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IAUC 7680: 2001dh, (2001dj) and 2001dl; WZ Sge

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                                                  Circular No. 7680
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

SUPERNOVAE 2001dh, (2001dj) and 2001dl
     F. Patat, European Southern Observatory; C. Contreras and J. Prieto,
Universidad Catolica de Chile; and G. Altavilla, S. Benetti, E. Cappellaro, A.
Pastorello and M. Turatto, Osservatorio Astronomico di Padova, report:
"Spectra of three candidate supernovae were obtained on Aug. 8 using the
Danish 1.5-m telescope + DFOSC (spectral range 320-900 nm, resolution 1.2 nm)
at La Silla.  2001dh (IAUC 7670) is a type-II supernova, about 1 month after
maximum, the spectrum being dominated by the H alpha P-Cyg line with the
absorption minimum measured at 641 nm and yielding an expansion velocity of
about 9000 km/s, assuming the NED recession value of 2608 km/s for the parent
galaxy; other strong lines are H beta (478 nm), Fe II (513 and 497 nm) and
Ca II (842 nm).  2001dj (IAUC 7674) is not a supernova but most likely a
galactic variable of early-F spectral type.  2001dl (IAUC 7675) is a type-Ia
supernova, its spectrum being very similar to that of SN 1994D at maximum
(cf. Patat et al. 1996, Monthly Notices Roy. Astron. Soc. 278, 111); the
characteristic Si II absorption is measured at 627 nm, and given the NED
recession velocity of 6204 km/s for the parent galaxy, the expansion velocity
is as large as 10 000 km/s."

    T. Kato, H. Ohashi, R. Ishioka, M. Uemura and K. Matsumoto, Kyoto
University; G. Masi and F. Mallia, Ceccano, Italy; D. Starkey, Auburn, Indiana;
J. Pietz, Erftstadt, Germany; B. Martin, Edmonton, Alberta; G. A. Good,
Albuquerque, New Mexico; and M. Richmond, S. Davis and T. Davis, Rochester,
New York, on behalf of the VSNET collaboration team, report: "Our latest
time-resolved CCD photometry (IAUC 7678) confirmed that there was an
interchange of the main maxima from early to 'genuine' superhumps around
Aug. 5.8 UT.  The signal of superhumps further evolved, and their times of
maxima during Aug. 5.25-11.12 are well represented by HJD(max)
= 2452126.755 + 0.057153(16)E.  The residuals from this ephemeris show a
systematic variation with probable period 4 days.  This variation is most
likely due to the beat between the orbital and superhump periods.
On Aug. 9 the superhumps showed prominent 'secondary superhumps' at phase
0.4, and these became even stronger on Aug. 10, gradually merging into
singly-peaked superhumps on Aug. 11.1.  The present finding concerning the
evolution and period of superhumps provides higher-quality confirmation of
the interpretation of the early behavior of the 1978 outburst proposed by
Bohusz and Udalski (IBVS 1583)."  Masi provides the following improved
position for WZ Sge (10 USNO-A2.0 reference stars): R.A. = 20h07m36s.53,
Decl. = +17d42'15".3 (J2000.0, mean residual 0".25).

                      (C) Copyright 2001 CBAT
2001 August 11                 (7680)              Brian G. Marsden

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