Exploring the R CrA environment with SPHERE

Abstract

Aims. R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. This star is very red in color, probably due to dust absorption, and is strongly variable. High-contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star. Methods. We observed R CrA with the near-infrared (NIR) channels (IFS and IRDIS) of SPHERE at the Very Large Telescope (VLT). In this paper, we used four different epochs, three of which are from open time observations while one is from SPHERE guaranteed time. The data were reduced using the data reduction and handling pipeline and the SPHERE Data Center. We implemented custom IDL routines on the reduced data with the aim to subtract the speckle halo. We have also obtained pupil-tracking H-band (1.45−1.85 μm) observations with the VLT/SINFONI NIR medium-resolution (R ∼ 3000) spectrograph. Results. A companion was found at a separation of 0.156″ from the star in the first epoch and increasing to 0.184″ in the final epoch. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure northeast from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and SINFONI spectrum, once corrected for extinction, point toward a spectral type object that is early M with a mass between 0.3 and 0.55 M⊙. The astrometric analyis provides constraints on the orbit paramenters: e ∼ 0.4, semimajor axis at 27–28 au, inclination of ∼70°, and a period larger than 30 yr. We were also able to put constraints of few MJup on the mass of possible other companions down to separations of few tens of au.

Discovery of a Low-mass Companion Embedded in the Disk of the Young Massive Star MWC 297 with VLT/SPHERE*

“…Each component might be embedded and surrounded by their own disk, in addition to any remnant envelope (e.g. Bowler et al 2014;Mesa et al 2019). Therefore, following Christiaens et al (2018), we considered extinction as a free parameter when fitting BT-SETTL models (Allard et al 2012).…”

2MASS J15491331-3539118: a new low-mass wide companion of the GQ Lup system

“…This is probably due to the edge-on geometry of the object which may affect the photocentre measurement. We note that other objects, such as Sz 102 in Lupus, RY Tau in Taurus (see Garufi et al 2019), and R CrA (Mesa et al 2019), with similar edge-on geometries to that of 2MASS J15491331 or extended circumstellar structures suffer from the same DR2 problem. As concluded in Sect.…”

Investigating the nature of the extended structure around the Herbig star RCrA using integral field and high-resolution spectroscopy

“…In this section, we describe the observations of R CrA acquired in recent years with SPHERE and SINFONI at VLT (summarized in Table 1), and FEROS at the 2.2 m telescope in La Silla. We focus here on the elongated structure already reported in Mesa et al (2019), and identified in Figure 1, analyzing the emission spectrum of the source, and investigating the origin of the emitting lines in light of images of the jet-like structure observed in the SPHERE data.…”

“…A H-band image of R CrA was obtained with the AO-fed integral field spectrograph SINFONI (Eisenhauer et al 2003;Bonnet et al 2004) operating between 1.45-1.85 µm with a resolution Mesa et al (2019), which appears elongated as a consequence of the differential imaging adopted. Solid and dashed lines refer to the median PA and aperture of the "elongated structure" as measured in Sect.…”

“…They point out that CO emission in the R CrA spectrum is likely due to an outflow, as also suggested from the bow-shocks seen in shocked H2 emission in the immediate vicinity of R CrA (Kumar et al 2011). The study of R CrA has gained new momentum in recent years, thanks to high-contrast imaging observations obtained with SPHERE (Mesa et al 2019) and the NAOS-CONICA at VLT (Cugno et al 2019). These studies focused their attention on the detection of a stellar companion as close as 19-28 au, and with a mass range between 0.1-1.0 M .…”