The long-period Galactic Cepheid RS Puppis

III. A geometric distance from HST polarimetric imaging of its light echoes

P. Kervella, Howard E. Bond, M. Cracraft, L. Szabados, J. Breitfelder, A. Mérand, W. B. Sparks, A. Gallenne, D. Bersier, P. Fouqué, R. I. Anderson

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

As one of the most luminous Cepheids in the Milky Way, the 41.5-day RS Puppis is an analog of the long-period Cepheids used to measure extragalactic distances. An accurate distance to this star would therefore help anchor the zero-point of the bright end of the period-luminosity relation. But, at a distance of about 2 kpc, RS Pup is too far away for measuring a direct trigonometric parallax with a precision of a few percentage points with existing instrumentation. RS Pup is unique by being surrounded by a reflection nebula whose brightness varies as pulses of light from the Cepheid propagate outward. We present new polarimetric imaging of the nebula obtained with HST/ACS. The derived map of the degree of linear polarization p L allows us to reconstruct the three-dimensional structure of the dust distribution. To retrieve the scattering angle from the p L value, we consider two different polarization models, one based on a Milky Way dust mixture and one assuming Rayleigh scattering. Considering the derived dust distribution in the nebula, we adjust a model of the phase lag of the photometric variations over selected nebular features to retrieve the distance of RS Pup. We obtain a distance of 1910 ± 80 pc (4.2%), corresponding to a parallax of π = 0.524 ± 0.022 mas. The agreement between the two polarization models that we considered is good, but the final uncertainty is dominated by systematics in the adopted model parameters. The distance we obtain is consistent with existing measurements from the literature, but light echoes provide a distance estimate that is not subject to the same systematic uncertainties as other estimators (e.g., the Baade-Wesselink technique). RS Pup therefore provides an important fiducial for calibrating the systematic uncertainties of the long-period Cepheid distance scale.

Original languageEnglish (US)
Article numberA7
JournalAstronomy and Astrophysics
Volume572
DOIs
StatePublished - Dec 1 2014

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echoes
polarization
dust
scattering
parallax
nebulae
anchor
instrumentation
reflection nebulae
Rayleigh scattering
calibrating
linear polarization
estimators
brightness
time lag
luminosity
analogs
stars
distribution
estimates

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kervella, P. ; Bond, Howard E. ; Cracraft, M. ; Szabados, L. ; Breitfelder, J. ; Mérand, A. ; Sparks, W. B. ; Gallenne, A. ; Bersier, D. ; Fouqué, P. ; Anderson, R. I. / The long-period Galactic Cepheid RS Puppis : III. A geometric distance from HST polarimetric imaging of its light echoes. In: Astronomy and Astrophysics. 2014 ; Vol. 572.
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title = "The long-period Galactic Cepheid RS Puppis: III. A geometric distance from HST polarimetric imaging of its light echoes",
abstract = "As one of the most luminous Cepheids in the Milky Way, the 41.5-day RS Puppis is an analog of the long-period Cepheids used to measure extragalactic distances. An accurate distance to this star would therefore help anchor the zero-point of the bright end of the period-luminosity relation. But, at a distance of about 2 kpc, RS Pup is too far away for measuring a direct trigonometric parallax with a precision of a few percentage points with existing instrumentation. RS Pup is unique by being surrounded by a reflection nebula whose brightness varies as pulses of light from the Cepheid propagate outward. We present new polarimetric imaging of the nebula obtained with HST/ACS. The derived map of the degree of linear polarization p L allows us to reconstruct the three-dimensional structure of the dust distribution. To retrieve the scattering angle from the p L value, we consider two different polarization models, one based on a Milky Way dust mixture and one assuming Rayleigh scattering. Considering the derived dust distribution in the nebula, we adjust a model of the phase lag of the photometric variations over selected nebular features to retrieve the distance of RS Pup. We obtain a distance of 1910 ± 80 pc (4.2{\%}), corresponding to a parallax of π = 0.524 ± 0.022 mas. The agreement between the two polarization models that we considered is good, but the final uncertainty is dominated by systematics in the adopted model parameters. The distance we obtain is consistent with existing measurements from the literature, but light echoes provide a distance estimate that is not subject to the same systematic uncertainties as other estimators (e.g., the Baade-Wesselink technique). RS Pup therefore provides an important fiducial for calibrating the systematic uncertainties of the long-period Cepheid distance scale.",
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Kervella, P, Bond, HE, Cracraft, M, Szabados, L, Breitfelder, J, Mérand, A, Sparks, WB, Gallenne, A, Bersier, D, Fouqué, P & Anderson, RI 2014, 'The long-period Galactic Cepheid RS Puppis: III. A geometric distance from HST polarimetric imaging of its light echoes', Astronomy and Astrophysics, vol. 572, A7. https://doi.org/10.1051/0004-6361/201424395

