المؤلفون: Egger, J. A., Osborn, H. P., Kubyshkina, D., Mordasini, C., Alibert, Y., Günther, M. N., Lendl, M., Brandeker, A., Heitzmann, A., Leleu, A., Damasso, M., Bonfanti, A., Wilson, T. G., Sousa, S. G., Haldemann, J., Delrez, L., Hooton, M. J., Zingales, T., Luque, R., Alonso, R., Asquier, J., Bárczy, T., Navascues, D. Barrado, Barros, S. C. C., Baumjohann, W., Benz, W., Billot, N., Borsato, L., Broeg, C., Buder, M., Castro-González, A., Cameron, A. Collier, Correia, A. C. M., Cortes, D., Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Deline, A., Demangeon, O. D. S., Demory, B. -O., Derekas, A., Edwards, B., Ehrenreich, D., Erikson, A., Fortier, A., Fossati, L., Fridlund, M., Gandolfi, D., Gazeas, K., Gillon, M., Güdel, M., Helling, Ch., Isaak, K. G., Kiss, L. L., Korth, J., Lam, K. W. F., Laskar, J., Lavie, B., Etangs, A. Lecavelier des, Lovis, C., Luntzer, A., Magrin, D., Maxted, P. F. L., Merín, B., Munari, M., Nascimbeni, V., Olofsson, G., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piazza, D., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Rodrigues, J., Santos, N. C., Scandariato, G., Ségransan, D., Simon, A. E., Smith, A. M. S., Stalport, M., Sulis, S., Szabó, Gy. M., Udry, S., Van Grootel, V., Venturini, J., Villaver, E., Walton, N. A.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: Multiplanetary systems spanning the radius valley are ideal testing grounds for exploring the proposed explanations for the observed bimodality in the radius distribution of close-in exoplanets. One such system is HIP 29442 (TOI-469), an evolved K0V star hosting two super-Earths and a sub-Neptune. We observe HIP 29442 with CHEOPS for a total of 9.6 days, which we model jointly with 2 sectors of TESS data to derive planetary radii of $3.410\pm0.046$, $1.551\pm0.045$ and $1.538\pm0.049$ R$_\oplus$ for planets b, c and d, which orbit HIP 29442 with periods of 13.6, 3.5 and 6.4 days. For planet d, this value deviates by more than 3 sigma from the median value reported in the discovery paper, leading us to conclude that caution is required when using TESS photometry to determine the radii of small planets with low per-transit S/N and large gaps between observations. Given the high precision of these new radii, combining them with published RVs from ESPRESSO and HIRES provides us with ideal conditions to investigate the internal structure and formation pathways of the planets in the system. We introduce the publicly available code plaNETic, a fast and robust neural network-based Bayesian internal structure modelling framework. We then apply hydrodynamic models to explore the upper atmospheric properties of these inferred structures. Finally, we identify planetary system analogues in a synthetic population generated with the Bern model for planet formation and evolution. Based on this analysis, we find that the planets likely formed on opposing sides of the water iceline from a protoplanetary disk with an intermediate solid mass. We finally report that the observed parameters of the HIP 29442 system are compatible with both a scenario where the second peak in the bimodal radius distribution corresponds to sub-Neptunes with a pure H/He envelope as well as a scenario with water-rich sub-Neptunes.
Comment: 30 pages, 17 figures, accepted for publication in A&A

URL الوصول: http://arxiv.org/abs/2406.18653

المؤلفون: Sulis, S., Borsato, L., Grouffal, S., Osborn, H. P., Santerne, A., Brandeker, A., Günther, M. N., Heitzmann, A., Lendl, M., Fridlund, M., Gandolfi, D., Alibert, Y., Alonso, R., Bárczy, T., Navascues, D. Barrado, Barros, S. C., Baumjohann, W., Beck, T., Benz, W., Bergomi, M., Billot, N., Bonfanti, A., Broeg, C., Cameron, A. Collier, van Damme, C. Corral, Correia, A. C. M., Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Deline, A., Delrez, L., Demangeon, O. D. S., Demory, B. -O., Derekas, A., Edwards, B., Ehrenreich, D., Erikson, A., Fortier, A., Fossati, L., Gazeas, K., Gillon, M., Güdel, M., Helling, Ch., Hoyer, S., Isaak, K. G., Kiss, L., Korth, J., Lam, K. W. F., Laskar, J., Etangs, A. Lecavelier des, Magrin, D., Maxted, P. F. L., Mordasini, C., Nascimbeni, V., Olofsson, G., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piazza, D., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Santos, N. C., Scandariato, G., Ségransan, D., Simon, A. E., Smith, A. M. S., Sousa, S. G., Stalport, M., Steinberger, M., Szabó, M. Gy., Tuson, A., Udry, S., Ulmer-Moll, S., Van Grootel, V., Venturini, J., Villaver, E., Walton, N. A., Wilson, T. G., Wolter, D., Zingales, T.

