Search

Giant planets on long period orbits around the nearest stars are among the easiest to directly image. Unfortunately these planets are difficult to fully constrain by indirect methods, e.g., transit and radial velocity (RV). In this study, we present the discovery of a super-Jupiter, HD 222237 b, orbiting a star located $11.445\pm0.002$ pc away. By combining RV data, Hipparcos and multi-epoch Gaia astrometry, we estimate the planetary mass to be ${5.19}_{-0.58}^{+0.58}\,M_{\rm Jup}$, with an eccentricity of ${0.56}_{-0.03}^{+0.03}$ and a period of ${40.8}_{-4.5}^{+5.8}$ yr, making HD 222237 b a promising target for imaging using the Mid-Infrared Instrument (MIRI) of JWST. A comparative analysis suggests that our method can break the inclination degeneracy and thus differentiate between prograde and retrograde orbits of a companion. We further find that the inferred contrast ratio between the planet and the host star in the F1550C filter ($15.50\,\mu \rm m$) is approximately $1.9\times10^{-4}$, which is comparable with the measured limit of the MIRI coronagraphs. The relatively low metallicity of the host star ($\rm-0.32\,dex$) combined with the unique orbital architecture of this system presents an excellent opportunity to probe the planet-metallicity correlation and the formation scenarios of giant planets., Comment: 18 pages, 10 figures, 3 tables, accepted for publication in MNRAS

Multi-planet systems exhibit a diversity of architectures that diverge from the solar system and contribute to the topic of exoplanet demographics. Radial velocity (RV) surveys form a crucial component of exoplanet surveys, as their long observational baselines allow searches for more distant planetary orbits. This work provides a significantly revised architecture for the multi-planet system HD 134606 using both HARPS and UCLES RVs. We confirm the presence of previously reported planets b, c, and d with periods $12.0897^{+0.0019}_{-0.0018}$, $58.947^{+0.056}_{-0.054}$, and $958.7^{+6.3}_{-5.9}$ days, and masses $9.14^{+0.65}_{-0.63}$, $11.0\pm1$, and $44.5\pm2.9$ Earth masses respectively, with the planet d orbit significantly revised to over double that originally reported. We report two newly detected super-Earths, e and f, with periods $4.31943^{+0.00075}_{-0.00068}$ and $26.9^{+0.019}_{-0.017}$ days, and masses $2.31^{+0.36}_{-0.35}$ and $5.52^{+0.74}_{-0.73}$ Earth masses, respectively. In addition, we identify a linear trend in the RV time series, and the cause of this acceleration is deemed to be a newly detected sub-stellar companion at large separation. HD 134606 now displays four low mass planets in a compact region near the star, one gas giant further out in the Habitable Zone, an additional massive companion in the outer regime, and a low mass M dwarf stellar companion at large separation, making it an intriguing target for system formation/evolution studies. The location of planet d in the Habitable Zone proves to be an exciting candidate for future space-based direct imaging missions, whereas continued RV observations of this system are recommended for understanding the nature of the massive, long period companion., Comment: 23 pages, 10 figures, 4 tables, accepted for publication in the Astronomical Journal

Very little is known about the young planet population because the detection of small planets orbiting young stars is obscured by the effects of stellar activity and fast rotation which mask planets within radial velocity and transit data sets. The few planets that have been discovered in young clusters generally orbit stars too faint for any detailed follow-up analysis. Here we present the characterization of a new mini-Neptune planet orbiting the bright (V=9) and nearby K2 dwarf star, HD 18599. The planet candidate was originally detected in TESS light curves from Sectors 2, 3, 29, and 30, with an orbital period of 4.138~days. We then used HARPS and FEROS radial velocities, to find the companion mass to be 25.5$\pm$4.6~M$_\oplus$. When we combine this with the measured radius from TESS, of 2.70$\pm$0.05~R$_\oplus$, we find a high planetary density of 7.1$\pm$1.4~g cm$^{-3}$. The planet exists on the edge of the Neptune Desert and is the first young planet (300 Myr) of its type to inhabit this region. Structure models argue for a bulk composition to consist of 23% H$_2$O and 77% Rock and Iron. Future follow-up with large ground- and space-based telescopes can enable us to begin to understand in detail the characteristics of young Neptunes in the galaxy., Comment: Accepted in MNRAS

