A H I Imaging Survey of Asymptotic Giant Branch Stars

Matthews, L. D.; Bertre, T. Le; Gérard, E.; Johnson, Megan

doi:10.1088/0004-6256/145/4/97

Cited by 21 publications

(35 citation statements)

References 116 publications

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“…12. RS Cnc also contrasts with the other stars known to have trailing H i wakes in that its space velocity is much lower, ∼15 km s −1 compared with V space > ∼ 57 km s −1 (see Matthews et al 2013). While no velocity gradient is seen along the tail of RS Cnc, the morphology of the tail gas reveals evidence of the importance of hydrodynamical effects.…”

Section: Kinematics Of the H I Emissionmentioning

confidence: 89%

The multi-scale environment of RS Cancri from CO and H I observations

Hoai¹,

Matthews²,

Winters³

et al. 2014

A&A

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We present a detailed study of the circumstellar gas distribution and kinematics of the semi-regular variable star RS Cnc on spatial scales ranging from ∼1 (∼150 AU) to ∼6 (∼0.25 pc). Our study utilizes new CO1−0 data from the Plateau de Bure Interferometer and new H i 21 cm line observations from the Jansky Very Large Array (JVLA), in combination with previous observations. New modeling of CO1−0 and CO2−1 imaging observations leads to a revised characterization of RS Cnc's previously identified axisymmetric molecular outflow. Rather than a simple disk-outflow picture, we find that a gradient in velocity as a function of latitude is needed to fit the spatially resolved spectra, and in our preferred model, the density and the velocity vary smoothly from the equatorial plane to the polar axis. In terms of density, the source appears quasi-spherical, whereas in terms of velocity the source is axisymmetric with a low expansion velocity in the equatorial plane and faster outflows in the polar directions. The flux of matter is also larger in the polar directions than in the equatorial plane. An implication of our model is that the stellar wind is still accelerated at radii larger than a few hundred AU, well beyond the radius where the terminal velocity is thought to be reached in an asymptotic giant branch star. The JVLA H i data show the previously detected head-tail morphology, and also supply additional details about the atomic gas distribution and kinematics. We confirm that the head seen in H i is elongated in a direction consistent with the polar axis of the molecular outflow, suggesting that we are tracing an extension of the molecular outflow well beyond the molecular dissociation radius (up to ∼0.05 pc). The 6 -long H i tail is oriented at a PA of 305• , consistent with the space motion of the star. The tail is resolved into several clumps that may result from hydrodynamic effects linked to the interaction with the local interstellar medium. We measure a total mass of atomic hydrogen M HI ≈ 0.0055 M and estimate a lower limit to the timescale for the formation of the tail to be ∼6.4 × 10 4 years.

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Section: Kinematics Of the H I Emissionmentioning

confidence: 89%

The multi-scale environment of RS Cancri from CO and H I observations

Hoai¹,

Matthews²,

Winters³

et al. 2014

A&A

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“…These are difficult observations to perform because of the omnipresence of this emission. Thanks to some dedicated work, however, considerable progress has been made in this area (Le Bertre and Gérard 2004;Matthews et al 2013Matthews et al , 2015. In general, the data do not contradict a largely isotropic mass loss, although there is evidence of circumstellar-interstellar media interactions at large distances from the stars.…”

Section: Circumstellar Morphologymentioning

confidence: 97%

“…3.1.3, but there are also interesting significant deviations from overall spherical symmetry. For instance, there is morphological evidence of the star (and the CSE) moving through the ISM in terms of bow shocks (Cox et al 2012a;Matthews et al 2013;Sahai and Mack-Crane 2014), Fig. 20, left panel.…”

Section: Morphology Of Cses: From the Wind Acceleration Region To Glomentioning

confidence: 99%

Mass loss of stars on the asymptotic giant branch

Höfner

Olofsson

2018

Astron Astrophys Rev

475

376

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As low-and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newlyformed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angularresolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their windforming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angularresolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building B Susanne Höfner

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“…It is now well established that detectable circumstellar envelopes of atomic hydrogen, spanning up to a parsec or more in size, form around certain types of evolved, mass-losing stars, and furthermore that the properties of these envelopes are significantly impacted by the space motion of the stars and the interaction of the stellar ejecta with the ISM (e.g., Gérard & Le Bertre 2006;Le Bertre et al 2012;Matthews et al 2013). For stars with low space velocities, quasi-spherical shells may be observed, while in cases where the space velocity is sufficiently high, bow shocks may be detectable in IR and ultraviolet wavelengths, and the effects of ram pressure may sweep back a portion of the ejecta to form a trailing gaseous wake (see M12; Matthews et al 2013 and references therein).…”

Section: Implications Of the Shell Morphology And Kinematics On Its Pmentioning

confidence: 99%

“…For stars with low space velocities, quasi-spherical shells may be observed, while in cases where the space velocity is sufficiently high, bow shocks may be detectable in IR and ultraviolet wavelengths, and the effects of ram pressure may sweep back a portion of the ejecta to form a trailing gaseous wake (see M12; Matthews et al 2013 and references therein). Numerical models also predict that the properties of the shells will change significantly as stars evolve and undergo changes in their massloss rates, and as the ejecta expand into the ISM (e.g., Wareing et al 2007;Villaver et al 2012).…”

Section: Implications Of the Shell Morphology And Kinematics On Its Pmentioning

confidence: 99%

A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS

Matthews

Marengo

Evans

2016

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We present the results of a search for H I 21 cm line emission from the circumstellar environments of four Galactic Cepheids (RS Pup, X Cyg, ζ Gem, and T Mon) based on observations with the Karl G. Jansky Very Large Array. The observations were aimed at detecting gas associated with previous or ongoing mass loss. Near the long-period Cepheid TMon, we report the detection of a partial shell-like structure whose properties appear consistent with originating from an earlier epoch of Cepheid mass loss. At the distance of TMon, the nebula would have a mass (H I+He) of~ M 0.5 , or ∼6% of the stellar mass. Assuming that one-third of the nebular mass comprises sweptup interstellar gas, we estimate an implied mass-loss rate of~´-No clear signatures of circumstellar emission were found toward ζGem, RSPup, or XCyg, although in each case, line-of-sight confusion compromised portions of the spectral band. For the undetected stars, we derive model-dependent s 3 upper limits on the mass-loss rates, averaged over their lifetimes on the instability strip, of ´-10 6 ( -) yr −1 and estimate the total amount of mass lost to be less than a few percent of the stellar mass.

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A H I Imaging Survey of Asymptotic Giant Branch Stars

Cited by 21 publications

References 116 publications

The multi-scale environment of RS Cancri from CO and H I observations

The multi-scale environment of RS Cancri from CO and H I observations

Mass loss of stars on the asymptotic giant branch

A SEARCH FOR MASS LOSS ON THE CEPHEID INSTABILITY STRIP USING H i 21 cm LINE OBSERVATIONS

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