Radial Velocity Surveys Research Articles

TESS Asteroseismic Masses and Radii of Red Giants with (and without) Planets

We present a study of asteroseismically derived surface gravities, masses, and radii of a sample of red giant stars both with and without confirmed planetary companions using TESS photometric light curves. These red giants were drawn from radial velocity surveys, and their reported properties in the literature rely on more traditional methods using spectroscopy and isochrone fitting. Our asteroseismically derived surface gravities achieved a precision of ∼0.01 dex; however, they were on average ∼0.1 dex smaller than the literature. The systematic larger gravities of the literature could plausibly present as a systematic overestimation of stellar masses, which would in turn lead to overestimated planetary masses of the companions. We find that the fractional discrepancies between our asteroseismically determined parameters and those previously found are typically larger for stellar radii (∼10% discrepancy) than for stellar masses (<5% discrepancy). However, no evidence of a systematic difference between methods was found for either fundamental parameter. Two stars, HD 100065 and HD 18742, showed significant disagreement with the literature in both mass and radii. We explore the impacts of updated stellar properties on inferred planetary properties and caution that red giant radii may be more poorly constrained than uncertainties suggest.

Unveiling Subarcsecond Multiplicity in the Pleiades with Gaia Multicolor Photometry

The list of 409 probable cluster members down to G = 15mag (m ≳ 0.5M ⊙) is compiled for the two degree radius of the Pleiades, based on astrometric data from Gaia DR3 and the PPMXL catalog, along with several radial velocity surveys, including APOGEE and LAMOST. This approach allows for the inclusion of binary stars with unreliable Gaia solutions, thereby eliminating associated bias. Thus, the often-neglected 14 sources with Gaia two-parameter solutions are included. The subsequent analysis of color–magnitude and color–color diagrams exploits artifacts in Gaia photometric data, caused by the different field sizes used to measure fluxes in the G, B p , and R p passbands, to reveal binary stars with subarcsecond angular separation. The findings are validated with prior high-resolution observations. Overall, 24 ± 3 cluster members with angular separation between 0.″1 and 1″ (13.5–135 au projected distance) and mass ratio q > 0.5 are deemed binary, indicating a binarity fraction of 6 ± 1%.

The mean longitudinal magnetic field and its uses in radial-velocity surveys

ABSTRACT This work focuses on the analysis of the mean longitudinal magnetic field as a stellar activity tracer in the context of small exoplanet detection and characterization in radial-velocity (RV) surveys. We use Solar Dynamics Observatory/Helioseismic and Magnetic Imager filtergrams to derive Sun-as-a-star magnetic field measurements, and show that the mean longitudinal magnetic field is an excellent rotational period detector and a useful tracer of the solar magnetic cycle. To put these results into context, we compare the mean longitudinal magnetic field to three common activity proxies derived from HARPS-N Sun-as-a-star data: the full width at half-maximum, the bisector span, and the S-index. The mean longitudinal magnetic field does not correlate with the RVs and therefore cannot be used as a one-to-one proxy. However, with high cadence and a long baseline, the mean longitudinal magnetic field outperforms all other considered proxies as a solar rotational period detector, and can be used to inform our understanding of the physical processes happening on the surface of the Sun. We also test the mean longitudinal magnetic field as a ‘stellar proxy’ on a reduced solar data set to simulate stellar-like observational sampling. With a Gaussian Process regression analysis, we confirm that the solar mean longitudinal magnetic field is the most effective of the considered indicators, and is the most efficient rotational period indicator over different levels of stellar activity. This work highlights the need for polarimetric time series observations of stars.

