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Alert Notice 281

          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 281 (May 11, 2001)

0829+28 SUPERNOVA 2001bg IN NGC 2608 (CANCER)

We have been informed by the Central Bureau for Astronomical Telegrams
(IAU Circular 7621) that Guy Hurst, Basingstoke, England, reports that Tom
Boles, Coddenham, England, discovered an apparent supernova on images
taken May 8.943 UT (limiting magnitude about 18) and May 9.9 UT (poor
conditions) at CCD magnitude about 14, using a 0.36-m Schmidt-Cassegrain
telescope and while participating in the U.K. Nova/Supernova Patrol.  The
object was confirmed at CCD magnitude about 14 by H. Kerner, Fassberg,
Germany, who obtained an image at the request of Hurst on May 9.884 UT
with a 0.15-m reflector.

Nothing was seen at the location of the supernova down to CCD magnitude
~19 on a Patrol master image taken on January 13, 2000, or down to
photographic red and blue magnitudes ~20 on Palomar Sky Survey images from
November 1989 and March 1990, respectively.

SN 2001bg is located 22" east and 19" south of the center of NGC 2608, at
the coordinates:

       R.A. = 08h 35m 18.86s Decl. = +28 degrees 28' 05.8"  (2000)

Accompanying is an AAVSO Preliminary 'e' scale Supernova Search chart of
NGC 2608 showing the location of SN 2001bg.  Please use this chart to
observe the supernova, and report your observations of 0829+28 SN 2001BG
to AAVSO Headquarters, making sure to indicate which comparison star(s)
you used.

Congratulations to Tom Boles on his latest discovery!


REMINDER - OBSERVATIONS REQUESTED FOR 0803+62 SU UMA BEING OBSERVED WITH
RXTE

As announced in AAVSO News Flash No. 772, a colleague from the University
of Leicester has been awarded time on the Rossi X-Ray Timing Explorer
(RXTE) satellite to observe the dwarf nova SU UMa.  RXTE will observe SU
UMa regularly through June.

Please keep a close eye on SU UMa and report your observations regularly
to the AAVSO, as our colleague is checking the online Quick-Look File
often. We are also periodically sending him data files so that he may
correlate his x-ray data with the AAVSO optical data.  AAVSO charts for SU
UMa may be found on the AAVSO website (details below) or obtained from
AAVSO Headquarters.


POSSIBLE PLANETARY TRANSITS OF 2248-14 IL AQUARII = GLIESE 876

AAVSO member and observer Frederick West, Hanover, PA, gave a presentation
at the 89th Annual Meeting of the AAVSO in October 2000 in which he
suggested that amateur astronomers monitor the variable star IL Aqr =
Gliese 876 in order to observe transits by either or both of its
recently-discovered Jovian planets. [The text of his presentation, with
calculations, will appear in June as a Letter to the Editor in Journal
AAVSO, Vol. 29, No. 2.]

High-precision (CCD or photoelectric photometry) transit observations
could improve our information about the radii, mass, density, and orbital
elements of both Gliese 876 and its planets and about the limb darkening
of the star.  The first window of opportunity to look for these transits
is May 16 - 27, 2001.

Gliese 876 = IL Aqr is a red dwarf star (RA = 22h 53m 20s, Decl. = -14deg
13.2min (2000), M4V, range 10.15-10.19 V, (B-V)=1.58, (R-I)=1.22),
possible periods = 20.2 and 28.7 days).  Geoffrey Marcy, University of
California at Berkeley, and his colleagues (Marcy et al. 1998; Cowen 2001)
found two giant planets orbiting Gliese 876:  Gliese 876b and Gliese 876c.  
Using the information in these references and in Delfosse et al. (1998),
MacRobert (2001), Burrows et al. (1997), Sterne (1960), and West (1996),
West calculated approximate dates and times of predicted transits of
Gliese 876 by its planets; they are given in the table below.

