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421. 36 accreting YSOs emission lines
ID:
ivo://CDS.VizieR/J/A+A/561/A2
Title:
36 accreting YSOs emission lines
Short Name:
J/A+A/561/A2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VLT/X-shooter observations of a sample of 36 accreting low-mass stellar and substellar objects (YSOs) in the Lupus star-forming region, spanning a range in mass from ~0.03 to ~1.2M_{sun}_, but mostly with 0.1M_{sun}_<M*<0.5M_{sun}_. Our aim is twofold: firstly, to analyse the relationship between excess-continuum and line emission accretion diagnostics, and, secondly, to investigate the accretion properties in terms of the physical properties of the central object. The accretion luminosity (L_acc_), and in turn the accretion rate (dM/dt_acc_), was derived by modelling the excess emission from the UV to the near-infrared as the continuum emission of a slab of hydrogen. We computed the flux and luminosity (L_line_) of many emission lines of H, He, and CaII, observed simultaneously in the range from ~330nm to 2500nm.
422. Accretion history of massive stars
ID:
ivo://CDS.VizieR/J/MNRAS/496/3482
Title:
Accretion history of massive stars
Short Name:
J/MNRAS/496/3482
Date:
21 Oct 2021
Publisher:
CDS
Description:
The mass growth of protostars is a central element to the determination of fundamental stellar population properties such as the initial mass function. Constraining the accretion history of individual protostars is therefore an important aspect of star formation research. The goal of the study presented here is to determine whether high-mass (proto)stars gain their mass from a compact (<0.1pc) fixed-mass reservoir of gas, often referred to as dense cores, in which they are embedded, or whether the mass growth of high-mass stars is governed by the dynamical evolution of the parsec-scale clump that typically surrounds them. To achieve this goal, we performed a 350micron continuum mapping of 11 infrared dark clouds, along side some of their neighbouring clumps, with the ArTeMiS camera on APEX. By identifying about 200 compact ArTeMiS sources, and matching them with Herschel Hi-GAL 70micron sources, we have been able to produce mass vs. temperature diagrams. We compare the nature (i.e. starless or protostellar) and location of the ArTeMiS sources in these diagrams with modelled evolutionary tracks of both core-fed and clump-fed accretion scenarios. We argue that the latter provide a better agreement with the observed distribution of high-mass star-forming cores. However, a robust and definitive conclusion on the question of the accretion history of high-mass stars requires larger number statistics.
423. Accretion in disks in Cep OB2
ID:
ivo://CDS.VizieR/J/ApJ/710/597
Title:
Accretion in disks in Cep OB2
Short Name:
J/ApJ/710/597
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members of the ~4Myr old cluster Tr 37 (including 20 "transition" objects (TOs)), as well as the only classical T Tauri star (CTTS) in the ~12Myr old cluster NGC 7160. The stars show different disk morphologies, with the majority of them having evolved and flattened disks. The typical accretion rates are about 1 order of magnitude lower than in regions aged 1-2Myr, and we find no strong correlation between disk morphology and accretion rates. Although half of the TOs are not accreting, the median accretion rates of normal CTTS and accreting "transition" disks are similar (~3x10^-9^ and 2x10^-9^M_{sun}_/yr, respectively). Comparison with other regions suggests that the TOs observed at different ages do not necessarily represent the same type of objects, which is consistent with the fact that the different processes that can lead to reduced IR excess/inner disk clearing (e.g., binarity, dust coagulation/settling, photoevaporation, giant planet formation) do not operate on the same timescales.
424. Accretion in {rho}-Ophiucus
ID:
ivo://CDS.VizieR/J/A+A/579/A66
Title:
Accretion in {rho}-Ophiucus
Short Name:
J/A+A/579/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new VLT/X-Shooter optical and near-infrared spectra of a sample of 17 candidate young low-mass stars and brown dwarfs located in the {rho}-Ophiucus cluster. We derived the spectral type and extinction for all the targets, and then we determined their physical parameters. All the objects but one have M_*_<~0.6M_{sun}_, and eight have mass below or close to the hydrogen-burning limit. Using the intensity of various permitted emission lines present in their spectra, we determined the accretion luminosity and mass accretion rates ({dot}(M)_acc_) for all the objects. When compared with previous works targeting the same sample, we find that, in general, these objects are not as strongly accreting as previously reported, and we suggest that the reason is our more accurate estimate of the photospheric parameters. We also compare our findings with recent works in other slightly older star-forming regions, such as Lupus, to investigate possible differences in the accretion properties, but we find that the accretion properties for our targets have the same dependence on the stellar and substellar parameters as in the other regions. This leads us to conclude that we do not find evidence for a different dependence of {dot}(M)_acc_ with M_*_ when comparing low-mass stars and brown dwarfs. Moreover, we find a similar small (<~1dex) scatter in the {dot}(M)_acc_-M_*_ relation as in some of our recent works in other star-forming regions, and no significant differences in {dot}(M)_acc_ due to different ages or properties of the regions. The latter result suffers, however, from low statistics and sample selection biases in the current studies. The small scatter in the {dot}(M)_acc_-M_*_ correlation confirms that mass accretion rate measurements in the literature based on uncertain photospheric parameters and single accretion indicators, such as the H{alpha} width, can lead to a scatter that is unphysically large. Our studies show that only broadband spectroscopic surveys coupled with a detailed analysis of the photospheric and accretion properties allows us to properly study the evolution of disk accretion rates in star-forming regions.
