- ID:
- ivo://CDS.VizieR/J/ApJ/755/154
- Title:
- Mass accretion rates from HST in the ONC
- Short Name:
- J/ApJ/755/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present observational understanding of the evolution of the mass accretion rates (dM/dt_acc_) in pre-main-sequence stars is limited by the lack of accurate measurements of dM/dt_acc_ over homogeneous and large statistical samples of young stars. Such observational effort is needed to properly constrain the theory of star formation and disk evolution. Based on Hubble Space Telescope/WFPC2 observations, we present a study of dM/dt_acc_ for a sample of ~700 sources in the Orion Nebula Cluster, ranging from the hydrogen-burning limit to M*~2M_{sun}_. We derive dM/dt_acc_ from both the U-band excess and the H{alpha} luminosity (L_H{alpha}_), after determining empirically both the shape of the typical accretion spectrum across the Balmer jump and the relation between the accretion luminosity (L_acc_) and L_H{alpha}_, which is L_acc_/L_{sun}_=(1.31+/-0.03).L_H{alpha}/L_{sun}_+(2.63+/-0.13). Given our large statistical sample, we are able to accurately investigate relations between dM/dt_acc_ and the parameters of the central star such as mass and age.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/875/51
- Title:
- Mass accretion rates of PMS stars. VI. LH95 in LMC
- Short Name:
- J/ApJ/875/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband H{alpha} photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing H{alpha} excess emission above the 4{sigma} level. We derive their physical parameters, including effective temperatures, luminosities, masses (M_*_), ages, accretion luminosities, and mass accretion rates (dM/dt_acc_). We identify two different stellar populations: younger than ~8Myr with median dM/dt_acc_~5.4x10^-8^M_{sun}_/yr (and M_*_~0.15-1.8M_{sun}_) and older than ~8Myr with median dM/dt_acc_~4.8x10^-9^M_{sun}_/yr (and M_*_~0.6-1.2M_{sun}_). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that dM/dt_acc_ in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The dM/dt_acc_-M_*_ relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on dM/dt_acc_ cannot be treated independently. With the aim to identify reliable correlations between mass, age, and dM/dt_acc_, we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the dM/dt_acc_ evolution in clusters with different environmental conditions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/1157
- Title:
- Members of ONC and Tau-Aur
- Short Name:
- J/MNRAS/444/1157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In light of recent substantial updates to spectral type estimations and newly established intrinsic colours, effective temperatures, and bolometric corrections for pre-main sequence (PMS) stars, we re-address the theory of accretion disc-regulated stellar angular momentum (AM) evolution. We report on the compilation of a consistent sample of fully convective stars within two of the most well-studied and youngest, nearby regions of star formation: the Orion nebula Cluster and Taurus-Auriga. We calculate the average specific stellar AM (j*) assuming solid body rotation, using surface rotation periods gathered from the literature and new estimates of stellar radii and ages. We use published Spitzer IRAC fluxes to classify our stars as Class II or Class III and compare their j_*_ evolution. Our results suggest that disc dispersal is a rapid process that occurs at a variety of ages. We find a consistent j_*_ reduction rate between the Class II and Class III PMS stars which we interpret as indicating a period of accretion disc-regulated AM evolution followed by near-constant AM evolution once the disc has dissipated. Furthermore, assuming our observed spread in stellar ages is real, we find that the removal rate of j_*_ during the Class II phase is more rapid than expected by contraction at constant stellar rotation rate. A much more efficient process of AM removal must exist, most likely in the form of an accretion-driven stellar wind or other outflow from the star-disc interaction region or extended disc surface.
- 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/A+A/452/245
- Title:
- Near-IR photometry of PMS stars in rho Oph
- Short Name:
- J/A+A/452/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to provide a measurement of the mass accretion rate in a large, complete sample of objects in the core of the star forming region rho Oph. The sample includes most of the objects (104 out of 111) with evidence of a circumstellar disk from mid-infrared photometry; it covers a stellar mass range from about 0.03 to 3M_{sun}_ and it is complete to a limiting mass of ~0.05M_{sun}_. We used J and K-band spectra to derive the mass accretion rate of each object from the intensity of the hydrogen recombination lines, Pa{beta} or Br{gamma}. For comparison, we also obtained similar spectra of 35 diskless objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/484/5102
- Title:
- NGC 6383 T Tauri accretion rates
- Short Name:
- J/MNRAS/484/5102
- Date:
- 03 Nov 2021 13:02:39
- Publisher:
- CDS
- Description:
- This paper presents optical (ugriH{alpha})-infrared (JHKs, 3.6-8.0um) photometry and Gaia astrometry of 55 Classical T-Tauri stars (CTTS) in the star-forming region Sh 2-012 and its central cluster NGC 6383. The sample was identified based on photometric H{alpha} emission linewidths, and has a median age of 2.8+/-1.6Myr, with a mass range between 0.3 and 1M_{sun}_. 94 per cent of CTTS with near-infrared cross-matches fall on the near-infrared T-Tauri locus, with all stars having mid-infrared photometry exhibiting evidence for accreting circumstellar discs. CTTS are found concentrated around the central cluster NGC 6383, and towards the bright rims located at the edges of Sh 2-012. Stars across the region have similar ages, suggestive of a single burst of star formation. Mass accretion rates dMacc/dt) estimated via H{alpha} and u-band line intensities show a scatter (0.3dex) similar to spectroscopic studies, indicating the suitability of H{alpha} photometry to estimate dMacc/dt. Examining the variation of dMacc/dt with stellar mass (M*), we find a smaller intercept in the (dMacc/dt)-M* relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/483/5554
- Title:
- Non-nuclear X-ray sources in nearby galaxies
- Short Name:
- J/MNRAS/483/5554
