Simultaneous UBVRI observations of the cataclysmic variable AE Aquarii: Temperatures and masses of fireballs     

R.K. Zamanov  G.Y. Latev  K.A. Stoyanov  S. Boeva  B. Spassov  S.V. Tsvetkov 《Astronomische Nachrichten》2012,333(8):736-743

We report simultaneous multicolour observations in 5 bands (UBVRI) of the flickering variability of the cataclysmic variable AE Aqr. Our aim is to estimate the parameters (colours, temperature, size) of the fireballs that produce the optical flares. The observed rise times of the optical flares are in the interval 220‐440 s. We estimate the dereddened colours of the fireballs as (U ‐B)₀∼0.8‐1.4, (B ‐V)₀∼0.03‐0.24, and (V ‐I)₀∼0.26‐0.78. We find for the fireballs temperatures of 10000‐25000 K, masses of (7‐90)x10¹⁹ g, and sizes of (3‐7)x10⁹ cm (using a distance of d = 86 pc). These values refer to the peak of the flares observed in the UBVRI bands. The data are available upon request from the authors (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

封闭条件下抛石路堤降温效果及机理的试验研究   总被引：22，自引：13，他引：9  

赖远明  张明义  喻文兵  高志华 《冰川冻土》2004,26(5):576-581

在多年冻土地区道路工程的修筑与维护中, 如何保证多年冻土不退化所采取措施的长期可靠度问题日益为人们所关注. 通过室内试验研究了实际工程中半开放半封闭抛石路堤受到风沙或积雪填埋后,在不同温度变幅条件下的降温效果. 实验结果发现: 在满足一定厚度时, 封闭条件下的块石层仍具有良好的降温效果, 具有可变等效导热系数的特性, 在实验中充分体现了"热二极管效应". 在外界温度变幅较大的条件下, 降温速度和降温效率均大于温度变幅较小的情况. 通过对块石层顶底温差与其顶部温度变化关系, 以及块石层内温度场特征的分析, 证实了封闭块石层内自然对流的真实存在和对流的运动发展趋势. 试验结果为抛石路堤降温的长期可靠性提供了依据.  相似文献   

Gravity and effective temperature distribution on the surface of contact binary systems     

S. Tsantilas  H. Rovithis‐Livaniou 《Astronomische Nachrichten》2008,329(6):596-601

The aim of this work is to study the gravity and the effective temperature distribution on the outer equipotential surface of a contact binary. In particular, the lines of constant g, (the iso‐g curves), are computed and plotted on the outer surface C_s of contact configurations. Since the gravity distribution would also specify the effective temperature distribution on the binary's common photosphere through the gravity darkening effect, these lines correspond to isothermals too. Applications have been made to two contact binaries; namely, to AW UMa and OO Aql, two systems with very different mass ratios. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

On the dynamics of a twisted disc immersed in a radiation field     

P. B. Ivanov  J. C. B. Papaloizou 《Monthly notices of the Royal Astronomical Society》2008,384(1):123-149

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Neutron star spin–kick velocity correlation effect on binary neutron star coalescence rates and spin–orbit misalignment of the components     

K. A. Postnov  A. G. Kuranov 《Monthly notices of the Royal Astronomical Society》2008,384(4):1393-1398

We study the effect of the neutron star spin–kick velocity alignment observed in young radio pulsars on the coalescence rate of binary neutron stars. Two scenarios are considered for neutron star formation: when the kick is always present, and when it is small or absent if a neutron star is formed in a binary system as a result of electron-capture degenerate core collapse. The effect is shown to be especially strong for large kick amplitudes and tight alignments, reducing the expected galactic rate of binary neutron star coalescence compared to calculations with randomly directed kicks. The spin–kick correlation also leads to a much narrower neutron star spin–orbit misalignment.  相似文献   

On the evolutionary status of short-period cataclysmic variables     

S. P. Littlefair  V. S. Dhillon  T. R. Marsh  B. T. Gänsicke  John Southworth  I. Baraffe  C. A. Watson  C. Copperwheat 《Monthly notices of the Royal Astronomical Society》2008,388(4):1582-1594

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RR Pic (1925): a Chandra X-ray view     

Y. Pekön  &#;. Balman 《Monthly notices of the Royal Astronomical Society》2008,388(2):921-926

We present the Chandra ACIS-S3 data of the old classical nova RR Pic (1925). The source has a count rate of 0.067 ± 0.002 count s⁻¹ in the 0.3–5.0 keV energy range. We detect the orbital period of the underlying binary system in the X-ray wavelengths. We also find that the neutral hydrogen column density differs for orbital minimum and orbital maximum spectra with values  0.25^+0.23_−0.18× 10²²  and  0.64^+0.13_−0.14× 10²² cm⁻²  at 3σ confidence level. The X-ray spectrum of RR Pic can be represented by a composite model of bremsstrahlung with a photoelectric absorption, two absorption lines centered around 1.1–1.4 keV and five Gaussian lines centered at emission lines around 0.3–1.1 keV corresponding to various transitions of S, N, O, C, Ne and Fe. The bremsstrahlung temperature derived from the fits ranges from 0.99 to 1.60 keV and the unabsorbed X-ray flux is found to be  2.5^+0.4_−1.2× 10⁻¹³ erg  cm⁻² s⁻¹  in the 0.3–5.0 keV range with a luminosity of 1.1 ± 0.2  10³¹ erg s⁻¹  at 600 pc. We also detect excess emission in the spectrum possibly originating from the reverse shock in the ejecta. A fit with a cooling flow plasma emission model shows enhanced abundances of He, C, N, O and Ne in the X-ray emitting region indicating existence of diffusive mixing.  相似文献   

A Photometric Study of the W UMa-Type Contact Binary RZ Corn     

Jia-Jia He  Sheng-Bang Qian 《中国天文和天体物理学报》2008,8(4)

We present results of CCD photometric observations of the short-period W UMatype contact binary system, RZ Com. The light curve of the binary has changed from Wsubtype to A-subtype from 1998 to 2003, then back to W-subtype in 2004. An analysis was carried out using the 2003 version of the Wilson-Devinney code. It is confirmed that RZ Com is a low-degree, overcontact f = 20.1% (±7.4%) binary system with a high inclination of i = 81.°40 (±0.°40), and a mass ratio q = 2.351 (±0.031). Combining four newly determined times of light minimum with others in the literature, the variations in orbital period is examined. A small-amplitude oscillation (A=0.0065d), with a period of 41.5 year, is discovered superimposed on a long-term increase at rate dP/dt = +3.97×10-8d yr-1. The period oscillation can be explained either by the light-time effect due to the presence of an unseen third body, or by cycles of magnetic activity on the components. Combining our photometric solution with the spectroscopic elements obtained by Mclean & Hilditch, the absolute dimensions of RZ Com are: M1 = 1.14 (+0.19)Mo, M2 = 0.50 (-4-0.09)Mo, R1= 1.12 (±0.01)R⊙, R2 = 0.78 (±0.01)R⊙ and A = 2.41 (±0.02)R⊙.  相似文献   

S193: another non-eclipsing SW Sex star     

I. G. Martínez-Pais  P. Rodríguez-Gil  J. Casares 《Monthly notices of the Royal Astronomical Society》1999,305(3):661-670

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Relativistic distortions in the X-ray spectrum of Cyg X-1     

C. Done  P. T. &#;ycki 《Monthly notices of the Royal Astronomical Society》1999,305(2):457-468

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