المصدر: A&A 686, L18 (2024)

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: HIP 41378 d is a long-period planet that has only been observed to transit twice, three years apart, with K2. According to stability considerations and a partial detection of the Rossiter-McLaughlin effect, $P_\mathrm{d} = 278.36$ d has been determined to be the most likely orbital period. We targeted HIP 41378 d with CHEOPS at the predicted transit timing based on $P_\mathrm{d}= 278.36$ d, but the observations show no transit. We find that large ($>22.4$ hours) transit timing variations (TTVs) could explain this non-detection during the CHEOPS observation window. We also investigated the possibility of an incorrect orbital solution, which would have major implications for our knowledge of this system. If $P_\mathrm{d} \neq 278.36$ d, the periods that minimize the eccentricity would be $101.22$ d and $371.14$ d. The shortest orbital period will be tested by TESS, which will observe HIP 41378 in Sector 88 starting in January 2025. Our study shows the importance of a mission like CHEOPS, which today is the only mission able to make long observations (i.e., from space) to track the ephemeris of long-period planets possibly affected by large TTVs.
Comment: Accepted for publication in Astronomy and Astrophysics

URL الوصول: http://arxiv.org/abs/2405.20077

المؤلفون: Leleu, A., Delisle, J. -B., Delrez, L., Bryant, E. M., Brandeker, A., Osborn, H. P., Hara, N., Wilson, T. G., Billot, N., Lendl, M., Ehrenreich, D., Chakraborty, H., Günther, M. N., Hooton, M. J., Alibert, Y., Alonso, R., Alves, D. R., Anderson, D. R., Apergis, I., Armstrong, D., Bárczy, T., Navascues, D. Barrado, Barros, S. C. C., Battley, M. P., Baumjohann, W., Bayliss, D., Beck, T., Benz, W., Borsato, L., Broeg, C., Burleigh, M. R., Casewell, S. L., Cameron, A. Collier, Correia, A. C. M., Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Deline, A., Demangeon, O. D. S., Demory, B. -O., Derekas, A., Edwards, B., Erikson, A., Fortier, A., Fossati, L., Fridlund, M., Gandolfi, D., Gazeas, K., Gillen, E., Gillon, M., Goad, M. R., Güdel, M., Hawthorn, F., Heitzmann, A., Helling, Ch., Isaak, K. G., Jenkins, J. S., Jenkins, J. M., Kendall, A., Kiss, L. L., Korth, J., Lam, K. W. F., Laskar, J., Latham, D. W., Etangs, A. Lecavelier des, Magrin, D., Maxted, P. F. L., McCormac, J., Mordasini, C., Moyano, M., Nascimbeni, V., Olofsson, G., Osborn, A., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Ricker, G., Saha, S., Santos, N. C., Scandariato, G., Seager, S., Ségransan, D., Simon, A. E., Smith, A. M. S., Sousa, S. G., Stalport, M., Sulis, S., Szabó, Gy. M., Udry, S., Van Grootel, V., Vanderspek, R., Venturini, J., Villaver, E., Vinés, J. I., Walton, N. A., West, R. G., Winn, J., Zivave, T.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from 1.2 to 2.9 earth radius and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. The fine-tuning and fragility of such orbital configurations ensure that no significant scattering or collision event has taken place since the formation and migration of the planets in the protoplanetary disc, hence providing important anchors for planet formation models. We aim to improve the characterisation of the architecture of this key system, and in particular the masses and radii of its planets. In addition, since this system is one of the few resonant chains that can be characterised by both photometry and radial velocities, we aim to use it as a test bench for the robustness of the planetary mass determination with each technique. We perform a global analysis of all available photometry and radial velocity. We also try different sets of priors on the masses and eccentricity, as well as different stellar activity models, to study their effects on the masses estimated by each method. We show how stellar activity is preventing us from obtaining a robust mass estimation for the three outer planets using radial velocity data alone. We also show that our joint photo-dynamical and radial velocity analysis resulted in a robust mass determination for planets c to g, with precision of 12% for the mass of planet c, and better than 10% for planets d to g. The new precisions on the radii range from 2 to 3%. The understanding of this synergy between photometric and radial velocity measurements will be valuable during the PLATO mission. We also show that TOI-178 is indeed currently locked in the resonant configuration, librating around an equilibrium of the chain.

