- ID:
- ivo://CDS.VizieR/J/ApJ/636/932
- Title:
- Mid-infrared survey of T Tauri stars
- Short Name:
- J/ApJ/636/932
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high spatial resolution, 10-20{mu}m survey of 65 T Tauri binary stars in Taurus, Ophiuchus, and Corona Australis using the Keck 10m telescopes. Designed to probe the inner ~1AU region of the circumstellar disks around the individual stellar components in these binary systems, this study increases the number of binaries with spatially resolved measurements at 10{mu}m by a factor of ~5.
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- ID:
- ivo://CDS.VizieR/J/ApJ/630/381
- Title:
- Mid-IR imaging in {rho} Oph
- Short Name:
- J/ApJ/630/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a comprehensive, new, ground-based mid-infrared imaging survey of the young stellar population of the {rho} Ophiuchi cloud are presented. Data were acquired at the Palomar 5m and at the Keck 10m telescopes with the MIRLIN (Mid-InfraRed Large-well Imager) and LWS (Long Wavelength Spectrometer centered at 12.5{mu}m) instruments, at 0.5" and 0.25" resolutions, respectively. Of 172 survey objects, 85 were detected. Among the 22 multiple systems observed, 15 were resolved and their individual component fluxes determined.
- ID:
- ivo://CDS.VizieR/J/ApJ/676/427
- Title:
- MIPS and IRAC data on ChaII PMS stars
- Short Name:
- J/ApJ/676/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and NIR data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population in an area of ~1.75deg^2^ and study the spatial distribution and properties of the cloud members and candidate pre-main-sequence (PMS) objects and their circumstellar matter. Our census is complete down to the substellar regime (M~0.03M_{sun}).
- ID:
- ivo://CDS.VizieR/J/A+A/533/A121
- Title:
- Missing low-mass stars in S254-S258
- Short Name:
- J/A+A/533/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study was to find an explanation for the remarkable morphology of the central part of the S254-S258 star forming complex. We performed a deep Chandra X-ray observation of the S254-S258 region in order to efficiently discriminate young stars (with and without circumstellar matter) from the numerous older field stars in the area. We detected 364 X-ray point sources in a 17'x17' field. This X-ray catalog provides, for the first time, a complete sample of all young stars in the region down to about 0.5M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A50
- Title:
- 1.3mm and 3mm emission maps or 4 Ae/Be stars
- Short Name:
- J/A+A/531/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Herbig Ae stars (HAe) are the precursors of Vega-type systems and, therefore, crucial objects in planet formation studies. Thus far, only a few disks associated with HAe stars have been studied using millimetre interferometers. Our aim is to determine the dust evolution and the lifetime of the disks associated with Herbig Ae stars. We imaged the continuum emission at ~3mm and ~1.3mm of the Herbig Ae/Be stars BD+61154, RR Tau, VY Mon and LkH{alpha} 198 using the Plateau de Bure Interferometer (PdBI). These stars are in the upper end of the stellar mass range of the Herbig Ae stars (M_*_>3M_{sun}_). Our measurements were used to complete the Spectral Energy Distribution (SED). The modelling of the SED, in particular the FIR-mm part, allow us to determine the masses and dust properties of these disks. We detected the disks associated with BD+61154, RR Tau and VY Mon with disk masses of 0.35M_{sun}_, 0.05M_{sun}_ and 0.40M_{sun}_ respectively. The disk around LkH{alpha} 198 was not detected with an upper limit to the disk mass of 0.004M_{sun}_. We detected, however, the disks associated with the younger stellar objects LkH{alpha} 198--IR and LkH{alpha} 198--mm that are located in the vicinity of LkH{alpha} 198. The fitting of the mm part of the SED reveal that the grains in the mid-plane of the disks around BD+61154, RR Tau and VY Mon have sizes of ~1-1000um. Therefore, grains have not grown to centimetre sizes in these disks yet. These massive (M_*_>3M_{sun}_) and young (~1Myr) HAe stars are surrounded by massive (>~0.04M_{sun}_) disks with grains of micron-millimetre sizes. Although grain growth is proceeding in these disks, their evolutionary stage is prior to the formation of planetesimals. These disks are less evolved than those detected around T Tauri and Herbig Be stars.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A78
- Title:
- M17 massive pms stars X-shooter spectra
- Short Name:
- J/A+A/604/A78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation process of massive stars is still poorly understood. Massive young stellar objects (mYSOs) are deeply embedded in their parental clouds; these objects are rare, and thus typically distant, and their reddened spectra usually preclude the determination of their photospheric parameters. M17 is one of the best-studied HII regions in the sky, is relatively nearby, and hosts a young stellar population. We have obtained optical to near-infrared spectra of previously identified candidate mYSOs and a few OB stars in this region with X-shooter on the ESO Very Large Telescope. The large wavelength coverage enables a detailed spectroscopic analysis of the photospheres and circumstellar disks of these candidate mYSOs. We confirm the pre-main-sequence (PMS) nature of six of the stars and characterise the O stars. The PMS stars have radii that are consistent with being contracting towards the main sequence and are surrounded by a remnant accretion disk. The observed infrared excess and the double-peaked emission lines provide an opportunity to measure structured velocity profiles in the disks. We compare the observed properties of this unique sample of young massive stars with evolutionary tracks of massive protostars and propose that these mYSOs near the western edge of the HII region are on their way to become main-sequence stars (~6-20M_{sun}_) after having undergone high mass accretion rates (dMacc/dt~10^-4^-10^-3^M_{sun}_/yr) Their spin distribution upon arrival at the zero age main-sequence (ZAMS) is consistent with that observed for young B stars, assuming conservation of angular momentum and homologous contraction.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A51
