- ID:
- ivo://CDS.VizieR/J/A+A/624/A38
- Title:
- Radial velocities of K2-36
- Short Name:
- J/A+A/624/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-36 is a K dwarf orbited by two small (R_b_=1.43+/-0.08R_{earth}_ and R_c_=3.2+/-0.3R_{earth}_, close-in (a_b_=0.022AU and a_c_=0.054AU) transiting planets discovered by the Kepler/K2 space observatory. They are representatives of two distinct families of small planets (R_p_<4R_{earth}_) recently emerged from the analysis of Kepler data, with likely a different structure, composition and evolutionary pathways. We revise the fundamental stellar parameters and the sizes of the planets, and provide the first measurement of their masses and bulk densities, which we use to infer their structure and composition. We observed K2-36 with the HARPS-N spectrograph over ~3.5-years, collecting 81 useful radial velocity measurements. The star is active, with evidence for increasing levels of magnetic activity during the observing time span. The radial velocity scatter is ~17m/s due to the stellar activity contribution, which is much larger that the semi-amplitudes of the planetary signals. We tested different methods for mitigating the stellar activity contribution to the radial velocity time variations and measuring the planet masses with good precision. We find that K2-36 is likely a ~1Gyr old system, and by treating the stellar activity through a Gaussian process regression, we measured the planet masses m_b_=3.9+/-1.1M_{earth}_ and m_c_=7.8+/-2.3M_{earth}_. The derived planet bulk densities {rho}_b_=7.2^+2.5^_-2.1_g/cm^3^ and {rho}_c_=1.3^+0.7^_-0.5^g/cm^3^ point out that K2-36b has a rocky, Earth-like composition, and K2-36c is a low-density sub-Neptune. Composed of two planets with similar orbital separations but different densities, K2-36 represents an optimal laboratory for testing the role of the atmospheric escape in driving the evolution of close-in, low-mass planets after ~1Gyr from their formation. Due to their similarities, we performed a preliminary comparative analysis between the systems K2-36 and Kepler-36, which we deem worthy of a more detailed investigation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/116
- Title:
- Radial velocities of K2-291 with HIRES & HARPS-N
- Short Name:
- J/AJ/157/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-291 is a solar-type star with a radius of R_*_=0.899+/-0.034 R_{sun}_ and mass of M_*_=0.934+/-0.038 M_{sun}_. From the K2 C13 data, we found one super-Earth planet (R_p_=1.589_-0.072_^+0.095^ R_{Earth}_) transiting this star on a short period orbit (P=2.225177_-6.8e-5_^+6.6e-5^ days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass. From our 75 radial velocity measurements using High Resolution Echelle Spectrometer on Keck I and High Accuracy Radial velocity Planet Searcher in the northern hemisphere on Telescopio Nazionale Galileo, we constrained the mass of K2-291 b to M_p_=6.49+/-1.16 M_{Earth}_. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process (GP) in order to more accurately model the effect of stellar noise on our data; the addition of the GP also improved the precision of this mass measurement. With a bulk density of {rho}=8.84_-2.03_^+2.50^ g/cm^3^, the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photoevaporation during the first billion years of the star's lifetime.
- ID:
- ivo://CDS.VizieR/J/AJ/160/3
- Title:
- Radial velocities of M-dwarf LTT 3780 with HARPS
- Short Name:
- J/AJ/160/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT3780 (TIC36724087, TOI-732, V=13.07, Ks=8.204, Rs=0.374R{sun}, Ms=0.401 M{sun}, d=22pc). The two planet candidates are identified in a single Transiting Exoplanet Survey Satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of P_b_=0.77, P_c_=12.25days and sizes r_p,b_=1.33{+/-}0.07, r_p,c_=2.30{+/-}0.16R{earth}, the two planets span the radius valley in period-radius space around low-mass stars, thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial velocity measurements from the High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N, we measure planet masses of m_p,b_=2.62_-0.46_^+0.48^ and m_p,c_=8.6_-1.3_^+1.6^M{earth}, which indicates that LTT3780b has a bulk composition consistent with being Earth-like, while LTT3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and core-powered mass-loss models. The brightness and small size of LTT3780, along with the measured planetary parameters, render LTT3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/29
- Title:
- Radial velocities of TOI-1728 with HPF
- Short Name:
- J/ApJ/899/29
- Date:
- 14 Mar 2022 09:03:00
- Publisher:
- CDS
- Description:
- We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an old, inactive M0 star with Teff=3980_-32_^+31^K, which hosts a transiting super-Neptune at an orbital period of ~3.49days. Joint fitting of the radial velocities and TESS and ground-based transits yields a planetary radius of 5.05_-0.17_^+0.16^ R{Earth}, mass 26.78_-5.13_^+5.43^M{Earth}, and eccentricity 0.057_-0.039_^+0.054^. We estimate the stellar properties, and perform a search for He 10830{AA} absorption during the transit of this planet and claim a null detection with an upper limit of 1.1% with 90% confidence. A deeper level of He 10830{AA} absorption has been detected in the planet atmosphere of GJ3470b, a comparable gaseous planet. TOI-1728b is the largest super-Neptune-the intermediate subclass of planets between Neptune and the more massive gas-giant planets-discovered around an M-dwarf. With its relatively large mass and radius, TOI-1728 represents a valuable data point in the M-dwarf exoplanet mass-radius diagram, bridging the gap between the lighter Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs. With a low bulk density of 1.14_-0.24_^+0.26^g/cm^3^, and orbiting a bright host star (J~9.6, V~12.4), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models.