URL الوصول: http://arxiv.org/abs/2405.13732

المؤلفون: Battley, M. P., Collins, K. A., Ulmer-Moll, S., Quinn, S. N., Lendl, M., Gill, S., Brahm, R., Hobson, M. J., Osborn, H. P., Deline, A., Faria, J. P., Claringbold, A. B., Chakraborty, H., Stassun, K. G., Hellier, C., Alves, D. R., Ziegler, C., Anderson, D. R., Apergis, I., Armstrong, D. J., Bayliss, D., Beletsky, Y., Bieryla, A., Bouchy, F., Burleigh, M. R., Butler, R. P., Casewell, S. L., Christiansen, J. L., Crane, J. D., Dalba, P. A., Daylan, T., Figueira, P., Gillen, E., Goad, M. R., Günther, M. N., Henderson, B. A., Henning, T., Jenkins, J. S., Jordán, A., Kanodia, S., Kendall, A., Kunimoto, M., Latham, D. W., Levine, A. M., McCormac, J., Moyano, M., Osborn, A., Osip, D., Pritchard, T. A., Psaridi, A., Rice, M., Rodriguez, J. E., Saha, S., Seager, S., Shectman, S. A., Smith, A. M. S., Teske, J. K., Ting, E. B., Udry, S., Vines, J. I., Watson, C. A., West, R. G., Wheatley, P. J., Winn, J. N., Yee, S. W., Zhao, Y.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: Long-period transiting exoplanets bridge the gap between the bulk of transit- and Doppler-based exoplanet discoveries, providing key insights into the formation and evolution of planetary systems. The wider separation between these planets and their host stars results in the exoplanets typically experiencing less radiation from their host stars; hence, they should maintain more of their original atmospheres, which can be probed during transit via transmission spectroscopy. Although the known population of long-period transiting exoplanets is relatively sparse, surveys performed by the Transiting Exoplanet Survey Satellite (TESS) and the Next Generation Transit Survey (NGTS) are now discovering new exoplanets to fill in this crucial region of the exoplanetary parameter space. This study presents the detection and characterisation of NGTS-30 b/TOI-4862 b, a new long-period transiting exoplanet detected by following up on a single-transit candidate found in the TESS mission. Through monitoring using a combination of photometric instruments (TESS, NGTS, and EulerCam) and spectroscopic instruments (CORALIE, FEROS, HARPS, and PFS), NGTS-30 b/TOI-4862 b was found to be a long-period (P = 98.29838 day) Jupiter-sized (0.928 RJ; 0.960 MJ) planet transiting a 1.1 Gyr old G-type star. With a moderate eccentricity of 0.294, its equilibrium temperature could be expected to vary from 274 K to 500 K over the course of its orbit. Through interior modelling, NGTS-30 b/TOI-4862 b was found to have a heavy element mass fraction of 0.23 and a heavy element enrichment (Zp/Z_star) of 20, making it metal-enriched compared to its host star. NGTS-30 b/TOI-4862 b is one of the youngest well-characterised long-period exoplanets found to date and will therefore be important in the quest to understanding the formation and evolution of exoplanets across the full range of orbital separations and ages.
Comment: 18 pages, 14 figures, accepted for publication in A&A

