학술논문
Astrometric detection of a Neptune-mass candidate planet in the nearest M-dwarf binary system GJ65 with VLTI/GRAVITY
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Working Paper
Author
GRAVITY Collaboration; Abuter, R.; Amorim, A.; Benisty, M.; Berger, J-P.; Bonnet, H.; Bourdarot, G.; Bourget, P.; Brandner, W.; Clénet, Y.; Davies, R.; Delplancke-Ströbele, F.; Dembet, R.; Drescher, A.; Eckart, A.; Eisenhauer, F.; Feuchtgruber, H.; Finger, G.; Förster-Schreiber, N. M.; Garcia, P.; Garcia-Lopez, R.; Gao, F.; Gendron, E.; Genzel, R.; Gillessen, S.; Hartl, M.; Haubois, X.; Haussmann, F.; Henning, T.; Hippler, S.; Horrobin, M.; Jochum, L.; Jocou, L.; Kaufer, A.; Kervella, P.; Lacour, S.; Lapeyrère, V.; Bouquin, J. B. Le; Ledoux, C.; Léna, P.; Lutz, D.; Mang, F.; Mérand, A.; More, N.; Nowak, M.; Ott, T.; Paumard, T.; Perraut, K.; Perrin, G.; Pfuhl, O.; Rabien, S.; Ribeiro, D. C.; Bordoni, M. Sadun; Shangguan, J.; Shimizu, T.; Stadler, J.; Straub, O.; Straubmeier, C.; Sturm, E.; Tacconi, L. J.; Tristram, K. R. W; Vincent, F.; von Fellenberg, S.; Widmann, F.; Wieprecht, E.; Woillez, J.; Yazici, S.; Zins, G.
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Subject
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Abstract
The detection of low-mass planets orbiting the nearest stars is a central stake of exoplanetary science, as they can be directly characterized much more easily than their distant counterparts. Here, we present the results of our long-term astrometric observations of the nearest binary M-dwarf Gliese 65 AB (GJ65), located at a distance of only 2.67 pc. We monitored the relative astrometry of the two components from 2016 to 2023 with the VLTI/GRAVITY interferometric instrument. We derived highly accurate orbital parameters for the stellar system, along with the dynamical masses of the two red dwarfs. The GRAVITY measurements exhibit a mean accuracy per epoch of 50-60 microarcseconds in 1.5h of observing time using the 1.8m Auxiliary Telescopes. The residuals of the two-body orbital fit enable us to search for the presence of companions orbiting one of the two stars (S-type orbit) through the reflex motion they imprint on the differential A-B astrometry. We detected a Neptune-mass candidate companion with an orbital period of p = 156 +/- 1 d and a mass of m = 36 +/- 7 Mearth. The best-fit orbit is within the dynamical stability region of the stellar pair. It has a low eccentricity, e = 0.1 - 0.3, and the planetary orbit plane has a moderate-to-high inclination of i > 30{\deg} with respect to the stellar pair, with further observations required to confirm these values. These observations demonstrate the capability of interferometric astrometry to reach microarcsecond accuracy in the narrow-angle regime for planet detection by reflex motion from the ground. This capability offers new perspectives and potential synergies with Gaia in the pursuit of low-mass exoplanets in the solar neighborhood.
Comment: Corresponding authors: G.Bourdarot, P.Kervella, O.Pfuhl. Accepted in A&A Letters
Comment: Corresponding authors: G.Bourdarot, P.Kervella, O.Pfuhl. Accepted in A&A Letters