اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديد33 Lib - analog of gamma Equ
172
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
In this paper we study periodic variability of the magnetic field in the Ap star 33 Lib. We found that its most probable period equals 83.5 years. There exist also possible shorter periods: 11.036 days, 7.649 days and 4.690 days. Analysis of the magnetic behavior of 33 Lib allows us to conclude, that the star shows the second longest period the slow rotator gamma Equ, the latter star with the period of 97 years.
قيم البحث
اقرأ أيضاً
We determined rotational period of practically nonrotating Ap star gamma Equ and claim $P_{rm rot}= 97$ years. This period is about 35000 times larger than the average rotational period among stars of the same spectral class. Paper discusses possible
mechanism explaining the origin of this phenomenon.
We investigated magnetic variability of the roAp star gamma Equ (HD 201601) with high time resolution. Measurements of the stellar longitudinal magnetic field B_e were performed with the hydrogen line polarimeter and the 6-m optical telescope of Spec
ial Astrophysical Observatory on 20/21 August 1989. We obtained a single 3-hour series of 1720 rapid B_e measurements for this star with the average time resolution of 6.6 sec. The averaged value of <B_e> on this night equals -750 pm 22 G. Both the power spectrum and the amplitude spectrum of the B_e time series essentially are flat. However, they show the presence of a marginally significant magnetic period at P_B = 3.596 min. which is real with the probability 67 %. The amplitude of the magnetic field variations with this period equals 347 pm 31 G. We did not detect variations of B_e field in gamma Equ with the well-known photometric period, P_phot=12.44 min.
A growing number of Be and Oe stars, named the gamma Cas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretio
n disk. To test these scenarios, we carried out a detailed optical monitoring of HD45314, the hottest member of the class of gamma Cas stars, along with dedicated X-ray observations on specific dates. High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties. Over the last four years, HD45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single- and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the H-alpha emission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker. The observed behaviour of HD45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.
Aims. Despite photometry and spectroscopy of its oscillations obtained over the past 25 years, the pulsation frequency spectrum of the rapidly oscillating Ap (roAp) star gamma Equ has remained poorly understood. Better time-series photometry, combine
d with recent advances to incorporate interior magnetic field geometry into pulsational models, enable us to perform improved asteroseismology of this roAp star. Methods. We obtained 19 days of continuous high-precision photometry of gamma Equ with the MOST (Microvariability & Oscillations of STars) satellite. The data were reduced with two different reduction techniques and significant frequencies were identified. Those frequencies were fitted by interpolating a grid of pulsation models that include dipole magnetic fields of various polar strengths. Results. We identify 7 frequencies in gamma Equ that we associate with 5 high-overtone p-modes and 1st and 2nd harmonics of the dominant p-mode. One of the modes and both harmonics are new discoveries for this star. Our best model solution (1.8 M_sun, log T_eff ~ 3.882; polar field strength ~8.1 kG) leads to unique mode identifications for these frequencies (ell = 0, 1, 2 and 4). This is the first purely asteroseismic fit to a grid of magnetic models. We measure amplitude and phase modulation of the primary frequency due to beating with a closely spaced frequency which had never been resolved. This casts doubts on theories that such modulation - unrelated to the rotation of the star - is due to a stochastic excitation mechanism.
We report the discovery of two massive eccentric systems with BRITE data, $tau$ Ori and $tau$ Lib, showing heartbeat effects close to the periastron passage. $tau$ Lib exhibits shallow eclipses that will soon vanish due to the apsidal motion in the s
ystem. In neither system, tidally excited oscillations were detected.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
