ABSTRACT
Understanding how giant planets form requires observational input from directly imaged protoplanets. We used VLT/NACO and VLT/SPHERE to search for companions in the transition disc of 2MASS ...J19005804-3645048 (hereafter CrA-9), an accreting M0.75 dwarf with an estimated age of 1–2 Myr. We found a faint point source at ∼0.7-arcsec separation from CrA-9 (∼108 au projected separation). Our 3-epoch astrometry rejects a fixed background star with a 5σ significance. The near-IR absolute magnitudes of the object point towards a planetary-mass companion. However, our analysis of the 1.0–3.8$\,\mu$m spectrum extracted for the companion suggests it is a young M5.5 dwarf, based on both the 1.13-μm Na index and comparison with templates of the Montreal Spectral Library. The observed spectrum is best reproduced with high effective temperature ($3057^{+119}_{-36}$K) BT-DUSTY and BT-SETTL models, but the corresponding photometric radius required to match the measured flux is only $0.60^{+0.01}_{-0.04}$ Jovian radius. We discuss possible explanations to reconcile our measurements, including an M-dwarf companion obscured by an edge-on circum-secondary disc or the shock-heated part of the photosphere of an accreting protoplanet. Follow-up observations covering a larger wavelength range and/or at finer spectral resolution are required to discriminate these two scenarios.
Context.
In recent years high-angular-resolution observations have revealed that circumstellar discs appear in a variety of shapes with diverse substructures being ubiquitous. This has given rise to ...the question of whether these substructures are triggered by planet–disc interactions. Besides direct imaging, one of the most promising methods to distinguish between different disc-shaping mechanisms is to study the kinematics of the gas disc. In particular, the deviations of the rotation profile from Keplerian velocity can be used to probe perturbations in the gas pressure profile that may be caused by embedded (proto-) planets.
Aims.
In this paper we aim to analyse the gas brightness temperature and kinematics of the transitional disc around the intermediate-mass star CQ Tau in order to resolve and characterise substructure in the gas caused by possible perturbers.
Methods.
For our analysis we used spatially resolved ALMA observations of the three CO isotopologues
12
CO,
13
CO, and C
18
O (
J
= 2−1) from the disc around CQ Tau. We further extracted robust line centroids for each channel map and fitted a number of Keplerian disc models to the velocity field.
Results.
The gas kinematics of the CQ Tau disc present non-Keplerian features, showing bent and twisted iso-velocity curves in
12
CO and
13
CO. Significant spiral structures are detected between ~10 and 180 au in both the brightness temperature and the rotation velocity of
12
CO after subtraction of an azimuthally symmetric model, which may be tracing planet–disc interactions with an embedded planet or low-mass companion. We identify three spirals, two in the brightness temperature and one in the velocity residuals, spanning a large azimuth and radial extent. The brightness temperature spirals are morphologically connected to spirals observed in near-infrared scattered light in the same disc, indicating a common origin. Together with the observed large dust and gas cavity, these spiral structures support the hypothesis of a massive embedded companion in the CQ Tau disc.
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
μ
m) 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
M
Jup
on the mass of possible other companions down to separations of few tens of au.
Context. We present a detailed analysis of the extended structure detected around the young and close-by Herbig Ae/Be star R CrA. This is a young triple system with an intermediate mass central ...binary whose separation is of the order of a few tens of the radii of the individual components, and an M-star companion at about 30 au. Aims. Our aim is to understand the nature of the extended structure by means of combining integral-field and high-resolution spectroscopy. Methods. We conducted the analysis based on FEROS archival optical spectroscopy data and adaptive optics images and integral-field spectra obtained with SINFONI and SPHERE at the VLT. Results. The observations reveal a complex extended structure that is composed of at least two components: a non-uniform wide cavity whose walls are detected in continuum emission up to 400 au, and a collimated wiggling-jet detected in the emission lines of helium and hydrogen. Moreover, the presence of Fe II emission projected close to the cavity walls suggests the presence of a slower moving wind, most likely a disk wind. The multiple components of the optical forbidden lines also indicate the presence of a high-velocity jet co-existing with a slow wind. We constructed a geometrical model of the collimated jet flowing within the cavity using intensity and velocity maps, finding that its wiggling is consistent with the orbital period of the central binary. The cavity and the jet do not share the same position angle, suggesting that the jet is itself experiencing a precession motion possibly due to the wide M-dwarf companion. Conclusions. We propose a scenario that closely agrees with the general expectation of a magneto-centrifugal-launched jet. These results build upon the extensive studies already conducted on R CrA.
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.
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