Dr. Astudillo-Defru, Nicola

2024, Dr. Astudillo-Defru, Nicola, Cointepas, M., Bouchy, F., Almenara, J., Bonfils, X., Knierim, H., Stalport, M., Mignon, L., Grieves, N., Bean, J., Brady, M., Burt, J., Canto-Martins, B., Collins, K., Collins, K., Delfosse, X., de Medeiros, J., Demory, B., Dorn, C., Forveille, T., Fukui, A., Gan, T., Gómez-Maqueo-Chew, Y., Halverson, S., Helled, R., Helm, I., Hirano, T., Horne, K., Howell, S., Isogai, K., Kasper, D., Kawauchi, K., Livingston, J., Massey, B., Matson, R., Murgas, F., Narita, N., Palle, E., Relles, H., Sabin, L., Schanche, N., Schwarz, R., Seifahrt, A., Shporer, A., Stefansson, G., Sturmer, J., Tamura, M., Tan, T., Twicken, J., Watanabe, N., Wells, R., Wilkin, F., Ricker, G., Seager, S., Winn, J., Jenkins, J.

We present the detection of three exoplanets orbiting the early M dwarf TOI-663 (TIC 54962195; V = 13.7 mag, J = 10.4 mag, R★ = 0.512 ± 0.015 R⊙, M★ = 0.514 ± 0.012 M⊙, d = 64 pc). TOI-663 b, c, and d, with respective radii of 2.27 ± 0.10 R⊕, 2.26 ± 0.10 R⊕, and 1.92 ± 0.13 R⊕ and masses of 4.45 ± 0.65 M⊕, 3.65 ± 0.97 M⊕, and <5.2 M⊕ at 99%, are located just above the radius valley that separates rocky and volatile-rich exoplanets. The planet candidates are identified in two TESS sectors and are validated with ground-based photometric follow-up, precise radial-velocity measurements, and high-resolution imaging. We used the software package juliet to jointly model the photometric and radial-velocity datasets, with Gaussian processes applied to correct for systematics. The three planets discovered in the TOI-663 system are low-mass mini-Neptunes with radii significantly larger than those of rocky analogs, implying that volatiles, such as water, must predominate. In addition to this internal structure analysis, we also performed a dynamical analysis that confirmed the stability of the system. The three exoplanets in the TOI-663 system, similarly to other sub-Neptunes orbiting M dwarfs, have been found to have lower densities than planets of similar sizes orbiting stars of different spectral types.

2022, Dr. Astudillo-Defru, Nicola, Almenara, J., Bonfils, X., Forveille, T., Ciardi, D., Schwarz, R., Collins, K., Cointepas, M., Lund, M., Bouchy, F., Charbonneau, D., Díaz, R., Delfosse, X., Kidwell, R., Kunimoto, M., Latham, D., Lissauer, J., Murgas, F., Ricker, G., Seager, S., Vezie, M., Watanabe, D.

The Transiting Exoplanet Survey Satellite mission identified a deep and asymmetric transit-like signal with a periodicity of 4.5 days orbiting the M4 dwarf star TOI-3884. The signal has been confirmed by follow-up observations collected by the ExTrA facility and Las Cumbres Observatory Global Telescope, which reveal that the transit is chromatic. The light curves are well modelled by a host star having a large polar spot transited by a 6-RE planet. We validate the planet with seeing-limited photometry, high-resolution imaging, and radial velocities. TOI-3884 b, with a radius of 6.00 ± 0.18 RE, is the first sub-Saturn planet transiting a mid-M dwarf. Owing to the host star’s brightness and small size, it has one of the largest transmission spectroscopy metrics for this planet size and becomes a top target for atmospheric characterisation with the James Webb Space Telescope and ground-based telescopes.

2022, Gorrini, P., Dr. Astudillo-Defru, Nicola, Dreizler, S., Damasso, M., Díaz, R. F., Bonfils, X., Jeffers, S. V., Barnes, J. R., Del Sordo, F., Almenara, J.-M., Artigau, E., Bouchy, F., Charbonneau, D., Delfosse, X., Doyon, R., Figueira, P., Forveille, T., Haswell, C. A., López-González, M. J., Melo, C., Mennickent, R. E., Gaisné, G., Morales, N., Murgas, F., Pepe, F., Rodríguez, E., Santos, N. C., Tal-Or, L., Tsapras, Y., Udry, S.

