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An intermediate-mass black hole candidate in M51?

Earnshaw, H. M. (2016) An intermediate-mass black hole candidate in M51? Astronomische Nachrichten, 337 (4-5). pp. 448-453. ISSN 00046337. http://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.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/asna.201612328DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/asna.201612328/abstractPublisherArticle
https://arxiv.org/abs/1510.02277arXivDiscussion Paper
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
Funders:
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC) ST/K501979/1
Record Number:CaltechAUTHORS:20160527-110052419
Persistent URL:http://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:06 Nov 2018 19:05

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