- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3039
- Title:
- Eruptive variable protostars from VVV EW
- Short Name:
- J/MNRAS/465/3039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a companion work (Contreras Pena et al., 2017MNRAS.465.3011C, Paper I), we detected a large population of highly variable Young Stellar Objects (YSOs) in the Vista Variables in the Via Lactea (VVV) survey, typically with class I or flat spectrum spectral energy distributions and diverse light-curve types. Here we present infrared spectra (0.9-2.5 {mu}m) of 37 of these variables, many of them observed in a bright state. The spectra confirm that 15/18 sources with eruptive light curves have signatures of a high accretion rate, either showing EXor-like emission features ({Delta}v=2 CO, Br{gamma}) and/or FUor-like features ({Delta}v=2 CO and H_2_O strongly in absorption). Similar features were seen in some long-term periodic YSOs and faders but not in dippers or short-term variables. The sample includes some dusty Mira variables (typically distinguished by smooth Mira-like light curves), two cataclysmic variables and a carbon star. In total, we have added 19 new objects to the broad class of eruptive variable YSOs with episodic accretion. Eruptive variable YSOs in our sample that were observed at bright states show higher accretion luminosities than the rest of the sample. Most of the eruptive variables differ from the established FUor and EXor subclasses, showing intermediate outburst durations and a mixture of their spectroscopic characteristics. This is in line with a small number of other recent discoveries. Since these previously atypical objects are now the majority amongst embedded members of the class, we propose a new classification for them as MNors. This term (pronounced emnor) follows V1647 Ori, the illuminating star of McNeil's Nebula.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/4364
- Title:
- Extended H2 emission from massive YSOs survey
- Short Name:
- J/MNRAS/450/4364
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from a survey, designed to investigate the accretion process of massive young stellar objects (MYSOs) through near infrared narrow band imaging using the H_2_ {nu}=1-0 S(1) transition filter. A sample of 353 Massive Young Stellar Object (MYSO) candidates was selected from the Red MSX Source survey using photometric criteria at longer wavelengths (infrared and submillimeter) and chosen with positions throughout the Galactic Plane. Our survey was carried out at the SOAR Telescope in Chile and CFHT in Hawaii covering both hemispheres.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A101
- Title:
- Extremely high-velocity jets in Serpens
- Short Name:
- J/A+A/632/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ALMA observations of four molecular transitions, CO 2-1, SiO 5-4, H_2_CO 3_03_-2_02_ in Band 6 (ALMA project 2013.1.00726.S; PI: C. Hull) and HCN 1-0 observed in Band 3 (ALMA project 2016.1.00710.S; PI: C. Hull) are presented. The synthesized beam of the observations is between 0.3 and 0.6 arcsec, corresponding to 130-260au at the distance to Serpens Main. The largest recoverable scale in the data is 5 arcsec and 12 arcsec (2150 and 4960au) for Band 3 and Band 6, respectively. The spectral resolution of the observations differs between the spectral windows, ranging from 0.04 to 0.3km/s. For both bands, only 12-m array data were used. The Band 6 data were obtained in two configurations (C43-1 and C43-4 with resolutions of 1.1 and 0.3 arcsec, respectively, and the final images are produced from the combined datasets.
- ID:
- ivo://CDS.VizieR/J/PASJ/60/209
- Title:
- Faint companions around YSOs in TMC
- Short Name:
- J/PASJ/60/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted near-infrared spectroscopy of 26 faint objects around young stellar objects in the Taurus molecular cloud. These objects were detected during a course of near-infrared coronagraphic searches for companions around 72 young stellar objects with the Subaru Telescope and the near-infrared coronagraph CIAO (coronagraphic imager with adaptive optics). A comparison of the Subaru and HST archive images revealed that three central stars and faint companions share common proper motions, suggesting that they are physically associated with each other. None of the 26 sources show deep water absorption bands at near-infrared, except for DH Tau B. This result indicates that all of them, but DH Tau B, have a high photospheric temperature or a large amount of excess from circumstellar materials.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A59
- Title:
- Far-IR lines in YSOs Herschel-PACS
- Short Name:
- J/A+A/594/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas plays a major role in the dynamical evolution of young stellar objects (YSOs). Its interaction with the dust is the key to our understanding planet formation later on in the protoplanetary disc stage. Studying the gas content is therefore a crucial step towards understanding YSO and planet formation. Such a study can be made through spectroscopic observations of emission lines in the far-infrared, where some of the most important gas coolants emit, such as the [OI] ^3^P_1_-^3^P_2_ transition at 63.18 microns. We provide a compilation of observations of far-IR lines in 362 young stellar objects covering all evolutionary stages, from Class 0 to Class III with debris discs. In the present paper we focus on [OI] and o-H_2_O emission at 63 microns. We have retrieved all the available Herschel-PACS spectroscopic observations at 63 microns that used the dominant observing mode, the chop-nod technique. We provide measurements of line fluxes for the [OI] ^3^P_1_-^3^P_2_ and o-H_2_O 8_08_-7_17_ transitions at 63 microns computed using different methods. Taking advantage of the PACS IFU, we check for spatially extended emission and further study the presence of multiple dynamical components in line emission. The final compilation consists of line and continuum fluxes at 63 microns for a total of 362 young stellar objects (YSOs). We detected [OI] line emission at 63 microns in 194 sources out of 362, and line absorption in another five sources. o-H_2_O was detected in 42 sources. We find evidence of extended [OI] emission in 77 sources, and detect 3sigma residual emission in 71 of them. The number of sources showing extended emission decays from Class 0 to Class II. We also looked for different components contributing to the line emission, and found evidence for multiple components in 30 sources. We explored correlations between line emission and continuum emission and find a clear correlation between WISE fluxes from 4.6 to 22 microns and [OI] line emission. We conclude that the observed emission is typically a combination of disc/envelope and jet emission.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A72
