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There are terrestrial signatures of the solar activity cycle in ice core data (Ram & Stoltz 1999), but the variations in the sun's irradiance over the cycle seem too small to account for the signature (Lean 1997; Goode & Dziembowski 2003). Thus, one would expect that the signature must arise from an indirect effect(s) of solar activity. Such an

We present long-slit observations in the red and near infrared of 12 HII galaxies made with the Isaac Newton Telescope at the Roque de los Muchachos Observatory in 1999 February and 2000 January. The spectral range includes the sulphur lines [SII] at 6717, 6731 Å and [SIII] at 9069, 9532 Å. For all the observed galaxies, ion-weighted temperatures

These are the preliminary results of our BVR photometric study. The quasar 1628.5+3808 is shown here only for the sake of illustration of our research. This object showed variations in the three bands. It was observed with a 1.5-meter telecope from the Observatorio Astronómico Nacional at San Pedro Mártir, México. Only non-variable field stars were

The Owl Nebula is a triple-shell planetary nebula with the outermost shell being a faint bow-shaped halo. We have obtained deep narrowband images and high-dispersion echelle spectra in the Hα, [O III], and [N II] emission lines to determine the physical structure of each shell in the nebula. These spatiokinematic data allow us to rule out

We revise the physical conditions in the O++ zone of the planetary nebula NGC 6543, obtaining two different estimates of the electron temperature (Te) and one estimate of the electron density (Ne). The electron temperature is computed by means of two independent methods, the nebular-to-auroral ratio [O III] λ5007/λ4363 and the diagnostic diagram