COMMISSION 27 AND 42 OF THE IAU
              INFORMATION BULLETIN ON VARIABLE STARS
                          Number 3820

                                                  Konkoly Observatory
                                                  Budapest
                                                  21 December 1992

                                                  HU ISSN 0374 - 0676


              Theta^2 Sgr, NOT AN Am STAR

   Owing to an undetected punch-card error during the
preparation of the 1964 version of the Bright Star
Catalogue the spectral type that was intended for HR 6724
(Hoffleit 1950) was inadvertently attributed to HR 7624,
Theta^2 Sgr. The most recent class for Theta^2 Sgr is A4/5IV
(Houk 1982). Regrettably this refutes Anders'(1992) conclusion
that his discovery of the variability of this star
constitutes an unusual discovery of the variability of an
Am type star. As he indicated, there are no previous
discoveries of the variability of Theta^2 Sgr. Anders' "target
star", HR 7631 was originally reported by Corben et al.
(1972) as varying by 0.07V, but they did not indicate any
specific comparison star, nor the time-span of their
observations. Superimposed on Anders' steady increase in
the difference between HR 7631 and 7624 a 0.07V flare is
indicated, the same range as previously reported for HR
7631 = NSV 12655, based on only six observations. Table I
gives data for these stars as listed in the current tape
version of the Bright Star Catalogue (BS5).


    Table I. Potential Variables and Comparison Star

HR      HD    RA (1950) Dec     M_V    Sp        Remark

7624  189118  19h56m.6-34d50'   5.30   A4/5IV    VAR
7631  189245  19 57 .1-33d50'   5.66   F7V       NSV 12655
7585  188158  19 51 .9-33d11'   6.46   K2/3III   Comparison

    A comparison of the differences between the
photoelectric V magnitudes and those read from Anders'
Figures 1a and 1b is given in Table II, showing reasonably
consistent results. It is intriguing that the flare of Theta^2
Sgr has the same amplitude as that reported for HR 7631.
Both stars need to be extensively monitored against
comparison sources that have not yet been suspected of
variability.


           Table II. Comparisons

    HR       BS5    Anders            "Flare" Amp
              V       V                    V

7631-7585   -0.80   -0.88                 0.07
7631-7624   +0.36   +0.03 to +0.28        0.07


    The star previously classified Am, HR 6724, has been
variously classified, as shown in Table III. Could this be a
spectrum variable?


               Table III. HR 6724

Sp.        Source

A5         Cannon, HD 164584, 1922
A8s        Adams et al, Ap.J., 81, 187, 1935.
Am, A8+F4  Hoffleit, "Dually classified", Harvard Ann., 119, 1950.
F0II       Herbig, in M.F. Walker, Ap.J., 125, p. 636, 1957.
F5II       Bidelman, Idem, p. 636.
F3III      Morgan and Abt, A.J., 77, 36, 1972.
F5II-III   Malaroda, A.J., 80, 637, 1975.
F2/3II/III Houk, Michigan Sp. Cat., 3, 1982.

   I wish to thank Dr. W. Bidelman for calling my
attention to the error in attributing class An to Theta^2 Sgr.


                                    Dorrit Hoffleit
                                    Department of Astronomy
                                    Yale University
                                    New Haven, CT 06511, USA



References:

Anders, G.J. 1992, I.B.V.S. No. 3768.
Corben, P. M., Carter, B.S., Banfiels, R. M., and Harvey, G. M. 1972, Mon.
      Notices Ast. Soc. S. Africa, 31, 7. [BIBCODE 1972MNSSA..31....7C ]
Hoffleit, D. 1950, Ann. Harvard Coll. Obs., 119, No. 1. [BIBCODE 1953AnHar.119....1H ]
Houk, N. 1982, Michigan Spectral Catalogue, Vol. 3, p. 291. [BIBCODE 1982mcts.book.....H ]


Erratum:
In I.B.V.S. 3768, first ref., for Ap.J. read Ap.J. Supp.