ASASSN-16nm and ASASSN-16nn: Discovery of Two Probable Supernovae in 2MASX J21255058-3724071 and APMUKS(BJ) B214820.71-555825.5

ATel #9785; 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), D. Bersier (LJMU), Subo Dong, S. Bose, Ping Chen (KIAA-PKU), S. Kiyota (Variable Star Observers League in Japan), P. Marples (Leyburn Observatory, Australia), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 23 Nov 2016; 17:49 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 quadruple 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered two new transient sources, most likely supernovae, in the galaxies 2MASX J21255058-3724071 and APMUKS(BJ) B214820.71-555825.5.

ASASSN-16nm (AT 2016ijc) was discovered in images obtained on UT 2016-11-23.09 at V~16.7 mag. We also detect the object in images obtained on UT 2016-11-18.09 (V~17.3). We do not detect (V>16.8) the object in images taken on UT 2016-11-17.13 and before. An image obtained on UT 2016-11-23 by J. Brimacombe confirms 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 circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-16nm is approximately 7.0" South and 18.5" East from the center of the galaxy 2MASX J21255058-3724071 (z=0.030685, d=126 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.0 (m-M=35.50, A_V=0.216).

ASASSN-16nn (AT 2016ijf) was discovered in images obtained on UT 2016-11-23.14 at V~16.8 mag. We also detect the object in images obtained on UT 2016-11-20.14 (V~17.2). We do not detect (V>16.9) the object in images taken on UT 2016-11-18.15 and before. An image obtained on UT 2016-11-23 by J. Brimacombe confirms 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 circle has a radius of 5" and is centered on the position of the transient in the J. Brimacombe image.

The position of ASASSN-16nn is approximately 0.7" North and 3.4" West from the center of the galaxy APMUKS(BJ) B214820.71-555825.5, which has no redshift available in NED.

Properties of the new sources 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-16nm  21:25:52.16   -37:24:14.32     2016-11-23.09      16.7          -19.0               19.78 
ASASSN-16nn  21:51:47.00   -55:44:19.06     2016-11-23.14      16.8          N/A                 3.47 

ASASSN-16nm:

 
Obs. UT Date         V mag 
2016-11-17.13        >16.8 
2016-11-18.09         17.3 
2016-11-23.09         16.7 

ASASSN-16nn:

 
Obs. UT Date         V mag 
2016-11-18.15        >16.9 
2016-11-20.14         17.2 
2016-11-23.14         16.8 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential 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, rather than anonymize, 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 the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.