It is commonly accepted that exoplanets with orbital periods shorter than 1 day, also known as ultra-short period (USP) planets, formed further out within their natal protoplanetary disk, before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here, we present the discovery of a four planet system orbiting the bright (V=10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of $\sim$ 13 hours, a mass of 1.42 $\pm$ 0.18 M$_{\oplus}$, a radius of $1.166^{0.061}_{-0.058}$ R$_{\oplus}$, and a mean density of 4.89$^{+1.03}_{-0.88}$ gcm$^{-3}$. Via Doppler spectroscopy, we discovered that the system hosts three outer planets on nearly circular orbits with periods of 6.6, 26.2, and 61.3d and minimum masses of 5.03 $\pm$ 0.41 M$_{\oplus}$, 33.12 $\pm$ 0.88 M$_{\oplus}$ and 15.05$^{+1.12}_{-1.11}$ M$_{\oplus}$, respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits, then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyrs, starting from an initial orbit of 0.02au. TOI-500 is the first four planet system known to host a USP Earth analog whose current architecture can be explained via a non-violent migration scenario., Comment: Published on Nature Astronomy (April 28th, 2022)

TOI-2202 b is a transiting warm Jovian-mass planet with an orbital period of P=11.91 days identified from the Full Frame Images data of five different sectors of the TESS mission. Ten TESS transits of TOI-2202 b combined with three follow-up light curves obtained with the CHAT robotic telescope show strong transit timing variations (TTVs) with an amplitude of about 1.2 hours. Radial velocity follow-up with FEROS, HARPS and PFS confirms the planetary nature of the transiting candidate (a$_{\rm b}$ = 0.096 $\pm$ 0.002 au, m$_{\rm b}$ = 0.98 $\pm$ 0.06 M$_{\rm Jup}$), and dynamical analysis of RVs, transit data, and TTVs points to an outer Saturn-mass companion (a$_{\rm c}$ = 0.155 $\pm$ 0.003 au, m$_{\rm c}$= $0.37 \pm 0.10$ M$_{\rm Jup}$) near the 2:1 mean motion resonance. Our stellar modeling indicates that TOI-2202 is an early K-type star with a mass of 0.82 M$_\odot$, a radius of 0.79 R$_\odot$, and solar-like metallicity. The TOI-2202 system is very interesting because of the two warm Jovian-mass planets near the 2:1 MMR, which is a rare configuration, and their formation and dynamical evolution are still not well understood., Comment: Accepted for publication in AJ

We report the discovery of two short-period Saturn-mass planets, one transiting the G subgiant TOI-954 (TIC 44792534, $ V = 10.343 $, $ T = 9.78 $) observed in TESS sectors 4 and 5, and one transiting the G dwarf K2-329 (EPIC 246193072, $ V = 12.70 $, $ K = 10.67 $) observed in K2 campaigns 12 and 19. We confirm and characterize these two planets with a variety of ground-based archival and follow-up observations, including photometry, reconnaissance spectroscopy, precise radial velocity, and high-resolution imaging. Combining all available data, we find that TOI-954 b has a radius of $0.852_{-0.062}^{+0.053} \, R_{\mathrm{J}}$ and a mass of $0.174_{-0.017}^{+0.018} \, M_{\mathrm{J}}$ and is in a 3.68 day orbit, while K2-329 b has a radius of $0.774_{-0.024}^{+0.026} \, R_{\mathrm{J}}$ and a mass of $0.260_{-0.022}^{+0.020} \, M_{\mathrm{J}}$ and is in a 12.46 day orbit. As TOI-954 b is 30 times more irradiated than K2-329 b but more or less the same size, these two planets provide an opportunity to test whether irradiation leads to inflation of Saturn-mass planets and contribute to future comparative studies that explore Saturn-mass planets at contrasting points in their lifetimes., Comment: 28 pages, 9 figures, 11 tables, accepted by AJ, ancillary data also available at https://github.com/vulpicastor/toi954-data

