-453. ISSN 0004-6337. doi:10.1002/asna.201612328. https://resolver.caltech.edu/CaltechAUTHORS:20160527-110052419
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Abstract
We present the current results of an investigation into M51 ULX-7, using archival data from XMM-Newton, Chandra and NuSTAR, and optical and radio data from HST and VLA. The source has a consistently hard power-law X-ray spectrum and high short-term variability. This is unusual variability behaviour for a ULX, as we would expect highly variable ULXs to have soft energy spectra. The power spectrum features a break at ∼ 10^(–3) Hz, from low frequency spectral index α = 0.1 to high frequency spectral index α = 0.8, analogous to the low frequency break found in power spectra of black holes accreting in the low/hard state. We do not observe a corresponding high frequency break, however taking the white noise level as a frequency lower limit of the break, we can calculate a black hole mass upper limit of 9.12×104 M, assuming that the ULX is in the low/hard state. While there is no radio detection, we find a flux density upper limit of 87 µJy/beam. Using the X-ray/radio fundamental plane, we calculate a black hole mass upper limit of 1.95×10^5 M®. Therefore, this ULX is consistent with being an IMBH accreting in the low/hard state.
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Additional Information: | © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We gratefully acknowledge support from the Science and Technology Facilities Council (HE through grant ST/K501979/1). | ||||||||||||
Group: | NuSTAR | ||||||||||||
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Issue or Number: | 4-5 | ||||||||||||
DOI: | 10.1002/asna.201612328 | ||||||||||||
Record Number: | CaltechAUTHORS:20160527-110052419 | ||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20160527-110052419 | ||||||||||||
Official Citation: | Earnshaw, H. M. (2016), An intermediate-mass black hole candidate in M51?. Astron. Nachr., 337: 448–453. doi: 10.1002/asna.201612328 | ||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||
ID Code: | 67448 | ||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||
Deposited By: | Joy Painter | ||||||||||||
Deposited On: | 27 May 2016 19:11 | ||||||||||||
Last Modified: | 04 Oct 2022 18:19 |
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