- ID:
- ivo://CDS.VizieR/J/A+A/606/A125
- Title:
- HD163296 DCO+, DCN and N_2_D+ data cubes
- Short Name:
- J/A+A/606/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deuterium fractionation has been used to study the thermal history of prestellar environments. Their formation pathways trace different regions of the disk and may shed light into the physical structure of the disk, including locations of important features for planetary formation. We aim to constrain the radial extent of the main deuterated species; we are particularly interested in spatially characterizing the high and low temperature pathways for enhancing deuteration of these species. We observed the disk surrounding the Herbig Ae star HD 163296 using ALMA in Band 6 and obtained resolved spectral imaging data of DCO^+^ (J=3-2), DCN (J=3-2) and N_2_D^+^ (J=3-2) with synthesized beam sizes of 0.53"x0.42", 0.53"x0.42", and 0.50"x0.39", respectively. We adopted a physical model of the disk from the literature and use the 3D radiative transfer code LIME to estimate an excitation temperature profile for our detected lines. We modeled the radial emission profiles of DCO^+^, DCN, and N_2_D^+^, assuming their emission is optically thin, using a parametric model of their abundances and our excitation temperature estimates.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/650/A59
- Title:
- HD 142527 disk 13CO and C18O images
- Short Name:
- J/A+A/650/A59
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Vortices are one of the most promising mechanisms to locally concentrate millimeter dust grains and allow the formation of planetesimals through gravitational collapse. The outer disk around the binary system HD 142527 is known for its large horseshoe structure with azimuthal contrasts of ~3-5 in the gas surface density and of ~50 in the dust. Using ^13^CO and C^18^O J=3-2 transition lines, we detect kinematic deviations to the Keplerian rotation, which are consistent with the presence of a large vortex around the dust crescent, as well as a few spirals in the outer regions of the disk. Comparisons with a vortex model suggest velocity deviations up to 350m/s after deprojection compared to the background Keplerian rotation, as well as an extension of +/-40au radially and ~200{deg} azimuthally, yielding an azimuthal-to-radial aspect ratio of ~5. Another alternative for explaining the vortex-like signal implies artificial velocity deviations generated by beam smearing in association with variations of the gas velocity due to gas pressure gradients at the inner and outer edges of the circumbinary disk. The two scenarios are currently difficult to differentiate and, for this purpose, would probably require the use of multiple lines at a higher spatial resolution. The beam smearing effect, due to the finite spatial resolution of the observations and gradients in the line emission, should be common in observations of protoplanetary disks and may lead to misinterpretations of the gas velocity, in particular around ring-like structures.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A75
- Title:
- HD 97048 H13CO+ and HC15N first detections
- Short Name:
- J/A+A/629/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of different molecular lines in protoplanetary disks provide valuable information on the gas kinematics, as well as constraints on the radial density and temperature structure of the gas. With ALMA we have detected H13CO+ (J=4-3) and HC15N (J=4-3) in the HD 97048 protoplanetary disk for the first time. We compare these new detections to the ringed continuum mm-dust emission and the spatially resolved CO (J=3-2) and HCO+ (J=4-3) emission. The radial distributions of the H^13^CO^+^ and HC^15^N emission show hints of ringed sub-structure whereas, the optically thick tracers, CO and HCO+, do not. We calculate the HCO^+^/H^13^CO^+^ intensity ratio across the disk and find that it is radially constant (within our uncertainties). We use a physio-chemical parametric disk structure of the HD 97048 disk with an analytical prescription for the HCO^+^ abundance distribution to generate synthetic observations of the HCO^+^ and H^13^CO^+^ disk emission assuming LTE. The best by-eye fit models require radial variations in the HCO^+^/H^13^CO^+^ abundance ratio and an overall enhancement in H^13^CO^+^ relative to HCO^+^. This highlights the need to consider isotope selective chemistry and in particular low temperature carbon isotope exchange reactions. This also points to the presence of a reservoir of cold molecular gas in the outer disk (T<10K, R>200au). Chemical models are required to confirm that isotope-selective chemistry alone can explain the observations presented here. With these data, we cannot rule out that the known dust substructure in the HD 97048 disk is responsible for the observed trends in molecular line emission, and higher spatial resolution observations are required to fully explore the potential of optically thin tracers to probe planet-carved dust gaps. We also report non-detections of H^13^CO^+^ and HC^15^N in the HD 100546 protoplanetary disk.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A121
