اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدHD 174005: another binary classified as lambda Boo
89
0
0.0
(
0
)
تأليف
R. Faraggiana
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We demonstrate that HD 174005, a star recently classified as belonging to the lambda Boo group, is in reality a double lined spectroscopic binary; at some phases, the observed composite spectrum may be similar to that of a single star with weak metal lines.
قيم البحث
اقرأ أيضاً
We examine the large sample of lambda Boo candidates collected in Table 1 of Gerbaldi et al. (2003) to see how many of them show composite spectra. Of the 132 lambda Boo candidates we identify 22 which definitely show composite spectra and 15 more fo
r which there are good reasons to suspect a composite spectrum. The percentage of lambda Boo candidates with composite spectra is therefore > 17 and possibly considerably higher. For such stars the lambda Boo classification should be reconsidered taking into account the fact that their spectra are composite. We argue that some of the underabundances reported in the literature may simply be the result of the failure to consider the composite nature of the spectra. This leads to the legitimate suspicion that some, if not all, the lambda Boo candidates are not chemically peculiar at all. A thorough analysis of even a single one of the lambda Boo candidates with composite spectra, in which the composite nature of the spectrum is duly considered, which would demonstrate that the chemical peculiarities persist, would clear the doubt we presently have that the stars with composite spectra may not be lambda Boo at all.
The abundance anomalies in lambda Boo stars are popularly explained by element-specific mass inflows at rates that are much greater than empirically-inferred bounds for interstellar accretion. Therefore, a lambda Boo stars thin outer envelope must de
rive from a companion star, planet, analogs to Kuiper Belt Objects or a circumstellar disk. Because radiation pressure on gas-phase ions might selectively allow the accretion of carbon, nitrogen, and oxygen and inhibit the inflow of elements such as iron, the source of the acquired matter need not contain dust. We propose that at least some lambda Boo stars accrete from the winds of hot Jupiters.
The selective abundance of C, N, O (almost solar) with respect to that of other elements (underabundant) in lambda Boo stars has been interpreted as a characteristic peculiarity of these objects, when considered as single stars. We show here that a s
imilar selective abundance is predicted from the composite spectra resulting from two unresolved stars in the same temperature range as the lambda Boo stars.
The preliminary results of a 1996 multisite campaign on the pulsating lambda Bootis star 29 Cyg are presented. This campaign, initiated by the Central Asian Network (CAN), allowed to collect data during 48 photometric and 2 spectroscopic nights at ob
servatories of Ukraine, Kazakhstan, Turkey, Hungary, Canada and USA. The multiplicity of excited modes is confirmed in both spectroscopy and photometry. The analysis of all 1995 and 1996 data, combined with new CAN observations made in July-October 1997, is under way.
A short period eclipsing binary star CV Boo is tested for the possible existence of additional bodies in the system with a help of the light equation method. We use data on the moments of minima from the literature as well as from our observations du
ring 2014 May--July. A variation of the CV Boos orbital period is found with a period of $approx 75$ d. This variation can be explained by the influence of a third star with a mass of $approx 0.4M_{odot}$ in an eccentric orbit with $eapprox 0.9$. A possibility that the orbital period changes on long time scales is discussed. The suggested tertiary companion is near the chaotic zone around the central binary, so CV Boo represents an interesting example to test its dynamical evolution. A list of 14 minima moments of the binary obtained from our observations is presented.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
