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Start Over Subject infrared astronomy
621. Library of Spectra (0.5 to 2.5um) of Cool Stars
ID:
ivo://CDS.VizieR/J/A+AS/146/217
Title:
Library of Spectra (0.5 to 2.5um) of Cool Stars
Short Name:
J/A+AS/146/217
Date:
21 Oct 2021
Publisher:
CDS
Description:
The present catalogue contains 182 low resolution optical spectra, 145 medium resolution (R~1100) near-IR spectra, and 112 merged optical+near-IR spectra that range from about 510 to 2450 nm. The observed stars are luminous cool objects: the sample includes red giants, red supergiants, oxygen rich and carbon rich long period variables (asymptotic giant branch stars), as well as a few Galactic Bulge and LMC/SMC stars. The optical data were acquired on the so-called 74 inch Telescope at Mount Stromlo Observatory. The near-IR data were acquired with the Cryogenic Array Spectrometer and Imager CASPIR on the 2.3 meter Australian National University Telescope at Siding Spring Observatory. Optical and near-IR data for variable objects have been merged only when both were taken less than 15 days apart; but both spectral ranges are also provided separately. The spectra are corrected for telluric absorption. However, in regions where the transmission of the Earth atmosphere is close to zero the fluxes recovered remain highly uncertain. The flux calibration is based on a series of reference stars, for which a theoretical intrinsic energy distribution was assumed. An absolute flux calibration (to about 10% accuracy) was only achieved in exceptional cases; in the other cases, the absolute fluxes can be off their real values by an order of magnitude due to slit losses (for the programme star and/or the reference star) and to non-photometric wheather. Uncertainties in the relative values of fluxes along each spectrum are described in the paper.
622. Line lists
ID:
ivo://CDS.VizieR/J/MNRAS/447/492
Title:
Line lists
Short Name:
J/MNRAS/447/492
Date:
21 Oct 2021
Publisher:
CDS
Description:
Knowledge of the elemental abundances of symbiotic giants is essential to address the role of chemical composition in the evolution of symbiotic binaries, to map their parent population, and to trace their mass transfer history. However, there are few symbiotic giants for which the photospheric abundances are fairly well determined. This is the second in a series of papers on chemical composition of symbiotic giants determined from high-resolution (R~50000) near-IR spectra. Results are presented for the late-type giant star in the AE Ara, BX Mon, KX TrA, and CL Sco systems. Spectrum synthesis employing standard local thermal equilibrium (LTE) analysis and stellar atmosphere models were used to obtain photospheric abundances of CNO and elements around the iron peak (Sc, Ti, Fe, and Ni). Our analysis resulted in sub-solar metallicities in BX Mon, KX TrA, and CL Sco by [Fe/H]~-0.3 or -0.5 depending on the value of microturbulence. AE Ara shows metallicity closer to solar by ~0.2 dex. The enrichment in ^14^N isotope found in all these objects indicates that the giants have experienced the first dredge-up. In the case of BX Mon first dredge-up is also confirmed by the low ^12^C/^13^C isotopic ratio of ~8.
623. Lines and continuum sky emission in the NIR
ID:
ivo://CDS.VizieR/J/A+A/581/A47
Title:
Lines and continuum sky emission in the NIR
Short Name:
J/A+A/581/A47
Date:
21 Oct 2021
Publisher:
CDS
Description:
Determining the intensity of lines and continuum airglow emission in the H-band is important for the design of faint-object infrared spectrographs. Existing spectra at low/medium resolution cannot disentangle the true sky-continuum from instrumental effects (e.g. diffuse light in the wings of strong lines). We aim to obtain, for the first time, a high resolution infrared spectrum deep enough to set significant constraints on the continuum emission between the lines in the H-band. During the second commissioning run of the GIANO high-resolution spectrograph at the La Palma Observatory, we pointed the instrument directly to the sky and obtained a deep spectrum that extends from 0.97 to 2.4 micron and includes the whole H-band. The spectrum shows about 1500 emission lines, a factor of two more than in previous works. Of these, 80% are identified as OH transitions; half of these are from highly excited molecules (hot-OH component). The other lines are attributable to O_2_ or unidentified. Several of the faint lines are in spectral regions that were previously believed to be free of lines emission. The continuum in the H-band is marginally detected at a level of about 300photons/m^2^/s/arcsec^2^/um. The observed spectrum and the list of observed sky-lines are published in electronic format. Our measurements indicate that the sky continuum in the H-band could be even darker than previously believed. However, the myriad of airglow emission lines severely limits the spectral ranges where very low background can be effectively achieved with low/medium resolution spectrographs. We identify a few spectral bands that could still remain quite dark at the resolving power foreseen for VLT-MOONS (R~6,600).
