اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدPreliminary results of dark-speckle stellar coronography
111
0
0.0
(
0
)
تأليف
A. Boccaletti DESPA
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The dark-speckle method (Labeyrie 1995) combines features of speckle interferometry and adaptive optics to provide images of faint circumstellar material. We present preliminary results of observations, and simulations concluding to the feasibility of exo-planet imaging from the ground. Laboratory simulations with an avalanche photodiode indicate the detectability of a stellar companion of relative intensity 10^{-6} at 5 Airy radii from the star. New, more general, expressions for the signal-to-noise ratio and integration time are given. Comparisons with direct long-exposure imaging indicate that the method improves the detectability of circumstellar nebulosity, faint companions and planets.
قيم البحث
اقرأ أيضاً
We present a preliminary analysis of the photospheric activity of CoRoT-Exo-2a, a young G7V star accompanied by a transiting hot Jupiter recently discovered by CoRoT. We apply spot modelling techniques developed for the analysis of the Sun as a star
and capable to extract from CoRoT high precision light curves information on the variation of the total spotted area and the longitude of active regions along the 142 days of the observations. This preliminary analysis shows that the active regions form within two active longitudes separated by about 180 degrees and rotating with periods of 4.5221 and 4.5543 days, respectively, and that the total spotted area oscillates with a period of about 28.9 days.
We show the preliminary results of the application of our fireshell model to GRB060124. This source is very peculiar because it is the first event for which both the prompt and the afterglow emission were observed simultaneously by the three Swift in
struments: BAT (15-350 keV), XRT (0.2-10 keV) and UVOT (170-650 nm), due to the presence of a precursor ~ 570 s before the main burst. We analyze GRB060124 within our canonical GRB scenario, identifying the precursor with the P-GRB and the prompt emission with the afterglow peak emission. In this way we reproduce correctly the energetics of both these two components. We reproduce also the observed time delay between the precursor (P-GRB) and the main burst. The effect of such a time delay in our model will be discussed.
Although not designed as an astrometric instrument, Kepler is expected to produce astrometric results of a quality appropriate to support many of the astrophysical investigations enabled by its photometric results. On the basis of data collected duri
ng the first few months of operation, the astrometric precision for a single 30 minute measure appears to be better than 4 milliarcseconds (0.001 pixel). Solutions for stellar parallax and proper motions await more observations, but the analysis of the astrometric residuals from a local solution in the vicinity of a star have already proved to be an important tool in the process of confirming the hypothesis of a planetary transit.
Due to its unique long-term coverage and high photometric precision, observations from the Kepler asteroseismic investigation will provide us with the possibility to sound stellar cycles in a number of solar-type stars with asteroseismology. By compa
ring these measurements with conventional ground-based chromospheric activity measurements we might be able to increase our understanding of the relation between the chromospheric changes and the changes in the eigenmodes. In parallel with the Kepler observations we have therefore started a programme at the Nordic Optical Telescope to observe and monitor chromospheric activity in the stars that are most likely to be selected for observations for the whole satellite mission. The ground-based observations presented here can be used both to guide the selection of the special Kepler targets and as the first step in a monitoring programme for stellar cycles. Also, the chromospheric activity measurements obtained from the ground-based observations can be compared with stellar parameters such as ages and rotation in order to improve stellar evolution models.
We study the prospect of using TianQin to detect stellar-mass binary black holes (SBBHs). We estimate the expected detection number as well as the precision of parameter estimation on SBBH inspirals, using five different population models. We note Ti
anQin can possibly detect a few SBBH inspirals with signal to noise ratios greater than 12; lowering the threshold and combining multiple detectors can both boost the detection number. The source parameters can be recovered with good precision for most events above the detection threshold. For example, the precision of the merger time most likely occurs near 1s, making it possible to guide the detection of the ground-based detectors, the precision of the eccentricity $e_0$ most likely occurs near $10^{-4}$, making it possible to distinguish the formation channels, and the precision of the mass parameter is better than $10^{-6}$ in general and most likely occurs near $10^{-7}$. We note, in particular, that for a typical merger event, the error volume is likely to be small enough to contain only the host galaxy, which could greatly help in the study of gravitational wave cosmology and relevant studies through the multimessenger observation.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
