Search

Start Over Content Level Research
24701. Young stellar objects in W49A and W51
ID:
ivo://CDS.VizieR/J/MNRAS/477/3369
Title:
Young stellar objects in W49A and W51
Short Name:
J/MNRAS/477/3369
Date:
17 Jan 2022 00:25:04
Publisher:
CDS
Description:
We have compared the star-formation properties of the W49A and W51 regions by using far-infrared data from the Herschel infrared Galactic Plane Survey (Hi-GAL) and 850-um observations from the James Clerk Maxwell Telescope (JCMT) to obtain luminosities and masses, respectively, of associated compact sources. The former are infrared luminosities from the catalogue of Elia et al., while the latter are from the JCMT Plane survey source catalogue as well as measurements from new data. The clump-mass distributions of the two regions are found to be consistent with each other, as are the clump-formation efficiency and star-formation efficiency analogues. However, the frequency distributions of the luminosities of the young stellar objects are significantly different. While the luminosity distribution in W51 is consistent with Galaxy-wide samples, that of W49A is top heavy. The differences are not dramatic and are concentrated in the central regions of W49A. However, they suggest that physical conditions there, which are comparable in part to those in extragalactic starbursts, are significantly affecting the star-formation properties or evolution of the dense clumps in the region.
24702. Young stellar outflows near-IR imaging
ID:
ivo://CDS.VizieR/J/MNRAS/404/661
Title:
Young stellar outflows near-IR imaging
Short Name:
J/MNRAS/404/661
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out a near-infrared imaging survey of luminous young stellar outflow candidates using the United Kingdom Infrared Telescope. Observations were obtained in the broad band K (2.2um) and through narrow band filters at the wavelengths of H_2_ v=1-0 S(1) (2.1218um) and Br gamma (2.166um) lines. Fifty regions were imaged with a field of view of 2.2x2.2arcmin^2^. Several young embedded clusters are unveiled in our near-infrared images. 76% of the objects exhibit H_2_ emission and 50% or more of the objects exhibit aligned H_2_ emission features suggesting collimated outflows, many of which are new detections. These observations suggest that disk accretion is probably the leading mechanism in the formation of stars, at least up to late O spectral types. The young stellar objects responsible for many of these outflows are positively identified in our images based on their locations with respect to the outflow lobes, 2MASS colours and association with MSX, IRAS, millimetre and radio sources. The close association of molecular outflows detected in CO with the H_2_ emission features produced by shock excitation by jets from the young stellar objects suggests that the outflows from these objects are jet-driven. Towards strong radio emitting sources, H_2_ jets were either not detected or were weak when detected, implying that most of the accretion happens in the pre-UCHII phase; accretion and outflows are probably weak when the YSO has advanced to its UCHII stage.
24703. Young stellar structures in NGC 6503
ID:
ivo://CDS.VizieR/J/MNRAS/452/3508
Title:
Young stellar structures in NGC 6503
Short Name:
J/MNRAS/452/3508
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a detailed clustering analysis of the young stellar population across the star-forming ring galaxy NGC 6503, based on the deep Hubble Space Telescope photometry obtained with the Legacy ExtraGalactic UV Survey. We apply a contour-based map analysis technique and identify in the stellar surface density map 244 distinct star-forming structures at various levels of significance. These stellar complexes are found to be organized in a hierarchical fashion with 95 percent being members of three dominant super-structures located along the star-forming ring. The size distribution of the identified structures and the correlation between their radii and numbers of stellar members show power-law behaviours, as expected from scale-free processes. The self-similar distribution of young stars is further quantified from their autocorrelation function, with a fractal dimension of ~1.7 for length-scales between ~20pc and 2.5kpc. The young stellar radial distribution sets the extent of the star-forming ring at radial distances between 1 and 2.5kpc. About 60 percent of the young stars belong to the detected stellar structures, while the remaining stars are distributed among the complexes, still inside the ring of the galaxy. The analysis of the time-dependent clustering of young populations shows a significant change from a more clustered to a more distributed behaviour in a time-scale of ~60Myr. The observed hierarchy in stellar clustering is consistent with star formation being regulated by turbulence across the ring. The rotational velocity difference between the edges of the ring suggests shear as the driving mechanism for this process. Our findings reveal the interesting case of an inner ring forming stars in a hierarchical fashion.
24704. Young stellar variables with KELT for K2. I.
ID:
ivo://CDS.VizieR/J/ApJ/848/97
Title:
Young stellar variables with KELT for K2. I.
Short Name:
J/ApJ/848/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
One of the most well-studied young stellar associations, Taurus-Auriga, was observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) is a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers," aperiodic and periodic variables among K2 C13 target stars. This release of the KELT data provides the community with long-time baseline observations to assist in the understanding of the more exotic variables in the association. Transient-like phenomena on timescales of months to years are known characteristics in the light curves of young stellar objects, making contextual pre- and post-K2 observations critical to understanding their underlying processes. We are providing a comprehensive set of the KELT light curves for known Taurus-Auriga stars in K2 C13. The combined data sets from K2 and KELT should permit a broad array of investigations related to star formation, stellar variability, and protoplanetary environments.
24705. Young super star clusters in the starburst of M82
ID:
ivo://CDS.VizieR/J/ApJ/619/270
