- ID:
- ivo://CDS.VizieR/J/A+A/622/A72
- Title:
- Intermediate-mass T Tau stars spectra
- Short Name:
- J/A+A/622/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated. We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determined fundamental stellar parameters (T_eff_, L and vsini) and measured surface magnetic field characteristics (including detection limits for non-detections, and longitudinal fields and basic topologies for positive detections). Using PMS evolutionary models, we determined the mass, radius, and internal structure of these stars. We compared different PMS models to check that our determinations were not model- dependant. We then compared the magnetic characteristics of our sample accounting for their stellar parameters and internal structures. Results: We detect magnetic fields in about half of our sample. About 90% of the magnetic stars have outer convective envelopes larger than ~25% of the stellar radii, and heavier than ~2% of the stellar mass. Going to higher mass, we find that the magnetic incidence in intermediate-mass stars drops very quickly, within a time-scale of the order of few times 0.1Myr. Finally, we propose that intermediate-mass T Tauri stars with large convective envelopes, close to the fully convective limit, have complex fields and that their dipole component strengths may decrease as the sizes of their convective envelopes decrease, similar to lower-mass T Tauri stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/124/445
- Title:
- Internal velocities in Orion Nebula
- Short Name:
- J/AJ/124/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The proper motions (tangential velocities) of Herbig-Haro (HH) objects in the Orion Nebula were measured with a +/-10km/s accuracy using the Hubble Space Telescope Wide Field Planetary Camera 2 images in [S II], [N II], H, and [O III], taken 4-6yr apart. Seven HH flows in the outer region as well as seven HH objects in the inner region of the BN-KL complex were identified. The H2 finger system was confirmed to be created by an explosive event that took place approximately 1000 yr ago. We found a new HH flow toward the northwest originating from the vicinity of OMC-1S, which may be a part of the low-velocity bipolar flows centered at FIR 4. The proper motion of HH 202 was also measured with high accuracy for the first time. The proper-motion vectors of HH 202 and HH 203/204 are aligned well with their projected symmetric axis, which may indicate that they emanated from the same source. The proper-motion measurements in various emission lines provide generally the same results in the wide range of velocity from 20 to 400km/s, as expected for shocks in a steady state.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3456
- Title:
- Internal velocities in the Orion Nebula
- Short Name:
- J/AJ/127/3456
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A map of high-velocity features in the 3'x5' central region of the Orion Nebula was created from slit spectra with a velocity resolution of 8km/s. Spatial velocities of 19 features belonging to 11 HH objects were obtained by combining these radial velocity data with existing proper motion data.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/9
- Title:
- Intrinsic colors and temperatures of PMS stars
- Short Name:
- J/ApJS/208/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the intrinsic colors and temperatures of 5-30 Myr old pre-main-sequence (pre-MS) stars using the F0- through M9-type members of nearby, negligibly reddened groups: the {eta} Cha cluster, the TW Hydra Association, the {beta} Pic Moving Group, and the Tucana-Horologium Association. To check the consistency of spectral types from the literature, we estimate new spectral types for 52 nearby pre-MS stars with spectral types F3 through M4 using optical spectra taken with the SMARTS 1.5 m telescope. Combining these new types with published spectral types and photometry from the literature (Johnson-Cousins BVI_C_, 2MASS JHK_S_ and WISE W1, W2, W3, and W4), we derive a new empirical spectral type-color sequence for 5-30 Myr old pre-MS stars. Colors for pre-MS stars match dwarf colors for some spectral types and colors, but for other spectral types and colors, deviations can exceed 0.3 mag. We estimate effective temperatures (T_eff_) and bolometric corrections (BCs) for our pre-MS star sample through comparing their photometry to synthetic photometry generated using the BT-Settl grid of model atmosphere spectra. We derive a new T_eff_ and BC scale for pre-MS stars, which should be a more appropriate match for T Tauri stars than often-adopted dwarf star scales. While our new T_eff_ scale for pre-MS stars is within =~100K of dwarfs at a given spectral type for stars <G5, for G5 through K6, the pre-MS stars are ~250 K cooler than their MS counterparts. Lastly, we present (1) a modern T_eff_, optical/IR color, and BC sequence for O9V-M9V MS stars based on an extensive literature survey, (2) a revised Q-method relation for dereddening UBV photometry of OB-type stars, and (3) introduce two candidate spectral standard stars as representatives of spectral types K8V and K9V.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/103
- Title:
- IPHAS T Tauri candidates in IC 1396
- Short Name:
- J/MNRAS/415/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Isaac Newton Telescope (INT) Photometric H-Alpha Survey (IPHAS) is a 1800deg^2^ survey of the Northern Galactic Plane, reaching down to r'~21. We demonstrate how the survey can be used to (1) reliably select classical T Tauri star candidates and (2) constrain the mass accretion rates with an estimated relative uncertainty of 0.6dex. IPHAS is a necessary addition to spectroscopic surveys because it allows large and uniform samples of accretion rates to be obtained with a precise handle on the selection effects. We apply the method on a region of 7deg^2^ towards the HII region IC 1396 in Cepheus OB2 and identify 158 pre-main-sequence candidates with masses between 0.2 and 2.0M_{sun}_ and accretion rates between 10-9.2 and 10-7.0M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/A+A/502/883
