AGB stars and galactic dynamics

Dejonghe, Herwig; Caelenberg, K. Van

doi:10.1017/s0074180900203471

Cited by 5 publications

(1 citation statement)

References 24 publications

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“…Mira variables have a low effective temperature (< 3500 K), cool extended atmospheres (radius up to few 100R ⊙ ), and luminosity can reach up to a few 10 3 L ⊙ (Mattei 1997). High luminous Mira variables play a significant role in the studies of stellar evolution, stellar populations, galactic-extragalactic structure and evolution (Lançon et al 1999;Dejonghe & van Caelenberg 1999;Groenewegen et al 2009), and enriches the interstellar medium (ISM) significantly through the high mass-loss (Habing 1996). The high mass loss and relatively low surface temperature of these evolved stars provide a habitable zone for several molecules such as TiO, VO, H 2 O, and CO in their extended atmospheres.…”

Section: Introductionmentioning

confidence: 99%

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

Ghosh

Mondal

Das

et al. 2018

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We describe the time-dependent properties of a new spectroscopically confirmed Mira variable, which was discovered in 2013 as MASTER-Net Optical Transient (OT) J212444.87+321738.3 towards the Cygnus constellation. We have performed long-term optical/near-infrared (NIR) photometric and spectroscopic observations to characterize the object. From the optical/NIR light curves, we estimate a variability period of 465 ± 30 days. The wavelength-dependent amplitudes of the observed light-curves range from ∆I∼4 mag to ∆K∼1.5 mag. The (J-K) color-index varies from 1.78 to 2.62 mag over phases. Interestingly, a phase lag of ∼60 days between optical and NIR light curves is also seen, as in other Miras. Our optical/NIR spectra show molecular features of TiO, VO, CO, and strong water bands which are a typical signature of oxygen-rich Mira. We rule out S-or C-type as ZrO bands at 1.03 and 1.06 µm and C 2 band at 1.77 µm are absent. We estimate the effective temperature of the object from the SED, and distance and luminosity from standard Period-Luminosity relations. The optical/NIR spectra display time-dependent atomic and molecular features (e.g. TiO, NaI, CaI, H 2 O,CO), as commonly observed in Miras. Such spectroscopic observations are useful for studying pulsation variability in Miras.

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Section: Introductionmentioning

confidence: 99%

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

Ghosh

Mondal

Das

et al. 2018

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Near-infrared spectroscopy of AGB star candidates in Fornax, Sculptor, and NGC 6822

Groenewegen¹,

Lançon

Marescaux

2009

A&A

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Context. The asymptotic giant branch (AGB) phase is characterised by substantial mass loss that is accompanied by the formation of dust. In extreme cases this will make the star no longer visible in the optical. For a better understanding of AGB evolution it is important to identify and characterise these very red AGB stars. Aims. The first aim of this article is to improve the census of red AGB stars in three Local Group galaxies, based on near-IR spectroscopic observations of new candidates with red 2MASS (J − K) colours. The opportunity is taken to compare the near-IR spectra with those of Milky Way stars. Methods. We used ISAAC on the ESO VLT to take J and H-band spectra of 36 targets in Fornax, Sculptor and NGC 6822. Results. Twelve new C-stars are found in Fornax, and one is confirmed in Sculptor. All C-stars have (J − K) > 1.6, and are brighter than −3.55 in bolometric magnitude. Ten new oxygen-rich late-type giant stars are identified in Fornax, but none is extremely red or very luminous. Five luminous O-rich AGB stars are identified in NGC 6822, of which 3 show water absorption, indicative of spectral type M. Again, none is as red as Milky Way OH/IR stars, but in this galaxy the list of candidate AGB stars is biased against very red objects. In some C-stars with (J − K) > 2 an extremely strong 1.53 μm absorption band is found. These stars are probably all Mira variables and the feature is related to the low temperature, high density chemistry that is a first step towards dust formation and mass loss.

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A census of AGB stars in Local Group galaxies

Nowotny

Kerschbaum

Schwarz

et al. 2001

A&A

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Abstract. Our photometric survey of Local Group galaxies, using a four filter technique based on the method of Wing (1971) allows the identification and subsequent characterization of their late-type stellar content. Two narrow band filters centred on molecular bands of TiO and CN allow us to distinguish between AGB stars of different chemistries [M-type (O-rich) and C-type (C-rich)]. The faint dwarf spheroidal galaxy And II, a member of the M 31 subgroup, was surveyed. From photometry in V and i as well as in the narrow band filters TiO and CN we were able to identify 7 new AGB carbon stars, to derive their mean absolute M i and bolometric magnitude M bol , their luminosity function, and their spatial distribution. We are unable to establish the true C/M ratio because the few M stars of And II are overwhelmed by foreground Galactic M stars.

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AGB stars and galactic dynamics

Cited by 5 publications

References 24 publications

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

Near-infrared spectroscopy of AGB star candidates in Fornax, Sculptor, and NGC 6822

A census of AGB stars in Local Group galaxies

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