- ID:
- ivo://CDS.VizieR/J/AJ/155/106
- Title:
- New Doppler velocity measurements of GJ 876
- Short Name:
- J/AJ/155/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gliese 876 harbors one of the most dynamically rich and well-studied exoplanetary systems. The nearby M4V dwarf hosts four known planets, the outer three of which are trapped in a Laplace mean-motion resonance. A thorough characterization of the complex resonant perturbations exhibited by the orbiting planets, and the chaotic dynamics therein, is key to a complete picture of the system's formation and evolutionary history. Here we present a reanalysis of the system using 6 yr of new radial velocity (RV) data from four instruments. These new data augment and more than double the size of the decades-long collection of existing velocity measurements. We provide updated estimates of the system parameters by employing a computationally efficient Wisdom-Holman N-body symplectic integrator, coupled with a Gaussian process (GP) regression model to account for correlated stellar noise. Experiments with synthetic RV data show that the dynamical characterization of the system can differ depending on whether a white-noise or correlated-noise model is adopted. Despite there being a region of stability for an additional planet in the resonant chain, we find no evidence for one. Our new parameter estimates place the system even deeper into resonance than previously thought and suggest that the system might be in a low-energy, quasi-regular double apsidal corotation resonance. This result and others will be used in a subsequent study on the primordial migration processes responsible for the formation of the resonant chain.
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- ID:
- ivo://CDS.VizieR/J/AJ/153/137
- Title:
- New NSVS 14256825 eclipse times
- Short Name:
- J/AJ/153/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cyclic behavior of (O-C) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets. We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the (O-C) diagram by three years. Based on the archival and our new data spanning over more than 17 years, we re-examined the up-to-date system (O-C). The data revealed a systematic, quasi-sinusoidal variation deviating from an older linear ephemeris by about 100 s. It also exhibits a maximum in the (O-C) near JD 2456400 that was previously unknown. We consider two most credible explanations of the (O-C) variability: the light propagation time due to the presence of an invisible companion in a distant circumbinary orbit, and magnetic cycles reshaping one of the binary components, known as the Applegate or Lanza-Rodono effect. We found that the latter mechanism is unlikely due to the insufficient energy budget of the M-dwarf secondary. In the framework of the third-body hypothesis, we obtained meaningful constraints on the Keplerian parameters of a putative companion and its mass. Our best-fitting model indicates that the observed quasi-periodic (O-C) variability can be explained by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses rather than a planet, orbiting the binary in a moderately elliptical orbit (e~0.175) with a period of ~10 years. Our analysis rules out the two-planet model proposed earlier.
- ID:
- ivo://CDS.VizieR/J/AJ/161/273
- Title:
- 181 new planet candidates with TESS
- Short Name:
- J/AJ/161/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) mission measured light from stars in ~75% of the sky throughout its 2yr primary mission, resulting in millions of TESS 30-minute-cadence light curves to analyze in the search for transiting exoplanets. To search this vast data trove for transit signals, we aim to provide an approach that both is computationally efficient and produces highly performant predictions. This approach minimizes the required human search effort. We present a convolutional neural network, which we train to identify planetary transit signals and dismiss false positives. To make a prediction for a given light curve, our network requires no prior transit parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in ~5ms on a single GPU, enabling large-scale archival searches. We present 181 new planet candidates identified by our network, which pass subsequent human vetting designed to rule out false positives. Our neural network model is additionally provided as open-source code for public use and extension.
