- ID:
- ivo://CDS.VizieR/J/AJ/155/138
- Title:
- WOCS.LXXVI.Velocity & abundances in NGC2506
- Short Name:
- J/AJ/155/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HYDRA spectra of 287 stars in the field of NGC 2506 from the turnoff through the giant branch are analyzed. With previous data, 22 are identified as probable binaries; 90 more are classified as potential non-members. Spectroscopic analyses of ~60 red giants and slowly rotating turnoff stars using line equivalent widths and a neural network approach lead to [Fe/H]=-0.27+/-0.07 (s.d.) and [Fe/H]=-0.27+/-0.06 (s.d.), respectively. Li abundances are derived for 145 probable single-star members, 44 being upper limits. Among turnoff stars outside the Li-dip, A(Li)=3.04+/-0.16 (s.d.), with no trend with color, luminosity, or rotation speed. Evolving from the turnoff across the subgiant branch, there is a well-delineated decline to A(Li)~1.25 at the giant branch base, coupled with the rotational spindown from between ~20 and 70 km/s to less than 20 km/s for stars entering the subgiant branch and beyond. A(Li) remains effectively constant from the giant branch base to the red giant clump level. A new member above the clump redefines the path of the first-ascent red giant branch; its Li is 0.6 dex below the first-ascent red giants. With one exception, all post-He-flash stars have upper limits to A(Li), at or below the level of the brightest first-ascent red giant. The patterns are in excellent qualitative agreement with the model predictions for low/intermediate-mass stars which undergo rotation-induced mixing at the turnoff and subgiant branch, first dredge-up, and thermohaline mixing beyond the red giant bump.
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- ID:
- ivo://CDS.VizieR/J/AJ/160/169
- Title:
- WOCS. LXXXII. Orbital parameters & RVs in NGC 7789
- Short Name:
- J/AJ/160/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extensive time-series radial-velocity (RV) survey of stars in the rich open cluster NGC7789 (1.6Gyr, [Fe/H]=+0.02). The stellar sample lies within an 18' circular radius from the cluster center (10pc in projection, or about 2core radii), and includes giants, red clump stars, blue stragglers, red stragglers, sub-subgiants, and main-sequence stars down to 1mag below the turnoff. Our survey began in 2005 and comprises more than 9000 RV measurements from the Hydra Multi-Object Spectrograph on the WIYN 3.5m telescope. We identify 624 likely cluster members and present the orbital solutions for 81 cluster binary stars with periods between 1.45 and 4200days. From the main-sequence binary solutions we fit a circularization period of 7.2_-1.1_^+0.6^days. We calculate an incompleteness-corrected main- sequence binary frequency of 31%{+/-}4% for binaries with periods less than 104days, similar to other WIYN Open Cluster Survey (WOCS) open clusters of all ages. We detect a blue straggler binary frequency of 33%{+/-}17%, consistent with the similarly aged open cluster NGC6819. We also find one secure, rapidly rotating sub-subgiant and one red straggler candidate in our sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/L20
- Title:
- Wolf 1061 velocities and planet candidates
- Short Name:
- J/ApJ/817/L20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use archival HARPS spectra to detect three planets orbiting the M3 dwarf Wolf 1061 (GJ 628). We detect a 1.36M_{Earth}_ minimum-mass planet with an orbital period P=4.888days (Wolf 1061b), a 4.25M_{Earth}_ minimum-mass planet with orbital period P=17.867days (Wolf 1061c), and a likely 5.21M_{Earth}_ minimum-mass planet with orbital period P=67.274days (Wolf 1061d). All of the planets are of sufficiently low mass that they may be rocky in nature. The 17.867day planet falls within the habitable zone for Wolf 1061 and the 67.274day planet falls just outside the outer boundary of the habitable zone. There are no signs of activity observed in the bisector spans, cross-correlation FWHMs, calcium H & K indices, NaD indices, or H{alpha} indices near the planetary periods. We use custom methods to generate a cross-correlation template tailored to the star. The resulting velocities do not suffer the strong annual variation observed in the HARPS DRS velocities. This differential technique should deliver better exploitation of the archival HARPS data for the detection of planets at extremely low amplitudes.
