1036 transients classified by PESSTO so far
221 transients are being followed by PESSTO

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PESSTO’s view on the superluminous event ASASSN-15lh


Spectral sequence of ASASSN-15lh over 260 days. From Leloudas et al. 2016, Nature Astronomy : PUBLISHED: 12 DECEMBER 2016 | VOLUME: 1 | ARTICLE NUMBER: 0002

Giorgos Leloudas led the PESSTO campaign to understand the nature of the extraordinary ASASSN-15lh with a paper in Nature Astronomy’s first edition. The paper was subject to an early release and a major press release my ESO.

This object was discovered last year by ASASSN and was originally thought to be the most luminous supernova ever discovered. The PESSTO campaign, combined with LCO photometry, data from VLT and the ANU 2.3m, Swift and HST monitored the transient for 10 months. Giorgos’ paper proposes that is more likely to be a a tidal disruption event. This was originally thought unlikely since the mass of the black hole in this host galaxy is likely to be larger than 108 solar masses, which would mean that stellar disruptions would occur within the event horizon and hence not radiate light. However our team suggest that a tidal disruption event could occur in this case if the black hole is rapidly spinning (a Kerr black hole) and that this is the most likely explanation.

PESSTO the world’s leading classification engine

PESSTO’s science goals have been to study the extremes of the explosive populations being found in large numbers by the most efficient surveys that have ever run. An important part of running the survey is taking a spectrum as quickly as possible after a transient is found and also to release the data, classification, redshift and any important or unusual characteristics. We do this on a daily basis, and nearly always within 12hrs of the end of the Chilean night.

As of January 1, 2016 the Transient Name Server (TNS) has been the official IAU mechanism for reporting new astronomical transients such as supernova candidates. Hosted at the Weizmann Institute of Science, this is a continuation of the IAU naming scheme for supernovae which was handled by the Central Bureau for Astronomical Telegrams until the end of 2015, and has been approved as the official IAU naming scheme by the IAU Executive Committee from 1st January 2016.

The IAU TNS keeps track of all the supernova candidates posted publicly and all spectroscopic classifications. The statistics are available on this page, showing that in the first 9 months of 2016 PESSTO is the leading engine to classify supernovae and report the results promptly to the community. Our results always have a reduced spectrum publicly available on the same rapid timescale, released through WISeREP

a few of the most recent PESSTO papers ...

Early observations of the nearby Type Ia supernova SN 2015F  Cartier, R.; Sullivan, M.; Firth, R. E. et al.
ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc  Holoien, T. W.-S.; Kochanek, C. S.; Prieto, J. L. et al.
An optical and near-infrared study of the Type Ia/IIn Supernova PS15si  Kilpatrick, Charles D.; Andrews, Jennifer E.; Smith, Nathan et al.