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

Abstract

We investigated 1234 fundamental mode RR Lyrae stars observed by the All Sky Automated Survey (ASAS) to identify the Blazhko (BL) effect. A sample of 1547 BL stars from the literature was collected to compare the modulation-period distribution with stars newly identified in our sample. A classical frequency spectra analysis was performed using Period04 software. Data points from each star from the ASAS database were analysed individually to avoid confusion with artificial peaks and aliases. Statistical methods were used in the investigation of the modulation-period distribution. Altogether we identified 87 BL stars (48 new detections), 7 candidate stars, and 22 stars showing long-term period variations. The distribution of modulation periods of newly identified BL stars corresponds well to the distribution of modulation periods of stars located in the Galactic field, Galactic bulge, Large Magellanic Cloud, and globular cluster M5 collected from the literature. As a very important by-product of this comparison, we found that pulsation periods of BL stars follow Gaussian distribution with the mean period of $0.54\pm 0.07$ d, while the modulation periods show log-normal distribution with centre at $\log (P_{\mathrm{m}}[\mathrm{d}])=1.78\pm 0.30$ dex. This means that 99.7 % of all known modulated stars have BL periods between 7.6 and 478 days. We discuss the identification of long modulation periods and show, that a significant percentage of stars showing long-term period variations could be classified as BL stars.

13 pages, 9 figures, Accepted for publication in Astronomy & Astrophysics

References in corpus (13)

• Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
• Long time-scale behavior of the Blazhko effect from rectified Kepler data
• Multiperiodic Galactic field RR Lyrae stars in the ASAS catalog
• Revisiting CoRoT RR Lyrae stars: detection of period doubling and temporal variation of additional frequencies
• New RR Lyrae variables in binary systems
• A Catalogue of RR Lyrae Stars from the Northern Sky Variability Survey
• The historical vanishing of the Blazhko effect of RR Lyr from GEOS and Kepler surveys
• On the modulation of RR Lyrae stars in the globular cluster M3
• Known Galactic field Blazhko stars
• The Blazhko behaviour of RR Geminorum II -- long-term photometric results
• On the incidence rate of first overtone Blazhko stars in the Large Magellanic Cloud
• Characteristics of bright ab-type RR Lyrae stars from the ASAS and WASP surveys
• Nonlinear dynamical analysis of the Blazhko effect with the Kepler space telescope: the case of V783 Cyg

Cited by in corpus (4)

• Blazhko effect in the Galactic bulge fundamental mode RR~Lyrae stars I: Incidence rate and differences between modulated and non-modulated stars
• Blazhko effect in the Galactic bulge fundamental mode RR Lyrae stars II: Modulation shapes, amplitudes and periods
• A Study of Pulsation properties of 57 Non-Blazhko effect ab-type RR Lyrae stars with homogeneous metallicities from the LAMOST-Kepler/K2 survey
• Digging Deeper for RR Lyrae Stars with Low Modulation Amplitudes