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Roaring to softly whispering : X-Ray emission after ∼3.7 yr at the location of the transient AT2018cow and implications for accretion-powered scenarios
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Migliori, Giulia, Margutti, R., Metzger, B. D., Chornock, R., Vignali, C., Brethauer, D., Coppejans, Deanne, Maccarone, T., Rivera Sandoval, L., Bright, J. S., Laskar, T., Milisavljevic, D., Berger, E. and Nayana, A. J. (2024) Roaring to softly whispering : X-Ray emission after ∼3.7 yr at the location of the transient AT2018cow and implications for accretion-powered scenarios. The Astrophysical Journal Letters, 963 (1). L24. doi:10.3847/2041-8213/ad2764 ISSN 2041-8205.
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Official URL: http://doi.org/10.3847/2041-8213/ad2764
Abstract
We present the first deep X-ray observations of luminous fast blue optical transient (LFBOT) AT 2018cow at ∼3.7 yr since discovery, together with the reanalysis of the observation at δ t ∼ 220 days. X-ray emission is significantly detected at a location consistent with AT 2018cow. The very soft X-ray spectrum and sustained luminosity are distinct from the spectral and temporal behavior of the LFBOT in the first ∼100 days and would possibly signal the emergence of a new emission component, although a robust association with AT 2018cow can only be claimed at δ t ∼ 220 days, while at δ t ∼ 1350 days contamination of the host galaxy cannot be excluded. We interpret these findings in the context of the late-time panchromatic emission from AT 2018cow, which includes the detection of persistent, slowly fading UV emission with ν L ν ≈ 1039 erg s−1. Similar to previous works (and in analogy with arguments for ultraluminous X-ray sources), these late-time observations are consistent with thin disks around intermediate-mass black holes (with M • ≈ 103–104 M ☉) accreting at sub-Eddington rates. However, differently from previous studies, we find that smaller-mass black holes with M • ≈ 10–100 M ☉ accreting at ≳the Eddington rate cannot be ruled out and provide a natural explanation for the inferred compact size (R out ≈ 40 R ☉) of the accretion disk years after the optical flare. Most importantly, irrespective of the accretor mass, our study lends support to the hypothesis that LFBOTs are accretion-powered phenomena and that, specifically, LFBOTs constitute electromagnetic manifestations of super-Eddington accreting systems that evolve to ≲Eddington over a ≈100-day timescale.
Item Type: | Journal Article | |||||||||||||||||||||
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Subjects: | Q Science > QB Astronomy | |||||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | |||||||||||||||||||||
SWORD Depositor: | Library Publications Router | |||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Black holes (Astronomy), X-ray astronomy, Transients (Dynamics) , Supernovae , Accretion (Astrophysics), Protoplanetary disks | |||||||||||||||||||||
Journal or Publication Title: | The Astrophysical Journal Letters | |||||||||||||||||||||
Publisher: | Institute of Physics Publishing, Inc. | |||||||||||||||||||||
ISSN: | 2041-8205 | |||||||||||||||||||||
Official Date: | March 2024 | |||||||||||||||||||||
Dates: |
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Volume: | 963 | |||||||||||||||||||||
Number: | 1 | |||||||||||||||||||||
Article Number: | L24 | |||||||||||||||||||||
DOI: | 10.3847/2041-8213/ad2764 | |||||||||||||||||||||
Status: | Peer Reviewed | |||||||||||||||||||||
Publication Status: | Published | |||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | |||||||||||||||||||||
Description: | Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. |
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Date of first compliant deposit: | 21 March 2024 | |||||||||||||||||||||
Date of first compliant Open Access: | 22 March 2024 | |||||||||||||||||||||
RIOXX Funder/Project Grant: |
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