A Model of the Dust Envelope of the Carbon Mira Star V CrB from Photometry, Infrared Spectroscopy, and Speckle Polarimetryстатья
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Дата последнего поиска статьи во внешних источниках: 7 июля 2020 г.
Аннотация:UBVJHKLM photometry for the carbon Mira star V CrB are presented. The infraredobservations were carried out in the time interval 1989–2018, while theU,B,andVdata were obtainedin 2001–2014. The light and color curves are analyzed. The pulsation period of V CrB has been found tobe355d.2in the infraredJHKLMbands and352dfor the opticalBVband. In theJHKbands, apartfrom periodic pulsations, there are distinct sinusoidal variations in the average brightness level with acharacteristic period of∼8300days. Color–magnitude relationships have been revealed for the infraredand optical bands. The phase curves exhibit the wavelength dependence of the brightness variabilityamplitude. The light curves for various bands and colors are discussed. We have constructed the modelof a spherically symmetric circumstellar dust envelope that allows the observed spectral energy distributionat both maximum and minimum light to be reproduced equally well (within the model assumptions) and isconsistent with the observations of V CrB by differential speckle polarimetry. The model is characterizedby the following parameters: the optical depth isτK=0.33, the inner and outer radii of the envelopeare 8 and 40 000 AU, respectively. The envelope contains spherical carbon dust grains (3/4by mass)and silicon carbide dust grains. Dust grains with a radius of 0.5μm account for90%of the envelopemass. The remaining10%of the mass is accounted for byfiner dust with a grain radius of 0.1μm.Based on the observational data, we have estimated the bolometricflux from V CrB:2.6×10−7and5.1×10−7erg cm−2s−1at minimum and maximum light, respectively. The effective temperature of thestar isTmax= 3000K at maximum light andTmin= 2400K at minimum light.