- ID:
- ivo://CDS.VizieR/J/AJ/162/265
- Title:
- TESS-Keck survey. VI. HIP-97166 radial velocity
- Short Name:
- J/AJ/162/265
- Date:
- 16 Mar 2022 06:42:57
- Publisher:
- CDS
- Description:
- We report the discovery of HIP-97166b (TOI-1255b), a transiting sub-Neptune on a 10.3day orbit around a K0 dwarf 68pc from Earth. This planet was identified in a systematic search of TESS Objects of Interest for planets with eccentric orbits, based on a mismatch between the observed transit duration and the expected duration for a circular orbit. We confirmed the planetary nature of HIP-97166b with ground-based radial-velocity measurements and measured a mass of M_b_=20{+/-}2M{Earth} along with a radius of R_b_=2.7{+/-}0.1R{Earth} from photometry. We detected an additional nontransiting planetary companion with M_c_sini=10{+/-}2M{Earth} on a 16.8day orbit. While the short transit duration of the inner planet initially suggested a high eccentricity, a joint RV-photometry analysis revealed a high impact parameter b=0.84{+/-}0.03 and a moderate eccentricity. Modeling the dynamics with the condition that the system remain stable over >10^5^ orbits yielded eccentricity constraints e_b_=0.16{+/-}0.03 and e_c_<0.25. The eccentricity we find for planet b is above average for the small population of sub-Neptunes with well-measured eccentricities. We explored the plausible formation pathways of this system, proposing an early instability and merger event to explain the high density of the inner planet at 5.3{+/-}0.9g/cc as well as its moderate eccentricity and proximity to a 5:3 mean-motion resonance.
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- ID:
- ivo://CDS.VizieR/J/AJ/162/215
- Title:
- TESS-Keck survey.V. Radial velocities of HD63935
- Short Name:
- J/AJ/162/215
- Date:
- 14 Mar 2022 08:19:39
- Publisher:
- CDS
- Description:
- We present the discovery of two nearly identically sized sub-Neptune transiting planets orbiting HD63935, a bright (V=8.6mag), Sun-like (Teff=5560K) star at 49pc. TESS identified the first planet, HD63935b (TOI-509.01), in Sectors 7 and 34. We identified the second signal (HD63935c) in Keck High Resolution Echelle Spectrometer and Lick Automated Planet Finder radial velocity data as part of our follow-up campaign. It was subsequently confirmed with TESS photometry in Sector 34 as TOI-509.02. Our analysis of the photometric and radial velocity data yielded a robust detection of both planets with periods of 9.0600{+/-}0.007 and 21.40{+/-}0.0019days, radii of 2.99{+/-}0.14 and 2.90{+/-}0.13R{Earth}, and masses of 10.8{+/-}1.8 and 11.1{+/-}2.4M{Earth}. We calculated densities for planets b and c consistent with a few percent of the planet mass in hydrogen/helium envelopes. We also describe our survey's efforts to choose the best targets for James Webb Space Telescope atmospheric follow-up. These efforts suggest that HD 63935 b has the most clearly visible atmosphere of its class. It is the best target for transmission spectroscopy (ranked by the transmission spectroscopy metric, a proxy for atmospheric observability) in the so far uncharacterized parameter space comprising sub-Neptune-sized (2.6R{Earth}<Rp<4R{Earth}), moderately irradiated (100F{Earth}<Fp<1000F{Earth}) planets around G stars. Planet c is also a viable target for transmission spectroscopy, and given the indistinguishable masses and radii of the two planets, the system serves as a natural laboratory for examining the processes that shape the evolution of sub-Neptune planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/136
- Title:
- TESS light curve of AGN NGC 4395
- Short Name:
- J/ApJ/899/136
- Date:
- 03 Dec 2021 13:06:51
- Publisher:
- CDS
- Description:
- We present optical light curves from the Transiting Exoplanet Survey Satellite (TESS) for the archetypical dwarf active galactic nucleus (AGN) in the nearby galaxy NGC 4395 hosting a ~105M{sun} supermassive black hole (SMBH). Significant variability is detected on timescales from weeks to hours before reaching the background noise level. The ~month-long, 30 minute-cadence, high-precision TESS light curve can be well fit by a simple damped random walk (DRW) model, with the damping timescale {tau}DRW constrained to be 2.3_-0.7_^+1.8^days (1{sigma}). NGC 4395 lies almost exactly on the extrapolation of the {tau }_DRW_-M_BH_ relation measured for AGNs with BH masses that are more than three orders of magnitude larger. The optical variability periodogram can be well fit by a broken power law with the high-frequency slope (-1.88{+/-}0.15) and the characteristic timescale ({tau}_br_=1/(2{pi}f_br_)=1.4_-0.5_^+1.9^days) consistent with the DRW model within 1{sigma}. This work demonstrates the power of TESS light curves in identifying low-mass accreting SMBHs with optical variability, and a potential global {tau}_DRW}_-M_BH_ relation that can be used to estimate SMBH masses with optical variability measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/625/L13
- Title:
- TESS light curve of beta Pictoris
- Short Name:
- J/A+A/625/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for signs of falling evaporating bodies (FEBs, also known as exocomets) in photometric time series obtained for {beta} Pictoris after fitting and removing its {delta} Scuti-type pulsation frequencies. Using photometric data obtained by the TESS satellite we determined the pulsational properties of the exoplanet host star {beta} Pictoris through frequency analysis. We then pre-whitened the 54 identified {delta} Scuti p-modes and investigated the residual photometric time series for the presence of FEBs. We identify three distinct dipping events in the light curve of {beta} Pictoris over a 105-day period. These dips have depths from 0.5 to 2-millimagnitudes and durations of up to 2-days for the largest dip. These dips are asymmetric in nature and are consistent with a model of an evaporating comet with an extended tail crossing the disc of the star. We present the first broadband detections of exocomets crossing the disc of {beta} Pictoris, complementing the predictions made 20 years earlier by Lecavelier Des Etangs et al. (1999A&A...343..916L). No periodic transits are seen in this time series. These observations confirm the spectroscopic detection of exocomets in calcium H and K lines that have been seen in high resolution spectroscopy.
