http://cfa-www.harvard.edu/iau/cbet/RecentCBETs.htmlCBET 1174 : 20071220 : SUPERNOVA 2007sr IN NGC 4038
SUPERNOVA 2007sr IN NGC 4038
G. Umbriaco, T. Pietrogrande, and F. Di Mille, Dipartimento di Astronomia,
Universita' di Padova; and I. Agnoletto, A. Harutyunyan, and S. Benetti,
Istituto Nazionale di Astrofisica and Osservatorio Astronomico di Padova,
report that a spectrogram (range 335-770 nm, resolution 0.9 nm) of 2007sr (cf.
CBET 1172, 1173), obtained on Dec. 20.22 UT at Asiago with the Galileo 1.22-m
telescope (+ Boller & Chivens spectrograph), shows it to be a type-Ia
supernova. Assuming a recession velocity of 1642 km/s (Lauberts and Valentijn
1989, The Surface Photometry Catalogue of the ESO-Uppsala Galaxies; via NED)
for the host galaxy, the 'PASSparToo' spectrum-comparison code (Harutyunyan et
al. 2005, ASP Conf. Ser. 342, 258) provides good fits to spectra of SNe 1996Z
and 2002bo at five and four days after B-maximum light, respectively. The
phase is confirmed by the high expansion velocity deduced from the Si II
635.5-nm absorption feature (about 12100 km/s) shown by the HVG class (Benetti
et al. 2005, Ap.J. 623, 1011) during the photospheric phases.
Visual magnitude estimate by P. Schmeer, Bischmisheim, Germany:
Dec. 20.249 UT, 12.8.
CBET 1173 : 20071220 : SUPERNOVA 2007sr IN NGC 4038
SUPERNOVA 2007sr IN NGC 4038
H. Naito, Nishi-Harima Astronomical Observatory (NHAO); and Y. Sakane,
T. Anan, S. Kouzuma, and H. Yamaoka, Kyushu University, report that a low-
resolution (R about 400) spectrum of 2007sr (cf. CBET 1172) was obtained on
Dec. 19.87 UT with the 2.0-m NAYUTA telescope at NHAO, showing a somewhat-blue
continuum with broad absorption features (Si II and Fe II are prominent),
which suggests that it is a type-Ia supernova a few days before maximum.
The expansion velocity, derived from the Si II 635.5-nm absorption minimum,
is 12300 km/s. Preliminary magnitudes from the images taken with the same
instrument are as follows: Dec. 19.81, B = 13.42; 19.78, V = 12.86.
CBET 1172 : 20071219 : SUPERNOVA 2007sr IN NGC 4038
SUPERNOVA 2007sr IN NGC 4038
A. J. Drake, S. G. Djorgovski, R. Williams, A. Mahabal, and M. J.
Graham, California Institute of Technology; E. Christensen, Gemini
Observatory; and E. C. Beshore and S. M. Larson, Lunar and Planetary
Laboratory, University of Arizona, report the discovery of an apparent
supernova (mag approximately 12.9) in four 30-s CCD exposures (limiting mag
about 20) taken in the course of the Catalina Sky Survey (CSS) on Dec. 18.53
UT using the 0.7-m f/1.9 Schmidt telescope (+ 4000x4000 camera). The new
object, now designated 2007sr, is located at R.A. = 12h01m52s.80, Decl. =
-18o58'21".7 (equinox 2000.0), and appears on one of the arms (or "antennae")
emanating from NGC 4038 (which is interacting with the galaxy NGC 4039).
Nothing appears at this position in co-added CSS images from 2006 Dec. 21
(limiting mag about 21.5); also, nothing definite appears on mutliple
exposures obtained on 1999 Feb. 22 with the Hubble Space Telescope (+ WFPC2
+ F814W filter), though it is possible that a precursor as bright as I-band
mag about 23 is present therein. CSS images of 2007sr are posted at this
website URL:
http://www.cacr.caltech.edu/~ajd/CSS_ATEL/712180180624111439.html E. Guido and G. Sostero (Remanzacco, Italy) write that five co-added
60-s CCD frames taken remotely with a 0.25-m f/3.4 reflector located near
Mayhill, NM, U.S.A., on Dec. 19.42 show 2007sr at position end figures
52s.80, 21".8 and magnitudes B = 13.20, V = 12.85, R = 12.80 (uncertainty
+/- 0.05 magnitude in each color). Their image is posted at this website URL:
http://www.fototime.com/%7B885F3FF0-0039-47A9-A815-71150CC0EC7B%7D/picture.JPG W. Li, Unversity of California at Berkeley, reports that 2007sr
appears at mag 12.9 and position end figures 52s.79, 21".3 on KAIT images
(cf. CBET 1179) taken on Dec. 19.52 UT.
SNe 1921A, 1974E (cf. IAUC 2653), and 2004gt (cf. IAUC 8454, 8456) also
appeared in NGC 4038.
