X-ray Emission near the Substellar Limit: The sigma Orionis and Taurus Star Forming Regions

Abstract

We have carried out an extensive search for X-ray emission from young, very low-mass objects near and beyond the substellar limit, making use of archived ROSAT PSPC and HRI observations pointed at Brown Dwarfs and Brown Dwarf candidates in the young sigma Orionis and Taurus-Auriga associations. In sigma Ori we identify three Brown Dwarf candidates with X-ray sources; in Taurus-Auriga we add one further X-ray detection of a Brown Dwarf to the list published earlier. We combine this data with all previously X-ray detected Brown Dwarfs and Brown Dwarf candidates in young stellar associations and star forming regions to perform a study of stellar activity parameters on the as yet largest sample of young, very low mass objects. A similar relation between X-ray and bolometric luminosity, and H-alpha emission, respectively, as is known for T Tauri stars seems to hold for young objects down to the substellar limit, too. No signs for a change in X-ray activity are found on the transition to substellar masses.

9 pages, 5 (9) figures; fig. 1-4 are available only in the preprint or in the ps-file via <http://www.xray.mpe.mpg.de/~stelzer/publications.html>, accepted for publication in A&A

References in corpus (9)

• Lithium and Halpha in stars and brown dwarfs of sigma Orionis
• The Substellar Mass Function in sigma Orionis
• Evidence for Circumstellar Disks around Young Brown Dwarfs in the Trapezium Cluster
• Exploring Brown Dwarf Disks
• X-ray emission from young stars in Taurus-Auriga-Perseus: Luminosity functions and the rotation-activity-age relation
• Four Brown Dwarfs in the Taurus Star-Forming Region
• Optical spectroscopy of isolated planetary mass objects in the sigma Orionis cluster
• Keck NIRC Observations of Planetary-mass Candidate Members in the sigma Orionis Open Cluster
• UVES spectra of young brown dwarfs in Cha I: radial and rotational velocities

Cited by in corpus (30)

• Accretion in Young Stellar/Substellar Objects
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. III. X-ray, Radio, and H-alpha Activity Trends in M and L Dwarfs
• Rotation and accretion of very low mass objects in the SigmaOri cluster
• First Detection of Millimeter Dust Emission from Brown Dwarf Disks
• Spectroscopic rotational velocities of brown dwarfs
• Rotation and variability of very low mass stars and brown dwarfs near Epsilon Ori
• The First Detailed Look at a Brown Dwarf Disk
• Simultaneous Chandra and VLA Observations of Young Stars and Protostars in rho Ophiuchus Cloud Core A
• Detection and high-resolution spectroscopy of a huge flare on the old M9 dwarf DENIS 104814.7-395606.1
• Optical Linear Polarization of Late M- and L-Type Dwarfs
• The brown dwarf population in the Chamaeleon I cloud
• XMM-Newton observations of the sigma Ori cluster. II. Spatial and spectral analysis of the full EPIC field
• X-ray emission of brown dwarfs: Towards constraining the dependence on age, luminosity, and temperature
• The X-ray emission from Young Stellar Objects in the rho Ophiuchi cloud core as seen by XMM-Newton
• Coronal X-ray emission from an intermediate-age brown dwarf
• An X-ray census of young stars in the Chamaeleon I North cloud
• X-ray emission from the young brown dwarfs of the Taurus Molecular Cloud
• A new strongly X-ray flaring M9 dwarf in the solar neighborhood
• XMM-Newton observations of the nearby brown dwarf LP 944-20
• Quiescent X-ray emission from an evolved brown dwarf ?
• Sejong Open Cluster Survey (SOS). III. The Young Open Cluster NGC 1893 in the H II Region W8
• New deep XMM-Newton observations to the west of the sigma Orionis cluster
• The enigmatic young brown dwarf binary FU Tau: accretion and activity
• Constraining the properties of spots on Pleiades very low mass stars
• X-ray emission from a brown dwarf in the Pleiades
• A U-band survey of brown dwarfs in the Taurus Molecular Cloud with the XMM-Newton Optical/UV Monitor
• X-ray Detections of Two Young Bona-Fide Brown Dwarfs
• A TGAS/Gaia DR1 parallactic distance to the sigma Orionis cluster
• At the Bottom of the Main Sequence: Activity and magnetic fields beyond the threshold to complete convection
• The first evidence of tidally induced activity in a brown dwarf-M dwarf pair: A Chandra study of the NLTT 41135/41136 system