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251.
Shinsuke Abe Noboru Ebizuka Hideyuki Murayama Katsuhito Ohtsuka Satoru Sugimoto Masa-yuki Yamamoto Hajime Yano Jun-ichi Watanabe Jiří Borovička 《Earth, Moon, and Planets》2004,95(1-4):265-277
Spectra of persistent meteor trains were observed at wavelength between 300 and 930 nm. Two obtained train spectra during
the 1998 and 2001 Leonid meteor showers are reported here. During the 1998 Leonids, one train was detected by a photographic
camera with a spectrograph covering 370–640 nm region. On the other hand, during the 2001 Leonids, video observations were
carried out using image intensified cameras in ultraviolet (UV), visible and near infrared (near-IR) wavelengths. Temperatures
in persistent trains have been measured by atmospheric O2 A(0,1) band at the wavelength near 864.5 nm. From a video spectrum obtained just 7 s after parent fireball’s flare, a rotational
temperature of 250 K at altitude of 88.0±0.5 km was estimated. We can say that the cooling time scale of train strongly depends
on the initial mass of its fireball at least for Leonids. Based on cooling constant calculated from our results, we estimated
a temperature of ∼
∼130 K as a final exothermic temperature at early stage of persistent trains. 相似文献
252.
Velocity determination of 131 head echoes recorded during Perseid meteor shower observations by the Canadian 2 MW radar, has
been performed under the assumption of either their constant velocity or of its linear change with time. Even though the constant
velocities concentrated at 60 km s-1 generally accepted for the Perseids, a substantial number of echoes had velocities either
lower than 60 km s-1 or greater than this value. The inclusion of variable velocity into considerations led to surprising
result that a great portion of the head echoes accelerated (3 possibly decelerating echoes in comparison with 33 accelerating
cases on the level of relative standard deviations of output parameters not exceeding 10%). It seems that the allocation of
the ionization responsible for the head echo is not entirely identical with the instantaneous meteoroid position. As a consequence,
the velocity derived from the measured head echo coordinates can differ from the velocity of parent body. We are not able
to explain this finding at present.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
253.
Bandwidth effects in the GAIA photometric system 3G are discussed. It is demonstrated that careful account for the bandwidth
effects in any proposed GAIA photometric system has to be made, in order to determine the fundamental parameters of heavily
reddened stars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
254.
We investigate the plausibility of using diffuse interstellar band at862 nm for tracing interstellar extinction with the ESA's
astrometric space mission GAIA. For this purpose we perform numerical tests to simulate the conditions of real observations,
covering a wide range of stellar parameters and different amounts of interstellar extinction. Our simulations indicate that
with the present Radial Velocity Spectrometer setup the uncertainty in color excess of σE(B-V)≤ 0.05 can be achieved only for the interstellar reddening tracers brighter than V ∼ 13. None of the plausible tracers can provide accurate color excesses (σ
E(B-V)
≤ 0.05) at the distances beyond 2 kpc. We therefore conclude that with the currently planned instrumentation onboard GAIA
this method can not be used as a stand-alone approach for probing interstellar extinction on the Galactic distance scales
within the framework of the GAIA mission.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
255.
The paper describes the JHK colours of late-type stars which were investigated as part of a survey of South Galactic Cap (b < -30°) IRAS sources selected on the basis of their 12/25µm flux ratios as high mass-loss candidates. Near-infrared two-colour diagrams provide an effective technique for distinguishing between various groups of late-type stars. Such diagrams are also useful in indicating which stars are likely to be peculiar and worthy of more detailed study. The late-type stars isolated by this survey comprise: 61 Mira variables (3 of which are carbon stars with very thick shells), 3 young stellar objects, 4 interacting binaries, 2 semi-regular carbon variables and 154 oxygen-rich giants. 相似文献
256.
We present a software package developed for the automatic 4-D stellar parameterization. The package can be adopted to virtually
any multicolour photometric system. Procedure of simultaneous determination of T
eff, log g, [M/H] and E
B-V is very flexible and can be performed by applying various photometric parameters(magnitudes, colour indices etc.). Any changes
of the photometric systems, weighting schemes or parameterization criteria can be implemented easily.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
257.
J. Klačka 《Earth, Moon, and Planets》1994,64(1):95-98
The problem of the stability of the zodiacal cloud is scrutinized. The central idea of the paper sticks in the theoretical treatment of the action of the solar electromagnetic radiation on small interplanetary dust particles (IDPs). It is suggested that the virtual problem of the (in-)stability of the zodiacal cloud originated from the physically incorrect application of the Poynting-Robertson effect on IDPs. Real particles are not of spherical shape and so the braking acceleration is not proportional to -v/c. Depending on the shape (and other optical properties) of the particle, also spiralling outward from the Sun may occur. 相似文献
258.
Michael Feast Patricia Whitelock John Menzies 《Monthly notices of the Royal Astronomical Society》2002,329(1):L7-L12
A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs has been used to derive estimates of M K for cluster Miras, including one in the Small Magellanic Cloud (SMC) globular cluster NGC 121. These lead to a zero-point of the Mira infrared period–luminosity (PL) relation, PL( K ), in good agreement with that derived from Hipparcos parallaxes of nearby field Miras. The mean of these two estimates together with data on LMC Miras yields a Large Magellanic Cloud (LMC) distance modulus of in evident agreement with a metallicity-corrected Cepheid modulus .
The use of luminous asymptotic giant branch (AGB) stars as extragalactic population indicators is also discussed. 相似文献
The use of luminous asymptotic giant branch (AGB) stars as extragalactic population indicators is also discussed. 相似文献
259.
260.