Influence of Orbit and Mass Constraints on Reflected Light Characterization of Directly Imaged Rocky Exoplanets

Survey strategies for upcoming exoplanet direct imaging missions have considered varying assumptions of prior knowledge. Precursor radial velocity surveys could have detected nearby exo-Earths and provided prior orbit and mass constraints. Alternatively, a direct imaging mission performing astrometry could yield constraints on the orbit and phase angle of target planets. Understanding the impact of prior mass and orbit information on planetary characterization is crucial for efficiently recognizing habitable exoplanets. To address this question, we use a reflected-light retrieval tool to infer the atmospheric and bulk properties of directly imaged Earth-analogs while considering varying levels of prior information and signal-to-noise ratio (S/N). Because of the strong correlation between the orbit-related parameters and the planetary radius, prior information on the orbital distance and planetary phase angle yield much tighter constraints on the planetary radius: from Rp=2.95−1.95+2.69R⊕ without prior knowledge, to Rp=1.01−0.19+0.33R⊕ with prior determination of the orbit for S/N = 20 in the visible/near-infrared spectral range, thus allowing size determination from reflected light observations. However, additional knowledge of planet mass does not notably enhance radius ( Rp=0.98−0.14+0.17R⊕ ) or atmospheric characterization. Also, prior knowledge of the mass alone does not yield a tight radius constraint ( Rp=1.64−0.80+1.29R⊕ ) nor improves atmospheric composition inference. By contrast, because of its sensitivity to gas column abundance, detecting a Rayleigh scattering slope or bounding Rayleigh opacity helps to refine gas mixing ratio inferences without requiring prior mass knowledge. Overall, apart from radius determination, increasing the S/N is more beneficial than additional prior observations.

BEBOP V. Homogeneous stellar analysis of potential circumbinary planet hosts

ABSTRACT Planets orbiting binary systems are relatively unexplored compared to those around single stars. Detections of circumbinary planets and planetary systems offer a first detailed view into our understanding of circumbinary planet formation and dynamical evolution. The BEBOP (binaries escorted by orbiting planets) radial velocity survey plays a special role in this adventure as it focuses on eclipsing single-lined binaries with an FGK dwarf primary and M dwarf secondary allowing for the highest radial velocity precision using the HARPS and SOPHIE spectrographs. We obtained 4512 high-resolution spectra for the 179 targets in the BEBOP survey which we used to derive the stellar atmospheric parameters using both equivalent widths and spectral synthesis. We furthermore derive stellar masses, radii, and ages for all targets. With this work, we present the first homogeneous catalogue of precise stellar parameters for these eclipsing single-lined binaries.

Search for giant planets in M 67 V: A warm Jupiter orbiting the turn-off star S1429

Context. Planets orbiting members of open or globular clusters offer a great opportunity to study exoplanet populations systematically, as stars within clusters provide a mostly homogeneous sample, at least in chemical composition and stellar age. However, even though there have been coordinated efforts to search for exoplanets in stellar clusters, only a small number of planets have been detected. One successful example is the seven-year radial velocity (RV) survey ‘Search for giant planets in M 67’ of 88 stars in the open cluster M 67, which led to the discovery of five giant planets, including three close-in (P &lt; 10 days) hot-Jupiters. Aims. In this work, we continue and extend the observation of stars in M 67, with the aim being to search for additional planets. Methods. We conducted spectroscopic observations with the Habitable Planet Finder (HPF), HARPS, HARPS-North, and SOPHIE spectrographs of 11 stars in M 67. Six of our targets showed a variation or long-term trends in their RV during the original survey, while the other five were not observed in the original sample, bringing the total number of stars to 93. Results. An analysis of the RVs reveals one additional planet around the turn-off point star S1429 and provides solutions for the orbits of stellar companions around S2207 and YBP2018. S1429 b is a warm-Jupiter on a likely circular orbit with a period of $\[\77.48_{-0.19}^{+0.18}\]$ days and a minimum mass of M sin i = 1.80 ± 0.2 MJ. We update the hot-Jupiter occurrence rate in M 67 to include the five new stars, deriving $\[\4.2_{-2.3}^{+4.1} \%\]$ when considering all stars, and $\[\5.4_{-3.0}^{+5.1} \%\]$ if binary star systems are removed.

