- ID:
- ivo://CDS.VizieR/J/MNRAS/441/343
- Title:
- Highly eccentric detached eclipsing binaries
- Short Name:
- J/MNRAS/441/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Next-generation synoptic photometric surveys will yield unprecedented (for the astronomical community) volumes of data and the processes of discovery and rare-object identification are, by necessity, becoming more autonomous. Such autonomous searches can be used to find objects of interest applicable to a wide range of outstanding problems in astronomy, and in this paper we present the methods and results of a largely autonomous search for highly eccentric detached eclipsing binary systems in the Machine-learned All-Sky Automated Survey Classification Catalog. 106 detached eclipsing binaries with eccentricities of e>~0.1 are presented, most of which are identified here for the first time. We also present new radial-velocity curves and absolute parameters for six of those systems with the long-term goal of increasing the number of highly eccentric systems with orbital solutions, thereby facilitating further studies of the tidal circularization process in binary stars.
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- ID:
- ivo://CDS.VizieR/J/AJ/156/179
- Title:
- Highly r-process-enhanced field stars kinematics
- Short Name:
- J/AJ/156/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the kinematics of 35 highly r-process-enhanced ([Eu/Fe]>=+0.7) metal-poor (-3.8<[Fe/H]< -1.4) field stars. We calculate six-dimensional positions and velocities, evaluate energies and integrals of motion, and compute orbits for each of these stars using parallaxes and proper motions from the second Gaia data release (Cat. I/345) and published radial velocities. All of these stars have halo kinematics. Most stars (66%) remain in the inner regions of the halo (<13 kpc), and many (51%) have orbits that pass within 2.6 kpc of the Galactic center. Several stars (20%) have orbits that extend beyond 20 kpc, including one with an orbital apocenter larger than the Milky Way virial radius. We apply three clustering methods to search for structure in phase space, and we identify eight groups. No abundances are considered in the clustering process, but the [Fe/H] dispersions of the groups are smaller than would be expected by random chance. The orbital properties, clustering in phase space and metallicity, and the lack of highly r-process-enhanced stars on disk-like orbits, indicate that such stars likely were accreted from disrupted satellites. Comparison with the galaxy luminosity-metallicity relation suggests M_V_>~-9 for most of the progenitor satellites, characteristic of ultra-faint or low-luminosity classical dwarf spheroidal galaxies. Environments with low rates of star formation and Fe production, rather than the nature of the r-process site, may be key to obtaining the [Eu/Fe] ratios found in highly r-process-enhanced stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1293
- Title:
- High precision orbits of 5 SB2 stars
- Short Name:
- J/ApJ/719/1293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision radial velocities (RVs) of double-lined spectroscopic binary stars HD78418, HD123999, HD160922, HD200077, and HD210027. They were obtained based on the high-resolution echelle spectra collected with the Keck I/HIRES, Shane/CAT/Hamspec, and TNG/Sarge telescopes/spectrographs over the years 2003-2008 as part of the TATOOINE search for circumbinary planets. The RVs were computed using our novel iodine cell technique for double-line binary stars, which relies on tomographically disentangled spectra of the components of the binaries. The precision of the RVs is of the order of 1-10m/s, and to properly model such measurements one needs to account for the light-time effect within the binary's orbit, relativistic effects, and RV variations due to tidal distortions of the components of the binaries. With such proper modeling, our RVs combined with the archival visibility measurements from the Palomar Testbed Interferometer (PTI) allow us to derive very precise spectroscopic/astrometric orbital and physical parameters of the binaries.
