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ASASSN-17ek: Discovery of A Probable Supernova in LCRS B035620.1-420206

ATel #10239; T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 3 Apr 2017; 16:31 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new transient source, most likely a supernova, in the galaxy LCRS B035620.1-420206.

ASASSN-17ek (AT 2017cqe) was discovered in images obtained on UT 2017-04-01.00 at V~17.2 mag. We also detect the transient in images obtained on UT 2017-03-27.02 (V~18.0). We do not detect (V>18.1) the object in images taken on UT 2017-03-24.02 and before. An image obtained on UT 2017-04-02 using the Las Cumbres Observatory 1-m telescope in Sutherland, South Africa, confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the LCO g-band confirmation image (right). The red circle has a radius of 2" and is centered on the position of the transient in the LCO image.

The position of ASASSN-17ek is approximately 2.1" South and 1.9" East from the center of the galaxy LCRS B035620.1-420206 (z=0.058971, d=253 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.8 (m-M=37.01, A_V=0.019). 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-17ek  03:58:02.45   -41:53:35.89     2017-04-01.00      17.2          -19.8               2.83 
Obs. UT Date         V mag 
2017-03-24.02        >18.1 
2017-03-27.02         18.0 
2017-04-01.00         17.2 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-17xx transient names as our primary nomenclature (including supernovae, but also other classes of transients), and we encourage others to do the same. We prefer merging the names as ASASSN-17xx (AT 2017xyz) to preserve, rather than anonymize, the origin of the transient.

We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the 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.