The TESS-Keck Survey. XX. 15 New TESS Planets and a Uniform RV Analysis of All Survey Targets

The Transiting Exoplanet Survey Satellite (TESS) has discovered hundreds of new worlds, with TESS planet candidates now outnumbering the total number of confirmed planets from Kepler. Owing to differences in survey design, TESS continues to provide planets that are better suited for subsequent follow-up studies, including mass measurement through radial velocity (RV) observations, compared to Kepler targets. In this work, we present the TESS-Keck Survey’s (TKS) Mass Catalog: a uniform analysis of all TKS RV survey data that has resulted in mass constraints for 126 planets and candidate signals. This includes 58 mass measurements that have reached ≥5σ precision. We confirm or validate 32 new planets from the TESS mission either by significant mass measurement (15) or statistical validation (17), and we find no evidence of likely false positives among our entire sample. This work also serves as a data release for all previously unpublished TKS survey data, including 9,204 RV measurements and associated activity indicators over our three-year survey. We took the opportunity to assess the performance of our survey and found that we achieved many of our goals, including measuring the mass of 38 small (<4 R ⊕) planets, nearly achieving the TESS mission’s basic science requirement. In addition, we evaluated the performance of the Automated Planet Finder as survey support and observed meaningful constraints on system parameters, due to its more uniform phase coverage. Finally, we compared our measured masses to those predicted by commonly used mass–radius relations and investigated evidence of systematic bias.

TESS and ESPRESSO discover a super-Earth and a mini-Neptune orbiting the K-dwarf TOI-238

The number of super-Earth and mini-Neptune planet discoveries has increased significantly in the last two decades thanks to transit and radial velocity (RV) surveys. When it is possible to apply both techniques, we can characterise the internal composition of exoplanets, which in turn provides unique insights on their architecture, formation and evolution. We performed a combined photometric and RV analysis of TOI-238 (TYC 6398-132-1), which has one short-orbit super-Earth planet candidate announced by NASA’s TESS team. We aim to confirm its planetary nature using radial velocities taken with the ESPRESSO and HARPS spectrographs, to measure its mass, and to detect the presence of other possible planetary companions. We carried out a joint analysis by including Gaussian processes and Keplerian orbits to account for the stellar activity and planetary signals simultaneously. We detected the signal induced by TOI-238 b in the RV time series, and the presence of a second transiting planet, TOI-238 c, whose signal appears in RV and TESS data. TOI-238 b is a planet with a radius of 1.402−0.086+0.084 R⊕ and a mass of 3.40−0.45+0.46 M⊕. It orbits at a separation of 0.02118 ± 0.00038 au of its host star, with an orbital period of 1.2730988 ± 0.0000029 days, and has an equilibrium temperature of 1311 ± 28 K. TOI-238 c has a radius of 2.18 ± 0.18 R⊕ and a mass of 6.7 ± 1.1 M⊕. It orbits at a separation of 0.0749 ± 0.0013 au of its host star, with an orbital period of 8.465652 ± 0.000031 days, and has an equilibrium temperature of 696 ± 15 K. The mass and radius of planet b are fully consistent with an Earth-like composition, making it a likely rocky super-Earth. Planet c could be a water-rich planet or a rocky planet with a small H-He atmosphere.

The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity* * HD 26965 is also known as 40 Eridani A, which is the host star of the planet Vulcan in the Star Trek universe.

We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF “NEID” precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday “lag” between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.

Mutual occurrence ratio of planets – I. New clues to reveal origins of hot and warm Jupiter from the RV sample

ABSTRACT Many studies have analysed planetary occurrence rates and their dependence on the host’s properties to provide clues to planet formation, but few have focused on the mutual occurrence ratio of different kinds of planets. Such relations reveal whether and how one type of planet evolves into another, e.g. from a cold Jupiter (CJ) to a warm Jupiter (WJ) or even hot Jupiter (HJ), and demonstrate how stellar properties impact the evolution history of planetary systems. We propose a new classification of giant planets, i.e. CJ, WJ, and HJ, according to their position relative to the snow line in the system. Then, we derive their occurrence rates (ηHJ, ηWJ, ηCJ) with the detection completeness of radial velocity (RV) surveys (HARPS and CORALIE) considered. Finally, we analyse the correlation between the mutual occurrence ratios, i.e. ηCJ/ηWJ, ηCJ/ηHJ, or ηWJ/ηHJ, and various stellar properties, e.g. effective temperature Teff. Our results show that the ηHJ, ηWJ, and ηCJ are increasing with the increasing Teff when Teff ∈ (4600, 6600] K. Furthermore, the mutual occurrence ratio between CJ and WJ, i.e. ηCJ/ηWJ, shows a decreasing trend with the increasing Teff. But, both ηCJ/ηHJ and ηWJ/ηHJ are increasing when the Teff increases. Further consistency tests reveal that the formation processes of WJ and HJ may be dominated by orbital change mechanisms rather than the in situ model. However, unlike WJ, which favours gentle disc migration, HJ favours a more violent mechanism that requires further investigation.

