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ASASSN-17be: Discovery of A Type Ia Supernova in 2MASX J02031063-6141105

ATel #10004; M. R. Drout (Hubble Fellow, Carnegie Observatories), T. W.-S. Holoien (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields, T. A. Thompson (Ohio State), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), J. Brimacombe (Coral Towers Observatory)
on 25 Jan 2017; 19:48 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 or "Assassin"), using data from the quadruple 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a new Type Ia supernova in the galaxy 2MASX J02031063-6141105.

ASASSN-17be (AT 2017pa) was discovered in images obtained on UT 2017-01-17.07 at V~17.5 mag. We also detect the object in images obtained on UT 2017-01-22.04 (V~17.4) and UT 2017-01-20.07 (V~17.6). We do not detect (V>17.1) the object in images taken on UT 2017-01-15.15 and before. An image obtained on UT 2017-01-25 using the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the du Pont confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the du Pont image.

The position of ASASSN-17be is approximately 0.1" South and 0.5" West from the center of the galaxy 2MASX J02031063-6141105, which has no redshift available in NED.

An optical spectrum (range 390-910 nm) of ASASSN-17be was obtained on UT 2017-01-25 using the du Pont 2.5-m telescope (+ WFCCD) at Las Campanas Observatory. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that ASASSN-17be is most consistent with a normal Type Ia supernova roughly 1 week after maximum brightness at z=0.04. This gives an absolute V-band magnitude of approximately -18.8 (m-M=36.25, A_V=0.096) at discovery.

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-17be  02:03:10.53   -61:41:10.63     2017-01-17.07      17.5          -18.8               0.51 
Obs. UT Date         V mag 
2017-01-15.15        >17.1 
2017-01-17.07         17.5 
2017-01-20.07         17.6 
2017-01-22.04         17.4 

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.