First detection of winds in red giants by microwave continuum techniques

Drake, S. A.; Linsky, Jeffrey L.

doi:10.1086/184154

Cited by 18 publications

(8 citation statements)

References 10 publications

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“…There have been radio‐wavelength surveys (typically at 2 and 6 cm) of red giant stars including stars on the AGB of the Hertzsprung–Russell diagram (see Drake & Linsky 1983, 1986; Drake, Linsky & Elitzer 1987; Drake et al 1991; Luttermoser & Brown 1992). Typically evolved stars on the cool side of the ‘dividing line’ are either not detected at these wavelengths or are very weak sources – giant stars of M6 or warmer have been detected (Drake et al 1991).…”

Section: Discussionmentioning

confidence: 99%

Radio emissions from substellar companions of evolved cool stars

Ignace¹,

Giroux²,

Luttermoser³

2010

Monthly Notices of the Royal Astronomical Society

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A number of substellar companions to evolved cool stars have now been reported. Cool giants are distinct from their progenitor main-sequence low-mass stars in a number of ways. First, the mass loss rates of cool giant stars are orders of magnitude greater than for the late-type main-sequence stars. Secondly, on the cool side of the Linsky-Haisch 'dividing line', K and M giant stars are not X-ray sources, although they do show evidence for chromospheres. As a result, cool star winds are largely neutral for those spectral types, suggesting that planetary or brown dwarf magnetospheres will not be effective in standing off the stellar wind. In this case, one expects the formation of a bow shock morphology at the companion, deep inside its magnetosphere. We explore radio emissions from substellar companions to giant stars using (a) the radiometric Bode's law and (b) a model for a bow shock morphology. Stars that are X-ray emitters likely have fully ionized winds, and the radio emission can be at the milli-Jansky level in favourable conditions. Non-coronal giant stars produce only micro-Jansky level emissions when adjusted for low-level ionizations. If the largely neutral flow penetrates the magnetosphere, a bow shock results that can be strong enough to ionize hydrogen. The incoherent cyclotron emission is sub-micro-Jansky. However, the long wavelength radio emission of Solar system objects is dominated by the cyclotron maser instability (CMI) mechanism. Our study leads to the following two observational prospects. First, for coronal giant stars that have ionized winds, application of the radiometic Bode's law indicates that long wavelength emission from substellar companions to giant stars may be detectable or nearly detectable with existing facilities. Secondly, for the non-coronal giant stars that have neutral winds, the resultant bow shock may act as a 'feeder' of electrons that is well embedded in the companion's magnetosphere. Incoherent cyclotron emissions are far too faint to be detectable, even with next generation facilities; however, much brighter flux densities may be achievable when CMI is considered.

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Section: Discussionmentioning

confidence: 99%

Radio emissions from substellar companions of evolved cool stars

Ignace¹,

Giroux²,

Luttermoser³

2010

Monthly Notices of the Royal Astronomical Society

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“…As for the observed mass-loss rate, radio continuum emission measures at 6 cm and 2 cm wavelength yielded ionized mass-loss rates between 6.9 × 10 −11 and 8.4 × 10 −11 M yr −1 (Drake & Linsky 1983. As far as the total mass-loss rate is concerned, we would need to know the average ionization ratio of the CS envelope.…”

Section: Individual Case Studiesmentioning

confidence: 99%

A critical test of empirical mass loss formulas applied to individual giants and supergiants

Schröder

Cuntz

2007

A&A

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To test our new, improved Reimers-type mass-loss relation, given by Schröder & Cuntz in 2005 (ApJ, 630, L73), we take a look at the best studied galactic giants and supergiants -particularly those with spatially resolved circumstellar shells and winds, obtained directly or by means of a companion acting as a probing light source. Together with well-known physical parameters, the selected stars provide the most powerful and critical observational venues for assessing the validity of parameterized mass-loss relations for cool winds not driven by molecules or dust. In this study, star by star, we compare our previously published relation with the original Reimers relation (1975, Mem. Roy. Soc. Liège 6. Ser. 8, 369), the Lamers relation (1981, ApJ, 245, 593), and the two relations by de Jager and his group (1988, A&AS, 72, 259; 1990, A&A, 231, 134). The input data, especially the stellar masses, have been constrained using detailed stellar evolution models. We find that only the relationship by Schröder & Cuntz agrees, within the error bars, with the observed mass-loss rates for all giants and supergiants.

