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ASAS-SN Discovery of Two Probable Supernovae in CGCG 257-002 and SDSS J145027.61+063713.3

ATel #7811; J. Nicolas (Groupe SNAUDE, France), S. Kiyota (Variable Star Observers League in Japan), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. S. Brown, A. B. Danilet, G. Simonian, U. Basu, J. F. Beacom, T. A. Thompson (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong (KIAA-PKU), J. Brimacombe (Coral Towers Observatory), E. Falco (CfA), P. R. Wozniak (LANL), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), J. M. Fernandez (Observatory Inmaculada del Molino), R. A. Koff (Antelope Hills Observatory), G. Masi (Virtual Telescope Project, Ceccano, Italy), L. A.G. Monard (Klein Karoo Observatory), B. Nicholls (Mt. Vernon Obs., New Zealand)
on 19 Jul 2015; 03:05 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 #: 7826, 7877

During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered two new transient sources, most likely supernovae, in the galaxies CGCG 257-002 and SDSS J145027.61+063713.3.

ASASSN-15mr was discovered in images obtained on UT 2015-07-18.42 at V~17.4 mag. We also detect the object in images obtained on UT 2015-07-13.37 (V~17.5) and UT 2015-07-07.55 (V~16.6). We do not detect (V>16.5) the object in images taken on UT 2015-07-06.55 and before. An image obtained by J. Nicolas on UT 2015-07-18.86 using a 0.41-m telescope at Observatoire Chante-Perdrix-Dauban, France confirms the discovery of the transient. This figure shows the archival DSS image of the host (left) and the J. Nicolas confirmation image (right). The red circle has a radius of 3" and is centered on the position of the transient in the J. Nicolas image.

The position of ASASSN-15mr is approximately 0.2" North and 0.1" West from the center of the galaxy CGCG 257-002 (z=0.026759, d=110 Mpc, via NED), giving an absolute V-band magnitude of approximately -18.1 (m-M=35.20, A_V=0.323).

ASASSN-15ms was discovered in images obtained on UT 2015-07-18.32 at V~17.3 mag. We also detect the object in images obtained on UT 2015-07-09.29 (V~17.2). We do not detect (V>17.4) the object in images taken on UT 2015-07-05.34 and before. An image obtained by S. Kiyota on UT 2015-07-18.89 using a 0.43m CDK + STL-11000M at the ITelescope.NET site at Nerpio, Spain 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 4" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-15ms is approximately 1.6" South and 1.7" West from the center of the galaxy SDSS J145027.61+063713.3 (z=0.044107, d=190 Mpc, via NED), giving an absolute V-band magnitude of approximately -19.2 (m-M=36.40, A_V=0.095).

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-15mr  19:39:56.82    +50:55:28.49      2015-07-18.42      17.4          -18.1               0.22 
ASASSN-15ms  14:50:27.50    +06:37:11.69      2015-07-18.32      17.3          -19.2               2.33 

ASASSN-15mr photometry:

 
Obs. UT Date         V mag 
2015-07-06.55        >16.5 
2015-07-07.55         16.6 
2015-07-13.37         17.5 
2015-07-18.42         17.4 

ASASSN-15ms photometry:

 
Obs. UT Date         V mag 
2015-07-05.34        >17.4 
2015-07-09.29         17.2 
2015-07-18.32         17.3 

Follow-up observations of both sources are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported in part by 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.