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ASASSN-16mj and ASASSN-16ml: Discovery of A Type Ia Supernova in SDSS J092119.07+170159.5 and a Probable Supernova in GALEXASC J215436.98-425103.9

ATel #9697; D. Bersier (LJMU), J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, J. Shields (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), G. Bock (Runaway Bay Observatory, Australia), R. A. Koff (Antelope Hills Observatory), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories)
on 1 Nov 2016; 18:09 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 9701

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN) we discovered two new transient sources, a Type Ia supernova and a likely supernova, in the galaxies SDSS J092119.07+170159.5 and GALEXASC J215436.98-425103.9.

ASASSN-16mj (SN 2016hpe) was discovered in images obtained on UT 2016-10-28.62 at V~16.4 mag. We do not detect (V>16.9) the object in images taken on UT 2016-10-17.61 and before. An image obtained on UT 2016-11-01 with the Liverpool Telescope confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the LT confirmation image (right). The red circle has a radius of 4" and is centered on the position of the transient in the LT image.

The position of ASASSN-16mj is approximately 1.2" South and 0.7" West from the center of the galaxy SDSS J092119.07+170159.5, which has no available redshift in NED.

A low resolution optical spectrum of ASASSN-16mj was obtained with the SPRAT spectrograph on the LT located at the Roque de los Muchachos observatory (La Palma) on UT 2016-11-01. The spectral range is 400-800 nm and the dispersion is 9.2 Angstrom/pixel. Comparison of the spectrum with a library of spectra (SNID - Blondin and Tonry 2007, ApJ, 666, 1024) shows that this object is a type Ia SN near maximum light at a redshift of 0.028. It is most likely of the 91T subclass, and shows a best fit with SN 2007S at 0.7d before maximum light. At this redshift, the SN has an absolute V-band magnitude of approximately -19.1 (m-M=35.45, A_V=0.08).

ASASSN-16ml (AT 2016hpt) was discovered in images obtained on UT 2016-10-30.08 at V~17.0 mag. We also detect the object in images obtained on UT 2016-10-25.19 (V~17.4). We do not detect (V>17.6) the object in images taken on UT 2016-10-22.20 and before. An image obtained on 2016-10-30 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the JB confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the JB image.

The position of ASASSN-16ml is approximately 1.3" North and 4.3" West from the center of the galaxy GALEXASC J215436.98-425103.9, which also has no redshift available in NED.

Properties and photometry of the new sources are summarized in the tables below:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-16mj  09:21:19.03   +17:01:58.35     2016-10-28.62      16.4          -19.1               1.39 
ASASSN-16ml  21:54:36.59   -42:51:02.93     2016-10-30.08      17.0           N/A                4.49 
ASASSN-16mj:
 
Obs. UT Date         V mag 
2016-10-17.61        >16.9 
2016-10-28.62         16.4 
ASASSN-16ml:
 
Obs. UT Date         V mag 
2016-10-22.20        >17.6 
2016-10-25.19         17.4 
2016-10-30.08         17.0 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize confusion, ASAS-SN will continue using ASASSN-16xx 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-16xx (AT2016xyz) to preserve the origin of the transient.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported by NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Mt. Cuba Astronomical Foundation. For more information about ASAS-SN, see the ASAS-SN Homepage and the list of all ASAS-SN transients.