Gamma-ray line emission from radioactive decay of 60Fe provides constraints on nucleosynthesis in massive stars and supernovae. We detect the γ-ray lines from 60Fe decay at 1173 and 1333 keV using three years of data from the spectrometer SPI on board INTEGRAL. The average flux per line is (4.4 ± 0.9) × 10−5 ph cm−2 s−1 rad−1 for the inner Galaxy region. Deriving the Galactic 26Al gamma-ray line flux with using the same set of observations and analysis method, we determine the flux ratio of 60Fe/26Al gamma-rays as 0.15 ± 0.05. We discuss the implications of these results for the widely-held hypothesis that 60Fe is synthesized in core-collapse supernovae, and also for the closely-related question of the precise origin of 26Al in massive stars.

Spectrophotometric observations of the complete sample of twenty four blue stragglers (BSs) in the old galactic open cluster M67 (NGC2682) have been collected, using the Guillermo Haro Observatory in Cananea, Mexico. All the calibrated spectra were re-calibrated by the Beijing Arizona Taipei Connecticut (BATC) photometric system which includes fluxes in 11 photometric bands covering ~3600–10000 Å. The goal of the current work is to provide observational constraints on spectral properties of BSs by determining the effective temperature (Teff) and surface gravity (log g). The overall results, obtained by applying the flux fitting method, indicate that Teff and surface gravities of BSs in M67 are fully compatible with those expected for main sequence stars.

With the Mie theory and the radiative transfer model, we studied the effect of dust size on the infrared color indexes concerning special filters used in the space infrared missions and typical filters in the near-infrared, of AGB stars with typical oxygen-rich and carbon-rich dust shells. It is found the most affected bands are the near-infrared bands JHK and the Spitzer IRAC bands, meanwhile the wavebands with reference wavelength longer than 10 μm is little affected. The effect increases fast with the mass loss rate. We also discussed the potential to distinguish the O-rich and C-rich dusts, and the difference in IR colors between the AGB stars and other IR sources like YSOs and galaxies.

We report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. We show that the durations of Swift bursts also have two log-normal distributions that are clearly divided at T90 = 2 s. Their intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value compared with the observed one. This study confirms the spectra of short GRBs are in general harder than the long GRBs and shows that this trend becomes weak in the source frame.

Using a self-consistant dynamic theory of non-local convection in chemically inhomogeneous stars, the lithium depletion in MS stars of masses 0.725–1.5 M⊙ are calculated. Both of the overshooting and microdiffusion are included in a consistent way. The comparisons of theretical reasults with the observed Li depletions in open clusters show that the general characters of Li depletions can be reproduced by theory. The overshooting mixing and microdiffusion induced by gravitational setting and radiative accelerations may be two main mechanisms of Li depletion.

The standard model of stellar structure is unable to account for various observational facts, and there is now a large consensus that some ‘extra mixing’ must occur in the radiation zones. The possible causes for such mixing are briefly reviewed. The most efficient among them is probably the shear-turbulence generated by the differential rotation, which itself results from the transport of angular momentum that can be mediated through the large-scale circulation induced by structural adjustments or by the applied torques (stellar wind, accretion, tides). In solar-type stars this angular momentum transport is ensured mainly by internal gravity waves that are excited at the boundary with convection zones. Another cause of mixing manifests itself in the red giant phase, namely the thermohaline instability due to an inversion of the molecular weight gradient. The implementation of these processes in stellar evolution codes is giving rise to a new generation of stellar models, which are in much better agreement with the observational constraints.

Helioseismological data have given us two interesting results: the differential-to-uniform solar rotation curve and the extent of the overshooting region (OV). As of today, no model (including numerical simulations) has been able to reproduce these findings. Here, we first present a new model for the angular momentum. It contains new terms representing vorticity and buoyancy that were left out in all previous formulations without a clear justification. It is shown that they extract angular momentum from the stellar core, a welcome feature since the standard angular momentum equation leads to a rotation curve that is considerably higher than what is observed. As for the overshooting extent, all models yield values that are an order of magnitude larger than the helio data of 0.07Hp. We propose a criterion whose main ingredient is a new flux conservation law that includes new terms, one of which increases the dissipation in the radiative zone and thus lowers the OV extent, a tendency in the desired direction. Since we have not coupled the new models to a solar structure-evolution code, we cannot at this stage carry out a comparison with the helio data. The purpose is to exhibit the fact that in both cases the missing ingredients are of such nature as to improve the previous model predictions. A proper quantification remains to be done.

