The variable V381 Lac and its possible connection with the R CrB phenomenon
arXiv:1512.00146 · doi:10.1093/mnras/stv2824
Abstract
We have performed new medium resolution spectroscopy, optical and near infrared photometry to monitor the variability of the AGB carbon star V 381 Lac. Our observations revealed rapid and deep changes in the spectrum and extreme variability in the optical and near infrared bands. Most notably we observed the change of NaI D lines from deep absorption to emission, and the progressive growing of the [N II] doublet 6548-6584 A emission, strongly related to the simultaneous photometric fading. V381 Lac occupies regions of 2MASS and WISE colour-colour diagrams typical of stars with dust formation in the envelope. The general framework emerging from the observations of V381 Lac is that of a cool AGB carbon star undergoing episodes of high mass ejection and severe occultation of the stellar photosphere reminiscent of those characterising the RCB phenomenon. Comparing the Spectral Energy Distribution obtained with the theoretical model for AGB evolution with dust in the circumstellar envelope, we can identify V381 Lac as the descendant of a star of initial mass ~2M_sun, in the final AGB phases, evolved into a carbon star by repeated Third Dredge Up episodes. According to our model the star is moderately obscured (tau_10 ~0.22) by dust, mainly formed by amorphous carbon (~80%) and SiC (~20%), with dust grain dimensions around ~0.2 micron and 0.08 micron respectively.
8 pages, 6 figures, accepted by MNRAS
References in corpus (6)
- Near-Infrared Photometry of Carbon Stars
- Dust-driven Winds and Mass Loss of C-rich AGB Stars with subsolar Metallicities
- AGB stars in the LMC: evolution of dust in circumstellar envelopes
- The meaning of WISE colours - I. The Galaxy and its satellites
- Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS
- R Coronae Borealis at the 2003 Light Minimum