- ID:
- ivo://CDS.VizieR/J/AJ/158/45
- Title:
- TESS light curve & radial velocities for HD 1397
- Short Name:
- J/AJ/158/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a transiting planet first identified as a candidate in Sector 1 of the Transiting Exoplanet Survey Satellite (TESS), and then confirmed with precision radial velocities. HD 1397b has a mass of M_P_=0.367_-0.023_^+0.022^ M_J_, a radius of R_P_=1.023_-0.013_^+0.013^ R_J_, and orbits its bright host star (V=7.8 mag) with an orbital period of 11.5366+/-0.0003 d on a moderately eccentric orbit (e=0.216_-0.026_^+0.027^). With a mass of M_*_=1.257_-0.029_^+0.029^ M_{sun}_, a radius of R_*_=2.341_-0.019_^+0.022^ R_{sun}_, and an age of 4.46+/-0.25 Gyr, the solar-metallicity host star has already departed from the main sequence. We find evidence in the radial velocity measurements of a secondary signal with a longer period. We attribute it to the rotational modulation of stellar activity, but a long-term radial velocity monitoring would be necessary to discard if this signal is produced by a second planet in the system. The HD 1397 system is among the brightest ones currently known to host a transiting planet, which will make it possible to perform detailed follow-up observations in order to characterize the properties of giant planets orbiting evolved stars.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A114
- Title:
- TESS light curves detection limits
- Short Name:
- J/A+A/630/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The primary targets of the NASA Transiting Exoplanet Survey Satellite will be K and M dwarf stars within our solar neighbourhood. Young K and M dwarf stars are known to exhibit a high starspot coverage (~50%), however, older stars are known to show fewer starspots. This implies that TESS 2 min cadence transit light curves may contain starspot anomalies, and if so, will require transit-starspot models to accurately determine the properties of the system. The goals are to determine if starspot anomalies can manifest in TESS transit light curves, to determine the detection limits of the starspot anomalies and to examine the relationship between the change in flux caused by the starspot anomaly and the planetary transit. 20573 simulations of planetary transits around spotted stars were conducted using the transit-starspot model, PRISM. In total 3888 different scenarios were considered using three different host star spectral types, M4V, M1V and K5V. The mean amplitude of the starspot anomaly was measured and compared to the photometric precision of the light curve, to determine if the starspot anomaly's characteristic "blip" was noticeable in the light curve. Results. The simulations show that, starspot anomalies will be observable in TESS 2 min cadence data. The smallest starspot detectable in TESS transit light curves has a radius of ~1900km. The starspot detection limits for the three host stars are: 4900+/-1700km (M4V), 13800+/-6000km (M1V) and 15900+/-6800km (K5V). The smallest change in flux of the starspot ({Delta}F_spot_=0.00015+/-0.00001) can be detected when the ratio between the planetary and stellar radii, k=0.082+/-0.004. The results confirm known dependencies between the amplitude of the starspot anomaly and the photometric parameters of the light curve. The results allowed the characterisation of the relationship between the change in flux of the starspot anomaly and the change in flux of the planetary transit for TESS transit light curves.