We present the discovery of TOI 540 b, a hot planet slightly smaller than Earth orbiting the low-mass star 2MASS J05051443-4756154. The planet has an orbital period of $P = 1.239149$ days ($\pm$ 170 ms) and a radius of $r = 0.903 \pm 0.052 R_{\rm Earth}$, and is likely terrestrial based on the observed mass-radius distribution of small exoplanets at similar insolations. The star is 14.008 pc away and we estimate its mass and radius to be $M = 0.159 \pm 0.014 M_{\rm Sun}$ and $R = 0.1895 \pm 0.0079 R_{\rm Sun}$, respectively. The star is distinctive in its very short rotational period of $P_{\rm rot} = 17.4264 +/- 0.0094$ hours and correspondingly small Rossby number of 0.007 as well as its high X-ray-to-bolometric luminosity ratio of $L_X / L_{\rm bol} = 0.0028$ based on a serendipitous XMM-Newton detection during a slew operation. This is consistent with the X-ray emission being observed at a maximum value of $L_X / L_{\rm bol} \simeq 10^{-3}$ as predicted for the most rapidly rotating M dwarfs. TOI 540 b may be an alluring target to study atmospheric erosion due to the strong stellar X-ray emission. It is also among the most accessible targets for transmission and emission spectroscopy and eclipse photometry with JWST, and may permit Doppler tomography with high-resolution spectroscopy during transit. This discovery is based on precise photometric data from TESS and ground-based follow-up observations by the MEarth team., Comment: 18 pages, 7 figures. Accepted for publication in The Astronomical Journal

About one out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultra-short-period planet (Sanchis-ojeda et al. 2014; Winn et al. 2018). All of the previously known ultra-short-period planets are either hot Jupiters, with sizes above 10 Earth radii (Re), or apparently rocky planets smaller than 2 Re. Such lack of planets of intermediate size (the "hot Neptune desert") has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here, we report the discovery of an ultra-short-period planet with a radius of 4.6 Re and a mass of 29 Me, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite (Ricker et al. 2015) revealed transits of the bright Sun-like star \starname\, every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0^(+2.7)_(-2.9)% of the total mass. With an equilibrium temperature around 2000 K, it is unclear how this "ultra-hot Neptune" managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (Vmag=9.8)., Comment: 26 pages, 10 figures, 3 tables. Published in Nature Astronomy (21/09/2020)

Earth-sized planets in the habitable zones of M dwarfs are good candidates for the study of habitability and detection of biosignatures. To search for these planets, we analyze all available radial velocity data and apply four signal detection criteria to select the optimal candidates. We find ten strong candidates satisfying these criteria and three weak candidates showing inconsistency over time due to data samplings. We also confirm three previous planet candidates and improve their orbital solutions through combined analyses of updated data sets. Among the strong planet candidates, HIP 38594 b is a temperate super-Earth with a mass of $8.2 \pm 1.7$ $M_\oplus$ and an orbital period of $60.7\pm0.1$ days, orbiting around an early-type M dwarf. Early-type M dwarfs are less active and thus are better hosts for habitable planets than mid-type and late-type M dwarfs. Moreover, we report the detection of five two-planet systems, including two systems made up of a warm or cold Neptune and a cold Jupiter, consistent with a positive correlation between these two types of planets. We also detect three temperate Neptunes, four cold Neptunes, and four cold Jupiters, contributing to a rarely explored planet population. Due to their proximity to the Sun, these planets on wide orbits are appropriate targets for direct imaging by future facilities such as HabEx and ELT., Comment: 27 pages, 17 figures, 2 tables, accepted for publication by ApJS