- Title:
- HD 139614 polarization Stokes Q and U images
- Short Name:
- J/A+A/635/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly due to an inclined (sub-)stellar companion embedded in the disk. We study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. We obtained J- and H-band observations in polarized scattered light with VLT/SPHERE that show strong azimuthal asymmetries. In the outer disk, beyond ~30au, a broad shadow spans a range of ~240{deg} in position angle, in the East. A bright ring at ~16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at ~34au and ~50au. We created a simple 4-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. We find that the shadow on the outer disk covers a range of position angle too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones -- or a continuously warped region -- to cast this broad shadow on the outer disk. A small misalignment of ~4{deg} between adjacent components can reproduce most of the observed shadow features. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust depleted gap responsible for a dip in the SED.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A68
- Title:
- HD 261711 reduced spectrum
- Short Name:
- J/A+A/552/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The internal structure of pre-main-sequence (PMS) stars is poorly constrained at present. This could change significantly through high-quality asteroseismological observations of a sample of such stars. We concentrate on an asteroseismological study of HD 261711, a rather hot delta Scuti-type pulsating member of the young open cluster NGC 2264 located at the blue border of the instability region. HD 261711 was discovered to be a pre-main sequence delta Scuti star using the time series photometry obtained by the MOST satellite in 2006. High-precision, time-series photometry of HD 261711 was obtained by the MOST and CoRoT satellites in four separate new observing runs that are put into context with the star's fundamental atmospheric parameters obtained from spectroscopy. Frequency Analysis was performed using Period04. The spectral analysis was performed using equivalent widths and spectral synthesis. With the new MOST data set from 2011/12 and the two CoRoT light curves from 2008 and 2011/12, the delta Scuti variability was confirmed and regular groups of frequencies were discovered. The two pulsation frequencies identified in the data from the first MOST observing run in 2006 are confirmed and 23 new delta Scuti-type frequencies were discovered using the CoRoT data. Weighted average frequencies for each group were determined and are related to l=0 and l=1 p-modes. Evidence for amplitude modulation of the frequencies in two groups is seen. The effective temperature (Teff) was derived to be 8600+/-200K, logg is 4.1+/-0.2, and the projected rotational velocity (vsini) is 53+/-1km/s. Using our Teff value and the radius of 1.8+/-0.5R_{sun}_ derived from spectral energy distribution (SED) fitting, we get a luminosity logL/L_{sun}_ of 1.20+/-0.14 which agrees well to the seismologically determined values of 1.65 Rsun and, hence, a logL/L_{sun}_ of 1.13. The radial velocity of 14+/-2km/s we derived for HD 261711, confirms the star's membership to NGC 2264. Our asteroseismic models suggest that HD 261711 is a delta Scuti-type star close to the zero-age main sequence (ZAMS) with a mass of 1.8 to 1.9M_{sun}_. With an age of about 10 million years derived from asteroseismology, the star is either a young ZAMS star or a late PMS star just before the onset of hydrogen-core burning. The observed splittings about the l=0 and 1 parent modes may be an artifact of the Fourier derived spectrum of frequencies with varying amplitudes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/493/234
- Title:
- Herbig Ae/Be accretion rates & mechanisms
- Short Name:
- J/MNRAS/493/234
- Date:
- 02 Feb 2022 07:28:24
- Publisher:
- CDS
- Description:
- This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity, and age are homogeneously determined. Mass accretion rates are determined from H{alpha} emission line measurements. Our data is complemented with the X-Shooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases as a function of stellar mass, and the existence of a different slope for lower and higher mass stars, respectively. The mass where the slope changes is determined to be 3.98^+1.37_-0.94M_{sun}_. We discuss this break in the context of different modes of disc accretion for low- and high-mass stars. Because of their similarities with T Tauri stars, we identify the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for the earlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally, we investigated the mass accretion-age relationship. Even using the superior Gaia based data, it proved hard to select a large enough sub-sample to remove the mass dependence in this relationship. Yet, it would appear that the mass accretion does decline with age as expected from basic theoretical considerations.
