225 research outputs found
Edge-on disk around the T Tauri star [MR81] Halpha 17 NE in CrA
Using the speckle camera SHARP at the 3.5m ESO NTT, K\"ohler and
collaborators found an object ~3.5 mag fainter in K only 1.3" north-east of the
T Tauri star [MR81] Ha 17 in the Corona Australis (CrA) star-forming region,
which could be either a brown dwarf or a T Tauri star with an edge-on disk. We
attempt to study this faint object in detail. We acquired deep VLT NACO
near-infrared images at three epochs to determine, whether [MR81] Ha 17 and the
nearby faint object are co-moving and to measure the infrared colors of both
objects. We obtained optical and infrared spectra of both objects with the VLT
using FORS and ISAAC, respectively, to determine spectral types and
temperatures as well as ages and masses. The T Tauri star [MR81] Ha 17 and the
faint nearby object have a projected separation of 1369.58 mas, i.e. 178 AU at
130 pc. They share the same proper motion (~5 sigma), so that they most
certainly form a bound binary pair. The apparently fainter component [MR81] Ha
17 NE has a spectral type of M2e, while the apparently brighter component
[MR81] Ha 17 SW, the previously known T Tauri star, has a spectral type of
M4-5e. We can identify a nearly edge-on disk around [MR81] Ha 17 NE by visual
inspection, which has a diameter of at least 30 to 50 AU. We are able to detect
strong emission lines in [MR81] Ha 17 NE, which are almost certainly due to
ongoing accretion. The NE object is detectable only by means of its scattered
light. If both objects are coeval (2-3 Myr) and located at the same distance
(~130 pc as CrA), then the apparently fainter [MR81] Ha 17 NE is more massive
(primary) component with a nearly edge-on disk and the apparently brighter
component [MR81] Ha 17 SW is less massive (com- panion). Both are low-mass T
Tauri stars with masses of ~0.5 and 0.23 \pm 0.05 solar masses, respectively.Comment: A&A in pres
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
The effect of air pollution on stone decay: the decay of the Drachenfels trachyte in industrial, urban, and rural environments—a case study of the Cologne, Altenberg and Xanten cathedrals
Defect Physics, Delithiation Mechanism, and Electronic and Ionic Conduction in Layered Lithium Manganese Oxide Cathode Materials
- …