Electronic Telegram No. 2708 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network SUPERNOVA 2011by IN NGC 3972 = PSN J11554556+5519338 Zhangwei Jin, Ningbo, Zhejiang, China; and Xing Gao, Urumqi, Xinjiang, China, report the discovery of a possible supernova (mag approximately 14.2) on a 60-s survey image (limiting mag about 19.5) taken by Xing Gao in the course of the Xingming Observation Sky Survey around Apr. 26.8234 UT using a Celestron C14 Schmidt-Cassegrain telescope (+ unfiltered CCD camera) at Mt. Nanshan. The new object is approximately located at R.A. = 11h55m45s.56, Decl. = +55d19'33".8 (equinox 2000.0), which is about 5".3 east and 19".1 north of the center of the galaxy NGC 3972. Nothing is visible at this position on archival images taken on Apr. 8 and 10 (limiting mag 19.5) or on a Digitized Sky Survey image from 1991 May 7 (limiting mag about 19.5; no plate type or bandpass noted). The discovery image is posted at the following website URL: http://www.xjltp.com/XOSS/XM20ZJ/XM20ZJ.htm. This variable was designated PSN J11554556+5519338 when posted at the Central Bureau's TOCP webpage and is here designated SN 2011by based on the spectroscopic report below. Joseph Brimacombe, Cairns, Australia, reports that he obtained unfiltered CCD images remotely using a 51-cm RCOS telescope (+ STL11K camera) at the New Mexico Skies Observatory near Mayhill, New Mexico, on Apr. 27.332 UT, yielding mag 14.5 and position end figures 45s.57, 33".9 for 2011by. He has posted his image at website URL http://www.flickr.com/photos/43846774@N02/5661036373/. T. Zhang and Z. Zhou, National Astronomical Observatories of China (NAOC); X. Wang, Tsinghua Center for Astrophysics, Tsinghua University, report on an optical spectrum (range 350-870 nm) of PSN J11554556+5519338 = SN 2011by that was obtained on Apr. 27.5 UT with the 2.16-m telescope (+ BFOSC) at the Xinglong Station of the NAOC. The spectrum is consistent with that of a type-Ia supernova at very young phase. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that this supernova matches that of SN 2003du at about 10 days before maximum. After removal of the host-galaxy recession velocity of about 850 km/s, they find the absorption minimum of the Si II 635.5-nm line to be blueshifted by about 12000 km/s. Further follow-up observations of this object are encouraged. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 April 28 (CBET 2708) Daniel W. E. Green