ABSTRACT
The combination of high-resolution and sensitivity offered by ALMA is revolutionizing our understanding of protoplanetary discs, as their bulk gas and dust distributions can be studied ...independently. In this paper we present resolved ALMA observations of the continuum emission (λ = 1.3 mm) and CO isotopologues (12CO, 13CO, C18O, J = 2 − 1) integrated intensity from the disc around the nearby (d = 162 pc), intermediate-mass ($M_{\star }=1.67\, \mathrm{M}_{\odot }$) pre-main-sequence star CQ Tau. The data show an inner depression in continuum and in both 13CO and C18O emission. We employ a thermo-chemical model of the disc reproducing both continuum and gas radial intensity profiles, together with the disc spectral energy distribution. The models show that a gas inner cavity with size between 15 and 25 au is needed to reproduce the data with a density depletion factor between ∼10−1 and ∼10−3. The radial profile of the distinct cavity in the dust continuum is described by a Gaussian ring centred at $R_{\rm dust}=53\,$au and with a width of $\sigma =13\,$au. Three-dimensional gas and dust numerical simulations of a disc with an embedded planet at a separation from the central star of ${\sim }20\,$ au and with a mass of ${\sim } 6\!-\!9\, M_{\rm Jup}$ reproduce qualitatively the gas and dust profiles of the CQ Tau disc. However, a one-planet model appears not to be able to reproduce the dust Gaussian density profile predicted using the thermo-chemical modeling.
We have measured astrometry for members of the Orion Nebula Cluster with images obtained in 2015 with the Wide Field Camera 3 on board the Hubble Space Telescope. By comparing those data to previous ...measurements with the Near-Infrared Camera and Multi-Object Spectrometer on Hubble in 1998, we have discovered that a star in the Kleinmann-Low Nebula, source x from Lonsdale et al., is moving with an unusually high proper motion of 29 mas yr super(?1), which corresponds to 55 km s super(?1) at the distance of Orion. Previous radio observations have found that three other stars in the Kleinmann-Low Nebula (the Becklin-Neugebauer object and sources I and n) have high proper motions (5-14 mas yr super(?1)) and were near a single location ~540 years ago, and thus may have been members of a multiple system that dynamically decayed. The proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star BN originated in the Kleinmann-Low Nebula rather than the nearby Trapezium cluster. However, our constraint on the motion of source n is significantly smaller than the most recent radio measurement, which indicates that it did not participate in the event that ejected the other three stars.
Abstract
We report the discovery of a low-mass stellar companion around the young Herbig Be star MWC 297. We performed multi-epoch high-contrast imaging in the near-infrared with the Very Large ...Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. The companion is found at a projected separation of 244.7 ± 13.2 au and a position angle of 176.4 ± 0.1 deg. The large separation supports formation via gravitational instability. From the spectrum, we estimate a mass of 0.1–0.5
M
⊙
, the range conveying uncertainties in the extinction of the companion and in evolutionary models at young ages. The orbit coincides with a gap in the dust disk inferred from the spectral energy distribution. The young age (≲1 Myr) and mass ratio with the central star (∼0.01) makes the companion comparable to PDS 70 b, suggesting a relation between formation scenarios and disk dynamics.
On the cavity size in circumbinary discs Hirsh, Kieran; Price, Daniel J; Gonzalez, Jean-François ...
Monthly notices of the Royal Astronomical Society,
10/2020, Letnik:
498, Številka:
2
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
How does the cavity size in circumbinary discs depend on disc and binary properties? We investigate by simulating disc cavities carved by binary companions using smoothed particle ...hydrodynamics. We find that a cavity is quickly opened on the dynamical time, while the cavity size is set on the viscous time. In agreement with previous findings, we find long-term cavity sizes of 2–5 times the binary semimajor axis, increasing with eccentricity and decreasing with disc aspect ratio. When considering binaries inclined with respect to the disc, we find three regimes: (i) discs that evolve towards a coplanar orbit have a large cavity, slightly smaller than that of an initially coplanar disc; (ii) discs that evolve towards a polar orbit by breaking have a small cavity, equal in size to that of an initially polar disc; and (iii) discs that evolve towards a polar orbit via warping have an intermediate-sized cavity. We find typical gas depletions inside the cavity of ≳2 orders of magnitude in surface density.
