Optical Night-Sky Brightness at Mauna Kea over the Course of a Complete Sunspot Cycle

We have produced a data base of V-band and B-band night-sky brightness measurements rather evenly spread out over the course of a whole sunspot cycle from September 1985 to August 1996. Almost all the data were obtained at the 2800-m level of Mauna Kea using the same telescope, same photomultiplier tube, filters, and diaphragm, thus minimizing various sources of systematic error and allowing an estimate of the sources of random error. The yearly V-band averages of observed sky brightness ranged from 21.287 to 21.906 magnitudes per square arc second. The color of the sky is $B-V$ = 0.930 and does not change discernibly over the course of the sunspot cycle. After correcting the V-band data to the zenith, we find that the airglow component varied a factor of 4.5 over the course of the solar cycle. Once the 11-year solar cycle effect is removed from the data, the most significant contribution to the scatter of individual data points appears to be the short term variations on time scales of tens of minutes like those observed by the Whole Earth Telescope project.Comment: 27 pages AAS-style (v 4.0) Latex, 5 figures, to be published in Publications of the Astronomical Society of the Pacifi

Near-infrared light curves of type Ia supernovae

Aims. With our time-dependent model atmosphere code PHOENIX, our goal is to simulate light curves and spectra of hydrodynamical models of all types of supernovae. In this work, we simulate near-infrared light curves of SNe Ia and confirm the cause of the secondary maximum. Methods. We apply a simple energy solver to compute the evolution of an SN Ia envelope during the free expansion phase. Included in the solver are energy changes due to expansion, the energy deposition of {\gamma}-rays and interaction of radiation with the material. Results. We computed theoretical light curves of several SN Ia hydrodynamical models in the I, J, H, and K bands and compared them to the observed SN Ia light curves of SN 1999ee and SN 2002bo. By changing a line scattering parameter in time, we obtained quite reasonable fits to the observed near-infrared light curves. This is a strong hint that detailed NLTE effects in IR lines have to be modeled, which will be a future focus of our work. Conclusions. We found that IR line scattering is very important for the near-infrared SN Ia light curve modeling. In addition, the recombination of Fe III to Fe II and of Co III to Co II is responsible for the secondary maximum in the near-infrared bands. For future work the consideration of NLTE for all lines (including the IR subordinate lines) will be crucial.Comment: 5 pages, 12 figures, A&A in pres