Revised Architecture and Two New Super-Earths in the HD 134606 Planetary System

Multiplanet 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 for searches for more distant planetary orbits. This work provides a significantly revised architecture for the multiplanet system HD 134606 using both HARPS and UCLES RVs. We confirm the presence of previously reported planets b, c, and d with periods of 12.0897−0.0018+0.0019 , 58.947−0.054+0.056 , and 958.7−5.9+6.3 days and masses of 9.14−0.63+0.65 , 11.0 ± 1, and 44.5 ± 2.9 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 of 4.31943−0.00068+0.00075 and 26.9−0.017+0.019 days and masses of 2.31−0.35+0.36 and 5.52−0.73+0.74 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 massive companion with a very long orbital period. 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 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.

Detection Sensitivities from the Anglo-Australian Planet Search

Our understanding of the occurrence rates and demographics of long-period planets depends critically on data from legacy radial-velocity surveys with the long-term sensitivity to Jupiter-like planets in Jupiter-like orbits. A recent paper presented such an analysis for giant planets (m sin i > 0.3 M J) from the now-completed Anglo-Australian Planet Search. In this work, I deliver the detailed detection sensitivities for all 203 individual stars in that study, as a function of orbital periods from 100 to 6000 days. We present these data as a companion to Wittenmyer et al.

Inferring Stellar Parameters from Iodine-imprinted Keck/HIRES Spectra with Machine Learning

The properties of exoplanet host stars are traditionally characterized through a detailed forward-modeling analysis of high-resolution spectra. However, many exoplanet radial velocity surveys employ iodine-cell-calibrated spectrographs, such that the vast majority of spectra obtained include an imprinted forest of iodine absorption lines. For surveys that use iodine cells, iodine-free “template” spectra must be separately obtained for precise stellar characterization. These template spectra often require extensive additional observing time to obtain, and they are not always feasible to obtain for faint stars. In this paper, we demonstrate that machine-learning methods can be applied to infer stellar parameters and chemical abundances from iodine-imprinted spectra with high accuracy and precision. The methods presented in this work are broadly applicable to any iodine-cell-calibrated spectrograph. We make publicly available our spectroscopic pipeline, the Cannon HIRES Iodine Pipeline, which derives stellar parameters and 15 chemical abundances from iodine-imprinted spectra of FGK stars and which has been set up for ease of use with Keck/HIRES spectra. Our proof of concept offers an efficient new avenue to rapidly estimate a large number of stellar parameters even in the absence of an iodine-free template spectrum.

The Influence of Cold Jupiters in the Formation of Close-in Planets. I. Planetesimal Transport

The formation of a cold Jupiter (CJ) is expected to quench the influx of pebbles and the migration of cores interior to its orbit, thus limiting the efficiency of rocky planet formation either by pebble accretion and/or orbital migration. Observations, however, show that the presence of outer CJs (>1 au and ≳0.3M Jup) correlates with the presence of inner super-Earths (at <1 au). This observation may simply be a result of an enhanced initial reservoir of solids in the nebula required to form a CJ or a yet-to-be-determined mechanism assisted by the presence of the CJ. In this work, we focus on the latter alternative and study the orbital transport of planetesimals interior to a slightly eccentric (∼0.05) CJ subject to the gravity and drag from a viscously evolving gaseous disk. We find that a secular resonance sweeping inward through the disk gradually transports rings of planetesimals when their drag-assisted orbital decay is faster than the speed of the resonance scanning. This snowplow-like process leads to large concentration (boosted by a factor of ∼10–100) of size-segregated planetesimal rings with aligned apsidal lines, making their expected collisions less destructive, due to their reduced velocity dispersion. This process is efficient for a wide range of α-disk models (and thus disk lifetimes) and Jovian masses, peaking for values ∼1–5M Jup, which are typical of observed CJs in radial velocity surveys. Overall, our work highlights the major role that the disk's gravity may have on the orbital redistribution of planetesimals, depicting a novel avenue by which CJs may enhance the formation of inner planetary systems, including super-Earths and perhaps even warm and hot Jupiters.

