- ID:
- ivo://CDS.VizieR/J/MNRAS/454/4013
- Title:
- DIBs in Magellanic Clouds and Milky Way
- Short Name:
- J/MNRAS/454/4013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diffuse interstellar bands (DIBs) trace warm neutral and weakly ionized diffuse interstellar medium (ISM). Here we present a dedicated, high signal-to-noise spectroscopic survey of two of the strongest DIBs, at 5780 and 5797{AA}, in optical spectra of 666 early-type stars in the Small and Large Magellanic Clouds, along with measurements of the atomic NaI D and CaII K lines. The resulting maps show for the first time the distribution of DIB carriers across large swathes of galaxies, as well as the foreground Milky Way ISM. We confirm the association of the 5797{AA} DIB with neutral gas, and the 5780{AA} DIB with more translucent gas, generally tracing the star-forming regions within the Magellanic Clouds. Likewise, the NaI D line traces the denser ISM whereas the CaII K line traces the more diffuse, warmer gas. The CaII K line has an additional component at ~200-220km/s seen towards both Magellanic Clouds; this may be associated with a pan-Magellanic halo. Both the atomic lines and DIBs show sub-pc-scale structure in the Galactic foreground absorption; the 5780 and 5797{AA} DIBs show very little correlation on these small scales, as do the CaII K and NaI D lines. This suggests that good correlations between the 5780 and 5797{AA} DIBs, or between CaII K and NaI D, arise from the superposition of multiple interstellar structures. Similarity in behaviour between DIBs and NaI in the Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Milky Way suggests the abundance of DIB carriers scales in proportion to metallicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/225/19
- Title:
- DIBs measurements from SDSS-III APOGEE spectra
- Short Name:
- J/ApJS/225/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High resolution stellar spectroscopic surveys provide massive amounts of diffuse interstellar bands (DIBs) measurements. Data can be used to study the distribution of the DIB carriers and those environmental conditions that favor their formation. In parallel, recent studies have also proved that DIBs extracted from stellar spectra constitute new tools for building the 3D structure of the Galactic interstellar medium (ISM). The amount of details on the structure depends directly on the quantity of available lines of sight. Therefore there is a need to construct databases of high-quality DIB measurements as large as possible. We aim at providing the community with a catalog of high-quality measurements of the 1.5273{mu}m DIB toward a large fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) hot stars observed to correct for the telluric absorption and not used for ISM studies so far. This catalog would complement the extensive database recently extracted from the APOGEE observations and used for 3D ISM mapping. We devised a method to fit the stellar continuum of the hot calibration stars and extracted the DIB from the normalized spectrum. Severe selection criteria based on the absorption characteristics are applied to the results. In particular limiting constraints on the DIB widths and Doppler shifts are deduced from the HI 21cm measurements, following a new technique of decomposition of the emission spectra. From ~16000 available hot telluric spectra we have extracted ~6700 DIB measurements and their associated uncertainties. The statistical properties of the extracted absorptions are examined and our selection criteria are shown to provide a robust dataset. The resulting catalog contains the DIB total equivalent widths, central wavelengths and widths. We briefly illustrate its potential use for the stellar and interstellar communities.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A69
- Title:
- Di-deuterated methanol (CHD2OH) line list
- Short Name:
- J/A+A/659/A69
- Date:
- 14 Mar 2022 07:43:58
- Publisher:
- CDS
- Description:
- Di-deuterated molecules are observed in the earliest stages of star formation at abundances of a few percent relative to their nondeuterated isotopologs, which is unexpected considering the scarcity of deuterium in the interstellar medium. With sensitive observations leading to the detection of a steadily increasing number of di-deuterated species, it is becoming possible to explore successive deuteration chains. The accurate quantification of the column density of di-deuterated methanol is a key piece of the puzzle that is missing in the otherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system and astrochemical template source IRAS 16293-2422. A spectroscopic dataset for astrophysical purposes was built for CHD2OH and made publicly available to facilitate the accurate characterization of this species in astrochemical surveys. The newly computed line list and partition function were used to search for CHD_2_OH toward IRAS 16293-2422 A and B in data from the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS). Only nonblended, optically thin lines of CHD_2_OH were used for the synthetic spectral fitting. The constructed spectroscopic database contains line frequencies and strengths for 7417 transitions in the 0-500GHz frequency range. ALMA-PILS observations in the 329-363GHz range were used to identify 105 unique, nonblended, optically thin line frequencies of CHD2OH for synthetic spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD2OH in IRAS 16293-2422 A and B of 7.5+/-1.1% and 7.7+/-1.2%, respectively. Deuteration in IRAS 16293-2422 is not higher than in other low-mass star-forming regions (L483, SVS13-A, NGC 1333-IRAS2A, -IRAS4A, and -IRAS4B). Di-deuterated molecules consistently have higher D/H ratios than their mono-deuterated counterparts in all low-mass protostars, which may be a natural consequence of H-D substitution reactions as seen in laboratory experiments. The Solar System's natal cloud, as traced by comet 67P/Churyumov-Gerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS 16293-2422, or been partially reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and the consideration of the underlying assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.
