For Hipparcos M, S, and C spectral type stars, we provide calibrated instantaneous (epoch) Cousins V-I color indices using newly derived HpV_T2_ photometry. Three new sets of ground-based Cousins VI data have been obtained for more than 170 carbon and red M giants, observed at SAAO in 1984 and 1987 (table1), at Siding Spring Observatory in 2002 (table2), and with the Automatic Photoelectric Telescopes located at Fairborn Observatory from 1996 (table3). These datasets in combination with the published sources of VI photometry served to obtain the calibration curves linking Hipparcos/Tycho Hp-V_T2_ with the Cousins V-I index. In total, 321 carbon stars and 4464 M- and S-type stars have new V-I indices. The standard error of the mean V-I is about 0.1mag or better down to Hp~9 although it deteriorates rapidly at fainter magnitudes. These V-I indices can be used to verify the published Hipparcos V-I color indices. Thus, we have identified a handful of new cases where, instead of the real target, a random field star has been observed. A considerable fraction of the DMSA/C and DMSA/V solutions for red stars appear not to be warranted. Most likely such spurious solutions may originate from usage of a heavily biased color in the astrometric processing.
Radial velocities have been determined for a sample of B8-F2 type stars observed by the Hipparcos satellite. Observations were obtained within the framework of an ESO key-program. Radial velocities have been measured using a cross-correlation method, the templates being a grid of synthetic spectra. The obtained precision depends on effective temperature and projected rotational velocity of the star as well as on a possible asymmetry of the correlation peak generally due to secondary components. New spectroscopic binaries have been detected from these a symmetries and the variability of the measured radial velocity. Simulations of binary and triple systems have been performed. For binaries our results have been compared with Hipparcos binary data. Adding the variable radial velocities, the minimum binary fraction has been found 60% for physical systems. Radial velocities have been determined for 581 B8-F2 stars, 159 being new. Taking into account published radial velocities, 39% south A-type stars with V magnitude lower than 7.5 have a radial velocity.
A sample consisting of 570 binary systems is compiled from several sources of visual binary stars with well-known orbital elements. High-precision trigonometric parallaxes (mean relative error about 5%) and proper motions (mean relative error about 3%) are extracted from the Hipparcos Catalogue or from the reprocessed Hipparcos data. However, 13% of the sample stars lack radial velocity measurements. Computed galactic velocity components and other kinematic parameters are used to divide the sample stars into kinematic age groups. The majority (89%) of the sample stars, with known radial velocities, are the thin disk stars, 9.5% binaries have thick disk kinematics and only 1.4% are halo stars. 85% of thin disk binaries are young or medium age stars and almost 15% are old thin disk stars. There is an urgent need to increase the number of the identified halo binary stars with known orbits and substantially improve the situation with their radial velocity data. Based on the data from the Hipparcos astrometry satellite (ESA)
This paper continues kinematical investigation of the Hipparcos visual binaries with known orbits. A sample, consisting of 804 binary systems with orbital elements determined from ground-based observations, is selected. The mean relative error of their parallaxes is about 12% and the mean relative error of proper motions is about 4%. However, even 41% of the sample stars lack radial velocity measurements. The computed Galactic velocity components and other kinematical parameters are used to divide the stars with known radial velocities into kinematical age groups. The majority (92%) of binaries from the sample are thin disk stars, 7.6% have thick disk kinematics and only two binaries have halo kinematics. Among them, the long-period variable Mira Ceti has a very discordant Hipparcos and ground-based parallax values. From the whole sample, 60 stars are ascribed to the thick disk and halo population. There is an urgent need to increase the number of the identified halo binaries with known orbits and substantially improve the situation with radial velocity data for stars with known orbits. Based on the data from the Hipparcos astrometry satellite (ESA)
We present 11 years of HIRES precision radial velocities (RVs) of the nearby M3V star Gliese 581, combining our data set of 122 precision RVs with an existing published 4.3-year set of 119 HARPS precision RVs (Mayor et al., 2009, Cat. J/A+A/507/487). The velocity set now indicates six companions in Keplerian motion around this star. Differential photometry indicates a likely stellar rotation period of ~94 days and reveals no significant periodic variability at any of the Keplerian periods, supporting planetary orbital motion as the cause of all the RV variations. The estimated equilibrium temperature of the sixth planet, GJ 581g, is 228K, placing it squarely in the middle of the habitable zone of the star and offering a very compelling case for a potentially habitable planet around a very nearby star. This detection, coupled with statistics of the incompleteness of present-day precision RV surveys for volume-limited samples of stars in the immediate solar neighborhood, suggests that {eta}_{oplus}_, the fraction of stars with potentially habitable planets, could well be on the order of a few tens of percent.
