Главная     Выжить во Вселенной    
Services
    Why to Inhabit     Top Contributors     Астрофотография     Коллекция     Форум     Blog New!     Помощь     Войти  
→ Adopt this star  

HD 117400


Оглавление

Изображения

Загрузить ваше изображение

DSS Images   Other Images


Публикации по объекту

Hybrid stars and the reality of "dividing lines" among G to K bright giants and supergiants.
We present results of pointed ROSAT PSPC observations of 15 hybridstars/candidates, which have been analyzed in a homogenous way. 7 ofthese stars were observed in X-rays for the first time. 12 out of 15hybrid stars have been detected as X-ray sources, some of them close tothe detection limit. We conclude that essentially all hybrid stars asdefined by the simultaneous presence of transition region line emissionand cool stellar winds are X-ray sources if exposed sufficiently deep.The X-ray luminosities of hybrid stars cover a range between 2x10^27^and ~10^30^erg/s. Their X-ray surface fluxes can be as low as =~20erg/cm^2^/s and thus considerably lower than those of normal luminosityclass (LC) III giants. X-ray spectra of hybrid stars tend to be harderthan that of normal LC III giants, moreover, the X-ray brightest starshave the hardest spectra. We find that for K II giants the normalizedX-ray flux versus C IV flux obeys a power law with an exponent a=2.9,steeper than among normal giants (1.5). Hybrid K II stars are X-rayunderluminous by a factor of 5 to 20 compared to LC III giants at thesame level of normalized CIV flux f_CIV_/f_bol_; hybrid G supergiantsare even more X-ray deficient. We reanalyze the CaII wind dividing lineand find it vertical at B-V=1.45 for LC III giants. It is nearlyhorizontal between B-V=1.45 and 1.0 (at M_bol_=~-2...-3), and not welldefined for supergiants with B-V<1.0. We therefore suggest thatpossibly all LC II and Ib G and K giants are hybrid stars and that the"dividing line" concept in its simplest form is not valid for G/K giantsbrighter than M_bol_=~-2. Hybrid stars are supposed to be evolvedintermediate mass stars and their coronal activity may in principle bedetermined by the individual history of each star.

Добавить новую статью


Внешние ссылки

  • - Внешних ссылок не найдено -
Добавить внешнюю ссылку


Группы:


Наблюдательные данные и астрометрия

Созвездие:Муха
Прямое восхождение:13h32m01.76s
Склонение:-67°34'17.1"
Видимая звёздная величина:8.499
Расстояние:478.469 парсек
Собственное движение RA:-13.4
Собственное движение Dec:-4.1
B-T magnitude:8.643
V-T magnitude:8.511

Каталоги и обозначения:
Собственные имена
HD 1989HD 117400
TYCHO-2 2000TYC 9242-792-1
USNO-A2.0USNO-A2 0150-11866790
HIPHIP 66012

→ Запросить дополнительные каталоги и обозначения от VizieR