Bright Blazhko RRab Lyrae stars observed by ASAS and the SuperWASP surveys

Abstract

Aims. Period study of 321 fundamental mode RR Lyrae type stars (RRab), which had appropriate data in ASAS and SuperWASP surveys, was performed to complement and extend the list of known Blazhko stars in galactic field with bright stars up to 12.5 mag in maximum light.Methods. An individual approach was applied to each studied star. Permanent visual supervision was maintained to each procedure in data analysis (data cleaning, frequency spectra examination) to avoid missing any possible sign of the Blazhko effect. Period analysis was performed using Period04 software. Results. We found 100 stars to be definitely modulated. In 25 cases, previously unknown modulation was revealed and 8 new candidates for Blazhko stars were identified. Their modulation needs to be confirmed. In 18 previously found Blazhko stars, no modulation was detectable. Multiple modulation was revealed for eight stars that were previously proposed to show simple modulation. In total, there were twelve stars with some peculiarity in their modulation in the sample. This brings the incidence rate of multiple/irregularlymodulated stars to 12%. The ratio of the modulation periods of five of the double-modulated stars was within the ratios of small integers. One of stars studied, IK Hya, showed a very interesting frequency spectrum, which we interpret as changing Blazhko period between 71.81 and 75.57 days and an additional 1403-day-long cycle analogous to a four-year cycle of the prototype RR Lyr. The limits of the shorter period produce a beating period that is approximately twice as big as a 1403-day period. The newly revealed Blazhko star RZ CVn seems to undergo changes in the amplitude of the modulation, as well as in the basic pulsation and Blazhko periods. We found that the incidence rate of the Blazhko RR Lyraes is at least 31%, more likely even higher. It was also found that the majority of the Blazhko variables show triplet structures in their frequency spectra and that in 89% of these cases, the peak with larger amplitude is on the right-hand side of the main pulsation component.

The SERMON project: 48 new field Blazhko stars and an investigation of modulation-period distribution

“…We also detected 7 candidates and 22 PC stars. When we put together stars from the ASAS-3 survey analysed by Skarka (2014a) with the sample analysed in this study, the detection efficiency of individual approach is about 12% in ASAS data, which is more than two times better than in Szczygieł & Fabrycky (2007) 6 . For the comparison of newly identified BL stars, we collected a sample comprising 1547 stars with known BL periods from literature.…”

“…This paper represents the extension of the study by Skarka (2014a) with fainter stars and stars with more scattered data. To some extend it complements the analysis by Szczygieł & Fabrycky (2007) who performed an automatic search on the full sample of all types of RR Lyrae stars in the ASAS Catalogue of Variable Stars (ACVS).…”

“…The corresponding photometric error of a data point at 13.5 mag is about 0.15 mag (Pojmański 2002). Stars analysed by Skarka (2014a) were ignored. Then we checked for the availability of the data via the online VSX tools.…”

Synergies between exoplanet surveys and variable star research

“…Several of them have received a considerable attention from the particular field (e.g., stellar rotations among Galactic field K−M stars [38] and in the open clusters Come Berenices [26] and in the Hyades and Praesepe [30]). The fields covered by these "side" studies range from rotating asteroids ( [70]) through classical pulsating stars ( [81]) to supernovae ( [80]). It is impossible to summarize all these topics in the depth they deserve.…”

The SuperWASP catalogue of 4963 RR Lyr stars: identification of 983 Blazhko effect candidates

“…Skarka (2013) has produced a web-based compilation of over 400 Blazhko stars, but, as stated on the web site, it does not include objects from densely populated areas such as globular clusters or the Galactic bulge, in much the same way as WASP (see below), nor objects from the OGLE, LINEAR or Catalina surveys mentioned above. However, Skarka has investigated bright RRab objects from the WASP dataset (Skarka 2014) in collaboration with data from ASAS (All Sky Automated Survey; Pojmanski 1997). Jurcsik et al (2009) suggested that the proportion of RRL showing the Blazhko effect approaches 50%, with the review by Kovacs (2016) mentioning how the occurrence rate in groundbased observations do not lag far behind space-based surveys.…”