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Discovery of two optical transients ROTSE3 J162148.5+370341 and ROTSE3 J004548.3+430222

ATEL # 1702; F. Yuan (U. Mich.), R. Quimby (Caltech), D. Chamarro (U. Mich.), A. Uecker (Indiana U. of Pennsylvania), M. D. Sisson, C. Akerlof, (U. Mich.) and J. C. Wheeler (U. Texas) on behalf of the ROTSE collaboration
on 8 Sep 2008; 3:30 UT
Password Certification: Fang Yuan (

Subjects: Optical, Nova, Supernova, Transients
Referred to by ATEL #: 1708

We report the discovery of two optical transients in unfiltered CCD images taken with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory, Texas.

We propose the first transient to be an apparent supernova. The transient, located at RA: 16:21:48.53 Dec: +37:03:41.0 (J2000, uncertainty <1 "), is 0.0" west and 2.1" north from center of its apparent host SDSS J162148.53+370338.9 at z=0.030. It was discovered at ~17.1 mag on Aug 4.17 UT by subtracting a reference built from images taken in August 2007. It was observed to rise to ~16.8 mag on Aug 10.18 UT and then decayed to ~17.4 mag on Aug 20.14 UT. A finding chart of the transient can be found at

The second transient, located at RA:00:45:48.25 Dec:43:02:22.2 (J2000, uncertainty <1"), is 34'34" east and 106'14" north (~25 kpc) from center of M31. It was discovered at ~18.4 on Aug 25.23 UT. It was also detected by ROTSE-IIId telescope on Bakirlitepe, TUBITAK National Observatory, Turkey. It peaked at ~18.1 mag on Aug 26.43 UT, decayed to ~19.2 mag on Aug 30.90 UT and then rose again to ~18.4 mag on Sep 5. 19 UT. The fast evolving multi-peaked lightcurve is not typical of a nova. Inspection of V-band INT archive images taken on 2001 Oct 16 revealed a possible counterpart, with a crude magnitude estimate of ~23.0. However, the field is relatively crowed and the actual correlation is uncertain. Spectral observation is desired to clarify the nature of this event. A finding chart of the transient can be found at The ROTSE lightcurve of the transient can be found at

The ROTSE magnitudes quoted above are unfiltered calibrated to USNO-B1.0 R.

The INT data were obtained from the Isaac Newton Group Archive which is maintained as part of the CASU Astronomical Data Centre at the Institute of Astronomy, Cambridge.

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R. E. Rutledge , Editor
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