- ID:
- ivo://CDS.VizieR/J/A+A/649/A25
- Title:
- (Possible spiral in the disk around HD34282
- Short Name:
- J/A+A/649/A25
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- During the evolution of protoplanetary disks into planetary systems we expect to detect signatures that trace mechanisms such as planet-disk interaction. Protoplanetary disks display a large variety of structures in recently published high-spatial resolution images. However, the three-dimensional morphology of these disks is often difficult to infer from the two-dimensional projected images we observe. We aim to detect signatures of planet-disk interaction by studying the scattering surface of the protoplanetary disk around HD34282 We spatially resolved the disk using the high-contrast imager VLT/SPHERE in polarimetric imaging mode. We retrieved a profile for the height of the scattering surface to create a height-corrected deprojection, which simulates a face-on orientation. The detected disk displays a complex scattering surface. An inner clearing or cavity extending up to r<0.28" (88au) is surrounded by a bright inclined (i=56{deg}) ring with a position angle of 119{deg}. The center of this ring is offset from the star along the minor axis with 0.07", which can be explained with a disk height of 26au above the midplane. Outside this ring, beyond its southeastern ansa we detect an azimuthal asymmetry or blob at r~0.4". At larger separation, we detect an outer disk structure that can be fitted with an ellipse, which is compatible with a circular ring seen at r=0.62" (=190au) and a height of 77au. After applying a height-corrected deprojection we see a circular ring centered on the star at 88 au; what had seemed to be a separate blob and outer ring could now both be part of a single-armed spiral. We present the first scattered-light image of the disk around HD 34282 and resolve a disk with an inner cavity up to r~90au and a highly structured scattering surface of an inclined disk at a large height H_scat_/r=0.29" above the midplane at the inner edge of the outer disk. Based on the current data it is not possible to conclude decisively whether H_scat_/r remains constant or whether the surface is flared with at most H_scat_ {prop.to} r^1.35^, although we favor the constant ratio based on our deprojections. The height-corrected deprojection allows for a more detailed interpretation of the observed structures, from which we discern the first detection of a single-armed spiral in a protoplanetary disk.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/124/1670
- Title:
- Post-T Tauri Stars in Sco-Cen Association
- Short Name:
- J/AJ/124/1670
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a spectroscopic survey of X-ray and proper-motion-selected samples of late-type stars in the Lower Centaurus-Crux (LCC) and Upper Centaurus-Lupus (UCL) subgroups of the nearest OB association: Scorpius-Centaurus. The primary goals of the survey are to determine the star formation history of the OB subgroups and to assess the frequency of accreting stars in a sample dominated by "post-T Tauri" pre-main-sequence (PMS) stars. We investigate two samples: (1) proper-motion candidates from the ACT Catalog (<I/246>) and Tycho Reference Catalog (TRC, <I/250>) with X-ray counterparts in the ROSAT All-Sky Survey (RASS) Bright Source Catalog and (2) G- and K-type stars in the Hipparcos catalog found to be candidate members by de Zeeuw et al. (1999, Cat. <J/AJ/117/354>). We obtained optical spectra of 130 candidates with the Siding Spring 2.3m dual-beam spectrograph.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A46
- Title:
- Pre-main sequence evolutionary tracks
- Short Name:
- J/A+A/510/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields are at the heart of the observed stellar activity in late-type stars, and they are presumably generated by a dynamo mechanism at the interface layer (tachocline) between the radiative core and the base of the convective envelope. Since dynamo models are based on the interaction between differential rotation and convective motions, the introduction of rotation in the ATON 2.3 stellar evolutionary code allows for explorations regarding a physically consistent treatment of magnetic effects in stellar structure and evolution, even though there are formidable mathematical and numerical challenges involved.
