CO Observations of Semiregular Variables

Kerschbaum, F.; Olofsson, H.; Hron, J.; Aringer, B.

doi:10.1007/978-94-011-0147-9_113

Cited by 55 publications

(88 citation statements)

References 2 publications

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“…To get from absolute K-magnitudes to the absolute bolometric magnitude M bol , we applied the BC(K) relations of Kerschbaum et al (2010) based on the J − K colour. Quasi-simultaneous photometry in the J and K bands was collected from the works of Catchpole et al (1979), Fouqué et al (1992), Kerschbaum & Hron (1994), Whitelock et al (2006), and the 2MASS catalogue (Skrutskie et al 2006), transformed to the 2MASS photometric system with the relations given by Carpenter (2001), and averaged to a final value. For some stars, only the 2MASS data were available, but for most stars this resulted in a cycle-averaged J − K colour.…”

Section: Luminositiesmentioning

confidence: 99%

The evolutionary state of Miras with changing pulsation periods

Uttenthaler

Stiphout

Voet

et al. 2011

A&A

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Context. Miras are long-period variables thought to be in the asymptotic giant branch (AGB) phase of evolution. In about one percent of known Miras, the pulsation period is changing. It has been speculated that this changing period is the consequence of a recent thermal pulse in these stars. Aims. We aim to clarify the evolutionary state of these stars, and to determine in particular whether or not they are in the thermallypulsing (TP-)AGB phase. Methods. One important piece of information that has been neglected so far when determining the evolutionary state is the presence of the radio-active s-process element technetium (Tc). We obtained high-resolution, high signal-to-noise-ratio optical spectra of a dozen prominent Mira variables with changing pulsation period to search for this indicator of TPs and dredge-up. We also use the spectra to measure lithium (Li) abundances. Furthermore, we establish the evolutionary states of our sample stars by means of their present-day periods and luminosities. Results. Among the twelve sample stars observed in this programme, five were found to show absorption lines of Tc. BH Cru is found to be a carbon-star, its period increase in the past decades possibly having stopped by now. We report a possible switch in the pulsation mode of T UMi from Mira-like to semi-regular variability in the past two years. R Nor, on the other hand, is probably a fairly massive AGB star, which could be true for all meandering Miras. Finally, we assign RU Vul to the metal-poor thick disk with properties very similar to the short-period, metal-poor Miras. Conclusions. We conclude that there is no clear correlation between period change class and Tc presence. The stars that are most likely to have experienced a recent TP are BH Cru and R Hya, although their rates of period change are quite different.

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Section: Luminositiesmentioning

confidence: 99%

The evolutionary state of Miras with changing pulsation periods

Uttenthaler

Stiphout

Voet

et al. 2011

A&A

Self Cite

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“…The obtained dust mass on the order of 10 −4 M is comparable to what is estimated from optical observations (∼2 × 10 −5 M ; Izumiura et al 2007), given the uncertainty of κ 100 . This gives a total mass of ∼10 −2 (κ 100 /25) −1 ( f gd /100) M , where f gd is the gas-to-dust mass ratio, which is considered to be in the range of 200-800 (Jura 1986;Kerschbaum et al 1996;Groenewegen et al 1998). The last two terms of the total mass act to cancel each other out, and their product is almost unity for the case of carbon stars (for example see Jura 1986;Groenewegen et al 1998).…”

Section: Mass and Mass-loss Rate In The Shellmentioning

confidence: 99%

Extended dust shell of the carbon star U Hydrae observed with AKARI

Izumiura

Ueta

Yamamura

et al. 2011

A&A

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Context. Low-to intermediate-mass stars lose a significant fraction of their mass while they are on the asymptotic giant branch (AGB). This mass loss is considered to determine the final stages of their evolution. The material ejected from the stellar photosphere forms a circumstellar envelope in its surroundings. Layers of circumstellar envelope constitute the footprint of mass-loss history. Aims. Our aim is to probe the mass-loss history in the carbon star U Hya in the last ∼10 4 years by investigating the distribution of dust in the circumstellar envelope with high spatial resolution. Methods. We observed U Hya in the far-infrared (FIR) at 65, 90, 140, and 160 μm simultaneously, using the slow scan observing mode of the far-infrared surveyor (FIS) aboard the infrared astronomical satellite AKARI. It produced a map of ∼10 × 40 in size in each band. Results. The FIS maps reveal remarkably circular, ring-like emission structure almost centered on the star, showing the presence of a detached, spherical dust shell. A hollow dust shell model gives the inner radius R in of 101-107 [(2.5-2.6) × 10 17 cm], thickness that covers a half of the total dust mass ΔR hm of 16-23 [(3.8-5.6) × 10 16 cm], which gives ΔR hm /R in ∼ 0.2, and the power-law index of the dust opacity distribution of 1.10-1.15. The dust mass in the shell is well-constrained to be (0.9-1.4) × 10 −4 (κ 100 /25) −1 M , where κ 100 is the dust absorptivity at 100 μm in units of cm 2 g −1 . The dust mass-loss rate at R in is found to be (1.8-9.6) × 10 −8 (κ 100 /25) −1 (v e /15) M yr −1 , which shows that the total mass-loss rate in the shell is at least an order of magnitude higher than the current rate, where v e is the outflow velocity at R in in units of km s −1 . An extension of FIR emission along PA ∼ −70 • is found out to ∼5 from the star, which is probably a ram-stripping wake by the ISM wind. We also find excess FIR emission that might indicate the earliest departure from spherical symmetry in the AGB mass loss inside the shell. Conclusions. The dust shell of U Hya is a hollow sphere and has an effective width that is narrower than the spatial resolution of the FIS. It could be formed as either a direct consequence of a thermal pulse, a result of two-wind interaction induced by a thermal pulse, a termination shock, or any combination of these processes.

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“…For the fits, the SED was traced by J, H, K, and L band photometry (Kerschbaum & Hron 1994;Kerschbaum 1995, and references therein), visual data from the General Catalogue of Variable Stars (Kholopov et al 1985−88), and mid-and far-infrared photometry from the IRAS Point Source Catalogue (Joint IRAS Working Group 1988). For details, we refer to Kerschbaum & Hron (1996).…”

Section: Data Basementioning

confidence: 99%

Bolometric corrections for cool giants based on near-infrared photometry

Kerschbaum

Lebzelter

Mekul

2010

A&A

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Context. The bolometric luminosity is one of the most fundamental stellar parameters that is generally not directly observable. When integrating whole spectral energy distributions, bolometric corrections are widely used. These corrections are typically specified for a well defined object type, a measured photometric colour, and the colour index range for which it is calibrated. Aims. We provide this bolometric correction for the near-infrared colours of red late giants. Methods. We compare bolometric luminosities derived from fits to spectral energy distributions covering the visual and near, mid, and far infrared to different near-infrared colour indices to define subgroups within our stellar sample and finally obtain specific bolometric corrections.Results. For well-defined subgroups of different near-infrared colours and atmospheric chemistry, we present four distinct bolometric colour relations and compare these to earlier results from the literature.

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CO Observations of Semiregular Variables

Cited by 55 publications

References 2 publications

The evolutionary state of Miras with changing pulsation periods

The evolutionary state of Miras with changing pulsation periods

Extended dust shell of the carbon star U Hydrae observed with AKARI

Bolometric corrections for cool giants based on near-infrared photometry

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