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“…Herman, Baud, and Habing (1985) did not detect any of the 12 OH/IR stars they observed at 6 cm above a detection threshold of 0.1 mJy. Drake and Linsky (1983b) detected 6 cm emission from a 1 Her (M5 II) and inferred a fractional ionization of 0.002-0.02 in its expanding chromosphere. In their subsequent 6 cm survey, Drake and Linsky (1986, hereafter referred to as DL) detected three K and M giants (a Boo (K2 III),p Per (M4 II) and// Gem (M3 III)) and possibly detected^ UMi (K4 III).…”

Section: Introductionmentioning

confidence: 99%

“…Drake and Linsky (1983b) detected 6 cm emission from a 1 Her (M5 II) and inferred a fractional ionization of 0.002-0.02 in its expanding chromosphere. In their subsequent 6 cm survey, Drake and Linsky (1986, hereafter referred to as DL) detected three K and M giants (a Boo (K2 III),p Per (M4 II) and// Gem (M3 III)) and possibly detected^ UMi (K4 III). In Table I, we collect all the published radio-continuum data on M and C giants and supergiants later than spectral type M4 (if oxygen rich) for which there is at least one claimed radio detection.…”

Section: Introductionmentioning

confidence: 99%

“…V we summarize our conclusions and present suggestions for future observations. Drake and Linsky ( 1986) discussed various plausible radio-emission mechanisms for G to mid M giants. We restrict ourselves here to a brief summary of stellar-wind type models and three other possible sources of radio-continuum emission that must contribute at some level.…”

Section: Introductionmentioning

confidence: 99%

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A radio-continuum survey of the coolest M and C giants

Drake¹,

Linsky²,

Elitzur³

1987

The Astronomical Journal

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We present the results of a sensitive VLA continuum survey of 22 cool M and C type giants and supergiants, including nine carbon stars, one S type star, and 12 M stars. The purpose of the survey was to probe the physical properties of the partially ionized, expanding chromospheres of the coolest luminous stars. Of the 22 stars observed at 6 cm, none were detected directly, although extended emission was detected near NML Cyg and OH 26.5 + 0.6, and a point source was detected near AFGL 865. Of the three stars observed at 2 cm, R Aql (M6.5e-9e) was detected as a 0.54 + 0.17 mJy source, and a point source was detected 1" from R Cas (M6e-9e) and may be physically associated with the star. These data imply small upper limits for the ionized-mass-loss rates and 2-6 cm spectral indices that are significantly steeper than the 0.6 value predicted by the "standard" stellar-wind model. The typical fractional ionizations/ on <0.0003-0.003 are considerably smaller than for the early M giants and supergiants, which indicates that hydrogen is predominately neutral and that carbon and other metals may not be completely once-ionized in many of the late M giants. For a number of the stars, the brightnesstemperature upper limits imply that the winds and chromospheres are optically thin at 6 cm. This condition sets useful constraints on the chromospheric-emission measures for these stars. The nondetection of o Ceti (Mira) at both 2 and 6 cm, despite a previous 6 cm detection, supports the idea that the radio-continuum emission of these stars may be variable, perhaps due either to flares or to the passage of pulsation-generated shock waves through their outer atmospheres.

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First detection of winds in red giants by microwave continuum techniques

Cited by 18 publications

References 10 publications

Radio emissions from substellar companions of evolved cool stars

Radio emissions from substellar companions of evolved cool stars

A critical test of empirical mass loss formulas applied to individual giants and supergiants

A radio-continuum survey of the coolest M and C giants

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