3.8-μm photometry during the secondary eclipse of the extrasolar planet HD 209458b     

Drake Deming †  L. Jeremy Richardson  Joseph Harrington 《Monthly notices of the Royal Astronomical Society》2007,378(1):148-152

We report infrared photometry of the extrasolar planet HD 209458b during the time of secondary eclipse (planet passing behind the star). Observations were acquired during two secondary eclipses at the NASA Infrared Telescope Facility (IRTF) in 2003 September. We used a circular variable filter (1.5 per cent bandpass) centred at 3.8 μm to isolate the predicted flux peak of the planet at this wavelength. Residual telluric absorption and instrument variations were removed by offsetting the telescope to nearby bright comparison stars at a high temporal cadence. Our results give a secondary eclipse depth of 0.0013 ± 0.0011, not yet sufficient precision to detect the eclipse, whose expected depth is  ∼0.002 –0.003  . We here elucidate the current observational limitations to this technique, and discuss the approach needed to achieve detections of hot Jupiter secondary eclipses at 3.8 μm from the ground.  相似文献   

A deep AAOmega survey of low-luminosity galaxies in the Shapley supercluster: stellar population trends     

Russell J. Smith  John R. Lucey  Michael J. Hudson 《Monthly notices of the Royal Astronomical Society》2007,381(3):1035-1052

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Dust masses and abundances in planetary nebulae: likely strong elemental depletion in low-abundance sources     

J. P. Phillips 《Monthly notices of the Royal Astronomical Society》2007,381(1):117-124

An analysis is undertaken of the relation between dust/gas mass ratios and elemental abundances within planetary nebulae (PNe). It is found that M _DUST/ M _GAS is broadly invariant with abundance, and similar to the values observed in asymptotic giant branch (AGB)-type stars. However, it is noted that the masses of dust observed in low-abundance PNe are similar to the masses of heavy elements observed in the gas phase. This is taken to imply that levels of elemental depletion must be particularly severe, and extend to many more species than have been identified so far. In particular, given that levels of C and O depletion are likely to be large, then this probably implies that species such as Fe, S, Si and Mg are depleted as well. There is already evidence for depletion of Fe, Si and Mg in individual PNe. It follows that whilst quoted abundances may accurately reflect gas-phase conditions, they are likely to be at variance with intrinsic abundances in low Z _N nebulae.
Finally, we note that there appears to be a variation in dust/gas mass ratios with galactocentric distance, with gradient similar to that observed for several elemental abundances. This may represent direct evidence for a correlation between dust/gas mass ratios and nebular abundances.  相似文献   

A kinematical approach to dark energy studies     

David Rapetti  Steven W. Allen  Mustafa A. Amin  Roger D. Blandford 《Monthly notices of the Royal Astronomical Society》2007,375(4):1510-1520

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Spectroscopic follow-up of a cluster candidate at z= 1.45     

Caroline van Breukelen  Garret Cotter  Steve Rawlings  Tony Readhead  David Bonfield  Lee Clewley  Rob Ivison  Matt Jarvis  Chris Simpson  Mike Watson 《Monthly notices of the Royal Astronomical Society》2007,382(3):971-984

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The flux ratio of the [O iii]λλ5007, 4959 lines in AGN: comparison with theoretical calculations     

M. S. Dimitrijevi&#;  L. &#;. Popovi&#;  J. Kova&#;evi&#;  M. Da&#;i&#;  D. Ili&#; 《Monthly notices of the Royal Astronomical Society》2007,374(3):1181-1184

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Evolution of binary stars and the effect of tides on binary populations   总被引：1，自引：0，他引：1  

Jarrod R. Hurley †  Christopher A. Tout  Onno R. Pols ‡ 《Monthly notices of the Royal Astronomical Society》2002,329(4):897-928

We present a rapid binary-evolution algorithm that enables modelling of even the most complex binary systems. In addition to all aspects of single-star evolution, features such as mass transfer, mass accretion, common-envelope evolution, collisions, supernova kicks and angular momentum loss mechanisms are included. In particular, circularization and synchronization of the orbit by tidal interactions are calculated for convective, radiative and degenerate damping mechanisms. We use this algorithm to study the formation and evolution of various binary systems. We also investigate the effect that tidal friction has on the outcome of binary evolution. Using the rapid binary code, we generate a series of large binary populations and evaluate the formation rate of interesting individual species and events. By comparing the results for populations with and without tidal friction, we quantify the hitherto ignored systematic effect of tides and show that modelling of tidal evolution in binary systems is necessary in order to draw accurate conclusions from population synthesis work. Tidal synchronism is important but, because orbits generally circularize before Roche lobe overflow, the outcome of the interactions of systems with the same semilatus rectum is almost independent of eccentricity. It is not necessary to include a distribution of eccentricities in population synthesis of interacting binaries; however, the initial separations should be distributed according to the observed distribution of semilatera recta rather than periods or semimajor axes.  相似文献   

The cluster substructure–alignment connection     

Manolis Plionis  Spyros Basilakos 《Monthly notices of the Royal Astronomical Society》2002,329(2):L47-L51

Using a sample of 903 APM clusters we investigate whether their dynamical status, as evidenced by the presence of significant substructures, is related to the large-scale structure of the Universe. We find that the cluster dynamical activity is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster. Furthermore, dynamically active clusters are more clustered than the overall cluster population. These are strong indications that clusters develop in a hierarchical fashion by anisotropic merging along the large-scale filaments within which they are embedded.  相似文献   

ON THE FORMATION AND MAINTENANCE MECHANISMS OF THE COLD WATER MASS OF THE YELLOW SEA   总被引：2，自引：0，他引：2  

李惠卿  袁业立 《中国海洋湖沼学报》1992,10(2):97-106

An analytical study is made on the formation of the Cold Water Mass of the Yellow Sea (CWYS) and the relevant thermally driven circulation. The temperature and velocity field, obtained by solving the coupled equations of motion and heat conduction, show that, in summer, the CWYS has a horizontal cyclonic circulation (component) with vertical upwelling in the middle and downwelling at the edges, that the vertical convection (u-w components) occurs only within a thin layer near the thermocline. and that the deeper layer remains almost motionless. This current structure represents well the mechanisms responsible for the maintenance of the thermocline or CWYS during the wanner months. Comparisons between the theoretical and observed temperatures show very good qualitative and quantitative agreements for corresponding seasons.  相似文献   

Precision timing measurements of PSR J1012+5307     

Ch. Lange  F. Camilo  N. Wex  M. Kramer  D.C. Backer  A.G. Lyne  O. Doroshenko 《Monthly notices of the Royal Astronomical Society》2001,326(1):274-282

We present results and applications of high-precision timing measurements of the binary millisecond pulsar J1012+5307. Combining our radio timing measurements with results based on optical observations, we derive complete 3D velocity information for this system. Correcting for Doppler effects, we derive the intrinsic spin parameters of this pulsar and a characteristic age of 8.6±1.9 Gyr . Our upper limit for the orbital eccentricity of only 8×10⁻⁷ (68 per cent confidence level) is the smallest ever measured for a binary system. We demonstrate that this makes the pulsar an ideal laboratory in which to test certain aspects of alternative theories of gravitation. Our precision measurements suggest deviations from a simple pulsar spin-down timing model, which are consistent with timing noise and the extrapolation of the known behaviour of slowly rotating pulsars.  相似文献