Context: Below 1 mHz, the power spectrum of helioseismic velocity measurements is dominated by the spectrum of convective motions (granulation and supergranulation) and it is difficult to detect the low-order acoustic modes and gravity modes. Aims: We attempt to understand more clearly the behavior of solar granulation as a function of observing

A series of missions will be launched over the next few decades that will be designed to detect and characterize extrasolar planets around nearby stars. These missions will search for habitable environments and signs of life (biosignatures) in planetary spectra. The vegetation's ``red edge,'' an enhancement in the Earth's spectrum near 700 nm when

The measurement of Doppler velocity shifts in spectra is a ubiquitous theme in astronomy, usually handled by computing the cross-correlation of the signals and finding the location of its maximum. This paper addresses the problem of the determination of wavelength or velocity shifts among multiple spectra of the same, or very similar, objects. We

The velocity field of the nearly face-on galaxy NGC 3631 is derived from observations in the Hα line on the 6-m telescope of the Special Astrophysical Observatory. These optical data are compared with radio observations of this galaxy (Knapen 1997). It is argued that the two-armed spiral structure of NGC 3631 has a wave nature, and that the

PSR B1951+32 is a gamma -ray pulsar detected by the Energetic Gamma Ray Experiment Telescope (EGRET) and identified with the 39.5 ms radio pulsar in the supernova remnant CTB 80. The pulsar energy spectrum is consistent with an unbroken power law with differential photon index of -1.8 +/- 0.1 between 50 MeV and 10 GeV. The EGRET data shows no

As part of a systematic survey for the search of high velocity gas in giant extragalactic H II regions, the authors have observed the five largest and brightest H II regions in M101. They have found two types of peculiar emission profiles: (1) a broadening of the Hα emission line at low intensity, in excess of the values expected for the typical