Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid*

Bond, Howard E.; Nelan, Edmund; Evans, Nancy Remage; Schaefer, Gail H.; Harmer, Dianne

doi:10.3847/1538-4357/aaa3f9

Cited by 207 publications

(22 citation statements)

References 61 publications

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“…The only accurate average magnitudes based on several pulsation cycles were found in the AAVSO database that provides J = 0.93 ± 0.01 mag and H = 0.67 ± 0.01 mag in the UKIRT system. Additionally, the uncertain pulsation mode and the age difference between the Cepheid and its companion raise questions concerning the properties of α UMi and whether it should be included in PL relation fits (Anderson 2018;Bond et al 2018 ; Table 1. Sample of Cepheids in resolved binary systems taken from Kervella et al (2019): parameters of the Cepheids and of their stable companions.…”

Section: Parallaxes Of Cepheid Resolved Companionsmentioning

confidence: 99%

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

Breuval

Kervella

Anderson

et al. 2020

A&A

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Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance ladder. Milky Way Cepheids are the only stars in this class accessible to trigonometric parallax measurements. However, the parallaxes of Cepheids from the second Gaia data release (GDR2) are affected by systematics because of the absence of chromaticity correction, and occasionally by saturation. Methods. As a proxy for the parallaxes of 36 Galactic Cepheids, we adopt either the GDR2 parallaxes of their spatially resolved companions or the GDR2 parallax of their host open cluster. This novel approach allows us to bypass the systematics on the GDR2 Cepheids parallaxes that is induced by saturation and variability. We adopt a GDR2 parallax zero-point (ZP) of −0.046 mas with an uncertainty of 0.015 mas that covers most of the recent estimates. Results. We present new Galactic calibrations of the Leavitt law in the V, J, H, KS, and Wesenheit WH bands. We compare our results with previous calibrations based on non-Gaia measurements and compute a revised value for the Hubble constant anchored to Milky Way Cepheids. Conclusions. From an initial Hubble constant of 76.18 ± 2.37 km s−1 Mpc−1 based on parallax measurements without Gaia, we derive a revised value by adopting companion and average cluster parallaxes in place of direct Cepheid parallaxes, and we find H0 = 72.8 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 when all Cepheids are considered and H0 = 73.0 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 for fundamental mode pulsators only.

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Section: Parallaxes Of Cepheid Resolved Companionsmentioning

confidence: 99%

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

Breuval

Kervella

Anderson

et al. 2020

A&A

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“…One component was removed from the list as the binary can not be resolved by Gaia. Some recent works by van Belle et al ( 2020) and Bond et al (2018) (on Polaris B) are added to give a list of 102 targets. The method-ology to use the WFC3 to obtain parallaxes was described in Riess et al (2014) and Casertano et al (2016) and has been used to obtain distances to eight CCs (Riess et al 2014(Riess et al , 2018a.…”

Section: Sources With Trigonometric Parallax Determinationsmentioning

confidence: 99%

The parallax zero point offset from Gaia EDR3 data

Groenewegen

2021

Preprint

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The second data release of Gaia revealed a parallax zero point offset of −0.029 mas based on quasars. The value depended on the position on the sky, and also likely on magnitude and colour. The offset and its dependence on other parameters inhibited an improvement in the local distance scale using e.g. the Cepheid and RR Lyrae period-luminosity relations. Analysis of the recent Gaia Early Data Release 3 (EDR3) reveals a mean parallax zero point offset of −0.021 mas based on quasars. The Gaia team addresses the parallax zero point offset in detail and proposes a recipe to correct for it, based on ecliptic latitude, G-band magnitude, and colour information. This paper is a completely independent investigation into this issue focussing on the spatial dependence of the correction based on quasars and the magnitude dependence based on wide binaries. The spatial and magnitude corrections are connected to each other in the overlap region between 17 < G < 19. The spatial correction is presented at several spatial resolutions based on the HEALPix formalism. The colour dependence of the parallax offset is unclear and in any case secondary to the spatial and magnitude dependence. The spatial and magnitude corrections are applied to two samples of brighter sources, namely a sample of ∼100 stars with independent trigonometric parallax measurements from HST data, and a sample of 75 classical cepheids using photometric parallaxes. The mean offset between the observed GEDR3 parallax and the independent trigonometric parallax (excluding outliers) is about −39 µas, and after applying the correction it is consistent with being zero. For the classical cepheid sample it is suggested that the photometric parallaxes may be underestimated by about 5%.

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“…The only accurate average magnitudes based on several pulsation cycles were found in the AAVSO database that provides J = 0.93 ± 0.01 mag and H = 0.67 ± 0.01 mag in the UKIRT system. Additionally, the uncertain pulsation mode as well as the age difference between the Cepheid and its companion raise questions concerning the properties of α UMi and whether it should be included in PL-relation fits (Anderson 2018;Bond et al 2018;Groenewegen 2018). We decided to exclude this star from our sample.…”

Section: Appendix C: Pulsation Modesmentioning

confidence: 99%

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

Breuval,

Kervella,

Anderson

et al. 2020

Preprint

View full text Add to dashboard Cite

Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance ladder. Milky Way Cepheids are the only stars of this class accessible to trigonometric parallax measurements. However, the parallaxes of Cepheids from the second Gaia data release (GDR2) are affected by systematics due to the absence of chromaticity correction and occasionally by saturation. Methods. As a proxy for the parallaxes of 36 Galactic Cepheids, we adopt either the GDR2 parallaxes of their spatially resolved companions or the GDR2 parallax of their host open cluster. This novel approach allows us to bypass the systematics on the GDR2 Cepheids parallaxes that is induced by saturation and variability. We adopt a GDR2 parallax offset of 0.046 mas with an uncertainty of 0.015 mas that covers most of the recent estimates. Results. We present new Galactic calibrations of the Leavitt law in the V, J, H, K S and Wesenheit W H bands. We compare our results with previous measurements from the Hubble Space Telescope (HST) and compute a revised value for the Hubble constant anchored to Milky Way Cepheids. Conclusions. From an initial Hubble constant of 76.18 ± 2.37 km s −1 Mpc −1 based on parallax measurements without Gaia, we derive a revised value by adopting companion and average cluster parallaxes in place of direct Cepheid parallaxes and we find H 0 = 73.07 ± 1.75 (stat. + syst.) ± 1.88 (ZP) km s −1 Mpc −1 when all Cepheids are considered, and H 0 = 73.51 ± 1.76 (stat. + syst.) ± 1.91 (ZP) km s −1 Mpc −1 for fundamental mode pulsators only.

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Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid*

Cited by 207 publications

References 61 publications

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

The parallax zero point offset from Gaia EDR3 data

The Milky Way Cepheid Leavitt law based on Gaia DR2 parallaxes of companion stars and host open cluster populations

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