相关论文: Phase-lag Distances of OH Masing AGB Stars

Variable OH/IR stars are Asymptotic Giant Branch (AGB) stars with an optically thick circumstellar envelope that emit strong OH 1612 MHz emission. They are commonly observed throughout the Galaxy but also in the LMC and SMC. Hence, the…

We have pioneered a new method for the measurement of extragalactic distances. This method uses the time-lag between variations in the short wavelength and long wavelength light from an active galactic nucleus (AGN), based on a quantitative…

Aims: Accurate distances to evolved stars with high mass loss rates are needed for studies of many of their fundamental properties. However, as these stars are heavily obscured and variable, optical and infrared astrometry is unable to…

We conducted radio observations searching for OH 18-cm maser emission from a sample of 169 unclassified MIPSGAL compact Galactic bubbles. These sources are thought to be the circumstellar envelopes of different kinds of evolved stars. Our…

The observed SEDs of a sample of 60 OH/IR stars are fitted using a radiative transfer model of a dusty envelope. Among the whole sample, 21 stars have reliable phase-lag distances while the others have less accurate distances. L*-P,Mlr-P…

Stars on the asymptotic giant branch (AGB) play important roles in a number of astronomical contexts. To quantify these roles, it is necessary to establish the mass-loss characteristics of stars as they evolve up and beyond the AGB. We used…

The HI line at 21 cm is a tracer of circumstellar matter around AGB stars, and especially of the matter located at large distances (0.1-1 pc) from the central stars. It can give unique information on the kinematics and on the physical…

Light variation of the 47 AGB star candidates in the outer Galactic disk has been monitored at I-band for 5 years. Periods were determined well for 18 of them and less reliably for the other 25. The average period of the objects is then 500…

To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of…

Estimating the distances to asymptotic giant branch (AGB) stars using optical measurements of their parallaxes is not straightforward because of the large uncertainties introduced by their dusty envelopes, their large angular sizes, and…

We report the results of an exploratory program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered galactic light. The goal is to characterize the morphology of the envelopes as a probe of…

Circumstellar shells around AGB stars are built over long periods of time that may reach several million years. They may therefore be extended over large sizes (~1 pc, possibly more), and different complementary tracers are needed to…

Context: A large fraction of otherwise similar asymptotic giant branch stars (AGB) do not show OH maser emission. As shown recently, a restricted lifetime may give a natural explanation as to why only part of any sample emits maser emission…

Asymptotic Giant Branch (AGB) stars are good tracers of the Galactic structure. They are bright in the infrared and can therefore be detected even in the most obscured regions of the Galaxy. Maser emission from their circumstellar envelopes…

Context: Ground-state OH maser emission from late-type stars is usually polarized and remains a powerful probe of the magnetic field structure in the outer regions of circumstellar envelopes if observed with high angular and spectral…

We investigate the molecular and dusty environment of OH/IR stars in order to characterize the mass-loss process during the tip-AGB superwind phase. Employing the AMBER instrument at the VLT Interferometer we obtained near-infrared H- and…

In the radio regime the mass-loss rate of AGB stars is best probed using molecular (and atomic) line emission arising in the CSE formed by the stellar wind. The numerical modelling of the circumstellar emission where intricate interplays…

Aim: The late stages of stellar evolution are mainly governed by the mass of the stars. Low- and intermediate-mass stars lose copious amounts of mass during the asymptotic giant branch (AGB) which obscure the central star making it…

We report on the measurement of the trigonometric parallaxes of 1612 MHz hydroxyl masers around two asymptotic giant branch stars, WX Psc and OH138.0+7.2, using the NRAO Very Long Baseline Array with in-beam phase referencing calibration.…

Using 766 compact objects from a survey of the galactic Plane in the 1612-MHz OH line, new light is cast on the infrared properties of evolved stars on the TP-AGB and beyond. The usual mid-infrared selection criteria, based on IRAS colours,…