相关论文: Asymptotic Giant Branch Variables in NGC 6822

The evolution and lifetimes of thermally pulsating asymptotic giant branch (TP-AGB) stars suffer from significant uncertainties. In this work, we analyze the numbers and luminosity functions of TP-AGB stars in six quiescent, low metallicity…

We have carried out a search for optically visible post-Asymptotic Giant Branch (post-AGB) stars in the Large Magellanic Cloud (LMC). First, we selected candidates with a mid-IR excess and then obtained their optical spectra. We…

We report the discovery of large amplitude X-ray variability in the low luminosity AGN (LLAGN) MGC 7589, and present possible observational evidence for accretion mode transition in this source. Long-term X-ray flux variations by a factor…

J-Branch Asymptotic Giant Branch (JAGB) stars are a photometrically well-defined population of extremely red, intermediate-age AGB stars that are found to have tightly-constrained luminosities in the near-infrared. Based on JK photometry of…

We report on photometric I-band observations of 147 bright (8<I<13) periodic variables toward the Galactic bulge including 76 new discoveries. We used one of the HATnet telescopes to obtain 151 exposures spanning 88 nights in 2005 of an 8.4…

A method of determining ages and masses of asymptotic giant branch (AGB) stars between 0.8 and $\sim$6 M$_\odot$ is demonstrated, based on comparing the star's position in the period--absolute-magnitude diagram to theoretical evolutionary…

We investigate the consequences of magnetic flares on the surface of asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind, in the winds of AGB stars the gas cooling time is much shorter than the outflow time. As a…

We explore the possibility that the short-lived radionuclides $^{26}$Al, $^{60}$Fe, $^{107}$Pd, and $^{182}$Hf inferred to be present in the proto-solar cloud originated from $3-8 M_{\odot}$ Asymptotic Giant Branch (AGB) stars. Models of…

We present a photometric search for objects with point-source components that are optically variable on timescales of weeks--months in the Hubble Ultra Deep Field (HUDF) to i'(AB)=28.0 mag. The data are split into four sub-stacks of…

We report the results of a search for long-period ($100<P<600$ days) periodic variability in SDSS Stripe 82 standards catalog. The SDSS coverage of Stripe 82 enables such a search because there are on average 20 observations per band in…

We present the multi-epoch analysis of 13 variable, nearby (z<0.1), Compton-thin (22<logN_H<24) active galactic nuclei (AGN) selected from the 105-month BAT catalog. Analyzing all available archival soft and hard X-ray observations, we…

The Magellanic Clouds (MCs) offer a unique opportunity to study the stellar evolution and nucleosynthesis of massive Asymptotic Giant Branch (AGB) stars in low metallicity environments where distances are known. Rubidium is a key element to…

30$\%$--50$\%$ of the luminous pulsating red-giant stars show light variations of a longer period than the pulsation periods. Those periods are called long secondary periods (LSP). There has been debated for many years but the origin of the…

We study the cosmic X-ray background (CXB) intensity variations on large angular scales using slew data of the RXTE observatory. We detect intensity variations up to ~2% on angular scales of 20--40deg. These variations are partly correlated…

We report the discovery of 3 new Double Periodic Variables based on the analysis of ASAS-SN light curves: GSD J11630570-510306, V593 Sco and TYC 6939-678-1. These systems have orbital periods between 10 and 20 days and long cycles between…

In this work, a sample of luminous M-type giants in the Baade's Windows towards the inner Galactic Bulge is investigated in the near-infrared. The ISOGAL survey at 7 and 15 micron has given information concerning the mass-loss rates of…

We describe variable stars found in the data collected during the OGLE-III Shallow Survey covering the I-band magnitude range from 9.7 mag to 14.5 mag. The main result is the extension of period--luminosity relations for Cepheids up to 134…

I propose that the mechanism behind the formation of concentric semi-periodic shells found in several planetary nebulae (PNs) and proto-PNs, and around one asymptotic giant branch (AGB) star, is a solar-like magnetic activity cycle in the…

I suggest a theoretical quantitative definition for the termination of the asymptotic giant branch (AGB) phase and the beginning of the post-AGB phase. I suggest that the transition will be taken to occur when the ratio of the dynamical…

As shown by Mennickent, et al(2003), a subset of the blue variable stars in the Large Magellanic Cloud exhibit brightness variability of small amplitude in the period range 2.4 to 16 days as well as larger amplitude variability with periods…