The first FUSE spectrum of the Nova-like (VY) MV Lyr was taken during a low state. The spectrum reveals the accreting WD, which is heated due to continuous accretion, which is typical of NL VY systems. There is no discernable extinction toward MV Lyr. The spectrum consists of four exposures (FUSE orbits). The WD model (solid white line) has a mass of 0.73 Msun, a temperature of 45,000K, a rotational velocity of 200 km/s and solar composition. To fit the flux below 930A one has to decrease the temperature to 44,000K. The slight decrease of flux (between 915 and 930A) is possibly due to the sharp H i absorption lines. In order to fit the right wing of the Lyman beta profile one has to increase the temperature to 47,000K. The right wing might be affected by some O vi emission. All the sharp emission lines (H i, C iii, and more) are most probably from air glow. We identify the following absorption lines which fit the WD photosphere model: S iv (1006), C ii (1010), S iv (1063, 1073), Si iv (1066), He ii (992, 1085), Si iii (1110), P v (1118), Si iv (1123, 1128) and C iii (1175). All the other lines are either not identified or are sharp ISM absorption lines (e.g. Si ii, C ii, Ar i, Fe ii). For solar composition, the WD has to have a rotation rate of at least 200 km/s and possibly as much as 250 km/s in order to match the profile of the absorption lines. If one decreases the abundances, the rotational velocity needed to match the absorption lines decreases as well. For Z=0.2 the (projected) rotational velocity needed to match the lines is 150 km/s. For an inclination of 12deg, a projected rotational velocity of 200 km/s corresponds to about 1/3 of the Keplerian velocity at one stellar radius. For a velocity of 150 km/s, it corresponds to about 1/4-1/5 of the Keplerian velocity. In the second (lower) figure we present the FUSE spectrum of MV Lyr obtained during a high-state. The spectrum is mainly from the disk. Standard disk models fail to fit the spectrum properly, and lead to a large mass accretion rate with a distance that do not fit 500pc. In order to remediate to this, we model the boundary layer by replacing the inner two rings of the disk with boundary layer rings of temperature 100,000K. In that model the WD is also included. The fitting results are: A WD with T=50,000K (the results do not depend strongly on the WD temperature), i=10deg, mass accretion rate=2.E-9 solar mass per year. The WD contributes only to 9 percent of the flux and the disk+BL contribute the remaining 91 percent.

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FUSE Data

Synthetic Spectrum

Click to see larger version of the plot

These data and models were published in the paper:

Godon, P., Sion, E.M. 2011, PASP, 123, 903; Godon, P., Sion, E.M., Levay, K., Linnell, A.P., Szkody, P., Barrett, P.E., Hubeny, I., Blair, W.P. 2012, ApJS, in press; Barrett, P.E. et al., 2011, in preparation

FUSE Data

Synthetic Spectrum

Click to see larger version of the plot

These data and models were published in the paper:

Godon, P., Sion, E.M. 2011, PASP, 123, 903; Godon, P., Sion, E.M., Levay, K., Linnell, A.P., Szkody, P., Barrett, P.E., Hubeny, I., Blair, W.P. 2012, ApJS, in press; Barrett, P.E. et al., 2011, in preparation

Notes on figures:

When a model is shown, the portions of the observed spectrum that have been masked before the spectral fit are in blue, while the rest of the observed spectrum is in red. The model fit is shown the solide line in black (or possibly white). If the model is a composite made of a disk model and a white dwarf model, then these are shown with the dashed- and dotted lines (respectively). Some models include the effect of quasi-molecular HI absorption features, these are labelled "Q-mol" in the spectrum.