The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6 11.7 s earlier than had been predicted, based on data ...stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with a constant period, ruling out an 81.6 s offset at the 6.4 level. The 1.3 day orbital period of WASP-4b appears to be decreasing at a rate of ms per year. The apparent period change might be caused by tidal orbital decay or apsidal precession, although both interpretations have shortcomings. The gravitational influence of a third body is another possibility, though at present there is minimal evidence for such a body. Further observations are needed to confirm and understand the timing variation.
The Transiting Exoplanet Survey Satellite (TESS) is providing precise time-series photometry for most star clusters in the solar neighborhood. Using the TESS images, we have begun a Cluster ...Difference Imaging Photometric Survey, in which we are focusing both on stars that are candidate cluster members and on stars that show indications of youth. Our aims are to discover giant transiting planets with known ages, and to provide light curves suitable for studies in stellar astrophysics. For this work, we made 159,343 light curves of candidate young stars, across 596 distinct clusters. Each light curve represents between 20 and 25 days of observations of a star brighter than GRp = 16, with 30-minute sampling. We describe the image-subtraction and time-series analysis techniques we used to create the light curves, which have noise properties that agree with theoretical expectations. We also comment on the possible utility of the light-curve sample for studies of stellar rotation evolution and binary eccentricity damping. The light curves, which cover about one-sixth of the galactic plane, are available at archive.stsci.edu/hlsp/cdips.
Abstract
We report the discovery of HATS-70b, a transiting brown dwarf at the deuterium burning limit. HATS-70b has a mass of
and a radius of
, residing in a close-in orbit with a period of
days. The ...host star is a
A star rotating at
, enabling us to characterize the spectroscopic transit of the brown dwarf via Doppler tomography. We find that HATS-70b, like other massive planets and brown dwarfs previously sampled, orbits in a low projected-obliquity orbit with
. The low obliquities of these systems is surprising given all brown dwarf and massive planets with obliquities measured orbit stars hotter than the Kraft break. This trend is tentatively inconsistent with dynamically chaotic migration for systems with massive companions, though the stronger tidal influence of these companions makes it difficult to draw conclusions on the primordial obliquity distribution of this population. We also introduce a modeling scheme for planets around rapidly rotating stars, accounting for the influence of gravity darkening on the derived stellar and planetary parameters.
Context.
The Multi-site All-Sky CAmeRA (MASCARA) and bRing are both photometric ground-based instruments with multiple stations that rely on interline charge-coupled devices with wide-field lenses to ...monitor bright stars in the local sky for variability. MASCARA has already discovered several planets in the northern sky, which are among the brightest known transiting hot Jupiter systems.
Aims.
In this paper, we aim to characterize a transiting planetary candidate in the southern skies found in the combined MASCARA and bRing data sets of HD 85628, an A7V star of
V
= 8.2 mag at a distance 172 pc, to establish its planetary nature.
Methods.
The candidate was originally detected in data obtained jointly with the MASCARA and bRing instruments using a Box Least-Square search for transit events. Further photometry was taken by the 0.7 m Chilean-Hungarian Automated Telescope (CHAT), and radial velocity measurements with the Fiber Dual Echelle Optical Spectrograph on the European Southern Observatory 1.0 m Telescope. High-resolution spectra during a transit were taken with the CTIO high-resolution spectrometer (CHIRON) on the Small and Moderate Aperture Research Telescope System 1.5 m telescope to target the Doppler shadow of the candidate.
Results.
We confirm the existence of a hot Jupiter transiting the bright A7V star HD 85628, which we co-designate as MASCARA-4b and bRing-1b. It is in an orbit of 2.824 days, with an estimated planet radius of 1.53
−0.04
+0.07
R
Jup
and an estimated planet mass of 3.1 ± 0.9
M
Jup
, putting it well within the planetary regime. The CHAT observations show a partial transit, reducing the probability that the transit was around a faint background star. The CHIRON observations show a clear Doppler shadow, implying that the transiting object is in a retrograde orbit with |
λ
| =244.9
−3.6
+2.7
°. The planet orbits at a distance of 0.047 ± 0.004 AU from the star and has a zero-albedo equilibrium temperature of 2100 ± 100 K. In addition, we find that HD 85628 has a previously unreported stellar companion star in the
Gaia
DR2 data demonstrating common proper motion and parallax at 4.3′′ separation (projected separation ~740 AU), and with absolute magnitude consistent with being a K/M dwarf.
Conclusions.
MASCARA-4 b/bRing-1 b is the brightest transiting hot Jupiter known to date in a retrograde orbit. It further confirms that planets in near-polar and retrograde orbits are more common around early-type stars. Due to its high apparent brightness and short orbital period, the system is particularly well suited for further atmospheric characterization.
We report the discovery by the HATSouth network of HATS-18b: a (ProQuest: Formulae and/or non-USASCII text omitted) planet in a 0.8378 day orbit, around a solar analog star (mass 1.037 + or - 0.047 ...Mmiddot in circle and radius (ProQuest: Formulae and/or non-USASCII text omitted) Rmiddot in circle) V= 14.067 + or - 0.040 mag. The high planet mass, combined with its short orbital period, implies strong tidal coupling between the planetary orbit and the star. In fact, given its inferred age, HATS-18 shows evidence of significant tidal spin up, which together with WASP-19 (a very similar system) allows us to constrain the tidal quality factor for Sun-like stars to be in the range of 6.5 <, ~ log sub(10)(Q*/k sub(2)) <, ~ 7 even after allowing for extremely pessimistic model uncertainties. In addition, the HATS-18 system is among the best systems (and often the best system) for testing a multitude of star-planet interactions, be they gravitational, magnetic, or radiative, as well as planet formation and migration theories.
