X-RAY-EMISSION FROM HYBRID-CHROMOSPHERE STARS

被引:23
作者
BROWN, A
DRAKE, SA
VANSTEENBERG, ME
LINSKY, JL
机构
[1] NATL INST STAND & TECHNOLOGY,BOULDER,CO 80309
[2] ST SYST CORP,LANHAM,MD 20706
[3] NASA,GODDARD SPACE FLIGHT CTR,NATL SPACE SCI DATA CTR,GREENBELT,MD 20771
[4] UNIV COLORADO,DIV QUANTUM PHYS,BOULDER,CO 80309
关键词
STARS; CHROMOSPHERES; LATE-TYPE; X-RAYS;
D O I
10.1086/170080
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The current evidence for the existence of hot (greater-than-or-equal-to 10(6) K) plasma around hybrid-chromosphere stars is examined. EXOSAT observations of the hybrid star alpha TrA provide the first X-ray detection of such a star. An X-ray differential emission measure locus is derived and used to demonstrate that the temperature of the X-ray-emitting plasma is unlikely to be lower than 10(6) K. Estimates are made of the interstellar hydrogen column densities toward hybrid stars using a variety of methods in order to allow interpretation of X-ray observations. The X-ray luminosity of alpha TrA is calculated to be approximately 5 x 10(29) ergs s-1 over the 1-300 angstrom spectral region and 7 x 10(28) ergs s-1 in the Einstein 0.2-4 keV (3-60 angstrom) energy range for N(H) = 5 x 10(19) cm-2 and a temperature of 10(6) K. X-ray nondetections of other hybrid stars from EXOSAT and Einstein satellite observations are consistent with their interstellar hydrogen column densities, if the ratio of their intrinsic X-ray to transition region emission line surface fluxes are the same as for alpha TrA. It now seems that the conceptual model of Linsky, in which the higher temperature plasma is magnetically confined and separated from the outflowing stellar wind, is most likely to correctly represent the physical structuring of hybrid star outer atmospheres.
引用
收藏
页码:614 / 619
页数:6
相关论文
共 41 条
[1]   ON THE DIVIDING LINE FOR STELLAR CORONAE [J].
ANTIOCHOS, SK ;
HAISCH, BM ;
STERN, RA .
ASTROPHYSICAL JOURNAL, 1986, 307 (02) :L55-L59
[2]   THE COOL HALF OF THE H-R DIAGRAM IN SOFT X-RAYS [J].
AYRES, TR ;
LINSKY, JL ;
VAIANA, GS ;
GOLUB, L ;
ROSNER, R .
ASTROPHYSICAL JOURNAL, 1981, 250 (01) :293-299
[3]  
AYRES TR, 1985, APJ, V29, pL5
[4]  
AYRES TR, 1991, UNPUB
[5]   SURVEY OF INTER-STELLAR H-I FROM L-ALPHA ABSORPTION-MEASUREMENTS .2. [J].
BOHLIN, RC ;
SAVAGE, BD ;
DRAKE, JF .
ASTROPHYSICAL JOURNAL, 1978, 224 (01) :132-142
[6]   COPERNICUS OBSERVATIONS OF INTERSTELLAR ABSORPTION AT LYMAN ALPHA [J].
BOHLIN, RC .
ASTROPHYSICAL JOURNAL, 1975, 200 (02) :402-414
[7]   MODELS OF TRANSITION REGIONS IN HYBRID STARS [J].
BROSIUS, JW ;
MULLAN, DJ .
ASTROPHYSICAL JOURNAL, 1986, 301 (02) :650-663
[8]   HIGH-RESOLUTION, FAR-ULTRAVIOLET STUDY OF BETA DRACONIS (G2 IB-II) - TRANSITION REGION STRUCTURE AND ENERGY-BALANCE [J].
BROWN, A ;
JORDAN, C ;
STENCEL, RE ;
LINSKY, JL ;
AYRES, TR .
ASTROPHYSICAL JOURNAL, 1984, 283 (02) :731-744
[9]  
BROWN A, 1986, ADV SPACE RES, V6, P195
[10]  
BROWN A, 1986, ESA SP263, P169