ASAS-SN Discovery of A Bright Transient in ESO 375-G041

ATel #7406; T. W.-S. Holoien, K. Z. Stanek (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), Subo Dong (KIAA-PKU), C. S. Kochanek, A. B. Danilet, G. Simonian, U. Basu, N. Goss, J. F. Beacom, T. A. Thompson (Ohio State), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), P. R. Wozniak (LANL), E. Falco (CfA), J. Brimacombe (Coral Towers Observatory), D. Szczygiel, G. Pojmanski (Warsaw University Observatory)
on 17 Apr 2015; 04:27 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Thomas Holoien (tholoien@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 double 14-cm "Cassius" telescope in Cerro Tololo, Chile, we discovered a bright new transient source near the nucleus of the galaxy ESO 375-G041.

ASASSN-15hf was discovered in images obtained on UT 2015-04-17.05 at V~14.9 mag. We also detect the object in images obtained on UT 2015-04-14.21 (V~15.7) and UT 2015-04-12.11 (V~16.6). We do not detect (V>16.8) the object in images taken on UT 2015-04-11.19 and before. This figure shows the archival DSS image of the host (left), the ASAS-SN V-band reference image of the host (center), and the 2015-04-17 ASAS-SN V-band subtraction image (right). The red circle has a radius of 7.0" and is centered on the position of the transient in the ASAS-SN data.

The position of ASASSN-15hf is approximately 0.3" North and 2.9" West from the center of the galaxy ESO 375-G041 (z=0.006178, d=29.9 Mpc, via NED), giving an absolute V-band magnitude of approximately -17.8 (m-M=32.38, A_V=0.273). Given the ASAS-SN pixel scale of 7.8 arcsec/pixel and uncertainties in the astrometry, the transient’s position is potentially consistent with the nucleus of the host. The host galaxy does not appear to be an AGN, based on spectra available in NED. Properties of the new source 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-15hf  10:29:30.76    -35:15:35.2      2015-04-17.05      14.9          -17.8               2.92 

 
Obs. UT Date         V mag 
2015-04-11.19        >16.8 
2015-04-12.11         16.6 
2015-04-14.21         15.7 
2015-04-17.05         14.9 

Follow-up observations, particularly spectroscopy, 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.