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21961. Thermodynamic quantities of molecular hydrogen
ID:
ivo://CDS.VizieR/J/A+A/595/A130
Title:
Thermodynamic quantities of molecular hydrogen
Short Name:
J/A+A/595/A130
Date:
21 Oct 2021
Publisher:
CDS
Description:
Hydrogen is the most abundant molecule in the Universe. Its thermodynamic quantities dominate the physical conditions in molecular clouds, protoplanetary disks, etc. It is also of high interest in plasma physics. Therefore thermodynamic data for molecular hydrogen have to be as accurate as possible in a wide temperature range. We here rigorously show the shortcomings of various simplifications that are used to calculate the total internal partition function. These shortcomings can lead to errors of up to 40 percent or more in the estimated partition function. These errors carry on to calculations of thermodynamic quantities. Therefore a more complicated approach has to be taken. Seven possible simplifications of various complexity are described, together with advantages and disadvantages of direct summation of experimental values. These were compared to what we consider the most accurate and most complete treatment (case 8). Dunham coefficients were determined from experimental and theoretical energy levels of a number of electronically excited states of H2. Both equilibrium and normal hydrogen was taken into consideration.
21962. Thermonuclear burst oscillations (TBOs) with RXTE
ID:
ivo://CDS.VizieR/J/ApJS/245/19
Title:
Thermonuclear burst oscillations (TBOs) with RXTE
Short Name:
J/ApJS/245/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe a blind uniform search for thermonuclear burst oscillations (TBOs) in the majority of Type I bursts observed by the Rossi X-ray Timing Explorer (RXTE) (2118 bursts from 57 neutron stars). We examined 2-2002Hz power spectra from the Fourier transform in sliding 0.5-2s windows, using fine-binned light curves in the 2-60keV energy range. The significance of the oscillation candidates was assessed by simulations which took into account light-curve variations, dead time, and the sliding time windows. Some of our sources exhibited multi-frequency variability at <~15Hz that cannot be readily removed with light-curve modeling and may have an astrophysical (non-TBO) nature. Overall, we found that the number and strength of potential candidates depends strongly on the parameters of the search. We found candidates from all previously known RXTE TBO sources, with pulsations that had been detected at similar frequencies in multiple independent time windows, and discovered TBOs from SAXJ1810.8-2658. We could not confirm most previously reported tentative TBO detections or identify any obvious candidates just below the detection threshold at similar frequencies in multiple bursts. We computed fractional amplitudes of all TBO candidates and placed upper limits on non-detections. Finally, for a few sources we noted a small excess of candidates with powers comparable to fainter TBOs, but appearing in single independent time windows at random frequencies. At least some of these candidates may be noise spikes that appear interesting due to selection effects. The potential presence of such candidates calls for extra caution if claiming single-window TBO detections.
21963. Thermonuclear X-ray bursts. II. Eddington limit
ID:
ivo://CDS.VizieR/J/ApJ/747/77
Title:
Thermonuclear X-ray bursts. II. Eddington limit
Short Name:
J/ApJ/747/77
Date:
21 Oct 2021
Publisher:
CDS
Description:
Time-resolved X-ray spectroscopy of thermonuclear bursts observed from low-mass X-ray binaries offer a unique tool to measure neutron-star masses and radii. In this paper, we continue our systematic analysis of all the X-ray bursts observed with Rossi X-ray Timing Explorer from X-ray binaries. We determine the events that show clear evidence for photospheric radius expansion and measure the Eddington limits for these accreting neutron stars using the bolometric fluxes attained at the touchdown moments of each X-ray burst. We employ a Bayesian technique to investigate the degree to which the Eddington limit for each source remains constant between bursts. We find that for sources with a large number of radius expansion bursts, systematic uncertainties are at a 5%-10% level. Moreover, in six sources with only pairs of Eddington-limited bursts, the distribution of fluxes is consistent with a ~10% fractional dispersion. This indicates that the spectroscopic measurements of neutron-star masses and radii using thermonuclear X-ray bursts can reach the level of accuracy required to distinguish between different neutron-star equations of state, provided that uncertainties related to the overall flux calibration of X-ray detectors are of comparable magnitude.
21964. Thermonuclear X-ray bursts observed by RXTE
ID:
ivo://CDS.VizieR/J/ApJS/179/360
Title:
Thermonuclear X-ray bursts observed by RXTE
Short Name:
J/ApJS/179/360
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 1187 thermonuclear (type-I) X-ray bursts from public (archival) observations of 48 low-mass X-ray binaries accreting neutron stars by the Rossi X-ray Timing Explorer, spanning 1996 January - 2007 June 3. For each burst, we list results of analysis of data from the Proportional Counter Array, including observed count rates, time-resolved spectroscopy, evolution of the burst lightcurve, and details of the persistent flux and source spectral state at the time of the burst.
21965. The 2RMS catalog in the Zone of Avoidance
ID:
ivo://CDS.VizieR/J/ApJS/245/6
Title:
The 2RMS catalog in the Zone of Avoidance
Short Name:
J/ApJS/245/6
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Two Micron All-Sky Survey (2MASS) Redshift Survey was started two decades ago with the goal of mapping the three-dimensional distribution of an all-sky flux-limited (Ks<11.75mag) sample of ~45000 galaxies. Our first data release presented an unprecedented uniform coverage for most of the celestial sphere, with redshifts for ~98% of our sample. However, we were missing redshifts for ~18% of the catalog entries that were located within the "Zone of Avoidance" (|b|<10{deg})-an important region of the sky for studies of the large-scale structure and cosmic flows. In this second and final data release, we present redshifts for all 1041 2MRS galaxies that previously lacked this information, as well as updated measurements for 27 others.
