The peculiar fast-rotating star 51 Oph probed by VEGA/CHARA

Abstract

Stellar rotation is a key in our understanding of both mass-loss and evolution of intermediate and massive stars. It can lead to anisotropic mass-loss in the form of radiative wind or an excretion disk. We wished to spatially resolve the photosphere and gaseous environment of 51 Oph, a peculiar star with a very high vsin(i) of 267km s${}^{-1}$ and an evolutionary status that remains unsettled. It has been classified by different authors as a Herbig, a $\beta$ Pic, or a classical Be star. We used the VEGA visible beam combiner installed on the CHARA array that reaches a submilliarcsecond resolution. Observation were centered on the H$\alpha$ emission line. We derived, for the first time, the extension and flattening of 51 Oph photosphere. We found a major axis of ${\theta }_{\mathrm{eq}}$=8.08$\pm$0.70$R_{\odot }$ and a minor axis of ${\theta }_{\mathrm{pol}}$=5.66$\pm$0.23$R_{\odot }$ . This high photosphere distortion shows that the star is rotating close to its critical velocity. Finally, using spectro-interferometric measurements in the H$\alpha$ line, we constrained the circumstellar environment geometry and kinematics and showed that the emission is produced in a 5.2$\pm$2R${}_{\ast }$ disk in Keplerian rotation. From the visible point of view, 51 Oph presents all the features of a classical Be star: near critical-rotation and double-peaked H$\alpha$ line in emission produced in a gaseous disk in Keplerian rotation. However, this does not explain the presence of dust as seen in the mid-infrared and millimeter spectra, and the evolutionary status of 51 Oph remains unsettled.

arXiv commentPublished in A&A Letter. 5 pages, 3 figures, 3 tables

References in corpus (16)

• Validation of the new Hipparcos reduction
• ISO spectroscopy of circumstellar dust in 14 Herbig Ae/Be systems: towards an understanding of dust processing
• First Results from the CHARA Array. II. A Description of the Instrument
• Imaging the Surface of Altair
• The spinning-top Be star Achernar from VLTI-VINCI
• Vega is a rapidly rotating star
• First Results from the CHARA Array VII: Long-Baseline Interferometric Measurements of Vega Consistent with a Pole-On, Rapidly Rotating Star
• SearchCal: a Virtual Observatory tool for searching calibrators in optical long baseline interferometry. I: The bright object case
• First direct detection of a Keplerian rotating disk around the Be star $\alpha$ Arae using the VLTI/AMBER instrument
• First spectro-interferometric survey of Be stars I. Observations and constraints on the disks geometry and kinematics
• Evidence for a hot dust-free inner disk around 51 Oph
• Spatially resolving the hot CO around the young Be star 51 Ophiuchi
• The composition of circumstellar gas and dust in 51 Oph
• The binary Be star δ Sco at high spectral and spatial resolution: Disk geometry and kinematics before the 2011 periastron
• 51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller
• Nature of the gas and dust around 51 Oph

Cited by in corpus (6)

• Spiral Arms in Disks: Planets or Gravitational Instability?
• VISION: A Six-Telescope Fiber-Fed Visible Light Beam Combiner for the Navy Precision Optical Interferometer
• Ultraviolet Spectropolarimetry: on the origin of rapidly rotating B stars
• On the inner disk structure of MWC480: evidence for asymmetries?
• Identification of emission-line stars in transition phase from pre-main sequence to main sequence
• The GRAVITY Young Stellar Object survey IV. The CO overtone emission in 51 Oph at sub-au scales