A Radial Velocity Study of the Intermediate Polar EX Hydrae

Abstract

A study on the intermediate polar EX Hya is presented, based on simultaneous photometry and high dispersion spectroscopic observations, during four consecutive nights. The strong photometric modulation related to with the 67-min spin period of the primary star is clearly present, as well as the narrow eclipses associated to the orbital modulation. Since our eclipse timings have been obtained almost 91,000 cycles since the last reported observations, we present new linear ephemeris, although we cannot rule out a sinusoidal variation suggested by previous authors. The system mainly shows double-peaked H$\alpha$, H$\beta$ and HeI $\lambda$5876 Åemission lines. From the profile of the H$\alpha$ line, we find two components; one with a steep rise and velocities not larger than $\sim$1000 km s${}^{-1}$ and another broader component extending up to $\sim$2000 km s${}^{-1}$, which we interpret as coming mainly from the inner disc. A strong and variable hotspot is found and a stream-like structure is seen at times. We show that the best solution correspond to $K_1=58\pm 5$ km s${}^{-1}$ from H$\alpha$, from the two emission components, which are both in phase with the orbital modulation. We remark on a peculiar effect in the radial velocity curve around phase zero, which could be interpreted as a Rositter-MacLaughlin-like effect, which has been taken into account before deriving $K_1$. This value is compatible with the values found in high-resolution both in the ultraviolet and X-ray. We find: $M_1=0.78\pm 0.03$ M${}_{\odot }$, $M_2=0.10\pm 0.02$ M${}_{\odot }$ and $a=0.67\pm 0.01$ R${}_{\odot }$. Doppler Tomography has been applied, to construct six Doppler tomograms for single orbital cycles spanning the four days of observations to support our conclusions. Our results indicate that EX Hya has a well formed disc and that the magnetosphere should extend only to about $3.75R_{\mathrm{WD}}$.

arXiv comment16 pages, 14 figures, accepted for publication in MNRAS

References in corpus (14)

• The Donor Stars of Cataclysmic Variables
• An Exploration of the Paradigm for the 2-3 Hour Period Gap in Cataclysmic Variables
• Brown Dwarfs and the Cataclysmic Variable Period Minimum
• The Spin Period of EX Hydrae
• A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate
• High-resolution spectroscopy of the intermediate polar EX Hydrae. I. Kinematic study and Roche tomography
• HST/STIS Spectroscopy of the Intermediate Polar EX Hydrae
• Exploring inside-out Doppler tomography: non-magnetic cataclysmic variables
• A spectroscopic search for faint secondaries in cataclysmic variables
• The Radial Velocity and Mass of the White Dwarf of EX Hydrae Measured with Chandra
• ORFEUS II and IUE Spectroscopy of EX Hydrae
• Spectroscopic Observations of the Intermediate Polar EX Hydrae in Quiescence
• Testing the cooling flow model in the intermediate polar EX Hydrae
• The Magnetospheric Boundary in Cataclysmic Variables

Cited by in corpus (9)

• The evolutionary status of Cataclysmic Variables: Eclipse modelling of 15 systems
• Hard X-ray view on intermediate polars in the Gaia era
• A Catalogue of Potential Post Common Envelope Binaries
• Hard X-ray Cataclysmic Variables
• Nova-produced Common Envelope: Source of the Non-solar Abundances and an Additional Frictional Angular Momentum Loss in Cataclysmic Variables
• Constraining the accretion geometry of the intermediate polar EX Hya using NuSTAR, Swift and Chandra observations
• X-ray spectroscopy method of white dwarf mass determination in intermediate polars. External systematic uncertainties
• New radial velocity observations of AH Her: evidence for material outside the tidal radius
• Current and secular accretion rates of EX Hydrae