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311. Radial velocities & light curves of KELT-24
ID:
ivo://CDS.VizieR/J/AJ/158/197
Title:
Radial velocities & light curves of KELT-24
Short Name:
J/AJ/158/197
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V=8.3 mag, K=7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a T_eff_=6509_-49_^+50^ K, a mass of M_*_=1.460_-0.059_^+0.055^ M_{sun}_, a radius of R_*_=1.506+/-0.022 R_{sun}_, and an age of 0.78_-0.42_^+0.61^ Gyr. Its planetary companion (KELT-24 b) has a radius of R_P_=1.272+/-0.021 R_J_ and a mass of M_P_=5.18_-0.22_^+0.21^ M_J_, and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis ({lambda}=2.6_-3.6_^+5.1^). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs.
312. Radial velocities of GJ 357
ID:
ivo://CDS.VizieR/J/A+A/628/A39
Title:
Radial velocities of GJ 357
Short Name:
J/A+A/628/A39
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2.5 V star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot, Earth-sized planet (Teq=525+/-11K) with a radius of R_b_=1.217+/-0.084R_{Earth}_ and an orbital period of P_b_=3.93d. Precise stellar radial velocities from CARMENES and PFS, as well as archival data from HIRES, UVES, and HARPS also display a 3.93-day periodicity, confirming the existence of the planet and leading to a planetary mass of M_b_=1.84+/-0.31M_{Earth}_. In addition to the radial velocity signal for GJ 357 b, more periodicities are present in the data indicating the presence of two more planets in the system: GJ 357 c, with a minimum mass of M_c_=3.40+/-0.46M_{Earth}_ in a 9.12d orbit, and GJ 357 d, with a minimum mass of M_d_=6.1+/-1.0M_{Earth}_ in a 55.7d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period of Prot=78+/-2d. GJ 357 b is to date the second closest transiting planet to the Sun, making it a prime target for further investigations such as transmission spectroscopy. Therefore, GJ 357 b represents one of the best terrestrial planets suitable for atmospheric characterization with the upcoming JWST and ground-based ELTs.
313. Radial velocities of GJ 3779 and GJ 1265
ID:
ivo://CDS.VizieR/J/A+A/620/A171
Title:
Radial velocities of GJ 3779 and GJ 1265
Short Name:
J/A+A/620/A171
Date:
21 Oct 2021
Publisher:
CDS
Description:
We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0+/-0.5M_{Earth}_ and 7.4+/-0.5M_{Earth}_ in low-eccentricity orbits with periods of 3.023+/-0.001d and 3.651+/-0.001d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around three days found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2-5M_{Earth}_. It also indicates that super-Earths (>5M_{Earth}_) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.
314. Radial velocities of HD215152
ID:
ivo://CDS.VizieR/J/A+A/614/A133
Title:
Radial velocities of HD215152
Short Name:
J/A+A/614/A133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of four super-earth planets around HD215152, with orbital periods of 5.76, 7.28, 10.86, and 25.2d, and minimum masses of 1.8, 1.7, 2.8, and 2.9M_Earth_ respectively. This discovery is based on 373 high quality radial velocity measurements taken by HARPS over thirteen years. Given the low masses of the planets, the S/N is not sufficient to constrain the planets eccentricities. However, a preliminary dynamical analysis suggests that eccentricities should be typically lower than about 0.03 for the system to remain stable. With two pairs of planets with a period ratio smaller than 1.5, with short orbital periods, small masses, and small eccentricities, HD215152 is similar to the very compact multi-planet systems found by Kepler, and very rare in RV surveys. This discovery proves that those systems are reachable with the RV technique, however they require a huge amount of observations to be characterized.
315. Radial velocities of K2-36
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.
316. Radial velocities of K2-291 with HIRES & HARPS-N
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.
317. Radial velocities of M-dwarf LTT 3780 with HARPS
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.
318. Radial velocities of TOI-1728 with HPF
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.
319. Radial velocities & photometry of the K dwarf HD26965
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.
320. Radial velocity and activity indicators
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.