The Transiting Exoplanet Survey Satellite mission was designed to find transiting planets around bright, nearby stars. Here we present the detection and mass measurement of a small, short-period ($\approx\,4$\,days) transiting planet around the bright ($V=7.9$), solar-type star HD 86226 (TOI-652, TIC 22221375), previously known to host a long-period ($\sim$1600 days) giant planet. HD 86226c (TOI-652.01) has a radius of $2.16\pm0.08$ $R_{\oplus}$ and a mass of 7.25$^{+1.19}_{-1.12}$ $M_{\oplus}$ based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is $3.97$ g cm$^{-3}$, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well-constrained. Given the host star brightness, planet period, and location of the planet near both the ``radius gap'' and the ``hot Neptune desert'', HD 86226c is an interesting candidate for transmission spectroscopy to further refine its composition., Comment: Accepted in AJ on 22 June 2020

We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V=9.9) G9 dwarf star in a visual binary system observed by the TESS space mission in Sectors 5 and 6. We performed ground-based follow-up observations -- comprised of LCOGT transit photometry, NIRC2 adaptive optics imaging, and FIES, CORALIE, HARPS, HIRES, and PFS high-precision Doppler measurements -- and confirmed the planetary nature of the 16-day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of 5 days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421b, has an orbital period of Pb =5.19672 +- 0.00049 days, a mass of Mb = 7.17 +- 0.66 Mearth and a radius of Rb = 2.68+0.19-0.18 Rearth, whereas the outer warm Neptune, TOI-421 c, has a period of Pc =16.06819 +- 0.00035 days, a mass of Mc = 16.42+1.06-1.04 Mearth, a radius of Rc = 5.09+0.16-0.15 Rearth and a density of rho_c =0.685+0.080-0.072 g cm-3 . With its characteristics the inner planet (rho_b=2.05+0.52-0.41 g cm-3) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421b and TOI-421c are found to be well suitable for atmospheric characterization. Our atmospheric simulations predict significant Ly-alpha transit absorption, due to strong hydrogen escape in both planets, and the presence of detectable CH_4 in the atmosphere of TOI-421c if equilibrium chemistry is assumed.

We report the detection of a transiting, dense Neptune planet candidate orbiting the bright ($V=8.6$) K0.5V star HD 95338. Detection of the 55-day periodic signal comes from the analysis of precision radial velocities from the Planet Finder Spectrograph on the Magellan II Telescope. Follow-up observations with HARPS also confirm the presence of the periodic signal in the combined data. HD 95338 was also observed by the Transiting Exoplanet Survey Satellite ({\it TESS}) where we identify a clear single transit in the photometry. A Markov Chain Monte Carlo period search on the velocities allows strong constraints on the expected transit time, matching well the epoch calculated from \tess{} data, confirming both signals describe the same companion. A joint fit model yields an absolute mass of 42.44$^{+2.22}_{-2.08} M_{\oplus}$ and a radius of 3.89$^{+0.19}_{-0.20}$ $R_{\oplus}$ which translates to a density of 3.98$^{+0.62}_{-0.64}$ \gcm\, for the planet. Given the planet mass and radius, structure models suggest it is composed of a mixture of ammonia, water, and methane. HD 95338\,b is one of the most dense Neptune planets yet detected, indicating a heavy element enrichment of $\sim$90\% ($\sim38\, M_{\oplus}$). This system presents a unique opportunity for future follow-up observations that can further constrain structure models of cool gas giant planets., Comment: 13 pages, 11 figures, MNRAS accepted

