CCD and DSLR maxima of RR Lyrae stars in 2016 and 2017

TL;DR

This paper reports on the maximum brightness timings of RR Lyrae stars observed in 2016 and 2017, contributing to the GEOS RR Lyr survey's data collection efforts.

Contribution

It provides new maximum timing data for RR Lyrae stars from 2016-2017, enhancing the observational dataset for this variable star class.

Findings

Maximum timings of RR Lyrae stars were successfully recorded.

Data contributes to ongoing RR Lyrae variability studies.

Observations support the GEOS RR Lyr survey objectives.

Abstract

We present here maximum timings of RR Lyrae stars observed in 2016 and 2017 by VSOLJ member Kenji Hirosawa. The calculation of the time of maximum from the measurements provided by the observer have been made in the frame of the GEOS RR Lyr survey.

Full text

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CCD and DSLR maxima of RR Lyrae stars in 2016 and 2017

*Joint publication: VOSJ Variable Star Bulletin No.65

Kenji Hirosawa1 and J.F. Le Borgne2

1 Variable Star Observer League in Japan,

2 Groupe Européen d’Observations Stellaires

We present here maximum timings of RR Lyrae stars observed in 2016 and 2017 by VSOLJ member Kenji Hirosawa. The calculation of the time of maximum from the measurements provided by the observer have been made in the frame of the GEOS RR Lyr survey. GEOS (European group for stellar observation, http://geos.upv.es/) is an association of amateur and professional astronomers, created in 1974, the aim of which is the promotion of research in astrophysics by amateur astronomers. A natural domain of research of the group is the study of variable stars. In this context, it appeared that the observation of the stars of RR Lyrae type is relatively neglected, in particular on long time scales. This is why GEOS decided about one decade ago to start a ”RR Lyr Survey” (GRRS). It includes 3 main parts:

• A routine survey of bright RR Lyr stars, aiming in measuring times of maximum of RRab stars brighter than magnitude about 13 in order to monitor the variation of period on decade time scale. The time sampling is of the order of 10 maximums per year for each star. The observations are mainly done by professional robotic telescopes (25 cm TAROT telescopes, Klotz et al., (2009)), but also by amateur astronomers performing telescopes of 10 to 25cm diameter equipped with CCD or DSLR cameras (Le Borgne et al.,, 2007).

• Prospecting survey of under-studied RR Lyraes of magnitudes 13 to 15 using telescopes of 20 to 60 cm equipped with CCD cameras. For this part the aim is to check variation type, period and possible Blazhko effect.

• The follow-up of the RR Lyr it self in order to monitor the evolution of its Blazhko effect. Preston et al. (Preston et al,, 1965) have shown that in years 1960’s the Blazhko effect of RR Lyr have stopped and restarted again afterwards. This phenomenon was not studied in details because it requests continuous monitoring of the star. GRRS observers use dedicated small instruments (5cm photographic lens with CCD or DSLR) to follow RR Lyr since 2008. The time sampling of times of maximum measurements have allow to observe the disappearance of RR Lyr Blazhko effect in 2014 (Le Borgne et al.,, 2014) (Poretti et al.,, 2018). It restarted afterwards but with very small amplitude, and in 2018, the amplitude of the Blazhko effect is not still at the value it had at the beginning of the survey.

GRRS contributes to the ”GEOS RR Lyr database” (http://rr-lyr.irap.omp.eu/dbrr/)

The O-C are computed using the elements from the General Catalogue of Variable Stars (Samus et al.,, 2017) by default. For the stars which have no elements in GCVS, the following table give the list of elements used.

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The following tables contain the list of maximums observed by Kenji Hirosawa in 2016 and 2017.

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