On the Enhancement of Mass Loss in Cepheids Due to Radial Pulsation

Neilson, Hilding R.; Lester, John B.

doi:10.1086/588650

Cited by 75 publications

(83 citation statements)

References 61 publications

(86 reference statements)

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“…The values given by our DUSTY models agree. They are also consistent with the predicted massloss rate from Neilson & Lester (2008), ranging from 10 −10 to 10 −7 M yr −1 .…”

Section: Discussionsupporting

confidence: 87%

“…This behavior might be explained by the stronger velocity fields in longer-period Cepheids, and the presence of shock waves at certain pulsation phases (Nardetto et al 2006(Nardetto et al , 2008. This scenario is consistent with the theoretically predicted range, 10 −10 −10 −7 M yr −1 , of Neilson & Lester (2008), based on a pulsation-driven mass-loss model. Neilson et al (2011) also found that a pulsation-driven mass-loss model combined with moderate convective-core overshooting provides an explanation for the Cepheid mass discrepancy, where stellar evolution masses differ by 10−20% from stellar pulsation calculations.…”

Section: T Monsupporting

confidence: 89%

“…We used a grain size distribution following a standard Mathis-Rumpl-Nordsieck (MRN) relation (Mathis et al 1977), that is, n(a) ∝ a 3.5 for 0.005 a 0.25 µm. We chose a spherical density distribution in the shell following a radiatively driven wind, because Cepheids are giant stars and might lose mass via stellar winds (Neilson & Lester 2008). In this case, DUSTY computes the density structure by solving the hydrodynamics equations, coupled to the radiative transfer equations.…”

Section: Single Dust Shell Modelmentioning

confidence: 99%

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Extended envelopes around Galactic Cepheids

Gallenne

Mérand

Kervella

et al. 2013

A&A

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Aims. We study the close environment of nearby Cepheids using high spatial resolution observations in the mid-infrared with the VLTI/MIDI instrument, a two-beam interferometric recombiner. Methods. We obtained spectra and visibilities for the classical Cepheids X Sgr and T Mon. We fitted the MIDI measurements, supplemented by B, V, J, H, K literature photometry, with the numerical transfer code DUSTY to determine the dust shell parameters. We used a typical dust composition for circumstellar environments. Results. We detect an extended dusty environment in the spectra and visibilities for both stars, although T Mon might suffer from thermal background contamination. We attribute this to the presence of a circumstellar envelope (CSE) surrounding the Cepheids. This is optically thin for X Sgr (τ 0.55 µm = 0.008), while it appears to be thicker for T Mon (τ 0.55 µm = 0.15). They are located at about 15−20 stellar radii. Following our previous work, we derived a likely period-excess relation in the VISIR PAH1 filter, f 8.6 µm [%]= 0.81(±0.04)P[day]. We argue that the impact of CSEs on the mid-IR period-luminosity (P−L) relation cannot be negligible because they can bias the Cepheid brightness by up to about 30%. For the K-band P−L relation, the CSE contribution seems to be lower (<5%), but the sample needs to be enlarged to firmly conclude that the impact of the CSEs is negligible in this band.

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“…The values given by our DUSTY models agree. They are also consistent with the predicted massloss rate from Neilson & Lester (2008), ranging from 10 −10 to 10 −7 M yr −1 .…”

Section: Discussionsupporting

confidence: 87%

Section: T Monsupporting

confidence: 89%

Section: Single Dust Shell Modelmentioning

confidence: 99%

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Extended envelopes around Galactic Cepheids

Gallenne

Mérand

Kervella

et al. 2013

A&A

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“…Another consequence is that the dusty nebula is not a good candidate to resolve a possible evolutionary vs. pulsational mass discrepancy for RS Pup (see e.g. Keller 2008;Caputo et al 2005;Neilson & Lester 2008, 2009). However, the compact and hot envelope observed by Kervella et al (2009) still appears as a plausible contributor.…”