- Title:
- I photometry of very low mass ONC stars
- Short Name:
- J/A+A/502/883
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotational studies at a variety of ages and masses are important for constraining the angular momentum evolution of young stellar objects (YSO). Of particular interest are the very low mass (VLM) stars and brown dwarfs (BDs), because of the significant lack of known rotational periods in that mass range. We aim to extend previous studies well down into the substellar regime, providing for the first time information on rotational periods for a large sample of young VLM stars and BDs. This extensive rotational period study of YSOs in the 1 Myr old Orion Nebula Cluster (ONC) is based on a deep photometric monitoring campaign using the Wide Field Imager (WFI) camera on the ESO/MPG 2.2m telescope on La Silla, Chile. Time series data was obtained with about 95 data points spread over 19 nights. Accurate I-band photometry of 2908 stars was obtained within a magnitude range of 13 to 21mag, i.e. extending three magnitudes deeper than previous studies in the ONC. Two different power spectral analysis techniques were used to search for periodic variability. In addition, the chi^2^ variability test was used for the detection of irregular variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/675/1375
- Title:
- IRAC/MIPS photometry in Cha I
- Short Name:
- J/ApJ/675/1375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of circumstellar disks in the Chamaeleon I star-forming region. Using the Infrared Array Camera and the Multiband Imaging Photometer on board the Spitzer Space Telescope, we have obtained images of Chamaeleon I at 3.6, 4.5, 5.8, 8.0, and 24um. To search for new disk-bearing members of the cluster, we have performed spectroscopy on objects that have red colors in these data. Through this work, we have discovered four new members of Chamaeleon I with spectral types of M4, M6, M7.5, and L0.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/1170
- Title:
- IRAC photometry of M8
- Short Name:
- J/MNRAS/407/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry and images (3.6, 4.5, 5.8 and 8.0um) from the Spitzer Infrared Array Camera (IRAC) of the star-forming region Messier 8 (M8). The IRAC photometry reveals ongoing star formation in the M8 complex, with 64 class 0/I and 168 class II sources identified in several locations in the vicinity of submm gas cores/clumps.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A38
- Title:
- IRAS05168+3634 star-forming region stellar content
- Short Name:
- J/A+A/622/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aims. We report the investigation results of the structure and content of a molecular cloud surrounding the source IRAS 05168+3634 (also known as Mol 9). Methods. We present a photometric analysis using the data of J, H, K UKIDSS, [3.6], [4.5]{mu}m Spitzer-IRAC and 3.4, 4.6, 12, 22{mu}m WISE databases. A multi-color criteria was used to identify the candidates of young stellar objects (YSOs) in the molecular cloud; in addition to IRAS 05168+3634, there are four IRAS sources embedded in the same molecular cloud. Color-magnitude diagrams and the K luminosity function (KLF) were used to determine the basic parameters of stellar objects (spectral classes, masses, ages). To study the YSOs with longer wavelength photometry the radiative transfer models were used. Results. Based on color-color and color-magnitude diagrams, we identified a rich population of embedded YSO candidates with infrared excess (Class 0/I and Class II) and their characteristics in a quite large molecular cloud located in a region of 24 arcmin radius. The molecular cloud includes 240 candidates of YSOs within the radii of subregions around five IRAS sources. The local distribution of identified YSOs in the molecular cloud frequently shows elongation and subclustering. The observed young subregions and parental molecular cloud morphologies are similar, especially when only the youngest Class I/0 sources are considered. The color-magnitude diagrams of the subregions suggest a very young stellar population. We construct the KLF of the subregions except for the IRAS 05162+3639 region and it shows unusually low values for {alpha} slope: 0.12-0.21. According to the values of the slopes of the KLFs, the age of the subregions can be estimated at 0.1-3Myr. The spectral energy distributions (SEDs) are constructed for 45 Class I and 75 Class II evolutionary stage YSOs and the received parameters of these YSOs are well correlated with the results obtained by other methods. According to the results of SED fitting tool, the sources IRAS 05184+3635, IRAS 05177+3636, and IRAS 05162+3639 can be classified as Class I evolutionary stage objects. IRAS 05168+3634 and IRAS 05156+3643 can be classified as flat-spectrum objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/555/932
- Title:
- IR fluxes of solar-type stars
- Short Name:
- J/ApJ/555/932
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using ISO-ISOPHOT, we carried out a survey of almost 150 stars to search for evidence of emission from dust orbiting young main-sequence stars, both in clusters and isolated systems. Over half of the detections are new examples of dusty stellar systems and demonstrate that such dust can be detected around numerous stars older than a few times 10^6^yr. Fluxes at 60 and either 90 or 100{mu}m or the new excess sources together with improved fluxes for a number of IRAS-identified sources are presented. Analysis of the excess luminosity relative to the stellar photosphere shows a systematic decline of this excess with stellar age consistent with a power-law index of -2.
