OH/IR stars in the inner bulge detected by ISOGAL

Ortiz, R.; Blommaert, J. A. D. L.; Copet, E.; Ganesh, Shashikiran; Habing, H. J.; Messineo, M.; Omont, A.; Schultheis, M.; Schüller, F.

doi:10.1051/0004-6361:20020514

Cited by 39 publications

(64 citation statements)

References 28 publications

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“…Intermediate in colours between the Galactic centre OH/IR stars of the just above mentioned studies and the colours of our sample are the OH/IR stars observed by the ISOGAL survey (Ortiz et al 2002) and of the MSX-selected selected sample of AGB stars (Ojha et al 2007). Their luminosity distributions peak around 8000 L , and objects with higher luminosities are found in both samples.…”

Section: The Distribution Of Luminosities and Mass-loss Ratesmentioning

confidence: 62%

“…This allows 4 http://aladin.u-strasbg.fr/ us to determine the bolometric flux with much higher accuracy compared to earlier times, when (uncertain) bolometric corrections or (unsuitable) black-body fitting had to be applied to cover the unobserved parts of the SED (e.g. van der Veen & Breukers 1989;Ortiz et al 2002). However, the photometric data available is not complete for all sources so that a determination of the bolometric flux by integration of an interpolated curve between the available data points will be unsatisfactory.…”

Section: Observed Bolometric Fluxmentioning

confidence: 99%

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Study of extremely reddened AGB stars in the Galactic bulge

Jiménez-Esteban

Engels

2015

A&A

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Context. Extremely reddened asymptotic giant branch stars (AGB) lose mass at high rates of >10 −5 M yr −1 . This is the very last stage of AGB evolution, in which stars in the mass range ∼2.0−4.0 M (for solar metallicity) should have been converted to C stars already. The extremely reddened AGB stars in the Galactic bulge are however predominantly O-rich, implying that they might be either low-mass stars or stars at the upper end of the AGB mass range. Aims. Our goal is to determine the mass range of the most reddened AGB stars in the Galactic bulge. Methods. Using Virtual Observatory tools, we constructed spectral energy distributions of a sample of 37 evolved stars in the Galactic bulge with extremely red IRAS colours. We fitted DUSTY models to the observational data to infer the bolometric fluxes. Applying individual corrections for interstellar extinction and adopting a common distance, we determined luminosities and mass-loss rates, and inferred the progenitor mass range from comparisons with AGB evolutionary models. Results. The observed spectral energy distributions are consistent with a classification as reddened AGB stars, except for two stars, which are proto-planetary nebula candidates. For the AGB stars, we found luminosities in the range ∼3000−30 000 L and mass-loss rates ∼10 −5 −3 × 10 −4 M yr −1 . The corresponding mass range is ∼1.1−6.0 M assuming solar metallicity. Conclusions. Contrary to the predictions of the evolutionary models, the luminosity distribution is continuous, with many O-rich AGB stars in the mass range in which they should have been converted into C stars already. We suspect that bulge AGB stars have higher than solar metallicity and therefore may avoid the conversion to C-rich. The presence of low-mass stars in the sample shows that their termination of the AGB evolution also occurs during a final phase of very high mass-loss rate, leading to optically thick circumstellar shells.

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Section: The Distribution Of Luminosities and Mass-loss Ratesmentioning

confidence: 62%

Section: Observed Bolometric Fluxmentioning

confidence: 99%

Study of extremely reddened AGB stars in the Galactic bulge

Jiménez-Esteban

Engels

2015

A&A

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“…Three OH/IR stars were selected for observations on the basis of strong IR fluxes: OH359.117-0.169, OH359.762+0.120 and OH359.971-0.119 (Ortiz et al 2002). The relevant data for these stars are listed in Table 1, where F [15] denotes the flux density at a wavelength of 15 μm as measured by the Infrared Space Observatory (ISO).…”

Section: Observationsmentioning

confidence: 99%

“…The IR properties of this star also are such that it is arguable whether it belongs to the bulge (cf. Ortiz et al 2002).…”

Section: Oh359971-0119mentioning

confidence: 99%

CO in OH/IR stars close to the Galactic centre

Winnberg¹,

Deguchi

Reid

et al. 2009

A&A

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Aims.A pilot project has been carried out to measure circumstellar CO emission from three OH/IR stars close to the Galactic centre. The intention was to find out whether it would be possible to conduct a large-scale survey for mass-loss rates using, for example, the Atacama large millimeter array (ALMA). Such a survey would increase our understanding of the evolution of the Galactic bulge. Methods. Two millimetre-wave instruments were used: the Nobeyama Millimeter Array at 115 GHz and the Submillimeter 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.Results. Towards two of the stars, CO emission was detected with positions and radial velocities coinciding within the statistical errors with the corresponding data of the associated OH sources. However, for one of the stars the line profile is not what one expects for an unresolved expanding circumstellar envelope. We believe that this CO envelope is partially resolved and that this star therefore is a foreground star not belonging to the bulge. Conclusions. The results of the observations have shown that it is possible to detect line profiles of circumstellar CO from late-type stars both within and in the direction of the Galactic bulge. ALMA will be able to detect CO emission in short integrations with sensitivity sufficient to estimate mass-loss rates from a large number of such stars.

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“…Three catalogues of OH/IR stars (Lindqvist et al 1992;Sevenster et al 1997;Sjouwerman et al 1998) were compiled and associated with ISOGAL data in the inner Galactic Bulge by Ortiz et al (2002). They found 37 OH/IR stars in the FC−027 field, 34 of which are associated with ISOGAL sources within 6 .…”

Section: Late Evolved Starsmentioning

confidence: 99%

Recent star formation in the inner Galactic Bulge seen by ISOGAL

Schüller

Omont²,

Glass

et al. 2006

A&A

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Context. The stellar populations in the central region of the Galaxy are poorly known because of the high visual extinction and very great source density in this direction. Aims. To use recent infrared surveys for studying the dusty stellar objects in this region. Methods. We analyse the content of a ∼20 × 20 arcmin 2 field centred at (l, b) = (−0.27 • , −0.06 • ) observed at 7 and 15 µm as part of the ISOGAL survey. These ISO observations are more than an order of magnitude better in sensitivity and spatial resolution than the IRAS observations. The sources are cross-associated with other catalogues to identify various types of objects. We then derive criteria to distinguish young objects from post-main sequence stars. Results. We find that a sample of about 50 young stellar objects and ultra-compact Hii regions emerges, out of a population of evolved AGB stars. We demonstrate that the sources colours and spatial extents, as they appear in the ISOGAL catalogue, possibly complemented with MSX photometry at 21 µm, can be used to determine whether the ISOGAL sources brighter than 300 mJy at 15 µm (or [15] ≤ 4.5 mag) are young objects or late-type evolved stars.

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OH/IR stars in the inner bulge detected by ISOGAL

Cited by 39 publications

References 28 publications

Study of extremely reddened AGB stars in the Galactic bulge

Study of extremely reddened AGB stars in the Galactic bulge

CO in OH/IR stars close to the Galactic centre

Recent star formation in the inner Galactic Bulge seen by ISOGAL

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