- ID:
- ivo://CDS.VizieR/J/A+A/494/209
- Title:
- Pre-main sequence evolutionary tracks
- Short Name:
- J/A+A/494/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In close binary systems, the axial rotation and the mutual tidal forces of the component stars deform each other and destroy their spherical symmetry by means of the respective disturbing potentials. We present new models for low-mass, pre-main sequence stars that include the combined distortion effects of tidal and rotational forces on the equilibrium configuration of stars. Using our theoretical results, we aim at investigating the effects of interaction between tides and rotation on the stellar structure and evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/806
- Title:
- Pre-main-sequence isochrones. II. SFR
- Short Name:
- J/MNRAS/434/806
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived ages for 13 young (<30Myr) star-forming regions and find that they are up to a factor of 2 older than the ages typically adopted in the literature. This result has wide-ranging implications, including that circumstellar discs survive longer (=~10-12Myr) and that the average Class I lifetime is greater (=~1Myr) than currently believed. For each star-forming region, we derived two ages from colour-magnitude diagrams. First, we fitted models of the evolution between the zero-age main sequence and terminal-age main sequence to derive a homogeneous set of main-sequence ages, distances and reddenings with statistically meaningful uncertainties. Our second age for each star-forming region was derived by fitting pre-main-sequence stars to new semi-empirical model isochrones. For the first time (for a set of clusters younger than 50Myr), we find broad agreement between these two ages, and since these are derived from two distinct mass regimes that rely on different aspects of stellar physics, it gives us confidence in the new age scale. This agreement is largely due to our adoption of empirical colour-T_eff_ relations and bolometric corrections for pre-main-sequence stars cooler than 4000K. The revised ages for the star-forming regions in our sample are: ~2Myr for NGC 6611 (Eagle Nebula; M 16), IC 5146 (Cocoon Nebula), NGC 6530 (Lagoon Nebula; M 8) and NGC 2244 (Rosette Nebula); ~6Myr for {sigma} Ori, Cep OB3b and IC 348; ~10Myr for {lambda} Ori (Collinder 69); ~11Myr for NGC 2169; ~12Myr for NGC 2362; ~13Myr for NGC 7160; ~14Myr for {chi}Per (NGC 884); and ~20Myr for NGC 1960 (M 36).
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/3178
- Title:
- Pre-main-sequence isochrones. Pleiades benchmark
- Short Name:
- J/MNRAS/424/3178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a critical assessment of commonly used pre-main-sequence isochrones by comparing their predictions to a set of well-calibrated colour-magnitude diagrams of the Pleiades in the wavelength range 0.4-2.5um. Our analysis shows that for temperatures less than 4000K, the models systematically overestimate the flux by a factor of 2 at 0.5um, though this decreases with wavelength, becoming negligible at 2.2um. In optical colours this will result in the ages for stars younger than 10Myr being underestimated by factors of between 2 and 3. We show that using observations of standard stars to transform the data into a standard system can introduce significant errors in the positioning of pre-main sequences in colour-magnitude diagrams. Therefore, we have compared the models to the data in the natural photometric system in which the observations were taken. Thus we have constructed and tested a model of the system responses for the Wide-Field Camera on the Isaac Newton Telescope. As a benchmark test for the development of pre-main-sequence models, we provide both our system responses and the Pleiades sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A49
- Title:
- Pre-main sequence stars evolutionary models
- Short Name:
- J/A+A/599/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Protostars grow from the first formation of a small seed and subsequent accretion of material. Recent theoretical work has shown that the pre-main-sequence (PMS) evolution of stars is much more complex than previously envisioned. Instead of the traditional steady, one-dimensional solution, accretion may be episodic and not necessarily symmetrical, thereby affecting the energy deposited inside the star and its interior structure. Given this new framework, we want to understand what controls the evolution of accreting stars. We use the MESA stellar evolution code with various sets of conditions. In particular, we account for the (unknown) efficiency of accretion in burying gravitational energy into the protostar through a parameter, ksi, and we vary the amount of deuterium present. We confirm the findings of previous works that, in terms of evolutionary tracks on an Hertzprung-Russell (H-R) diagram, the evolution changes significantly with the amount of energy that is lost during accretion. We find that deuterium burning also regulates the PMS evolution. In the low-entropy accretion scenario, the evolutionary tracks in the H-R diagram are significantly different from the classical tracks and are sensitive to the deuterium content. A comparison of theoretical evolutionary tracks and observations allows us to exclude some cold accretion models (ksi~0) with low deuterium abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A132
- Title:
- Pre-main sequence stars evolutionary models. II
- Short Name:
