We present an 86 GHz SiO (v = 1, J = 2 -> 1) maser search toward late-type stars located within vertical bar b vertical bar < 0 degrees.5 and 20 degrees < l < 50 degrees. This search is an extension at longer longitudes of a previously published work. We selected 135 stars from the MSX catalog using color and flux criteria and detected 92 (86 new detections). The detection rate is 68%, the same as in our previous study. The last few decades have seen the publication of several catalogs of point sources detected in infrared surveys (MSX, 2MASS, DENIS, ISOGAL, WISE, GLIMPSE, AKARI, and MIPSGAL). We searched each catalog for data on the 444 targets of our earlier survey and for the 135 in the survey reported here. We confirm that, as anticipated, most of our targets have colors typical of oxygen-rich asymptotic giant branch (AGB) stars. Only one target star may have already left the AGB. Ten stars have colors typical of carbon-rich stars, meaning a contamination of our sample with carbon stars less than or similar to 1.7%.

Maser stars have been found with radial velocities up to +350 km s(-1) and down to -350 km s(-1) and exclusively within a few degrees from the Galactic centre. They form two spatially separated streams: one stream is at positive longitudes and consists of stars going away from us and the other is at negative longitudes consisting of stars approaching us. I show that closed orbits in a simple mass model for the bar explain quantitatively the existence of the two streams and the velocities observed. The mass of the bar is estimated on dynamical grounds: 3 x 10(10) M-sun.

We have selected a homogeneous sample of asymptotic giant branch (AGB) stars in the Galactic bulge population from the ISOGAL survey. Our target stars cover a wide range of mass-loss rates (similar to 10(-8)-10(-4) M-circle dot yr(-1)) and differ primarily by their age on the AGB. This homogeneous sample is thus ideally suited to study the dust formation process as a function of age on the AGB. We observed our sample with Spitzer-Infrared Spectrograph, and studied the overall properties of the infrared spectra of these targets. The analysis is complicated by the presence of strong and variable background emission, and the extracted infrared AGB star spectra are affected by interstellar extinction. Several stars in our sample have no detectable dust emission, and we used these 'naked stars' to characterize the stellar and molecular contributions to the infrared spectra of our target stars. The resulting dust spectra of our targets do indeed show significant variety in their spectral appearance, pointing to differing dust compositions for the targets. We classify the spectra based on the shape of their 10-mu m emission following the scheme by Sloan & Price. We find that the early silicate emission classes associated with oxide dust are generally under-represented in our sample due to extinction effects. We also find a weak 13-mu m dust feature in two of our otherwise naked star spectra, suggesting that the carrier of this feature could potentially be the first condensate in the sequence of dust condensation.

The article by Kessler et al. was the introductory paper to a special issue of AA IRAS was more than a timely mission, it was overdue. Already in the very first plans for IRAS, it had been decided that IRAS should make a whole-sky survey and should not be driven by any program chosen in advance. This clearly was the right decision.

We present first results of a program with the integral field spectrometer SINFONI on the ESO-VLT (Very Large Telescope) Yepun to observe obscured stellar clusters in HII regions in the infrared H and K bands with the goals of obtaining a more complete and less biased picture of the Milky Way's spiral structure, and of improving our understanding of the spatial distribution of Galactic HII regions. The classification in spectral subclasses of early type stars together with the extinction determination and the stellar apparent magnitudes enable us to obtain spectrophotometric distances, which are independent and complementary to kinematic distances and free from the ambiguity inherent to the latters' determination. Most importantly, our method is much less limited by interstellar extinction than previous optical programmes, allowing studies along lines of sight where optical measurements are impossible.

