Multi-site observations of Delta Scuti stars 7 Aql and 8 Aql (a new Delta Scuti variable): The twelfth STEPHI campaign in 2003

TL;DR

This study analyzes the pulsation behavior of two Delta Scuti stars, including a newly identified variable, using multi-site, high-precision photometry to detect multiple oscillation frequencies and compare them with theoretical models.

Contribution

First detection of multiple pulsation frequencies in 7 Aql and 8 Aql, including a new variable star, with detailed comparison to theoretical pulsation models.

Findings

Detected 6 frequencies in 7 Aql and 3 in 8 Aql above 99% confidence.

Observed frequencies suggest low radial order p modes and presence of non-radial oscillations.

Range of excited modes aligns with non-adiabatic theoretical predictions.

Abstract

We present an analysis of the pulsation behaviour of the Delta Scuti stars 7 Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the framework of STEPHI XII campaign during 2003 June--July. 183 hours of high precision photometry were acquired by using four-channel photometers at three sites on three continents during 21 days. The light curves and amplitude spectra were obtained following a classical scheme of multi-channel photometry. Observations in different filters were also obtained and analyzed. Six and three frequencies have been unambiguously detected above a 99% confidence level in the range 0.090 mHz--0.300 mHz and 0.100 mHz-- 0.145 mHz in 7 Aql and 8 Aql respectively. A comparison of observed and theoretical frequencies shows that 7 Aql and 8 Aql may oscillate with p modes of low radial orders, typical among Delta Scuti stars. In terms of radial oscillations the range of 8 Aql goes from n=1 to n=3 while for 7 Aql the range spans from n=4 to n=7. Non-radial oscillations have to be present in both stars as well. The expected range of excited modes according to a non adiabatic analysis goes from n=1 to n=6 in both stars.