- ID:
- ivo://CDS.VizieR/J/AJ/157/113
- Title:
- TESS M-dwarf exoplanetary systems
- Short Name:
- J/AJ/157/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the M-dwarf exoplanetary systems forthcoming from NASA's TESS mission. While the mission's footprint is too complex to be characterized by a single detection completeness, we extract ensemble completeness functions that recover the planet detections from previous work for stars between 3200 and 4000 K. We employ these completeness functions, together with a dual- population planet occurrence model that includes compact multiple planetary systems, to infer anew the planet yield. We predict both the number of M-dwarf planets likely from TESS and their system architectures. We report four main findings. First, TESS will likely detect more planets orbiting M dwarfs that previously predicted. Around stars with effective temperatures between 3200 and 4000 K, we predict that TESS will find 1274+/-241 planets orbiting 1026+/-182 stars, a 1.2-fold increase over previous predictions. Second, TESS will find two or more transiting planets around 20% of these host stars, a number similar to the multiplicity yield of NASA's Kepler mission. Third, TESS light curves in which one or more planets are detected will often contain transits of additional planets below the detection threshold of TESS. Among a typical set of 200 TESS hosts to one or more detected planets, 93+/-17 transiting planets will be missed. Transit follow-up efforts with the photometric sensitivity to detect an Earth or larger around a mid-M dwarf, even with very modest period completeness, will readily result in additional planet discoveries. Fourth, the strong preference of TESS for systems of compact multiples indicates that TESS planets will be dynamically cooler on average than Kepler planets, with 90% of TESS planets residing in orbits with e<0.15. We include both (1) a predicted sample of planets detected by TESS orbiting stars between 3200 and 4000 K, including additional nontransiting planets, or transiting and undetected planets orbiting the same star and (2) sample completeness functions for use by the community.
- ID:
- ivo://CDS.VizieR/J/A+A/652/A120
- Title:
- TESS OBA-type eclipsing binaries
- Short Name:
- J/A+A/652/A120
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Intermediate- to high-mass stars are the least numerous types of stars and they are less well understood than their more numerous low-mass counterparts in terms of their internal physical processes. Modelling the photometric variability of a large sample of main-sequence intermediate- to high-mass stars in eclipsing binary systems will help to improve the models for such stars. Our goal is to compose a homogeneously compiled sample of main-sequence intermediate- to high-mass OBA-type dwarfs in eclipsing binary systems from TESS photometry. We search for binaries with and without pulsations and determine their approximate ephemerides. Our selection starts from a catalogue of dwarfs with colours corresponding to those of OBA-type dwarfs in the TESS Input Catalog. We develop a new automated method aimed at detecting eclipsing binaries in the presence of strong pulsational and/or rotational signal relative to the eclipse depths and apply it to publicly available 30-min cadence TESS light curves. Using targets with TESS magnitudes below 15 and cuts in the 2MASS magnitude bands of J-H<0.045 and J-K<0.06 as most stringent criteria, we arrive at a total of 189 981 intermediate- to high-mass candidates, 91193 of which have light curves from at least one of two data reduction pipelines. The eclipsing binary detection and subsequent manual check for false positives resulted in 3155 unique OBA-type eclipsing binary candidates. Our sample of eclipsing binary stars in the intermediate- to high-mass regime allows for future binary (and asteroseismic) modelling with the aim to better understand the internal physical processes in this hot part of the main sequence.
- ID:
- ivo://CDS.VizieR/J/ApJS/253/11
- Title:
- TESS observations of Cepheid stars
- Short Name:
- J/ApJS/253/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first analysis of Cepheid stars observed by the TESS space mission in Sectors 1-5. Our sample consists of 25 pulsators: ten fundamental mode, three overtone and two double-mode classical Cepheids, plus three type II and seven anomalous Cepheids. The targets were chosen from fields with different stellar densities, both from the Galactic field and from the Magellanic System. Three targets have 2 minutes cadence light curves available by the TESS Science Processing Operations Center: for the rest, we prepared custom light curves from the full-frame images with our own differential photometric FITSH pipeline. Our main goal was to explore the potential and the limitations of TESS concerning the various subtypes of Cepheids. We detected many low-amplitude features: weak modulation, period jitter, and timing variations due to light-time effect. We also report signs of nonradial modes and the first discovery of such a mode in an anomalous Cepheid, the overtone star XZ Cet, which we then confirmed with ground-based multicolor photometric measurements. We prepared a custom photometric solution to minimize saturation effects in the bright fundamental-mode classical Cepheid, {beta} Dor with the lightkurve software, and we revealed strong evidence of cycle-to-cycle variations in the star. In several cases, however, fluctuations in the pulsation could not be distinguished from instrumental effects, such as contamination from nearby sources, which also varies between sectors.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/L9
- Title:
- TESS obs. of massive O and B stars
- Short Name:
- J/ApJ/872/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Uncertainties in stellar structure and evolution theory are largest for stars undergoing core convection on the main sequence. A powerful way to calibrate the free parameters used in the theory of stellar interiors is asteroseismology, which provides direct measurements of angular momentum and element transport. We report the detection and classification of new variable O and B stars using high-precision short-cadence (2 minutes) photometric observations assembled by the Transiting Exoplanet Survey Satellite (TESS). In our sample of 154 O and B stars, we detect a high percentage (90%) of variability. Among these we find 23 multiperiodic pulsators, 6 eclipsing binaries, 21 rotational variables, and 25 stars with stochastic low-frequency variability. Several additional variables overlap between these categories. Our study of O and B stars not only demonstrates the high data quality achieved by TESS for optimal studies of the variability of the most massive stars in the universe, but also represents the first step toward the selection and composition of a large sample of O and B pulsators with high potential for joint asteroseismic and spectroscopic modeling of their interior structure with unprecedented precision.