Analyses of the Short-Period Cepheid SU Cassiopeiae

Milone, Eugene F.; Wilson, William Jerome; Volk, Kevin

doi:10.1086/301115

Cited by 5 publications

(6 citation statements)

References 37 publications

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“…Before our interferometric works Mérand et al 2006Mérand et al , 2007, the nebula around RS Pup was the only certain case of a direct relationship between a Cepheid and interstellar material. Another Cepheid, SU Cas, also appears close to a reflection nebula (Milone et al 1999;Turner & Evans 1984), but the physical association is more uncertain. The nebulosity around RS Pup was discovered by Westerlund (1961).…”

Section: Introductionmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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Context. The bright southern Cepheid RS Pup is surrounded by a circumstellar nebula reflecting the light from the central star. The propagation of the light variations from the Cepheid inside the dusty nebula creates spectacular light echoes that can be observed up to large distances from the star itself. This phenomenon is currently unique in this class of stars. Aims. For this relatively distant star, the trigonometric parallax available from Hipparcos has a low accuracy. A careful observation of the light echoes has the potential to provide a very accurate, geometric distance to RS Pup. Methods. We obtained a series of CCD images of RS Pup with the NTT/EMMI instrument covering the variation period of the star (P = 41.4 d), allowing us to track the progression of the light wavefronts over the nebular features surrounding the star. We measured precisely the phase lag of the photometric variation in several regions of the circumstellar nebula. Results. From our phase lag measurements, we derive a geometric distance of 1992 ± 28 pc to RS Pup. This distance is affected by a total uncertainty of 1.4%, and corresponds to a parallax of π = 0.502 ± 0.007 mas and a distance modulus of µ = 11.50 ± 0.03. Conclusions. The geometric distance we derive is by far the most accurate to a Cepheid, and among the most accurate to any star. RS Pup appears both as somewhat neglected and particularly promising to investigate the mass-loss history of Cepheids. Thanks to its highly accurate distance, it is also bound to become an important luminosity fiducial for the long period part of the period-luminosity diagram.

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Section: Introductionmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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“…The implied mean radius of SU Cas according to the Cepheid period–radius relation of Turner et al (2010), which is tied to the almost identical slopes for the Cepheid period–radius relation in studies by Gieren, Barnes & Moffett (1989), Laney & Stobie (1995), Gieren, Fouqué & Gómez (1998) and Turner & Burke (2002), is 25.0 R ⊙ . By comparison, the surface brightness technique yields a mean radius of 28.0 ± 0.8 R ⊙ , while an independent Baade–Wesselink analysis using infrared colours by Milone, Wilson & Volk (1999) produced an estimate of 33.0 ± 1.1 R ⊙ . The last study also summarizes previous estimates for the mean radius of SU Cas derived from variants of the Baade–Wesselink method, most of which lie in the range 30–45 R ⊙ .…”

Section: Su Cas As a Member Of Alessi 95mentioning

confidence: 99%

“…The last study also summarizes previous estimates for the mean radius of SU Cas derived from variants of the Baade–Wesselink method, most of which lie in the range 30–45 R ⊙ . Systematic effects cannot be discounted, given the small amplitude of the light variations in SU Cas and the fact that Milone et al (1999) adopted a projection factor of p = 1.39 in their study. Laney & Joner (2009) find a value of p = 1.277 to be more suitable for SU Cas, which would reduce the Milone et al (1999) value to 30.3 ± 1.0 R ⊙ .…”

Section: Su Cas As a Member Of Alessi 95mentioning

confidence: 99%

“…Systematic effects cannot be discounted, given the small amplitude of the light variations in SU Cas and the fact that Milone et al (1999) adopted a projection factor of p = 1.39 in their study. Laney & Joner (2009) find a value of p = 1.277 to be more suitable for SU Cas, which would reduce the Milone et al (1999) value to 30.3 ± 1.0 R ⊙ . The VJK photometry used by Laney & Joner (2009) leads to a mean radius of 28.5 R ⊙ for SU Cas, while Turner & Burke (2002) obtained a radius of 19.0 ± 0.7 R ⊙ using a Baade–Wesselink analysis tied to KHG photometry.…”

