EX Hydrae

EX Hydrae

EX Hydrae is a southern variable star classified as an eclipsing intermediate polar-type cataclysmic variable(CV). EX Hya is a binary system with an orbital period of 98 minutes, and belongs to a small group of polars with ultra short periods. This variable also has a 67 minute oscillation believed to be the spin period of the white dwarf component.  Outbursts of EX Hya are generally recurring every two years or so with a magnitude range of 13.5 to 9.2. EX Hya is also a source of hard and soft X-rays.

There are over 32,000 observations of EX Hya in the AAVSO International Database dating back to 1954. Outbursts  are relatively quick rising about 2-3 magnitudes, and lasting only a few days. At least 15 outbursts have been detected in the past 50 years.

The long term light curve of EX Hya from the AAVSO data base also highlighting my observations (SRX) from when I first started to observe EX Hya.

In August 1998 I detected an outburst of EX Hya at 9.5. This lead to the first ever satellite observations in X-rays, by the Rossi X-ray Timing Explorer.  A light curve of my observations of EX Hya showing outburst detections up to  September 2012.

Co-Authored paper on EX Hya.

Outbursts of EX Hydrae: mass-transfer events or disc instabilities? 2000MNRAS.313..70H

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