URL الوصول: http://arxiv.org/abs/2404.02974

المؤلفون: Rosário, N. M., Demangeon, O. D. S., Barros, S. C. C., Gandolfi, D., Egger, J. A., Serrano, L. M., Osborn, H. P., Beck, M., Benz, W., Florén, H. -G., Guterman, P., Wilson, T. G., Alibert, Y., Fossati, L., Hooton, M. J., Delrez, L., Santos, N. C., Sousa, S. G., Bonfanti, A., Salmon, S., Adibekyan, V., Nigioni, A., Venturini, J., Alonso, R., Anglada, G., Asquier, J., Bárczy, T., Navascues, D. Barrado, Barragán, O., Baumjohann, W., Beck, T., Billot, N., Biondi, F., Bonfils, X., Borsato, L., Brandeker, A., Broeg, C., Cessa, V., Charnoz, S., Cameron, A. Collier, Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Deline, A., Demory, B. -O., Ehrenreich, D., Erikson, A., Esposito, M., Fortier, A., Fridlund, M., Gillon, M., Güdel, M., Günther, M. N., Helling, Ch., Hoyer, S., Isaak, K. G., Kiss, L. L., Lam, K. W. F., Laskar, J., Etangs, A. Lecavelier des, Lendl, M., Luntzer, A., Magrin, D., Maxted, P. F. L., Mordasini, C., Nascimbeni, V., Olofsson, G., Osborne, H. L. M., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Scandariato, G., Ségransan, D., Simon, A. E., Smith, A. M. S., Stalport, M., Szabó, Gy. M., Thomas, N., Udry, S., Van Eylen, V., Van Grootel, V., Villaver, E., Walter, I., Walton, N. A.

المصدر: A&A 686, A282 (2024)

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: We aim to constrain the internal structure and composition of HD 15337 b and c, two short-period planets situated on opposite sides of the radius valley, using new transit photometry and radial velocity data. We acquire 6 new transit visits with the CHaracterising ExOPlanet Satellite (CHEOPS) and 32 new radial velocity measurements from the High Accuracy Radial Velocity Planet Searcher (HARPS) to improve the accuracy of the mass and radius estimates for both planets. We reanalyse light curves from TESS sectors 3 and 4 and analyse new data from sector 30, correcting for long-term stellar activity. Subsequently, we perform a joint fit of the TESS and CHEOPS light curves, and all available RV data from HARPS and the Planet Finder Spectrograph (PFS). Our model fits the planetary signals, the stellar activity signal and the instrumental decorrelation model for the CHEOPS data simultaneously. The stellar activity was modelled using a Gaussian-process regression on both the RV and activity indicators. We finally employ a Bayesian retrieval code to determine the internal composition and structure of the planets. We derive updated and highly precise parameters for the HD 15337 system. Our improved precision on the planetary parameters makes HD 15337 b one of the most precisely characterised rocky exoplanets, with radius and mass measurements achieving a precision better than 2\% and 7\%, respectively. We are able to improve the precision of the radius measurement of HD 15337 c to 3\%. Our results imply that the composition of HD 15337 b is predominantly rocky, while HD 15337 c exhibits a gas envelope with a mass of at least $0.01\ M_\oplus$.Our results lay the groundwork for future studies, which can further unravel the atmospheric evolution of these exoplanets and give new insights into their composition and formation history and the causes behind the radius gap.
Comment: 17 pages, including appendix

URL الوصول: http://arxiv.org/abs/2403.16621

المؤلفون: Orell-Miquel, J., Carleo, I., Murgas, F., Nowak, G., Palle, E., Luque, R., Masseron, T., Sanz-Forcada, J., Dragomir, D., Dalba, P. A., Tronsgaard, R., Wittrock, J., Kim, K., Stibbards, C., Collins, K. I., Plavchan, P., Howell, S. B., Furlan, E., Buchhave, L. A., Gnilka, C. L., Gupta, A. F., Henning, Th., Lester, K. V., Rodriguez, J. E., Scott, N. J., Osborn, H. P., Villanueva Jr., S., Seager, S., Winn, J. N., Jenkins, J. M., Vanderspek, R., Latham, D. W., Rowden, P., Watanabe, D., Torres, G., Burke, C. J., Daylan, T., Barclay, T., Twicken, J. D., Ricker, G. R.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: The Transiting Exoplanet Survey Satellite (TESS) provides a continuous suite of new planet candidates that need confirmation and precise mass determination from ground-based observatories. This is the case for the G-type star TOI-1710, which is known to host a transiting sub-Saturn planet ($\mathrm{M_p}=$28.3$\pm$4.7$\mathrm{M}_\oplus$) in a long-period orbit (P=24.28\,d). Here we combine archival SOPHIE and new and archival HARPS-N radial velocity data with newly available TESS data to refine the planetary parameters of the system and derive a new mass measurement for the transiting planet, taking into account the impact of the stellar activity on the mass measurement. We report for TOI-1710b a radius of $\mathrm{R_p}$$=$5.15$\pm$0.12$\mathrm{R}_\oplus$, a mass of $\mathrm{M_p}$$=$18.4$\pm$4.5$\mathrm{M}_\oplus$, and a mean bulk density of $\rho_{\rm p}$$=$0.73$\pm$0.18$\mathrm{g \, cm^{-3}}$, which are consistent at 1.2$\sigma$, 1.5$\sigma$, and 0.7$\sigma$, respectively, with previous measurements. Although there is not a significant difference in the final mass measurement, we needed to add a Gaussian process component to successfully fit the radial velocity dataset. This work illustrates that adding more measurements does not necessarily imply a better mass determination in terms of precision, even though they contribute to increasing our full understanding of the system. Furthermore, TOI-1710b joins an intriguing class of planets with radii in the range 4-8 $\mathrm{R}_\oplus$ that have no counterparts in the Solar System. A large gaseous envelope and a bright host star make TOI-1710b a very suitable candidate for follow-up atmospheric characterization.
Comment: Accepted for publication in A&A. 21 pages, 14 figures

