Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

Neilson, Hilding R.; Ignace, Richard; Smith, Beverly J.; Henson, G. D.; Adams, Alyssa

doi:10.1051/0004-6361/201424037

Cited by 5 publications

(7 citation statements)

References 58 publications

(87 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because we have considered spherical grains only, our simulations are less applicable to cases where magnetic fields likely play a role in aligning dust grains, such as the Galactic Center sources studied by Buchholz et al (2011Buchholz et al ( , 2013, but they may still provide useful insights. For systems with large polarization magnitudes such as V CVn (Neilson et al 2014) or the DSO (Shahzamanian et al 2016;Zajaček et al 2017b), our simulations provide lower limits to the observed polarization that can guide future modeling by diagnosing the presence of more complex circumstellar structures. In all cases, we find the most useful constraints are possible with polarization observations at multiple wavelengths, and encourage observers to make this a standard practice.…”

Section: Unresolved Bow Shockmentioning

confidence: 94%

“…An additional 𝐾-band observation of this object would allow more robust conclusions. Neilson et al (2014) proposed that an unresolved stellar wind bow shock could explain the large 𝑉-band intrinsic polarization (𝑝 𝑉 ≈ 1 − 6%) in the semi-regular variable V CVn. These authors attributed the time variability of their polarization measurements to pulsation-related variability in the density of the stellar wind.…”

Section: Unresolved Bow Shockmentioning

confidence: 99%

See 1 more Smart Citation

Polarization simulations of stellar wind bow shock nebulae – II. The case of dust scattering

Shrestha

Neilson

Hoffman

et al. 2020

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We study the polarization produced by scattering from dust in a bow shock-shaped region of enhanced density surrounding a stellar source, using the Monte Carlo radiative transfer code SLIP. Bow shocks are structures formed by the interaction of the winds of fast-moving stars with the interstellar medium. Our previous study focused on the polarization produced in these structures by electron scattering; we showed that polarization is highly dependent on inclination angle and that multiple scattering changes the shape and degree of polarization. In contrast to electron scattering, dust scattering is wavelength-dependent, which changes the polarization behaviour. Here we explore different dust particle sizes and compositions and generate polarized spectral energy distributions for each case. We find that the polarization SED behaviour depends on the dust composition and grain size. Including dust emission leads to polarization changes with temperature at higher optical depth in ways that are sensitive to the orientation of the bow shock. In various scenarios and under certain assumptions, our simulations can constrain the optical depth and dust properties of resolved and unresolved bow shock-shaped scattering regions.Constraints on optical depth can provide estimates of local ISM density for observed bow shocks. We also study the impact of dust grains filling the region between the star and bow shock. We see that as the density of dust between the star and bow shock increases, the resulting polarization is suppressed for all the optical depth regimes.

show abstract

Section: Unresolved Bow Shockmentioning

confidence: 94%

Section: Unresolved Bow Shockmentioning

confidence: 99%

Polarization simulations of stellar wind bow shock nebulae – II. The case of dust scattering

Shrestha

Neilson

Hoffman

et al. 2020

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

show abstract

“…In addition, V CVn exhibits most prominent inverse correlation between flux and fraction of polarization among other long-period variables. Neilson et al (2014) discussed the polarization variability of V CVn in detail. They considered qualitatively several hypotheses which can potentially describe unique behavior of the star.…”

Section: Introductionmentioning

confidence: 99%

The Circumstellar Envelope of the Semiregular Variable Star V CVn

et al. 2019

View full text Add to dashboard Cite

V CVn is a semiregular variable star with a V -band amplitude of ≈ 2 mag. This star has an unusually high amplitude of polarimetric variability: up to 6 per cent. It also exhibits a prominent inverse correlation between the flux and the fraction of polarization and a substantial constancy of the angle of polarization. To figure out the nature of these features, we observed the object using the Differential Speckle Polarimetry at three bands centered on 550, 625 and 880 nm using the 2.5-m telescope of Sternberg Astronomical Institute. The observations were conducted on 20 dates distributed over three cycles of pulsation. We detected an asymmetric reflection nebula consisting of three regions and surrounding the star at the typical distance of 35 mas. The components of the nebula change their brightness with the same period as the star, but with significant and different phase shifts. We discuss several hypotheses that could explain this behavior.

show abstract

“…For unresolved bow shocks (or cases in which a bow shock is predicted to exist, e.g. Neilson et al 2014), we measure a single polarization value corresponding to a single viewing angle. This corresponds to a horizontal line in figures such as Figs.…”

Section: Observational Implicationsmentioning

confidence: 99%

“…SLIP can also produce position angle maps for comparison with observations. The position angles in our models are consistently ≈ 0 • for most viewing angles, but flip to near 90 • at high inclinations and optical depths when q is negative.For unresolved bow shocks (or cases in which a bow shock is predicted to exist, e.g Neilson et al 2014…”

mentioning

confidence: 99%

Polarization simulations of stellar wind bow-shock nebulae – I. The case of electron scattering

Shrestha

Neilson

Hoffman

et al. 2018

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

Bow shocks and related density enhancements produced by the winds of massive stars moving through the interstellar medium provide important information regarding the motions of the stars, the properties of their stellar winds, and the characteristics of the local medium. Since bow shock nebulae are aspherical structures, light scattering within them produces a net polarization signal even if the region is spatially unresolved. Scattering opacity arising from free electrons and dust leads to a distribution of polarized intensity across the bow shock structure. That polarization encodes information about the shape, composition, opacity, density, and ionizsation state of the material within the structure. In this paper we use the Monte Carlo radiative transfer code SLIP to investigate the polarization created when photons scatter in a bow shock-shaped region of enhanced density surrounding a stellar source. We present results for electron scattering, and investigate the polarization behaviour as a function of optical depth, temperature, and source of photons for two different cases: pure scattering and scattering with absorption. In both regimes we consider resolved and unresolved cases. We discuss the implications of these results as well as their possible use along with observational data to constrain the properties of observed bow shock systems. In different situations and under certain assumptions, our simulations can constrain viewing angle, optical depth and temperature of the scattering region, and the relative luminosities of the star and shock.

show abstract

Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

Cited by 5 publications

References 58 publications

Polarization simulations of stellar wind bow shock nebulae – II. The case of dust scattering

Polarization simulations of stellar wind bow shock nebulae – II. The case of dust scattering

The Circumstellar Envelope of the Semiregular Variable Star V CVn

Polarization simulations of stellar wind bow-shock nebulae – I. The case of electron scattering

Contact Info

Product

Resources

About