English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present and discuss ultraviolet and optical photometry from theUltraviolet/Optical Telescope and X-ray limits from the X-Ray Telescope onSwift and imaging polarimetry and ultraviolet/optical spectroscopy with theHubble Space Telescope of ASASSN-15lh. It has been classified as ahydrogen-poor superluminous supernova (SLSN I) more luminous than any othersupernova observed. ASASSN-15lh is not detected in the X-rays in individual orcoadded observations. From the polarimetry we determine that the explosion wasonly mildly asymmetric. We find the flux of ASASSN-15lh to increase stronglyinto the ultraviolet, with a ultraviolet luminosity a hundred times greaterthan the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find objectsas bright as ASASSN-15lh are easily detectable beyond redshifts of ~4 with thesingle-visit depths planned for the Large Synoptic Survey Telescope. Deepnear-infrared surveys could detect such objects past a redshift of ~20 enablinga probe of the earliest star formation. A late rebrightening -- most prominentat shorter wavelengths -- is seen about two months after the peak brightness,which is itself as bright as a superluminous supernova. The ultraviolet spectraduring the rebrightening are dominated by the continuum without the broadabsorption or emission lines seen in SLSNe or tidal disruption events and theearly optical spectra of ASASSN-15lh. Our spectra show no strong hydrogenemission, showing only LyA absorption near the redshift previously found byoptical absorption lines of the presumed host. The properties of ASASSN-15lhare extreme when compared to either SLSNe or tidal disruption events.

ASASSN-15lh: A Superluminous Ultraviolet Rebrightening Observed by Swift and Hubble