The California Legacy Survey. IV. Lonely, Poor, and Eccentric: A Comparison between Solitary and Neighborly Gas Giants

We compare systems with single giant planets to systems with multiple giant planets using a catalog of planets from a high-precision radial velocity survey of FGKM stars. Our comparison focuses on orbital properties, planet masses, and host-star properties. We use hierarchical methods to model the orbital eccentricity distributions of giant singles and giant multiples, and find that the distributions are distinct. The multiple giant planets typically have moderate eccentricities and their eccentricity distribution extends to e = 0.47 (90th percentile), while the single giant planets have a pileup of nearly circular orbits and a long tail that extends to e = 0.77. We determine that the stellar hosts of multiple giants are distinctly more metal rich than the hosts of solitary giants, with respective mean metallicities of 0.228 ± 0.027 versus 0.129 ± 0.019 dex. We measure the distinct occurrence distributions of single and multiple giants with respect to orbital separation, and find that single gas giants have a ∼2.3σ significant hot Jupiter (a < 0.06) pileup not seen among multigiant systems. We find that the median mass () of giants in multiples is nearly double that of single giants (1.71 M J versus 0.92 M J). We find that giant planets in the same system have correlated masses, analogous to the “peas in a pod” effect seen among less-massive planets.

Exploring the brown dwarf desert with precision radial velocities and Gaia DR3 astrometric orbits

Context. The observed scarcity of brown dwarfs in close orbits (within 10 au) around solar-type stars has posed significant questions about the origins of these substellar companions. These questions not only pertain to brown dwarfs but also impact our broader understanding of planetary formation processes. However, to resolve these formation mechanisms, accurate observational constraints are essential. Notably, most of the brown dwarfs have been discovered by radial velocity surveys, but this method introduces uncertainties due to its inability to determine the orbital inclination, leaving the true mass – and thus their true nature – unresolved. This highlights the crucial role of astrometric data, helping us distinguish between genuine brown dwarfs and stars. Aims. This study aims to refine the mass estimates of massive companions to solar-type stars, mostly discovered through radial velocity measurements and subsequently validated using Gαìα DR3 astrometry, to gain a clearer understanding of their true mass and occurrence rates. Methods. We selected a sample of 31 sources with substellar companion candidates validated by Gaia Data Release (DR3) and with available radial velocities. Using the Gaia DR3 solutions as prior information, we performed an MCMC fit with the available radial velocity measurements to integrate these two sources of data and thus obtain an estimate of their true mass. Results. Combining radial velocity measurements with Gaia DR3 data led to more precise mass estimations, leading us to reclassify several systems initially labeled as brown dwarfs as low-mass stars. Out of the 32 analyzed companions, 13 have been determined to be stars, 17 are substellar, and two have inconclusive results with the current data. Importantly, using these updated masses, we reevaluated the occurrence rate of brown dwarf companions (13–80 MJup) on close orbits (&lt;10 au) in the CORALIE sample, determining a tentative occurrence rate of 0.8−0.2+0.3%.

The evolution of hot Jupiters revealed by the age distribution of their host stars.

