COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3654

                                                  Konkoly Observatory
                                                  Budapest
                                                  29 August 1991

                                                  HU ISSN 0374 - 0676


               V3821 Sgr AND A NEARBY CARBON STAR


It has been shown that large errors do exist in the published positions of some
Variable stars (Carlos Lopez, 1989). W. Bidelman of the Warner and Swasey
Observatory pointed out that a carbon star No. 4007 in Stephenson's catalog
(1989) had published positions that were very close to the variable V3821 Sgr.
A question therefore arose as to whether or not these were one and the same
star. The variable is listed in the fourth edition of The General Catalogue of
Variable Stars as an eclipsing binary of the Algol type. This star was
discovered by Dorrit Hoffleit at Harvard around 1935.



    Table I. Nor Positions for Carbon Star No. 4007
          and Several Variable Stars.

Star                  (1950)                    Remarks

4007        18 23 27.9829 -22 06 02.535     vis. mag 10.0
                  27.7           07
V3821 Sgr   18 23 22.5560 -22 06 10.304     13.7-14.6 pg, EA
                  24.            06.2       IBVS 660 chart 75c.
V2548 Sgr   18 23 26.5685 -22 04 03.761     14.5-16.4 pg, SR 159d.
                  28             04.1       IBVS 660 chart 82.
NSV 10781   18 23 07.6399 -22 18 18.519     12.8-13.9 pg
                  09             08.3       IBVS 660 chart 75a.
NSV 10782   18 23 10.7336 -22 07 34.840     14.0-14.5 pg
                  11             07.5       IBVS 660 chart 75b.
NSV 10784   18 23 17.2117 -22 13 55.811     14.4-15.1 pg
                  18             14.8       IBVS 660 chart 79.


                            [FIGURE 1]

 Finder Chart, Approx. 10' x 10'  North at top. R. Carbon star 4007
 a. NSV 10781   b. NSV 10782   c. V3821 Sgr   d. V2548 Sgr


  Measurements by Christopher Predom and Robert
DeMartino on a yellow plate confirmed the position of the carbon star and
showed another star in the position of the variable, 76 arc seconds to its
west. The identity of the carbon star was established from a marked finder
chart supplied by D.J. MacConnell, one of the original investigators of this
object. Dr. Hoffleit then checked her original records and visited Harvard
Observatory in order to ascertain which star was actually the variable. The
carbon star and the variable are in fact two different stars. The plates she
had surveyed showed no significant variation of the carbon star. On
examination of 230 Harvard plates taken between 1924 and 1951, and another
130 plates at the Maria Mitchell Observatory taken between 1957 and 1962, Dr.
Hoffleit had found a total of 16 minima from which she determined the following
provisional light element:

        JD(min) = 2427239.548 + 0.7503986 n

Many more plates are now available at the Maria Mitchell Observatory. Under
the direction of Dr. E.P. Belserene, a summer student will determine a more
definitive period and light curve.

The new positions we have recorded for the variable, the carbon star, and a few
other nearby variables are shown in Table I. The first line is the new
position, the second shows the old coordinates.


                    CHRISTOPHER PREDOM
                    ROBERT DeMARTINO
                    Astronomical Society of New Haven, Inc.

References:

Hansen, O.L. and Blanco, V.M. 1975, Ast. Jour., 80,
   1011, star 20482. [BIBCODE 1975AJ.....80.1011H ]
Hoffleit, D. 1972, Inform. Bull. Var. Stars, No. 660.
Hoffleit, D. et al. 1991, Journ. Amer. Assoc. Var.
   Star Obs. 3, No. 2.
Lopez, C.E. 1989, Journ. Amer. Assoc. Var. Star Obs.
   18, No. 2.
Lopez, C.E., Girard, T.M. 1990, Publications of the
   Astronomical Society of the Pacific, 102, No. 655. [BIBCODE 1990PASP..102.1018L ]
Stephenson, C.B. 1989, Pub. Warner and Swasey Obs. 3,
   No. 2. [BIBCODE 1989PW&SO...3....2S ]