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          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 244 (March 13, 1998)


1140+48 SUPERNOVA 1998S IN NGC 3877

We have been informed by the Central Bureau for Astronomical Telegrams
(IAU Circular 6829) that W.-d. Li, University of California at Berkeley,
reports that C. Li, Beijing Astronomical Observatory (BAO), reports that
Zhou Wan discovered a supernova in NGC 3877 on Mar 2.68 UT (date as
corrected in IAU Circular 6835) at unfiltered CCD magnitude 15.2 on CCD
images obtained with the 0.60-m BAO telescope of the BAO Supernova Survey.
No object was present on images taken on Feb. 23.7 (IAU Circular 6835).

The discovery was confirmed by the Lick Supernova Survey, using the Lick
Observatory Katzman Automatic Imaging Telescope, and showed the supernova
had brightened to unfiltered CCD magnitude of about 13.5 by Mar. 4.3 UT.
The supernova was not present in images taken using this telescope prior
to March 3 (IAU Circular 6829).

D. D. Balam, University of Victoria, reported the supernova to be at 13.6"
west and 46"  south of the nucleus of NGC 3877, with the following precise
position (IAU Circular 6831):

       R.A. = 11h 46m 06.18s    Dec. = +47 degrees 28' 55.5"   (2000)

Spectroscopic observations confirming the object as a supernova have been
reported as follows:

- A. V. Filippenko and E. C. Moran, University of California at Berkeley,
obtained a very-high-resolution echelle spectrogram with the Keck-1 telescope
on Mar 4 UT, which suggested the supernova was Type-II (IAU Circular 6829).

- P. Garnavich, S. Jha, and R. Kirshner, Harvard-Smithsonian Center for
Astrophysics, report that J. Huchra used the 1.5-m Tillinghast telescope to
obtain a spectrum on Mar 5.3 UT that showed SN 1998S to be an unusual
Type-IIn (narrow-lined) supernova.  They also report that features seen in
SN 1998S are identical to SN 1983K, which was discovered two weeks before
maximum light and reached a maximum of B magnitude 12.4 (IAU Circular 6832).

Observations of SN 1998S reported to the AAVSO and the Central Bureau for
Astronomical Telegrams include:

Mar 2.70 UT, 16.0: V (derived from unfiltered CCD image), K. Kawakami, Kochi
University, Japan, (reported by A. Nakamura, Kuma, Ehime, Japan, IAU Circular
6831); 5.844, 13.6 CCD, J.-C. Merlin, Le Creusot, France (IAU Circular 6831);
7.32, 13.0, R. Modic, Richmond Heights, OH; 7.69, 12.6, S Yoshida, Waseda
University, Japan (IAU Circular 6835); 8.085, 12.8, Modic; 9.91, 12.5 CCD,
J.-C. Merlin, Le Creusot, France, GSC sequence (IAU Circular 6835); 9.947,
12.9, G. Poyner, Birmingham, England (GSC sequence); 10.017, 12.2, B. Granslo,
Fjellhamar, Norway; 10.044, 12.2, Granslo; 10.098, 12.3, Granslo; 10.181,
12.8, Schmeer; 10.18, 12.8, P. Schmeer, Bischmisheim, Germany (IAU Circular
6835); 11.79, 12.0, K. Hornoch, Lelekovice, Czech Republic, GSC sequence (IAU
Circular 6838); 11.83, 12.0, L. Brat, Brno, Czech Republic (IAU Circular 6838);
11.83, 12.3, L. Novak, Brno, Czech Republic (IAU Circular 6838); 11.844, 12.2,
Poyner; 11.866, 12.3, Poyner; 12.132, 12.2, Poyner; 12.75, 12.5, L. Kiss,
Szeged, Hungary; 13.361, 12.4, Modic.

Accompanying is an 'e' scale chart of NGC 3877 showing SN 1998S, prepared by
C. Scovil using Tycho Catalog and Guide Star Catalog comparison star
magnitudes.  Please use this chart to observe 1140+48 SN 1998S, and report
your observations to the AAVSO.  Be sure to indicate which comparison stars
you used to make your estimates.

Congratulations to Zhou Wan on his discovery!


FADING OF 1921+50 CH CYGNI

Observations submitted to the AAVSO International Database in recent months
indicate that the symbiotic variable CH Cyg, which had been recovering from
its unprecedentedly faint minimum of June-July 1996 (see AAVSO Alert Notice
222), is fading again.

CH Cyg had brightened from visual magnitude approximately 10.3 in July 1996
to 8.8 by November 1997, when it began to fade again.  Currently it is at
visual magnitude approximately 9.7.

Accompanying is a light curve of 5-day means of the AAVSO observations of
CH Cyg from January 1993 to date.  This light curve includes the 1996 minimum,
and shows some aspects of the multiperiodic nature of this interesting
variable (see Karovska, M., and Mattei, J. A., 1992, Journ. AAVSO, 21, 1, 23).

247 observers worldwide contributed the 10,475 observations used to generate
this light curve; we acknowledge with thanks each observer's valuable
contribution.

Accompanying is an AAVSO 'c' scale chart for CH Cyg prepared by C. Scovil.
Observers are urged to use this chart to monitor CH Cyg closely, and to inform
us by phone, fax, or email of its behavior.  Be sure to indicate which
comparison stars you used to make each estimate.


CHARTS AVAILABLE ON AAVSO FTP SITE

Electronic copies of the AAVSO charts of SN 1998S and CH Cyg and the light
curve of CH Cyg mentioned in this Alert Notice are available from our FTP site:

           ftp.aavso.org (198.116.78.2), in /pub/alerts/alert244

In addition, the charts may be accessed from the charts page of our FTP site:

          ftp.aavso.org (198.116.78.2), in /pub/charts/uma/sn1998s/ and
                                        in /pub/charts/cyg/ch_cyg/

The charts, along with the light curve of CH Cyg, 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.  We also encourage observers to send
observations by fax to 617-354-0665 or by e-mail through the Internet to
observations@aavso.org.

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Janet A. Mattei
Director

Keywords:
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484