- 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/898/150
- Title:
- High-res. MIKE obs. of metal-poor stars
- Short Name:
- J/ApJ/898/150
- Date:
- 21 Mar 2022 08:50:22
- Publisher:
- CDS
- Description:
- Extensive progress has recently been made in our understanding of heavy-element production via the r-process in the universe, specifically with the first observed neutron star binary merger (NSBM) event associated with the gravitational-wave signal detected by LIGO, GW170817. The chemical abundance patterns of metal-poor r-process-enhanced stars provide key evidence for the dominant site(s) of the r-process and whether NSBMs are sufficiently frequent or prolific r-process sources to be responsible for the majority of r-process material in the universe. We present atmospheric stellar parameters (using a nonlocal thermodynamic equilibrium analysis) and abundances from a detailed analysis of 141 metal-poor stars carried out as part of the R-Process Alliance (RPA) effort. We obtained high-resolution "snapshot" spectroscopy of the stars using the MIKE spectrograph on the 6.5m Magellan Clay telescope at Las Campanas Observatory in Chile. We find 10 new highly enhanced r-II (with [Eu/Fe]>+1.0), 62 new moderately enhanced r-I (+0.3<[Eu/Fe]<~+1.0), and 17 new limited-r ([Eu/Fe]<+0.3) stars. Among those, we find 17 new carbon-enhanced metal-poor (CEMP) stars, of which five are CEMP-no. We also identify one new s-process-enhanced ([Ba/Eu]>+0.5) and five new r/s (0.0<[Ba/Eu]<+0.5) stars. In the process, we discover a new ultra-metal-poor (UMP) star at [Fe/H]=-4.02. One of the r-II stars shows a deficit in {alpha} and Fe-peak elements, typical of dwarf galaxy stars. Our search for r-process-enhanced stars by RPA efforts has already roughly doubled the known r-process sample.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/816/70
- Title:
- High resolution spectra of 3 NGC104 member stars
- Short Name:
- J/ApJ/816/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters are known to host peculiar objects named blue straggler stars (BSSs), significantly heavier than the normal stellar population. While these stars can be easily identified during their core hydrogen-burning phase, they are photometrically indistinguishable from their low-mass sisters in advanced stages of the subsequent evolution. A clear-cut identification of these objects would require the direct measurement of the stellar mass. We used the detailed comparison between chemical abundances derived from neutral and from ionized spectral lines as a powerful stellar "weighing device" to measure stellar mass and to identify an evolved BSS in 47Tucanae. In particular, high-resolution spectra of three bright stars, located slightly above the level of the "canonical" horizontal branch (HB) sequence in the color-magnitude diagram of 47 Tucanae, have been obtained with the UVES spectrograph. The measurements of iron and titanium abundances performed separately from neutral and ionized lines reveal that two targets have stellar parameters fully consistent with those expected for low-mass post-HB objects, while for the other target the elemental ionization balance is obtained only by assuming a mass of ~1.4M_{sun}_, which is significantly larger than the main sequence turn-off mass of the cluster (~0.85M_{sun}_). The comparison with theoretical stellar tracks suggests that this is a BSS descendant possibly experiencing its core helium-burning phase. The large applicability of the proposed method to most of the globular clusters in our Galaxy opens the possibility to initiate systematic searches for evolved BSSs, thus giving access to still unexplored phases of their evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/23
- Title:
- High-resolution spectra of 9 RGB stars in NGC6681
- Short Name:
- J/ApJ/846/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtain high-resolution spectra of nine red giant branch stars in NGC 6681 and perform the first detailed abundance analysis of stars in this cluster. We confirm cluster membership for these stars based on consistent radial velocities of 214.5+/-3.7km/s and find a mean [Fe/H]=-1.63+/-0.07dex and [{alpha}/Fe]=0.42+/-0.11dex. Additionally, we confirm the existence of a Na-O anti-correlation in NGC 6681 and identify two populations of stars with unique abundance trends. With the use of HST photometry from Sarajedini+ (2007AJ....133.1658S) and Piotto+ (2015AJ....149...91P) we are able to identify these two populations as discrete sequences in the cluster CMD. Although we cannot confirm the nature of the polluter stars responsible for the abundance differences in these populations, these results do help put constraints on possible polluter candidates.