- ID:
- ivo://CDS.VizieR/J/AJ/129/856
- Title:
- Herbig Ae/Be stars in nearby OB associations
- Short Name:
- J/AJ/129/856
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a study of the early-type stars in nearby OB associations spanning an age range of ~3-16Myr, with the aim of determining the fraction of stars that belong to the Herbig Ae/Be class. We studied the B, A, and F stars in the nearby (<=500pc) OB associations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1, with membership determined from Hipparcos (Cat. <I/239>) data. We also included in our study the early-type stars in the Trumpler 37 cluster, part of the Cep OB2 association. We obtained spectra for 440 Hipparcos stars in these associations, from which we determined accurate spectral types, visual extinctions, effective temperatures, luminosities and masses, using Hipparcos photometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/976
- Title:
- Herbig Ae/Be X-shooter observations
- Short Name:
- J/MNRAS/453/976
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Herbig Ae/Be stars (HAeBes) span a key mass range that links low- and high-mass stars, and thus provide an ideal window from which to explore their formation. This paper presents Very Large Telescope/X-shooter spectra of 91 HAeBes, the largest spectroscopic study of HAeBe accretion to date. A homogeneous approach to determining stellar parameters is undertaken for the majority of the sample. Measurements of the ultraviolet are modelled within the context of magnetospheric accretion, allowing a direct determination of mass accretion rates. Multiple correlations are observed across the sample between accretion and stellar properties: the youngest and often most massive stars are the strongest accretors, and there is an almost 1:1 relationship between the accretion luminosity and stellar luminosity. Despite these overall trends of increased accretion rates in HAeBes when compared to classical T Tauri stars, we also find noticeable differences in correlations when considering the Herbig Ae and Herbig Be subsets. This, combined with the difficulty in applying a magnetospheric accretion model to some of the Herbig Be stars, could suggest that another form of accretion may be occurring within Herbig Be mass range.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A30
- Title:
- Herschel maps of {rho} Oph
- Short Name:
- J/A+A/581/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of nearby star-forming regions with the Herschel Space Observatory complement our view of the protoplanetary disks in Ophiuchus with information about the outer disks. The main goal of this project is to provide new far-infrared fluxes for the known disks in the core region of Ophiuchus and to identify potential transitional disks using data from Herschel. We obtained PACS and SPIRE photometry of previously spectroscopically confirmed young stellar objects (YSO) in the region and analysed their spectral energy distributions.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A82
- Title:
- HH83 outflow spectrally select. structures pm
- Short Name:
- J/A+A/652/A82
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We continue our program of investigation of the proper motions of spectrally separated structures in the Herbig-Haro outflows with the aid of Fabry-Perot scanning interferometry. This work mainly focuses on the physical nature of various structures in the jets. The aim of the present study is to measure the proper motions of the previously discovered kinematically separated structures in the working surface of the HH 83 collimated outflow. We used observations from two epochs separated by 15 years, which were performed on the 6m telescope with Fabry-Perot scanning interferometer. We obtained images corresponding to different radial velocities for the two separate epochs, and used them to measure proper motions. In the course of our data analysis, we discovered a counter bow-shock of HH 83 flow with positive radial velocity, which makes this flow a relatively symmetric bipolar system. The second epoch observations confirm that the working surface of the flow is split into two structures with an exceptionally large (250km/s) difference in radial velocity. The proper motions of these structures are almost equal, which suggests that they are physically connected. The asymmetry of the bow shock and the turning of proper motion vectors suggests a collision between the outflow and a dense cloud. The profile of the H{alpha} line for the directly invisible infrared source HH 83 IRS, obtained by integration of the data within the reflection nebula, suggests it to be of P Cyg type with a broad absorption component characteristic of the FU Ori-like objects. If this object underwent an FU Ori type outburst, which created the HH 83 working surfaces, its eruption took place about 1500 years ago according to the kinematical age of the outflow.