624. Lines in the infrared solar spectrum
ID:
ivo://CDS.VizieR/J/A+AS/113/71
Title:
Lines in the infrared solar spectrum
Short Name:
J/A+AS/113/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
We list 603 spectral lines between 1.0, 1.8um that are judged to be relatively unblended from a visual inspection of spectra of the quiet sun. Much of the atomic data of relevance to studies of solar and stellar magnetism, convection and atmospheric structure are also provided. Particular attention is paid to blending by telluric lines. We determine the level of blending both in the presence and the absence of telluric lines. We also describe how telluric blends may be removed from spectra with high spectral resolution.
625. Linking high- and low-mass star formation
ID:
ivo://CDS.VizieR/J/A+A/657/A70
Title:
Linking high- and low-mass star formation
Short Name:
J/A+A/657/A70
Date:
21 Mar 2022 09:28:51
Publisher:
CDS
Description:
Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades in source luminosity. We performed spectral energy distribution (SED) fitting on archival broadband photometric continuum data from 1.2 to 850 microns, to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling density and temperature profiles with the radiative transfer package Transphere. The envelope masses, densities at 1000AU, outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in the literature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses and luminosities, which helps more firmly establish the continuity between low- and high-mass star formation mechanisms. Our density power law indices are consistent with observed values in literature, which show no discernible trends with luminosity. Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable from trends in the same variables for low- and intermediate-mass protostars.
626. Linking ice and gas. Serpens SVS4
ID:
ivo://CDS.VizieR/J/A+A/643/A48
Title:
Linking ice and gas. Serpens SVS4
Short Name:
J/A+A/643/A48
Date:
21 Oct 2021
Publisher:
CDS
Description:
The interaction between dust, ice, and gas during the formation of stars produces complex organic molecules. While observations indicate that several species are formed on ice-covered dust grains and are released into the gas phase, the exact chemical interplay between solid and gas phases and their relative importance remain unclear. Our goal is to study the interplay between dust, ice, and gas in regions of low-mass star formation through ice- and gas- mapping and by directly measuring gas-to-ice ratios. This provides constraints on the routes that lead to the chemical complexity that is observed in solid and gas phases. We present observations of gas-phase methanol (CH_3_OH) and carbon monoxide (^13^CO and C^18^O) at 1.3mm towards ten low-mass young protostars in the Serpens SVS4 cluster from the SubMillimeter Array (SMA) and the Atacama Pathfinder EXperiment (APEX) telescope. We used archival data from the Very Large Telescope (VLT) to derive abundances of ice H_2_O, CO, and CH_3_OH towards the same region. Finally, we constructed gas-ice maps of SVS4 and directly measured CO and CH_3_OH gas-to-ice ratios. The SVS4 cluster is characterised by a global temperature of 15+/-5K. At this temperature, the chemical behaviours of CH_3_OH and CO are anti-correlated: larger variations are observed for CH_3_OH gas than for CH_3_OH ice, whereas the opposite is seen for CO. The gas-to-ice ratios (N_gas_/N_ice_) range from 1-6 for CO and 1.4x10^-4^-3.7x10^-3^for CH_3_OH. The CO gas-maps trace an extended gaseous component that is not sensitive to the effect of freeze-out. Because of temperature variations and dust heating around 20K, the frozen CO is efficiently desorbed. The CH_3_OH gas-maps, in contrast, probe regions where methanol is predominantly formed and present in ices and is released into the gas phase through non-thermal desorption mechanisms. Combining gas- and ice-mapping techniques, we measure gas-to-ice ratios of CO and CH_3_OH in the SVS4 cluster. The CH_3_OH gas-to-ice ratio agrees with values that were previously reported for embedded Class 0/I low-mass protostars. We find that there is no straightforward correlation between CO and CH_3_OH gas with their ice counterparts in the cluster. This is likely related to the complex morphology of SVS4: the Class 0 protostar SMM4 and its envelope lie in the vicinity, and the outflow associated with SMM4 intersects the cluster. This study serves as a pathfinder for future observations with ALMA and the James Webb Space Telescope (JWST) that will provide high-sensitivity gas-ice maps of molecules more complex than methanol. Such comparative maps will be essential to constrain the chemical routes that regulate the chemical complexity in star-forming regions.
627. L1489IRS observed by the submillimeter array
ID:
ivo://CDS.VizieR/J/A+A/475/915
Title:
L1489IRS observed by the submillimeter array
Short Name:
J/A+A/475/915
Date:
21 Oct 2021
Publisher:
CDS
Description:
Submillimeter Array observations of the Young Stellar Object L1489IRS (IRAS 04016+2610). These include images of the continuum at 267 GHz (1.12 mm) and line emission of the HCO+ J=3-2 transition at 267.55762 GHz. The HCO+ image is available in two different (u,v)-weighting schemes, natural and uniform, optimizing for S/N and resolution respectively. The continuum image is only available in uniform weighting. The synthesized beam size is 1".
