# Observations of the RRc variable LINEAR 1169665 with the robotic telescope TAROT

## TL;DR

This study analyzes long-term observations of the RRc variable star LINEAR 1169665, revealing a 4.9-year period modulation likely due to a light time effect or a new long-period modulation phenomenon.

## Contribution

It provides the first detailed analysis of period modulation in LINEAR 1169665 using multiple survey data over a decade, suggesting a potential new modulation mechanism.

## Key findings

- Period modulation of 1800.1 days detected
- No significant amplitude variation observed
- Possible explanation involves light time effect or new modulation

## Abstract

LINEAR 1169665 is a RR Lyrae of sub-type c discovered by the asteroid survey LINEAR. The robotic telescope TAROT at Calern Observatory has observed it between the years 2006 and 2015. The present study of TAROT data as well as those from the surveys ASAS-SN (2012-2019) and LINEAR (2002-2008) shows that this star presents a period modulation with a period of 1800.1 days (4.9 years) but with no significant variation of magnitude at maximum. This phenomenon is similar to the one found in KEPLER data for the RRc KIC 2831097 (Sodor et al., 2017) which was suspected to be the result of a light time effect in a double stellar system. The large modulation period and the lack of amplitude modulation exclude it to be attributed to a Blazhko effect. But alternatively to the light time effect this phenomenon might be due to a new modulation phenomenon with long period affecting at least RRc stars.