Title:
Young super star clusters in the starburst of M82
Short Name:
J/ApJ/619/270
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent results from the Hubble Space Telescope (HST) have resolved starbursts as collections of compact young stellar clusters. Here we present a photometric catalog of the young stellar clusters in the nuclear starburst of M82, observed with the HST WFPC2 in H{alpha} (F656N) and in four optical broadband filters. We identify 197 young super stellar clusters (SSCs). The compactness and high density of the sources led us to develop specific techniques to measure their sizes. Strong extinction lanes divide the starburst into five different zones. In the catalog we include relative coordinates, radii, fluxes, luminosities, masses, equivalent widths, extinctions, and other parameters. Extinction values have been derived from the broadband images.
24706. Young T Tauri star in CB 26 molecular outflows
ID:
ivo://CDS.VizieR/J/A+A/494/147
Title:
Young T Tauri star in CB 26 molecular outflows
Short Name:
J/A+A/494/147
Date:
21 Oct 2021
Publisher:
CDS
Description:
The disk-outflow connection is thought to play a key role in extracting excess angular momentum from a forming proto-star. Although jet rotation has been observed in a few objects, no rotation of molecular outflows has been unambiguously reported so far. We report new millimeter-interferometric observations of the edge-on T-Tauri-star - disk system in the isolated Bok globule CB-26. The aim of these observations was to study the disk-outflow relation in this 1Myr old low-mass young stellar object.
24707. Young visual M-dwarf binaries spectra
ID:
ivo://CDS.VizieR/J/A+A/642/A57
Title:
Young visual M-dwarf binaries spectra
Short Name:
J/A+A/642/A57
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from an integral field spectroscopy study of seven close visual binary pairs of young M-dwarf multiple systems. The target systems are part of the astrometric monitoring AstraLux program, surveying hundreds of M-dwarf systems for multiplicity and obtaining astrometric epochs for orbital constraints. Our new VLT/SINFONI data provides resolved spectral type classification in the J, H and K bands for seven of these low-mass M-dwarf binaries, which we determine by comparing them to empirical templates and examining the strength of water absorption in the K-band. The medium resolution K-band spectra also allows us to derive effective temperatures for the individual components. All targets in the survey display several signs of youth, and some have kinematics similar to young moving groups, or low surface gravities which we determine from measuring equivalent widths of gravity sensitive alkali lines in the J-band. Resolved photometry from our targets is also compared with isochrones from theoretical evolutionary models, further implying young ages. Dynamical masses will be provided from ongoing monitoring of these systems, which can be seen as emblematic binary benchmarks that may be used to calibrate evolutionary models for low-mass stars in the future.
24708. 25yr CaII-HK observations of F-K nearby stars
ID:
ivo://CDS.VizieR/J/ApJ/457/L99
Title:
25yr CaII-HK observations of F-K nearby stars
Short Name:
J/ApJ/457/L99
Date:
21 Oct 2021
Publisher:
CDS
Description:
We find a significant correlation between the magnetic and rotational moments for a sample of 112 lower main-sequence stars. The rotational moment is calculated from measurements of the rotation period in most of the stars (not from the projected rotational velocity inferred from Doppler broadening). The magnetic moment is computed from a database of homogeneous measurements of the mean level of Ca II H and K emission fluxes sampled for most of the stars over an interval of 25yr. The slope connecting the logarithm of the magnetic moment and the logarithm of the rotational moment is about +0.5-0.6, with a Pearson correlation coefficient of about +0.9. The scatter of points from the mean relation has a component that is natural and caused by decade-long surface variability.
24709. 8yr INTEGRAL/IBIS soft gamma-ray source obs.
ID:
ivo://CDS.VizieR/J/ApJS/223/15
Title:
8yr INTEGRAL/IBIS soft gamma-ray source obs.
Short Name:
J/ApJS/223/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
Here we report an all-sky soft gamma-ray source catalog based on IBIS observations performed during the first 1000 orbits of INTEGRAL. The database for the construction of the source list consists of all good-quality data available, from the launch in 2002, up to the end of 2010. This corresponds to ~110Ms of scientific public observations, with a concentrated coverage on the Galactic Plane and extragalactic deep exposures. This new catalog includes 939 sources above a 4.5{sigma} significance threshold detected in the 17-100keV energy band, of which 120 sources represent previously undiscovered soft gamma-ray emitters. The source positions are determined, mean fluxes are provided in two main energy bands, and these are both reported together with the overall source exposure. Indicative levels of variability are provided, and outburst times and durations are given for transient sources. A comparison is made with previous IBIS catalogs and catalogs from other similar missions.
24710. 16yr LC of TXS 0506+056 from MASTER networks
ID:
ivo://CDS.VizieR/J/ApJ/896/L19
Title:
16yr LC of TXS 0506+056 from MASTER networks
Short Name:
J/ApJ/896/L19
Date:
07 Dec 2021
Publisher:
CDS
Description:
We present the earliest astronomical observation of a high-energy neutrino error box of which the variability was discovered after high-energy-neutrino detection. The one robotic telescope of the MASTER global international networks automatically imaged the error box of the very high-energy-neutrino event IceCube-170922A. Observations were carried out in minutes after the IceCube-170922A neutrino event was detected by the IceCube observatory at the South Pole. MASTER found the blazar TXS 0506+056 to be in the off-state after one minute and then switched to the on-state no later than two hours after the event. The effect is observed at a 50{sigma} significance level. We also present own a unique 16yr light curve of blazar TXS 0506+056 (518 data set).

Limit your search

more »

more »

more »

more »

more »

more »

more »

more »