We investigate the tidal disruption of a red giant whose envelope is thought to be stripped off when it passed by a massive black hole. Since the low-density stellar envelope would be lost, the tidal disruption of a red giant by massive black hole is regarded as primarily happening in its core region. The object is called a stripped red giant (SRG). Comparing our results with the three candidate tidal disruption events detected by Chandra in 2001 and 2002, i.e., the X-ray flares of NGC 5905, RX J1242.6-1119A, and RX J1624.9+7554, we argue that the tidal disruption of a stripped red giant is strongly ruled out.

Asteroseismology, as a tool to use the indirect information contained in stellar oscillations to probe the stellar interiors, is an active field of research presently. Stellar age, as a fundamental property of star apart from its mass, is most difficult to estimate. In addition, the estimating of stellar age can provide the chance to study the time evolution of astronomical phenomena. In our poster, we summarize our previous work and further present a method to determine age of low-mass main-sequence star.

For solar and stellar modeling, a high-quality equation of state is crucial. But the inverse is also true: the astrophysical data (helioseismic today, asteroseismic tomorrow) put constraints on the physical formalisms, making the Sun and the stars laboratories for plasma physics. One of the main astrophysical benefits from a good equation of state is an improved abundance determination. Recent theoretical progress in the equation of state has involved both rigorous and phenomenological approaches, giving the user a considerable choice.

New 2D dynamical models for the winds of AGB stars are presented which include hydrodynamics with radiation pressure on dust, equilibrium chemistry, time-dependent dust formation theory, and coupled frequency-dependent Monte Carlo radiative transfer. The simulations reveal a much more complicated picture of the dust formation and wind acceleration as compared to 1D spherical wind models. Triggered by non-spherical pulsations or large-scale convective motions, dust forms event-like in the cooler regions above the stellar surface which are temporarily less illuminated, followed by the radial ejection of dust arcs and clumps. These simulations can possibly explain recent high angular resolution interferometric IR observations of red giants, which show an often non-symmetric and highly time-variable innermost dust formation and wind acceleration zone. The dependence of the mass-loss rates on stellar parameters is less threshold-like as used from 1D models, and therefore, it seems quite possible that the phenomenon of dust-driven winds may occur also in less evolved red giants.

We report on the development of a new stellar evolution code, and provide a taste of results, showing its capability to calculate full evolutionary tracks for a wide range of masses and metalicities. The code is fast and efficient, and is capable of following through all evolutionary phases, including core/shell flashes and thermal pulses, without any interruption or intervention. It is meant to be used also in the context of modeling the evolution of dense stellar systems, for performing live calculations for both ‘normal’ ZAMS/PRE-MS models, but mainly for ‘non-canonical’ stellar configurations (i.e. merger-products). We show a few examples of evolutionary calculations for stellar populations I and II, and for masses in the range 0.25–64 M⊙.

The discovery of the extremely luminous supernova SN 2006gy, possibly interpreted as a pair instability supernova, renewed the interest in very massive stars. We explore the evolution of these objects, which end their life as pair instability supernovae or as core collapse supernovae with relatively massive iron cores, up to about 3 M⊙.

Observations of the rotation periods of cool open cluster stars display a distinctive dichotomy when plotted against stellar mass/color. Other measures of stellar activity are also known to be dependent on stellar mass and structure, especially the onset and characteristics of convection zones. One proposal for understanding the observed rotation period dichotomy suggested dependencies on the moment of inertia of either the whole star or that of only the outer convection zone (Barnes 2003).

The moment of inertia of stars with the mass between 0.1Msun and 3.0Msun have been calculated using a version of Yale Stellar evolution code (aka YREC). Each star has been evolved from stellar birthline to the onset of the core He burning. For easy comparison to observations, we have calculated the isochrones of these quantities as well as the convective turnover time, of interest to the activity community.

