Mathematics
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21934810h&link_type=abstract
American Astronomical Society, AAS Meeting #219, #348.10
Mathematics
Scientific paper
We report on a photometric monitoring of MWC 349A with the CCD-equipped Maria Mitchell Observatory's 24-inch telescope in 2009-2011. The goal of the project was to separate the Hα emission line variations from those of the continuum. We present our new method of the line/continuum separation (based on observations with two interference filters of different widths centered on Hα) and the results of the monitoring. Variations of both the red continuum and the Hα emission with amplitudes up to 0.1 magnitude on relatively short time scales (weeks and months) were superimposed on a secular drop of the star's brightness by approximately 0.3 magnitudes during the past 15 years. More recently, we found that the previously suspected periodicity with the period of ca. 240 days was followed by a long (more than a year) interval of virtually constant brightness. In our method of line/continuum separation, random and systematic errors in the outcomes from the two filters create an artificial anti-correlation between the extracted line and continuum intensities. However, considerable anti-correlation was observed even after smoothing the data for periods as long as a month. On shorter time scales, possible intrinsic anti-correlation has been corroborated by separating the emission line from the continuum with two independent filter combinations. If the intrinsic anti-correlation is real, it can be explained by the well-known inverse dependence of the recombination line emissivity on electron temperature, the latter being directly proportional to the ionizing ultraviolet continuum of the star. This project was supported by NSF/REU grant AST-0851892, the Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring and the Nantucket Maria Mitchell Association.
Bosworth B.
Hillbrand Alexander
Sliski David
Strelnitski Vladimir
Walker Gabrielle
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