- ID:
- ivo://CDS.VizieR/J/A+A/333/205
- Title:
- HD 185510 UBV photometry
- Short Name:
- J/A+A/333/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV photometry and moderate resolution H{alpha} spectrophotometry of the evolved binary system HD 185510 (sdB + K0 III), performed at Catania Astrophysical Observatory, is presented and discussed. The spectrophotometric data were collected in 1991, 1993, and 1994, while the photometric light curves were obtained in 1993, 1994 and 1995. From the B and V photometry we determine a new photometric rotational period of 26.23d, confirming the asynchronous rotation of the cool giant component. The spectroscopic data confirm the vsin i value of 15km/s measured by Fekel et al. (1993AJ....106.2370F) and clearly reveal a filled-in H{alpha} line with appreciable variations. The excess emission of the line, observed at any orbital phase, is found to be anticorrelated with the V light curve and is primarily ascribed to the chromospheric activity on the cool star. The primary total eclipse is clearly visible in the U band, but undetectable in the V band. From the U observations we determined a total duration of the primary eclipse (from 1^st^ to 4^rd^ contact) of 1.3883d, with the ingress lasting only 27 minutes. This new accurate monitoring and timing of the eclipse allowed us to improve the system solution which leads to R_C_=8.8R_{sun}_, T_C_=4800K, R_H_=0.11R_{sun}_, T_H_=30000K for the cool and hot star respectively. The evolution of HD 185510B is discussed also in relation to the evolutionary status of HD 185510A and the synchronization time scale. HD 185510B is probably a sdB near the zero age extended horizontal branch, resulting from an enhanced mass loss in late case B or case A mass exchange with a possible common envelope phase. A small amount (15-20%) of mass loss from the system which can account for the strong IR excess is suggested.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/570/A22
- Title:
- Heavy elements in old very metal-rich stars
- Short Name:
- J/A+A/570/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied a sample of high proper motion, old and metal-rich dwarf stars, selected from the NLTT catalogue. The low pericentric distances and eccentric orbits of these solar neighbourhood stars indicate that they might have originated in the inner parts of the Galaxy. Chemical tagging can probe the formation history of stellar populations. To identify the origin of a sample of 71 very metal-rich dwarf stars, we derive the abundances of the neutron-capture elements Y, Ba, La, and Eu. The abundances of Y, La, Ba, and Eu vs. Fe, O, and Mg as reference elements, as well as their kinematics, suggest that our sample of old metal-rich dwarf stars is clearly distinct from the thin disk. They could be old inner thin-disk stars, as suggested previously, or bulge stars. In either cases they would have migrated from the inner parts of the Galaxy to the solar neighbourhood.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A111
- Title:
- 89 Her interferometric study
- Short Name:
- J/A+A/559/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binary post-asymptotic giant branch (post-AGB) stars are interesting laboratories to study both the evolution of binaries as well as the structure of circumstellar disks. A multiwavelength high angular resolution study of the prototypical object 89 Herculis is performed with the aim of identifying and locating the different emission components seen in the spectral energy distribution. A large interferometric data set, collected over the past decade and covering optical and near-infrared wavelengths, is analyzed in combination with the spectral energy distribution and flux-calibrated optical spectra. In this first paper only simple geometric models are applied to fit the interferometric data. Combining the interferometric constraints with the photometry and the optical spectra, we re-assess the energy budget of the post-AGB star and its circumstellar environment.
- ID:
- ivo://CDS.VizieR/J/A+A/650/L17
- Title:
- HERMES spectra of Betelgeuse
- Short Name:
- J/A+A/650/L17
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Despite being the best studied red supergiant star in our Galaxy, the physics behind the photometric variability and mass loss of Betelgeuse is poorly understood. Moreover, recently the star has experienced an unusual fading with its visual magnitude reaching a historical minimum. The nature of this event was investigated by several studies where mechanisms like episodic mass loss and presence of dark spots in the photosphere were invoked. We aim at relating the atmospheric dynamics of Betelgeuse to its photometric variability, with the main focus on the dimming event. We use the tomographic method which allows us to probe different depths in the stellar atmosphere and to recover the corresponding disk-averaged velocity field. The method is applied to a series of high-resolution HERMES observations of Betelgeuse. Variations in the velocity field are then compared with photometric and spectroscopic variations. The tomographic method reveals that the succession of two shocks along our line-of-sight (in February 2018 and January 2019), the second one amplifying the effect of the first one, combined with underlying convection or/and outward motion present at this phase of the 400 d pulsation cycle, produced a rapid expansion of a portion of the atmosphere of Betelgeuse and an outflow between October 2019 and February 2020. This resulted in a sudden increase of molecular opacity in the cooler upper atmosphere of Betelgeuse and, thus, in the observed unusual decrease of the star's brightness.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A109
- Title:
- Herschel/PACS spectra of 48 evolved stars
- Short Name:
- J/A+A/565/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 48 Herschel/PACS spectra of evolved stars in the wavelength range of 67-72um. This wavelength range covers the 69mu band of crystalline olivine (Mg_2-2x_Fe_(2x)_SiO_4_). The width and wavelength position of this band are sensitive to the temperature and composition of the crystalline olivine. Our sample covers a wide range of objects: from high mass-loss rate AGB stars (OH/IR stars, dM/dt>=10^-5^M_{sun}_/yr), through post-AGB stars with and without circumbinary disks, to planetary nebulae and even a few massive evolved stars. The goal of this study is to exploit the spectral properties of the 69um band to determine the composition and temperature of the crystalline olivine. Since the objects cover a range of evolutionary phases, we study the physical and chemical properties in this range of physical environments. We fit the 69um band and use its width and position to probe the composition and temperature of the crystalline olivine. For 27 sources in the sample, we detected the 69um band of crystalline olivine (Mg_2-2x_Fe_(2x)_SiO_4_). The 69um band shows that all the sources produce pure forsterite grains containing no iron in their lattice structure. The temperature of the crystalline olivine as indicated by the 69um band, shows that on average the temperature of the crystalline olivine is highest in the group of OH/IR stars and the post-AGB stars with confirmed Keplerian disks. The temperature is lower for the other post-AGB stars and lowest for the planetary nebulae. A couple of the detected 69um bands are broader than those of pure magnesium-rich crystalline olivine, which we show can be due to a temperature gradient in the circumstellar environment of these stars. The disk sources in our sample with crystalline olivine are very diverse. They show either no 69um band, a moderately strong band, or a very strong band, together with a temperature for the crystalline olivine in their disk that is either very warm (~600K), moderately warm (~200K), or cold (~120K), respectively.