- ID:
- ivo://CDS.VizieR/J/AJ/160/62
- Title:
- 2018-2019 Xinglong BVR photometry of V0599 Aur
- Short Name:
- J/AJ/160/62
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- Combining all available photometric data from various surveys and literature with our observations, we present 10 sets of light curves for the eclipsing binary V0599 Aur covering a timescale of 20 yr. During the last two decades, the O'Connell effect continuously varied and went through at least two flips between positive and negative effects. The photometric solutions from our two sets of multicolored light curves show that V0599 Aur is a W-type shallow contact binary with an active spot on the secondary. Its absolute parameters are determined by combining the Gaia distance with the photometric solutions. The period investigation reveals a secular decrease and a cyclic variation in its orbital period. The former mainly originates from the mass transfer from the more massive secondary to the less massive primary. The latter can be preferentially explained as a result of cyclic magnetic activity of the secondary, with three observational supports: (1) the existence and evolution of an active spot suggested by the long-term photometry, (2) periodic variation in both the O'Connell effect and relative luminosity, and (3) weak correlations between O'Connell effect/relative luminosity changes and cyclic period variation. Together with the cyclic period variation and its theoretical reasonability by Applegate's mechanism, we suggest that the secondary of V0599 Aur is a solar-type magnetic-activity star with an approximately 11 yr active cycle. Furthermore, by combining the secular period decrease with the Roche-lobe model, we infer that V0599 Aur is evolving from the marginal contact state controlled by thermal relaxation oscillation theory to the overcontact state.
- ID:
- ivo://CDS.VizieR/J/A+A/439/1149
- Title:
- XMM spectroscopy of TWA 5
- Short Name:
- J/A+A/439/1149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of X-ray spectroscopy for TWA 5, a member of the young TW Hydrae association, observed with XMM-Newton. TWA 5 is a multiple system which shows H{alpha} emission, a signature typical of classical T Tauri stars, but no infrared excess. From this analysis of the RGS and EPIC spectra, we have derived the emission measure distribution vs. temperature of the X-ray emitting plasma, its abundances, and the electron density.
- ID:
- ivo://CDS.VizieR/J/ApJ/820/87
- Title:
- XO-4b 3yr observations with DEMONEX
- Short Name:
- J/ApJ/820/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The DEdicated MONitor of EXotransits (DEMONEX) was a 20-inch robotic and automated telescope to monitor bright stars hosting transiting exoplanets to discover new planets and improve constraints on the properties of known transiting planetary systems. We present results for the misaligned hot Jupiter XO-4b containing seven new transits from the DEMONEX telescope, including three full and four partial transits. We combine these data with archival light curves and archival radial velocity measurements to derive the host star mass M_{star}_=1.293_-0.029_^+0.030^M_{sun}_ and radius R_{star}_=1.554_-0.030_^+0.042^R_{sun}_, the planet mass M_P_=1.615_-0.099_^+0.10^M_J_ and radius R_P_=1.317_-0.029_^+0.040^R_J_, and a refined ephemeris of P=4.1250687+/-0.0000024days and T_0_=2454758.18978+/-0.00024BJD_TDB_. We include archival Rossiter-McLaughlin measurements of XO-4 to infer the stellar spin-planetary orbit alignment of {lambda}=-40.0_-7.5_^+8.8^deg. We test the effects of including various detrend parameters, theoretical and empirical mass-radius relations, and Rossiter-McLaughlin models. We infer that detrending against CCD position and time or airmass can improve data quality but can have significant effects on the inferred values of many parameters--most significantly R_p_/R_{star}_ and the observed central transit times T_C_. In the case of R_p_/R_{star}_ we find that the systematic uncertainty due to detrending can be three times that of the quoted statistical uncertainties. The choice of mass-radius relation has little effect on our inferred values of the system parameters. The choice of Rossiter-McLaughlin models can have significant effects on the inferred values of vsinI_{star}_ and the stellar spin-planet orbit angle {lambda}.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/L10
- Title:
- XO-2N and XO-2S equivalent widths
- Short Name:
- J/ApJ/801/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of exoplanet host stars is an important factor in understanding the formation and characteristics of their orbiting planets. The best example of this to date is the planet-metallicity correlation. Other proposed correlations are thus far less robust, in part due to uncertainty in the chemical history of stars pre- and post-planet formation. Binary host stars of similar type present an opportunity to isolate the effects of planets on host star abundances. Here we present a differential elemental abundance analysis of the XO-2 stellar binary, in which both G9 stars host giant planets, one of which is transiting. Building on our previous work, we report 16 elemental abundances and compare the {Delta}(XO-2N-XO-2S) values to elemental condensation temperatures. The {Delta}(N-S) values and slopes with condensation temperature resulting from four different pairs of stellar parameters are compared to explore the effects of changing the relative temperature and gravity of the stars. We find that most of the abundance differences between the stars depend on the chosen stellar parameters, but that Fe, Si, and potentially Ni are consistently enhanced in XO-2N regardless of the chosen stellar parameters. This study emphasizes the power of binary host star abundance analysis for probing the effects of giant planet formation, but also illustrates the potentially large uncertainties in abundance differences and slopes induced by changes in stellar temperature and gravity.
