- ID:
- ivo://CDS.VizieR/J/AJ/162/183
- Title:
- Infrared spectra of V838 Monocerotis with SOFIA
- Short Name:
- J/AJ/162/183
- Date:
- 14 Mar 2022 06:37:38
- Publisher:
- CDS
- Description:
- Luminous Red Variables are most likely eruptions that are the outcome of stellar mergers. V838Mon is one of the best-studied members of this class, representing an archetype for stellar mergers resulting from B-type stars. As result of the merger event, "nova-like" eruptions occur driving mass loss from the system. As the gas cools considerable circumstellar dust is formed. V838Mon erupted in 2002 and is undergoing very dynamic changes in its dust composition, geometry, and infrared luminosity providing a real-time laboratory to validate mineralogical condensation sequences in stellar mergers and evolutionary scenarios. We discuss recent NASA Stratospheric Observatory for Infrared Astronomy 5-38{mu}m observations combined with archival NASA Spitzer spectra that document the temporal evolution of the freshly formed (within the last <~20yr) circumstellar material in the environs of V838Mon. Changes in the 10{mu}m spectral region are strong evidence that we are witnessing a classical dust condensation sequence expected to occur in oxygen-rich environments where alumina formation is followed by that of silicates at the temperature cools.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/374/399
- Title:
- Infrared star clusters with |b|<20{deg}
- Short Name:
- J/MNRAS/374/399
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used star density maps obtained from the Two-Micron All-Sky Survey (2MASS) to obtain a sample of star clusters in the entire Galactic Plane with |b|<20{deg}. A total of 1788 star cluster candidates are identified in this survey. Among those are 681 previously known open clusters and 86 globular clusters. A statistical analysis indicates that our sample of 1021 new cluster candidates has a contamination of about 50 per cent. Star cluster parameters are obtained by fitting a King profile to the star density. These parameters are used to statistically identify probable new globular cluster candidates in our sample. A detailed investigation of the projected distribution of star clusters in the Galaxy demonstrates that they show a clear tendency to cluster on spatial scales in the order of 12-25pc, a typical size for molecular clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/463/175
- Title:
- Infrared study of IRAS 14416-5937 region
- Short Name:
- J/A+A/463/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out an infrared study of the southern Galactic massive star-forming region associated with IRAS 14416-5937. This star-forming region has been mapped simultaneously in two far infrared bands at ~150 & 210 micron using the TIFR 1-m balloon borne telescope with ~1' angular resolution. We have used the 2MASS JHKs data as well as the GLIMPSE-Spitzer data of this region to study the stellar populations of the embedded young cluster. This region comprises of two sources designated as A and B, separated by ~2pc. The spectrum of a region located close to the source A obtained using the Long Wavelength Spectrometer (LWS) on-board the Infrared Space Observatory (ISO) is presented. Emission from warm dust and the unidentified infrared bands (UIBs) is estimated using the mid-infrared data from the MSX survey. The spatial distribution of the temperature of cool dust and optical depth at 200 micron have been obtained taking advantage of the similar beams in the two TIFR bands. A number of atomic fine structure lines have been detected in the ISO-LWS spectrum, which have been used to estimate the electron density and the effective temperature of the ionising radiation in this region. From the near and mid infrared images, we identify a dust lane due north-west direction of the source A. The dust lane is populated by Class I type sources. Class II type sources are found further along the dust lane as well as below it. Self consistent radiative transfer models of the two sources (A and B) are in good agreement with the observed spectral energy distributions. The spatial distribution of young stellar objects in and around the dust lane suggests that active star formation is taking place along the dust lane and is possibly triggered by the expanding HII regions of A and B.
- ID:
- ivo://CDS.VizieR/J/AJ/134/214
- Title:
- Infrared study of J-type carbon stars
- Short Name:
- J/AJ/134/214
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We collected 113 J-type carbon stars from the published literature. Observations from 2MASS, IRAS, and ISO show that, except for silicate carbon stars in the J-type carbon star domain, the infrared properties of the other J-type carbon stars are quite similar to those of ordinary carbon stars. The above results imply that the chemical peculiarity of enhanced ^13^C for J-type carbon stars is not reflected in the infrared region. In addition, the possible evolutionary scenario and binarity for J-type carbon stars are also discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A24
- Title:
- Infra-red transitions of Ca and Mg
- Short Name:
- J/A+A/554/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While solar spectra contain a lot of CaI and MgI infrared lines, no laboratory-measured spectra of these atoms have been reported for wavenumbers below 2000cm^-1^. This study reports CaI spectra in 1300-4500cm^-1^ range and MgI spectra in 1300-4500cm^-1^ range. We perform the time-resolved Fourier transform infrared spectroscopy study of a plasma created by the laser ablation of MgF_2_ and CaF_2_ targets in a vacuum. The oscillator strengths(f-values) are calculated using quantum defect theory (QDT) which shows good agreement with the available experimental and theoretical results. We report several CaI and MgI IR lines which have not been measured previously in laboratory. The recorded spectra allow to determine the excitation energies of some Ca I and Mg I states with high orbital momentum (l=4,5). We also provide a large list of QDT-calculated f-values for CaI and MgI in the range of 800-9000cm^-1^.