The long-period Galactic Cepheid RS Puppis : III. A geometric distance from HST polarimetric imaging of its light echoes. / Kervella, P.; Bond, Howard E.; Cracraft, M.; Szabados, L.; Breitfelder, J.; Mérand, A.; Sparks, W. B.; Gallenne, A.; Bersier, D.; Fouqué, P.; Anderson, R. I.

In: Astronomy and Astrophysics, Vol. 572, A7, 01.12.2014.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The long-period Galactic Cepheid RS Puppis

T2 - III. A geometric distance from HST polarimetric imaging of its light echoes

AU - Kervella, P.

AU - Bond, Howard E.

AU - Cracraft, M.

AU - Szabados, L.

AU - Breitfelder, J.

AU - Mérand, A.

AU - Sparks, W. B.

AU - Gallenne, A.

AU - Bersier, D.

AU - Fouqué, P.

AU - Anderson, R. I.

PY - 2014/12/1

Y1 - 2014/12/1

N2 - As one of the most luminous Cepheids in the Milky Way, the 41.5-day RS Puppis is an analog of the long-period Cepheids used to measure extragalactic distances. An accurate distance to this star would therefore help anchor the zero-point of the bright end of the period-luminosity relation. But, at a distance of about 2 kpc, RS Pup is too far away for measuring a direct trigonometric parallax with a precision of a few percentage points with existing instrumentation. RS Pup is unique by being surrounded by a reflection nebula whose brightness varies as pulses of light from the Cepheid propagate outward. We present new polarimetric imaging of the nebula obtained with HST/ACS. The derived map of the degree of linear polarization p L allows us to reconstruct the three-dimensional structure of the dust distribution. To retrieve the scattering angle from the p L value, we consider two different polarization models, one based on a Milky Way dust mixture and one assuming Rayleigh scattering. Considering the derived dust distribution in the nebula, we adjust a model of the phase lag of the photometric variations over selected nebular features to retrieve the distance of RS Pup. We obtain a distance of 1910 ± 80 pc (4.2%), corresponding to a parallax of π = 0.524 ± 0.022 mas. The agreement between the two polarization models that we considered is good, but the final uncertainty is dominated by systematics in the adopted model parameters. The distance we obtain is consistent with existing measurements from the literature, but light echoes provide a distance estimate that is not subject to the same systematic uncertainties as other estimators (e.g., the Baade-Wesselink technique). RS Pup therefore provides an important fiducial for calibrating the systematic uncertainties of the long-period Cepheid distance scale.

AB - As one of the most luminous Cepheids in the Milky Way, the 41.5-day RS Puppis is an analog of the long-period Cepheids used to measure extragalactic distances. An accurate distance to this star would therefore help anchor the zero-point of the bright end of the period-luminosity relation. But, at a distance of about 2 kpc, RS Pup is too far away for measuring a direct trigonometric parallax with a precision of a few percentage points with existing instrumentation. RS Pup is unique by being surrounded by a reflection nebula whose brightness varies as pulses of light from the Cepheid propagate outward. We present new polarimetric imaging of the nebula obtained with HST/ACS. The derived map of the degree of linear polarization p L allows us to reconstruct the three-dimensional structure of the dust distribution. To retrieve the scattering angle from the p L value, we consider two different polarization models, one based on a Milky Way dust mixture and one assuming Rayleigh scattering. Considering the derived dust distribution in the nebula, we adjust a model of the phase lag of the photometric variations over selected nebular features to retrieve the distance of RS Pup. We obtain a distance of 1910 ± 80 pc (4.2%), corresponding to a parallax of π = 0.524 ± 0.022 mas. The agreement between the two polarization models that we considered is good, but the final uncertainty is dominated by systematics in the adopted model parameters. The distance we obtain is consistent with existing measurements from the literature, but light echoes provide a distance estimate that is not subject to the same systematic uncertainties as other estimators (e.g., the Baade-Wesselink technique). RS Pup therefore provides an important fiducial for calibrating the systematic uncertainties of the long-period Cepheid distance scale.

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