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E. R. Smith (Whitman Coll. & Maria Mitchell Obs.), V. Strelnitski (Maria Mitchell Obs.)
We report on the first attempt at multicolor photometry of the close binary TW CrB. U,B,I relative CCD photometry was carried out over six consecutive nights in June 2003 using the 31-in reflector of Lowell Obs. in Flagstaff, AZ. Combining our results with the V photometry of Zhang and Zhang (2003), we conclude that the depth of both the primary and the secondary minima is similar in B, V, and I: 0.88 +/- 0.04 mag for the primary minimum and 0.70 +/- 0.03 mag for the secondary. However, both minima are deeper in U: 0.96 +/- 0.06 and 0.87 +/- 0.04, respectively. We note a considerable "bluing" of the system around the primary minimum, lasting 1-2 hours, during which the U-B and, possibly, also the B-I color index decreases by 0.2-0.3 mag. The relatively deep secondary minimum in U and the "bluing" in U near the primary minimum may be the result of a hot spot on the inner extremity of the primary component, possibly due to infall of matter from the secondary. Our observations also show variations from cycle to cycle in U, on the order of 0.1 mag, which may be due to instability of the hot spot. An attempt at absolute UBVRI photometry indicates a considerable ultraviolet excess making it impossible to ascribe a single spectral class to this system, as was previously attempted. This project was supported by the NSF/REU grant AST-0097694 and the Nantucket Maria Mitchell Association.
The author(s) of this abstract have provided an email address for comments about the abstract: smither@whitman.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.