# 2006A&A...446.1165J

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 Query : 2006A&A...446.1165J

2006A&A...446.1165J - Astronomy and Astrophysics, volume 446, 1165-1176 (2006/2-2)

Radial velocity survey for planets and brown dwarf companions to very young brown dwarfs and very low-mass stars in ChamaeleonI with UVES at the VLT.

JOERGENS V.

Abstract (from CDS):

We present results of a radial velocity (RV) survey for planets and brown dwarf (BD) companions to very young BDs and (very) low-mass stars in the ChaI star-forming cloud. Time-resolved high-resolution echelle spectra of ChaHα1-8 and ChaHα12 (M6-M8), B34 (M5), CHXR74 (M4.5), and Sz23 (M2.5) were taken with UVES at the VLT between 2000 and 2004. The precision achieved for the relative RVs range between 40 and 670m/s and is sufficient to detect Jupiter mass planets around the targets. This is the first RV survey of very young BDs. It probes multiplicity, which is a key parameter for formation in an as yet unexplored domain, in terms of age, mass, and orbital separation. We find that the subsample of ten BDs and very low-mass stars (VLMSs, M≤0.12M, spectral types M5-M8) has constant RVs on time scales of 40 days and less. For this group, estimates of upper limits for masses of hypothetical companions range between 0.1MJup and 1.5MJup for assumed orbital separations of 0.1AU. This hints at a rather small multiplicity fraction for very young BDs/VLMSs, for orbital separations of ≤0.1AU and orbital periods of ≤40 days. Furthermore, the non-variable objects demonstrate the lack of any significant RV noise due to stellar activity down to the precision necessary to detect giant planets. Thus, very young BDs/VLMSs are suitable targets for RV surveys for planets. Three objects of the sample exhibit significant RV variations with peak-to-peak RV differences of 2-3km/s. For the highest mass object observed with UVES (Sz23, ∼0.3M), the variations are on time scales of days, which might be explained by rotational modulation. On the other hand, the BD candidate ChaHα8 (M6.5) and the low-mass star CHXR74 (M4.5) both display significant RV variations on times scales of ≥150 days, while they are both RV constant or show only much smaller amplitude variations on time scales of days to weeks, i.e. of the rotation periods. A suggested explanation for the detected RV variations of CHXR74 and ChaHα8 is that they are caused by giant planets or very low-mass BDs of at least a few Jupiter masses orbiting with periods of several months or longer. Thus, the presented RV data indicate that orbital periods of companions to very young BDs and (very) low-mass stars are possibly several months or longer, and that orbital separations are ≥0.2AU. This parameter range has not been covered for all targets yet, but will be probed by follow-up observations. Furthermore, we show that the scaled down equivalent to the BD desert found around solar-like stars would be a giant planet desert around BD and VLMS primaries, if formed by the same mechanism. The present data test its existence for the targets in the limited separation range of the survey. So far, no hints of companions in a giant planet desert'' have been found.

Journal keyword(s): stars: low-mass, brown dwarfs - stars: pre-main sequence - binaries: spectroscopic - techniques: radial velocities - planetary systems

Full paper

 Number of rows : 20
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 2MASS J11011926-7732383 ** 11 01 19.266 -77 32 38.31       19.4 16.59 M7+M8 36 0
2 [NC98] Cha HA 12 Em* 11 06 37.9647720216 -77 43 09.113892564     20.6   15.91 M6.5e 38 0
3 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1099 1
4 CHXR 74 TT* 11 06 57.3114166800 -77 42 10.639632780         13.66 M3Ve 44 0
5 [NC98] Cha HA 1 Y*O 11 07 16.6710048312 -77 35 53.212777692   22.8 21.0   16.38 M7.5/8e 84 0
6 CHXR 76 Or* 11 07 35.1774430800 -77 34 49.286652024   20.04 18.15   14.39 M4e 45 0
7 CHSM 10496 Em* 11 07 37.7410696536 -77 35 30.793352928   23.7 22.2   17.03 ~ 39 0
8 V* HK Cha Or* 11 07 42.3364909752 -77 33 59.394350844   21.9 19.8   15.26 ~ 78 0
9 [NC98] Cha HA 8 SB* 11 07 46.0912894776 -77 40 08.918309388   22.2 20.1   15.61 ~ 43 1
10 V* HL Cha Or* 11 07 52.2574621728 -77 36 57.037742172   21.5 19.51   15.07 ~ 47 0
11 Sz 23 Or* 11 07 58.0951794888 -77 42 41.352365124   15.8 18.04   14.63 M4Ve 63 0
12 CHSM 12180 Em* 11 08 18.9694304592 -77 39 17.131209948   20.5 18.52   14.50 ~ 40 0
13 ISO-ChaI 144 Em* 11 08 24.1193575992 -77 41 47.438803392   21.3 19.18   14.85 ~ 48 0
14 V* HQ Cha Or* 11 08 39.5017287912 -77 34 16.733892756   21.7 19.75   15.06 ~ 65 0
15 Ross 905 PM* 11 42 11.0933350978 +26 42 23.650782778   12.06 10.613 10.272 8.24 M3V 597 1
16 TWA 27 LM* 12 07 33.4675524840 -39 32 54.016625184     19.95 17.99 15.88 M8IVe 330 0
17 V* GQ Lup Or* 15 49 12.1053805848 -35 39 05.058139788 12.19 12.76 11.66 11.15   K7Ve 271 1
18 2MASSW J1858509-370631 Y*O 18 59 50.9461096368 -37 06 31.493373948           ~ 14 1
19 NAME CrA Complex reg 19 15 00.0 -37 30 00           ~ 106 1
20 BD-15 6290 BY* 22 53 16.7325836486 -14 15 49.304052185 12.928 11.749 10.192 9.013 7.462 M3.5V 962 1

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2023.03.24-16:51:08