- ID:
- ivo://CDS.VizieR/J/AJ/160/201
- Title:
- Infrared transmission spectrum for Kepler-79d
- Short Name:
- J/AJ/160/201
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extremely low-density planets ("super-puffs") are a small but intriguing subset of the transiting planet population. With masses in the super-Earth range (1-10M{Earth}) and radii akin to those of giant planets (>4R{Earth}), their large envelopes may have been accreted beyond the water snow line and many appear to be susceptible to catastrophic mass loss. Both the presence of water and the importance of mass loss can be explored using transmission spectroscopy. Here, we present new Hubble space telescope WFC3 spectroscopy and updated Kepler transit depth measurements for the super-puff Kepler-79d. We do not detect any molecular absorption features in the 1.1-1.7{mu}m WFC3 bandpass, and the combined Kepler and WFC3 data are consistent with a flat-line model, indicating the presence of aerosols in the atmosphere. We compare the shape of Kepler-79d transmission spectrum to predictions from a microphysical haze model that incorporates an outward particle flux due to ongoing mass loss. We find that photochemical hazes offer an attractive explanation for the observed properties of super-puffs like Kepler-79d, as they simultaneously render the near-infrared spectrum featureless and reduce the inferred envelope mass-loss rate by moving the measured radius (optical depth unity surface during transit) to lower pressures. We revisit the broader question of mass-loss rates for super-puffs and find that the age estimates and mass-loss rates for the majority of super-puffs can be reconciled if hazes move the photosphere from the typically assumed pressure of ~10mbar to ~10{mu}bar.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/125
- Title:
- IN-SYNC. I. APOGEE stellar parameters
- Short Name:
- J/ApJ/794/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Over two years, 8859 high-resolution H-band spectra of 3493 young (1-10Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of the SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. In addition, we present accurate extinctions by measuring the E(J-H) of these young stars with respect to the single-star photometric locus in the Pleiades. Finally, we identify an intrinsic stellar radius spread of about 25% for late-type stars in IC 348 using three (nearly) independent measures of stellar radius, namely, the extinction-corrected J-band magnitude, the surface gravity, and the Rsini from the rotational velocities and literature rotation periods. We exclude that this spread is caused by uncertainties in the stellar parameters by showing that the three estimators of stellar radius are correlated, so that brighter stars tend to have lower surface gravities and larger Rsini than fainter stars at the same effective temperature.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/136
- Title:
- IN-SYNC. II. Candidate young stars in NGC 1333
- Short Name:
- J/ApJ/799/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2Myr) stars in NGC 1333 is 0.92+/-0.12km/s after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a subvirial velocity dispersion of 0.5km/s. Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70{mu}G magnetic field acting on the dense cores or be the signature of a cluster with initial substructure undergoing global collapse.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/59
- Title:
- IN-SYNC. IV. YSOs in Orion A
- Short Name:
- J/ApJ/818/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the Sloan Digital Sky Survey APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high-resolution near-infrared spectroscopy of about 2700 young pre-main-sequence stars on a ~6{deg} field of view. We have measured accurate stellar parameters (T_eff_, logg, vsini) and extinctions and placed the sources in the Hertzsprung-Russel diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results to assess the performance and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium: we estimate an average R_V_=5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity-inferred ages and between extinction and disk presence; this strongly suggests a real spread of ages larger than a few Myr. Focusing on the young population around NGC 1980/{iota} Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (~5Myr) age and low A_V_, but considering that its radial velocity distribution is indistinguishable from Orion A's population, we suggest that NGC 1980 is part of Orion A's star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/72
- Title:
- IN-SYNC. VIII. YSOs in NGC 1333, IC 348 and Orion A
- Short Name:
- J/ApJ/869/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we address two issues related to primordial disk evolution in three clusters (NGC1333, IC348, and OrionA) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC348 and OrionA is that primordial disks around intermediate-mass stars (2-5M_{sun}_) evolve faster than those around loss-mass stars (0.1-1M_{sun}_), which is consistent with previous results. However, considering only low-mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Second, in the OrionA molecular cloud, in the mass range of 0.35-0.7M_{sun}_, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5{mu}m excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC1333 and IC348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1{sigma} effect.
