Rare outburst of OY Car

(vsnet-alert 802)

The UGSU type variable star OY Car is in outburst this evening

   OY Car       1997 Mar 25.424 UT           11.7
                         25.454                11.6

Also, HL CMa at it again
HL CMa      1997 Mar 25.434 UT           11.0

Full moon present.

Michael Mattiazzo,
Adelaide, South Australia

(vsnet-alert 804)

I am looking for confirmation of the AAVSO report (AAVSO News Flash #132) that the SU UMa-type dwarf nova OY Car (RA=10:06:22.3, DEC=-70:14:05.0, epoch 2000) is in outburst (V<12). If the outburst is confirmed, an EUVE Target of Opportunity observation will begin as early as DOY 85 22 UT (in less than 24 hrs). Please send visual magnitude estimates to the address below asap. If the source is in outburst, regular monitoring throughout the outburst would be of great value.


| Christopher W. Mauche                  Phone: (510) 422-7017         
| Lawrence Livermore Nat'l Lab.          Fax:   (510) 423-7228         
| L-41, P.O. Box 808                     e-mail: mauche@cygnus.llnl.gov
| Livermore, CA 94550                       or:  mauche@llnl.gov       

(vsnet-alert 805)

One estimate of OY Carinae, under difficult conditions:

OY CAR March 26.802 UT 11.1 HJN

Thank goodness the heavy clouds have gone, but there is till a lot of thin cloud - and the Moon!

Jan Hers, Sedgefield, South Africa.

(vsnet-alert 806)

Following the initial alert by Michael Mattiazzo (vsnet-alert 802), following observations have been reported to vsnet-alert and vsnet-obs.

   YYMMDD(UT)   mag  code
   970312.497  <127  MKA
   970316.433  <127  MKA
   970325.424   117  MKA
   970325.453   116  MKA
   970325.562   116  MKA
   970326.417   114  MKA
   970326.458   115  MKA
   970326.500   116  MKA
   970326.542   115  MKA
   970326.801   111  HJN
Judging from the brightness and duration, the present outburst may well be a superoutburst, since its last one in 1995 October - November.

OY Car is one of the most well-known eclipsing SU UMa-type dwarf novae, which have been and will be teaching us much about the physical processes going in superoutbursting dwarf novae. OY Car has played an important role in this field [1,2,3].

[1] J. H. Wood et al., 1989, ApJ 341, 974
[2] F. V. Hessman et al., 1992, AsAp 263, 147
    (OY Carinae: the secrets of the super-humps revealed)
[3] I. Billington et al., 1996, MNRAS, 279, 1274 and references therein
I would also like to urge visual (and CCD, of course) observers to record spectacular eclipses (together with possible superhumps) of this short-period cataclysmic binary. A good northern example may be found at (http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/htcas.html).

According to [1], eclipse are expected to occur:

   HJED = 2443993.553691 + 0.0631209295 E
                   +/-50          +/-20
Taichi Kato

Some links to eclipsing dwarf novae

HT Cas



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