[vsolj-alert 486] SNe 1999ga and 1999gb

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

cf. [vsnet-alert 3732] [FWD] KAIT SN candidate in NGC 2532
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/msg03732.html
cf. [vsnet-alert 3733] another possible SN in the south
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/msg03733.html
cf. [vsnet-alert 3735] KAIT SN candidate in NGC 2532
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/msg03735.html
[vsnet-chart 222] Chart of SN? in NGC2532
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chart/msg00222.html
[vsnet-chat 2420] Host galaxy of SN? in NGC2532
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chat/msg02420.html
[vsnet-chat 2421] Host galaxy of SN? in NGC2442
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chat/msg02421.html

Dear SN watchers,

  Two supernovae announced yesterday had formally designated as SNe
1999ga and 1999gb on IAUC 7316.  The object in the south found by
Perth team is the former, and the latter is the KAIT object.

  SN 1999ga was discovered on Nov. 19.76 UT by Perth group.  It is
located on R.A. = 7h36m16s.70, Decl. = -69o33'21".8 (2000.0), which is
about 38" west and 91" south of the nucleus of NGC 2442, the large SBb
galaxy with S-shaped arm.  This object lies between the disk and the
southern arm. 

  Because of rather low b (-21o), there are some field stars, as well
as the blobs in the host galaxy.  In the neighbourhood of SN, a 16-17
mag star exists at 42" west and 130" south from the nucleus of the
host. 

  The reported magnitudes are: on Nov. 19.76 UT, R about 18; Nov.
22.54, C about 18.5 +/- 1.  The recession velocity of the host is
about 1400 km/s, which indicates that the typical SN II on this galaxy
would be about 15 mag or so at its maximum.  SN 1999ga is quite
dimmer (though the discovery image, at
http://vsnet.parg.asn.au/SNe/sn99xx.html , shows somewhat brighter
magnitude than reported).  It can be due to the interstellar
obscuration, well past maximum brightness, or intrinsically
sub-luminous.  

  GSC mags in this field (J mag, which is near to B mag) are quite 
dimmer than USNO rmags.  The observers without blue filter cannot use
GSC mags for comparison.  

  The second one, SN 1999gb, is discovered on Nov. 22.4 by the LOSS
KAIT team.  The location is: R.A. = 8h10m13s.70, Decl. = +33o57'29".8
(2000.0), which is about 19" west and 6" north from the nucleus of the
host Sc (with bright inner arms) galaxy NGC 2532.  The SN lies on the
west end of the inner arm.  Some blobs (or foregroud stars?) are there
in the outer west-south arm, whose magnitudes are about 16-18 mag.  

  The reported magnitudes are: Nov. 22.4, 16.1C; 23.4, 15.9C, which
indicate that it seems to be in the rising phase.  The recession
velocity of the host is about 5000 km/s, so the expected maximum of
a typical SN Ia is around 16 mag.  SN 1999gb should be a bright
supernova. 

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

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