... 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. ...

... Bad Astronomy . Misconceptions . ... Bad Astronomy : "We're light years more advanced than our competition!" ... Even the closest astronomical object, the Moon, is 400,000 kilometers away! ... A beam of light will travel 9,500,000,000,000 kilometers in one year. This distance is defined as a light year ; the distance light travels in a year. ... This is another example of Bad Astronomy; like a light year, a parsec is a unit of distance, not time (to be specific, it equals 3.26 light years) . ...

... ESO is building what will be the World's largest optical telescope array, The Very Large Telescope (VLT). The VLT Project organisation is responsible for the design and construction of the Unit Telescopes, including enclosures, optics, adapter-rotators and coating unit. ... Unit Telescopes Overview - This page is outdated, an update is in process. ... Secondary mirror (M2 Unit) - This page is outdated, an update is in process. ... Coating Unit - This page is outdated, an update is in process. ...

... hcorcal value versus freq from sky and absorber . ... power levels during hcorcal measurements . Ratio of other cals to hcorcal tracking blank sky. ... Measuring the high correlated cal using blank sky and absorber . ... The high correlated cal value (diode 1 going to polA and polB) for lband wide was measured 06mar03 on the telescope using the sky/absorber technique. ... Fig 1 is the measured cal value in deg K versus frequency. ... The hcorcal was measured 3 times in each set of 10 measurements. ...

We present a time-lapse sequence of 20 near-infrared ( J and K band) snapshots of the central 20 20 of the Crab pulsar wind nebula, taken at subarcsecond resolution with the Hokupa`a/QUIRC adaptive optics camera on the Gemini North Telescope and sampled at intervals of 10 minutes and 24 hr. It is observed that the equatorial wisps and polar knots in the termination shock of the pulsar wind appear to fluctuate in brightness on kilosecond timescales. ...

... 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. ...

. Pulkovo Observatory of Russian Academy of Sciences is situated . near Saint-Petersburg. It was founded in 1839. 196140, Saint-Petersburg, Pulkovskoye chaussee 65/1 . English version . Russian version . This page has been accessed times since May 1, 1999.

We measure the extinction curve in the central 200 pc of M31 at mid-ultraviolet to near-infrared wavelengths (from 1928 У? to 1.5 ЮМm), using Swift/UVOT and Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3)/Advanced Camera for Surveys (ACS) observations in 13 bands. ... The extinction curves of these clumps (RV = 2.4-2.5) are steeper than the average Galactic one (RV = 3.1), but are similar to optical and near-infrared curves recently measured toward the Galactic bulge (RV ~ 2.5). ...

... We have studied scaling relations (virial mass versus CO luminosity, luminosity versus size, linewidth versus size) for molecular clouds in the 30 Dor and N 159 regions in the Large Magellanic Cloud. ... The study of molecular clouds in the Galaxy has resulted in a number of scaling relations between global cloud properties such as mass, density, luminosity, size and velocity dispersion (e.g. Larson (1981) , Scoville & Sanders (1987) , Solomon et al. ... Elmegreen B.G., 1989, ApJ , 338 , 178. ...

... GSAOI Home . ... Science . ... They used Cepheid variables out to 20 Mpc as the calibrating method for a host of secondary distance indicators such as Type Ia supernovae, surface brightness fluctuations, and the Tully Fisher method. ... Luminous red supergiants provide a new method of measuring the Hubble constant that is independent of the Cepheid distances. ... Larger spiral galaxies will yield larger numbers of red supergiants and hence a more accurate distance modulus. ...

... The task also issues a number of housekeeping related messages and values and also writes several keywords to the EXPOSURE extension (the information is usually CCD-dependent and it is thus important that it is kept and propagated through the event file processing chain). ... Filter: the filter wheel position is derived from the position sensor potentiometer (housekeeping column F1122 contained in the main periodic housekeeping file PNPMH1 , HK mnemonic H_CE_FWSPOT). ...

Noise Equivalent Passband . ... Schade showed that the noise bandwidth was a good subjective measure of image quality. ... The mean square value of the gradient Q'(x) of the intensity distribution across and edge trace, within certain limits, normalized to unit intensity difference. ... It should be emphasized that subjective sharpness is dependent on the actual intensity step, or contrast, at an edge, as well as the intensity profile across the edge. ... Considering the case of a single bar target. ...

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. ...

The ESA/ESO Astronomy Exercise Series 2 . The Distance to Messier 100 as Determined by Cepheid Variable Stars . ... The small variations in distance to the individual Cepheid variable stars in the Cloud are negligible compared with the much larger distance to the SMC. ... In this way Cepheid variable stars can be used as one of the 'standard candles' in the Universe that act either as distance indicators themselves or can be used to calibrate (or set the zero point for) other distance indicators. ...

... IC 418: The Spirograph Nebula . ... Credit: NASA , ESA , and the Hubble Heritage Team ( STScI / AURA ); Acknowledgement: R. Sahai ( JPL ) et al. ... Dubbed the Spirograph Nebula for its resemblance to drawings from a cyclical drawing tool , planetary nebula IC 418 shows patterns that are not well understood. ... IC 418 lies about 2000 light-years away and spans 0.3 light-years across. ... Publications with keywords: IC 418 - planetary nebula . Publications with words: IC 418 - planetary nebula . ...

... The concepts of Fourier frequency and wavelet duration are obviously related. ... Among many sensible definitions, we chose to require that the peak of the wavelet mean spectrum should be matched with the singularity of the Fourier transform of the cosine wave. Then, it can be shown that the frequency of the cosine is related to the wavelet duration by the relation . ... The ambiguous definition of the duration of an event is common to the sizing of any object of irregular shape. ...

... Impedance . Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. ... Resistance is the real part of impedance; a device with a purely resistive impedance exhibits no phase shift between the voltage and current. ...

... Institute for Cosmophysical Research and Aeronomy (IKFIA) (Yakutsk). ... IRE RAN (Moscow). Russian Foundation for Basic Research (Moscow). ... Institute for Remote Environmental Research AEN (Moscow) . ... Russian Federal Research Institute of Fisheries and Oceanography (Moscow) . ... Russian Federal Research Institute of Fishery and Oceanography KamchNIRO. ... Russian Federal Research Institute of Fishery and Oceanography. ... Russian Federal Research Institute of Fishery and Oceanography VNIRO. ...

... 22.Reference Frames . ... To derive the motion of a penny dropped inside an airliner moving at 600 miles/hr (about 1000 km/hr)--should we calculate it with respect to the interior of the airliner, or with respect to the ground? ... And if a similar penny is let go inside an orbiting spaceship--should its motion be calculated relative to the interior of the spaceship, or relative to the Earth outside? ... How do observations differ in the two frames--the airliner cabin and the Earth? ...

Next: Carbon stars Up: OTHER HYDROGEN-DEFICIENT STARS Previous: Extreme helium stars and . V348sgr may be more closely related to about twenty hydrogen-deficient central stars of planetary nebulae which have similar carbon abundances ( ) and strong emission line spectra ([ Leuenhagen et al. 1995 ], [ Leuenhagen & Hamann 1997 ]). ... Hydrogen-deficient and carbon-rich knots are seen in the inner nebulae of at least two objects (Abell 30 and Abell 78). ...