BVRI Photometry of the CX Cephei System (WR 151)

We have obtained 699 new BVRI observations of the O5 + WN5 eclipsing binary system CX Cephei (WR 151), plus 126 more observations in V only. Our light curves are consistent with previous studies, showing a primary minimum (where the O5 star is eclipsed) of approximately 0.1 mag depth and a much smaller secondary minimum with an approximately 0.03 mag depth. Using the PHOEBE interface to the Wilson-Devinney computer code, we were able to obtain a reasonably satisfactory fit to these data, ignoring any possible contribution from atmospheric eclipse phenomena. The best-fit solution has i = 61.1° and results in masses of 36.8 M_☉ for the O5 star and 26.4 M_☉ for the Wolf-Rayet (WR) star. The binary system is detached. There is an asymmetry in the light curve, suggesting that the “leading side” of the O5 star (or the trailing side of the WR star) is brighter than vice versa. We also observed some features in the light curve that were persistent, but which we could not model.0 - C residuals relative to the PHOEBE fit reveal time variations with a total range of approximately 12% of the flux. Comparing our data with those of Lipunova & Cherpashchuk (1982), we find that the secondary minimum is less prominent today than it was in the 1980s. We were able to revise their period estimate to 2.12691 days

Nova Aquilae 1918 (V603 Aql) Faded by 0.44 mag/century from 1938-2013

We present the light curve of the old nova V603 Aql (Nova Aql 1918) from 1898-1918 and 1934-2013 using 22,721 archival magnitudes. All of our magnitudes are either in, or accurately transformed into, the Johnson $B$ and $V$ magnitude systems. This is vital because offsets in old sequences and the visual-to-$V$ transformation make for errors from 0.1-1.0 magnitude if not corrected. Our V603 Aql light curve is the first time that this has been done for any nova. Our goal was to see the evolution of the mass accretion rate on the century time scale, and to test the long-standing prediction of the Hibernation model that old novae should be fading significantly in the century after their eruption is long over. The 1918 nova eruption was completely finished by 1938 when the nova decline stopped, and when the star had faded to fainter than its pre-nova brightness of $B=11.43 \pm 0.03$ mag. We find that the nova light from 1938-2013 was significantly fading, with this being seen consistently in three independent data sets (the Sonneberg plates in $B$, the AAVSO $V$ light curve, and the non-AAVSO $V$ light curve). We find that V603 Aql is declining in brightness at an average rate of $0.44 \pm 0.04$ mag per century since 1938. This work provides remarkable confirmation of an important prediction of the Hibernation model.Comment: 13 pages, 1 figure, 2 electronic online data tables, Accepted for publication ApJLet