Search

Pioneering photometric, astrometric, and spectroscopic surveys is helping exoplanetary scientists better constrain the fundamental properties of stars within our galaxy and the planets these stars host. In this study, we use the third data release from the stellar spectroscopic GALAH Survey, coupled with astrometric data of eDR3 from the Gaia satellite, and other data from NASA's Exoplanet Archive, to refine our understanding of 279 confirmed and candidate exoplanet host stars and their exoplanets. This homogenously analysed data set comprises 105 confirmed exoplanets, along with 146 K2 candidates, 95 TESS Objects of Interest (TOIs), and 52 Community TOIs (CTOIs). Our analysis significantly shifts several previously (unknown) planet parameters while decreasing the uncertainties for others. Our radius estimates suggest that 35 planet candidates are more likely brown dwarfs or stellar companions due to their new radius values. We are able to refine the radii and masses of WASP-47 e, K2-106 b, and CoRoT-7 b to their most precise values yet to less than 2.3 per cent and 8.5 per cent, respectively. We also use stellar rotational values from GALAH to show that most planet candidates will have mass measurements that will be tough to obtain with current ground-based spectrographs. With GALAH's chemical abundances, we show through chemo-kinematics that there are five planet hosts that are associated with the galaxy's thick disc, including NGTS-4, K2-183, and K2-337. Finally, we show that there is no statistical difference between the chemical properties of hot Neptune and hot rocky exoplanet hosts, with the possibility that short-period rocky worlds might be the remnant cores of hotter, gaseous worlds. [ABSTRACT FROM AUTHOR]

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalogue of physical and chemical properties for 47 285 stars. Using these data, we have derived isochrone masses and radii that are precise to within 5 per cent. We have revised the parameters of three confirmed, and twelve candidate, TESS planetary systems. These results cast doubt on whether CTOI-20125677 is indeed a planetary system, since the revised planetary radii are now comparable to stellar sizes. Our GALAH– TESS catalogue contains abundances for up to 23 elements. We have specifically analysed the molar ratios for C/O, Mg/Si, Fe/Si, and Fe/Mg, to assist in determining the composition and structure of planets with Rp < 4R⊕. From these ratios, 36 per cent fall within 2 |$\sigma$| sigma of the Sun/Earth values, suggesting that these stars may host rocky exoplanets with geological compositions similar to planets found within our own Solar system. [ABSTRACT FROM AUTHOR]

The Doppler wobble induced by the extra-solar planet HD 134987b was first detected by data from the Keck Telescope nearly a decade ago, and was subsequently confirmed by data from the Anglo-Australian Telescope (AAT). However, as more data have been acquired for this star over the years since, the quality of a single Keplerian fit to that data has been getting steadily worse. The best-fitting single Keplerian to the 138 Keck and AAT observations now in hand has an root-mean-square (rms) scatter of 6.6 m s−1. This is significantly in excess of both the instrumental precision achieved by both the Keck and Anglo-Australian Planet Searches for stars of this magnitude, and of the jitter expected for a star with the properties of HD134987. However, a double Keplerian (i.e. dual planet) fit delivers a significantly reduced rms of 3.3 m s−1. The best-fitting double planet solution has minimum planet masses of 1.59 and 0.82 1.59 ± 0.02 MJup, orbital periods of 258 and 5000 d, and eccentricities of 0.23 and 0.12, respectively. We find evidence that activity-induced jitter is a significant factor in our fits and do not find evidence for asteroseismological p modes. We also present seven years of photometry at a typical precision of 0.003 mag with the T8 0.8 m automatic photometric telescope at Fairborn observatory. These observations do not detect photometric variability and support the inference that the detected radial-velocity periods are due to planetary mass companions rather than due to photospheric spots and plages. [ABSTRACT FROM AUTHOR]

We report Doppler measurements of the stars HD 187085 and HD 20782 which indicate two high eccentricity low-mass companions to the stars. We find HD 187085 has a Jupiter-mass companion with a ∼1000-d orbit. Our formal ‘best-fitting’ solution suggests an eccentricity of 0.47, however, it does not sample the periastron passage of the companion and we find that orbital solutions with eccentricities between 0.1 and 0.8 give only slightly poorer fits (based on rms and ) and are thus plausible. Observations made during periastron passage in 2007 June should allow for the reliable determination of the orbital eccentricity for the companion to HD 187085. Our data set for HD 20782 does sample periastron and so the orbit for its companion can be more reliably determined. We find the companion to HD 20782 has , an orbital period of 595.86 ± 0.03 d and an orbit with an eccentricity of 0.92 ± 0.03. The detection of such high-eccentricity (and relatively low-velocity amplitude) exoplanets appears to be facilitated by the long-term precision of the Anglo-Australian Planet Search. Looking at exoplanet detections as a whole, we find that those with higher eccentricity seem to have relatively higher velocity amplitudes indicating higher mass planets and/or an observational bias against the detection of high-eccentricity systems. [ABSTRACT FROM AUTHOR]

ABSTRACT We report the detection of a new candidate exoplanet around the metal-rich star τ[sup 1] Gruis. With M sin i= 1.26 ± 0.18 M[sub Jup] , a period of 1391 ± 300 d and an orbit with an eccentricity of 0.14 ± 0.14 it adds to the growing population of long-period exoplanets with low-eccentricity orbits. This population now comprises more than 20 per cent of known exoplanets. When the companion to τ[sup 1] Gruis is plotted together with all exoplanets found by radial velocity searches we find evidence for a peak in the number of short-period exoplanets, followed by a minimum of planets between approximately 5 and 50 d and then an apparent rise in the number of planets per unit radius that seems to set in by 100 d, indicating more planets further from the host star. This is very different from the Gaussian-like period distribution found for stellar companions. This lends support to the idea that once a clearing in the inner protoplanetary disc develops, it halts the inward migration of planets. In particular, the smooth distribution of exoplanets arising from planetary migration through a disc is altered by an accumulation of exoplanets at the point where the disc has been cleared out. [ABSTRACT FROM AUTHOR]

Investigates extrasolar planets around several stars. Planetary systems; Metal-rich sun-like stars; Periodic Keplerian velocity variations.

We report the detection of an extra-solar planet candidate orbiting the G1 V star HD 39091. The orbital period is 2049 d and the eccentricity is 0.62. With a minimum (M sin i) mass of 10.3M[sub JUP] this object falls near the high-mass end of the observed planet mass function, and may plausibly be a brown dwarf. Other characteristics of this system, including orbital eccentricity and metallicity, are typical of the well-populated class of radial velocity planets in eccentric orbits around metal-rich stars. [ABSTRACT FROM AUTHOR]