Uncertainties in the orbital elements make the times uncertain by several
days, so Gliese 876 should be monitored for transits during "opportunity
windows" lasting ten days or longer.  These windows will occur on the same
days of the calendar year for many years.  Gliese 876 rises at sidereal
time 17:42 and sets at 4:04 for an observer at 40 N latitude. Thus,
morning observations are feasible from late May to September and evening
observations September to late January.  For Gliese 876b a transit may
last as long as 3.53 hours and have an amplitude as much as 0.20
magnitude. For Gliese 876c a transit could last as long as 2.2 hours.  If
the planets simultaneously transit, Gliese 876 could be dimmed by as much
as 0.45 magnitude.

 Transit Number    ----Predicted Time of Transit----    Opportunity Window
  876b   876c          JD             Date and UT
           58      2452050.8     2001 May  21  07:12       2001 May  16-27
   29              2452079.97    2001 Jun. 19  11:17       2001 Jun. 14-26
           59      2452080.9     2001 Jun. 20  09:36       2001 Jun. 14-26
           60      2452111.0     2001 Jul. 20  12:00       2001 Jul. 15-26
   30              2452140.97    2001 Aug. 19  11:17       2001 Aug. 14-25
           61      2452141.1     2001 Aug. 19  14:24       2001 Aug. 14-25
           62      2452171.2     2001 Sep. 18  16:48       2001 Sep. 13-24
           63      2452201.3     2001 Oct. 18  19:12       2001 Oct. 13-25
   31              2452201.97    2001 Oct. 19  11:17       2001 Oct. 13-25
           64      2452231.4     2001 Nov. 17  21:36       2001 Nov. 12-23
           65      2452261.5     2001 Dec. 18  00:00       2001 Dec. 12-24
   32              2452262.97    2001 Dec. 19  11:17       2001 Dec. 12-24
           66      2452291.6     2002 Jan. 17  02:24       2002 Jan. 11-23

Observations should be made every 5 minutes.  Observers should have access
to an accurate time source and record the time of their observations to
the nearest second, if possible.  Accompanying is an AAVSO Preliminary 'd'
scale chart of Gliese 876 with comparison stars suitable for CCD or
photoelectric observing.  Please use this chart to make your observations
and REPORT ALL OBSERVATIONS DIRECTLY TO Dr. Frederick West, 520 Diller
Road, Hanover, PA 17331-4805, USA. (Do not report observations to the
AAVSO.)

References
Burrows, A., et al. 1997, in: Planets Beyond the Solar System and The Next
  Generation of Space Missions (D.R. Soderblom,ed.), Ast. Soc. Pacific Conf.
  Series, Vol. 119, pp. 9-17.
Cowen, R. 2001, Science News, 159, No. 2, 22.
Delfosse, X., et al. 1998. Astron. and Astrophys. Lett., 338, L67.
Marcy, G.W., et al. 1998, Astrophys. J. Lett., 505, L147.
MacRobert, A. 2001, Sky & Telescope, 101, No. 4, 20.
Sterne, T.E. 1960, An Introduction to Celestial Mechanics, Interscience,
   New York, pp. 8-14.
Weis, E.W. 1994, Astron. J., 107, 1135.
West, F.R. 1996, J. Amer. Assoc. Var. Star Obs., 24, 19.
West, F.R. 1999, J. Amer. Assoc. Var. Star Obs., 27, 77.


CHARTS AVAILABLE ON AAVSO WEB AND FTP SITES

Electronic copies of the charts for SN 2001bg, SU UMa, and Gliese 876
mentioned in this Alert Notice are available through our web site at the
following address:

                         http://www.aavso.org

They may also be obtained directly from our FTP site:

             ftp.aavso.org (198.116.78.2), in /alerts/alert281

The answering machine at AAVSO Headquarters is on nights and weekends for
your convenience. Please call our charge-free number (888-802-STAR =
888-802-7827) 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.

If you need to change the email address this Alert Notice is sent to, or
if you would like to stop receiving the Alert Notice by email, please
visit the following URL:
                    http://www.aavso.org/mailinglists.stm

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Janet A. Mattei
Director

Elizabeth O. Waagen
Senior Technical Assistant

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