- ID:
- ivo://CDS.VizieR/VI/136
- Title:
- Dielectronic Recombination Lines of C+ - SS1
- Short Name:
- VI/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A computed list of transition lines for the atomic ion C^+^ is generated using R-matrix [1], Autostructure [2] and Emissivity [3] codes. These lines are produced by dielectronic recombination and subsequent cascade decays of the low-lying autoionizing states above the threshold of C^2+1^S^e^ with a principal quantum number n<5 for the captured electron. The line list contains 6187 optically-allowed transitions which include many C II lines observed in the astronomical spectra [4]. Beside the transition lines, the data also include level energies for the bound and resonance states, radiative transition probabilities, recombination rate coefficients, and oscillator strengths. A 26-term C^2+^ atomic target was used within an intermediate coupling scheme in the production of these data. The theoretical results for energy and fine structure splitting agree very well with the available experimental data for both resonances and bound states. The data were also validated by comparison to theoretical data previously reported in the literature which include radiative transition probabilities, effective dielectronic recombination rate coefficients and autoionization probabilities.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A118
- Title:
- Differences of atlases of solar spectrum
- Short Name:
- J/A+A/590/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The high-fidelity solar spectral atlas prepared by Delbouille et. al (1973, Liege atlas, Atlas photometrique du spectre solaire de {lambda} 3000 a {lambda} 10000, 1973apds.book.....D) and the atlas by Neckel (1999, Hamburg atlas, 1999SoPh..184..421N) are widely recognised as the most important collection of reference spectra of the Sun at disc centre in the visible wavelength range. The two datasets serve as fundamental resources for many researchers, in particular for chemical abundance analyses. But despite their similar published specifications (spectral resolution and noise level), the shapes of the spectral lines in the two atlases differ significantly and systematically. Knowledge of any instrumental degradations is imperative to fully exploit the information content of spectroscopic data. We seek to investigate the magnitude of these differences and explain the possible sources. We provide the wavelength-dependent correction parameters that need to be taken into account when the spectra are to be compared with synthetic data, for instance.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A8
- Title:
- Differential abundances of open clusters
- Short Name:
- J/A+A/635/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Well studied Open Clusters (OCs) of the Solar neighbourhood are frequently used as reference objects to test galactic and stellar theories. For that purpose their chemical composition needs to be known with a high level of confidence. It is also important to clarify if each OC is chemically homogeneous and if it has a unique chemical signature. The aims of this work are (1) to determine accurate and precise abundances of 22 chemical species (from Na to Eu) in the Hyades, Praesepe and Rupecht 147 using a large number of stars at different evolutionary states, (2) to evaluate the level of chemical homogeneity of these OCs, (3) to compare their chemical signatures. We gathered ~800 high resolution and high signal-to-noise spectra of ~100 members in the three clusters, obtained with the latest memberships based on Gaia DR2 data. We build a pipeline which computes atmospheric parameters and strictly line-by-line differential abundances among twin stars in our sample. With this method we are able to reach a very high precision in the abundances (0.01-0.02dex in most of the elements). We find large differences in the absolute abundances in some elements, which can be attributed to diffusion, NLTE effects or systematics in the analysis. For the three OCs, we find strong correlations in the differential abundances between different pairs of elements. According to our experiment with synthetic data, this can be explained by some level of chemical inhomogeneity. We compare differential abundances of several stars from the Hyades and Praesepe tails: the stars that differ more in chemical abundances also have distinct kinematics, even though they have been identified as members of the tail. It is possible to obtain high precision abundances using a differential analysis even when mixing spectra from different instruments. With this technique we find that the Hyades and Preasepe have the same chemical signature when G dwarfs and K giants are considered. Despite a certain level of inhomogeneity in each cluster, it is still possible to clearly distinguish the chemical signature of the older cluster Ruprecht 147 when compared to the Hyades and Praesepe.
