THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
25 Birch Street, Cambridge, MA 02138 USA
INTERNET: aavso@aavso.org
Tel. 617-354-0484 FAX 617-354-0665
AAVSO ALERT NOTICE 230 (October 16, 1996)
1343+61 SUPERNOVA 1996bk IN NGC 5308
We have been informed by Stefano Pesci, Milan, Italy, the Central Bureau for
Astronomical Telegrams (IAU Circular 6491), and Guy Hurst (The Astronomer
Electronic Circular 1133) of the visual discovery by Pesci and Piero Mazza,
Milan, Italy, of a supernova in NGC 5308 at magnitude 14.5-15.0 on October
12.79 UT; Pesci reports that it is "quite separated from the nucleus." No
object was seen at this location by Pesci on August 15. The supernova was
confirmed visually by M. Schwartz, Cascade Mountains, OR, by CCD on Oct 13.3 UT.
P. Garnavich and R. Kirshner, Harvard-Smithsonian Center for Astrophysics,
report that spectra obtained on Oct 15.1 UT by J. Huchra and L. Macri with the
1.5-m Tillinghast telescope confirm the supernova in NGC 5308 as a type-Ia
supernova about a week past maximum. They also report that, according to CCD
images taken with the Whipple Observatory 1.2-m telescope, the supernova is
10.5" south and 17.9" west of the galaxy center, and at the time of exposure
was magnitude V = 15 (IAU Circular 6491).
J. Mackey, Werrington, England, used a CCD with Visual filter to estimate
the supernova's brightness at 14.05 V on Oct 13.795 UT, and provides the
following position (2000):
R.A. = 13h 46m 57.98s Decl. = +60 degrees 58' 12.9"
Additional observations of the supernova in NGC 5308 include Oct 13.8201 UT,
13.9, G. Comello, Groningen, Netherlands and Oct 14.8021, 14.1, Comello.
Accompanying is an excerpt from the AAVSO Variable Star Atlas showing the
location of NGC 5308, along with an image of the galaxy from Vickers'
Deep Space CCD Atlas: North. An additional image of NGC 5308 may be found on
the web page of the International Supernova Network at the address
http://www.queen.it/web4you/noprofit/isn/isn.htm
Also accompanying is an AAVSO preliminary "e" chart for NGC 5308 prepared by
C. Scovil. Please use this chart to make estimates of the supernova and report
your observations of 1343+61 SN 5308 to AAVSO Headquarters by email, telephone,
or fax, indicating which comparison stars you have used.
Congratulations to Stefano and Piero on their latest discovery!
FADING OF 0059+53 NOVA CASSIOPEIAE 1995
The very interesting nova, N Cas 95 (see AAVSO Alert Notices 213, 214, 217, and
particularly 218), is fading, as the observations reported to the AAVSO from
observers around the world and shown in the accompanying light curve indicate.
Since its behavior was described in AAVSO Alert Notice 218, N Cas 95 has
brightened three more times before beginning its present decline. The most
recent observations show it to be at visual magnitude 10.2.
While the overall optical behavior of this nova was initially quite similar to
that of HR Del, whose light curve we published in AAVSO Alert Notice 213, its
recent behavior is unique to this slow nova.
The accompanying light curve of N Cas 95 from its discovery on August 24, 1995,
through October 14, 1996, consists of 7487 visual, CCD, and CCDV observations
from 245 observers worldwide. We thank each observer for his or her valuable
contribution.
Please continue to monitor N Cas 95 closely, using the AAVSO revised "b" and
"d" preliminary charts distributed with AAVSO Alert Notice 218, and email,
telephone, or fax your observations to AAVSO Headquarters.
2138+43 SS CYGNI IN OUTBURST AND UNDER OBSERVATION BY RXTE AND EUVE
The dwarf nova cataclysmic variable SS Cyg is undergoing a narrow outburst at
present. Astronomers (see AAVSO Alert Notice 229) have observed it with the
RXTE satellite for 2 days, and will be observing it for another 3 days when it
is back down near minimum. The astronomers have also been observing SS Cyg
with the EUVE satellite since the current outburst started on October 8, and
will continue to observe throughout the outburst.
Our sincere thanks to the 57 observers from around the world who have reported
262 visual and CCD observations of SS Cyg by email, phone, or fax since October
1. Your observations triggered the satellite observations and have enabled us
to provide the astronomers with detailed, up-to-the-minute information crucial
to the successful timing of the satellite observations.
It is extremely important that we know the behavior of SS Cyg as it declines
from this outburst, as we are continuing to keep the astronomers informed so
they can schedule RXTE to observe SS Cyg when it reaches magnitude 11.5. Please
monitor SS Cyg closely and continue to report your observations to AAVSO
Headquarters on a daily basis. Observers with CCD are especially urged to
monitor SS Cyg very closely - on the order of every 5 minutes for 30 to 45
minutes twice a night, once at the beginning of the night and once at the end -
as it approaches magnitude 11.5, and report your observations promptly.
0207-63 WX HYDRI AND 2138+43 SS CYGNI OBSERVED WITH HUBBLE SPACE TELESCOPE
Astronomers using the Hubble Space Telescope (HST) successfully observed the
dwarf novae WX Hyi and SS Cyg in quiescence, as they had hoped to do (see AAVSO
Alert Notice 229). Your observations were very valuable in allowing us to
determine the state of these stars prior to and during their observing runs.
WX Hyi is currently declining from a superoutburst; we extend our thanks to our
observers from South Africa and Australia for their most valuable reports on
this star's behavior.
Additional observations with HST are planned for the coming weeks. Please
continue to monitor WX Hyi and SS Cyg closely and keep us informed of their
status.
CHARTS AVAILABLE ON AAVSO FTP SITE
Chart links are obsolete; 11/2013 create charts using VSP at http://www.aavso.org/vsp
Electronic copies of the AAVSO chart of NGC 5308, the excerpts from the AAVSO
and Vickers Atlases showing NGC 5308, and the light curve of N Cas 95 mentioned
in this Alert Notice are available from our FTP site:
ftp.aavso.org (198.116.78.2), in /pub/alert230
These materials may also be accessed through our Web site at the following
address:
http://www.aavso.org
The answering machine at AAVSO Headquarters is on nights and weekends for your
convenience. Please call our charge-free number (800-642-3883) to report your
observations. If you are cut off when you telephone in your observations,
please wait a few minutes and call back to complete your call. We have learned
that if someone calls to leave observations on the answering machine and while
they are speaking someone else calls, the first person may be cut off. We
also encourage observers to send observations by fax to 617-354-0665 or by
e-mail through the Internet to observations@aavso.org. We would appreciate it
very much if you would report your observations in Universal Time.
Many thanks for your valuable astronomical contributions and your efforts.
Good observing!
Janet A. Mattei
Director
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