425. Accretion luminosities of young stars from Pf{beta}
ID:
ivo://CDS.VizieR/J/ApJ/769/21
Title:
Accretion luminosities of young stars from Pf{beta}
Short Name:
J/ApJ/769/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we introduce the use of HI Pfund {beta} (Pf{beta}; 4.6538{mu}m) as a tracer of mass accretion from protoplanetary disks onto young stars. Pf{beta} was serendipitously observed in NIRSPEC and CRIRES surveys of CO fundamental emission, amounting to a sample size of 120 young stars with detected Pf{beta} emission. Using a subsample of disks with previously measured accretion luminosities, we show that Pf{beta} line luminosity is well correlated with accretion luminosity over a range of at least three orders of magnitude. We use this correlation to derive accretion luminosities for all 120 targets, 65 of which are previously unreported in the literature. The conversion from accretion luminosity to accretion rate is limited by the availability of stellar mass and radius measurements; nevertheless, we also report accretion rates for 67 targets, 16 previously unmeasured. Our large sample size and our ability to probe high extinction values allow for relatively unbiased comparisons between different types of disks.
426. Accretion process in NGC 2264
ID:
ivo://CDS.VizieR/J/A+A/586/A47
Title:
Accretion process in NGC 2264
Short Name:
J/A+A/586/A47
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 2264 is a young stellar cluster (~3Myr) with hundreds of low-mass accreting stars that allow a detailed analysis of the accretion process taking place in the pre-main sequence. Our goal is to relate the photometric and spectroscopic variability of classical T Tauri stars to the physical processes acting in the stellar and circumstellar environment, within a few stellar radii from the star. NGC 2264 was the target of a multiwavelength observational campaign with CoRoT, MOST, Spitzer, and Chandra satellites and photometric and spectroscopic observations from the ground. We classified the CoRoT light curves of accreting systems according to their morphology and compared our classification to several accretion diagnostics and disk parameters.
427. Accretion rate distributions of AGNs
ID:
ivo://CDS.VizieR/J/other/ChA+A/32.351
Title:
Accretion rate distributions of AGNs
Short Name:
J/other/ChA+A/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
The redshift, central black hole mass and accretion rate are important parameters when studying the AGN evolution. The central black hole masses for 172 quasars and Seyfert galaxies are calculated in this paper using the reverberation mapping method. The distributions of central black hole masses, redshifts and the Eddington accretion rates are analyzed, to verify the transition from the quasar to the Seyfert galaxy in the course of evolution.
428. Accretion rate of AGNs from COSMOS surveys
ID:
ivo://CDS.VizieR/J/ApJ/733/60
Title:
Accretion rate of AGNs from COSMOS surveys
Short Name:
J/ApJ/733/60
Date:
21 Oct 2021
Publisher:
CDS
Description:
We show how accretion rate governs the physical properties of a sample of unobscured broad-line, narrow-line, and lineless active galactic nuclei (AGNs). We avoid the systematic errors plaguing previous studies of AGN accretion rates by using accurate intrinsic accretion luminosities (Lint) from well-sampled multiwavelength spectral energy distributions from the Cosmic Evolution Survey, and accurate black hole masses derived from virial scaling relations (for broad-line AGNs) or host-AGN relations (for narrow-line and lineless AGNs).
429. Accretion-rotation connection in NGC 2264
ID:
ivo://CDS.VizieR/J/A+A/599/A23
Title:
Accretion-rotation connection in NGC 2264
Short Name:
J/A+A/599/A23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The low spin rates measured for solar-type stars at an age of a few Myr (~10% of the break-up velocity) indicate that some mechanism of angular momentum regulation must be at play in the early pre-main sequence. This may be associated with magnetospheric accretion and star-disk interaction, as suggested by observations that disk-bearing objects (CTTS) are slower rotators than diskless sources (WTTS) in young star clusters. We characterize the rotation properties for members of the star-forming region NGC 2264 (~3Myr) as a function of mass, and investigate the accretion-rotation connection at an age where about 50% of the stars have already lost their disks. We examined a sample of 500 cluster members (40% with disks, 60% without disks), distributed in mass between ~0.15 and 2M_{sun}_, whose photometric variations were monitored in the optical for 38 consecutive days with the CoRoT space observatory. Light curves were analyzed for periodicity using three different techniques: the Lomb-Scargle periodogram, the autocorrelation function and the string-length method. Periods were searched in the range between 0.17-days (i.e., 4h, twice the data sampling adopted) and 19-days (half the total time span). Period detections were confirmed using a variety of statistical tools (false alarm probability, Q-statistics), as well as visual inspection of the direct and phase-folded light curves.
430. Accurate astrometry & RVs of 4 multiple systems
ID:
ivo://CDS.VizieR/J/ApJ/838/54
Title:
Accurate astrometry & RVs of 4 multiple systems
Short Name:
J/ApJ/838/54
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work extends the still modest number of multiple stars with known relative orbit orientation. Accurate astrometry and radial velocities are used jointly to compute or update outer and inner orbits in three nearby triple systems, HIP 101955 (orbital periods 38.68 and 2.51yr), HIP 103987 (19.20 and 1.035yr), HIP 111805 (30.13 and 1.50yr), and in one quadruple system, HIP 2643 (periods 70.3, 4.85, and 0.276yr), all composed of solar-type stars. The masses are estimated from the absolute magnitudes and checked using the orbits. The ratios of outer to inner periods (from 14 to 20) and the eccentricities of the outer orbits are moderate. These systems are dynamically stable, but not very far from the stability limit. In three systems, all orbits are approximately coplanar and have small eccentricity, while in HIP101955 the inner orbit with e=0.6 is highly inclined.

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