- ID:
- ivo://CDS.VizieR/J/A+A/559/A85
- Title:
- 1D Lya forest power spectrum
- Short Name:
- J/A+A/559/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-{alpha} forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 (Baryon Oscillation Spectroscopic Survey, BOSS, 2013AJ....145...10D) selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from <z>=2.2 to <z>=4.4, and scales from 0.001(km/s)^-1^ to 0.02(km/s)^-1^. We determine the methodological and instrumental systematic uncertainties of our measurements.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PAZh/43/521
- Title:
- 3D map of reddening and interstellar extinction
- Short Name:
- J/PAZh/43/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An improved version of the 3D stellar reddening map in a space with a radius of 1200 pc around the Sun and within 600 pc of the Galactic midplane is presented. As in the previous 2010 and 2012 versions of the map, photometry with an accuracy better than 0.05 mag in the J and Ks bands for more than 70 million stars from the 2MASS catalogue is used in the new version. However, the data reduction technique is considerably more complicated. As before, an analysis of the distribution of stars near the main-sequence turnoff on the (J-Ks)-Ks diagram, where they form a distribution maximum, provides a basis for the method. The shift of this maximum, i.e., the mode (J-Ks), along (J-Ks) and Ks, given the spatial variations of the mean dereddened color (J-Ks)_0_ of these stars, is interpreted as a growth of the reddening with increasing distance. The main distinction of the new method is that instead of the fixed mean absolute magnitude, dereddened color, distance, and reddening for each cell, the individual values of these quantities are calculated for each star by iterations when solving the system of equations relating them. This has allowed one to increase the random accuracy of the map to 0.01mag and its spatial resolution to 20pc in coordinates and distance and to 1{deg} in longitude and latitude. Comparison with other reddening estimates for the same spatial cells and Gaia DR1 TGAS stars shows that the constructed map is one of the best maps for the space under consideration. Its systematic errors have been estimated to be {sigma}(E(J-Ks)=0.025mag, or {sigma}(E(B-V))=0.04mag. The main purpose of the map is to analyze the characteristics of Galactic structures, clouds, and cloud complexes. For this purpose, the reddening map within each spatial cell has also been computed by analyzing the reddening along each line of sight.
5053. DM Cyg BVIc light curves
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/350
- Title:
- DM Cyg BVIc light curves
- Short Name:
- J/MNRAS/397/350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DM Cyg, a fundamental mode RRab star, was observed in the 2007 and 2008 seasons in the framework of the Konkoly Blazhko Survey. Very small amplitude light-curve modulation was detected with 10.57d modulation period. The maximum brightness and phase variations do not exceed 0.07mag and 7min, respectively. In spite of the very small amplitude of the modulation, beside the frequency triplets characterizing the Fourier spectrum of the light curve, two quintuplet components were also identified. The accuracy and the good phase coverage of our observations made it possible to analyse the light curves at different phases of the modulation separately.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A101
- Title:
- 3D MHD models angular quadratures
- Short Name:
- J/A+A/645/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate angular quadratures are crucial for the numerical solution of three-dimensional (3D) radiative transfer problems, especially when including the spectral line polarisation produced by the scattering of anisotropic radiation. There are two requirements for an optimal quadrature that are difficult to satisfy simultaneously: high accuracy and short computing time. Recently, imposing certain symmetries, we have derived a set of near optimal angular quadratures. Here we extend our previous investigation by considering other symmetries. Moreover, we test the performance of our new quadratures by numerically solving a radiative transfer problem of resonance line polarisation in a 3D model of the solar atmosphere resulting from a magneto-hydrodynamical simulation. The new angular quadratures derived here outperform the previous ones in terms of the number of rays needed to achieve any given accuracy.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A139
- Title:
- 3D non-LTE Balmer line formation
- Short Name:
- J/A+A/615/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For H{alpha}, H{beta}, and H{gamma} we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for H{gamma}, while the inner wings can be weaker in 3D models, particularly for H{alpha}. For H{alpha}, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (Teff~~6500K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (Teff~~4500K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from H{alpha}, H{beta}, and H{gamma}; however the value is too low by around 50K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1{sigma} uncertainties. For H{alpha}, the absolute 3D effects and non-LTE effects can separately reach around 100K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of H{alpha} can underestimate effective temperatures by around 150K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A99
- Title:
- DoAr 44 ugri light curves
- Short Name:
- J/A+A/643/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young stars interact with their accretion disk through their strong magnetosphere. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). We monitored the system over several rotational cycles, combining high-resolution spectropolarimetry at both optical and near-IR wavelengths with long-baseline near-IR inteferometry and multicolor photometry. We derive a rotational period of 2.96d from the system's light curve, which is dominated by stellar spots. We fully characterize the central star's properties from the high signal-to-noise, high-resolution optical spectra we obtained during the campaign. DoAr 44 is a young 1.2M_{sun}_ star, moderately accreting from its disk (Macc=6.510^-9^M_{sun}_/yr), and seen at a low inclination (i~=30{deg}). Several optical and near-IR line profiles probing the accretion funnel flows (H{alpha}, H{beta}, HeI 1083nm, Pa{beta}) and the accretion shock (HeI 587.6nm) are modulated at the stellar rotation period. The most variable line profile is HeI 1083nm, which exhibits modulated redshifted wings that are a signature of accretion funnel flows, as well as deep blueshifted absorptions indicative of transient outflows. The Zeeman-Doppler analysis suggests the star hosts a mainly dipolar magnetic field, inclined by about 20{deg} onto the spin axis, with an intensity reaching about 800G at the photosphere, and up to 2+/-0.8kG close to the accretion shock. The magnetic field appears strong enough to disrupt the inner disk close to the corotation radius, at a distance of about 4.6R* (0.043au), which is consistent with the 5R* (0.047au) upper limit we derived for the size of the magnetosphere in our Paper I from long baseline interferometry. DoAr 44 is a pre-transitional disk system, exhibiting a 25-30au gap in its circumstellar disk, with the inner and outer disks being misaligned. On a scale of 0.1au or less, our results indicate that the system is steadily accreting from its inner disk through its tilted dipolar magnetosphere. We conclude that in spite of a highly structured disk on the large scale, perhaps the signature of ongoing planetary formation, the magnetospheric accretion process proceeds unimpeded at the star-disk interaction level.