URL الوصول: http://arxiv.org/abs/2401.13574

المؤلفون: Heidari, N., Boisse, I., Hara, N. C., Wilson, T. G., Kiefer, F., Hébrard, G., Philipot, F., Hoyer, S., Stassun, K. G., Henry, G. W., Santos, N. C., Acuña, L., Almasian, D., Arnold, L., Astudillo-Defru, N., Attia, O., Bonfils, X., Bouchy, F., Bourrier, V., Collet, B., Cortés-Zuleta, P., Carmona, A., Delfosse, X., Dalal, S., Deleuil, M., Demangeon, O. D. S., Díaz, R. F., Dumusque, X., Ehrenreich, D., Forveille, T., Hobson, M. J., Jenkins, J. S., Jenkins, J. M., Lagrange, A. M., Latham, D. W., Larue, P., Liu, J., Moutou, C., Mignon, L., Osborn, H. P., 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. G., Vines, J. I.

المصدر: A&A 681, A55 (2024)

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: 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 HD88986b, a potentially transiting sub-Neptune, possessing the longest orbital period among known transiting small planets (< 4 R$_{\oplus}$) with a precise mass measurement ($\sigma_M/M$ > 25%). Additionally, we identified the presence of a massive companion in a wider orbit around HD88986. Our analysis reveals that HD88986b, 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 HD88986b has a radius of 2.49$\pm$0.18 R$_{\oplus}$, a mass of 17.2$^{+4.0}_{-3.8}$ M$_{\oplus}$, and it orbits every 146.05$^{+0.43}_{-0.40}$ d around a subgiant HD88986 which is one of the closest and brightest exoplanet host stars (G2V type, R=1.543 $\pm$0.065 R$_{\odot}$, V=$6.47\pm 0.01$ mag, distance=33.37$\pm$0.04 pc). The nature of the outer, massive companion is still to be confirmed; a joint analysis of RVs, Hipparcos, and Gaia astrometric data shows that with a 3$\sigma$ confidence interval, its semi-major axis is between 16.7 and 38.8 au and its mass is between 68 and 284 M$_{Jup}$. HD88986b'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 HD88986b (460$\pm$8 K), thanks to its long orbital period, will open up exciting opportunities for future studies of cold atmosphere composition characterization.
Comment: 37 pages, accepted to be published in A&A