Dust radiative transfer models are presented for 60 carbon stars in the Magellanic Clouds (MCs) for which 5-35 mu m Spitzer infrared spectrograph (IRS) spectra and quasi-simultaneous ground-based JHKL photometry are available. From the modelling, the luminosity and mass-loss rate are derived (under the assumption of a fixed expansion velocity and dust-to-gas ratio), and the ratio of silicon carbide (SiC) to amorphous carbon (AMC) dust is also derived. This ratio is smaller than observed in Galactic carbon stars, as has been noted before. Light curves for 36 objects can be retrieved from the massive compact halo object (MACHO) and optical gravitational lensing experiment (OGLE) data bases, and periods can be derived for all but two of these. Including data from the literature, periods are available for 53 stars.There is significant scatter in a diagram where the mass-loss rates are plotted against luminosity, and this is partly due to the fact that the luminosities are derived from single-epoch data. The mass-loss rates for the MC objects roughly scatter around the mean relation for Galactic C-stars.The situation is better defined when the mass-loss rate is plotted against pulsation period. For a given period, most of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) stars have mass-loss rates that are in agreement with that observed in Galactic carbon stars (under the assumption that these objects have an expansion velocity and dust-to-gas ratio typical of the mean observed in Galactic carbon Miras).For some SMC sources only, the IRS spectrum at longer wavelengths falls clearly below the model flux predicted by a constant mass-loss rate. An alternative model with a substantial increase of the mass-loss rate to its present-day value over a time-scale of a few tens of years is able to explain the spectral energy distribution (SED) and IRS spectra of these sources. However, the probability to have two such cases in a sample of 60 is small, and makes this not a likely explanation (and testable by re-observing these objects near the end of the lifetime of Spitzer). Alternative explanations are (ad hoc) changes to the dust emissivity at longer wavelengths, and/or deviations from spherical symmetry.

We present new mass-loss rates for AGB stars derived from fitting circumstellar dust models to the spectral energy distributions from I to 35 mu m of 26 LMC stars and 14 SMC stars. It is found that for pulsation periods greater than 500 days, there is a very tight correlation of mass-loss rate with pulsation period, but for shorter periods there is a large dispersion in the mass-loss rate. The new results are compared to some commonly used mass-loss formulations.

Aims. We investigate the intermediate-age asymptotic giant branch stellar population of two Local Group dwarf irregular galaxies to characterize their carbon star population in near-infrared (IR).Methods. Our work is based on near-IR photometry complemented with optical ground based and Hubble Space Telescope (HST) photometry. Near-IR photometry is based on our and archival J and Ks-band images from SOFI near-IR array of the ESO New Technology Telescope (NTT). Optical photometry for DDO 210 is from the EMMI optical imager of ESO NTT, while the SagDIG optical data come from Momany et al. (2005, A&A, 439, 111).Results. We show that near- IR photometry is a very powerful tool for carbon star detection. We recovered two out of three previously-known carbon stars in DDO 210 and discovered six additional objects in this galaxy which have optical and near- IR colors consistent with carbon giants. This brings the total number of bona fide C-star candidates in DDO 210 to nine. However, to confirm the nature of these objects additional higher spatial resolution imaging or spectroscopic data are necessary.We detected a large population of C-star candidates in SagDIG, 18 of which were previously identified in Demers & Battinelli ( 2002, AJ, 123, 238) and Cook ( 1987, Ph. D. Thesis), and six new bona fide carbon stars. We present their optical and near- IR colors and use their luminosity function to put constraints on the star formation history (SFH) in this dwarf irregular galaxy.

