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 language | English (US) |
|---|---|
| Article number | A7 |
| Journal | Astronomy and Astrophysics |
| Volume | 572 |
| DOIs | |
| State | Published - Dec 1 2014 |
Fingerprint
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Cite this
}
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 journal › Article
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.
UR - http://www.scopus.com/inward/record.url?scp=84913584012&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84913584012&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/201424395
DO - 10.1051/0004-6361/201424395
M3 - Article
VL - 572
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
M1 - A7
ER -