- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/145/39
- Title:
- Differential BV(RI)c light curves of PY Vir
- Short Name:
- J/AJ/145/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Complete CCD photometric light curves in BV(RI)_c_ bands obtained in 2012 for the short-period close binary system PY Virginis are presented. A new photometric analysis with the Wilson-Van Hamme code shows that PY Vir is an A-type marginal contact binary system. The absolute parameters of PY Vir are derived using spectroscopic and photometric solutions. Combining new determined times of minimum light with others published in the literature, the O-C diagram of the binary star is investigated. A periodic variation, with a period of 5.22(+/-0.05)years and an amplitude of 0.0075(+/-0.0004)days, was discovered. Since the spectrum of a third component has been detected by Rucinski et al. (2008, cat. J/AJ/136/586), we consider this cyclic period oscillation to be the result of the light-time effect due to the presence of a third body. This third component may also be a binary itself. Therefore, PY Vir should be a quadruple system composed of two cool-type binary systems. This system is a good astrophysical laboratory to study the formation and evolution of close binaries and multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/147/50
- Title:
- Differential BVRI light curves of DV Psc
- Short Name:
- J/AJ/147/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present six new BVR_c_I_c_ CCD light curves of a short-period RS CVn binary DV Psc obtained in 2010-2012. The light curve distortions change on both short and long timescales, which is explained by two starspots on the primary component. Moreover, five new flare events were detected and the flare ratio of DV Psc is about 0.082 flares per hour. There is a possible relation between the phases (longitude) of the flares and starspots for all of the available data of late-type binaries, which implies a correlation of the stellar activity of the spots and flares. The cyclic oscillation, with a period of 4.9+/-0.4yr, may result from the magnetic activity cycle, identified by the variability of Max.I-Max.II. Until now, there were no spectroscopic studies of chromospheric activity indicators of the H_{beta}_and H_{gamma}_lines for DV Psc. Our observations of these indicators show that DV Psc is active, with excess emissions. The updated O-C diagram with an observing time span of about 15yr shows an upward parabola, which indicates a secular increase in the orbital period of DV Psc. The orbital period secularly increases at a rate of dP/dt=2.0x10^-7^days/yr, which might be explained by the angular momentum exchanges or mass transfer from the secondary to primary component.
- ID:
- ivo://CDS.VizieR/J/AJ/146/79
- Title:
- Differential BVRI light curves of EP And
- Short Name:
- J/AJ/146/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New multi-color CCD photometric light curves of the eclipsing binary EP And were obtained over six nights in 2006, 2011, and 2012. Using the Wilson-Devinney code, we computed the photometric elements of this system. It was discovered that EP And is a W-type W UMa contact binary system with a mass ratio of q=2.685 and a degree of contact factor f=24.9%, rather than an A-type system. Combining 28 newly determined times of minimum light derived from 1999 to 2012 with others collected from the literature, a long-term increase (dP/dt=+5.22x10^-8^days/yr) with a sinusoidal variation (A=0.0109days; T=40.89yr) in the orbital period was found. The orbital period secular increases may be interpreted as conservative mass transfer from the less massive component to the more massive one, and cyclic variations of the orbital period may be caused by the light-travel time effect through the presence of a third body. The evolutionary status and the age of the system are also discussed.