We derive the distribution of maser stars in the inner Milky Way (MW) based on an analysis of lV-diagrams (lVd) for two samples of maser stars: 771 OH/IR stars and 363 SiO-maser stars. They are all close to the plane of the MW and have long. from -45 to +45deg. The two lVds are compared and found to be very similar. They also compare well with the lVd of interstellar CO, but there are significant differences in detail between the stellar lVds and that of the ISM. Based on the qualitative discussion we divide the lVds into seven areas. In each area we compare the number of stars observed with those predicted by an assumed set of orbits in a galactic potential. This potential is axially symmetric but a weak rotating bar has been added. We conclude that the maser stars move on almost circular orbits outside of about 3.5 kpc, but that the orbits become more and more elongated when one goes deep inside our MW. We find a strong effect of the Corotation (CR) resonance (res) at 3.3 kpc, we see a small but noticeable effect of the Outer Lindblad res at 5 kpc and no effect of the Inner Lindblad res at r=0.8 kpc. We find a set of 6 groups of orbits that together predict counts in agreement with the counts of stars observed. We then calculate the trajectory of each orbit and so find the distribution of the maser stars in the plane of the MWG. This distribution has two new (but not unexpected) features. The first is a bar-like distribution within 2 kpc from the GC outlined. These orbits explain the high-vel stars near l=0deg in the forbidden and the permitted quadrants. The second feature are two "croissant"-like voids in the distribution close to the CR radius (3.3 kpc), which are the consequence of the presence of the CR res. We find excellent agreement with an earlier reconstruction by Sevenster (1999).

Regions of different metallicity have been identified in the Magellanic Clouds by using the ratio between Asymptotic Giant Branch stars of spectral type C and M. In the Large Magellanic Cloud the ratio appears to decrease radially while in the Small Magellanic Cloud (SMC) there is no clear trend, reflecting either the large extension of the SMC along the line of sight or a more complex star formation history. The distribution of the C/M ratio is clumpy and corresponds to a spread in (Fe/H) of 0.75 dex in both Clouds. There is an indication of increasing C/M ratio, thus decreasing metallicity, towards the Bridge region connecting the two Clouds.

Aims. To study the nature of Bulge AGB stars and in particular their circumstellar dust, we have analysed mid-infrared spectra obtained with the ISOCAM CVF spectrometer in three Bulge fields. Methods. The ISOCAM 5–16.5 µm CVF spectra were obtained as part of the ISOGAL infrared survey of the inner Galaxy. A classification of the shape of the 10 µm dust feature was made for each case. The spectra of the individual sources were modelled using a radiative transfer model. Different combinations of amorphous silicates and aluminium-oxide dust were used in the modelling. Results. Spectra were obtained for 29 sources of which 26 are likely to be Bulge AGB stars. Our modelling shows that the stars suffer mass loss rates in the range of 10 −8 −5 × 10 −7 M� /yr, which is at the low end of the mass-loss rates experienced on the thermally %

We investigate the molecular bands in carbon-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), using the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope (SST) over the 5-38 mu m range. All 26 low-resolution spectra show acetylene (C2H2) bands at 7 and 14 mu m. The hydrogen cyanide (HCN) bands at these wavelengths are very weak or absent. This is consistent with low nitrogen abundances in the LMC. The observed 14 mu m C2H2 band is reasonably reproduced by an excitation temperature of 500 K. There is no clear dilution of the 14 mu m C2H2 band by circumstellar dust emission. This 14-mu m band originates from molecular gas in the circumstellar envelope in these high mass-loss rate stars, in agreement with previous findings for Galactic stars. The C2H2 column density, derived from the 13.7 mu m band, shows a gas mass-loss rate in the range 3 x 10(-6) to 5 x 10(-5) M-circle dot yr(-1). This is comparable with the total mass-loss rate of these stars estimated from the spectral energy distribution. Additionally, we compare the line strengths of the 13.7 mu m C2H2 band of our LMC sample with those of a Galactic sample. Despite the low metallicity of the LMC, there is no clear difference in the C2H2 abundance among LMC and Galactic stars. This reflects the effect of the third dredge-up bringing self-produced carbon to the surface, leading to high carbon-to-oxygen ratio at low metallicity.

A pilot project is carried out to measure circumstellar CO emission from three OH/IR, stars close to the GC using the Nobeyama Millimeter Array at 115 GHz and the Sub-Millimeter Array at 230 GHz. An interferometer is necessary as a 'spatial filter' in this region of space because of the confusion with interstellar CO emission. The intention is to find out whether it is possible to later conduct a large-scale survey for mass-loss rates using, for example, ALMA. Thus an important parameter would be added to our understanding of the evolution of the Galactic Bulge. Sources have been detected towards two of the stars with 'correct' positions and radial velocities. However, for one of the stars the line profile is not what one expects for expanding circumstellar envelopes. This surprising result is discussed and our plans for future observations are presented.