628. L379IRS3 radio lines
ID:
ivo://CDS.VizieR/J/AZh/93/409
Title:
L379IRS3 radio lines
Short Name:
J/AZh/93/409
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of spectral observations of the region of massive star formation L379IRS3 (IRAS 18265-1517) are presented. The observations were carried out with the 30-m Pico Veleta radio telescope (Spain) at seven frequencies in the 1-mm, 2-mm, and 3-mm wavelength bands. Lines of 24 molecules were detected, from simple diatomic or triatomic species to complex eight- or nine-atom compounds such as CH_3_OCHO or CH_3_OCH_3_. Rotation diagrams constructed from methanol and methyl cyanide lines were used to determine the temperature of the quiescent gas in this region, which is about 40-50K. In addition to this warm gas, there is a hot component that is revealed through high-energy lines of methanol and methyl cyanide, molecular lines arising in hot regions, and the presence of H_2_O masers and Class II methanol masers at 6.7GHz, which are also related to hot gas. One of the hot regions is probably a compact hot core, which is located near the southern submillimeter peak and is related to a group of methanol masers at 6.7GHz. High-excitation lines at other positions may be associated with other hot cores or hot post-shock gas in the lobes of bipolar outflows. The rotation diagrams can be use to determine the column densities and abundances of methanol (10^-9^) and methyl cyanide (about 10^-11^) in the quiescent gas. The column densities of A- and E-methanol in L379IRS3 are essentially the same. The column densities of other observed molecules were calculated assuming that the ratios of the molecular level abundances correspond to a temperature of 40 K. The molecular composition of the quiescent gas is close to that in another region of massive star formation, DR21(OH). The only appreciable difference is that the column density of SO2 in L379IRS3 is at least a factor of 20 lower than the value in DR21(OH). The SO_2_/CS and SO2/OCS abundance ratios, which can be used as chemical clocks, are lower in L379IRS3 than in DR21(OH), suggesting that L379IRS3 is probably younger than DR21(OH).
629. L1551 ISOCAM observations
ID:
ivo://CDS.VizieR/J/A+A/420/945
Title:
L1551 ISOCAM observations
Short Name:
J/A+A/420/945
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a deep mid-IR ISOCAM survey of the L1551 dark molecular cloud are presented. The aim of this survey is a search for new YSO (Young Stellar Object) candidates, using two broad-band filters centred at 6.7 and 14.3{mu}m. Although two regions close to the centre of L1551 had to be avoided due to saturation problems, 96 sources were detected in total (76 sources at 6.7{mu}m and 44 sources at 14.3{mu}m). Using the 24 sources detected in both filters, 14 were found to have intrinsic mid-IR excess at 14.3{mu}m and were therefore classified as YSO candidates. Using additional observations in B, V, I, J, H and K obtained from the ground, most candidates detected at these wavelengths were confirmed to have mid-IR excess at 6.7{mu}m as well, and three additional YSO candidates were found.
630. LMC AGB stars IRAS fluxes
ID:
ivo://CDS.VizieR/J/ApJ/348/98
Title:
LMC AGB stars IRAS fluxes
Short Name:
J/ApJ/348/98
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a search for optically obscured asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), combining data obtained using the IRAS satellite with near-infrared photographic plate material of a 15deg^2^ region in the northern LMC. Of the 156 IRAS sources that are detected either in separate cross-scans or in more than one passband, 63 have [12-25] colors consistent with their being either stellar photospheres or circumstellar dust shells. Seventeen of these we identify with bright (I_c_<9) foreground stars in our own Galaxy, while a further 17 are associated with red supergiants in the LMC. Of the remaining stars, no more than five are likely to be optically visible AGB stars, while the rest have no obvious optical counterpart. This immediately rules out the presence of sufficient high-luminosity "cocoon" stars to explain the observed deficit of several hundred luminous (M_bol_<-6) AGB stars between the predictions of standard models of AGB evolution and the observed luminosity function. It remains possible that most of the unidentified sources are dusty AGB stars, evolving through a phase of enhanced mass loss toward becoming planetary nebulae. We infer bolometric magnitudes as low as M_bol_~-5 for these sources and suggest that this phase can be triggered at low luminosities, truncating AGB evolution and leading to the observed scarcity of asymptotic giant branch stars with bolometric magnitudes brighter than -6.0mag.