Although chemical separation is generally accepted as the main physical process responsible for the anomalous surface abundances of AmFm stars, its exact behavior within the interior of these stars is still uncertain. We will explore two hydrodynamical processes which could compete with atomic diffusion: mass loss and turbulence. We will also discuss the extent to which separation occurs immediately below the surface convection zone as well as the extent to which separation occurs below 200,000 K. To do so, self-consistent stellar models with mass loss and turbulence where calculated using the Montreal stellar evolution code and compared to observations of A and F stars. It is shown that to the precision of observations available for F stars, a mass loss rate of 2×10−14M⊙ · yr−1, is compatible with observations and that no turbulence is then required.

We positionally cross-identified FIRST (the Faint Images of the Radio Sky at Twenty centimeters) catalogue with 2MASS (the Two Micron All Sky Survey) pointed-source database and collected the data from radio band and near infrared band. Then the data were cross-matched with the Véron-Cetty & Véron 2006 catalog and the Tycho-2 catalog, respectively. Therefore the known samples of quasars and stars are obtained. We applied principal component analysis (PCA) on the known sample. The overall sample may be projected in the principal component space. From the space, we can easily locate the area that radio stars occupy, and select out radio star candidates. With the follow-up observation of these candidates, the properties of radio stars may be studied.

The diffuse interstellar bands appear as absorption features in spectra of reddened stars and lie mostly in the visible region of the spectrum. The first examples were recorded photographically nearly one hundred years ago and despite a huge amount of observational, theoretical and laboratory effort the spectra remain unassigned. Most researchers believe that organic material is responsible for the absorptions, the most popular form being polycyclic aromatic (hydro)carbon (PAH) structures. This article reviews briefly the main characteristics of the spectrum, describes some current research and outlines some lines of inquiry.

It is known since long ago that in comets a large quantity of organic matter exists in form of grains or is embedded in silicate grains. This was detected in situ by cometary space missions as well as inferred as a distributed source of some molecules observed in comets. Since organic matter is rather volatile, finding slow sublimating grains in comets can be good evidence of organics as a constituent of such grains. Here we describe a method to detect sublimating grains in comets. It consists of specific observations, specific data analysis, and some light-scattering modeling. We detect sublimating grains by measuring the quantity of grains as a function of the nucleocentric distance. Once detected, it is possible to get their photometric characteristics and compare them with the results of light-scattering modeling. The method has been applied to several comets. Sublimating grains were reliably identified for two of them.

We present the first semi-analytical model that follows the chemical evolution during the collapse of a molecular cloud and the formation of a low-mass star and the surrounding disk. It computes infall trajectories from any starting point in the cloud and it includes a full time-dependent treatment of the temperature structure. We focus here on the freeze-out and desorption of CO and H2O. Both species deplete towards the centre before the collapse begins. CO evaporates during the infall phase and re-adsorbs when it enters the disk. H2O remains in the solid phase everywhere, except within a few AU of the star. Material that ends up in the planet- and comet-forming zones is predicted to spend enough time in a warm zone during the collapse to form complex organic species.

We investigate the molecular abundances in protostellar cores by solving the gas-grain chemical reaction network. As a physical model of the core, we adopt a result of one-dimensional radiation-hydrodynamics calculation, which follows the contraction of an initially hydrostatic prestellar core to form a protostellar core. Temporal variation of molecular abundances is solved in multiple infalling shells, which enable us to investigate the spatial distribution of molecules in the evolving core. The shells pass through the warm region of T ~ 20–100 K in several 104 yr and falls onto the central star in ~100 yr after they enter the region of T > 100 K. We found that the complex organic species such as HCOOCH3 are formed mainly via grain-surface reactions at T ~ 20–40 K, and then sublimated to the gas phase when the shell temperature reaches their sublimation temperatures (T ≥ 100 K). Carbon-chain species can be re-generated from sublimated CH4 via gas-phase and grain-surface reactions. HCO2+, which is recently detected towards L1527, are abundant at r = 100–2,000 AU, and its column density reaches ~1011 cm−2 in our model. If a core is isolated and irradiated directly by interstellar UV radiation, photo-dissociation of water ice produces OH, which reacts with CO to form CO2 efficiently. Complex species then become less abundant compared with the case of embedded core in ambient clouds. Although a circumstellar (protoplanetary) disk is not included in our core model, we can expect similar chemical reactions (i.e., production of large organic species, carbon-chains and HCO2+) to proceed in disk regions with T ~ 20–100 K.