- Title:
- Fermi sources with massive YSO associations
- Short Name:
- J/A+A/530/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive protostars have associated bipolar outflows that can produce strong shocks when they interact with the surrounding medium. At these shocks, particles can be accelerated up to relativistic energies. Relativistic electrons and protons can then produce gamma-ray emission, as some theoretical models predict. To identify young galactic objects that may emit gamma rays, we crossed the Fermi First Year Catalog with some catalogs of known massive young stellar objects (MYSOs), early type stars, and OB associations, and we implemented Monte Carlo simulations to find the probability of chance coincidences. We obtained a list of massive MYSOs that are spatially coincident with Fermi sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/63
- Title:
- FIR-mm data of YSOs in star-forming regions
- Short Name:
- J/ApJ/849/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the Herschel Space Observatory with ancillary data of 284 protoplanetary disks in the Taurus, Chamaeleon I, and Ophiuchus star-forming regions, covering from the optical to mm/cm wavelengths. We analyze their spectral indices as a function of wavelength and determine their (sub)millimeter slopes when possible. Most disks display observational evidence of grain growth, in agreement with previous studies. No correlation is found between other tracers of disk evolution and the millimeter spectral indices. A simple disk model is used to fit these sources, and we derive posterior distributions for the optical depth at 1.3mm and 10au, the disk temperature at this same radius, and the dust opacity spectral index {beta}. We find the fluxes at 70{mu}m to correlate strongly with disk temperatures at 10au, as derived from these simple models. We find tentative evidence for spectral indices in Chamaeleon I being steeper than those of disks in Taurus/Ophiuchus, although more millimeter observations are needed to confirm this trend and identify its possible origin. Additionally, we determine the median spectral energy distribution of each region and find them to be similar across the entire wavelength range studied, possibly due to the large scatter in disk properties and morphologies.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/L2
- Title:
- First detection of HCOOH in TW Hya disk with ALMA
- Short Name:
- J/ApJ/862/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of asteroids, comets, and planets occurs in the interior of protoplanetary disks during the early phase of star formation. Consequently, the chemical composition of the disk might shape the properties of the emerging planetary system. In this context, it is crucial to understand whether and what organic molecules are synthesized in the disk. In this Letter, we report the first detection of formic acid (HCOOH) toward the TW Hydrae protoplanetary disk. The observations of the trans-HCOOH 6_(1,6)-5(1,5)_ transition were carried out at 129GHz with Atacama Large Millimeter/Submillimeter Array (ALMA). We measured a disk-averaged gas-phase t-HCOOH column density of ~(2-4)x10^12^cm^-2^, namely as large as that of methanol. HCOOH is the first organic molecule containing two oxygen atoms detected in a protoplanetary disk, a proof that organic chemistry is very active, albeit difficult to observe, in these objects. Specifically, this simplest acid stands as the basis for synthesis of more complex carboxylic acids used by life on Earth.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/71
- Title:
- Fluxes & physical param. of blended YSOs
- Short Name:
- J/ApJ/864/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite significant evidence suggesting that intermediate- and high-mass stars form in clustered environments, how stars form when the available resources are shared is still not well understood. A related question is whether the initial mass function (IMF) is in fact universal across galactic environments, or whether it is an average of IMFs that differ, for example, in massive versus low-mass molecular clouds. One of the long-standing problems in resolving these questions and in the study of young clusters is observational: how to accurately combine multiwavelength data sets obtained using telescopes with different spatial resolutions. The resulting confusion hinders our ability to fully characterize clustered star formation. Here we present a new method that uses Bayesian inference to fit the blended spectral energy distributions and images of individual young stellar objects (YSOs) in confused clusters. We apply this method to the infrared photometry of a sample comprising 70 Spitzer-selected, low-mass (M_cl_<100M_{sun}_) young clusters in the galactic plane, and we use the derived physical parameters to investigate how the distribution of YSO masses within each cluster relates to the total mass of the cluster. We find that for low-mass clusters this distribution is indistinguishable from a randomly sampled Kroupa IMF for this range of cluster masses. Therefore, any effects of self-regulated star formation that affect the IMF sampling are likely to play a role only at larger cluster masses. Our results are also compatible with smoothed particle hydrodynamics models that predict a dynamical termination of the accretion in protostars, with massive stars undergoing this stopping at later times in their evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/133
- Title:
- Follow-up of probable young star ASASSN-15qi
- Short Name:
- J/ApJ/831/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The ~3.5mag brightening in the V band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from ~10000K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000km/s. The wind and hot gas both disappeared as the outburst faded and the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H_2_ is detected in emission from vibrational levels as high as v=11, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, though the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling.