Zechmeister et al. (2009) surveyed 38 nearby M dwarfs from March 2000 to March 2007 with VLT2 and the UVES spectrometer. This data has recently been reanalyzed (Butler et al. 2019), yielding a significant improvement in the Doppler velocity precision. Spurred by this, we have combined the UVES data with velocity sets from HARPS, Magellan/PFS, and Keck/HIRES. Sixteen planet candidates have been uncovered orbiting nine M dwarfs. Five of them are new planets corresponding to radial velocity signals, which are not sensitive to the choice of noise models and are identified in multiple data sets over various timespans. Eight candidate planets require additional observation to be confirmed. We also confirm three previously reported planets. Among the new planets, GJ 180 d and GJ 229A c are super-Earths located in the conservative habitable zones of their host stars. We investigate their dynamical stability using the Monte Carlo approach and find both planetary orbits are robust to the gravitational perturbations of the companion planets. Due to their proximity to the Sun, the angular separation between the host stars and the potentially habitable planets in these two systems is 25 and 59 mas, respectively. They are thus good candidates for future direct imaging by JWST and E-ELT. In addition we find GJ 433 c, a cold super-Neptune belonging to an unexplored population of Neptune-like planets. With a separation of 0.5 as from its host star, GJ 433 c is probably the first realistic candidate for direct imaging of cold Neptunes. A comprehensive survey of these planets is important for the studies of planet formation., Comment: 38 pages, 31 figures, 4 tables

Earth mass exoplanets are difficult to detect. The Dispersed Matter Planet Project (DMPP) identifies stars which are likely to host the most detectable low mass exoplanets. The star DMPP-3 (HD 42936) shows signs of circumstellar absorption, indicative of mass loss from ablating planets. Here we report the radial velocity (RV) discovery of a highly eccentric 507 d binary companion and a hot super-Earth planet in a 6.67 d orbit around the primary star. DMPP-3A is a solar type star while DMPP-3B is just massive enough to fuse hydrogen. The binary, with semi-major axis 1.22 $\pm$ 0.02 AU, is considerably tighter than others known to host planets orbiting only one of the component stars. The configuration of the DMPP-3 planetary system is rare and indicates dynamical interactions, though the evolutionary history is not entirely clear. DMPP-3Ab is possibly the residual core of a giant planet precursor, consistent with the inferred circumstellar gas shroud., Comment: Accepted for publication by Nature Astronomy on 12th November 2019 (Main article, Methods and Supplementary Information; 18 pages, 4 figures, 3 tables)

The Neptune desert is a feature seen in the radius-mass-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here we report the {\it TESS} discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC\,8003-1117-1 (TOI-132). {\it TESS} photometry shows transit-like dips at the level of $\sim$1400 ppm occurring every $\sim$2.11 days. High-precision radial velocity follow-up with HARPS confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of $\sim$11.5 m s$^{-1}$, which, when combined with the stellar mass of $0.97\pm0.06$ $M_{\odot}$, provides a planetary mass of 22.83$^{+1.81}_{-1.80}$ $M_{\oplus}$. Modeling the {\it TESS} high-quality light curve returns a planet radius of 3.43$^{+0.13}_{-0.14}$ $R_{\oplus}$, and therefore the planet bulk density is found to be 3.11$^{+0.44}_{-0.450}$ g cm$^{-3}$. Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3$^{+1.2}_{-2.3}$\%. TOI-132 b is a {\it TESS} Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding the Neptune desert., Comment: 12 pages, 10 figures, 4 tables. Submitted to MNRAS. Comments welcome. Missing labels, Typos fixed

