arXiv subjects

R. Neuhäuser

Publications and source records attributed to R. Neuhäuser.

93 records · Page 6Linked to original sources

arXiv2001

Multiplicity of young brown dwarfs in Cha I

How frequent are brown dwarf binaries? Do brown dwarfs have planets? Are current theoretical pre-main-sequence evolutionary tracks valid down to the substellar regime? - Any detection of a companion to a brown dwarf takes us one step forward towards answering these basic questions of star formation. We report here on a search for spectroscopic and visual companions to young brown dwarfs in the Cha I star forming cloud. Based on spectra taken with UVES at the VLT, we found significant radial velocity (RV) variations for five bona-fide and candidate brown dwarfs in Cha I. They can be caused by either a (substellar or planetary) companion or stellar activity. A companion causing the detected RV variations would have about a few Jupiter masses. We are planning further UVES observations in order to explore the nature of the detected RV variations. We also found that the RV dispersion is only ~ 2km/s indicating that there is probably no run-away brown dwarf among them. Additionally a search for companions by direct imaging with the HST and SOFI (NTT) has yielded to the detection of a few companion candidates in larger orbits.

astro-ph↗

arXiv2001

The T Tauri star RXJ1608.6-3922 - not an eclipsing binary but a spotted single star

High-resolution spectroscopy and photometric monitoring of the pre-main sequence star RXJ1608.6-3922 shows that it is not an eclipsing binary, as previously claimed. Radial velocity measurements covering suitable time spans in order to detect a spectroscopic binary with the claimed period of about 7 days have been performed. The scatter of the radial velocity does not exceed 2.4 km/s, defining an upper mass limit of 24 Jupiter masses for any eclipsing companion orbiting this star with the claimed period. Photometric observations of RXJ1608.6-3922 in 7 consecutive nights (i.e. as long as the claimed orbital period) reveal brightness variations of the order of 0.2 mag with a period of 3.6 days. The shape of the detected light curve differs from a light curve of the star recorded in 1996. The small variations of the radial velocity, the variable shape of the light curve, as well as (B-V) color variations suggest that the flux of RXJ 1608.6-3922 is modulated by spots on the stellar surface with a rotational period of 3.6 days. The stellar activity of this star seems to be highly variable, taking into account the variable shape of the light curve, with an amplitude varying from 0.5 to 0.2 mag in a few years, as well as hints for a variable H$_α$ equivalent width.

astro-ph↗

arXiv2000

A Search for the Optical/Infrared Counterpart of the Anomalous X-ray Pulsar 1E 1841-045

We have carried out a search for the optical and infrared counterpart of the Anomalous X-ray Pulsar 1E 1841-045, which is located at the center of the supernova remnant Kes73. We present the first deep optical and infrared images of the field of 1E 1841-045, as well as optical spectroscopy results that exclude the brightest objects in the error circle as possible counterparts. A few of the more reddened objects in this region can be considered as particularly interesting candidates, in consideration of the distance and absorption expected from the association with Kes73. The strong interstellar absorption in the direction of the source does not allow to completely exclude the presence of main sequence massive companions.

astro-ph↗