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Alert Notice 278

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                AAVSO ALERT NOTICE 278 (November 20, 2000)

1017-49  V383 VELORUM (NSV 4834) = NEW DWARF NOVA

We have been informed by AAVSO member and observer David B. Williams,
Indianapolis, IN, that he has determined on Harvard photographic patrol plates
that the suspected variable star NSV 4834 is a previously-unrecognized dwarf
nova with an estimated photographic (blue) magnitude range of 12.7 - 17 and a
characteristic outburst cycle of 50-60 days.

The official name V383 Velorum was assigned by N. Samus, editor of the General
Catalogue of Variable Stars.

Williams reports an improved position for V383 Vel of

        R.A. = 10h 19m 40.6s   Decl. = -49 degrees 34' 15"  (1950),

which precesses to

        R.A. = 10h 21m 41.2s   Decl. = -49 degrees 49' 25"  (2000).

Observers are urged to follow this newly-classified variable closely
throughout its observing season, which is just beginning.

Variability of this star was first reported in the 1930s by W. J. Luyten,
who found the star at photographic magnitudes 12.5 and <15.5 on a pair
of Harvard plates during the Bruce Proper Motion Survey of the southern sky.
No additional observations were made, and no finding chart was published.
Recently, Williams has begun to identify and determine accurate positions
for Luyten's variables on the discovery plates in the Harvard Observatory
archive (see "Unfinished Business: Luyten's Harvard Variables - I" in the
recent AAVSO Journal, Vol. 28, No.1, page 12 (2000).)  He has also observed
on the Harvard patrol plates some of the brighter Luyten variables to
determine types and periods.  This additional step led to the recognition of
V383 Vel's dwarf nova characteristics.  Williams found more than 20 maxima
dating back to 1899.  A report on these observations is being prepared for
the Information Bulletin on Variable Stars.

Accompanying are AAVSO preliminary 'd' and 'e+' scale charts of V383 Vel
prepared by C. Scovil, A. Price, and K. Malatesta, AAVSO Headquarters.  Please
use them to observe V383 Vel.  The charts have a letter sequence for the
fainter stars, which will be measured as soon as possible. As a reminder on
the use of letter sequences, first, find the two comparison stars which bracket
the variable and divide the difference between them into 10 steps.  Then,
estimate the brightness of the variable using these 10 steps.  For example, if
the variable is fainter than d and brighter than e, and is a little closer to
e in brightness, write your estimate as d7v3e.

We ask you to use the letter sequence to make your estimate and report the
letter estimate.  However, in order to give us an approximate idea of the
star's behavior, we ask that you also give a numerical magnitude based on the
USNO-A2.0 Catalog values given below:

                        a - 116        f - 137
                        b - 124        g - 144
                        c - 128        h - 150
                        d - 130        m - 157
                        e - 134        n - 162

Thus, the example letter estimate above would also be reported as magnitude

NUMERICAL MAGNITUDE when you report your observations to AAVSO Headquarters.
The USNO-based numerical magnitude will give us a rough idea of what the star
is doing, and the letter estimate will allow us to calculate a final numerical
magnitude for the AAVSO International Database once the sequence has been


Electronic copies of the charts of V383 Vel 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:

             ftp.aavso.org (, in /alerts/alert278

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.

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Janet A. Mattei

Elizabeth O. Waagen
Senior Technical Assistant