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ASAS-SN Discoveries of a Probable Supernova in IC 0831 and a Possible Extreme (delta V > 6.6 mag) M-dwarf Flare

ATel #6168; T. W.-S. Holoien, B. J. Shappee, K. Z. Stanek, C. S. Kochanek, A. B. Davis, J. Jencson, U. Basu, J. F. Beacom (Ohio State), J. L. Prieto (Princeton), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory), D. Bersier (LJMU)
on 24 May 2014; 23:56 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 #: 6203

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 a probable new supernova in IC 0831 and a possible extreme M-dwarf flare:

 
Object         RA (J2000)     DEC (J2000)        Disc. UT Date    Disc. V mag 
ASASSN-14bd    12:52:44.86    +26:28:12.4        2014-05-22.35	     17.0 
ASASSN-14be    11:31:24.92    +04:41:16.5	 2014-05-24.29	     16.0 

ASASSN-14bd was discovered in images obtained 2014 UT May 22.35 at V~17.0 mag. We also detect the transient in images obtained on 2014 UT May 20.35 (V~17.0 mag), UT May 17.36 (V~17.0 mag) and UT 2014 May 24.30 (V~16.8 mag), but do not detect (V>17.0) this object in images taken on 2014 UT May 07.36 and before. This figure shows the ASAS-SN discovery subtraction image (top left), the latest ASAS-SN subtraction image from May 24 (top right), the ASAS-SN V-band reference image (bottom left), and archival SDSS g-band image (bottom right). The green circle has a radius of 3.5'' at the ASAS-SN position of the SN candidate.

ASASSN-14bd's position in the ASAS-SN images is 10.2'' W and 0.6'' S of the center of IC 0831 (z=0.021405, d=93.3 Mpc, via NED), giving an absolute V-band magnitude of approx. -18.1 (m-M=34.85, A_V=0.032, Schlafly & Finkbeiner 2011) in the most recent data.

ASASSN-14be was discovered in images obtained 2014 UT May 24.29 at V~16.0 mag and is undetected (V>16.9) in images obtained 2014 UT May 24.30 (15 minutes later). A cross-check of the ASAS-SN position in Vizier reveals that the nearest source is a faint (g~23.9) and red (g-r=0.7) star roughly 4.3'' away from our position. The line-of-sight Galactic extinction at this position is A_V=0.098 (Schlafly & Finkbeiner 2011), so nearby sources are not likely to be significantly reddened. Due to the lack of sources closer to our position, we believe ASASSN-14be is a flare from either the faint star or a source that is undetected in the SDSS images. This figure shows the ASAS-SN discovery subtraction image (top left), the latest ASAS-SN subtraction image from 15 minutes later (top right), the ASAS-SN V-band reference image (bottom left), and archival SDSS z-band image (bottom right). The green circle has a radius of 3.5'' at the ASAS-SN position of the transient.

Using the limiting g-band and r-band magnitudes of 22.2 for SDSS gives a conservative limiting V-band magnitude of V>22.6, and the nearby star has V~23.7. This implies that, regardless of the source, ASASSN-14be is likely an extreme delta V>6.6 mag flare.

Follow-up observations of both transients 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.