ASAS-SN Discovery of A Probable Nearby Supernova in 2MASX J15333488-7807258
ATel #7444; B. J. Shappee (Hubble Fellow, Carnegie Observatories), Subo Dong (KIAA-PKU), K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom, T. A. Thompson (Ohio State), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), P. R. Wozniak (LANL), E. Falco (CfA), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 25 Apr 2015; 06:10 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Benjamin Shappee (firstname.lastname@example.org)
Subjects: Optical, Supernovae, Transient
Referred to by ATel #: 7458
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 2MASX J15333488-7807258.
ASASSN-15hs was discovered in images obtained on UT 2015-04-24.18 at V~16.6 mag. We also detect the object in images obtained on UT 2015-04-17.26 (V~17.1), 2015-04-19.22 (V~16.9), 2015-04-23.15 (V~16.8), and 2015-04-23.17 (V~16.9). We do not detect (V>16.9) the object in images taken on UT 2015-04-17.18 and before. A g-band image obtained on UT 2015-04-25.10 with the LCOGT 1-m robotic telescope in Sutherland, South Africa confirms the discovery of the transient. This figure shows the ASAS-SN reference image (bottom-left), archival DSS image of the host (bottom-right), ASAS-SN discovery difference image (top-left), and the LCOGT confirmation image (top-right). The red circle has a radius of 2" and is centered on the position of the transient in the LCOGT image.
The position of ASASSN-15hs is approximately 1.7" North and 2.2" East from the center of the galaxy 2MASX J15333488-7807258 (z=0.0.009096, d=35.1 Mpc, via NED), giving an absolute V-band magnitude of approximately -16.6 (m-M=32.94, A_V=0.297). Properties of the new source and photometry are summarized in the tables below:
Object RA (J2000) DEC (J2000) Disc. UT Date Disc. V mag Approx. Abs. Mag Offset from Host
ASASSN-15hs 15:33:34.31 -78:07:23.46 2015-04-24.18 16.6 -16.4 2.7"
Observation Date V mag
2015-04-17.26 17.1 0.2
2015-04-19.22 16.9 0.1
2015-04-23.15 16.8 0.2
2015-04-23.17 16.9 0.1
2015-04-24.18 16.6 0.1
Follow-up observations are encouraged.
We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported in part by Mt. Cuba Astronomical Foundation. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.