Volume 630, October 2019
|Number of page(s)||13|
|Section||Stellar structure and evolution|
|Published online||04 October 2019|
The origin of R CrA variability
A complex triple system hosting a disk
INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
2 INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
3 INAF-Osservatorio Astrofisico di Catania, Via S.Sofia 78, 95123 Catania, Italy
Accepted: 1 August 2019
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.
Key words: stars: pre-main sequence / circumstellar matter / accretion / accretion disks / protoplanetary disks / planets and satellites: formation
© ESO 2019
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