COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1579 Konkoly Observatory Budapest 1979 April 2 THE IUE ULTRAVIOLET SPECTRUM OF V1073 CYGNI V1073 Cyg (HD204038, BD+33d4252) is a contact binary with an Am-type star as the bright member although Hill, et al. (1975) give an early F-classification, perhaps as a result of the dispersion of their spectra. FitzGerald (1964) has solved the double line velocity variation using several measurements of the weak, diffuse lines of the secondary star. Popper (1970), however, noted that the visible-band lines for each component are of a quality too poor to yield reliable masses. Kondo (1966) and Bendenelli, et al. (1967) analyzed the partially- eclipsing light curve and Kruseman (1968) noted that his light curves agree with Kondo's solution. A newer synthesis of Kondo's light curve has been presented by Leung and Schneider (1977), who then also represented FitzGerald's velocities on the basis of a circular orbit. It is possible to compare the Stromgren indices by Hilditch and Hill (1975) to the calibration by Crawford and Mandwewala (1976). The metallicity of V1073 Cyg is evident from this comparison but it is also clear that the reddening cannot be derived from the heavily blanketed (u-b) and c1 parameters. An upper limit to E(b-y) is of the order of 0.06 leading to an upper limit, E(B-V) = 0.08. Because the period is short, numerous timings of minimum light have been observed and largely collated by Strohmeier, et al. (1962), Kondo, and Strohmeier and Bauernfeind (1968). A few additional timings have become available in the last decade. These eighty years of history make it clear that the eclipses occur at half-period intervals and that the period has varied, but the scatter and character of the residuals from a constant-period ephemeris can be explained either by a secular change at a variable rate or by one discontinuous period increase about JD2427600. For purposes of this note, phases have been calculated from: Hel. Pr. Min. = 2438672.5826 + 0.7858592E. Program PG2SS, originally defined by S. Sobieski, permitted observation of V1073 Cyg with the IUE satellite. The description of the instrumentation package is given at length in the October 5, 1978 issue of Nature. The journal of our three observations taken in the low- dispersion mode appears in Table I which lists in successive columns Table I Low Dispersion Spectra of V1073 Cyg ------------------------------------------------------------------- Image Hel.J.D. Phase Exposure Aperture Remarks ------------------------------------------------------------------- LWR2047 2443732.031 0.098 23 min. Large Saturated from lambda2495 to lambda3035 LWR2047 2443732.051 0.136 19 Small Underexposed shortward of lambda2400 LWR2058 2443733.059 0.419 14 Large ------------------------------------------------------------------- the image number, the mean heliocentric Julian Day Number an phase of the observation, the exposure length and the choice of the large (10" x 20" ellipse) or small (3" circle) aperture for the spectrograph. Neither interstellar absorption nor stellar emission lines were detected. Each spectrum shows absorption features which are very broad, in part because of the low resolution (~= 6A) of the spectra and in part because of the very large number of unresolved, low excitation lines. Because of the unresolved richness of the spectrum, we content ourselves with describing the evidence for 8 common atoms and ions. Fe I: The strongest evidence is a possible contribution from multiplet 1 to an absorption feature at lambda2970. Possibly present. Fe II: Almost every strong transition falls within a conspicuous absorption feature. The only discrepancy occurs near lambda2240 where several intense lines should fall, but only a weak absorption is seen. Definitely present. Cr II: Blends of lines from multiplets 5,6, and 11 fall within absorptions of moderate strength near lambdalambda2860,2750, and 2870, respectively. Definitely present. Mg I: The strongest line is expected to occur at lambda2852 and a weak absorption is seen at about that wavelength. Possibly present. Mg II: The resonance doublet at lambdalambda2795,2802 is conspicuously in absorption. Members of multiplet 2 fall within a moderate absorption feature near lambda2930. Definitely present. Mn II: Three strong lines of multiplet 1 fall within a conspicuous absorption near lambda2600. Possibly present. Ti I: The strongest transitions of multiplet 1 fall near an absorption feature at lambda2950. It is possible that multiplet 3 contributes to an absorption feature at lambda2645. Possibly present. Si I: Multiplet 1 may contribute to a strong absorption feature near lambda2525. Possibly present. A smooth free-hand continuum was drawn from LWR2058, corrected for the cathode sensitivity by the calibration in IUE Newsletter No. 2, and dereddened for E(B-V) = 0.08 by the interstellar extinction curve due to Jamar, et al. (1976). This was compared to sample model atmospheres in the range from 8750K through 6000K - thus bracketing the spectral classifications - drawn from the compilation by Carbon and Gingerich (1969). It proved impossible to reproduce the spectral gradient of the observations by any of these atmospheres, a circumstance due, no doubt, to the severe blanketing. Obviously, better spectra would be desirable. With the IUE, a suitable high resolution exposure with the small aperture would, however, be longer than the binary period. We are indebted to the Telescope Operators and Resident Astronomers of the IUE team for their assistance and advice. This research was supported by NASA grant NSG-5296, which is gratefully acknowledged. ROBERT KOCH M. JAVAD SIAH MICHAEL N. FANELLI Department of Astronomy University of Pennsylvania Philadelphia 19104 U.S.A. References: Bendenelli, O., Delli Ponti, C., Catalano, S., and Cristaldi, S. 1967, Mem. Soc. Astr. Ital. 38, 763. [BIBCODE 1967MmSAI..38..763B ] Carbon, D.F., and Gingerich, O. 1969 in Proc. Third Harvard-Smithsonian Conference on Stellar Atmospheres, O. Gingerich, ed (Cambridge: M.I.T. Press), p. 377. [BIBCODE 1969tons.conf..377C ] Crawford, D.L., and Mandwewala, R. 1976, Pub. A. S. P. 88, 917. [BIBCODE 1976PASP...88..917C ] FitzGerald, P. 1964, Pub. D. D. O. 2, 417. [BIBCODE 1964PDDO....2..417F ] Hilditch, R.W., and Hill, G. 1975, Mem. R. A. S. 79, 101. [BIBCODE 1975MmRAS..79..101H ] Hill, G., Hilditch, R.W., Younger, F., and Fisher, W.A. 1975, Mem. R. A. S. 79, 131. [BIBCODE 1975MmRAS..79..131H ] Jamar, C., Macau-Hercot, D., Monfils, A., Thompson, G.I. Houziaux, L., and Wilson, R. 1976, Ultraviolet Bright Star Spectrophotometric Catalogue. [BIBCODE 1976ubss.book.....J ] Kondo, Y. 1966, A. J. 71, 54. [BIBCODE 1966AJ.....71...54K ] Kruseman, P. 1968, B. A. N. Supp. 2, 377. [BIBCODE 1968BANS....2..377K ] Leung, K.C., and Schneider, J.J. 1978, Ap. J. 222, 917. [BIBCODE 1978ApJ...222..917L ] Popper, D.M. 1970, Bull. A. A. S. 2, 12. Strohmeier, W. and Bauernfeind, H. 1968, Veroff. Remeis Sternw. Bamberg 7 (72). [BIBCODE 1968BamVe...7...72S ] Strohmeier, W., Knigge, R. and Ott, H. 1962, Veroff. Remeis Sternw. Bamberg 5 (13).