- J/A+A/618/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We want to investigate how planet formation is imprinted on stellar surface composition using up-to-date stellar evolution models. We simulate the evolution of pre-main-sequence stars as a function of the efficiency of heat injection during accretion, the deuterium mass fraction, and the stellar mass, M*. For simplicity, we assume that planet formation leads to the late accretion of zero-metallicity gas, diluting the surface stellar composition as a function of the mass of the stellar outer convective zone. We estimate that in the solar system, between 97 and 168 Mearth of condensates formed planets or were ejected from the system. We adopt 150 M_earth_(M*/M_sun_)(Z/Z_sun_) as an uncertain but plausible estimate of the mass of heavy elements that is not accreted by stars with giant planets, including our Sun. By combining our stellar evolution models to these estimates, we evaluate the consequences of planet formation on stellar surface compositions. We show that after the first ~0.1 million years (Myr) during which stellar structure can differ widely from the usually assumed fully-convective structure, the evolution of the convective zone follows classical pre-main-sequence evolutionary tracks within a factor of two in age. We find that planet formation should lead to a scatter in stellar surface composition that is larger for high-mass stars than for low-mass stars. We predict a spread in [Fe/H] of approximately 0.05dex for stars of temperature Teff~6500K, to 0.02dex for Teff~5500K, marginally compatible with differences in metallicities observed in some binary stars with planets. Stars with Teff>=7000K may show much larger [Fe/H] deficits, by 0.6dex or more, in the presence of efficient planet formation, compatible with the existence of refractory-poor lambda Boo stars. We also find that planet formation may explain the lack of refractory elements seen in the Sun as compared to solar twins, but only if the ice-to-rock ratio in the solar-system planets is less than ~0.4 and planet formation began less than ~1.3Myr after the beginning of the formation of the Sun.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/480
- Title:
- Pre-main-sequence stars in Lupus association
- Short Name:
- J/ApJ/658/480
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kinematical analysis of spectroscopically identified pre-main-sequence stars associated with the Lupus dark cloud reveals a streamlike motion of low internal velocity dispersion (<=1.3km/s). A statistically significant mismatch between the convergent point radial velocity and the spectroscopic radial velocity from the literature indicates a moderate degree of expansion. The rate of expansion is too low to account for the present extent of the association if one assumes that the spatially dispersed population was formed in the dense molecular cores observed today. Therefore, it is unlikely that the outlying weak-lined T Tauri members were born in the same star-forming cores as the more compactly located classical T Tauri stars, despite the kinematic integrity of the association. Distances inferred from the classical moving-cluster method show a large depth of the association (~80pc) along the line of sight. A color-magnitude diagram of the association in the near-IR colors corrected for the distribution of distances shows a clear gap separating the older (5-27Myr) and the younger (~1Myr) generations of stars. Half of the identified 1Myr old stars lie in the tight group of mostly classical T Tauri stars associated with the Lupus 3 dark filament. This nest of very young stars appears to be 25pc farther from the Sun than the center of the greater Lupus association.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A148
- Title:
- Pre-main sequence stars in Scorpius OB1
- Short Name:
- J/A+A/615/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The low-mass members of OB associations, expected to be a major component of their total population, are in most cases poorly studied because of the difficulty of selecting these faint stars in crowded sky regions. Our knowledge of many OB associations relies on only a relatively small number of massive members. We study here the Sco OB1 association, with the aim of a better characterization of its properties, such as global size and shape, member clusters and their morphology, age and formation history, and total mass. We use deep optical and near-infrared (NIR) photometry from the VPHAS+ and VVV surveys, over a wide area (2.6{deg}x2.6{deg}), complemented by Spitzer infrared (IR) data, and Chandra and XMM-Newton X-ray data. A new technique is developed to find clusters of pre-main sequence M-type stars using suitable color-color diagrams, complementing existing selection techniques using narrow-band H{alpha} photometry or NIR and ultraviolet (UV) excesses, and X-ray data. We find a large population of approximately 4000 candidate low-mass Sco OB1 members whose spatial properties correlate well with those of H{alpha}-emission, NIR-excess, UV-excess, and X-ray detected members, and unresolved X-ray emission. The low-mass population is spread among several interconnected subgroups: they coincide with the HII regions G345.45+1.50 and IC4628, and the rich clusters NGC 6231 and Trumpler 24, with an additional subcluster intermediate between these two. The total mass of Sco OB1 is estimated to be ~8500M_{sun}_. Indication of a sequence of star-formation events is found, from South (NGC 6231) to North (G345.45+1.50). We suggest that the diluted appearance of Trumpler 24 indicates that the cluster is now dissolving into the field, and that tidal stripping by NGC 6231 nearby contributes to the process.
