Contributions of late-type dwarf stars to the soft X-ray diffuse background

1990 ◽  
Vol 361 ◽  
pp. 207 ◽  
Author(s):  
J. H. M. M. Schmitt ◽  
S. L. Snowden
Keyword(s):  
Late Type ◽  
Dwarf Stars ◽  
X Ray ◽  
Diffuse Background

X‐Ray Spectroscopy of Rapidly Rotating, Late‐Type Dwarf Stars

1999 ◽  
Vol 512 (2) ◽  
pp. 874-891 ◽  
Author(s):  
K. P. Singh ◽  
S. A. Drake ◽  
E. V. Gotthelf ◽  
N. E. White
Keyword(s):  
Late Type ◽  
Dwarf Stars ◽  
X Ray

scholarly journals On the Stellar Rotation-Activity Connection

1983 ◽  
Vol 102 ◽  
pp. 279-300 ◽  
Author(s):  
Robert Rosner
Keyword(s):  
Surface Activity ◽  
Rotation Rate ◽  
Late Type ◽  
Stellar Rotation ◽  
Dwarf Stars ◽  
X Ray

I discuss the connection between the rotation rate of late-type dwarf stars and their level of surface “activity” (as deduced from visible, UV, and X-ray observations) from both theoretical and observational perspectives.

scholarly journals Observations of Absorption Lines from Highly Ionized Atoms

1984 ◽  
Vol 81 ◽  
pp. 153-168 ◽  
Author(s):  
Edward B. Jenkins
Keyword(s):  
Absorption Lines ◽  
X Rays ◽  
Interstellar Gas ◽  
Hot Stars ◽  
Dwarf Stars ◽  
Lower Velocity ◽  
X Ray ◽  
Diffuse Background ◽  
Supernova Explosions ◽  
Early Type Stars

AbstractIn the ultraviolet spectra of hot stars, we can see absorption lines from highly ionized species in the interstellar medium. Observations of these features have been very influential in revising our perception of the medium's various physical states and how gases in space are heated and ionized. The pervasiveness of 0 VI absorption lines, coupled with complementary observations of a diffuse background in soft x-rays and EUV radiation, shows that there is an extensive network of low density gas (n ≈ fewx10-3cm-3) existing at “coronal” temperatures, 5.3 ≲ log T ≲ 6.3. Thus, while we once thought that x-rays and cosmic rays were the dominant sources of excitation and heating of the interstellar gas, we now realize that shocks created by supernova explosions or mass loss from early-type stars can propagate freely through space and eventually transfer a large amount of energy to the medium. To create the coronal temperatures, the shocks must have velocities in excess of 150 km s-1; shocks at somewhat lower velocity (v ≲ 100 km s-1) can be directly observed in the lines of Si III. Observations of other lines in the ultraviolet, such as Si IV and C IV, may highlight the widespread presence of energetic uv radiation from very hot, dwarf stars. More advanced techniques in visible and x-ray astronomical spectroscopy may open up for inspection selected lines from atoms in much higher stages of ionization.

scholarly journals X-Ray Coronae from Single Late-Type Dwarf Stars

1998 ◽  
Vol 188 ◽  
pp. 222-223
Author(s):  
K.P. Singh ◽  
S.A. Drake ◽  
N.E. White
Keyword(s):  
Binary Systems ◽  
Late Type ◽  
Dwarf Stars ◽  
X Ray ◽  
Elemental Abundances ◽  
Moderate Resolution

Study of X-ray coronae from late-type stars with moderate resolution X-ray spectroscopy with ASCA, has led to the characterization of temperatures and measurements of elemental abundances in their coronae. Several RS CVn and Algol-type binary systems, and single late-type stars have been observed. We present here the results obtained from X-ray spectroscopy of recently observed single F-G-K-M type dwarfs. The sample observed with ASCA contains αCen (Mewe et al. 1997), π1UMa (Drake et al. 1994), YY Gem, Speedy Mic, GJ 890 (Singh et al. 1997), EK Dra, HN Peg, κ1Cet (Guedel et al. 1997), AB Dor (Mewe et al. 1996) and HD 35850 (Tagliaferri et al. 1997).

X-Ray Coronae from Single Late-Type Dwarf Stars

1998 ◽  
pp. 222-223
Author(s):  
K. P. Singh ◽  
S. A. Drake ◽  
N. E. White
Keyword(s):  
Late Type ◽  
Dwarf Stars ◽  
X Ray

scholarly journals X-Ray Emission from Distant Stellar Clusters

1998 ◽  
Vol 188 ◽  
pp. 220-221
Author(s):  
N.S. Schulz ◽  
J.H. Kastner
Keyword(s):  
Main Sequence ◽  
Sequence Evolution ◽  
Late Type ◽  
Low Mass Stars ◽  
Dwarf Stars ◽  
X Ray ◽  
T Tauri ◽  
Low Mass ◽  
M Stars ◽  
M Dwarf Stars

Observations with the Einstein Observatory indicated that stellar X-ray activity diminishes in clusters older than 70 Myr (Pleiades). ROSAT observations of older clusters also support this result (see Caillault 1995 and references therein). The timescales over which young stars diminish in X-ray luminosity depends on spectral type (Randich et al. 1996), leading to the conclusion that X-ray activity in late type PMS depends on age and stellar mass. F and G-stars approach the main sequence much faster and the diminishing rates of X-ray activity from F to M stars start to differ considerably. Kastner et al. (1997) observed that the mean of the ratio Lx/Lbol for K and M dwarf stars increases monotonically for low-mass stars from the very early T Tauri stage through the age of the Pleiades cluster, reflecting the contraction and spin-up of such stars during pre-main sequence evolution. This ratio then decreases towards middle aged stars, as late-type main sequence stars spin down. Here we extend this result by including more distant clusters that are younger overall than those considered by Kastner et al. and also including earlier spectral types.

scholarly journals Mapping Cool Gas in the ISM with ROSAT

1997 ◽  
Vol 166 ◽  
pp. 283-286
Author(s):  
I.B. Hutchinson ◽  
R.S. Warwick ◽  
R. Willingale
Keyword(s):  
Column Density ◽  
Line Of Sight ◽  
Local Interstellar Medium ◽  
Late Type ◽  
Dwarf Stars ◽  
General Direction ◽  
X Ray ◽  
White Dwarf Stars ◽  
Cool Gas ◽  
Using Data

AbstractWe have investigated the distribution of cool gas within the local interstellar medium (<150 pc) using data derived from both the ROSAT X-ray and EUV all-sky surveys. The EUV/X-ray spectra for a sample of 89 white dwarf stars and 200 active late-type stars have been analysed to give an estimate of the gas column density along each object’s line of sight. In order to extend the sky coverage we have also included in the analysis 190 late-type stars detected only in the X-ray band. The derived NHI measurements confirm the size of the local low density bubble as typically 50-100 pc and also show that in the general direction of Loop I there is a substantial excess of absorption at a range of distances from 10-150 pc.

scholarly journals 1/4 Ke V Diffuse Background and the Local Interstellar Medium

1989 ◽  
Vol 120 ◽  
pp. 536-536
Author(s):  
S.L. Snowden
Keyword(s):  
Interstellar Medium ◽  
Filling Factor ◽  
Thermal Emission ◽  
Mean Free Path ◽  
Physical Parameters ◽  
X Rays ◽  
Local Interstellar Medium ◽  
X Ray ◽  
Diffuse Background ◽  
X Ray Background

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

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