New HARPS Planets

New HARPS planets!

The HARPS search for southern extra-solar planets XXXVI: Five new long-period giant planets and a system update

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We describe radial-velocity time series obtained by HARPS on the 3.60 m telescope in La Silla (ESO, Chile) over ten years and report the discovery of five new giant exoplanets in distant orbits; these new planets orbit the stars HD 564, HD 30669, HD 108341, and BD-114672. Their periods range from 492 to 1684 days, semi-major axes range from 1.2 to 2.69 AU, and eccentricities range from 0 to 0.85. Their minimum mass ranges from 0.33 to 3.5 Mjup. We also refine the parameters of two planets announced previously around HD 113538, based on a longer series of measurements. The planets have a period of 663+-8 and 1818+-25 days, orbital eccentricities of 0.14+-0.08 and 0.20+-0.04, and minimum masses of 0.36+-0.04 and 0.93+-0.06 Mjup. Finally, we report the discovery of a new hot-Jupiter planet around an active star, HD 103720; the planet has a period of 4.5557+-0.0001 days and a minimum mass of 0.62+-0.025 Mjup. We discuss the fundamental parameters of these systems and limitations due to stellar activity in quiet stars with typical 2m/s radial velocity precision.

Glad to see that BD-11° 4672 b is treated no more as stellar activity but as planet.

Hmm losing track of which HARPS planets have been published or not... don't think these were in the original batch of 32 though.

Yes, these are mostly new. They should go in their own thread, like the previous HARPS paper.

All of the results seem fairly ordinary. I did notice the revised period for HD 113538 b earlier this year when working with the archive, but concluded it was dynamically difficult (P2/P1 ≈ 2.7). Now the solution is unambiguous, so I'll have to see if it's less unstable.

Also, they really didn't check whether the Hot Jupiter is transiting? I can't find any transit surveys that have observed the star, so it's not implausible…

High eccentricty for HD 108341b (is it just my software, or are various bits of the text non-readable, e.g. most of the star names in table 2) - pity the argument of periastron isn't near 90 degrees which would be most helpful for transits, or 270 degrees for eclipses.

Looks like it's the actual text. I'm unable to read it as well.

Follow-up. I've downloaded the paper's source and looked at the LaTeX, fixed some rather sloppy errors/typos and recompiled it. The author defined LaTeX commands \a, \b, \c, \d, ... etc to define each of the star names and it doesn't look like they were particularly consistent between the definitions and how they were called in the paper (for example, even in a definition line, a letter is doubled). Rather than re-post the entire paper, I've taken a screenshot of the relevant table and posted it here.

Great, thanks!

HD22496b: the first ESPRESSO standalone planet discovery

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The ESPRESSO spectrograph is a new powerful tool to detect and characterize extrasolar planets. Its design allows unprecedented radial velocity precision (down to a few tens of cm/s) and long-term thermo-mechanical stability. We present the first standalone detection of an extrasolar planet by blind radial velocity search using ESPRESSO and aim at showing the power of the instrument in characterizing planetary signals at different periodicities in long time spans. We use 41 ESPRESSO measurements of HD\,22496 within a time span of 895 days with a median photon noise of 18 cm/s. A radial velocity analysis is performed to test the presence of planets in the system and to account for the stellar activity of this K5-K7 main sequence star. For benchmarking and comparison, we attempt the detection with 43 archive HARPS measurements and compare the results yielded by the two datasets. We also use four TESS sectors to search for transits. We find radial velocity variations compatible with a close-in planet with an orbital period of P=5.09071±0.00026 days when simultaneously accounting for the effects of stellar activity at longer time scales (Prot=34.99+0.58−0.53 days). We characterize the physical and orbital properties of the planet and find a minimum mass of 5.57+0.73−0.68 M⊕, right in the dichotomic regime between rocky and gaseous planets. Although not transiting according to TESS data, if aligned with the stellar spin axis, the absolute mass of the planet must be below 16 M⊕. We find no significant evidence for additional signals with semi-amplitudes above 56 cm/s at 95% confidence. With a modest set of radial velocity measurements, ESPRESSO is capable of detecting and characterizing low-mass planets and constrain the presence of planets in the habitable zone of K-dwarfs down to the rocky-mass regime.

