We present a review on the determination of the primordial helium abundance, Y_p, based on the study of hydrogen and helium recombination lines in extragalactic H II regions. We also discuss the observational determinations of the increase of helium to the increase of oxygen by mass Δ Y/Δ O , and compare them with predictions based on models of

We present the project Local Cosmology from Isolated Dwarfs (LCID), aimed at deriving detailed star-formation histories for a sample of Local Group isolated dwarf galaxies. To accomplish this goal we have collected, using the ACS on board the HST, color-magnitude diagrams reaching the oldest main sequence turnoff (V ≃ 29) with good photometric

Available from the Minor Planet Center.

Aims:The aim of this paper is to analyze the thermal properties, oscillatory, and flow motions of a bright, long-lasting feature observed in solar granulation, which we call the plume. Methods: We used the spectral observations of quiet granulation at solar disc center, including the two Fe II 5234 and Fe I 6393 Å lines recorded simultaneously at

We report the discovery of gas streaming motions along nuclear spiral arms toward the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Hα, [N II] λ6584, and [S II] λλ6717, 6731 emission lines of

As part of our ongoing Chandra/HST M31 transient program we report on two active sources recently detected in two Chandra ACIS observations. Source 1 We present two 5ks ACIS-I observations of the ongoing outburst of the M31 transient source CXOM31 J004217.0+411508 (r3-46). Using an absorbed powerlaw model with photon index = 1.7 and nH = 6.6e20