Context. Gliese-832 (GJ 832) is an M2V star hosting a massive planet on a decade-long orbit, GJ 832b, discovered by radial velocity (RV). Later, a super Earth or mini-Neptune orbiting within the stellar habitable zone was reported (GJ 832c). The recently determined stellar rotation period (45.7±9.3 days) is close to the orbital period of putative planet c (35.68±0.03 days). Aims. Weaimtoconfirmor dismiss the planetary nature of the RV signature attributed to GJ 832c, by adding 119 new RV data points, new photometric data, and an analysis of the spectroscopic stellar activity indicators. Additionally, we update the orbital parameters of the planetary system and search for additional signals. Methods. We performed a frequency content analysis of the RVs to search for periodic and stable signals. Radial velocity time series were modelled with Keplerians and Gaussian process (GP) regressions alongside activity indicators to subsequently compare them within a Bayesian framework. Results. We updated the stellar rotational period of GJ 832 from activity indicators, obtaining 37.5 +1.4 −1.5 days, improving the precision by a factor of 6. The new photometric data are in agreement with this value. We detected an RV signal near 18 days (FAP < 4.6%), which is half of the stellar rotation period. Two Keplerians alone fail at modelling GJ 832b and a second planet with a 35-day orbital period. Moreover, the Bayesian evidence from the GP analysis of the RV data with simultaneous activity indices prefers a model without a second Keplerian, therefore negating the existence of planet c.

2021, Dr. Astudillo-Defru, Nicola, Demangeon, O., Dalal, S., Hébrard, G., Nsamba, B., Kiefer, F., Camacho, J. D., Sahlmann, J., Arnold, L., Bonfils, X., Boisse, I., Bouchy, F., Bourrier, V., Campante, T., Delfosse, X., Deleuil, M., Díaz, R. F., Faria, J., Forveille, T., Hara, N., Heidari, N., Hobson, M., Lopez, T., Moutou, C., Rey, J., Santerne, A., Sousa, S., Santos, N., Strøm, P., Tsantaki, M., Udry, S.

Context. 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 10 m s−1, which is well within the reach of multiple instruments that have now been in operation for more than a decade. Aims. We take advantage of the ongoing radial velocity survey with the SOPHIEhigh-resolution spectrograph, which continues the search started by its predecessor ELODIEto 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 yr, we attempt the detection and confirmation of Keplerian signals. Results. We announce the discovery of six planets, one per system, with minimum masses in the range 4.8–8.3Mjupand orbital periods between 200 days and 10 yr. 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. Conclusions. 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 0.862−0.018+0.028. 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.

2024, Dr. Astudillo-Defru, Nicola, Almenara, J., Bonfils, X., Bryant, E., Jordán, A., Hébrard, G., Martioli, E., Correia, A., Cadieux, C., Arnold, L., Artigau, É., Bakos, G., Barros, S., Bayliss, D., Bouchy, F., Boué, G., Brahm, R., Carmona, A., Charbonneau, D., Ciardi, D., Cloutier, R., Cointepas, M., Cook, N., Cowan, N., Delfosse, X., Dias do Nascimento, J., Donati, J., Doyon, R., Forveille, T., Fouqué, P., Gaidos, E., Gilbert, E., da Silva, J., Hartman, J., Hesse, K., Hobson, M., Jenkins, J., Kiefer, F., Kostov, V., Laskar, J., Lendl, M., L’Heureux, A., Martins, J., Menou, K., Moutou, C., Murgas, F., Polanski, A. S., Rapetti, D., Sedaghati, E., Shang, H.