- ID:
- ivo://CDS.VizieR/J/AJ/155/126
- Title:
- Radial velocities & photometry of the K dwarf HD26965
- Short Name:
- J/AJ/155/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD 26965, with an orbital period of 42.364+/-0.015 days, or alternatively, as the presence of residual, uncorrected rotational activity in the data. Observations include data from HIRES, PFS, CHIRON, and HARPS, where 1111 measurements were made over 16 years. Our best solution for HD 26965 b is consistent with a super-Earth that has a minimum mass of 6.92+/-0.79 M_{Earth}_ orbiting at a distance of 0.215+/-0.008 au from its host star. We have analyzed the correlation between spectral activity indicators and the radial velocities from each instrument, showing moderate correlations that we include in our model. From this analysis, we recover a ~38-day signal, which matches some literature values of the stellar rotation period. However, from independent Mt. Wilson HK data for this star, we find evidence for a significant 42-day signal after subtraction of longer period magnetic cycles, casting doubt on the planetary hypothesis for this period. Although our statistical model strongly suggests that the 42-day signal is Doppler in origin, we conclude that the residual effects of stellar rotation are difficult to fully model and remove from this data set, highlighting the difficulties to disentangle small planetary signals and photospheric noise, particularly when the orbital periods are close to the rotation period of the star. This study serves as an excellent test case for future works that aim to detect small planets orbiting "Sun-like" stars using radial velocity measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A78
- Title:
- Radial velocity and activity indicators
- Short Name:
- J/A+A/653/A78
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Due to their low transit probability, the long-period planets are, as a population, only partially probed by transit surveys. Radial velocity surveys thus have a key role to play, in particular for giant planets. Cold Jupiters induce a typical radial velocity semi-amplitude of 10m/s, which is well within the reach of multiple instruments that have now been in operation for more than a decade. We take advantage of the ongoing radial velocity survey with the sophie high-resolution spectrograph, which continues the search started by its predecessor elodie to further characterize the cold Jupiter population. Methods. Analyzing the radial velocity data from six bright solar-like stars taken over a period of up to 15 years, we attempt the detection and confirmation of Keplerian signals. We announce the discovery of six planets, one per system, with minimum masses in the range 4.8-8.3M_jup_ and orbital periods between 200 days and 10 years. The data do not provide enough evidence to support the presence of additional planets in any of these systems. The analysis of stellar activity indicators confirms the planetary nature of the detected signals. These six planets belong to the cold and massive Jupiter population, and four of them populate its eccentric tail. In this respect, HD 80869 b stands out as having one of the most eccentric orbits, with an eccentricity of 0.862^+0.028^_-0.018_. These planets can thus help to better constrain the migration and evolution processes at play in the gas giant population. Furthermore, recent works presenting the correlation between small planets and cold Jupiters indicate that these systems are good candidates to search for small inner planets.
- ID:
- ivo://CDS.VizieR/J/AJ/155/255
- Title:
- Radial velocity and activity measurements of HAT-P-11
- Short Name:
- J/AJ/155/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HAT-P-11 is a mid-K dwarf that hosts one of the first Neptune-sized planets found outside the solar system. The orbit of HAT-P-11b is misaligned with the star's spin-one of the few known cases of a misaligned planet orbiting a star less massive than the Sun. We find an additional planet in the system based on a decade of precision radial velocity (RV) measurements from Keck/High Resolution Echelle Spectrometer. HAT-P-11c is similar to Jupiter in its mass (M_P_sin i=1.6+/-0.1 M_J_) and orbital period (P=9.3_-0.5_^+1.0^ year), but has a much more eccentric orbit (e=0.60+/-0.03). In our joint modeling of RV and stellar activity, we found an activity-induced RV signal of ~7 m/s, consistent with other active K dwarfs, but significantly smaller than the 31 m/s reflex motion due to HAT-P-11c. We investigated the dynamical coupling between HAT-P-11b and c as a possible explanation for HAT-P-11b's misaligned orbit, finding that planet-planet Kozai interactions cannot tilt planet b's orbit due to general relativistic precession; however, nodal precession operating on million year timescales is a viable mechanism to explain HAT-P-11b's high obliquity. This leaves open the question of why HAT-P-11c may have such a tilted orbit. At a distance of 38 pc, the HAT-P-11 system offers rich opportunities for further exoplanet characterization through astrometry and direct imaging.
