Electronic Telegram No. 1059 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2007if On August 28, F. Yuan, Physics Department, University of Michigan; and R. Quimby, University of Texas, on behalf of the ROTSE collaboration, reported the discovery of a variable object (mag 19.5 +/- 0.1) in Pisces on unfiltered CCD images taken on Aug. 16.29 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The new object, which was quickly posted on the Central Bureau's unconfirmed-objects webpage, is located at 1h10m51s.37, Decl. = +15o27'39".9 (equinox 2000.0; uncertainty < 1"). There were then 13 images showing the variable taken by the ROTSE-IIIb and by the ROTSE-IIIc telescopes at the H.E.S.S. site at Mt. Gamsberg, Namibia. Additional magnitudes (calibrated relative to R magnitudes from the USNO-B1.0 catalogue) for the variable: Aug. 14.30, [20.1; 19.28, 18.3; 22.01, 17.8; 24.26, 17.8; 26.38, 17.2; 26.98, 17.6. The field has been monitored by ROTSE-III telescopes on a daily basis before and after the discovery, weather permitting; the variable recently has remained around mag 17, up to Sept. 9.98 (when observed at the H.E.S.S. site). No object (including a possible host galaxy) is seen at this position in the Sloan Digital Sky Survey images, a Digitized Sky Survey image, or any USNO archive plates. A spectrum was taken with the MDM 2.4-m telescope by C. Peters and J. Thorstensen (Dartmouth College) around Aug 22.4 UT; the low S/N data may show a broad absorption feature around 575 nm. There might also be a P-Cyg feature at about 699 nm, which could be H-alpha at z = 0.066. However, none of these features are significant in the preliminary analysis, and thus no evidence can be claimed for determining the nature of the transient. Spectroscopy at the HET telescope on Aug. 29 also failed to show significant features that could identify the nature of the transient. Further information on the ROTSE observations including a finding chart and a light curve can be found at: http://www.rotse.net/transients/j0110+1527/index.html. Today, Yuan and Quimby, joined by C. Akerlof and J. Miller, University of Michigan; C. Peters and J. Thorstensen, Dartmouth College; by the "Nearby Supernova Factory" collaboration (C. Baltay, A. Bauer, D. Rabinowitz, and R. Scalzo, Yale University; G. Rigaudier and E. Pecontal, Centre de Recherche Astronomique de Lyon; C. Buton, Y. Copin, E. Gangler, G. Smadja, and C. Tao, Institut de Physique Nucleaire de Lyon; P. Antilogus, S. Bailey, R. Pain, R. Pereira, and C. Wu, Laboratoire de Physique Nucleaire et de Haute Energies de Paris; G. Aldering, C. Aragon, S. Bongard, M. Childress, S. Loken, P. Nugent, S. Perlmutter, K. Runge, R. C. Thomas, and B. A. Weaver, Lawrence Berkeley National Laboratory; D. Birchall, Institute for Astronomy, University of Hawaii, Hilo; and J. Cough, J. Holtzman, New Mexico State University, Las Cruces); and by A. Rau and M. Kasliwal, California Institute of Technology; and A. Gal-Yam, Weizman Institute of Science, Rehovot, Israel, report that the variable is spectroscopically similar to the possibly "super-Chandrasekhar-mass" type-Ia supernova 2003fg (cf. IAUC 8147, 8148; Howell et al. 2006, Nature 443, 308), and thus the new variable is hereby designated as SN 2007if. The "Nearby Supernova Factory" collaboration has independently discovered 2007if at mag 18.4 in images obtained on Aug. 25.4 UT using the QUEST-II camera on the Palomar Oschin 1.2-m Schmidt telescope, operated by the Palomar-QUEST Consortium. By Sept. 3, 2007if had brightened to mag 17.7 (both magnitudes calibrated to the R band, via comparison with the USNO-B1.0 catalogue); nothing was detected at this position in Palomar images obtained on Aug. 9.5 (no limiting magnitude provided). A spectrum (range 320-1000 nm) of 2007if, obtained on Aug. 26.5 with the SuperNova Integral Field Spectrograph (SNIFS) on the University of Hawaii 2.2-m telescope, consists of a blue continuum with scattered small- amplitude absorption features superimposed. Lacking additional constraints (such as host-galaxy redshift), the target was not positively identified as a type-Ia supernova. Additional spectroscopy of 2007if was obtained by Kasliwal, Rau, and Gal-Yam using the Double Spectrograph mounted on the Hale 5-m telescope at Palomar on Sept. 6.45; inspection of a quick reduction of this spectrum suggested that 2007if is a type-Ia supernova, and further analysis using the 'Superfit' supernova-spectral-identification code (Howell et al. 2005, Ap.J. 634, 1190) shows that the best matches are obtained with type-Ia supernovae well before peak, indicating that 2007if must have been detected shortly after explosion. An additional SNIFS spectrum of 2007if, obtained on Sept. 10.5, is an unambiguous match to that of SN 2003fg. A comparison plot (corrected to rest-frame, assuming z = 0.07 for this object) is available at http://snfactory.lbl.gov/snf/data/SNF20070825-001.png. The C II identification around 400 nm reported by Howell et al. can also be made for 2007if: after a small correction for the B-band telluric absorption, C II 658-nm is clearly visible, as predicted by Howell et al. Assuming z = 0.07 and the magnitudes reported above (as bright as mag 17), it is noted that 2007if is clearly overluminous (absolute magnitude M < -20) for a type-Ia supernova, agreeing well with the spectroscopic results and suggesting a "super-Chandrasekhar-mass" event. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2007 CBAT 2007 September 11 (CBET 1059) Daniel W. E. Green