We report the discovery and characterisation of a giant transiting planet orbiting a nearby M3.5V dwarf (d = 80.4pc, G = 15.1 mag, K=11.2mag, R* = 0.358 ± 0.015 R⊙, M* = 0.340 ± 0.009 M⊙). Using the photometric time series from TESS sectors 10, 36, 46, and 63 and near-infrared spectrophotometry from ExTrA, we measured a planetary radius of 0.77 ± 0.03 RJ and an orbital period of 1.52 days. With high-resolution spectroscopy taken by the CFHT/SPIRou and ESO/ESPRESSO spectrographs, we refined the host star parameters ([Fe/H] = 0.27 ± 0.12) and measured the mass of the planet (0.273 ± 0.006 MJ). Based on these measurements, TOI-4860 b joins the small set of massive planets (>80 ME) found around mid to late M dwarfs (<0.4 R⊙), providing both an interesting challenge to planet formation theory and a favourable target for further atmospheric studies with transmission spectroscopy. We identified an additional signal in the radial velocity data that we attribute to an eccentric planet candidate (e = 0.66 ± 0.09) with an orbital period of 427 ± 7 days and a minimum mass of 1.66 ± 0.26 MJ, but additional data would be needed to confirm this.

2022, Dr. Astudillo-Defru, Nicola, Almenara, J., Bonfils, X., Otegi, J., Attia, O., Turbet, M., Collins, K., Polanski, A., Bourrier, V., Hellier, C., Ziegler, C., Bouchy, F., Briceno, C., Charbonneau, D., Cointepas, M., Collins, K., Crossfield, I., Delfosse, X., Diaz, R., Dorn, C., Doty, J., Forveille, T., Gaisné, G., Gan, T., Helled, R., Hesse, K., Jenkins, J., Jensen, E., Latham, D., Law, N., Mann, A., Mao, S., McLean, B., Murgas, F., Myers, G., Seager, S., Shporer, A., Tan, T. G., Twicken, J., Winn, J.

We report the detection of GJ 3090 b (TOI-177.01), a mini-Neptune on a 2.9-day orbit transiting a bright (K = 7.3 mag) M2 dwarf located at 22 pc. The planet was identified by the Transiting Exoplanet Survey Satellite and was confirmed with the High Accuracy Radial velocity Planet Searcher radial velocities. Seeing-limited photometry and speckle imaging rule out nearby eclipsing binaries. Additional transits were observed with the LCOGT, Spitzer, and ExTrA telescopes. We characterise the star to have a mass of 0.519 ± 0.013 M⊙ and a radius of 0.516 ± 0.016 R⊙. We modelled the transit light curves and radial velocity measurements and obtained a planetary mass of 3.34 ± 0.72 ME, a radius of 2.13 ± 0.11 RE, and a mean density of 1.89−0.45+0.52 g cm−3. The low density of the planet implies the presence of volatiles, and its radius and insolation place it immediately above the radius valley at the lower end of the mini-Neptune cluster. A coupled atmospheric and dynamical evolution analysis of the planet is inconsistent with a pure H–He atmosphere and favours a heavy mean molecular weight atmosphere. The transmission spectroscopy metric of 221−46+66 means that GJ 3090 b is the second or third most favorable mini-Neptune after GJ 1214 b whose atmosphere may be characterised. At almost half the mass of GJ 1214 b, GJ 3090 b is an excellent probe of the edge of the transition between super-Earths and mini-Neptunes. We identify an additional signal in the radial velocity data that we attribute to a planet candidate with an orbital period of 13 days and a mass of 17.1−3.2+8.9 ME, whose transits are not detected.

2021, Dr. Astudillo-Defru, Nicola, Murgas, F., Bonfils, X., Crossfield, I., Almenara, J., Livingston, J., Stassun, K., Korth, J., Orell-Miquel, J., Morello, G., Eastman, J., Lissauer, J., Kane, S., Morales, F., Werner, M., Gorjian, V., Benneke, B., Dragomir, D., Matthews, E., Howell, S., Ciardi, D., Gonzales, E., Matson, R., Beichman, C., Schlieder, J., Collins, K., Collins, K., Jensen, E., Evans, P., Pozuelos, F., Gillon, M., Jehin, E., Barkaoui, K., Artigau, E., Bouchy, F., Charbonneau, D., Delfosse, X., Díaz, R., Doyon, R., Figueira, P., Forveille, T., Lovis, C., Melo, C., Gaisné, G., Pepe, F., Santos, N., Ségransan, D., Udry, S., Goeke, R., Levine, A., Quintana, E., Guerrero, N., Mireles, I., Caldwell, D., Tenenbaum, P., Brasseur, C., Ricker, G., Vanderspek, R., Latham, D., Seager, S., Winn, J., Jenkins, J.