- ID:
- ivo://CDS.VizieR/J/AJ/158/251
- Title:
- New reduction of UVES data for 35 M dwarfs
- Short Name:
- J/AJ/158/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UVES (Ultraviolet and Visible Spectrometer) M Dwarf Planet Search program surveyed 40 M dwarfs and 1 M giant from 2000 through 2007 March. Two of the M dwarfs were double-lined spectroscopic binaries. The 38 single-lined M dwarfs in this survey are among the nearest and brightest M dwarfs. Starting with the reduced 1D spectra provided by the UVES team, we reanalyzed the UVES velocities of Proxima Cen as part of the "Pale Red Dot" program. The velocity rms decreased from 3.6 to 2.3 m/s. Motivated by this result, we have harvested all of the raw data from the UVES M Dwarf Planet Search from the European Southern Observatory (ESO) archives and have written custom packages to generate 1D spectra from the raw data, and velocities from the 1D spectra. The median improvement in the velocity rms from the new analysis is 1.8 m/s. Six of the 38 M dwarfs from the original study had a velocity rms<4 m/s. In the reanalysis presented here, 22 of these stars have a velocity rms<4 m/s. We improve the upper limits on possible planets orbiting these stars by a factor of typically two to three. For many of these M dwarfs, these observations represent the first epoch of high-precision velocity measurements.
- ID:
- ivo://CDS.VizieR/J/AJ/158/38
- Title:
- New substellar discoveries from Kepler and K2
- Short Name:
- J/AJ/158/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discoveries of a brown dwarf (BD) and a low-mass star from the Kepler and K2 missions. The newly discovered BD is EPIC 212036875b and the low-mass star is KOI-607b. EPIC 212036875b has a mass of M_b_=52.3+/-1.9 M_J_, a radius of R_b_=0.874+/-0.017 R_J_, and orbits its host star in P=5.169885+/-0.000027 days. Its host star is a late F-type star with M_*_=1.288+/-0.065 M_{sun}_, R_*_= 1.498+/-0.025 R_{sun}_, and T_eff_=6238+/-60 K. KOI-607b has a mass of M_b_=95.1+/-3.4 M_J_, a radius of R_b_=1.089+/-0.089 R_J_, and an orbital period of P=5.89399148+/-0.00000060 days. The primary star in the KOI-607 system is a G dwarf with M_*_=0.993+/-0.052 M_{sun}_, R_*_= 0.915+/-0.031 R_{sun}_, and T_eff_=5418+/-87 K. We also revisit a BD, CWW 89Ab, that was previously published by Nowak et al. 2017AJ....153..131N (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting BDs associated with a star cluster, which illustrates the need for more BDs with accurate masses, radii, and reliable age determinations to test theoretical models. We find that the newly discovered BD, EPIC 212036875b, falls in the middle of the so-called BD desert, indicating that EPIC 212036875b is either a particularly rare object, or the BD desert may not be so dry after all.
- ID:
- ivo://CDS.VizieR/J/AJ/156/178
- Title:
- NIR transmission spectra of TRAPPIST-1 planets
- Short Name:
- J/AJ/156/178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The seven approximately Earth-sized transiting planets in the TRAPPIST-1 system provide a unique opportunity to explore habitable- and nonhabitable-zone small planets within the same system. Its habitable-zone exoplanets - due to their favorable transit depths - are also worlds for which atmospheric transmission spectroscopy is within reach with the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST). We present here an independent reduction and analysis of two HST Wide Field Camera 3 (WFC3) near-infrared transit spectroscopy data sets for six planets (b through g). Utilizing our physically motivated detector charge-trap correction and a custom cosmic-ray correction routine, we confirm the general shape of the transmission spectra presented by de Wit et al. (2016Natur.537...69D). Our data reduction approach leads to a 25% increase in the usable data and reduces the risk of confusing astrophysical brightness variations (e.g., flares) with instrumental systematics. No prominent absorption features are detected in any individual planet's transmission spectra; by contrast, the combined spectrum of the planets shows a suggestive decrease around 1.4 {mu}m similar to an inverted water absorption feature. Including transit depths from K2, the SPECULOOS-South Observatory, and Spitzer, we find that the complete transmission spectrum is fully consistent with stellar contamination owing to the transit light source effect. These spectra demonstrate how stellar contamination can overwhelm planetary absorption features in low-resolution exoplanet transit spectra obtained by HST and JWST and also highlight the challenges in combining multi-epoch observations for planets around rapidly rotating spotted stars.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/5.775