1448. XO-2N and XO-2S spectra
- ID:
- ivo://CDS.VizieR/J/A+A/583/A135
- Title:
- XO-2N and XO-2S spectra
- Short Name:
- J/A+A/583/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binary stars hosting exoplanets are a unique laboratory where chemical tagging can be performed to measure with high accuracy the elemental abundances of both stellar components, with the aim to investigate the formation of planets and their subsequent evolution. Here, we present a high-precision differential abundance analysis of the XO-2 wide stellar binary based on high resolution HARPS-N@TNG spectra. Both components are very similar K-dwarfs and host planets. Since they formed presumably within the same molecular cloud, we expect they should possess the same initial elemental abundances. We investigate if the presence of planets can cause some chemical imprints in the stellar atmospheric abundances. We measure abundances of 25 elements for both stars with a range of condensation temperature T_C_=40-1741K, achieving typical precisions of ~0.07dex. The North component shows abundances in all elements higher by +0.067+/-0.032dex on average, with a mean difference of +0.078dex for elements with T_C_>800K. The significance of the XO-2N abundance difference relative to XO-2S is at the 2{sigma} level for almost all elements. We discuss the possibility that this result could be interpreted as the signature of the ingestion of material by XO-2N or depletion in XO-2S due to locking of heavy elements by the planetary companions. We estimate a mass of several tens of M_{earth}_ in heavy elements. The difference in abundances between XO-2N and XO-2S shows a positive correlation with the condensation temperatures of the elements, with a slope of (4.7+/-0.9)x10^-5^dex/K, which could mean that both components have not formed terrestrial planets, but that first experienced the accretion of rocky core interior to the subsequent giant planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/13
- Title:
- XO-2S and XO-2N chemical composition
- Short Name:
- J/ApJ/808/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using high-quality spectra of the twin stars in the XO-2 binary system, we have detected significant differences in the chemical composition of their photospheres. The differences correlate strongly with the elements' dust condensation temperature. In XO-2N, volatiles are enhanced by about 0.015dex and refractories are overabundant by up to 0.090dex. On average, our error bar in relative abundance is 0.012dex. We present an early metal-depletion scenario in which the formation of the gas giant planets known to exist around these stars are responsible for a 0.015 dex offset in the abundances of all elements while 20M_{Earth}_ of non-detected rocky objects that formed around XO-2S explain the additional refractory-element difference. An alternative explanation involves the late accretion of at least 20M_{Earth}_of planet-like material by XO-2N, allegedly as a result of the migration of the hot Jupiter detected around that star. Dust cleansing by a nearby hot star as well as age or Galactic birthplace effects can be ruled out as valid explanations for this phenomenon.
- ID:
- ivo://CDS.VizieR/J/AJ/162/189
- Title:
- 125 years light curve of HS Hydrae with DASCH
- Short Name:
- J/AJ/162/189
- Date:
- 16 Mar 2022 11:44:07
- Publisher:
- CDS
- Description:
- HS Hydrae is a short period eclipsing binary (Porb=1.57day) that belongs to a rare group of systems observed to have rapidly changing inclinations. This evolution is due to a third star on an intermediate orbit, and results in significant differences in eclipse depths and timings year to year. Zasche & Paschke revealed that HS Hydrae's eclipses were rapidly fading from view, predicting they would cease around 2022. Using 25 days of photometric data from Sector 009 of the Transiting Exoplanet Survey Satellite (TESS), we find that the primary eclipses for HS Hydrae were only 0.00173{+/-}0.00007mag in depth in March 2019. This data from TESS likely represents the last eclipses detected from HS Hydrae. We also searched the Digitization of the Harvard Astronomical Plate Collection archive for historic data from the system. With a total baseline of over 125yr, this unique combination of data sets-from photographic plates to precision space-based photometry-allows us to trace the emergence and decay of eclipses from HS Hydrae, and further constrain its evolution. Recent TESS observations from Sector 035 confirm that eclipses have ceased for HS Hya, and we estimate they will begin again in 2195.