URL الوصول: http://arxiv.org/abs/2311.13513

المؤلفون: Damasso, M., Rodrigues, J., Castro-González, A., Lavie, B., Davoult, J., Osorio, M. R. Zapatero, Dou, J., Sousa, S. G., Owen, J. E., Sossi, P., Adibekyan, V., Osborn, H., Leinhardt, Z., Alibert, Y., Lovis, C., Mena, E. Delgado, Sozzetti, A., Barros, S. C. C., Bossini, D., Ziegler, C., Ciardi, D. R., Matthews, E. C., Carter, P. J., Lillo-Box, J., Mascareño, A. Suárez, Cristiani, S., Pepe, F., Rebolo, R., Santos, N. C., Prieto, C. Allende, Benatti, S., Bouchy, F., Briceño, C., Di Marcantonio, P., D'Odorico, V., Dumusque, X., Egger, J. A., Ehrenreich, D., Faria, J., Figueira, P., Santos, R. Génova, Gonzales, E. J., Hernández, J. I. González, Law, N., Curto, G. Lo, Mann, A. W., Martins, C. J. A. P., Mehner, A., Micela, G., Molaro, P., Nunes, N. J., Palle, E., Poretti, E., Schlieder, J. E., Udry, S.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: We followed-up with ESPRESSO the K0V star HIP 29442 (TOI-469), already known to host a validated sub-Neptune companion TOI-469.01. We aim to verify the planetary nature of TOI-469.01. We modelled radial velocity and photometric time series to measure the dynamical mass, radius, and ephemeris, and to characterise the internal structure and composition of TOI-469.01. We confirmed the planetary nature of TOI-469.01. Thanks to ESPRESSO we discovered two additional close-in companions. We also detected their low signal-to-noise transit signals in the TESS light curve. HIP 29442 is a compact multi-planet system, and the three planets have orbital periods $P_{\rm orb, b}=13.63083\pm0.00003$, $P_{\rm orb, c}=3.53796\pm0.00003$, and $P_{\rm orb, d}=6.42975^{+0.00009}_{-0.00010}$ days, and we measured their masses with high precision: $m_{\rm p, b}=9.6\pm0.8~M_{\oplus}$, $m_{\rm p, c}=4.5\pm0.3~M_{\oplus}$, and $m_{\rm p, d}=5.1\pm0.4~M_{\oplus}$. We measured radii and bulk densities of all the planets (the 3$\sigma$ confidence intervals are shown in parenthesis): $R_{\rm p, b}=3.48^{+0.07 (+0.19)}_{-0.08 (-0.28)} ~R_{\oplus}$ and $\rho_{\rm p, b}=1.3\pm0.2 (0.3) g~cm^{-3}$; $R_{\rm p, c}=1.58^{+0.10 (+0.30)}_{-0.11 (-0.34)}~R_{\oplus}$ and $\rho_{\rm p, c}=6.3^{+1.7 (+6.0)}_{-1.3 (-2.7)} g~cm^{-3}$; $R_{\rm p, d}=1.37\pm0.11^{(+0.32)}_{(-0.43)}~R_{\oplus}$ and $\rho_{\rm p, d}=11.0^{+3.4 (+21.0)}_{-2.4 (-6.3)} g~cm^{-3}$. We used the more conservative 3$\sigma$ confidence intervals for the radii as input to the interior structure modelling. We find that HIP 29442 $b$ appears as a typical sub-Neptune, likely surrounded by a gas layer of pure H-He with a mass of $0.27^{+0.24}_{-0.17} M_{\oplus}$ and a thickness of $1.4\pm0.5 R_{\oplus}$. For the innermost companions HIP 29442 $c$ HIP 29442 $d$, the model supports an Earth-like composition.
Comment: Accepted for publication on A&A

URL الوصول: http://arxiv.org/abs/2308.13310

المؤلفون: Garai, Z., Osborn, H. P., Gandolfi, D., Brandeker, A., Sousa, S. G., Lendl, M., Bekkelien, A., Broeg, C., Cameron, A. Collier, Egger, J. A., Hooton, M. J., Alibert, Y., Delrez, L., Fossati, L., Salmon, S., Wilson, T. G., Bonfanti, A., Tuson, A., Ulmer-Moll, S., Serrano, L. M., Borsato, L., Alonso, R., Anglada, G., Asquier, J., Navascues, D. Barrado y, Barros, S. C. C., Bárczy, T., Baumjohann, W., Beck, M., Beck, T., Benz, W., Billot, N., Biondi, F., Bonfils, X., Buder, M., Cabrera, J., Cessa, V., Charnoz, S., Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Demangeon, O. D. S., Demory, B. -O., Ehrenreich, D., Erikson, A., Van Eylen, V., Fortier, A., Fridlund, M., Gillon, M., Van Grootel, V., Güdel, M., Günther, M. N., Hoyer, S., Isaak, K. G., Kiss, L. L., Kristiansen, M. H., Laskar, J., Etangs, A. Lecavelier des, Lovis, C., Luntzer, A., Magrin, D., Maxted, P. F. L., Mordasini, C., Nascimbeni, V., Olofsson, G., Ottensamer, R., Pagano, I., Pallé, E., Peter, G., Piotto, G., Pollacco, D., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Santos, N. C., Scandariato, G., Ségransan, D., Simon, A. E., Smith, A. M. S., Steller, M., Szabó, Gy. M., Thomas, N., Udry, S., Venturini, J., Walton, N.

