Amplitude spectrum of V458 Vul. The confidence levels of peaks in the
spectrum are shown by horizontal lines and per cents on the right
edge of the Figure.
Fig. 2. The light curve of V458 Vul folded with the
period of 0.58946 day (top). The light-decay trend is eliminated
to reduce data to plateau level. The light curve of a check star
folded with the same period to demonstrate the accuracy of
observations (middle). The averaged orbital light curve of V458 Vul
We analysed spectra of V458 Vul taken with SAO RAS 1-m reflector on 2007 August 18.90 and October 18.68 UT (spectral range 3800-7530A, resolution 8A). The date of the last spectrum coincides with the date of the first X-ray detection by Swift. Our spectra confirm the description of spectral evolution by T.N.Tarasova (IBVS #5807): the features of FeII class nova were completely changed by ones of He/N nova in the SSS phase. No signs of high excitation Fe ion emission are seen in spectrum taken on October 18. HeII 4686A emission is blended with CIII/NIII and HeI lines, but its intensity is less than a half of Hbeta what gives the upper limit of the central source temperature of 190000K. [Fe X] 6374A emission is very faint, its detection is marginal.
Fig. 3. The light curve of V458 Vul drawn versus time. Horizontal line marks plateu, SSS - marks the first and the last detection of X-ray SuperSoft Source, digits 1-4 show the local maxima used to correct the orbital period.
Fig. 4. The spectra of V458 Vul taken on 2007 August 18 and
October 18. The line identifications are given.
Dr. Albert Zijlstra (JBCA, Univ. of Manchester) reported about new time-resolved optical spectroscopic observations of V458 Vul which reveal radial velocity variations in the He II 5412 and 4686 A emission lines with the period 0.06812255 (0.00000017) day (Rodriguez-Gil et al. ArXiv:1006.1075). It is identified with the orbital period of the binary system. T(0) = 2454652.52694 (8 x 10^-5). Period 0.58946 day and its aliases determined by Goranskij et al. (ATel 1631) do not become apparent. V458 Vul is therefore the planetary nebula central binary star with the shortest period known. We try to identify this period in our photometric observations. We have two sets of extensive monitoring in the V band: JD 2454644 - 2454655 (612 obs.) and JD 2455060 - 2455073 (415 obs.). These data were cleaned for slow trends and low frequency noise. Period 0.06812255 day appears in the first set with the amplitude 0.03 mag and roughly sinusoidal light curve, and in the second set with the amplitude of 0.05 mag with a small eclipse-like dip near the phase of T(0). The averaged light curves are shown in the following Figure.
Figure. Mean light curves of V458 Vul calculated with the
period of 0.06812255 day.
J.J.Drake, K.Page, J.Osborne, M.Bode, R.Corradi, P.Rodriguez-Gil,
J.Drew, P.Gaensicke, D.Steeghs, C.Knigge, J.Sokoloski,
J.J.Drake, K.Page, J.Osborne, A.Beardmore, J.-U.Ness, S.Starrfield, G.Schwarz, M.Tsujimoto, M.Barlow, R.Wesson, M.Bode, R.Corradi, P.Rodriguez-Gil, P.Gaensicke, D.Steeghs, C.Knigge, D.Takai, A.Zijlstra, ATel 1603, 2007.
T.N.Tarasova, IBVS No.5807, 2007.
View UBVRc light curves of V458 Vul. Java compatible brouser is needed. Use mouse mouseDrag function to examine the details.
Download photometric data collection (in ASCII codes; JD hel., V,B,U,R in the columns of the table).