- 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.
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- 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/ApJ/877/60
- Title:
- YMGs. I. Young binaries & lithium-rich stars
- Short Name:
- J/ApJ/877/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young stars in the solar neighborhood serve as nearby probes of stellar evolution and represent promising targets to directly image self-luminous giant planets. We have carried out an all-sky search for late-type (~K7-M5) stars within 100pc selected primarily on the basis of activity indicators from the Galaxy Evolution Explorer and ROSAT. Approximately 2000 active and potentially young stars are identified, of which we have followed up over 600 with low-resolution optical spectroscopy and over 1000 with diffraction-limited imaging using Robo-AO at the Palomar 1.5m telescope. Strong lithium is present in 58 stars, implying ages spanning ~10-200Myr. Most of these lithium-rich stars are new or previously known members of young moving groups including TWA, {beta}Pic, Tuc-Hor, Carina, Columba, Argus, ABDor, Upper Centaurus Lupus, and Lower Centaurus Crux; the rest appear to be young low-mass stars without connections to established kinematic groups. Over 200 close binaries are identified down to 0.2"-the vast majority of which are new-and will be valuable for dynamical mass measurements of young stars with continued orbit monitoring in the future.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/132
- Title:
- ~30yr of opt. spectroscopy & Vmag obs. of GW Ori
- Short Name:
- J/ApJ/851/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main-sequence hierarchical triple-star system GW Ori. A forward modeling of the ^13^CO and C^18^O J=2-1 transitions permits a measurement of the total stellar mass in this system, 5.29+/-0.09M_{sun}_, and the circumtriple disk inclination, 137.6{deg}+/-2.0{deg}. Optical spectra spanning a 35yr period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a period of 241.50+/-0.05d; a tertiary companion orbits that inner pair with a period of 4218+/-50d. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system (M_A_~2.7M_{sun}_, M_B_~1.7M_{sun}_, M_C_~0.9M_{sun}_) and find strong evidence that at least one of the stellar orbital planes (and likely both) is misaligned with the disk plane by as much as 45{deg}. A V-band light curve spanning 30yr reveals several new ~30-day eclipse events 0.1-0.7mag in depth and a 0.2mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is ~1Myr old.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/74
- Title:
- 27yr of RV observations of HD 219134
- Short Name:
- J/ApJ/821/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nearby (6.5pc) star HD219134 was recently shown by Motalebi+ (2015, J/A+A/584/A72) and Vogt+ (2015ApJ...814...12V) to host several planets, the innermost of which is transiting. We present 27yr of radial velocity (RV) observations of this star from the McDonald Observatory Planet Search program, and 19yr of stellar activity data. We detect a long-period activity cycle measured in the CaII SHK index, with a period of 4230+/-100d (11.7yr), very similar to the 11yr solar activity cycle. Although the period of the Saturn-mass planet HD219134h is close to half that of the activity cycle, we argue that it is not an artifact due to stellar activity. We also find a significant periodicity in the SHK data due to stellar rotation with a period of 22.8d. This is identical to the period of planet f identified by Vogt+ (2015ApJ...814...12V), suggesting that this RV signal might be caused by rotational modulation of stellar activity rather than a planet. Analysis of our RVs allows us to detect the long-period planet HD219134h and the transiting super-Earth HD219134b. Finally, we use our long time baseline to constrain the presence of longer period planets in the system, excluding to 1{sigma} objects with Msini>0.36M_J_ at 12yr (corresponding to the orbital period of Jupiter) and Msini>0.72M_J_ at a period of 16.4yr (assuming a circular orbit for an outer companion).
- ID:
- ivo://CDS.VizieR/J/ApJ/821/89
- Title:
- 12yrs of radial velocity obs. of exoplanet systems
- Short Name:
- J/ApJ/821/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a Doppler survey at Keck combined with NIRC2 K-band adaptive optics (AO) imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter-mass planets out to 20au for a majority of stars in our sample, and we report the discovery of eight new long-period planets, in addition to 20 systems with statistically significant RV trends that indicate the presence of an outer companion beyond 5AU. We combine our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions, and account for variations in our sensitivity to companions among stars in our sample. We estimate the total occurrence rate of companions in our sample to be 52+/-5% over the range 1-20M_Jup_ and 5-20AU. Our data also suggest a declining frequency for gas giant planets in these systems beyond 3-10AU, in contrast to earlier studies that found a rising frequency for giant planets in the range 0.01-3AU. This suggests either that the frequency of gas giant planets peaks between 3 and 10 AU, or that outer companions in these systems have a different semi-major axis distribution than the overall population of gas giant planets. Our results also suggest that hot gas giants may be more likely to have an outer companion than cold gas giants. We find that planets with an outer companion have higher average eccentricities than their single counterparts, suggesting that dynamical interactions between planets may play an important role in these systems.
- ID:
- ivo://CDS.VizieR/J/A+A/605/L11
- Title:
- YZ Ceti radial velocity curve
- Short Name:
- J/A+A/605/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanet surveys have shown that systems with multiple low-mass planets on compact orbits are common. Except for a few cases, however, the masses of these planets are generally unknown. At the very end of the main sequence, host stars have the lowest mass and hence offer the largest reflect motion for a given planet. In this context, we monitored the low-mass (0.13M_{sun}_) M dwarf YZ Cet (GJ 54.1, HIP 5643) intensively and obtained radial velocities and stellar-activity indicators derived from spectroscopy and photometry, respectively. We find strong evidence that it is orbited by at least three planets in compact orbits (Porb=1.97, 3.06, 4.66 days), with the inner two near a 2:3 mean-motion resonance. The minimum masses are comparable to the mass of Earth (Msini=0.75+/-0.13, 0.98+/-0.14, and 1.14+/-0.17M_{earth}_), and they are also the lowest masses measured by radial velocity so far. We note the possibility for a fourth planet with an even lower mass of Msini=0.472+/-0.096 Mearth at Porb=1.04-days. An n-body dynamical model is used to place further constraints on the system parameters. At 3.6 parsecs, YZ Cet is the nearest multi-planet system detected to date.