Brown, P.J., Yang, Y., Cooke, J. et al. (9 more authors) (2016) ASASSN-15lh: a superluminous ultraviolet rebrightening observed by Swift and Hubble. The Astrophysical Journal, 828 (1). 3. ISSN 0004-637X
Abstract
We present and discuss ultraviolet and optical photometry from the Ultraviolet/Optical Telescope and X-ray limits from the X-Ray Telescope on Swift and imaging polarimetry and ultraviolet/optical spectroscopy with the Hubble Space Telescope of ASASSN-15lh. It has been classified as a hydrogenpoor superluminous supernova (SLSN I) more luminous than any other supernova observed. ASASSN- 15lh is not detected in the X-rays in individual or coadded observations. From the polarimetry we determine that the explosion was only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly into the ultraviolet, with a ultraviolet luminosity a hundred times greater than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find objects as bright as ASASSN-15lh are easily detectable beyond redshifts of ∼4 with the single-visit depths planned for the Large Synoptic Survey Telescope. Deep near-infrared surveys could detect such objects past a redshift of ∼20 enabling a probe of the earliest star formation. A late rebrightening – most prominent at shorter wavelengths – is seen about two months after the peak brightness, which is itself as bright as a superluminous supernova. The ultraviolet spectra during the rebrightening are dominated by the continuum without the broad absorption or emission lines seen in SLSNe or tidal disruption events and the early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen emission, showing only Lyα absorption near the redshift previously found by optical absorption lines of the presumed host. The properties of ASASSN-15lh are extreme when compared to either SLSNe or tidal disruption events.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016. The American Astronomical Society. All rights reserved. This is an author produced version of a paper subsequently published in The Astrophysical Journal. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 18 Nov 2016 13:10 |
Last Modified: | 07 Mar 2018 05:13 |
Published Version: | https://doi.org/10.3847/0004-637X/828/1/3 |
Status: | Published |
Publisher: | American Astronomical Society |
Refereed: | Yes |
Identification Number: | 10.3847/0004-637X/828/1/3 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:107687 |