We report on the physical properties of the disk-like structure of B8 IIIp star 36 Lyncis from line syntheses of phase-resolved , high resolution spectra obtained from the International Ultraviolet Explorer archives and from newly obtained ground-based spectra of the H \alpha absorption profile .
This disk is highly inclined to the rotational axis and betrays its existence every half rotation cycle as one of two opposing sectors pass in front of the star .
Although the disk absorption spectrum is at least ten times too weak to be visible in optical iron lines during these occultations , its properties can be readily examined in a large number of UV “ iron curtain ” lines because of their higher opacities .
The UV Fe II and Fe III lines in particular permit a determination of the disk temperature : 7,500 \pm { 500 } K and a column density of 3 _ { -1.5 } \hskip { -18.0675 pt } { } ^ { +3 } \hskip { 7.227 pt } \times 10 ^ { 20 } cm ^ { -2 } .
The analysis of the variations of the UV resonance lines brings out some interesting details about the radiative properties of the disks : ( 1 ) they are optically thick in the C IV and Si IV doublets , ( 2 ) the range of excitation of the UV resonance lines is larger at the primary occultation ( \phi = 0.00 ) than at the secondary one , and ( 3 ) the relative strengths of the absorption peaks for the two occultations varies substantially from line to line .
We have modeled the absorptions of the UV C IV resonance and H \alpha absorptions by means of a simulated disk with opaque and translucent components .
Our simulations suggest that a gap separates the star and the inner edge of the disk .
The disk extends radially out to \geq 10 R _ { * } .
The disk scale height perpendicular to the plane is \approx 1R _ { * } .
However , the sector causing the primary occultation is about four times thicker than the opposite sector .
The C IV scattering region extends to a larger height than the H \alpha region does , probably because it results from shock heating far from the cooler disk plane .