Section: Su Cas As a Member Of Alessi 95mentioning

confidence: 99%

“…The implied mean radius of SU Cas according to the Cepheid period-radius relation of Turner et al (2010), which is tied to the almost identical slopes for the Cepheid period-radius relation in studies by Gieren, Barnes & Moffett (1989), Laney & Stobie (1995), Gómez (1998), andBurke (2002), is 25.0 R ⊙ . By comparison, the surface brightness technique yields a mean radius of 28.0 ± 0.8 R ⊙ , while an independent Baade-Wesselink analysis using infrared colours by Milone et al (1999) Meynet et al (1993). Additionally, the implied age of log t = 8.2 for SU Cas from its membership in Alessi 95 provides a key point at the short-period end of a semi-empirical period-age relationship for cluster Cepheids developed by Turner (2012), where again the dispersion is no larger than ±0.1 in log t and the relationship is generated by isochrone fits to clusters containing Galactic Cepheids.…”

Section: Su Cas As a Member Of Alessi 95mentioning

confidence: 99%

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Alessi 95 and the short-period Cepheid SU Cassiopeiae

Turner

Majaess

Lane

et al. 2012

Monthly Notices of the Royal Astronomical Society

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The parameters for the newly discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically observed B‐ and A‐type stars near SU Cas follow a reddening relation described by E(U−B)/E(B−V) = 0.83 + 0.02E(B−V), implying a value of R=AV/E(B−V) ≃ 2.8 for the associated dust. Alessi 95 has a mean reddening of E(B−V)(B0) = 0.35 ± 0.02 s.e., an intrinsic distance modulus of V0−MV= 8.16 ± 0.04 s.e. (±0.21 s.d.), d= 429 ± 8 pc, and an estimated age of 108.2 yr from zero‐age main sequence (ZAMS) fitting of available UBV, CCD BV, NOMAD, and Two Micron All Sky Survey JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B−V) = 0.33 ± 0.02 and a luminosity of 〈MV〉=−3.15 ± 0.07 s.e., consistent with overtone pulsation (PFM= 2.75 d), as also implied by the Cepheid’s light‐curve parameters, rate of period increase and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, its pulsation parallax derived from the infrared surface brightness technique and Hipparcos parallaxes, which all agree to within a few per cent.

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The Distance Scale for Classical Cepheid Variables

Turner

Burke

2002

The Astronomical Journal

117

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Field reddenings are summarized for 68 Cepheids from published studies and updated results presented here. The compilation forms the basis for a comparison with other published reddening scales of Cepheids, including those established from reddening-independent indices, photometry on the Lick six-color system, Strömgren system, Walraven system, Washington system, Cape BVI system, DDO system, and Geneva system, IRSB studies, and Cepheid spectroscopy, both old and new. Reddenings tied to period-color relations are the least reliable, as expected, while photometric color excesses vary in precision, their accuracy depending on the methodology and calibration sample. The tests provide insights into the accuracy and precision of published Cepheid reddening scales, and lead to a new system of standardized reddenings comprising a sample of 198 variables with an average uncertainty of ±0.028 in E B−V , the precision being less than ±0.01 for many. The collected color excesses are used to map the dispersion in intrinsic colors as a function of pulsation period, the results contradicting current perceptions about the period dependence of dispersion in Cepheid effective temperatures.

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Analyses of the Short-Period Cepheid SU Cassiopeiae

Cited by 5 publications

References 37 publications

The long-period Galactic Cepheid RS Puppis

The long-period Galactic Cepheid RS Puppis

Alessi 95 and the short-period Cepheid SU Cassiopeiae

The Distance Scale for Classical Cepheid Variables

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