Bibcode
Bonfils, X.; Astudillo-Defru, N.; Díaz, R.; Almenara, J.-M.; Forveille, T.; Bouchy, F.; Delfosse, X.; Lovis, C.; Mayor, M.; Murgas, F.; Pepe, F.; Santos, N. C.; Ségransan, D.; Udry, S.; Wünsche, A.
Bibliographical reference
Astronomy and Astrophysics, Volume 613, id.A25, 9 pp.
Advertised on:
5
2018
Journal
Citations
84
Refereed citations
75
Description
The combination of high-contrast imaging and high-dispersion
spectroscopy, which has successfully been use to detect the atmosphere
of a giant planet, is one of the most promising potential probes of the
atmosphere of Earth-size worlds. The forthcoming generation of extremely
large telescopes (ELTs) may obtain sufficient contrast with this
technique to detect O2 in the atmosphere of those worlds that
orbit low-mass M dwarfs. This is strong motivation to carry out a census
of planets around cool stars for which habitable zones can be resolved
by ELTs, i.e. for M dwarfs within 5 parsec. Our HARPS survey has been a
major contributor to that sample of nearby planets. Here we report on
our radial velocity observations of Ross 128 (Proxima Virginis, GJ447,
HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source
hosts an exo-Earth with a projected mass m sini = 1.35
M⊕ and an orbital period of 9.9 days. Ross 128 b
receives less than 1.5 times as much flux as Earth from the Sun and its
equilibrium ranges in temperature between 269 K for an Earth-like albedo
and 213 K for a Venus-like albedo. Recent studies place it close to the
inner edge of the conventional habitable zone. An 80-day long light
curve from K2 campaign C01 demonstrates that Ross 128 b does not
transit. Together with the All Sky Automated Survey (ASAS) photometry
and spectroscopic activity indices, the K2 photometry shows that Ross
128 rotates slowly and has weak magnetic activity. In a habitability
context, this makes survival of its atmosphere against erosion more
likely. Ross 128 b is the second closest known exo-Earth, after Proxima
Centauri b (1.3 parsec), and the closest temperate planet known around a
quiet star. The 15 mas planet-star angular separation at maximum
elongation will be resolved by ELTs (>3λ/D) in the optical
bands of O2.
Based on observations made with the HARPS instrument on the ESO 3.6 m
telescope under the programme IDs 072.C-0488(A), 183.C-0437(A), and
191.C-0873(A) at Cerro La Silla (Chile).Radial velocity data (Table 5)
are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/613/A25
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