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ASASSN-16pa and ASASSN-16pb: Discovery of Two Probable Supernovae

ATel #9893; J. Brimacombe (Coral Towers Observatory), J. S. Brown (Ohio State), S. Bose (KIAA-PKU), K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, T. A. Thompson, J. Shields (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU), S. Kiyota (Variable Star Observers League in Japan), P. Marples (Leyburn Observatory, Australia), G. Masi (Virtual Telescope Project, Ceccano, Italy), R. S. Post (Post Astronomy), G. Stone (Sierra Remote Observatories)
on 22 Dec 2016; 20:41 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 9900

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" and "Cassius" telescopes in Haleakala, Hawaii and Cerro Tololo, Chile, we discovered two new transient sources, most likely supernovae in an uncatalogued host galaxy and the galaxy CGCG 058-057.

ASASSN-16pa (AT 2016izf) was discovered in images obtained on UT 2016-12-22.09 at V~17.1 mag. We also detect the object in images obtained on UT 2016-12-19.19 (V~17.2). We do not detect (V>17.7) the object in images taken on UT 2016-12-18.11 and before. An image obtained on 2016-12-22 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-16pa is approximately 7.6" South and 6.0" West from a nearby uncatalogued galaxy.

ASASSN-16pb (AT 2016izg) was discovered in images obtained on UT 2016-12-22.59 at V~16.4 mag. We do not detect (V>17.0) the object in images taken on UT 2016-12-13.42 and before. An image obtained on 2016-12-22 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival SDSS g-band 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-16pb is approximately 2.5" North and 7.1" West from the center of the galaxy CGCG 058-057 (z=0.029781, d=128 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.2 (m-M=35.48, A_V=0.080). 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-16pa  00:33:14.108   -84:29:20.09     2016-12-21.15      17.0            N/A                9.7 
ASASSN-16pb  07:53:12.802   +12:53:55.95     2016-12-22.59      16.4          -19.2               7.53 

ASASSN-16pa photometry:

 
Obs. UT Date         V mag 
2016-12-18.11        >17.7 
2016-12-19.19         17.2 
2016-12-22.09         17.1 

ASASSN-16pb photometry:

 
Obs. UT Date         V mag 
2016-12-13.42        >17.0 
2016-12-22.59         16.4 

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 Las Cumbres Observatory 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, 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.