- Title:
- 3mm maps of 4 transition disks
- Short Name:
- J/A+A/564/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transition disks are protoplanetary disks with inner depleted dust cavities and excellent candidates to investigate the dust evolution under the existence of a pressure bump. A pressure bump at the outer edge of the cavity allows dust grains from the outer regions to stop their rapid inward migration towards the star and efficiently grow to millimetre sizes. Dynamical interactions with planet(s) have been one of the most exciting theories to explain the clearing of the inner disk. We look for evidence of the presence of millimetre dust particles in transition disks by measuring their spectral index {alpha}_mm_ with new and available photometric data. We investigate the influence of the size of the dust depleted cavity on the disk integrated millimetre spectral index. We present the 3-millimetre (100GHz) photometric observations carried out with Plateau de Bure Interferometer of four transition disks: LkH{alpha} 330, UX Tau A, LRLL 31, and LRLL 67. We use available values of their fluxes at 345GHz to calculate their spectral index, as well as the spectral index for a sample of twenty transition disks. We compare the observations with two kind of models. In the first set of models, we consider coagulation and fragmentation of dust in a disk in which a cavity is formed by a massive planet located at different positions. The second set of models assumes disks with truncated inner parts at different radius and with power-law dust size distributions, where the maximum size of grains is calculated considering turbulence as the source of destructive collisions. We show that the integrated spectral index is higher for transition disks (TD) than for regular protoplanetary disks (PD) with mean values of <{alpha}_mm_^TD^>=2.70+/-0.13 and <{alpha}_mm_^PD^>=2.20+/-0.07 respectively. For transition disks, the probability that the measured spectral index is positively correlated with the cavity radius is 95%. High angular resolution imaging of transition disks is needed to distinguish between the dust trapping scenario and the truncated disk case.
- ID:
- ivo://CDS.VizieR/J/MNRAS/384/675
- Title:
- Monitoring low-mass stars in NGC 2362
- Short Name:
- J/MNRAS/384/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of a time-series photometric survey of NGC 2362, carried out using the CTIO 4-m Blanco telescope and Mosaic-II detector as part of the Monitor project. Rotation periods were derived for 271(*) candidate cluster members over the mass range 0.1~<M/M_{sun}_<~1.2. The rotation period distributions show a clear mass-dependent morphology, qualitatively similar to that in NGC 2264, as would be expected from the age of this cluster. Using models of angular momentum evolution, we show that angular momentum losses over the ~1-5Myr age range appear to be needed in order to reproduce the evolution of the slowest rotators in the sample from the ONC to NGC 2362, as found by many previous studies. By incorporating Spitzer IRAC mid-infrared (mid-IR) measurements, we found that three to four objects showing mid-IR excesses indicative of the presence of circumstellar discs were all slow rotators, as would be expected in the disc regulation paradigm for early pre-main-sequence angular momentum evolution, but this result is not statistically significant at present, given the extremely limited sample size. (*) The abstract indicates 271 clusters, but the actual number is 272.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/83
- Title:
- Multiple star formation in Ophiuchus
- Short Name:
- J/ApJ/813/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a multiplicity survey of members of the {rho} Ophiuchus cloud complex with high-resolution imaging to characterize the multiple-star population of this nearby star-forming region and investigate the relation between stellar multiplicity and star and planet formation. Our aperture masking survey reveals the presence of five new stellar companions beyond the reach of previous studies, but does not result in the detection of any new substellar companions. We find that 43+/-6% of the 114 stars in our survey have stellar-mass companions between 1.3 and 780 AU, while 7_-5_^+8^% host brown dwarf companions in the same interval. By combining this information with knowledge of disk-hosting stars, we show that the presence of a close binary companion (separation <40AU) significantly influences the lifetime of protoplanetary disks, a phenomenon previously seen in older star-forming regions. At the ~1-2Myr age of our Ophiuchus members ~2/3 of close binary systems have lost their disks, compared to only ~30% of single stars and wide binaries. This has a significant impact on the formation of giant planets, which are expected to require much longer than 1 Myr to form via core accretion and thus planets formed via this pathway should be rare in close binary systems.
- ID:
- ivo://CDS.VizieR/J/AJ/144/101
- Title:
- Multiwavelength data of IRAS 20050+2720 young SFR
- Short Name:
- J/AJ/144/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 20050+2720 is young star-forming region at a distance of 700pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N_H_/A_K_ ratio compared with the diffuse interstellar medium.
