Results 1 - 10 of 2535
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[en] High quality is required to the electronic which works with bolometer made of metal for measuring the radiation power in plasmaphysical experiments. If the bandwidth is to be 1 kHz, and the time constant of the bolometer is about 160 ms by high overall gain the critical parameters are the noise of the amplifier, pick up to the system, stability and decoupling of common mode signals. The high overall gain is necessary to be able to measure lowest radiation power. The design made is a good approach to the desired property. (orig.)
[de]An eine Elektronik zum Betrieb von Metallbolometern fuer die Messung der Strahlungsleistung in plasmaphysikalischen Experimenten werden hohe Anforderungen gestellt. Soll eine Grenzfrequenz von 1 kHz erreicht werden, bei einer Zeitkonstante des Bolometers von 160 ms, dann sind die kritischen Werte bei hoher Gesamtverstaerkung das Rauschen des Verstaerkers, Fremdspannungseinkopplung (Brumm), Stabilitaet und Entkopplung von Gleichtaktsignalen. Die hohe Verstaerkung ist notwendig, um noch kleinste Strahlungsleistung nachzuweisen. Die ausgefuehrte Schaltung stellt einen guten Kompromiss zwischen diesen gewuenschten Eigenschaften dar. (orig.)
[en] The Infrared Flux Method (IRFM) is one of the most accurate techniques to derive fundamental stellar parameters - namely effective temperatures, bolometric luminosities and angular diameters - in an almost model independent way. We review the method and its application to late-type dwarfs, with particular emphasis on the dependence of the resulting effective temperatures on the adopted absolute calibration. We also compare our results with a large set of recent interferometric angular diameters in order to better constrain the temperature scale: despite the excellent agreement we find, uncertainties of order 100 K cannot yet be ruled out. We conclude that although such disturbing uncertainty still plagues the determination of accurate effective temperatures, the homogeneous and internally precise fundamental stellar parameters determined via IRFM permit the study of the fine structure of the lower main sequence in greater detail than ever before.
[en] Using data of three well observed Type II plateau supernovae (SNe II-P), SNe 1987A, 1999em, and 2003hn, and two atmosphere models by Eastman et al. and Dessart and Hillier, we derive calibrations for bolometric corrections and effective temperature from BVI photometry. The typical scatter of the bolometric correction is 0.11 mag. With these results we obtain bolometric light curves and effective temperature evolution for a sample of 33 SNe II-P. The SN sample shows a range of 1 dex in plateau luminosity and plateau durations from 75 to 120 days. Comparing the shape of the transition between the plateau and the radioactive tail, we find that the size of the drop is in the range of 0.8-1.12 dex.
[en] Several alternative neutrino detection schemes are described briefly and compared. It is suggested that a ballistic-phonon experiment might be promising. In such an experiment the amplitude received at a bolometer would depend on the distance it is from the neutrino event, and also on the direction because of phonon focusing, so several bolometers suggested to locate the event position from the difference in arrival times. The design of such an experiment is discussed assuming the phonons are detected by conventional superconducting bolometers. Determination of the direction of neutrino flux would be obtained from a study of the distribution of direction of the tracks of recoiling electrons or nuclei. The problem of smearing out the effective source over a distance of approximately a mean free path is addressed, and the need for high-resolution phonon focusing studies is expressed
[en] A tin bolometer evaporated on an anodized aluminum block is described. The noise equivalent power of the bolometer is of 10-13 watt Hzsup(-1/2) and the time constant is 3μ sec. The bolometer is a suitable fast molecular beam detector
[en] When making use of tabulations of empirical bolometric corrections for stars (BCV), a commonly overlooked fact is that while the zero point is arbitrary, the bolometric magnitude of the Sun (Mbol,sun) that is used in combination with such tables cannot be chosen arbitrarily. It must be consistent with the zero point of BCV so that the apparent brightness of the Sun is reproduced. The latter is a measured quantity, for which we adopt the value Vsun = -26.76 ± 0.03. Inconsistent values of Mbol,sun are listed in many of the most popular sources of BCV. We quantify errors that are introduced by failure to pay attention to this detail. We also take the opportunity to reprint the BCV coefficients of the often used polynomial fits by Flower, which were misprinted in the original publication.
[en] We present an analysis of the relation between the star formation rate (SFR) and mass of dense gas in Galactic clumps and nearby galaxies. Using the bolometric luminosity as a measure of SFR and the molecular line luminosity of HCO+ (3-2) as a measure of dense gas mass, we find that the relation between SFR and Mdense is approximately linear. This is similar to published results derived using HCN (1-0) as a dense gas tracer. HCO+ (3-2) and HCN (1-0) have similar conditions for excitation. Our work includes 16 Galactic clumps that are in both the Bolocam Galactic Plane Survey and the Red MSX Source Survey, 27 water maser sources from the literature, and the aforementioned HCN (1-0) data. Our results agree qualitatively with predictions of recent theoretical models which state that the nature of the relation should depend on how the critical density of the tracer compares with the mean density of the gas.