2020A&A...641A.113M


C.D.S. - SIMBAD4 rel 1.7 - 2020.12.05CET00:48:44

2020A&A...641A.113M - Astronomy and Astrophysics, volume 641A, 113-113 (2020/9-1)

GJ 357 b. A super-Earth orbiting an extremely inactive host star.

MODIRROUSTA-GALIAN D., STELZER B., MAGAUDDA E., MALDONADO J., GUDEL M., SANZ-FORCADA J., EDWARDS B. and MICELA G.

Abstract (from CDS):


Aims. In this paper we present a deep X-ray observation of the nearby M dwarf GJ 357 and use it to put constraints on the atmospheric evolution of its planet, GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ 357 in order to see how they affect the perceived planetary properties.
Methods. By comparing the observed X-ray luminosity of its host star, we estimate the age of GJ 357 b as derived from a recent XMM-Newton observation (logLx[erg/s]=25.73), with Lx-age relations for M dwarfs. We find that GJ 357 presents one of the lowest X-ray activity levels ever measured for an M dwarf, and we put a lower limit on its age of 5 Gyr. Using this age limit, we performed a backwards reconstruction of the original primordial atmospheric reservoir. Furthermore, by considering the systematic errors in the stellar parameters, we find a range of possible planetary masses, radii, and densities.
Results. From the backwards reconstruction of the irradiation history of GJ 357 b's we find that the upper limit of its initial primordial atmospheric mass is ∼38M. An initial atmospheric reservoir significantly larger than this may have survived through the X-ray and ultraviolet irradiation history, which would not be consistent with current observations that suggest a telluric composition. However, given the relatively small mass of GJ 357 b, even accreting a primordial envelope ≥10M would have been improbable as an unusually low protoplanetary disc opacity, large-scale migration, and a weak interior luminosity would have been required. For this reason, we discard the possibility that GJ 357 b was born as a Neptunian- or Jovian-sized body. In spite of the unlikelihood of a currently existing primordial envelope, volcanism and outgassing may have contributed to a secondary atmosphere. Under this assumption, we present three different synthetic IR spectra for GJ 357 b that one might expect, consisting of 100% CO2, 100% SO2, and 75% N2, 24% CO2 and 1% H2O, respectively. Future observations with space-based IR spectroscopy missions will be able to test these models. Finally, we show that the uncertainties in the stellar and planetary quantities do not have a significant effect on the estimated mass or radius of GJ 357 b.

Abstract Copyright: © ESO 2020

Journal keyword(s): planets and satellites: terrestrial planets - planets and satellites: atmospheres - planet-star interactions - planets and satellites: physical evolution - X-rays: stars

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 3038 0
2 Cl Melotte 25 OpC 04 26 54.00 +15 52 00.0           ~ 2715 0
3 HD 33793 Ro* 05 11 40.5893175460 -45 01 06.353955874 11.624 10.433 8.853 7.9 6.899 M1VIp 286 0
4 CoRoT-7b Pl 06 43 49.4690410679 -01 03 46.825797768           ~ 358 1
5 * rho01 Cnc e Pl 08 52 35.8113282132 +28 19 50.956901366           ~ 416 1
6 NAME L 678-39b Pl 09 36 01.6372518187 -21 39 38.878281901           ~ 18 0
7 NAME L 678-39c Pl 09 36 01.6372518187 -21 39 38.878281901           ~ 4 0
8 NAME L 678-39d Pl 09 36 01.6372518187 -21 39 38.878281901           ~ 5 0
9 L 678-39 PM* 09 36 01.6372518187 -21 39 38.878281901 13.647 12.48 10.906 9.858 8.577 M2.5V 106 0
10 NAME TW Hya Association As* 11 01.9 -34 42           ~ 830 0
11 NAME Barnard's star BY* 17 57 48.4997994034 +04 41 36.111354228 12.497 11.24 9.511 8.298 6.741 M4V 673 2

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2020.12.05-00:48:44

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