Considering the lesser frequency RV planets are being announced lately, I would suggest to create a dedicated post for "RV detections", except for HARPS planets which already have their own thread.

Analysis of the public HARPS/ESO spectroscopic archive -- Jupiter-like planets around HD 103891 and HD 105779

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We use the recently published database (Trifonov et al. 2020) of radial velocities (RVs) that were derived from fifteen years of HARPS/ESO observations to search for planet candidates. Methods. For targets with sufficient RV data, we apply an automated algorithm to identify significant periodic signals and fit a Keplerian model for orbital estimates. We also search the auxiliary data of stellar-activity indices and compare our findings with existing literature, to detect periodic RV signals that have no counterpart in the activity timeseries. The most convincing signals are then manually inspected to designate additional false planet detection, focusing the search on long-period (P > 1 000 d) massive candidates around FGK dwarf stars. Results. We identify two Jupiter analogs, in orbit around the slightly evolved F8V star HD 103891 and the Solar-like star HD 105779. We use nested sampling to derive their orbital parameters, and find their orbital periods to be 1919 +/- 16 d and 2412 +/- 54 d, while their minimum masses are 1.44 +/- 0.02 M Jup and 0.64 +/- 0.06 M Jup , respectively. While the orbit of HD 103891 b is slightly eccentric (e = 0.31 +/- 0.03), that of HD 105779 b is likely circular (e < 0.16). Conclusions. With minimum astrometric signatures of 59 and 42 μas, HD 103891 b and HD 105779 b join the growing sample of planets whose exact masses may soon be derived with Gaia astrometry. This finding also highlights the importance of long-term RV surveys to study planetary occurrence beyond the snow line of Solar-like stars.

Astonishing find: third planet in Pi Mensae system detected by HARPS!

A Radial Velocity Study of the Planetary System of Pi Mensae: Improved Planet Parameters for PI Mensae c and a Third Planet on a 125-d Orbit

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Pi Men hosts a transiting planet detected by the TESS space mission and an outer planet in a 5.7-yr orbit discovered by RV surveys. We studied this system using new radial velocity (RV) measurements taken with the HARPS spectrograph on ESO's 3.6-m telescope as well as archival data. We constrain the stellar RV semi-amplitude due to the transiting planet, Pi Men c, as K_c = 1.21 +/- 0.12 m/s resulting in a planet mass of M_c = 3.63 +/- 0.38 M_Earth. A planet radius of R_c= 2.145 +/- 0.015 R_Earth yields a bulk density of rho = 2.03 +/- 0.22 g/cm^{-3}. The precisely determined density of this planet and the brightness of the host star make Pi Men c an excellent laboratory for internal structure and atmospheric characterization studies. Our HARPS RV measurements also reveal compelling evidence for a third body, PI Men d, with a minimum mass M sin i = 13.38 +/- 1.35 M_Earth orbiting with a period of P_d = 125 d on an eccentric orbit (e = 0.22). A simple dynamical analysis indicates that the orbit of Pi Men d is stable on timescales of at least 20 Myrs. Given the mutual inclination between the outer gaseous giant and the inner rocky planet and the presence of a third body at 125 d, Pi Men is an important planetary system for dynamical and formation studies.

New HARPS planet at nearby M dwarfs (Gliese 21, Gliese 548 A, GJ 1074, GJ 3822, GJ 9404) are announced (dedicated discovery papers are forthcoming) plus several long period planet and brown dwarf candidates. Interesting case that of GJ 412 A, which has two TESS transiting planet candidates.