5057. 3D observations of S 140
- ID:
- ivo://CDS.VizieR/J/A+A/580/A68
- Title:
- 3D observations of S 140
- Short Name:
- J/A+A/580/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The objective of this work is to study in detail the temperatures of dust and gas in the photon-dominated region S140, especially around the deeply embedded infrared sources IRS1-3 and at the ionization front. We derive the dust temperature and column density by combining Herschel PACS continuum observations with SOFIA observations at 37um and SCUBA data at 450um. We model these observations using simple greybody fits and the DUSTY radiative transfer code. For the gas analysis we use RADEX to model the CO 1-0, CO 2-1, ^13^CO 1-0 and C^18^O 1-0 emission lines mapped with the IRAM-30m telescope over a 4' field. Around IRS 1-3, we use HIFI observations of single-points and cuts in CO 9-8, ^13^CO 10-9 and C^18^O 9-8 to constrain the amount of warm gas
- ID:
- ivo://CDS.VizieR/J/A+A/650/A157
- Title:
- Dolidze 25 Chandra/ACIS-I X-ray sources
- Short Name:
- J/A+A/650/A157
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The dispersal of protoplanetary disks sets the timescale available for planets to assemble, and thus it is one of the fundamental parameters in theories of planetary formation. Disk dispersal is determined by several properties of the central star, the disk itself, and the surrounding environment. In particular, the metallicity of disks may impact their evolution, even if to date controversial results exist: in low-metallicity clusters disks seem to rapidly disperse, while in the Magellanic Clouds some evidence supports the existence of accreting disks few tens of Myrs old. In this paper we study the dispersal timescale of disks in Dolidze 25, the young cluster in proximity of the Sun with lowest metallicity, with the aim of understanding whether disk evolution is impacted by the low-metallicity of the cluster. We have analyzed Chandra/ACIS-I observations of the cluster and combined the resulting source catalog with existing optical and infrared catalogs of the region. We selected the disk-bearing population in a 1 degree circular region centered on Dolidze~25 from criteria based on infrared colors, and the disk-less population within a smaller central region among the X-ray sources with OIR counterpart. In both cases, criteria are applied to discard contaminating sources in the foreground/background. We have derived stellar parameters from isochrones fitted to color-magnitude diagrams. We derived a disk fraction of about 34% and a median age of the cluster of 1.2Myrs. To minimize the impact of incompleteness and spatial inhomogeneity of the list of members, we restricted this calculation to stars in a magnitude range where our selection of cluster members is fairly complete and by adopting different cuts in stellar masses. By comparing this estimate with existing estimates of the disk fraction of clusters younger than 10Myrs, our study suggests that the disk fraction of Dolidze 25 is lower than what is expected from its age alone. Even if our results are not conclusive given the intrinsic uncertainty on stellar ages estimated from isochrones fitting to color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be impacted by the environment. Given the poor O star population and low stellar density of the cluster, it is more likely that disks dispersal timescale is dictated more by the low metallicity of the cluster rather than external photoevaporation or dynamical encounters.
- ID:
- ivo://CDS.VizieR/J/other/IBVS/5185
- Title:
- Dolidze S, C, and MS stars positions
- Short Name:
- J/other/IBVS/518
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of other work I have obtained complete identifications for a problematic list of late-type stars by Dolidze (1975AbaOB..47....3D). The charts were used to make the identifications. Since numerous substantial errors were found that have propagated elsewhere in the literature, it was thought useful to publish the list separately. The corrections allow linkage of the stars to other catalogues in the visible and infrared. This complements a second similar list of late-M stars by Dolidze (Dolidze, 1975AbaOB..47..171D, Skiff, 1997IBVS.4417....1S).
- ID:
- ivo://CDS.VizieR/J/other/RAA/14.1135
- Title:
- Doppler factor for a Fermi blazar sample
- Short Name:
- J/other/RAA/14.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 457 blazars (193 flat spectrum radio quasars, 61 low-synchrotron peaked blazars, 69 intermediate-synchrotron peaked blazars and 134 high-synchrotron peaked blazars) from the second Fermi-LAT catalog (2FGL) of {gamma}-ray sources, which have X-ray observations. We calculated the lower limits for their Doppler factors, {delta}_{gamma}_, and compared the lower limits with the available Doppler factors and the apparent superluminal velocities in the literature.