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21331. Water masers in M31. I. Recombination lines
ID:
ivo://CDS.VizieR/J/ApJ/826/24
Title:
Water masers in M31. I. Recombination lines
Short Name:
J/ApJ/826/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of a Green Bank Telescope survey for water masers, ammonia (1,1) and (2,2), and the H66{alpha} recombination line toward 506 luminous compact 24{mu}m emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ~10{mu}as/yr astrometry. No new water masers, ammonia lines, or H66{alpha} recombination lines were detected individually or in spectral stacks reaching rms noise levels of ~3mJy and ~0.2mJy, respectively, in 3.1-3.3km/s channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.
21332. Water masers in Orion
ID:
ivo://CDS.VizieR/J/ApJ/493/940
Title:
Water masers in Orion
Short Name:
J/ApJ/493/940
Date:
21 Oct 2021
Publisher:
CDS
Description:
Measurements of the 6_16_ -> 5_23_ line of H_2_O at 1.3cm in the Orion region of star formation are reported. With a spatial resolution of ~0.1", H_2_O maser emission was detected in two regions: Orion BN/KL and Orion S. The well-known masers in the BN/KL region are distributed in a 30"x30" area. The "shell" masers, within the BN/KL region, are distributed in a 2" by 0.5" strip centered on radio source I and are offset from IRc2.
21333. Water maser survey
ID:
ivo://CDS.VizieR/J/AJ/132/1322
Title:
Water maser survey
Short Name:
J/AJ/132/1322
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the most sensitive water maser survey toward Bok globules to date, performed using NASA's 70m antenna at Robledo de Chavela (Spain). We observed 207 positions within the Clemens and Barvainis catalog with a higher probability of harboring a young star, using as selection criteria the presence of radio continuum emission (from submillimeter to centimeter wavelengths), geometric centers of molecular outflows, peaks in maps of high-density gas tracers (NH3 or CS), and IRAS point sources. We have obtained seven maser detections, six of which (in CB 34, CB 54, CB 65, CB 101, CB 199, and CB 232) are reported for the first time here. Most of the water masers we detected are likely to be associated with young stellar objects (YSOs), except for CB 101 (probably an evolved object) and CB 65 (uncertain nature). The water maser in CB 199 shows a relatively high shift (30km/s) of its velocity centroid with respect to the cloud velocity, which is unusual for low-mass YSOs. We speculate that high-velocity masers in this kind of object could be related to episodes of energetic mass loss in close binaries. Alternatively, the maser in CB 199 could be pumped by a protoplanetary or a young planetary nebula. CB 232 is the smallest Bok globule (0.6pc) known to be associated with water maser emission, although it would be superseded by the cases of CB 65 (0.3pc) and CB 199 (0.5pc) if their association with YSOs is confirmed. All our selection criteria have statistically compatible detection rates, except for IRAS sources, which tend to be somewhat worse predictors for the presence of maser emission.
21334. Water maser survey of late-type stars
ID:
ivo://CDS.VizieR/J/PASJ/53/517
Title:
Water maser survey of late-type stars
Short Name:
J/PASJ/53/517
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents new results of a water maser survey of late-type stellar objects at 22.235GHz with the Kashima 34-m radio telescope. We have detected 179 out of 643 observed sources, including 32 new detections. The sources were selected in terms of the IRAS flux density and colors of late-type stars, involving optically observable Mira/semi-regular variables, IRC objects, OH/IR sources and proto-planetary nebulae. We found the highest H_2_O detection rate for the type of stars with a thin dust envelope (Mira/semi-regular variables) among other types of sources. This is attributed to the smaller distances to such stars in the sample. The velocity spread of the H_2_O maser profile has an increasing tendency with the IRAS color, though it becomes more difficult to access this color dependence beyond an edge of the transition of the (oxygen-rich) Asymptotic Giant Branch stars to protoplanetary nebulae in the two-color diagram.
21335. Water maser survey of methanol maser sources
ID:
ivo://CDS.VizieR/J/A+A/434/613
Title:
Water maser survey of methanol maser sources
Short Name:
J/A+A/434/613
Date:
21 Oct 2021
Publisher:
CDS
Description:
High sensitivity observations of the 22GHz water maser emission have been carried out with the Effelsberg 100m radio telescope. The observed sample was 79 candidate high-mass protostellar objects from a flux-limited sample of 6.7GHz methanol sources (Szymczak et al., 2002A&A...392..277S). Water maser emission was found in 41 sources of which 28 were not previously catalogued.
