The photometric behaviour of SU Dra, 1955–2000

Abstract

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.

Revisiting the Kepler non-Blazhko RR Lyrae sample: cycle-to-cyle variations and additional modes

“…Although Chadid (2000) and Chadid & Preston (2013) reported spectroscopic C2C variations of RR Lyrae stars, on ground-based photometric basis only marginal signs of such an effect were published (e.g. Barcza 2002;Jurcsik et al 2008). On space photometric basis no similar C2C variation of non-Blazhko RRab stars have been reported ever before, so we checked our finding carefully.…”

Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models - I. Theory and practical implementation

“…Barcza (2002) derived good quality light curves of the RRab star SU Dra by homogenizing 45 yr of UBV ( RI ) C observations (see his table 7). The method described in the previous section will now be applied.…”

“…To give a good impression of the accuracy of inverting the UBV(RI) C photometry to physical parameters, the comparison star BD +67 • 708 was used, because its colours are similar to those of SU Dra (table 3 in Barcza 2002). The results are [M] = −0.77 ± 0.03, E(B − V) = 0.000, ϑ = (1.913 ± 0.002) × 10 −10 rad, log g = 3.59 ± 0.01 and T e = 7505 ± 5 K. The errors are roughly in the same order of magnitude as those of SU Dra when Conditions I and II are satisfied.…”

“…Consequently, assuming a typical chemical composition means that μ = 1.3 is the appropriate choice in h 0 (R, t). Barcza (2002) derived good quality light curves of the RRab star SU Dra by homogenizing 45 yr of UBV(RI) C observations (see his (Liu & Janes 1990), the basic quantities for (10) are summarized in Table 1 for different phases. Fig.…”

Five colour photometry of the RRd star V372 Serpentis

“…They are smooth: humps or bumps indicating atmospheric shocks are not present, in contrast with the ascending branch of e.g. SU Dra (Preston & Paczynski 1964;Barcza 2002). The duration of an ascending branch is ≈P 1 /2.…”