SUPERNOVA 2008S IN NGC 6946
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R. Arbour, South Wonston, Hants, U.K., reports his discovery of an
apparent supernova (mag 17.6) on an unfiltered CCD image (limiting magnitude
about 18.6) taken on Feb. 1.7889 UT using a 30-cm f/6.3 Schmidt-Cassegrain
reflector (+ Starlight Xpress CCD camera) in the course of his supernova
patrol. The new object is located at R.A. = 20h34m45s.35, Decl. =
+60o05'57".8 (equinox 2000.0), which is 53" west and 196" south of the center
of NGC 6946. Nothing is visible at this position on the Digitized Sky Survey
blue (1990 Aug. 15) or red (1991 July 11) plates. Arbour adds that eight
confirming images of 2008S taken by T. Boles (Coddenham, England) on Feb.
2.763 yields magnitude 17.1 and position end figures 45s.36, 57".9.
Eight previous supernovae have been recorded in NGC 6946, all brighter than
mag 15 except for 2002hh (cf. IAUC 8005, 8007), which was highly reddened.
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
2008 February 2 (CBET 1234) Daniel W. E. Green
SUPERNOVA 2008S IN NGC 6946
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V. Stanishev, Physics Department, Stockholm University; and A.
Pastorello, Queen's University; report that a spectrum of SN 2008S (cf. CBET
1234), obtained on Feb. 4.83 UT with the Nordic Optical Telescope (+ ALFOSC;
range 350-900 nm) by T. Pursimo,
shows that it is likely a young, reddened,
type-IIn supernova. The spectrum consists of a nearly featureless red
continuum with superimposed strong, narrow H_beta and H_alpha emission lines
(
FWHM about 1000 km/s). A strong interstellar Na I absorption line with an
equivalent width of about 0.5 nm is visible at 588.8 nm.
Further to CBET 1234, R. Arbour provides the following additional CCD
magnitudes for 2008S, obtained with a 40-cm f/5 reflector:
Jan. 24.000 UT,
17.8 (limiting mag about 18.2; pre-discovery); Feb. 4.771, 17.2 (limiting
mag about 18.6).
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
2008 February 5 (CBET 1235) Daniel W. E. Green
SUPERNOVA 2008S IN NGC 6946
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P. Schmeer, Bischmisheim, Germany, reports the following unfiltered CCD
magnitude estimates of 2008S (cf. CBETs 1234, 1235) from exposures taken with
the University of Iowa's 0.37-m Cassegrain "Rigel telescope" in Arizona:
2007 Dec. 18.089 UT, [18.5; 2008 Jan. 30.529, 16.7 (limiting mag about 18.0).
Schmeer also provides the following position for 2008S: R.A. = 20h34m45s.33,
Decl. = +60o05'58".4 (equinox 2000.0).
V. Stanishev, Physics Department, Stockholm University; and A.
Pastorello, Queen's University, report that the magnitude of SN 2008S,
measured on an R-band image obtained on Feb. 4.83 UT with the Nordic Optical
Telescope (+ ALFOSC) by T. Pursimo, is R = 16.43; the magnitude is measured
relative to star 5 (R = 14.336) from Sahu et al. (2006, MNRAS 372, 1315).
2008 February 5 (CBET 1236) Daniel W. E. Green
Все фотометрические данные говорят о том, что вспышка произошла не позднее 24 января 2008 года, скорость разлета оболочки мала (1000км/с), абсолютный блеск не поднимается выше M=-12.0
m, при том что спектр схож с ранним этапом вспышки сверхновой типа IIn (явно снятый уже через 12 суток после начала вспышки - а это совершенно
не ранний этап!).
Вывод: это не сверхновая! это вспышка яркой голубой переменной (Luminous Blue Variable, LBV) 
!