21966. The RMS survey: ^13^CO observations of YSOs
ID:
ivo://CDS.VizieR/J/A+A/487/253
Title:
The RMS survey: ^13^CO observations of YSOs
Short Name:
J/A+A/487/253
Date:
21 Oct 2021
Publisher:
CDS
Description:
MSX names, positions, observational rms values and molecular line parameters obtained from Gaussian fits to all detected components made towards the RMS sample of massive young stellar object candidates located in the southern Galactic plane.
21967. The RMS survey: water masers of YSOs
ID:
ivo://CDS.VizieR/J/A+A/507/795
Title:
The RMS survey: water masers of YSOs
Short Name:
J/A+A/507/795
Date:
21 Oct 2021
Publisher:
CDS
Description:
The red MSX source (RMS) survey has identified a large sample of candidate massive young stellar objects (MYSOs) and ultra compact (UC) HII regions from a sample of ~2000 MSX and 2MASS colour selected sources. To search for H_2_O masers towards a large sample of young high mass stars and to investigate the statistical correlation of H_2_O masers with the earliest stages of massive star formation. We have used the Mopra Radio telescope to make position-switched observations towards ~500 UCHII regions and MYSOs candidates identified from the RMS survey and located between 190{deg}<l<30{deg}. These observations have a 4{sigma} sensitivity of ~1Jy and a velocity resolution of ~0.4km/s.
21968. The role of the host star's metallicity
ID:
ivo://CDS.VizieR/J/A+A/624/A94
Title:
The role of the host star's metallicity
Short Name:
J/A+A/624/A94
Date:
21 Oct 2021
Publisher:
CDS
Description:
Most of our current understanding of the planet formation mechanism is based on the planet metallicity correlation derived mostly from solar-type stars harbouring gas-giant planets. To achieve a more extensive grasp on the substellar formation process, we aim to analyse in terms of their metallicity a diverse sample of stars (in terms of mass and spectral type) covering the whole range of possible outcomes of the planet formation process (from planetesimals to brown dwarfs and low-mass binaries). Our methodology is based on the use of high-precision stellar parameters derived by our own group in previous works from high-resolution spectra by using the iron ionisation and equilibrium conditions. All values were derived in an homogeneous way, except for the M dwarfs where a methodology based on the use of pseudo equivalent widths of spectral features was used. Our results show that as the mass of the substellar companion increases the metallicity of the host star tends to lower values. The same trend is maintained when analysing stars with low-mass stellar companions and a tendency towards a wide range of host star's metallicity is found for systems with low-mass planets. We also confirm that more massive planets tend to orbit around more massive stars. The core-accretion formation mechanism for planet formation achieves its maximum efficiency for planets with masses in the range 0.2 and 2M_{Jup}_. Substellar objects with higher masses have higher probabilities of being formed as stars. Low-mass planets and planetesimals might be formed by core-accretion even around low-metallicity stars.
21969. The Roma BZCAT - 5th edition
ID:
ivo://CDS.VizieR/VII/274
Title:
The Roma BZCAT - 5th edition
Short Name:
VII/274
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Roma-BZCAT is now at the 5th Edition which contains coordinates and multi-frequency data of 3561 sources, about 30% more than in the 1st edition, either confirmed blazars or exhibiting characteristics close to this type of sources. With respect to the previous editions, this new edition has relevant changes in the sources' classification and has a new format for the notes in the tables. We emphasize that all the sources in the Roma-BZCAT have a detection in the radio band. Moreover, a complete spectroscopic information is published and could be accessed by us for all of them, with the exception of BL Lac candidates. Consequently, peculiar sources as the so called "radio quiet BL Lacs", which are reported in some other catalogues, are not included here because of possible contamination with hot stars and other extragalactic objects.
21970. The ROSAT brightest cluster sample - I.
ID:
ivo://CDS.VizieR/J/MNRAS/301/881
Title:
The ROSAT brightest cluster sample - I.
Short Name:
J/MNRAS/301/881
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a 90 per cent flux-complete sample of the 201 X-ray-brightest clusters of galaxies in the northern hemisphere ({delta}>=0{deg}), at high Galactic latitudes (|b|>= 20{deg}), with measured redshifts z<=0.3 and fluxes higher than 4.4x10^-12^erg/cm^2^/s in the 0.112.4 keV band. The sample, called the ROSAT Brightest Cluster Sample (BCS), is selected from ROSAT All-Sky Survey data and is the largest X-ray-selected cluster sample compiled to date. In addition to Abell clusters, which form the bulk of the sample, the BCS also contains the X-ray-brightest Zwicky clusters and other clusters selected from their X-ray properties alone. Effort has been made to ensure the highest possible completeness of the sample and the smallest possible contamination by non-cluster X-ray sources. X-ray fluxes are computed using an algorithm tailored for the detection and characterization of X-ray emission from galaxy clusters. These fluxes are accurate to better than 15 per cent (mean 1{sigma} error).

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