21336. Wavelength calibration
ID:
ivo://CDS.VizieR/J/A+AS/128/409
Title:
Wavelength calibration
Short Name:
J/A+AS/128/409
Date:
21 Oct 2021
Publisher:
CDS
Description:
Thorium-Argon lamps are commonly used as wavelength calibration units at moderately high spectral resolutions because of the richness of the thorium spectrum in the visual. The inclusion of blended lines whose position is assumed to coincide with the laboratory wavelength of the main component is shown to result in a calibration precision significantly worse than the intrinsic random noise limit. In order to avoid this degradation of the calibration, we present resolution-dependent Th-Ar wavelengths in the region 277 to >1000nm for use at pixel-scales (pixel-size expressed in wavelength units) between {lambda}/2.5x10+4 and {lambda}/10+5.
21337. Wavelength Dependence of Galactic UV Extinction
ID:
ivo://CDS.VizieR/III/130
Title:
Wavelength Dependence of Galactic UV Extinction
Short Name:
III/130
Date:
21 Oct 2021
Publisher:
CDS
Description:
A collection of data for 115 extinction curves derived from low-dispersion IUE spectra are presented with normalization to E(B-V)=1. The electronic Atlas of Extinctions contains the list of the stars used, their association membership, and the normalized extinctions for 88 wavelength values between 1260 and 3000 Angstroems.
21339. W49B with H.E.S.S. and Fermi-LAT
ID:
ivo://CDS.VizieR/J/A+A/612/A5
Title:
W49B with H.E.S.S. and Fermi-LAT
Short Name:
J/A+A/612/A5
Date:
21 Oct 2021
Publisher:
CDS
Description:
The supernova remnant (SNR) W49B originated from a core-collapse supernova that occurred between one and four thousand years ago, and subsequently evolved into a mixed-morphology remnant, which is interacting with molecular clouds (MC). Gamma-ray observations of SNR-MC associations are a powerful tool to constrain the origin of Galactic cosmic rays, as they can probe the acceleration of hadrons through their interaction with the surrounding medium and subsequent emission of non-thermal photons. We report the detection of a gamma-ray source coincident with W49B at very high energies (VHE; E>100GeV) with the H.E.S.S. Cherenkov telescopes together with a study of the source with five years of Fermi-LAT high-energy gamma-ray (0.06-300GeV) data. The smoothly connected, combined source spectrum, measured from 60MeV to multi-TeV energies, shows two significant spectral breaks at 304+/-20MeV and 8.4_-2.5_^+2.2^GeV; the latter is constrained by the joint fit from the two instruments. The detected spectral features are similar to those observed in several other SNR-MC associations and are found to be indicative of gamma-ray emission produced through neutral-pion decay.
21340. WDA and WDB apsidal-motion constants
ID:
ivo://CDS.VizieR/J/A+A/543/A67
Title:
WDA and WDB apsidal-motion constants
Short Name:
J/A+A/543/A67
Date:
21 Oct 2021
Publisher:
CDS
Description:
The internal structure constants k_j_ and the radius of gyration are useful tools for investigating the apsidal motion and tidal evolution of close binaries and planetary systems. These parameters are available for various evolutionary phases but they are scarce for the late stages of stellar evolution. To cover this gap, we present here the calculations of the apsidal-motion constants, the fractional radius of gyration, and the gravitational potential energy for two grids of cooling evolutionary sequences of white dwarfs and for neutron star models. The cooling sequences of white dwarfs were computed with LPCODE. An additional alternative to the white dwarf models was also adopted with the MESA code which allows non-stop calculations from the pre main-sequence (PMS) to the white dwarf cooling sequences. Neutron star models were acquired from the NSCool/TOV subroutines. The apsidal-motion constants, the moment of inertia and the gravitational potential energy were computed with a fourth-order Runge-Kutta method. The parameters are made available for four cooling sequences of white dwarfs (DA and DB types): 0.52, 0.57, 0.837 and 1.0M_{sun}_ and for neutron star models covering a mass range from 1.0 up to 2.183M_{sun}_, in 0.1 mass step. We show that, contrary to previously established opinion, the product of the form-factors {beta} and {alpha}, which are related to the moment of inertia, and gravitational potential energy, is not constant during some evolutionary phases. Regardless of the final products of stellar evolution (white dwarfs, neutron stars and perhaps black holes), we found that they recover the initial value of product {alpha}{beta} at the pre main-sequence phase (~0.4). These results may have important consequences for the investigation of the Jacobi virial equation.

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