HIRES radial velocities of HD9446, HD43691 & HD179079
Short Name:
J/AJ/159/197
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Transit Ephemeris Refinement and Monitoring Survey is a project that aims to detect transits of intermediate-long period planets by refining orbital parameters of the known radial velocity planets using additional data from ground-based telescopes, calculating a revised transit ephemeris for the planet, then monitoring the planet host star during the predicted transit window. Here we present the results from three systems that had high probabilities of transiting planets: HD9446b and c, HD43691b, and HD179079b. We provide new radial velocity (RV) measurements that are then used to improve the orbital solution for the known planets. We search the RV data for indications of additional planets in orbit and find that HD9446 shows a strong linear trend of 4.8{sigma}. Using the newly refined planet orbital solutions, which include a new best-fit solution for the orbital period of HD9446c, and an improved transit ephemerides, we found no evidence of transiting planets in the photometry for each system. Transits of HD9446b can be ruled out completely and transits HD9446c and HD43691b can be ruled out for impact parameters up to b=0.5778 and b=0.898, respectively, due to gaps in the photometry. A transit of HD179079b cannot be ruled out, however, due to the relatively small size of this planet compared to the large star and thus low signal to noise. We determine properties of the three host stars through spectroscopic analysis and find through photometric analysis that HD9446 exhibits periodic variability.
We present the discovery of Kepler-129d (P_d_=7.2_-0.3_^+0.4^yr, m_sini_d__=8.3_-0.7_^+1.1^M_Jup_, e_d_=0.15_-0.05_^+0.07^) based on six years of radial-velocity observations from Keck/HIRES. Kepler-129 also hosts two transiting sub-Neptunes: Kepler-129b (P_b_= 15.79days, r_b_=2.40{+/-}0.04R{Earth}) and Kepler-129c (P_c_=82.20days, r_c_=2.52{+/-}0.07R{Earth}) for which we measure masses of m_b_<20M{Earth} and m_c_=43_-12_^+13^M{Earth}. Kepler-129 is a hierarchical system consisting of two tightly packed inner planets and a massive external companion. In such a system, two inner planets precess around the orbital normal of the outer companion, causing their inclinations to oscillate with time. Based on an asteroseismic analysis of Kepler data, we find tentative evidence that Kepler-129b and c are misaligned with stellar spin axis by >~38{deg}, which could be torqued by Kepler-129 d if it is inclined by >~19{deg} relative to inner planets. Using N-body simulations, we provide additional constraints on the mutual inclination between Kepler-129d and inner planets by estimating the fraction of time during which two inner planets both transit. The probability that two planets both transit decreases as their misalignment with Kepler-129d increases. We also find a more massive Kepler-129c enables the two inner planets to become strongly coupled and more resistant to perturbations from Kepler-129d. The unusually high mass of Kepler-129c provides a valuable benchmark for both planetary dynamics and interior structure, since the best-fit mass is consistent with this 2.5R{Earth} planet having a rocky surface.
In this paper we search for distant massive companions to known transiting gas giant planets that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 planets obtained using the Keck HIRES instrument, and find statistically significant accelerations in fifteen systems. Six of these systems have no previously reported accelerations in the published literature: HAT-P-10, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 adaptive optics (AO) imaging data to place constraints on the allowed masses and orbital periods of the companions responsible for the detected accelerations. The estimated masses of the companions range between 1-500 M_Jup_, with orbital semi-major axes typically between 1-75 AU. A significant majority of the companions detected by our survey are constrained to have minimum masses comparable to or larger than those of the transiting planets in these systems, making them candidates for influencing the orbital evolution of the inner gas giant. We estimate a total occurrence rate of 51%+/-10% for companions with masses between 1-13 M_Jup_ and orbital semi-major axes between 1-20 AU in our sample. We find no statistically significant difference between the frequency of companions to transiting planets with misaligned or eccentric orbits and those with well-aligned, circular orbits. We combine our expanded sample of radial velocity measurements with constraints from transit and secondary eclipse observations to provide improved measurements of the physical and orbital characteristics of all of the planets included in our survey.
Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e=0.28+/-0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65's exterior giant planet did not disrupt its inner system.
We present results of a method for an automatic search for HI shells in 3D data cubes and apply it to the Leiden-Dwingeloo HI survey of the northern Milky Way. In the 2nd Galactic quadrant, where identifications of structures are not substantially influenced by overlapping, we find nearly 300 structures.
