Gaia discovery and LCOGT and LT follow-up of Gaia15aao - a supernova in CGCG 078-056

ATel #7014; L. Wyrzykowski (Warsaw Observatory/IoA Cambridge), P. Whitelock, V. McBride (SAAO/University of Cape Town), M. Dominik, A. Scholz (University of St Andrews),H. Campbell, M. Fraser, S. T. Hodgkin (IoA Cambridge), Z. Kostrzewa-Rutkowska (Warsaw Observatory), N. Blagorodnova, G. Rixon, S. Koposov, N. Walton (IoA Cambridge) on behalf of larger team.
on 31 Jan 2015; 12:26 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@ast.cam.ac.uk)

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We report on the detection and photometric confirmation of a new supernova candidate discovered by the Gaia satellite during the Gaia Photometric Science Alerts validation phase (http://gaia.ac.uk/selected-gaia-science-alerts).

Name Ra (J2000.0) Dec (J2000.0) Discovery (UT) Discovery G[mag]

Gaia15aao 15:44:12.40 11:16:16.29 2015-01-12T03:34:18 17.72mag

was detected by Gaia as a new blue source within CGCG 078-056 galaxy (NED) on 2015-01-12T03:34:18 and 2015-01-12T05:20:52 at G=17.72 mag (Gaia clear band). Last Gaia observation with a non-detection: 2014-12-24T21:27:19.

The presence of the transient was confirmed using LCOGT 1-m robotic telescopes at Cerro Tololo, Chile, on 2015-01-29T09:02:19 and Liverpool Telescope, La Palma, on 2015-01-29T05:36:02. This figure: http://www.astrouw.edu.pl/~wyrzykow/GAIA/FOLLOWUP/Gaia15aao-follow-up.png
shows archival SDSS image of the CGCG 078-056 host galaxy, LCOGT 60s and LT 120 s exposures in gri filters combined into a colour composition with the transient clearly present. The g-band calibrated magnitude of the transient on the follow-up images was 16.9 mag.

Supernova candidate Gaia15aao is located about 6’’ from the centre of the starburst galaxy CGCG 078-056 http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id=1237668349755719744”> with redshift z= 0.034277, giving approximate absolute magnitude of -19. The transient also can be related with the star forming region visible as a blue dot on SDSS archival image about 1’’ to the east-north. Spectroscopic follow-up from Asiago (ATEL #7012) classified this transient as a supernova type Ia at about 2 weeks past maximum.

Further follow-up observations are strongly encouraged.

We acknowledge ESA Gaia (http://cosmos.esa.int/gaia), DPAC (cosmos.esa.int/web/gaia/dpac) and the DPAC Photometric Science Alerts Team (http://gaia.ac.uk/selected-gaia-science-alerts). The LCOGT observations were carried under proposal SAO2014B-001 which is part of the University of St Andrews and South African Astronomical Observatory allocation. The photometric calibrations were obtained using the Cambridge Photometric Calibration Server (CPCS), designed and maintained by Sergey Koposov and Lukasz Wyrzykowski. More info on CPCS: http://www.ast.cam.ac.uk/ioa/wikis/gsawgwiki/index.php/Follow-up

Archival, LCOGT and LT colour composite images