- ID:
- ivo://CDS.VizieR/J/AJ/130/2866
- Title:
- Differential astrometry of {delta} Equulei
- Short Name:
- J/AJ/130/2866
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Delta Equulei is among the most well-studied nearby binary star systems. Results of its observation have been applied to a wide range of fundamental studies of binary systems and stellar astrophysics. It is widely used to calibrate and constrain theoretical models of the physics of stars. We report 27 high-precision differential astrometry measurements of {delta} Equ from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES).
- ID:
- ivo://CDS.VizieR/J/AJ/145/142
- Title:
- Differential BV photometry of {delta} Sco
- Short Name:
- J/AJ/145/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We acquired Johnson BV photometry of the binary Be disk system {delta} Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100days. We were able to reproduce the changes in the magnitude and color of {delta} Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0*10^-9^M_{Sun}_/yr over ~35days can reproduce the observed increase in brightness.
- ID:
- ivo://CDS.VizieR/J/AJ/151/40
- Title:
- Differential BV photometry of 5 variables in M79
- Short Name:
- J/AJ/151/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC 1904). At visual apparent and absolute magnitudes of V=12.20 and M_V_=-3.46, this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near- and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for Population II standard candles, which are four magnitudes brighter than RR Lyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of ~0.53M_{sun}_. We also detected four very hot stars lying above the horizontal branch ("AGB-manque" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RR Lyrae stars, a Type II Cepheid, and a semiregular variable.
- ID:
- ivo://CDS.VizieR/J/AJ/146/146
- Title:
- Differential BV photometry of VV Crv
- Short Name:
- J/AJ/146/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained red-wavelength spectroscopy and Johnson B and V differential photoelectric photometry of the eclipsing binary VV Crv=HR 4821. The system is the secondary of the common proper motion double star ADS 8627, which has a separation of 5.2". VV Crv has an orbital period of 3.144536 days and a low but non-zero eccentricity of 0.085. With the Wilson-Devinney program we have determined a simultaneous solution of our spectroscopic and photometric observations. Those orbital elements produce masses of M_1_=1.978+/-0.010M_{sun}_ and M_2_=1.513+/-0.008M_{sun}_, and radii of R_1_=3.375+/-0.010R_{sun}_ and R_2_=1.650+/-0.008R_{sun}_for the primary and secondary, respectively. The effective temperatures of the two components are 6500K (fixed) and 6638K, so the star we call the primary is the more massive but cooler and larger component. A comparison with evolutionary tracks indicates that the components are metal rich with [Fe/H]=0.3, and the system has an age of 1.2Gyr. The primary is near the end of its main-sequence lifetime and is rotating significantly faster than its pseudosynchronous velocity. The secondary is still well ensconced on the main sequence and is rotating more slowly than its pseudosynchronous rate.