2018A&A...610A..39H


Query : 2018A&A...610A..39H

2018A&A...610A..39H - Astronomy and Astrophysics, volume 610A, 39-39 (2018/2-1)

The nature of the giant exomoon candidate Kepler-1625 b-i.

HELLER R.

Abstract (from CDS):

The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indicate the presence of a hitherto unknown kind of gas giant moon, if confirmed. Three transits of Kepler-1625 b have been observed, allowing estimates of the radii of both objects. Mass estimates, however, have not been backed up by radial velocity measurements of the host star. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e., via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0.4MJup) to a brown dwarf (BD; up to 75MJup) or even a very-low-mass star (VLMS; MJup~=0.11M). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water-rock companion of about 180M. Furthermore, the planet-moon dynamics during the transits suggest a total system mass of 17.6–12.6+19.2MJup. A Neptune-mass exomoon around a giant planet or low-mass BD would not be compatible with the common mass scaling relation of the solar system moons about gas giants. The case of a mini-Neptune around a high-mass BD or a VLMS, however, would be located in a similar region of the satellite-to-host mass ratio diagram as Proxima b, the TRAPPIST-1 system, and LHS 1140 b. The capture of a Neptune-mass object around a 10MJup planet during a close binary encounter is possible in principle. The ejected object, however, would have had to be a super-Earth object, raising further questions of how such a system could have formed. In summary, this exomoon candidate is barely compatible with established moon formation theories. If it can be validated as orbiting a super-Jovian planet, then it would pose an exquisite riddle for formation theorists to solve.

Abstract Copyright: © ESO 2018

Journal keyword(s): accretion, accretion disks - eclipses - planetary systems - planets and satellites: composition - planets and satellites: formation - planets and satellites: individual: Kepler-1625 b

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 G 268-38 PM* 00 44 59.3309137511 -15 16 17.542839990     14.150 13.801   M4.5 115 0
2 NAME G 268-38b Pl 00 44 59.3314993038 -15 16 17.543124886           ~ 140 0
3 NAME Proxima Centauri b Pl 14 29 42.9451234609 -62 40 46.170818907           ~ 310 0
4 NAME Proxima Centauri Er* 14 29 42.9461331854 -62 40 46.164680672 14.21 12.95 11.13 9.45 7.41 M5.5Ve 1175 0
5 Kepler-1625 Ro* 19 41 43.0400811024 +39 53 11.499004176           ~ 44 0
6 Kepler-1625b Pl 19 41 43.0401596937 +39 53 11.498985535           ~ 64 1
7 Kepler-51 Ro* 19 45 55.1428629456 +49 56 15.650520684           ~ 109 1
8 Kepler-51b Pl 19 45 55.1429734720 +49 56 15.650638630           ~ 81 1
9 TRAPPIST-1 LM* 23 06 29.3684948589 -05 02 29.037301866     18.798 16.466 14.024 M7.5e 787 0

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2022.11.29-16:49:24

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