We report the detection of a new planetary system orbiting the nearby M2.5V star GJ357, using precision radial-velocities from three separate echelle spectrographs, HARPS, HiRES, and UVES. Three small planets have been confirmed in the system, with periods of 9.125+/-0.001, 3.9306+/-0.0003, and 55.70+/-0.05 days, and minimum masses of 3.33+/-0.48, 2.09+/-0.32, and 6.72+/-0.94 Me, respectively. The second planet in our system, GJ357c, was recently shown to transit by the Transiting Exoplanet Survey Satellite (TESS; Luque et al. 2019), but we could find no transit signatures for the other two planets. Dynamical analysis reveals the system is likely to be close to coplanar, is stable on Myrs timescales, and places strong upper limits on the masses of the two non-transiting planets b and d of 4.25 and 11.20 Me, respectively. Therefore, we confirm the system contains at least two super-Earths, and either a third super-Earth or mini-Neptune planet. GJ357b & c are found to be close to a 7:3 mean motion resonance, however no libration of the orbital parameters was found in our simulations. Analysis of the photometric lightcurve of the star from the TESS, when combined with our radial-velocities, reveal GJ357c has an absolute mass, radius, and density of 2.248+0.117-0.120 Me, 1.167+0.037-0.036 Re, and 7.757+0.889-0.789 g/cm3, respectively. Comparison to super-Earth structure models reveals the planet is likely an iron dominated world. The GJ357 system adds to the small sample of low-mass planetary systems with well constrained masses, and further observational and dynamical follow-up is warranted to better understand the overall population of small multi-planet systems in the solar neighbourhood., Comment: Manuscript accepted to MNRAS 15/10/2019

The radial velocity method plays a major role in the discovery of nearby exoplanets. To efficiently find planet candidates from the data obtained in high precision radial velocity surveys, we apply a signal diagnostic framework to detect radial velocity signals that are statistically significant, consistent in time, robust to the choice of noise models, and not correlated with stellar activity. Based on the application of this approach to the survey data of the Planet Finder Spectrograph (PFS), we report fifteen planet candidates located in fourteen stellar systems. We find that the orbits of the planet candidates around HD 210193, 103949, 8326, and 71135 are consistent with temperate zones around these stars (where liquid water could exist on the surface). With periods of 7.76 and 15.14 days respectively, the planet candidates around star HIP 54373 form a 1:2 resonance system. These discoveries demonstate the feasibility of automated detection of exoplanets from large radial velocity surveys, which may provide a complete sample of nearby Earth analogs., Comment: 30 pages, 20 figures, 3 tables, accepted for publication in ApJS

We describe a new method to derive clean, iodine-free spectra directly from observations acquired using high-resolution echelle spectrographs equipped with iodine cells. The main motivation to obtain iodine-free spectra is to use portions of the spectrum that are superimposed with the dense forest of iodine absorption lines, in order to retrieve lines that can be used to monitor the magnetic activity of the star, helping to validate candidate planets. In short, we provide a straight-forward methodology to clean the spectra by using the forward model used to derive radial velocities, the Line Spread Function information plus the stellar spectrum without iodine to reconstruct and subtract the iodine spectrum from the observations. We show our results using observations of the star $\tau$ Ceti acquired with the PFS, HIRES and UCLES spectrographs, reaching an iodine-free spectrum correction at the $\sim$1% RMS level. We additionally discuss the limitations and further applications of the method., Comment: 15 pages, 7 figures. Accepted for publication in AJ

We report the detection of a hot Jupiter ($M_{p}=1.75_{-0.17}^{+0.14}\ M_{J}$, $R_{p}=1.38\pm0.04\ R_{J}$) orbiting a middle-aged star ($\log g=4.152^{+0.030}_{-0.043}$) in the Transiting Exoplanet Survey Satellite (TESS) southern continuous viewing zone ($\beta=-79.59^{\circ}$). We confirm the planetary nature of the candidate TOI-150.01 using radial velocity observations from the APOGEE-2 South spectrograph and the Carnegie Planet Finder Spectrograph, ground-based photometric observations from the robotic Three-hundred MilliMeter Telescope at Las Campanas Observatory, and Gaia distance estimates. Large-scale spectroscopic surveys, such as APOGEE/APOGEE-2, now have sufficient radial velocity precision to directly confirm the signature of giant exoplanets, making such data sets valuable tools in the TESS era. Continual monitoring of TOI-150 by TESS can reveal additional planets and subsequent observations can provide insights into planetary system architectures involving a hot Jupiter around a star about halfway through its main-sequence life., Comment: 13 pages, 3 figures, 2 tables, accepted to ApJL

