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Alert Notice 283

                25 Birch Street, Cambridge, MA 02138 USA
                Tel. 617-354-0484       Fax 617-354-0665

                AAVSO ALERT NOTICE 283 (May 21, 2001)


The SU Ursae Majoris-type (WZ Sge subclass) dwarf nova AL Comae Berenices is
undergoing a rare superoutburst, and is currently at visual magnitude 12.6,
up from its minimum magnitude of around 20.

The present outburst of AL Com is only the fourth reported since 1967, when
coverage of this star begins in the AAVSO International Database.  The last
reported outburst of AL Com was a superoutburst and occurred April 5, 1995,
and lasted until May 3 (see AAVSO Alert Notices 206 and 207), with AL Com
reaching magnitude 12.2.  The superoutburst light curve included a decline,
standstill, decline, and then fast drop and recovery before returning
to minimum, as discussed in Alert Notices 206 and 207.

Previous outbursts were reported in April 1974 (regular outburst, lasting
4 days and reaching magnitude 14.0) and March 1975 (superoutburst, lasting
30 days and reaching magnitude 12.8).

Articles on the 1995 superoutburst of AL Com include Pych and Olech, Acta
Atronomica, 45, 385 (1995); Howell et al., Astronomical Journal, 111, 6,
2367 (1996), which includes AAVSO collaboration; and Nogami et al.,
Astrophysical Journal, 490, 840 (1997).

AL Com is also a member of the class of objects known as TOADs (Tremendous
Amplitude Outburst Dwarf novae), which are low-mass transfer systems that
have superoutbursts at intervals of years or decades and sometimes have
a brief fading and recovery before returning to minimum.

Both visual and, particularly, CCD observers are urged to search for
superhumps (small-amplitude periodic oscillations), making observations
every 5 minutes for as long as possible during the night and recording the
time to four decimal places while this star is in superoutburst.  The CCD
observers are also urged to monitor AL Com in the (V) and (I) bands for

The following observations have been reported to the AAVSO:
May 17.8979 UT, <15.4, M. Reszelski, Szamotuly, Poland;
18.2812, <13.9, P. Abbott, Leduc, Alberta, Canada;
18.8700, 12.1, J. Gunther, St. Trinit, France;
18.9021, 12.8, C. Jones, Laindon, Essex, England;
18.9700, 12.9, H. McGee, West Clandon, Surrey, England;
19.1645, 12.8, M. Simonsen, Macomb, MI;
19.2382, 12.4, T. Burrows, Novato, CA;
19.8714, 12.7, Reszelski;
19.8990, 12.7, P. Schmeer, Bischmisheim, Germany;
19.9097, 12.5, W. Vollmann, Vienna, Austria;
19.9276, 12.9 CCDR, M. Fiaschi, Padova, Italy;
19.9334, 13.0 CCD, R. Diethelm, Rodersdorf, Switzerland;
19.9860, 12.7, G. Poyner, Birmingham, West Midlands, England;
20.1041, 12.8, R. Berg, Crown Point, IN;
20.1617, 12.8, Simonsen;
20.2167, 13.0, J. Van Poucker, Eastpointe, MI;
20.8791, 12.5, Reszelski;
20.8958, 13.0, P. Dubovsky, Podbiel, Slovakia;
20.9169, 12.6, Schmeer;
21.0750, 13.0 CCDV, A. Price, Waltham, MA;
21.3061, 12.6, Abbott;

Accompanying is an AAVSO Preliminary 'e' scale chart of AL Com (sequence
revised 21 May 2001) prepared by C. Scovil and K. Malatesta, AAVSO
Headquarters.  Please use this chart to observe AL Com and report your
observations to AAVSO Headquarters, making sure to indicate which comparison
star(s) you used.  For CCD observers we have also prepared a CCD chart that is
on our website.


Nova Aql 2001 (see AAVSO Alert Notice 282 and AAVSO News Flash 785) is fading
rapidly, as the following observations reported to the AAVSO indicate:

May 19.8958 UT, 13.0, W. Hasubick, Buchloe, Germany;
19.9512, 13.31 CCDV, G. Favero, Padova, Italy;
19.9742, 13.32 CCDV, Favero;
19.9900, 14.0:, G. Krisch, Bockenem, Germany;
19.9929, <13.3, P. Chevally, Geneva, Switzerland;
20.0277, 13.8, H. Hautecler, Boutersem, Belgium;
20.0847, 13.2 CCDV, M. Fiaschi, Padova, Italy;
20.2118, <12.4, M. Komorous, London, Ontario, Canada;
20.2617, 13.8:, M. Simonsen, Macomb, MI;
20.2776, <13.3, S. Wolfe, Upper Arlington, OH;
20.3138, 13.7, P. Dombrowski, Glastonbury, CT;
20.3201, 12.10 CCDR, S. O'Connor, Montreal North, Quebec, Canada;
20.3229, 14.0:, J. Van Poucker, Eastpointe, MI;
20.3250, 13.59 CCDV, O'Connor;
20.4325, 14.1:, M. Linnolt, Honolulu, HI;
20.9805, 13.7, P. Dubovsky, Podbiel, Slovakia;
21.1124, 13.6 CCDV, A. Price, Waltham, MA;
21.3533, 13.8, P. Abbott, Leduc, Alberta, Canada;

The nova has faded below the limit of the AAVSO 'd' scale Preliminary chart
issued with Alert Notice 282.  An AAVSO 'f' scale Preliminary chart is being
prepared by G. Hawkins and K. Malatesta, AAVSO Headquarters, that extends the
comparison star sequence for this nova.  This chart will be posted on the
AAVSO website when it is ready.  Please use it to observe N Aql 01 and report
your observations to AAVSO Headquarters, indicating which comparison star(s)
you used.  As the nova fades, CCD observers are urged to follow it as long
as possible.


Electronic copies of the charts for AL Com and N Aql 01 mentioned in this
Alert Notice are available through our web site at the following address:


They may also be obtained directly from our FTP site:


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

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Janet A. Mattei

Elizabeth O. Waagen
Senior Technical Assistant

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484