A preliminary timing analysis of two intermediate polars: UU Col and Swift J0939.7-3224

TL;DR

This study analyzes the timing properties of two intermediate polars, UU Col and Swift J0939.7-3224, using TESS photometry, refining their orbital and spin periods and suggesting different accretion mechanisms.

Contribution

It provides the first detailed timing analysis of these two intermediate polars, refining their periods and proposing their accretion modes based on optical data.

Findings

UU Col is a disc-overflow accretor with revised orbital and spin periods.

J0939 likely a pure disc-fed accretor with refined spin and orbital periods.

Absence of beat frequency in J0939 suggests different accretion mode.

Abstract

We present the preliminary timing analysis of confirmed intermediate polar UU Col and possible intermediate polar Swift J0939.7-3224 in the optical band with the help of long-term, high-cadence continuous photometry from Transiting Exoplanet Survey Satellite (TESS). For UU Col, we revise previously reported orbital and spin periods as 3.464 $\pm$ 0.005 h and 863.74 $\pm$ 0.08 s, respectively. Using the second harmonic of the beat frequency, the beat period is estimated as $\sim$928 s. These findings indicate that UU Col is a disc-fed dominated disc-overflow accretor. For J0939, we establish the spin period as 2671.8 $\pm$ 0.8 s and refine the provisionally suggested orbital period as 8.49 $\pm$ 0.03 h. The absence of beat frequency in J0939 signifies that it might be a pure disc-fed accretor; however, an X-ray study of this source will help to understand its true nature.