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. HD1397b has a mass of ${\rm M_P}$ = $0.335_{-0.018}^{+0.018}$ ${\rm M_J}$, a radius of ${\rm R_P}$ = $1.021_{-0.014}^{+0.015}$ ${\rm M_J}$, and orbits its bright host star ($V = 7.8$ mag) with an orbital period of $11.53508 \pm 0.00057 $ d, on a moderately eccentric orbit ($e$ = 0.210 $\pm$ 0.038). With a mass of ${\rm M}_{\star}$ = $1.284_{-0.016}^{+0.020}$ ${\rm M}_{J}$, a radius of ${\rm R}_{\star}$ = 2.314$_{-0.042}^{+0.049}$ ${\rm R_J}$, and an age of 4.7 $\pm$ 0.2 Gyr, the solar metallicity host star has already departed from the main sequence. We find evidence in the radial velocity measurements for a long term acceleration, and a $P \approx 18$ d periodic signal that we attribute to rotational modulation by stellar activity. The HD1397 system is among the brightest systems 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., Comment: 15 pages, submitted to AJ

We report the discovery of EPIC 201498078b, which was first identified as a planetary candidate from Kepler K2 photometry of Campaign 14, and whose planetary nature and orbital parameters were then confirmed with precision radial velocities. EPIC 201498078b is half as massive as Saturn ($\rm M_P$=$0.179 \pm 0.021$ $\rm M_J$), and has a radius of $\rm R_P$=$0.840 \pm 0.011$ $\rm R_J$, which translates into a bulk density of $ \rm \rho_P$=$0.37 \pm 0.05$ g cm$^{-3}$. EPIC 201498078b transits its slightly evolved G-type host star ($\rm M_{\star}$=$1.105 \pm 0.019$ $\rm M_{\odot}$, $\rm R_P$=$1.669 \pm 0.022$ $\rm R_{\odot}$) every $11.63364 \pm 0.00010$ days and presents a significantly eccentric orbit ($e=0.420 \pm 0.034$). We estimate a relatively short circularization timescale of 1.8 Gyr for the planet, but given the advanced age of the system we expect the planet to be engulfed by its evolving host star in $\sim 1$ Gyr before the orbit circularizes. The low density of the planet coupled to the brightness of the host star ($J=9.4$) makes this system one of the best candidates known to date in the super-Neptune regime for atmospheric characterization via transmission spectroscopy, and to further study the transition region between ice and gas giant planets., Comment: submitted to MNRAS, 11 pages, 10 figures

We report the discovery of EPIC247098361b using photometric data of the Kepler K2 satellite coupled with ground-based spectroscopic observations. EPIC247098361b has a mass of M$_{P}=0.397\pm 0.037$ M$_J$, a radius of R$_{P}=1.00 \pm 0.020$ R$_J$, and a moderately low equilibrium temperature of $T_{eq}=1030 \pm 15$ K due to its relatively large star-planet separation of $a=0.1036$ AU. EPIC247098361b orbits its bright ($V=9.9$) late F-type host star in an eccentric orbit ($e=0.258 \pm 0.025$) every 11.2 days, and is one of only four well characterized warm Jupiters having hosts stars brighter than $V=10$. We estimate a heavy element content of 20 $\pm$ 7 M$_{\oplus}$ for EPIC247098361b, which is consistent with standard models of giant planet formation. The bright host star of EPIC247098361b makes this system a well suited target for detailed follow-up observations that will aid in the study of the atmospheres and orbital evolution of giant planets at moderate separations from their host stars., Comment: 11 pages, 10 figures, submitted to MNRAS

We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital period of 42.364$\pm$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 1,111 measurements were made over 16 years. Our best solution for HD26965 $b$ is consistent with a super-Earth that has a minimum mass of 6.92$\pm$0.79 M$_{\oplus}$ orbiting at a distance of 0.215$\pm$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 $\sim$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 dataset, 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., Comment: 16 pages, 10 figures, 13 tables, accepted for publication in AJ