Cyclic variations with twice the accretion disk precession period in the old nova V603 Aquilae

TL;DR

This study analyzes long-term light curves of V603 Aql, revealing a known 3.5-hour modulation and discovering a new 5.85-day variation, likely linked to accretion disk precession, with the origin of the latter remaining uncertain.

Contribution

First detection of brightness variations with a period twice the accretion disk precession period in V603 Aql, expanding understanding of its accretion dynamics.

Findings

Confirmed the 3.5-hour superhump period.

Detected a 5.85-day brightness variation.

Linked the 5.85-day period to twice the disk precession period.

Abstract

A dense series of long and high time resolution light curves of the old nova V603 Aql, covering 22 nights (19 of which are consecutive), are analyzed in order to identify and characterize variations on the time scale of hours and days. The well known 3.5 hour modulation, observed many times in the past and considered to be due to a long lasting, albeit not entirely stable superhump, is recovered at a period of 0.1453 days and an amplitude of 0.062 mag. Most interesting, however, is the detection of highly significant brightness variations with an amplitude of 0.050 mag and a period of 5.85 days which is to a very high precision equal to twice the beat period between the orbital and the superhump period. The latter is generally interpreted as the precession period of an eccentric accretion disk. The origin of these long term variations remains unknown.