The unexpected discovery of hot Jupiters challenged the classical theory of planet formation inspired by our solar system. Until now, the origin and evolution of hot Jupiters are still uncertain. Determining their age distribution and temporal evolution can provide more clues into the mechanism of their formation and subsequent evolution. Using a sample of 383 giant planets around Sun-like stars collected from the kinematic catalogs of the Planets Across Space and Time project, we find that hot Jupiters are preferentially hosted by relatively younger stars in the Galactic thin disk. We subsequently find that the frequency of hot Jupiters declines with age as [Formula: see text]. In contrast, the frequency of warm/cold Jupiters shows no significant dependence on age. Such a trend is expected from the tidal evolution of hot Jupiters' orbits, and our result offers supporting evidence using a large sample. We also perform a joint analysis on the planet frequencies in the stellar age-metallicity plane. The result suggests that the frequencies of hot Jupiters and warm/cold Jupiters, after removing the age dependence are both correlated with stellar metallicities as [Formula: see text] and [Formula: see text], respectively. Moreover, we show that the above correlations can explain the bulk of the discrepancy in hot Jupiter frequencies inferred from the transit and radial velocity (RV) surveys, given that RV targets tend to be more metal-rich and younger than transits.

Jupiter-like planets might be common in a low-density environment

Radial velocity surveys suggest that the Solar System may be unusual and that Jupiter-like planets have a frequency < 20% around solar-type stars. However, they may be much more common in one of the closest associations in the solar neighbourhood. Young moving stellar groups are the best targets for direct imaging of exoplanets and four massive Jupiter-like planets have been already discovered in the nearby young β Pic Moving Group (BPMG) via high-contrast imaging, and four others were suggested via high precision astrometry by the European Space Agency’s Gaia satellite. Here we analyze 30 stars in BPMG and show that 20 of them might potentially host a Jupiter-like planet as their orbits would be stable. Considering incompleteness in observations, our results suggest that Jupiter-like planets may be more common than previously found. The next Gaia data release will likely confirm our prediction.

Forming Gas Giants around a Range of Protostellar M-dwarfs by Gas Disk Gravitational Instability

Recent discoveries of gas giant exoplanets around M-dwarfs from transiting and radial velocity surveys are difficult to explain with core-accretion models. We present here a homogeneous suite of 162 models of gravitationally unstable gaseous disks. These models represent an existence proof for gas giants more massive than 0.1 Jupiter masses to form by the gas disk gravitational instability (GDGI) mechanism around M-dwarfs for comparison with observed exoplanet demographics and protoplanetary disk mass estimates for M-dwarf stars. We use the Enzo 2.6 adaptive mesh refinement (AMR) 3D hydrodynamics code to follow the formation and initial orbital evolution of gas giant protoplanets in gravitationally unstable gaseous disks in orbit around M-dwarfs with stellar masses ranging from 0.1 M ⊙ to 0.5 M ⊙. The gas disk masses are varied over a range from disks that are too low in mass to form gas giants rapidly to those where numerous gas giants are formed, therefore revealing the critical disk mass necessary for gas giants to form by the GDGI mechanism around M-dwarfs. The disk masses vary from 0.01 M ⊙ to 0.05 M ⊙ while the disk to star mass ratios explored the range from 0.04 to 0.3. The models have varied initial outer disk temperatures (10–60 K) and varied levels of AMR grid spatial resolution, producing a sample of expected gas giant protoplanets for each star mass. Broadly speaking, disk masses of at least 0.02 M ⊙ are needed for the GDGI mechanism to form gas giant protoplanets around M-dwarfs.

Radial distribution of giant exoplanets at Solar System scales

Aims. Giant planets play a major role in multiple planetary systems. Knowing their demographics is important to test their overall impact on the formation of planetary systems. It is also important to test their formation processes. Recently, three radial velocity (RV) surveys have established radial distributions of giant planets. All show a steep increase up to 1–3 au, and two suggest a decrease beyond that. Methods. We aim to understand the limitations associated with the characterization of long-period giant RV planets, and to estimate their impact on the radial distribution of these planets. Results. We revisit the results obtained by two major surveys that derived such radial distributions, using the RV data available at the time of the surveys as well as, whenever possible, new data. Conclusions. We show that the radial distributions published beyond (5–8 au) are not secure. More precisely, the decrease in the radial distribution beyond the peak at 1–3 au is not confirmed.