Context. The NASA mission TESS is currently doing an all-sky survey from space to detect transiting planets around bright stars. As part of the validation process, the most promising planet candidates need to be confirmed and characterized using follow-up observations. Aims. In this article, our aim is to confirm the planetary nature of the transiting planet candidate TOI-674b using spectroscopic and photometric observations. Methods. We use TESS, Spitzer, ground-based light curves, and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b. We perform a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. Results. We confirm and characterize TOI-674b, a low-density super-Neptune transiting a nearby M dwarf. The host star (TIC 158588995, V = 14.2 mag, J = 10.3 mag) is characterized by its M2V spectral type with M⋆ = 0.420 ± 0.010 M⊙, R⋆ = 0.420 ± 0.013 R⊙, and Teff = 3514 ± 57 K; it is located at a distance d = 46.16 ± 0.03 pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of 1.977143 ± 3 × 10−6 days, a planetary radius of 5.25 ± 0.17 R⊕, and a mass of 23.6 ± 3.3 M⊕ implying a mean density of ρp =0.91 ± 0.15 g cm−3. A non-circular orbit model fit delivers similar planetary mass and radius values within the uncertainties. Given the measured planetary radius and mass, TOI-674b is one of the largest and most massive super-Neptune class planets discovered around an M-type star to date. It is found in the Neptunian desert, and is a promising candidate for atmospheric characterization using the James Webb Space Telescope.

2024, Dr. Astudillo-Defru, Nicola, Heidari, N., Boisse, I., Hara, N., Wilson, T., Kiefer, F., Hébrard, G., Philipot, F., Hoyer, S., Stassun, K., Henry, G., Santos, N., Acuña, L., Almasian, D., Arnold, L., Attia, O., Bonfils, X., Bouchy, F., Bourrier, V., Collet, B., Cortés-Zuleta, P., Carmona, A., Delfosse, X., Dalal, S., Deleuil, M., Demangeon, O., Díaz, R., Dumusque, X., Ehrenreich, D., Forveille, T., Hobson, M., Jenkins, J., Jenkins, J., Lagrange, A., Latham, D., Larue, P., Liu, J., Moutou, C., Mignon, L., Osborn, H., Pepe, F., Rapetti, D., Rodrigues, J., Santerne, A., Segransan, D., Shporer, A., Sulis, S., Torres, G., Udry, S., Vakili, F., Vanderburg, A., Venot, O., Vivien, H., Vines, J.

Transiting planets with orbital periods longer than 40 d are extremely rare among the 5000+ planets discovered so far. The lack of discoveries of this population poses a challenge to research into planetary demographics, formation, and evolution. Here, we present the detection and characterization of HD 88986 b, a potentially transiting sub-Neptune, possessing the longest orbital period among known transiting small planets (<4 R⊕) with a precise mass measurement (σM/M > 25%). Additionally, we identified the presence of a massive companion in a wider orbit around HD 88986. To validate this discovery, we used a combination of more than 25 yr of extensive radial velocity (RV) measurements (441 SOPHIE data points, 31 ELODIE data points, and 34 HIRES data points), Gaia DR3 data, 21 yr of photometric observations with the automatic photoelectric telescope (APT), two sectors of TESS data, and a 7-day observation of CHEOPS. Our analysis reveals that HD 88986 b, based on two potential single transits on sector 21 and sector 48 which are both consistent with the predicted transit time from the RV model, is potentially transiting. The joint analysis of RV and photometric data show that HD 88986 b has a radius of 2.49 ± 0.18 R⊕, a mass of 17.2−3.8+4.0 M⊕, and it orbits every 146.05−0.40+0.43 d around a subgiant HD 88986 which is one of the closest and brightest exoplanet host stars (G2Vtype, R = 1.543 ± 0.065 R⊙, V = 6.47 ± 0.01 mag, distance = 33.37 ± 0.04 pc). The nature of the outer, massive companion is still to be confirmed; a joint analysis of RVs, HIPPARCOS, and Gaia astrometric data shows that with a 3σ confidence interval, its semi-major axis is between 16.7 and 38.8 au and its mass is between 68 and 284 MJup. HD 88986 b’s wide orbit suggests the planet did not undergo significant mass loss due to extreme-ultraviolet radiation from its host star. Therefore, it probably maintained its primordial composition, allowing us to probe its formation scenario. Furthermore, the cold nature of HD 88986 b (460 ± 8 K), thanks to its long orbital period, will open up exciting opportunities for future studies of cold atmosphere composition characterization. Moreover, the existence of a massive companion alongside HD 88986 b makes this system an interesting case study for understanding planetary formation and evolution.

