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Radial-velocity (RV) surveys have discovered hundreds of exoplanetary systems but suffer from a fundamental degeneracy between planet mass M p and orbital inclination i. In this paper, we resolve this degeneracy by combining RVs with complementary absolute astrometry taken from the Gaia EDR3 version of the cross calibrated Hipparcos–Gaia Catalog of Accelerations (HGCA). We use the Markov Chain Monte Carlo orbit code orvara to simultaneously fit literature RVs and absolute astrometry from the HGCA. We constrain the orbits, masses, and inclinations of nine single and massive RV companions orbiting nearby G and K stars. We confirm the planetary nature of six companions: HD 29021 b ( 4.47 − 0.65 + 0.67 M Jup ), HD 81040 b ( 7.24 − 0.37 + 1.0 M Jup ), HD 87883 b ( 6.31 − 0.32 + 0.31 M Jup ), HD 98649 b ( 9.7 − 1.9 + 2.3 M Jup ), HD 106252 b ( 10.00 − 0.73 + 0.78 M Jup ), and HD 171238 b ( 8.8 − 1.3 + 3.6 M Jup ). We place one companion, HD 196067 b ( 12.5 − 1.8 + 2.5 M Jup ) on the planet–brown dwarf boundary and two companions in the low-mass brown dwarf regime: HD 106515 Ab ( 18.9 − 1.4 + 1.5 M Jup ), and HD 221420 b ( 20.6 − 1.6 + 2.0 M Jup ). The brown dwarf HD 221420 b, with a semimajor axis of 9.99 − 0.70 + 0.74 au, a period of 27.7 − 2.5 + 3.0 yr, and an eccentricity of 0.162 − 0.030 + 0.035 represents a promising target for high-contrast imaging. The RV orbits of HD 87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet because of insufficient RV data. We find two possible inclinations for each of these orbits due to difficulty in separating prograde from retrograde orbits, but we expect this will change decisively with future Gaia data releases.
Radial-velocity (RV) surveys have discovered hundreds of exoplanetary systems but suffer from a fundamental degeneracy between planet mass M p and orbital inclination i. In this paper, we resolve this degeneracy by combining RVs with complementary absolute astrometry taken from the Gaia EDR3 version of the cross calibrated Hipparcos–Gaia Catalog of Accelerations (HGCA). We use the Markov Chain Monte Carlo orbit code orvara to simultaneously fit literature RVs and absolute astrometry from the HGCA. We constrain the orbits, masses, and inclinations of nine single and massive RV companions orbiting nearby G and K stars. We confirm the planetary nature of six companions: HD 29021 b ( 4.47 − 0.65 + 0.67 M Jup ), HD 81040 b ( 7.24 − 0.37 + 1.0 M Jup ), HD 87883 b ( 6.31 − 0.32 + 0.31 M Jup ), HD 98649 b ( 9.7 − 1.9 + 2.3 M Jup ), HD 106252 b ( 10.00 − 0.73 + 0.78 M Jup ), and HD 171238 b ( 8.8 − 1.3 + 3.6 M Jup ). We place one companion, HD 196067 b ( 12.5 − 1.8 + 2.5 M Jup ) on the planet–brown dwarf boundary and two companions in the low-mass brown dwarf regime: HD 106515 Ab ( 18.9 − 1.4 + 1.5 M Jup ), and HD 221420 b ( 20.6 − 1.6 + 2.0 M Jup ). The brown dwarf HD 221420 b, with a semimajor axis of 9.99 − 0.70 + 0.74 au, a period of 27.7 − 2.5 + 3.0 yr, and an eccentricity of 0.162 − 0.030 + 0.035 represents a promising target for high-contrast imaging. The RV orbits of HD 87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet because of insufficient RV data. We find two possible inclinations for each of these orbits due to difficulty in separating prograde from retrograde orbits, but we expect this will change decisively with future Gaia data releases.
Acoustic glitches are regions inside a star where the sound speed or its derivatives change abruptly. These leave a small characteristic oscillatory signature in the stellar oscillation frequencies. With the precision achieved by Kepler seismic data, it is now possible to extract these small amplitude oscillatory signatures, and infer the locations of the glitches. We perform glitch analysis for all the 66 stars in the Kepler seismic LEGACY sample to derive the locations of the base of the envelope convection zone and the helium ionization zone. The signature from helium ionization zone is found to be robust for all stars in the sample, whereas the convection zone signature is found to be weak and problematic, particularly for relatively massive stars with large errorbars on the oscillation frequencies.We demonstrate that the helium glitch signature can be used to constrain the properties of the helium ionization layers and the helium abundance.
The advent of space-based observatories such as CoRoT and Kepler has enabled the testing of our understanding of stellar evolution on thousands of stars. Evolutionary models typically require five input parameters, the mass, initial Helium abundance, initial metallicity, mixinglength (assumed to be constant over time), and the age to which the star must be evolved. Some of these parameters are also very useful in characterizing the associated planets and in studying galactic archaeology. How to obtain these parameters from observations rapidly and accurately, specifically in the context of surveys of thousands of stars, is an outstanding question, one that has eluded straightforward resolution. For a given star, we typically measure the effective temperature and surface metallicity spectroscopically and low-degree oscillation frequencies through space observatories. Here we demonstrate that statistical learning, using artificial neural networks, is successful in determining the evolutionary parameters based on spectroscopic and seismic measurements. Our trained networks show robustness over a broad range of parameter space, and critically, are entirely computationally inexpensive and fully automated. We analyze the observations of a few stars using this method and the results compare well to inferences obtained using other techniques. This method is both computationally cheap and inferentially accurate, paving the way for analyzing the vast quantities of stellar observations from past, current, and future missions.
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