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ASASSN-17gt and ASASSN-17gu: Discovery of Two Probable Supernovae in CGCG 453-026 and SDSS J115131.21+152727.5

ATel #10431; G. Stone (Sierra Remote Observatories), P. Marples (Leyburn Observatory, Australia), R. S. Post (Post Astronomy), P. Cacella (DogsHeaven Observatory), J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, 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), G. Bock (Runaway Bay Observatory, Australia), I. Cruz (Cruz Observatory), J. M. Fernandez (Observatory Inmaculada del Molino), S. Kiyota (Variable Star Observers League in Japan), R. A. Koff (Antelope Hills Observatory), W. Wiethoff (University of Minnesota, Duluth)
on 27 May 2017; 20:44 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 #: 10435

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 n the galaxies CGCG 453-026 and SDSS J115131.21+152727.5.

ASASSN-17gt (AT 2017eio) was discovered in images obtained on UT 2017-05-24.59 at V~17.5 mag. We also detect the object in images obtained on UT 2017-05-26.59 (V~17.1) and UT 2017-05-25.59 (V~17.3). We do not detect (V>16.0) the object in images taken on UT 2017-05-22.63 and before. An image obtained on 2017-05-25 by R. Post confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the R. Post confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the R. Post image.

The position of ASASSN-17gt is approximately 3.4" South and 2.2" East from the center of the galaxy CGCG 453-026 (z=0.033470, d=136 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.3 (m-M=35.67, A_V=0.165).

ASASSN-17gu (AT 2017eip) was discovered in images obtained on UT 2017-05-26.34 at V~17.1 mag. We also detect the object in images obtained on UT 2017-05-27.34 (V~17.2), UT 2017-05-25.33 (V~17.4), and UT 2017-05-24.35 (V~17.4). We do not detect (V>17.8) the object in images taken on UT 2017-05-23.35 and before. An image obtained on 2017-05-27 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-17gu is approx. 2.4" South and 2.1" West from the center of the galaxy SDSS J115131.21+152727.5, which has no redshift available in NED. We also note that it is 1.4' southwest of the galaxy UGC 06831 (z=0.021277, d=93.6 Mpc, via NED).

Properties of the new sources and photometry are summarized below:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-17gt  22:55:37.11   +19:10:24.60     2017-05-24.59      17.5          -18.3               4.05 
ASASSN-17gu  11:51:31.07   +15:27:25.22     2017-05-26.34      17.1           N/A                3.19 
 
ASASSN-17gt: 
Obs. UT Date         V mag 
2017-05-22.63        >16.0 
2017-05-24.59         17.5 
2017-05-25.59         17.3 
2017-05-26.59         17.1 
 
ASASSN-17gu: 
Obs. UT Date         V mag 
2017-05-23.35        >17.8 
2017-05-24.35         17.4 
2017-05-25.33         17.4 
2017-05-26.34         17.1 
2017-05-27.34         17.2 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, 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 Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA). For more information about ASAS-SN, see the ASAS-SN Homepage and the list of all ASAS-SN transients.