With the William Herschel Telescope in La Palma we made IJK(s) observations of an area of about 40' x 30' of the Local Group galaxy Draco. This allows us to describe Draco's late-type stellar population across the whole galaxy at a photometric level 2 mag deeper than the 2MASS survey. We detected the red giant branch (RGB) and measured the magnitude of the tip of the RGB in the three bands. From that in the I band we obtain a distance modulus of (m - M)(0) = 19.49 +/- 0.06(stat) +/- 0.15(sys), in excellent agreement with a measurement from RR Lyrae stars. The peak of the (J - K-s)(0) histogram at different MKs suggests that Draco has a mean [Fe/H] = - 1.95 +/- 1.26 while fiducial RGB tracks of Galactic globular clusters indicate a mean [Fe/H] = - 1.33 +/- 0.72 where the error corresponds to the spread around the mean value. There are significant differences between the colour - magnitude diagrams of stars in the inner, medium and outer areas of the galaxy. A metal poor (Z = 0.0004) intermediate-age population ( about 1.6 Gyr old) is clearly present and emerges in particular between 6' and 12' from the centre of the galaxy. A few additional carbon star candidates have been identified from both their location in the colour - magnitude diagram and from an indication of variability. The large scale distribution of late-type stars is smooth but irregular in shape; this points at a variation of inclination with radius.

We have determined extinction corrections for a sample of 441 late-type stars in the inner Galaxy, which we previously searched for SiO maser emission, using the 2MASS near-infrared photometry of the surrounding stars. From this, the near-infrared extinction law is found to be approximated by a power law A A λ -1.9±0.1 , Near- and mid-infrared colour-colour properties of known Mira stars are reviewed. From the distribution of the dereddened infrared colours of the SiO target stars we infer mass-loss rates between 10 -7 and 10 -5 M ○. yr -1 .

Observations in the IJK(s) wave bands covering the central 20' x 20' of the Local Group galaxy NGC 6822 have been made with the William Herschel Telescope in La Palma. They have allowed us to characterize, for the first time in the near-infrared across the whole galaxy, its late-type stellar population (i.e. red giant and asymptotic giant branch stars) and to derive from the ratio between carbon-rich and oxygen-rich asymptotic giant branch stars an indication about spatial variations in metallicity. These amount to about 1.56 dex, twice of what has been previously found within each Magellanic Cloud using the same technique. We have calibrated our photometry on the DENIS (I-band) and 2MASS (J and K-s bands) data and obtained a distance modulus of (m-M)(0) = 23.34+/-0.12 from the position of the tip of the RGB. The large scale distribution of late-type stars suggests that either the galaxy is viewed under a high inclination angle or it has a non-negligible thickness.

“Asymptotic giant branch stars” developed into a broad, coherent field of research in the last quarter of the preceding century, but its roots go much deeper into the past and involve several serendipitous discoveries. We will discuss briefly when and how its most significant concepts came to the surface. To that end we have arranged the historical developments into five broad areas. We do not intend to write a full history of astronomy, and we will skip over the fundamental developments in physics. When no specific reference is given, we have used North’s History of Astronomy and Cosmology [56] and A Source Book in Astronomy and Astrophysics, edited by Lang and Gingerich [48]. We also limit most of our review to the developments before 1984 for two reasons: (i) In a long review published in 1983 Iben and Renzini [39] showed that the theoretical side of the AGB evolution was broadly and consistently understood; (ii) in 1984 the results of the IRAS full-sky survey at 12, 25, 60, and 100 μm became public; the catalogue contained thousands of AGB stars, and a new era of observation began.