COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2817

                                         Konkoly Observatory
                                         Budapest
                                         11 November 1985

                                         HU ISSN 0374 - 0676


         BRUN 276, A YOUNG STAR BELOW THE MAIN-SEQUENCE?

 Brun 276 is a faint object in the vicinity of the Orion Nebula. We have
secured a MEPSICRON (Firmani et al., 1984) spectrum of B276 with the 2.1 m
telescope at San Pedro Martir Observatory of the University of Mexico, on
October 17, 1985 (U.T.). This spectrum covers the spectral range lambda-lambda 
3700 - 6900 A (1024 pixels); although it is under-exposed (V >~ 18.0 during the 
observation) and it is also contaminated by the nebula, it is possible to see 
stellar lines of calcium II (H and K) and hydrogen Balmer lines in emission 
(probably Hbeta is as strong as Halpha). Altogether the spectrum indicates 
T Tauri star, possibly of early K-type.
Walker (1969) gives V=18.04, B-V=+0.73 and U-B=-0.99. Haro (1976) gives 
I >~ 17. These values indicate that B276 is neither heavily obscured by
interstellar extinction, nor with a large infrared-excess, probably. If we
use a mild infrared colour excess of a T Tauri star (Mendoza, 1966) for B276,
then we derive Mbol =~ 9. The (B-V) colour-index and the spectral type yield
Te=~ 4800 K. If these values are not very wrong, then B276 lies below the
main-sequence, at least one magnitude.
  We conclude that B276 is a pre-main-sequence star embedded in the Orion
Nebula, which lies below the main sequence because

  1) It is a variable star (Brun, 1935)
  2) It has a variable Halpha -emission line (Haro, 1976, 1980; Parsamian and
   Chavira, 1982)
  3) The spectrum is of a T Tauri star
  4) The combined observational data locates it below the main sequence, most
    likely.



          E.E MENDOZA, C. FIRMANI, and G. HARO
            Instituto de Astronomia
          Universidad Nacional Autonoma de Mexico
            Ap. Postal 20 - 158
            01000 Mexico D.F.

References:

Brun, A., 1935, Pub. Obs. Lyon, Vol. 1, No. 12
Firmani, C., Gutierrez, L., Ruiz, E., Bisiacchi, G.F., Salas, L., 
  Paresce, F., Carlson, C.W., Lampston, M., 1984, Astron. Astrophys. 134, 251 [BIBCODE 1984A&A...134..251F ]
Haro, G., 1976, Bol. Inst. Tonantzintla 2, 3 [BIBCODE 1976BITon...2....3H ]
Haro, G., 1980, Dissertation, Colegio Nacional, Mexico, D.F.
Mendoza, E.E., 1966, Ap. J. 143, 1010 [BIBCODE 1966ApJ...143.1010M ]
Parsamian, E.S., and Chavira, E., 1982, Bol. Inst. Tonantzintla, 3, 69 [BIBCODE 1982BITon...3...69P ]
Walker, M.F., 1969, Ap. J. 155, 447 [BIBCODE 1969ApJ...155..447W ]