We present the first simultaneous radio, X-ray, ultraviolet, and optical spectroscopic observations of the M8.5 dwarf TVLM 513-46546, with a duration of 9 hr. These observations are part of a program to study the origin of magnetic activity in ultracool dwarfs, and its impact on chromospheric and coronal emission. Here we detect steady quiescent

Standard binary evolution models of pulsars in very circular orbits can explain systems with lighter companions and weaker magnetic fields: they are descended from long-lived Low Mass X-ray Binaries with Roche-lobe overflow. By contrast, those having more massive companions and larger magnetic fields are descendants of Intermediate Mass systems

The generally adopted value for the solar abundance of indium is over six times higher than the meteoritic value. We address this discrepancy through numerical synthesis of the 451.13-nm line on which all indium abundance studies are based, both for the quiet Sun and the sunspot umbra spectrum, employing standard atmosphere models and accounting

From the equivalent widths of the main features of the K band spectra (the NaI, CaI and CO bandheads) we have derived the metallicities of the sources by means of the empirical scale obtained by Ramirez et al. (2000AJ....120..833R) and Frogel et al. (2001AJ....122.1896F) for luminous red giants. (2 data files).

Aims:The analysis of near infrared spectropolarimetric data at the internetwork in different regions on the solar surface could offer constraints that reject current modeling of these quiet areas. Methods: We present spectro-polarimetric observations of very quiet regions for different values of the heliocentric angle for the Fe i lines at 1.56 μm

We present near-infrared (1.15-2.50μm) medium-resolution (R = 1700) spectroscopy of a sample of 23 brown dwarf candidates in the young UpperSco association. We confirm membership of 21 brown dwarfs based on their spectral shape, comparison with field dwarfs and presence of weak gravity-sensitive features. Their spectral types range from M8 to L2