Section: Resultsmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand²,

Szabados³

et al. 2012

A&A

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Context. The southern long-period Cepheid RS Pup is surrounded by a large circumstellar dusty nebula reflecting the light from the central star. Due to the changing luminosity of the central source, light echoes propagate into the nebula. This remarkable phenomenon was the subject of Paper I. The origin and physical properties of the nebula are however uncertain: it may have been created through mass loss from the star itself, or it could be the remnant of a pre-existing interstellar cloud. Aims. Our goal is to determine the three-dimensional structure of the light-scattering nebula, and estimate its mass. This will bring us new clues on the origin of the nebula. Knowing the geometrical shape of the nebula will also allow us to retrieve the distance of RS Pup in an unambiguous manner using a model of its light echoes (in a forthcoming work). Methods. The scattering angle of the Cepheid light in the circumstellar nebula can be recovered from its degree of linear polarization. We thus observed the nebula surrounding RS Pup using the polarimetric imaging mode of the VLT/FORS instrument, and obtained a map of the degree and position angle of linear polarization. Results. From our FORS observations, we derive a three-dimensional map of the distribution of the dust around RS Pup, whose overall geometry is an irregular and geometrically thin layer. The nebula does not present a well-defined central symmetry. Using a simple scattering model, we derive a total dust mass of M dust = 2.9 ± 0.9 M for the light-scattering dust within 1.8 of the Cepheid. This translates into a total mass of M gas+dust = 290 ± 120 M , assuming a dust-to-gas ratio of M dust /M gas = 1.0 ± 0.3%. Conclusions. The high mass of the dusty nebula excludes that it was created by mass-loss from the star. However, the thinness of the dust distribution is an indication that the Cepheid participated to the shaping of the nebula, e.g. through its radiation pressure or stellar wind. RS Pup therefore appears as a regular long-period Cepheid located in an exceptionally dense interstellar environment.

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“…As shown by Mérand et al (2007), long period Cepheids tend to show brighter CSEs in the near-IR K band than short periods, indicating that the mass-loss mechanism could be linked to the pulsation of the star. Interestingly, pulsation driven mass loss models by Neilson & Lester (2008) predict lower mass loss rates for long periods compared to short periods. Using the same models, predicted a sufficiently large IR excess to impact the near and mid-IR P − L relations of LMC Cepheids.…”

Section: Introductionmentioning

confidence: 99%

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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Context. Compact circumstellar envelopes (CSEs) have been detected around several Cepheids by interferometry. In particular, observations with the VINCI instrument revealed in 2006 a compact envelope around the long period Cepheid Car (P = 35.5 days). Another Cepheid, RS Pup (P = 41.4 days), presents a large (≈2 ) circumstellar nebula scattering the Cepheid light in the visible. These envelopes are particularly interesting for two reasons: their presence could impact the Cepheid distance scale, and they could imply stellar mass loss. Aims. Our goal is to establish the spatial and spectral properties of the CSEs of Car and RS Pup. This is done through a parametrization of the envelopes in terms of fractional flux (with respect to the star) and angular size. Methods. We retrieved archival Spitzer images of the two stars (λ = 3.5−70 μm), and obtained new diffraction-limited imaging with the VLT/VISIR camera in BURST mode (λ = 8.6−11.9 μm), as well as interferometric observations with the VLTI/MIDI beam combiner (λ = 8−13 μm). This combination of single-telescope and interferometric techniques allows us to probe the envelopes of the two Cepheids over a broad range of angular scales, from arcminutes to milliarcseconds. Results. The circumstellar envelope of RS Pup is resolved spatially at 24 and 70 μm by Spitzer, and around 10 μm by MIDI and VISIR. The envelope of Car appears much more compact, and is resolved only in the VISIR and MIDI observations. The infrared excesses we detect around RS Pup and Car are both very significant, but differ considerably in spectral and spatial properties. We detect a warm component in the CSE of both stars at a spatial scale of a few 100 to a few 1000 AU. In addition, RS Pup presents a very large (several 100 000 AU) and cold (≈40 K) dusty envelope. Conclusions. The observed properties of the CSEs lead us to propose that the cold dust content of the large reflection nebula surrounding RS Pup has an interstellar origin, while the warm CSEs of the two stars were created by ongoing stellar mass loss. We also speculate that the NGC 7023 reflection nebula surrounding the Herbig Be star HD 200775 is an analogue of RS Pup at an age of 100 000 years. The presence of CSEs around the two brightest long-period Cepheids is an indication that many long-period members of this class, if not all, could be surrounded by warm circumstellar envelopes created by mass loss. However, very large dusty envelopes such as that of RS Pup are probably less common, as according to our scenario, they require the presence of a high dust density in the interstellar medium (ISM) at the time of the formation of the Cepheid progenitor.

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On the Enhancement of Mass Loss in Cepheids Due to Radial Pulsation

Cited by 75 publications

References 61 publications

Extended envelopes around Galactic Cepheids

Extended envelopes around Galactic Cepheids

The long-period Galactic Cepheid RS Puppis

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

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