... Mindful of these biases, I can now explore the relations between the measured rotation periods and various other observables. The hypothesis behind monitoring stellar variability is that active stars have asymmetric spot distributions on their photospheres. ... They found that only stars with rotation periods greater than seven days show variations greater than 0.4 magnitudes at I. Bouvier et al . ... 1993a) demonstrated a relation between X--ray flux and spectral type in ZAMS stars. ...

A comparative study of type I and type II supernovae . ... Sternberg State Astronomical Institute, Moscow, U.S.S.R. (Received 26 November, 1985) . ... No significant difference between SNe I and SNe II has been found in their radial distribution and frequency of outbursts in spiral galaxies. ... The radial distribution of type Ia SNe in spiral galaxies is only slightly steeper than the one for SNe II, while SNe Ib/c are more concentrated towards the central regions. ...

We compare atomic gas, molecular gas, and the recent star formation rate (SFR) inferred from HЮБ in the Small Magellanic Cloud (SMC). ... This allows us to disentangle conversion factor effects from the impact of metallicity on the formation and star formation efficiency of molecular gas. ... At a fixed total gas surface density the SMC has a 5-10 times lower molecular gas fraction (and star formation rate) than large spiral galaxies. ...

... The distribution of galactic RCB stars is controversial. Several authors have argued that they belong to a thick galactic disk, and are thus old Population I stars. However, they may alternatively belong to the even older galactic bulge (Population II). ... In either case, the populations are sufficiently old that RCB stars must have relatively low masses ( ). ... These are the only RCB stars for which a distance is known and hence for which an absolute magnitude can be deduced. ...

International Service of Geomagnetic Indices (ISGI) of the IAGA . ... World Data Center C1 for Geomagnetism (WDC-C1), . Solar-Terrestrial Physics Division in Copenhagen, Denmark . ... Sodankyl Geophysical Observatory Geomagnetic and Ionospheric Data . Space Physics Text Book (Oulu): Magnetic activity indices . ... Solar Data Analysis Center (SDAC) . ... Mauna Loa Solar Observatory Analysis Center of HAO/NCAR in Boulder, Colorado . ... Neutron Monitor Server , University of Chicago . ...

... RelatedљPages . ... FITS-WCS and related software . Several implementations of the FITS WCS standards are available: . The WCSLIB software distribution (i.e. this library) may be obtained from http://www.atnf.csiro.au/people/Mark.Calabretta/WCS/ . ... The Kapteyn Package http://www.astro.rug.nl/software/kapteyn/ by Hans Terlouw and Martin Vogelaar. pywcs , http://stsdas.stsci.edu/astrolib/pywcs/ by Michael Droettboom. ... Gentoo, http://packages.gentoo.org/package/sci-astronomy/wcslib . ...

... A universal physical relation for quasars . ... Harvey Tananbaum and his collaborators have first observed a relation between the soft X-ray and the optical/ultraviolet emission in AGN in 1979. Such relation is nonlinear, and it is usually parameterized as dependence between the logarithm of the monochromatic luminosities at 2500 †Е ( L 2500†Е ) and 2 keV ( L 2keV ) . ... Yet, the dispersion along the L 2500†Е тАУ L 2keV relationship is found to be rather high, typically ~0.35тАУ0.4 in log units. ...

Next: Estimating the angle Up: Wavelength Calibration Previous: General Description . The wavelength calibration involves a physical equation, the echelle relation and regression analysis to achieve estimates of the dispersion relation. Provided that the echelle dispersion is performed with a grating, any echelle spectrum can be calibrated usually with four lines used as pre-identifications and a catalog of laboratory wavelengths associated to the calibration lamp. ... E