We have measured astrometry for members of the Orion Nebula Cluster with images obtained in 2015 with the Wide Field Camera 3 on board the Hubble Space Telescope. By comparing those data to previous ...measurements with the Near-Infrared Camera and Multi-Object Spectrometer on Hubble in 1998, we have discovered that a star in the Kleinmann-Low Nebula, source x from Lonsdale et al., is moving with an unusually high proper motion of 29 mas yr−1, which corresponds to 55 km s−1 at the distance of Orion. Previous radio observations have found that three other stars in the Kleinmann-Low Nebula (the Becklin-Neugebauer object and sources I and n) have high proper motions (5-14 mas yr−1) and were near a single location ∼540 years ago, and thus may have been members of a multiple system that dynamically decayed. The proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star BN originated in the Kleinmann-Low Nebula rather than the nearby Trapezium cluster. However, our constraint on the motion of source n is significantly smaller than the most recent radio measurement, which indicates that it did not participate in the event that ejected the other three stars.
The combination of high resolution and sensitivity offered by ALMA is revolutionizing our understanding of protoplanetary discs, as their bulk gas and dust distributions can be studied independently. ...In this paper we present resolved ALMA observations of the continuum emission (\(\lambda=1.3\) mm) and CO isotopologues (\(^{12}\)CO, \(^{13}\)CO, C\(^{18}\)O \(J=2-1\)) integrated intensity from the disc around the nearby (\(d = 162\) pc), intermediate mass (\(M_{\star}=1.67\,M_{\odot}\)) pre-main-sequence star CQ Tau. The data show an inner depression in continuum, and in both \(^{13}\)CO and C\(^{18}\)O emission. We employ a thermo-chemical model of the disc reproducing both continuum and gas radial intensity profiles, together with the disc SED. The models show that a gas inner cavity with size between 15 and 25 au is needed to reproduce the data with a density depletion factor between \(\sim 10^{-1}\) and \(\sim 10^{-3}\). The radial profile of the distinct cavity in the dust continuum is described by a Gaussian ring centered at \(R_{\rm dust}=53\,\)au and with a width of \(\sigma=13\,\)au. Three dimensional gas and dust numerical simulations of a disc with an embedded planet at a separation from the central star of \(\sim20\,\)au and with a mass of \(\sim 6\textrm{-} 9\,M_{\rm Jup}\) reproduce qualitatively the gas and dust profiles of the CQ Tau disc. However, a one planet model appears not to be able to reproduce the dust Gaussian density profile predicted using the thermo-chemical modeling.
We report the discovery of a low-mass stellar companion around the young Herbig Be star MWC 297. We performed multi-epoch high-contrast imaging in the near-infrared with the Very Large Telescope ...(VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. The companion is found at a projected separation of 244.7 13.2 au and a position angle of 176.4 0.1 deg. The large separation supports formation via gravitational instability. From the spectrum, we estimate a mass of 0.1-0.5 M , the range conveying uncertainties in the extinction of the companion and in evolutionary models at young ages. The orbit coincides with a gap in the dust disk inferred from the spectral energy distribution. The young age ( 1 Myr) and mass ratio with the central star (∼0.01) makes the companion comparable to PDS 70 b, suggesting a relation between formation scenarios and disk dynamics.
We have measured astrometry for members of the Orion Nebula Cluster with images obtained in 2015 with the Wide Field Camera 3 on board the Hubble Space Telescope. By comparing those data to previous ...measurements with NICMOS on Hubble in 1998, we have discovered that a star in the Kleinmann-Low Nebula, source x from Lonsdale et al. (1982), is moving with an unusually high proper motion of 29 mas/yr, which corresponds to 55 km/s at the distance of Orion. Previous radio observations have found that three other stars in the Kleinmann-Low Nebula (BN and sources I and n) have high proper motions (5-14 mas/yr) and were near a single location ~540 years ago, and thus may have been members of a multiple system that dynamically decayed. The proper motion of source x is consistent with ejection from that same location 540 years ago, which provides strong evidence that the dynamical decay did occur and that the runaway star BN originated in the Kleinmann-Low Nebula rather than the nearby Trapezium cluster. However, our constraint on the motion of source n is significantly smaller than the most recent radio measurement, which indicates that it did not participate in the event that ejected the other three stars.
How does the cavity size in circumbinary discs depend on disc and binary properties? We investigate by simulating disc cavities carved by binary companions using smoothed particle hydrodynamics ...(SPH). We find that a cavity is quickly opened on the dynamical time, while the cavity size is set on the viscous time. In agreement with previous findings, we find long term cavity sizes of 2-5 times the binary semi-major axis, increasing with eccentricity and decreasing with disc aspect ratio. When considering binaries inclined with respect to the disc we find three regimes: i) discs that evolve towards a coplanar orbit have a large cavity, slightly smaller than that of an initially coplanar disc; ii) discs that evolve towards a polar orbit by breaking have a small cavity, equal in size to that of an initially polar disc; iii) discs that evolve towards a polar orbit via warping have an intermediate-sized cavity. We find typical gas depletions inside the cavity of \(\gtrsim 2\) orders of magnitude in surface density.
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