The origin of R CrA variability. A complex triple system hosting a disk
Abstract
Context. R CrA is the brightest member of the Coronet star-forming region and is the closest Herbig AeBe star with a spectrum dominated by emission lines. Its luminosity has been monitored since the end of the nineteenth century, but the origin of its variability, which shows a stable period of 65.767 ± 0.007 days, is still unknown.
Aims: We studied photometric and spectroscopic data for this star to investigate the nature of the variability of R CrA.
Methods: We exploited the fact that the near-infrared luminosity of the Herbig AeBe stars is roughly proportional to the total luminosity of the stars to derive the absorption, and then mass and age of R CrA. In addition, we modeled the periodic modulation of the light curve as due to partial attenuation of a central binary by a circumbinary disk. This model reproduces the observations very well.
Results: We found that the central object in R CrA is a very young (1.5 ± 1.5 Myr) highly absorbed (AV = 5.47 ± 0.4 mag) binary; we obtain masses of MA = 3.02 ± 0.43 M⊙ and MB = 2.32 ± 0.35 M⊙ for the two components. We propose that the secular decrease of the apparent luminosity of R CrA is due to a progressive increase of the disk absorption. This might be related to precession of a slightly inclined disk caused by the recently discovered M-dwarf companion. This means that R CrA might be a triple system hosting a disk.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2019
- DOI:
- 10.1051/0004-6361/201936101
- arXiv:
- arXiv:1908.07256
- Bibcode:
- 2019A&A...630A.132S
- Keywords:
-
- stars: pre-main sequence;
- circumstellar matter;
- accretion;
- accretion disks;
- protoplanetary disks;
- planets and satellites: formation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in A&