Abstract
We report the discovery of 10 transiting extrasolar planets by the HATSouth survey. The planets range in mass from the super-Neptune HATS-62b, with
, to the super-Jupiter HATS-66b, with
, ...and in size from the Saturn HATS-69b, with
, to the inflated Jupiter HATS-67b, with
. The planets have orbital periods between
days (HATS-67b) and
days (HATS-61b). The hosts are dwarf stars with masses ranging from
(HATS-69) to
(HATS-64) and have apparent magnitudes between
mag (HATS-68) and
mag (HATS-66). The super-Neptune HATS-62b is the least massive planet discovered to date with a radius larger than Jupiter. Based largely on the
Gaia
DR2 distances and broadband photometry, we identify three systems (HATS-62, HATS-64, and HATS-65) as having possible unresolved binary star companions. We discuss in detail our methods for incorporating the
Gaia
DR2 observations into our modeling of the system parameters and into our blend analysis procedures.
We report six new inflated hot Jupiters (HATS-25b through HATS-30b) discovered using the HATSouth global network of automated telescopes. The planets orbit stars with V magnitudes in the range of ...~12-14 and have masses in the largely populated 0.5MJ-0.7M sub(J) region of parameter space but span a wide variety of radii, from 1.17R sub(J) to 1.75R sub(J). HATS-25b, HATS-28b, HATS-29b, and HATS-30b are typical inflated hot Jupiters (Rp= 1.17-1.26R sub(J)) orbiting G-type stars in short period (P= 3.2-4.6 days) orbits. However, HATS-26b (Rp= 1.75R sub(J), P= 3.3024 days) and HATS-27b (Rp= 1.50R sub(J), P= 4.6370 days) stand out as highly inflated planets orbiting slightly evolved F stars just after and in the turn-off points, respectively, which are among the least dense hot Jupiters, with densities of 0.153 g cm super(-3) and 0.180 g cm super(-3), respectively. All the presented exoplanets but HATS-27b are good targets for future atmospheric characterization studies, while HATS-27b is a prime target for Rossiter-McLaughlin monitoring in order to determine its spin-orbit alignment given the brightness (V= 12.8) and stellar rotational velocity (v sin iapproximate 9.3 km s super(-1)) of the host star. These discoveries significantly increase the number of inflated hot Jupiters known, contributing to our understanding of the mechanism(s) responsible for hot Jupiter inflation.
We observed the open clusters M35 and NGC 2158 during the initial K2 campaign (C0). Reducing these data to high-precision photometric timeseries is challenging due to the wide point-spread function ...(PSF) and the blending of stellar light in such dense regions. We developed an image-subtraction-based K2 reduction pipeline that is applicable to both crowded and sparse stellar fields. We applied our pipeline to the data-rich C0 K2 super stamp, containing the two open clusters, as well as to the neighboring postage stamps. In this paper, we present our image subtraction reduction pipeline and demonstrate that this technique achieves ultra-high photometric precision for sources in the C0 super stamp. We extract the raw light curves of 3960 stars taken from the UCAC4 and EPIC catalogs and de-trend them for systematic effects. We compare our photometric results with the prior reductions published in the literature. For de-trended TFA-corrected sources in the 12-12.25 K p magnitude range, we achieve a best 6.5-hour window running rms of 35 ppm, falling to 100 ppm for fainter stars in the 14-14.25 K p magnitude range. For stars with K p > 14 , our de-trended and 6.5-hour binned light curves achieve the highest photometric precision. Moreover, all our TFA-corrected sources have higher precision on all timescales investigated. This work represents the first published image subtraction analysis of a K2 super stamp. This method will be particularly useful for analyzing the Galactic bulge observations carried out during K2 campaign 9. The raw light curves and the final results of our de-trending processes are publicly available at http://k2.hatsurveys.org/archive/.
ABSTRACT
We present the discovery of the transiting exoplanets HAT-P-65b and HAT-P-66b, with orbital periods of
and
days, masses of
and
, and inflated radii of
and
, respectively. They orbit ...moderately bright (
and
) stars of mass
and
. The stars are at the main-sequence turnoff. While it is well known that the radii of close-in giant planets are correlated with their equilibrium temperatures, whether or not the radii of planets increase in time as their hosts evolve and become more luminous is an open question. Looking at the broader sample of well-characterized close-in transiting giant planets, we find that there is a statistically significant correlation between planetary radii and the fractional ages of their host stars, with a false-alarm probability of only 0.0041%. We find that the correlation between the radii of planets and the fractional ages of their hosts is fully explained by the known correlation between planetary radii and their present-day equilibrium temperatures; however, if the zero-age main-sequence equilibrium temperature is used in place of the present-day equilibrium temperature, then a correlation with age must also be included to explain the planetary radii. This suggests that, after contracting during the pre-main-sequence, close-in giant planets are reinflated over time due to the increasing level of irradiation received from their host stars. Prior theoretical work indicates that such a dynamic response to irradiation requires a significant fraction of the incident energy to be deposited deep within the planetary interiors.
We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120 + or - 0.012 MsubJ, a radius of 0.563 + 0.046 - 0.034 RsubJ, and an orbital period of ...3.1853 days. The host star is a moderately bright K dwarf star with a mass of 0.849 + or - 0.027 MsubS, a radius of 0.815 + 0.049 - 0.035 RsubS, and a metallicity of Fe/H= +0.250 + or - 0.080. HATS-7b, which, together with the recently discovered HATS-8b, is one of the first two transiting Neptunes discovered in the Southern sky, is a prime target for additional follow-up observations with southern hemisphere facilities to characterize the atmospheres of super-Neptunes.
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