Electronic Telegram No. 2656

Central Bureau for Astronomical Telegrams
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138,
U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://www.cfa.harvard.edu/iau/cbat.html

SUPERNOVAE 2011X, 2011Y, AND 2011Z
[Note: this text replaces that on CBET 2652] G. Pignata and M. Cifuentes, Universidad Andres Bello; J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, R. Cartier, F. Forster, S. Silva, F. Carrasco, P. Sanchez, and C. Hervias, Universidad de Chile; P. Gonzalez, Pontificia Universidad Catolica de Chile (for SN 2011X only); B. Conuel, Wesleyan University; G. Folatelli, IPMU, University of Tokyo; and D. Reichart, K. Ivarsen, J. Haislip, A. Crain, D. Foster, M. Nysewander, and A. LaCluyze, University of North Carolina at Chapel Hill, on behalf of the CHASE project, report the discovery of three supernovae on unfiltered CCD images obtained with the 0.41-m 'PROMPT' telescopes located at Cerro Tololo; SN 2011X was found with the 'PROMPT 5' telescope, and the other two supernovae were found with the 'PROMPT 3' telescope. The discovery observations are tabulated below (positional uncertainty in the range +/- 0".2 to 0".3 in each coordinate):

2011 UT
R.A. (2000.0)
Jan. 15.25
13 50 21.36
-52 39 58.5
63" W, 20" S
Jan. 27.07
8 12 58.25
-27 34 15.7
Jan. 29.25
13 30 43.04
-20 57 14.0
1".0 W, 8".3 S

Additional approximate unfiltered CHASE magnitudes for 2011X (designated PSN J13502136-5239585 on the Central Bureau's TOCP webpage), which is thought to be connected with the galaxy ESO 221-7 = PGC 49121: 2009 June 4.06-2010 Aug. 14.07 UT, [21.0 (thirty 40-s archival images taken over this time span); 2011 Jan. 16.29, 17.2.
Additional approximate unfiltered CHASE magnitudes for 2011Y (designated PSN J08125825-2734157 on the Central Bureau's TOCP webpage), for which the faintness of the presumed host galaxy does not allow the measurement of reliable offsets between the supernova's position and the center of the galaxy: 2010 Dec. 31.23, [18.0; 2011 Jan. 8.18, [18.0; 28.05, 17.3.
Additional approximate unfiltered CHASE magnitudes for 2011Z (designated PSN J13304304-2057140 on the Central Bureau's TOCP webpage), which is thought to be connected with the galaxy ESO 576-77 = PGC 47494: 2010 Feb. 11.29, [18.5; June 27.02, [17.0; 2011 Feb. 2.28, (visible, but no mag provided).

M. Stritzinger, Oskar Klein Centre, Stockholm University; N. Morrell, Las Campanas Observatory; J. Anderson, F. Foerster, and M. Hamuy, Universidad de Chile; G. Pignata, Universidad Andres Bello; and G. Folatelli, University of Tokyo; on behalf of the Millennium Center for Supernova Science, report that they have obtained spectra (range 432.5-965.9 nm) of these three supernovae on Mar. 5.1 UT with the Magellan I Baade 6.5-m telescope (+ IMACS) at Las Campanas Observatory. The spectrum of SN 2011X indicates that it is an evolved type-IIP supernova; best matches with the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) suggest that 2011X is at least 3-4 months old. SN 2011Y is a normal type-Ia supernova around maximum light; adopting for the host galaxy a recession velocity of 20385 km/s (as derived by the SNID code, based on the spectral features of the supernova), an expansion velocity of 11000 km/s is computed from the absorption minima of the Si II 635.5-nm line.
SN 2011Z is a type-Ia supernova before maximum light. Cross-correlation with a library of supernova spectra using SNID provides a close match to the sub-luminous supernova 1986G (Phillips et al. 1987, PASP 99, 592). Adopting a SNID-derived host recession velocity of 6595 km/s, expansion velocities of 10500 km/s and 11000 km/s are derived from the absorption minima of the Si II 597.1- and 635.5-nm lines, respectively.

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars.

2011 Febrary 15
(C) Copyright 2010 CBAT
(CBET 2656)
Daniel W. E. Green