HADES RV Programme with HARPS-N at TNG XV. Planetary occurrence rates around early-M dwarfs

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We present the complete Bayesian statistical analysis of the HArps-n red Dwarf Exoplanet Survey (HADES), which monitored the radial velocities of a large sample of M dwarfs with HARPS-N at TNG, over the last 6 years. The targets were selected in a narrow range of spectral types from M0 to M3, 0.3 M⊙<M⋆<0.71 M⊙, in order to study the planetary population around a well-defined class of host stars. We take advantage of Bayesian statistics to derive an accurate estimate of the detectability function of the survey. Our analysis also includes the application of Gaussian Process approach to take into account stellar activity induced radial velocity variations, and improve the detection limits, around the most-observed and most-active targets. The Markov chain Monte Carlo and Gaussian process technique we apply in this analysis has proven very effective in the study of M-dwarf planetary systems, helping the detection of most of the HADES planets. From the detectability function we can calculate the occurrence rate of small mass planets around early-M dwarfs, either taking into account only the 11 already published HADES planets or adding also the 5 new planetary candidates discovered in this analysis, and compare them with the previous estimates of planet occurrence around M-dwarf or Solar-type stars: considering only the confirmed planets, we find the highest frequency for low-mass planets (1 M⊕<mpsini<10 M⊕) with periods 10 d<P<100 d, focc=85+5−19%, while for short-period planets (1 d<P<10 d) we find a frequency of focc=10.3+8.4−3.3%, significantly lower than for later-M dwarfs. These results, and their comparison with other surveys focused on different stellar types, confirms the central role that stellar mass plays in the formation and evolution of planetary systems.

L 363-38 b: a planet newly discovered with ESPRESSO orbiting a nearby M dwarf star
https://arxiv.org/abs/2210.12710

Independent validation of the temperate Super-Earth HD79211 b using HARPS-N
https://arxiv.org/abs/2210.12211

I'm not sure if the former paper fits the topic, anyway...

Direct imaging discovery of a high-mass brown dwarf around HD 176535

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Brown Dwarfs (BD) with well-measured masses, age and luminosities are important benchmark objects to test BD formation and evolutionary models. We present the direct imaging discovery of a substellar companion to HD 176535A, a Sun-like K3.5 (V) star aged 5.04 ± 1.45 Gyrs at a distance of 37.0 ± 0.024 pc. The radial velocity of the star is from the High Accuracy velocity Planet Searcher (HARPS) spectrograph based on 11 years of monitoring. Our high-contrast imaging observation with the Keck/NIRC2 coronagraph revealed a companion (L'p = 13.39 ± 0.14 mag) at 0.35" or 10.98 AU. We perform a joint fit of the archival RVs, our single-epoch relative astrometry, and complementary absolute astrometry from Hipparcos and Gaia EDR3 catalog of accelerations, using an open-source orbit fitting python code orvara. We obtain a precise dynamical mass of 65.7-1.6+2.0 MJup for the high-mass brown dwarf HD 176535B. We conclude that HD 176535B will be a great candidate for more future high-contrast imaging observations with instruments such as CHARIS, which will further help us to refine its orbital parameters and atmospheric characterizations.

A Jupiter analogue and a cold Super-Neptune orbiting the solar-twin star HIP 104045

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We present the discovery of two planets around the solar twin HIP 104045 via radial velocity data obtained with the ESO/HARPS spectrograph as part of the Solar Twin Planet Search observing programme. The joint Keplerian and Gaussian Process model fit accounting for both planetary and intrinsic stellar modulations, as well as no timing-radial velocity correlations of several activity tracers of the host star, reveal the presence of a Jupiter analogue m sin i_b = 0.498±0.074 M_Jup under circular orbit with P_b = 2315±310 days and a cold Super-Neptune m sin i_c = 43.15±10.3 M⊕ under circular orbit with P_c = 316±75 days.

Quite a pleasant Summer this year

A review of planetary systems around HD 99492, HD 147379 and HD 190007 with HARPS-N
https://arxiv.org/abs/2308.05669

Multi techniques approach to identify and/or constrain radial velocity sub-stellar companions
https://arxiv.org/abs/2308.05417