المصدر: A&A 674, A44 (2023)

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period planets in these systems often escape detection. HD 22946 is a bright star around which 3 transiting planets were identified via TESS photometry, but the true orbital period of the outermost planet d was unknown until now. We aim to use CHEOPS to uncover the true orbital period of HD 22946d and to refine the orbital and planetary properties of the system, especially the radii of the planets. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS. We identified 2 transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO radial velocity data. Finally, a combined model was fitted to the entire dataset. We successfully determined the true orbital period of the planet d to be 47.42489 $\pm$ 0.00011 d, and derived precise radii of the planets in the system, namely 1.362 $\pm$ 0.040 R$_\oplus$, 2.328 $\pm$ 0.039 R$_\oplus$, and 2.607 $\pm$ 0.060 R$_\oplus$ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3$\sigma$ upper limits for these respective planet masses, which are 13.71 M$_\oplus$, 9.72 M$_\oplus$, and 26.57 M$_\oplus$. We estimated that another 48 ESPRESSO radial velocities are needed to measure the predicted masses of all planets in HD 22946. Planet c appears to be a promising target for future atmospheric characterisation. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and internal structure.

URL الوصول: http://arxiv.org/abs/2306.04468

المؤلفون: Ulmer-Moll, S., Osborn, H. P., Tuson, A., Egger, J. A., Lendl, M., Maxted, P., Bekkelien, A., Simon, A. E., Olofsson, G., Adibekyan, V., Alibert, Y., Bonfanti, A., Bouchy, F., Brandeker, A., Fridlund, M., Gandolfi, D., Mordasini, C., Persson, C. M., Salmon, S., Serrano, L. M., Sousa, S. G., Wilson, T. G., Rieder, M., Hasiba, J., Asquier, J., Sicilia, D., Walter, I., Alonso, R., Anglada, G., Navascues, D. Barrado y, Barros, S. C. C., Baumjohann, W., Beck, M., Beck, T., Benz, W., Billot, N., Bonfils, X., Borsato, L., Broeg, C., Bárczy, T., Cabrera, J., Charnoz, S., Cointepas, M., Cameron, A. Collier, Csizmadia, Sz., Cubillos, P. E., Davies, M. B., Deleuil, M., Deline, A., Delrez, L., Demangeon, O. D. S., Demory, B. -O., Dumusque, X., Ehrenreich, D., Eisner, N. L., Erikson, A., Fortier, A., Fossati, L., Gillon, M., Grieves, N., Güdel, M., Hagelberg, J., Helled, R., Hoyer, S., Isaak, K. G., Kiss, L. L., Laskar, J., Etangs, A. Lecavelier des, Lovis, C., Magrin, D., Nascimbeni, V., Otegi, J., Ottensammer, R., Pagano, I., Pallé, E., Peter, G., Piotto, G., Pollacco, D., Psaridi, A., Queloz, D., Ragazzoni, R., Rando, N., Rauer, H., Ribas, I., Santos, N. C., Scandariato, G., Smith, A. M. S., Steller, M., Szabó, G. M., Ségransan, D., Thomas, N., Udry, S., Van Grootel, V., Venturini, J., Walton, N. A.

مصطلحات موضوعية: Astrophysics - Earth and Planetary Astrophysics

الوصف: A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and for shedding light on the formation and evolution of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are unaltered by intense stellar irradiation and tidal effects. We identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as duo-transit events. To solve the orbital periods of TESS duo-transit candidates, we use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. We also collect spectroscopic observations with CORALIE and HARPS in order to confirm the planetary nature and measure the mass of the candidates. We report the discovery of a warm transiting Neptune-mass planet orbiting TOI-5678. After four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet. TOI-5678 b has a mass of 20 (+-4) Me and a radius of 4.91 (+-0.08 Re) . Using interior structure modeling, we find that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2 (+1.7, -1.3) Me. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar insolation (11 Se). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars are suitable targets to study the atmospheric composition of cooler gas giants.
Comment: 17 pages, 10 figures, accepted to A&A

URL الوصول: http://arxiv.org/abs/2306.04295