BF Eridani: a cataclysmic variable with a massive white dwarf and an evolved secondary
V. V. Neustroev, S. Zharikov
备注：
15 pages, 11 figures (36 eps files) and 5 tables. Accepted for publication in MNRAS. The paper with high resolution colour images can be downloaded from http://urania.it.nuigalway.ie/papers/bf_eri.pdf
We present high- and medium-resolution spectroscopic observations of the cataclysmic variable BF Eri during its low and bright states. The orbital period of this system was found to be 0.270881(3) days. The secondary star is clearly visible in the spectra through absorption lines of the neutral metals MgI, FeI and CaI. Its spectral type was found to be K3+-0.5. A radial velocity study of the secondary yielded a semi-amplitude of K_2=182.5+-0.9 km/s. The radial velocity semiamplitude of the white dwarf was found to be K_1=74+-3 km/s from the motion of the wings of the Halpha and Hbeta emission lines. From these parameters we have obtained that the secondary in BF Eri is an evolved star with a mass of 0.50-0.59 Msun, whose size is about 30 per cent larger than a zero-age main-sequence single-star of the same mass. We also show that BF Eri contains a massive white dwarf (M1>1.23 Msun), allowing us to consider the system as a SN Ia progenitor. BF Eri also shows a high gamma-velocity (gamma=-94 km/s) and substantial proper motion. With our estimation of the distance to the system (d~700+-200 pc), this corresponds to a space velocity of ~350 km/s with respect to the dynamical local standard of rest. The cumulative effect of repeated nova eruptions with asymmetric envelope ejection might explain the high space velocity of the system. We analyze the outburst behaviour of BF Eri and question the current classification of the system as a dwarf nova. We propose that BF Eri might be an old nova exhibiting "stunted" outbursts.
Low-state spectrophotometry of the short-period polar EF Eridani (Porb=81 min) found the system at V=18.0 with no trace of the companion (Wheatley and Ramsay 1998). We show that the lack of such spectral features implies that the companion to the white dwarf in EF Eri has a spectral type later than M9 and is either a transition object at the brink of hydrogen burning or a brown dwarf. The optical low state spectrum indicates a temperature of the white dwarf of Teff=9500+-500K. This is one of the coldest white dwarfs in cataclysmic variables, implying a cooling age t_cool>=10e9 yrs or accretion…
Infrared spectroscopic observations of LL Andromedae and EF Eridani are presented. Our K band spectrum of LL Andromedae reveals the presence of methane absorption in the secondary star indicating an effective temperature less than 1300K, similar to a "T" type methane brown dwarf. The secondary star in EF Eridani is seen to be warmer with an effective temperature of ~1650K and a spectroscopic classification consistent with an L4-5 star. Both secondaries have theoretical mass estimates of 0.04-0.055 solar masses (40-55 Jupiter masses). Our IR spectroscopic observations of LL And and EF Eri provi…
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We model the infrared (IR) emission from the ring-like dust disk around the main-sequence (MS) star Epsilon Eridani, a young analog to our solar system, in terms of a porous dust model previously developed for the extended wedge-shaped disk around the MS star $β$ Pictoris and the sharply truncated ring-like disks around the Herbig Ae/Be stars HR 4796A and HD 141569A. It is shown that the porous dust model with a porosity of $\simali$90% is also successful in reproducing the IR to submillimeter dust emission spectral energy distribution as well as the 850$\mum$ flux radial profile of the dust r…
Chemical compositions are derived from high-resolution spectra for three stars classed as SRd variables in the General Catalogue of Variable Stars. These stars are shown to be metal-poor supergiants: WY And with [Fe/H] = -1.0, VW Eri with [Fe/H] = -1.8, and UW Lib with [Fe/H] = -1.2. Their compositions are identical to within the measurement errors with the compositions of subdwarfs, subgiants, and less evolved giants of the same FeH. The stars are at the tip of the first giant branch or in the early stages of evolution along the asymptotic giant branch (AGB). There is no convincing evidence t…
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EF Eri is a magnetic cataclysmic variable that has been in a low accretion state for the past nine years. Low state optical spectra reveal the underlying Zeeman-split white dwarf absorption lines. These features are used to determine a value of 13-14 MG as the white dwarf field strength. Recently, 5-7 years into the low state, Balmer and other emission lines have appeared in the optical. An analysis of the H$α$ emission line yields the first radial velocity solution for EF Eri, leading to a spectroscopic ephemeris for the binary and, using the best available white dwarf mass of 0.6M${\odot}$, …
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