New Mass-Loss Measurements from Astrospheric Lyα Absorption

Wood, Brian E.; Müller, Hans-Reinhard; Zank, G. P.; Linsky, Jeffrey L.; Redfield, Seth

doi:10.1086/432716

Cited by 454 publications

(668 citation statements)

References 19 publications

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“…We therefore postulate degenerative processes for the crystalline structure of the dust by ionic irradiation. Although we cannot observe the stellar wind directly, its flux and/or speed might be related to the X-ray luminosity, as shown for low X-ray fluxes by Wood et al (2005) by comparing stellar mass loss rates with X-ray surface fluxes.…”

Section: Discussionmentioning

confidence: 89%

Dust amorphization in protoplanetary disks

Glauser

Güdel

Watson

et al. 2009

A&A

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Aims. High-energy irradiation of circumstellar material might impact the structure and the composition of a protoplanetary disk and hence the process of planet formation. In this paper, we present a study of the possible influence of stellar irradiation, indicated by X-ray emission, on the crystalline structure of circumstellar dust. Methods. The dust crystallinity is measured for 42 class II T Tauri stars in the Taurus star-forming region using a decomposition fit of the 10 μm silicate feature, measured with the spitzer IRS instrument. Since the sample includes objects with disks of various evolutionary stages, we further confine the target selection, using the age of the objects as a selection parameter. Results. We correlate the X-ray luminosity and the X-ray hardness of the central object with the crystalline mass fraction of the circumstellar dust and find a significant anti-correlation for 20 objects within an age range of approx. 1 to 4.5 Myr. We postulate that X-rays represent the stellar activity and consequently the energetic ions of the stellar winds which interact with the circumstellar disk. We show that the fluxes around 1 AU and ion energies of the present solar wind are sufficient to amorphize the upper layer of dust grains very efficiently, leading to an observable reduction of the crystalline mass fraction of the circumstellar, sub-micron sized dust. This effect could also erase other relations between crystallinity and disk/star parameters such as age or spectral type.

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Section: Discussionmentioning

confidence: 89%

Dust amorphization in protoplanetary disks

Glauser

Güdel

Watson

et al. 2009

A&A

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“…(an equivalent relation therefore holds betweenṀ w and L X ); using the activity-age relation (see below), one findsṀ 378 M. Güdel ( Wood et al 2005). If stellar-wind mass loss could be measured directly, it would be a genuine magnetic activity indicator, because mass-loss is higher in young, magnetically active stars than in evolved stars.…”

Section: The Rotation and Mass-loss History Of The Sunmentioning

confidence: 99%

“…The measurable absorption depths in Lyα are compared with results from hydrodynamic model calculations (Wood et al 2002, Wood et al 2005. The amount of astrospheric absorption should scale with the wind ram pressure, P w ∝Ṁ w V w , where V w is the (unknown) wind velocity (Wood & Linsky 1998).…”

Section: The Rotation and Mass-loss History Of The Sunmentioning

confidence: 99%

Magnetic activity, high-energy radiation and variability: from young solar analogs to low-mass objects

Güdel

2009

Proc. IAU

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Abstract. Magnetic activity on cool stars expresses itself in a bewildering variety of radiative and particle output originating from magnetic regions between the photosphere and the corona. Given its origin in evolving magnetic fields, most of this output is variable in time. Radiation in the ultraviolet, the extreme ultraviolet, and the X-ray ranges are important for heating and ionizing upper planetary atmospheres and thus driving atmospheric evaporation. Additionally, stellar winds interact with the upper atmospheres and may lead to further erosion. The stellar high-energy output is therefore a prime factor in determining habitability of planets. We summarize our knowledge of magnetic activity in young solar analogs and lower-mass stars and show how the stellar output changes on evolutionary timescales.

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“…Finally, the active regions and flares in the upper chromosphere, transition regions and coronae as well as solar-like winds have been studied thanks to the UV, and EUV data from, e.g., IUE, HST, GALEX, EUVE and FUSE (e.g., Jordan et al 1987;Ayres 1995, Pagano et al 2004, Ribas et al 2005, Wood et al 2005, X-ray data from, e.g., Einstein, Rosat, ASCA, Beppo-SAX, Chandra, and XMM (e.g., Favata & Micela 2003 and reference therein, Telleschi et al 2005, Stelzer 2007), and radio observations from VLA, VLBI, VLBA, and single-dishes (e.g., Güdel & Benz 1993, Benz & Güdel 1994, Umana et al 1995, Trigilio et al 1998.…”

Section: Sources Of Long-term Data On Magnetic Activitymentioning

confidence: 99%

“…HD 81809 is a close visual binary of slow rotating solar-like stars (G2 V+G9 V) with a well defined chromospheric cycle (Baliunas et al 1995). XMM-Newton observations have shown a well-defined coronal cycle that has been modeled by Favata et al (2008) with a simple extension of the solar case in terms of varying coverage of solar-like active regions, but (Wood et al 2005).…”

Section: Long-term Observations Of Coronaementioning

confidence: 99%

Long-term stellar variability

Pagano

2009

Proc. IAU

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Abstract. Stars with significant subsurface convection zones develop magnetic loop structures that, arising from the surface upward to the external atmospheres, cause flux variability detectable throughout the whole electromagnetic spectrum. In fact, diagnostics of magnetic activity are in radio wavelengths, where gyrosincrotron radiation arises from the quiescent and flaring corona; in the optical region, where important signatures are the Balmer lines, the Ca ii IRT and H&K lines; in the UV and X ray domains, the latter mainly due to coronal thermal plasma. The zoo of different magnetic features observed for the Sun -spots, faculae, flares, CMEs -are characterized by different temporal evolution and energetics, both in quantity and quality. As a consequence, the time scale of variability, the amount of involved energy and the quality of the involved photons are used as fingerprints in interpreting the observed stellar variability in the framework of the solar-stellar analogy. Here I review main results from long-term multiwavelength observations of cool star atmospheres, with emphasis to similarities and differences with the solar case.

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New Mass-Loss Measurements from Astrospheric Lyα Absorption

Cited by 454 publications

References 19 publications

Dust amorphization in protoplanetary disks

Dust amorphization in protoplanetary disks

Magnetic activity, high-energy radiation and variability: from young solar analogs to low-mass objects

Long-term stellar variability

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