اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدIdentifying pulsation modes from two-passband photometry
67
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
I discuss a prospect for mode identification from two-passband photometry of forthcoming BRITE space mission. Examples of photometric diagnostic diagrams are shown for three types of main sequence pulsating variables: $beta$ Cephei, Slowly Pulsating B-type and $delta$ Scuti stars. I consider also taking into account the radial velocity data from simultaneous spectroscopy, which can be carried out from the ground. With such observations, much better discrimination of the spherical harmonic degree, $ell$, can be accomplished and more constraints on stellar parameters and input physics can be derived.
قيم البحث
اقرأ أيضاً
The G9.5 giant eps Oph shows evidence of radial p-mode pulsations in both radial velocity and luminosity. We re-examine the observed frequencies in the photometry and radial velocities and find a best model fit to 18 of the 21 most significant photom
etric frequencies. The observed frequencies are matched to both radial and nonradial modes in the best model fit. The small scatter of the frequencies about the model predicted frequencies indicate that the average lifetimes of the modes could be as long as 10-20d. The best fit model itself, constrained only by the observed frequencies, lies within 1 sigma of eps Ophs position in the HR-diagram and the interferometrically determined radius.
Using CCD photometry obtained by the EROS collaboration in 1991-1993, we have discovered an LMC variable star with a light curve that is oscillating with a mean period of $sim 14$ days and an amplitude of $sim$ 0.3 mag. The oscillations appear with i
rregular amplitude variations. The Fourier spectrum shows that the pulsation of this star is phase locked between two modes of frequencies $f_0$ and 1.5$times f_0$. Moreover, this object has strong $H alpha$ and $H beta$ emission lines and neutral lines of Helium that suggest a spectral type between late O and early B. In a preliminary analysis, we derive a luminosity of $ L=3.4-3.8L_odot$ and an effective temperature in the range $log(T_{eff}) =3.85-4.2$.
The period-luminosity sequences and the multiple periods of luminous red giant stars are examined using the OGLE III catalogue of long-period variables in the Large Magellanic Cloud. It is shown that the period ratios in individual multimode stars ar
e systematically different from the ratios of the periods at a given luminosity of different period-luminosity sequences. This leads to the conclusion that the masses of stars at the same luminosity on the different period-luminosity sequences are different. An evolutionary scenario is used to show that the masses of stars on adjacent sequences differ by about 16-26% at a given luminosity, with the shorter period sequence being more massive. The mass is also shown to vary across each sequence by a similar percentage, with the mass increasing to shorter periods. On one sequence, sequence B, the mass distribution is shown to be bimodal. It is shown that the small amplitude variables on sequences A, A and B pulsate in radial and nonradial modes of angular degree l=0, 1 and 2, with the l=1 mode being the most common. The stars on sequences C and C are predominantly radial pulsators (l=0). Matching period ratios to pulsation models shows that the radial pulsation modes associated with sequences A, A, B, C and C are the 4th, 3rd, 2nd and 1st overtones and the fundamental mode, respectively.
The combination of two-dimensional Dirac surface states with s-wave superconductivity is expected to generate localized topological Majorana zero modes in vortex cores. Putative experimental signatures of these modes have been reported for heterostru
ctures of proximitized topological insulators, iron-based superconductors or certain transition metal dichalcogenides. Despite these efforts, the Majorana nature of the observed excitation is still under debate. We propose to identify the presence of Majorana vortex modes using a non-local transport measurement protocol originally proposed for one-dimensional settings. In the case of an isolated subgap state, the protocol provides a spatial map of the ratio of local charge- and probability-density which offers a clear distinction between Majorana and ordinary fermionic modes. We show that these distinctive features survive in the experimentally relevant case of hybridizing vortex core modes.
V348 Sgr is simultaneously an active hot R Coronae Borealis (RCB) variable, a peculiar extreme helium star, and the hydrogen-deficient central star of a planetary nebula. Explaining the RCB-type variability has been difficult since the star spends mu
ch of its time at minimum light. We present new ground-based multicolour photometry covering 5 observing seasons and 80 days of continuous photometry from space. The latter demonstrate small-amplitude (< 0.01 mag.) variability at maximum light on timescales typical for strange-mode pulsation in hot helium supergiants. These could provide a trigger for frequent dust-production episodes; other mechanisms must also be considered. Multi-colour photometry probes the reddening properties of extinction events from minimum to maximum light. The latter are comparable with extinction events due to carbonaceous grains seen in cooler RCB stars. Minimal reddening at minimum light is indicative that starlight scattered from circumstellar dust into the line of sight dominates transmitted light.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
