Dense cloud cores in massive star-forming regions

Baltic Astronomy 13:3 (2004) 411-414

Authors:

B Posselt, R Klein, K Schreyer, T Henning

Abstract:

We have performed a submillimeter survey of the areas around 47 selected IRAS point sources of high luminosity. A number of new submm sources were found. The high multiplicity of the sources suggests that isolated massive-star formation is a rare event. In some cases the filaments near the young stellar objects (YSO) or between them were found. The pointers of massive star formation like masers, outflows and high-density knots were identified. Available catalogs in the near-infrared (2MASS), mid-infrared (MSX point sources) and radio continuum (NVSS at 1.4 GHz point sources) were correlated to our submm maps.

Finding Faint Intermediate-mass Black Holes in the Radio Band

(2004)

Authors:

TJ Maccarone, RP Fender, AK Tzioumis

GRS 1915+105: The first three months with INTEGRAL

European Space Agency, (Special Publication) ESA SP (2004) 299-305

Authors:

DC Hannikainen, O Vilhu, J Rodriguez, NJ Westergaard, S Shaw, GG Pooley, T Belloni, AA Zdziarski, RW Hunstead, K Wu, S Brandt, A Castro-Tirado, PA Charles, AJ Dean, P Durouchoux, RP Fender, P Hakala, CR Kaiser, AR King, N Lund, IF Mirabel, J Poutanen

Abstract:

GRS 1915+105 is being observed as part of an Open Time monitoring program with INTEGRAL. Three out of six observations from the monitoring program are presented here, in addition to data obtained through an exchange with other observers. We also present simultaneous RXTE observations of GRS 1915+105. During INTEGRAL Revolution 48 (2003 March 6) the source was observed to be in a highly variable state, characterized by 5-minute quasi-periodic oscillations. During these oscillations, the rise is faster than the decline, and is harder. This particular type of variability has never been observed before. During subsequent INTEGRAL revolutions (2003 March-May), the source was in a steady or "plateau" state (also known as class χaccording to Belloni et al. 2000). Here we discuss both the temporal and spectral characteristics of the source during the first three months of observations. The source was clearly detected with all three gamma-ray and X-ray instruments onboard INTEGRAL.

Viscous shear instability in weakly magnetized, dilute plasmas

Astrophysical Journal 616:2 I (2004) 857-864

Abstract:

When the ion mean free path much exceeds the Larmor radius in a plasma, the viscous stress tensor is altered dramatically and depends only on quantities measured along the field lines. This regime corresponds to typical interstellar medium conditions in galaxies and protogalaxies, even if the magnetic field is extremely weak, with a negligible Lorentz force on all scales of interest. In this work, the only role of the magnetic field is to channel angular momentum transport along its lines of force. We show that differential rotation in such a gas is highly unstable, with a maximum growth rate exceeding that of the magnetorotational instability. The regime of interest has been treated previously by plasma kinetic methods. Where there is overlap, our work appears to be in agreement with the kinetic results. The nonlinear outcome of this instability is likely to be a turbulent process, significantly augmenting the magnetorotational instability, and important to the initial phases of the amplification of small galactic magnetic fields.

Astrophysics in the lab

Physics World IOP Publishing 17:12 (2004) 20-21