2008A&A...487..317A


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.12CET09:44:19

2008A&A...487..317A - Astronomy and Astrophysics, volume 487, 317-322 (2008/8-3)

A mini-survey of ultracool dwarfs at 4.9 GHz.

ANTONOVA A., DOYLE J.G., HALLINAN G., BOURKE S. and GOLDEN A.

Abstract (from CDS):

A selection of ultracool dwarfs are known to be radio active, with both gyrosynchrotron emission and the electron cyclotron maser instability being given as likely emission mechanisms. We explore whether ultracool dwarfs previously undetected at 8.5GHz may be detectable at a lower frequency. We select a sample of fast rotating ultracool dwarfs with no detectable radio activity at 8.5GHz, observing each of them at 4.9GHz. From the 8 dwarfs in our sample, we detect emission from 2MASS J07464256+2000321, with a mean flux level of 286±24µJy. The light-curve of 2MASS J07464256+2000321, is dominated towards the end of the observation by a very bright, ≃100% left circularly polarized burst during which the flux reached 2.4mJy. The burst was preceded by a raise in the level of activity, with the average flux being ≃160µJy in the first hour of observation rising to ≃400µJy in the 40min before the burst. During both periods, there is significant variability. The detection of 100% circular polarization in the emission at 4.9GHz points towards the electron cyclotron maser as the emission mechanism. However, the observations at 4.9GHz and 8.5GHz were not simultaneous, thus the actual fraction of dwarfs capable of producing radio emission, as well as the fraction of those that show periodic pulsations is still unclear, as indeed are the relative roles played by the electron cyclotron maser instability versus gyrosynchrotron emission, therefore we cannot assert if the previous non-detection at 8.5GHz was due to a cut-off in emission between 4.9 and 8.4GHz, or due to long term variability.

Abstract Copyright:

Journal keyword(s): stars: low-mass, brown dwarfs - radio continuum: stars - radiation mechanisms: general - masers

Simbad objects: 13

goto Full paper

goto View the reference in ADS

Number of rows : 13

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 [SBB2014] 5121623 LM* 03 35 02.0920098507 +23 42 35.415191371       17.67   M8.5V 45 1
2 LP 944-20 BD* 03 39 35.2525168530 -35 25 43.628465433   20.17 18.69 16.39 13.288 M9.5Ve 260 0
3 Cl* Melotte 22 KPNO 2 BD* 03 45 43.1604506693 +25 40 23.246972754         17.36 L0 112 0
4 2MASS J05233822-1403022 BD* 05 23 38.2238597336 -14 03 02.008934344           L2.5 50 0
5 ICRF J054236.1+495107 Sy1 05 42 36.13789843 +49 51 07.2337251   18.45 17.80 17.210   ~ 1235 1
6 LSPM J0746+2000 BD* 07 46 42.49536 +20 00 32.6124   21.7 17.7 17.9 15.034 L0.5V 168 1
7 DENIS J104814.6-395606 BD* 10 48 14.5734267094 -39 56 06.843210566     17.532 15.051 12.67 M8.5Ve: 112 0
8 NAME Kelu-1 BD* 13 05 40.1737206066 -25 41 05.830344467         16.85 L2+L3.5 235 0
9 TVLM 513-46 BD* 15 01 08.1871800643 +22 50 02.120480463   21.4 15.09 18.0   M8.5V 145 0
10 2MASSW J1507476-162738 BD* 15 07 47.6756748763 -16 27 40.118410414     22.136 18.928 16.579 L5V 164 0
11 2MASS J16241436+0029158 BD* 16 24 14.367 +00 29 15.82           T6V 131 0
12 2MASS J16322911+1904407 BD* 16 32 29.114 +19 04 40.71       22.42 19.98 L8 115 0
13 2MASSW J2224438-015852 BD* 22 24 43.8550503291 -01 58 53.265872547           L4.5V 103 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2008A&A...487..317A and select 'bookmark this link' or equivalent in the popup menu


2019.12.12-09:44:19

© Université de Strasbourg/CNRS

    • Contact