- ID:
- ivo://CDS.VizieR/J/AJ/157/141
- Title:
- Radial velocity and light curves of WASP-190
- Short Name:
- J/AJ/157/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of WASP-190b, an exoplanet on a 5.37 day orbit around a mildly evolved F6 IV-V star with V=11.7, T_eff_=6400+/-100 K, M_*_=1.35+/-0.05 M_{sun}_, and R_*_=1.6+/-0.1 R_{sun}_. The planet has a radius of R_P_=1.15+/-0.09 R_Jup_ and a mass of M_P_=1.0+/-0.1 M_Jup_, making it a mildly inflated hot Jupiter. It is the first hot Jupiter confirmed via Doppler tomography with an orbital period of >5 days. The orbit is also marginally misaligned with respect to the stellar rotation, with {lambda}=21{deg}+/-6{deg} measured using Doppler tomography.
- ID:
- ivo://CDS.VizieR/J/AJ/155/24
- Title:
- Radial velocity and planet detectability in alpha Cen
- Short Name:
- J/AJ/155/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use more than a decade of radial-velocity measurements for {alpha} Cen A, B, and Proxima Centauri from the High Accuracy Radial Velocity Planet Searcher, CTIO High Resolution Spectrograph, and the Ultraviolet and Visual Echelle Spectrograph to identify the Msin(i), and orbital periods of planets that could have been detected if they existed. At each point in a mass-period grid, we sample a simulated, Keplerian signal with the precision and cadence of existing data and assess the probability that the signal could have been produced by noise alone. Existing data places detection thresholds in the classically defined habitable zones at about Msin(i) of 53 M_{Earth}_, for {alpha} Cen A, 8.4 M_{Earth}_, for {alpha} Cen B, and 0.47 M_{Earth}_, for Proxima Centauri. Additionally, we examine the impact of systematic errors, or "red noise" in the data. A comparison of white- and red-noise simulations highlights quasi-periodic variability in the radial velocities that may be caused by systematic errors, photospheric velocity signals, or planetary signals. For example, the red-noise simulations show a peak above white-noise simulations at the period of Proxima Centauri b. We also carry out a spectroscopic analysis of the chemical composition of the {alpha} Centauri stars. The stars have super-solar metallicity with ratios of C/O and Mg/Si that are similar to the Sun, suggesting that any small planets in the {alpha} Cen system may be compositionally similar to our terrestrial planets. Although the small projected separation of {alpha} Cen A and B currently hampers extreme-precision radial-velocity measurements, the angular separation is now increasing. By 2019, {alpha} Cen A and B will be ideal targets for renewed Doppler planet surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/156/82
- Title:
- Radial velocity characterization of TESS planets
- Short Name:
- J/AJ/156/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) will conduct a two-year wide-field survey searching for transiting planets around bright stars. Many TESS discoveries will be amenable to mass characterization via ground-based radial velocity measurements with any of a growing suite of existing and anticipated velocimeters in the optical and near-infrared. In this study we present an analytical formalism to compute the number of radial velocity (RV) measurements - and hence the total observing time-required to characterize RV planet masses with the inclusion of either a white or correlated noise activity model. We use our model to calculate the total observing time required to measure all TESS planet masses from the expected TESS planet yield while relying on our current understanding of the targeted stars, stellar activity, and populations of unseen planets that inform the expected RV precision. We also present specialized calculations applicable to a variety of interesting subsets of TESS planets including the characterization of 50 planets smaller than 4 Earth radii, which is expected to take as little as 60 nights of observation. However, the efficient RV characterization of such planets requires a priori knowledge of the "best" targets, which we argue can be identified prior to the conclusion of the TESS planet search based on our calculations. Our results highlight the comparable performance of optical and near-IR spectrographs for most planet populations except for Earths and temperate TESS planets, which are more efficiently characterized in the near-IR. Lastly, we present an online tool to the community to compute the total observing times required to detect any transiting planet using a user-defined spectrograph (RVFC; http://maestria.astro.umontreal.ca/rvfc).