2022, Heidari, N., Boisse, I., Orell-Miquel, J., Hébrard, G., Acuña, L., Hara, N. C., Lillo-Box, J., Eastman, J. D., Arnold, L., Dr. Astudillo-Defru, Nicola, Adibekyan, V., Bieryla, A., Bonfils, X., Bouchy, F., Barclay, T., Brasseur, C. E., Borgniet, S., Bourrier, V., Buchhave, L.

We present the discovery and characterization of a transiting sub-Neptune that orbits the nearby (28 pc) and bright (V = 8.37) K0V star HD 207897 (TOI-1611) with a 16.20-day period. This discovery is based on photometric measurements from the Transiting Exoplanet Survey Satellite mission and radial velocity (RV) observations from the SOPHIE, Automated Planet Finder, and HIRES high-precision spectrographs. We used EXOFASTv2 to model the parameters of the planet and its host star simultaneously, combining photometric and RV data to determine the planetary system parameters. We show that the planet has a radius of 2.50 ± 0.08 RE and a mass of either14.4 ± 1.6 ME or 15.9 ± 1.6 ME with nearly equal probability. The two solutions correspond to two possibilities for the stellar activity period. The density accordingly is either 5.1 ± 0.7 g cm−3 or 5.5+0.8−0.7 g cm−3, making it one of the relatively rare dense sub-Neptunes. The existence of this dense planet at only 0.12 AU from its host star is unusual in the currently observed sub-Neptune (2 < RE < 4) population. The most likely scenario is that this planet has migrated to its current position.

2021, Dr. Astudillo-Defru, Nicola, Dalal, S., Kiefer, F., Hébrard, G., Sahlmann, J., Sousa, S., Forveille, T., Delfosse, X., Arnold, L., Bonfils, X., Boisse, I., Bouchy, F., Bourrier, V., Brugger, B., Cortés-Zuleta, P., Deleuil, M., Demangeon, O., Díaz, R., Hara, N., Heidari, N., Hobson, J., Lopez, T., Lovis, C., Martioli, E., Mignon, L., Mousis, O., Moutou, C., Rey, J., Santerne, A., Santos, N., Ségransan, D., Strøm, P., Udry, S.

Distinguishing classes within substellar objects and understanding their formation and evolution need larger samples of substellar companions such as exoplanets, brown dwarfs, and low-mass stars. In this paper, we look for substellar companions using radial velocity surveys of FGK stars with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We assign here the radial velocity variations of 27 stars to their orbital motion induced by low-mass companions. We also constrained their plane-of-the-sky motion using HIPPARCOS and Gaia Data Release 1 measurements, which constrain the true masses of some of these companions. We report the detection and characterization of six cool Jupiters, three brown dwarf candidates, and 16 low-mass stellar companions. We additionally update the orbital parameters of the low-mass star HD 8291 B, and we conclude that the radial velocity variations of HD 204277 are likely due to stellar activity despite resembling the signal of a giant planet. One of the new giant planets, BD+631405 b, adds to the population of highly eccentric cool Jupiters, and it is presently the most massive member. Two of the cool Jupiter systems also exhibit signatures of an additional outer companion. The orbital periods of the new companions span 30 days to 11.5 yr, their masses 0.72 MJ–0.61 M, and their eccentricities 0.04–0.88. These discoveries probe the diversity of substellar objects and low-mass stars, which will help constrain the models of their formation and evolution.