- ID:
- ivo://CDS.VizieR/J/PASJ/57/13
- Title:
- High-dispersion spectra of nearby F-K stars
- Short Name:
- J/PASJ/57/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Towards constructing a system of high-dispersion spectroscopic standard stars with well-established abundances, so that adequate reference stars of similar properties may be found for precise differential abundance studies of any near-solar type stars, we have collected high-resolution (R~70000) echelle spectra for 160 F-K dwarfs and subgiants of the solar neighborhood in three wavelength regions (5000-6200{AA}, 5800-7000{AA}, and 7600-8800{AA}) at Okayama Astrophysical Observatory. This spectra database is open to the public.
- ID:
- ivo://CDS.VizieR/J/AJ/157/245
- Title:
- High-precision radial velocities for HD 221416
- Short Name:
- J/AJ/157/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V=8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 {mu}Hz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R_*_=2.943+/-0.064 R_{sun}_), mass (M_*_=1.212+/-0.074 M_{sun}_), and age (4.9+/-1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (R_p_=9.17+/-0.33 R_{Earth}_) with an orbital period of ~14.3 days, irradiance of F=343+/-24 F_{Earth}_, and moderate mass (M_p_=60.5+/-5.7 M_{Earth}_) and density ({rho}_p_=0.431+/-0.062 g/cm^3^). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R_{Earth}_) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ~15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/40
- Title:
- High resolution NIR RVs of K2-M4 low-mass stars
- Short Name:
- J/ApJ/822/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA InfraRed Telescope Facility in the K band with an isotopologue methane gas cell to achieve wavelength calibration and a novel, iterative RV extraction method. We surveyed 14 members of young (~25-150Myr) moving groups, the young field star {epsilon} Eridani, and 18 nearby (<25pc) low-mass stars and achieved typical single-measurement precisions of 8-15m/s with a long-term stability of 15-50m/s over longer baselines. We obtain the best NIR RV constraints to date on 27 targets in our sample, 19 of which were never followed by high-precision RV surveys. Our results indicate that very active stars can display long-term RV variations as low as ~25-50m/s at ~2.3125{mu}m, thus constraining the effect of jitter at these wavelengths. We provide the first multiwavelength confirmation of GJ876bc and independently retrieve orbital parameters consistent with previous studies. We recovered RV variabilities for HD160934AB and GJ725AB that are consistent with their known binary orbits, and nine other targets are candidate RV variables with a statistical significance of 3{sigma}-5{sigma}. Our method, combined with the new iSHELL spectrograph, will yield long-term RV precisions of <~5m/s in the NIR, which will allow the detection of super-Earths near the habitable zone of mid-M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/112
- Title:
- High-resolution spectra of * bet CMi
- Short Name:
- J/ApJ/836/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The late-type Be star {beta} CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement+ (2015A&A...584A..85K). These results showed that the disk is likely truncated at a finite radius from the star, which Klement et al. suggest is evidence for an unseen binary companion in orbit. Here we report on an analysis of the Ritter Observatory spectroscopic archive of {beta} CMi to search for evidence of the elusive companion. We detect periodic Doppler shifts in the wings of the H{alpha} line with a period of 170 days and an amplitude of 2.25km/s, consistent with a low-mass binary companion (M~0.42M_{sun}_). We then compared small changes in the violet-to-red peak height changes (V/R) with the orbital motion. We find weak evidence that it does follow the orbital motion, as suggested by recent Be binary models by Panoglou et al. Our results, which are similar to those for several other Be stars, suggest that {beta} CMi may be a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no direct sign of this companion star is found in the very limited archive of International Ultraviolet Explorer spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/514/A97
- Title:
- High-resolution spectra of Late-type stars
- Short Name:
- J/A+A/514/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- * Aims: We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood which may be used to investigate different aspects of the formation and evolution of the solar neighborhood in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. * Methods: We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral range simultaneously. Standard data reduction was performed with the IRAF echelle package. We applied the spectral subtraction technique to reveal chromospheric emission in the stars of the sample. The equivalent width of chromospheric emission lines was measured in the subtracted spectra and then converted to fluxes using equivalent width--flux relationships. Radial and rotational velocities were determined by the cross-correlation technique. Kinematics, equivalent widths of the lithium line 6707.8{AA} and spectral types were also determined. * Results: A catalog of spectroscopic data is compiled: radial and rotational velocities, space motion, equivalent widths of optical chromospheric activity indicators from Ca II H & K to the calcium infrared triplet and the lithium line in 6708{AA}. Fluxes in the chromospheric emission lines and R'_HK are also determined for each observation of star in the sample. We used these data to investigate the emission levels of our stars. The study of the H{alpha} emission line revealed the presence of two different populations of chromospheric emitters in the sample, clearly separated in the log(F_H{alpha}_/F_bol_)-(V-J) diagram. The dichotomy may be associated with the age of the stars.
