AAS Meeting #193 - Austin, Texas, January 1999
Session 102. Binary Stars
Display, Saturday, January 9, 1999, 9:20am-4:00pm, Exhibit Hall 1

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[102.09] CCD Photometry of MWC349A Separated from Its Companion

K. Billings (Columbia U. \& Maria Mitchell Obs.), R. Jorgenson (U. Puget Sound \& Maria Mitchell Obs.)

The variable emission-line star MWC349 is a unique source of maser and laser emission in hydrogen recombination lines arising in an edge-on circumstellar disk. Precise information on the star's optical variability is interesting by itself and for its possible correlations with the variations of the maser and laser emission. However, the emission-line star proper (MWC349A) has a close (2.4 arcsec) companion (MWC349B) that contaminates the results of optical photometry. With one exception, all photometry on this system has previously been done on the two components together. If the second component is not variable, the additional flux due to this component would reduce the amplitude of the observed variations of MWC349A. We have attempted to do BVRI photometry separately on the two stars using CCD images obtained with the 31-inch telescope of the NURO observatory in Flagstaff, AZ, and the IRAF/DAOPHOT package. DAOPHOT creates a model of the Point Spread Function for a field image and then fits this model to individual star images (including the stars in groups with heavily overlapping images) to find instrumental magnitudes of separate stars. In this way, we have obtained the difference in B, V, R and I magnitudes of MWC349A and B for several observing sessions. We use these results, together with the previous results of combine (A+B) photometry, to assess the actual amplitudes of variability of MWC349A. We show that in the case of the B and V bands the amplitude of variations changes drastically, requiring future photometry to be done separately on each component. For the R and I bands, where MWC349A strongly dominates, the change seems insignificant, allowing for the combined photometry of the system.

The author(s) of this abstract have provided an email address for comments about the abstract: kerry@rabi.phys.columbia.edu

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