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 blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude

We have observed the 5.54 s anomalous X-ray pulsar XTE J1810-197 at radio, millimeter, and infrared (IR) wavelengths, with the aim of learning about its broadband spectrum. At the IRAM 30 m telescope, we have detected the magnetar at ν=88 and 144 GHz, the highest radio-frequency emission ever seen from a pulsar. At 88 GHz we detected numerous

We introduce the log(Hα/[SII]λλ6717+6731) versus log(Hα/[NII]λ6583) (S2N2) diagnostic diagram as a metallicity and ionization parameter indicator for HII regions in external galaxies. The location of HII regions in the S2N2 diagram was studied both empirically and theoretically. We found that, for a wide range of metallicities, the S2N2 diagram

Context: The masses previously obtained for the X-ray binary 2S 0921-630 inferred a compact object that was either a high-mass neutron star or low-mass black-hole, but used a previously published value for the rotational broadening (v sin i) with large uncertainties. Aims: We aim to determine an accurate mass for the compact object through an