ASAS-SN Discovery of A Probable Supernova in Dwarf Galaxy GALEXASC J025358.03-213854.7

ATel #6836; J. Brimacombe (Coral Towers Observatory), S. Kiyota (Variable Star Observers League in Japan), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, A. B. Davis, G. Simonian, U. Basu, N. Goss, J. F. Beacom (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), E. Conseil (Association Francaise des Observateurs d'Etoiles Variables), B. Nicholls (Mt. Vernon Obs., New Zealand), J. Nicolas (Groupe SNAUDE, France)
on 18 Dec 2014; 17:23 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

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During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the double 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy GALEXASC J025358.03-213854.7:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-14mg  02:53:58.10   -21:38:52.86      2014-12-18.11    16.6 

ASASSN-14mg was discovered in images obtained on UT 2014-12-18.11 at V~16.6 mag. We also detect the object in images obtained on UT 2014-12-15.33 (V~16.8), UT 2014-12-13.33 (V~16.5), UT 2014-12-11.33 (V~16.7), and UT 2014-12-08.07 (V~16.4) and we marginally detect the object in images obtained on UT 2014-12-10.35, UT 2014-12-02.36, and UT 2014-11-29.33. We do not detect (V>17.1) the object in images taken on UT 2014-11-27.36 and before. Images obtained by J. Brimacombe on UT 2014-12-18.24 with the RCOS 51-cm telescope in New Mexico and by S. Kiyota on UT 2014-12-18.28 using a Planewave CDK 0.43-m telescope located near Mayhill, New Mexico confirm the discovery of the transient. This figure shows the archival DSS image of the host (left) and the J. Brimacombe confirmation image (right). The red arrow indicates the position of the transient in the J. Brimacombe image.

The position of ASASSN-14mg is approximately 2.3" North and 0.4" East from the center of the galaxy GALEXASC J025358.03-213854.7, an apparent dwarf galaxy with no redshift available in NED. Follow-up observations, particularly spectroscopy, are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.