ASASSN-17cu and ASASSN-17cv: Discovery of Two Probable Supernovae

ATel #10113; S. Kiyota (Variable Star Observers League in Japan), J. Brimacombe (Coral Towers Observatory), R. A. Koff (Antelope Hills Observatory), R. S. Post (Post Astronomy), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, 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. M. Fernandez (Observatory Inmaculada del Molino)
on 22 Feb 2017; 23:38 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

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During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered two new transient sources, most likely supernovae, in the galaxies MCG +08-20-019 and 2MASX J16110570+0234002.

ASASSN-17cu (AT 2017bgp) was discovered in images obtained on UT 2017-02-21.53 at V~17.8 mag. We also detect the object in images obtained on UT 2017-02-17.45 (V~17.7). We do not detect (V>17.4) the object in images taken on UT 2017-02-15.51 and before. An image obtained on 2017-02-22 by S. Kiyota confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the S. Kiyota confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-17cu is approximately 0.4" North and 0.6" East from the center of the galaxy MCG +08-20-019 (z=0.047198, d=204 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.7 (m-M=36.45, A_V=0.053).

ASASSN-17cv (AT 2017bgt) was discovered in images obtained on UT 2017-02-21.64 at V~17.2 mag. We also detect the object in images obtained on UT 2017-02-22.66 (V~17.4). We do not detect (V>17.5) the object in images taken on UT 2017-02-13.58 and before. An image obtained on 2017-02-22 by J. Brimacombe confirms the discovery of the transient. This figure shows the archival Pan-STARRS (Chambers et al. 2016, arXiv:1612.05560) 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-17cv is approximately 0.1" South and 0.2" East from the center of the galaxy 2MASX J16110570+0234002 (no redshift information available from 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-17cu  10:46:07.315   +44:43:29.26     2017-02-21.53      17.8          -18.7               0.72 
ASASSN-17cv  16:11:05.702   +02:34:00.20     2017-02-21.64      17.2          N/A                 0.22 

ASASSN-17cu photometry:

 
Obs. UT Date         V mag 
2017-02-15.51        >17.5 
2017-02-17.45         17.7 
2017-02-21.53         17.8 

ASASSN-17cv photometry:

 
Obs. UT Date         V mag 
2017-02-13.58        >17.5 
2017-02-21.64         17.2 
2017-02-22.66         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.