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have created a new, clean catalogue of extragalactic non-nuclear X-ray sources by correlating the 3XMM-DR4 data release of the XMM-Newton Serendipitous Source Catalogue with the Third Reference Catalogue of Bright Galaxies and the Catalogue of Neighbouring Galaxies, using an improved version of the method presented in Walton et al. (2011MNRAS.416.1844W, Cat. J/MNRAS/416/1844). Our catalogue contains 1314 sources, of which 384 are candidate ultraluminous X-ray sources (ULXs). The resulting catalogue improves upon previous catalogues in its handling of spurious detections by taking into account XMM-Newton quality flags. We estimate the contamination of ULXs by background sources to be 24 per cent. We define a 'complete' subsample as those ULXs in galaxies for which the sensitivity limit is below 10^39^erg/s and use it to examine the hardness ratio properties between ULX and non-ULX sources, and ULXs in different classes of host galaxy. We find that ULXs have a similar hardness ratio distribution to lower-luminosity sources, consistent with previous studies. We also find that ULXs in spiral and elliptical host galaxies have similar distributions to each other independent of host galaxy morphology, however our results do support previous indications that the population of ULXs is more luminous in star-forming host galaxies than in non-star-forming galaxies. Our catalogue contains further interesting subpopulations for future study, including Eddington Threshold sources and highly variable ULXs. We also examine the highest-luminosity (L_X_ >5x10^40^erg/s) ULXs in our catalogue in search of intermediate-mass black hole candidates, and find nine new possible candidates
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/4441
- Title:
- Outburst catalogue of cataclysmic variables
- Short Name:
- J/MNRAS/456/4441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Outburst Catalogue contains a wide variety of observational properties for 722 dwarf nova-type (DN) cataclysmic variables (CVs) and 309 CVs of other types from the Catalina Real-time Transient Survey. In particular, it includes the apparent outburst and quiescent V-band magnitudes, duty cycles, limits on the recurrence time, upper- and lower-limits on the distance and absolute quiescent magnitudes, colour information, orbital parameters, and X-ray counterparts. These properties were determined by means of a classification script presented in this paper. The DN in the catalogue show a correlation between the outburst duty cycle and the orbital period (and outburst recurrence time), as well as between the quiescent absolute magnitude and the orbital period (and duty cycle). This is the largest sample of dwarf nova properties collected to date. Besides serving as a useful reference for individual systems and a means of selecting objects for targeted studies, it will prove valuable for statistical studies that aim to shed light on the formation and evolution of cataclysmic variables.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/451
- Title:
- PMS stars in the Cepheus flare region
- Short Name:
- J/ApJS/185/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of optical spectroscopic and BVR_C_I_C_ photometric observations of 77 pre-main-sequence (PMS) stars in the Cepheus flare region. A total of 64 of these are newly confirmed PMS stars, originally selected from various published candidate lists. We estimate effective temperatures and luminosities for the PMS stars, and comparing the results with PMS evolutionary models, we estimate stellar masses of 0.2-2.4M_{sun}_ and stellar ages of 0.1-15Myr. Among the PMS stars, we identify 15 visual binaries with separations of 2-10". From archival IRAS, Two Micron All Sky Survey, and Spitzer data, we construct their spectral energy distributions (SEDs) and classify 5% of the stars as Class I, 10% as Flat SED, 60% as Class II, and 3% as Class III young stellar objects. We identify 12 classical T Tauri stars and two weak-line T Tauri stars as members of NGC 7023, with a mean age of 1.6Myr. The 13 PMS stars associated with L1228 belong to three small aggregates: RNO 129, L1228A, and L1228S. The age distribution of the 17 PMS stars associated with L1251 suggests that star formation has propagated with the expansion of the Cepheus flare shell. We detect sparse aggregates of ~6-7Myr old PMS stars around the dark clouds L1177 and L1219, at a distance of ~400pc. Three T Tauri stars appear to be associated with the Herbig Ae star SV Cep at a distance of 600pc. Our results confirm that the molecular complex in the Cepheus flare region contains clouds of various distances and star-forming histories.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/31
- Title:
- Protoplanetary disk data in Cha I and Lupus
- Short Name:
- J/ApJ/847/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we investigate the relation between disk mass and mass accretion rate to constrain the mechanism of angular momentum transport in protoplanetary disks. We find a correlation between dust disk mass and mass accretion rate in Chamaeleon I with a slope that is close to linear, similar to the one recently identified in Lupus. We investigate the effect of stellar mass and find that the intrinsic scatter around the best-fit M_dust_-M_*_ and dM_acc_/dt-M_*_ relations is uncorrelated. We simulate synthetic observations of an ensemble of evolving disks using a Monte Carlo approach and find that disks with a constant {alpha} viscosity can fit the observed relations between dust mass, mass accretion rate, and stellar mass but overpredict the strength of the correlation between disk mass and mass accretion rate when using standard initial conditions. We find two possible solutions. In the first one, the observed scatter in M_dust_ and dM_acc_/dt is not primordial, but arises from additional physical processes or uncertainties in estimating the disk gas mass. Most likely grain growth and radial drift affect the observable dust mass, while variability on large timescales affects the mass accretion rates. In the second scenario, the observed scatter is primordial, but disks have not evolved substantially at the age of Lupus and Chamaeleon I owing to a low viscosity or a large initial disk radius. More accurate estimates of the disk mass and gas disk sizes in a large sample of protoplanetary disks, through either direct observations of the gas or spatially resolved multiwavelength observations of the dust with ALMA, are needed to discriminate between both scenarios or to constrain alternative angular momentum transport mechanisms such as MHD disk winds.
