An Analysis of the Absolute Energy Distribution in the Spectrum of SU Draconis.

Oke, J. B.; Giver, L. P.; Searle, Leonard

doi:10.1086/147392

Cited by 32 publications

(42 citation statements)

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“…The observed −pv radial (ϕ) (Liu & Janes 1989;Oke et al 1962) does not show the undulation ofθ 0 d, and the assumption of an eventually phase dependent conversion factor (Sabbey et al 1995) cannot bring the curves to congruence. For a few variables in M5 and M92 a similar undulation of ϑ 0 (ϕ) was shown graphically by Cohen (1992); however, it was not discussed.…”

Section: The Results For Su Dramentioning

confidence: 85%

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Distance and mass of pulsating stars from multicolour photometry and atmospheric models

Barcza

2003

A&A

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Abstract. For determining distance and mass of pulsating stars a new, purely photometric method is described in which radial velocity observations are not needed. From multicolour photometry the variation of angular diameter is determined in a conventional way by using the surface brightness of the theoretical atmospheric models ATLAS of Kurucz (1997). As a function of phase the following two parameters are introduced in the Navier-Stokes equation: gravity (of the appropriate static ATLAS model), and angular diameter. Distance and mass are derived from phases of standstill. Conclusions are drawn on the hydrodynamic behaviour of the atmosphere. The new method is compared with the Baade-Wesselink (BW) method. As an example the RR Lyrae variable SU Dra is given: using UBVR C photometry, a distance of 647 ± 16 pc, and a mass of 0.66 ± .03 M were found. In addition to the radius change (4.58−5.51) R radius undulations have been found with amplitude ≈0.2 R and period P/5, which are synchronized with the main period P = 0. d 66042. The present method has confirmed the distance value from the BW method; thus, in the problem of different distance scales from BW and other methods the short extragalactic distance scale has been bolstered by an independent argument. The mass is some 30 percent larger than the value from the equation of pulsation of van Albada & Baker (1971).

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Section: The Results For Su Dramentioning

confidence: 85%

“…Liu & Janes 1989) or from weak metallic lines (e.g. Oke et al 1962). In the present method v radial (ϕ), v γ , p, and an eventual arbitrary phase shift of the radius change from photometry and radial velocity (e.g.…”

Section: Appraisal Of the Method Comparison With The Bw Techniquementioning

confidence: 95%

Distance and mass of pulsating stars from multicolour photometry and atmospheric models

Barcza

2003

A&A

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“…They are formed at different depths, and therefore RV curves from different lines have different shapes, amplitudes, and zero points (shown e.g. by Sanford 1949;Oke et al 1962). Since available RV measurements are based on various lines, it was necessary to unify them.…”

Section: Radial Velocitiesmentioning

confidence: 99%

New analysis of the light time effect in TU Ursae Majoris

Liška

Skarka

Mikulášek

et al. 2016

A&A

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Context. Recent statistical studies prove that the percentage of RR Lyrae pulsators that are located in binaries or multiple stellar systems is considerably lower than might be expected. This can be better understood from an in-depth analysis of individual candidates. We investigate in detail the light time effect of the most probable binary candidate TU UMa. This is complicated because the pulsation period shows secular variation. Aims. We model possible light time effect of TU UMa using a new code applied on previously available and newly determined maxima timings to confirm binarity and refine parameters of the orbit of the RRab component in the binary system. The binary hypothesis is also tested using radial velocity measurements. Methods. We used new approach to determine brightness maxima timings based on template fitting. This can also be used on sparse or scattered data. This approach was successfully applied on measurements from different sources. To determine the orbital parameters of the double star TU UMa, we developed a new code to analyse light time effect that also includes secular variation in the pulsation period. Its usability was successfully tested on CL Aur, an eclipsing binary with mass-transfer in a triple system that shows similar changes in the O-C diagram. Since orbital motion would cause systematic shifts in mean radial velocities (dominated by pulsations), we computed and compared our model with centre-of-mass velocities. They were determined using high-quality templates of radial velocity curves of RRab stars. Results. Maxima timings adopted from the GEOS database (168) together with those newly determined from sky surveys and new measurements (85) were used to construct an O-C diagram spanning almost five proposed orbital cycles. This data set is three times larger than data sets used by previous authors. Modelling of the O-C dependence resulted in 23.3-yr orbital period, which translates into a minimum mass of the second component of about 0.33 M . Secular changes in the pulsation period of TU UMa over the whole O-C diagram were satisfactorily approximated by a parabolic trend with a rate of −2.2 ms yr −1 . To confirm binarity, we used radial velocity measurements from nine independent sources. Although our results are convincing, additional long-term monitoring is necessary to unambiguously confirm the binarity of TU UMa.

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“…Spectrophotometry was published by Oke et al (1962) covering the wave length range from ultraviolet to visual which could be converted to Johnson UBV colours by using the Vilnius filters of Azusienis & Strayzis (1969) and spectrophotometry to the Vega calibration of Tüg et al (1977). A phase shift of 0.02 was applied to be in accordance with the phasing in the present paper.…”

Section: The Observational Data Basismentioning

confidence: 99%

The photometric behaviour of SU Dra, 1955–2000

Barcza

2002

A&A

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Abstract.A multicolour photometric data basis is compiled for SU Dra from 356 Johnson UBV and 228 UBV (RI)C observations reported in this paper, in addition to 483 BV , 289 UBV , and 85 UBV RI observations found in the literature. Mean period, period change (4.40 ± .14) × 10 −10 day/day, and phase noise are derived from the V light curves by a variational procedure minimizing the length of the folded light curve (string length minimization, SLM). From variation of string length in the neighbourhood of minimum, observational error of photometry, observed amplitude, number of observations formulae are derived for the error of period and phase noise by statistical and analytical considerations. Secondary periodic variations are excluded to a few mmag level, indication of amplitude variation (Blazhko-effect) has not been found, however, systematic segregation of light curve segments is reported from different epochs in the descending branch before the brightness rise. Mean light and colour curves are derived from photometry and they are compared with those from integration of spectrophotometric observations. The period change is interpreted in terms of mixing events in the stellar interior.

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An Analysis of the Absolute Energy Distribution in the Spectrum of SU Draconis.

Cited by 32 publications

References 0 publications

Distance and mass of pulsating stars from multicolour photometry and atmospheric models

Distance and mass of pulsating stars from multicolour photometry and atmospheric models

New analysis of the light time effect in TU Ursae Majoris

The photometric behaviour of SU Dra, 1955–2000

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