- Title:
- nu2 Lupi CHEOPS light curves
- Short Name:
- J/other/NatAs/5.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanets transiting bright nearby stars are key objects for advancing our knowledge of planetary formation and evolution. The wealth of photons from the host star gives detailed access to the atmospheric, interior and orbital properties of the planetary companions. nu^2^ Lupi (HD 136352) is a naked-eye (V=5.78) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6 and 107.6d via radial-velocity monitoring. The two inner planets (b and c) were recently found to transit2, prompting a photometric follow-up by the brand new Characterising Exoplanets Satellite (CHEOPS). Here, we report that the outer planet d is also transiting, and measure its radius and mass to be 2.56+/-0.09R_{Earth}_ and 8.82+/-0.94M_{Earth}_, respectively. With its bright Sun-like star, long period and mild irradiation (~5.7 times the irradiation of Earth), nu^2^ Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. We refine the properties of all three planets: planet b probably has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen-helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the nu^2^ Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/23
- Title:
- NUV and FUV measurements of planet host stars
- Short Name:
- J/ApJ/890/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for evidence of the cause of the exoplanet radius gap, i.e., the dearth of planets with radii near 1.8R_{Earth}_. If the cause were photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of the planet-hosting stars. If, alternatively, the cause were core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find that no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of Galaxy Evolution Explorer near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core-powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized <4R_{Earth}_ planets has roughly doubled could confirm or rule out photoevaporation.
- ID:
- ivo://CDS.VizieR/J/AJ/155/177
- Title:
- Obliquities of planetary & eclipsing binary systems
- Short Name:
- J/AJ/155/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity {Psi} of the eclipsed star. Here we present a method for detecting and analyzing these patterns, based on a statistical test for correlations between the anomalies observed in a sequence of eclipses. Compared to previous methods, ours makes fewer assumptions and is easier to automate. We apply it to a sample of 64 stars with transiting planets and 24 eclipsing binaries for which precise space-based data are available, and for which there was either some indication of flux anomalies or a previously reported obliquity measurement. We were able to determine obliquities for 10 stars with hot Jupiters. In particular we found {Psi}~<10{deg} for Kepler-45, which is only the second M dwarf with a measured obliquity. The other eight cases are G and K stars with low obliquities. Among the eclipsing binaries, we were able to determine obliquities in eight cases, all of which are consistent with zero. Our results also reveal some common patterns of stellar activity for magnetically active G and K stars, including persistently active longitudes.
- ID:
- ivo://CDS.VizieR/J/AJ/161/164
- Title:
- Observation of 186 TESS stars with NESSI (WYIN)
- Short Name:
- J/AJ/161/164
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- We present high-resolution speckle interferometric imaging observations of TESS exoplanet host stars using the NN-EXPLORE Exoplanet and Stellar Speckle Imager instrument at the 3.5m WIYN telescope. Eight TESS objects of interest that were originally discovered by Kepler were previously observed using the Differential Speckle Survey Instrument. Speckle observations of 186 TESS stars were carried out, and 45 (24%) likely bound companions were detected. This is approximately the number of companions we would expect to observe given the established 46% binarity rate in exoplanet host stars. For the detected binaries, the distribution of stellar mass ratio is consistent with that of the standard Raghavan distribution and may show a decrease in high-q systems as the binary separation increases. The distribution of binary orbital periods, however, is not consistent with the standard Ragahavan model, and our observations support the premise that exoplanet-hosting stars with binary companions have, in general, wider orbital separations than field binaries. We find that exoplanet-hosting binary star systems show a distribution peaking near 100 au, higher than the 40-50au peak that is observed for field binaries. This fact led to earlier suggestions that planet formation is suppressed in close binaries.
