A Hubble Space Telescope survey for novae in M87 – III. Are novae good standard candles 15 d after maximum brightness?

Ten weeks of daily imaging of the giant elliptical galaxy M87 with the Hubble Space Telescope (HST) has yielded 41 nova light curves of unprecedented quality for extragalactic cataclysmic variables. We have recently used these light curves to demonstrate that the observational scatter in the so-called maximum-magnitude rate of decline (MMRD) relation for classical novae is so large as to render the nova-MMRD useless as a standard candle. Here, we demonstrate that a modified Buscombe–de Vaucouleurs hypothesis, namely that novae with decline times t_2 > 10 d converge to nearly the same absolute magnitude about two weeks after maximum light in a giant elliptical galaxy, is supported by our M87 nova data. For 13 novae with daily sampled light curves, well determined times of maximum light in both the F606W and F814W filters, and decline times t_2 > 10 d we find that M87 novae display M_(606W,15) = −6.37 ± 0.46 and M_(814W,15) = −6.11 ± 0.43. If very fast novae with decline times t_2 < 10 d are excluded, the distances to novae in elliptical galaxies with stellar binary populations similar to those of M87 should be determinable with 1σ accuracies of ± 20 per cent with the above calibrations

A Hubble Space Telescope survey for novae in M87 – III. Are novae good standard candles 15 d after maximum brightness?

Ten weeks of daily imaging of the giant elliptical galaxy M87 with the Hubble Space Telescope (HST) has yielded 41 nova light curves of unprecedented quality for extragalactic cataclysmic variables. We have recently used these light curves to demonstrate that the observational scatter in the so-called maximum-magnitude rate of decline (MMRD) relation for classical novae is so large as to render the nova-MMRD useless as a standard candle. Here, we demonstrate that a modified Buscombe–de Vaucouleurs hypothesis, namely that novae with decline times t_2 > 10 d converge to nearly the same absolute magnitude about two weeks after maximum light in a giant elliptical galaxy, is supported by our M87 nova data. For 13 novae with daily sampled light curves, well determined times of maximum light in both the F606W and F814W filters, and decline times t_2 > 10 d we find that M87 novae display M_(606W,15) = −6.37 ± 0.46 and M_(814W,15) = −6.11 ± 0.43. If very fast novae with decline times t_2 < 10 d are excluded, the distances to novae in elliptical galaxies with stellar binary populations similar to those of M87 should be determinable with 1σ accuracies of ± 20 per cent with the above calibrations

Potential for protein deposition and threonine requirement of modern genotype barrows fed graded levels of protein with threonine as the limiting amino acid

The study was conducted to estimate the actual genetic potential for daily protein deposition of growing barrows [genotype: Pietrain x (Duroc x Landrace)]. Twenty-four pigs with an average initial body weight (BW) of 43.7 +/- 0.7 kg were used in a N-balance study. Semi-purified diets with graded levels of crude protein (45.8, 94.2, 148.0, 198.9, 255.5 and 300.2 g/kg DM) were used, based on a constant mixture of wheat, soya bean protein concentrate and potato protein concentrate as protein sources. The amino acid pattern of the diets was according to the ideal amino acid ratio for growing pigs (Wang and Fuller, 1989), with the exception of threonine (adjusted as limiting amino acid). N-balance data were used to estimate daily N-maintenance requirement (NMR = 446 mg N/BWkg0.67/day) by regression method and the theoretical maximum of daily N-retention (PDmaxT = 3115 mg N/BWkg0.67/day) based on N-utilization model of Gebhardt (1966) using program Mathematica 3.0. The results indicate that PDmaxT of pigs under study is much higher than results from earlier studies with older genotypes. In summary, pigs of modern genotype have a very high genetic potential for daily protein deposition and these actual data are important basic informations for estimation of amino acid requirement within the model used. Threonine requirement data depending on threonine efficieny and protein deposition (8.96, 10.45 and 12.22 g/day for 130, 145 and 160 g daily protein deposition; 50 kg body weight) are discussed