2002A&A...394..911N


Query : 2002A&A...394..911N

2002A&A...394..911N - Astronomy and Astrophysics, volume 394, 911-926 (2002/11-2)

Coronal density diagnostics with Helium-like triplets: CHANDRA-LETGS observations of Algol, Capella, Procyon, ε Eri, α Cen A&B, UX Ari, AD Leo, YY Gem, and HR 1099.

NESS J.-U., SCHMITT J.H.M.M., BURWITZ V., MEWE R., RAASSEN A.J.J., VAN DER MEER R.L.J., PREDEHL P. and BRINKMAN A.C.

Abstract (from CDS):

We present an analysis of ten cool stars (Algol, Capella, Procyon, ε Eri, α Cen A&B, UX Ari, AD Leo, YY Gem, and HR 1099) observed with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra X-ray Observatory. This sample contains all cools stars observed with the LETGS presently available to us with integration times sufficiently long to warrant a meaningful spectral analysis. Our sample comprises inactive, moderately active, and hyperactive stars and samples the bulk part of activity levels encountered in coronal X-ray sources. We use the LETGS spectra to carry out density and temperature diagnostics with an emphasis on the H-like and the He-like ions. We find a correlation between line flux ratios of the Lyα and He-like resonance lines with the mean X-ray surface flux. We determine densities using the He-like triplets. For all stars we find no significant deviations from the low-density limit for the ions of Ne, Mg, and Si, while the measured line ratios for the ions of C, N, and O do show evidence for departures from the low-density limit in the active stars, but not in the inactive stars. Best measurements can be made for the Ovii triplet where we find significant deviations from the low-density limit for the stars Algol, Procyon, YY Gem, ε Eri, and HR 1099. We discuss the influence of radiation fields on the interpretation of the He-like triplet line ratios in the low-Z ions, which is relevant for Algol, and the influence of dielectronic satellite lines, which is relevant for Procyon. For the active stars YY Gem, ε Eri, and HR 1099 the low f/i ratios can unambiguously be attributed to high densties in the range 1-3x1010cm–3 at OVII temperatures. We find our LETGS spectra to be an extremely useful tool for plasma diagnostics of stellar coronae.

Abstract Copyright:

Journal keyword(s): atomic data - techniques: spectroscopic - stars: coronae - stars: late-type - stars: activity - X-rays: stars

Simbad objects: 9

goto Full paper

goto View the references in ADS

Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 * bet Per EB* 03 08 10.1324535 +40 57 20.328013 1.70 2.07 2.12 2.08 2.11 B8V 1219 1
2 V* UX Ari RS* 03 26 35.3756804760 +28 42 54.226408428 7.76 7.28 6.37     K0IV 697 0
3 * eps Eri BY* 03 32 55.8444911587 -09 27 29.739493865 5.19 4.61 3.73 3.00 2.54 K2V 1932 1
4 HD 22468 RS* 03 36 47.2904292073 +00 35 15.943692002 7.09 6.79 5.90     K2:Vnk 1167 0
5 * alf Aur SB* 05 16 41.35871 +45 59 52.7693 1.33 0.88 0.08 -0.52 -0.96 G3III: 1177 0
6 V* YY Gem BY* 07 34 37.4474327544 +31 52 10.179641496 11.60 10.56 9.27 7.69 6.67 M0.5VeFe-2 854 0
7 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1864 0
8 V* AD Leo Er* 10 19 36.2808181226 +19 52 12.010446571   10.82 9.52 9.19   dM3 1340 1
9 * alf Cen ** 14 39 40.4 -60 50 20   0.4 -0.1     G2V+K1V 953 0

To bookmark this query, right click on this link: simbad:objects in 2002A&A...394..911N and select 'bookmark this link' or equivalent in the popup menu