ASAS-SN Discovery of a Likely Supernova in SDSS J102131.91+082419.8 and a Bright Transient in 2MASX J12141125+3839400

ATel #6152; B. J. Shappee, A. B. Davis (Ohio State), J. Brimacombe (Coral Towers Observatory), T. W.-S. Holoien, K. Z. Stanek, C. S. Kochanek, J. Jencson, U. Basu, J. F. Beacom (Ohio State), J. L. Prieto (Princeton), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), D. Bersier (LJMU)
on 21 May 2014; 02:31 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Benjamin Shappee (shappee@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 "Brutus" telescope in Haleakala, Hawaii, we discovered two new transient sources, a probable supernovae in SDSS J102131.91+082419.8 and a bright transient in 2MASX J12141125+3839400.

 
Object       RA (J2000)   DEC (J2000)      Disc. UT Date   Disc. V mag 
ASASSN-14ba  10:21:31.9   +8:24:21.12       2014-05-19.29      16.6 
ASASSN-14bb  12:14:11.3   +38:39:40.8       2014-05-19.33      16.0 

ASASSN-14ba was discovered in images obtained 2014 UT May 19.29 at V~16.6 mag. We also detect the object in images obtained on May 17.28. We do not detect this object, V<15 and V<17, in images taken on 2014 UT May 13.3 and April 17.3, respectively. An image obtained on UT May 20.18 with the RCOS 51-cm telescope in New Mexico (obtained by J. Brimacombe) confirms the discovery of the new transient. This figure shows the ASAS-SN reference image (top left), archival SDSS g-band image (top right), ASAS-SN discovery subtraction image (bottom left), and the confirmation image (bottom right). The green circle has a radius of 3.0" at the position of the SN.

ASASSN-14ba is approximately 1.3" North and 0.5" West of the core of SDSS J102131.91+082419.8 (z=0.032668, d=143 Mpc, via NED), which would give it an absolute V mag of approx. -19.1 (m-M=35.77, A_V=0.080, Schlafly & Finkbeiner 2011). Follow-up observations are encouraged.

ASASSN-14bb was discovered in images obtained 2014 UT May 19.33 at V~16.0 mag. We also detect the transient at roughly the same magnitude in images obtained on 2014 UT May 20.27. We do not detect (V<17.0) this object in images taken on 2014 UT May 6.3 and before. This figure shows the ASAS-SN reference image (top left), archival SDSS g-band image (top right), ASAS-SN discovery subtraction image (bottom left), and the ASAS-SN confirmation subtraction image (bottom right). The green circle has a radius of 3.0" at the position of the SN.

The transient's position in the ASAS-SN data is consistent with the position of the galaxy 2MASX J12141125+383940 (PhotZ = 0.061 +/- 0.024, from SDSS). There is no strong variability in CRTS at the transient position and the potential host galaxy is not a known AGN. The ASAS-SN coordinates of the source are consistent with the center of the galaxy, implying this could be a supernova, activity of a previously unknown AGN, or potentially something more exotic, such as a tidal disruption event. If we take the SDSS PhotZ redshift at face value (including its errors), the luminosity distance of the source would be d~260 +/- 110 Mpc, giving an absolute V mag of approx. -21.1 +/- 1.0 (m-M=37.1 +/- 1.0, A_V=0.042, Schlafly & Finkbeiner 2011). Follow-up observations, especially spectroscopy, are encouraged.

We thank LCOGT and its staff for their continued support of ASAS-SN. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.