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BVRI Photometry on MASTER OT in NGC 2748

ATel #10686; J. Vinko, K. Sarneczky, O. Hanyecz, A. Sodor (Konkoly Observatory)
on 30 Aug 2017; 20:21 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)

Subjects: Optical, Supernovae, Transient

We report photometric observations of the recently discovered optical transient MASTER OT J091344.71+762842.4 in NGC 2748 (ATel #10667), a possible supernova. The data were taken with the 60/90 cm Schmidt telescope through Bessell B,V,R,I filters at Konkoly Observatory, Piszkesteto, Hungary between Aug 25 and 29, 2017. The transient is clearly present on all images at the following position: R.A. = 09:13:44.666, Dec. = +76:28:44.51, which is about 2" North from the position announced by Balanutsa et al. in ATel #10667. PSF-photometry of the OT source and several local comparison stars, whose magnitudes were tied to their PS1-photometry after transforming the PS1 griz magnitudes to the Johnson-Cousins BVRI system (Magnier et al. arXiv:1612.05242), was computed with IRAF/DAOPHOT. The following Vega-magnitudes have been obtained for MASTER OT in NGC 2748:

 
 
  MJD       B     eB    V     eV    R     eR    I     eI 
57990.79  17.26  0.14 16.38  0.11 15.77  0.12 15.30  0.11 
57991.79  17.25  0.14 16.29  0.10 15.70  0.12 15.21  0.11 
57993.95  16.73  0.08 15.92  0.05 15.34  0.06 14.97  0.06 
57994.79  16.81  0.09 15.91  0.07 15.32  0.07 14.94  0.07 
 
The transient appears to be brightening rapidly, consistent with a supernova several days before maximum light. Adopting D = 19.6 Mpc distance for the host galaxy, NGC 2748, from NED, the latest extinction-corrected absolute magnitudes of the OT are M_B = -14.73 (+/- 0.10), M_V = -15.63 (0.07), M_R = -16.20 (0.08) and M_I = -16.55 (0.08). These data suggest that the transient is probably heavily reddened by dust within its host. Spectroscopic observations on this young transient are encouraged.