Rejuvenation of spiral bulges     

Daniel Thomas  Roger L. Davies 《Monthly notices of the Royal Astronomical Society》2006,366(2):510-520

  相似文献   

The submillimetre properties of gamma-ray burst host galaxies     

N. R. Tanvir  V. E. Barnard  A. W. Blain  A. S. Fruchter  C. Kouveliotou  P. Natarajan  E. Ramirez-Ruiz  E. Rol  I. A. Smith  R. P. J. Tilanus  R. A. M. J. Wijers 《Monthly notices of the Royal Astronomical Society》2004,352(3):1073-1080

  相似文献   

Watching meteors on Triton     

W. Dean Pesnell  J.M. Grebowsky 《Icarus》2004,169(2):482-491

The thin atmosphere of Neptune's moon Triton is dense enough to ablate micrometeoroids as they pass through. A combination of Triton's orbital velocity around Neptune and its orbital velocity around the Sun gives a maximum meteoroid impact velocity of approximately 19 km s⁻¹, sufficient to heat the micrometeoroids to visibility as they enter. The ablation profiles of icy and stony micrometeoroids were calculated, along with the estimated brightness of the meteors. In contrast to the terrestrial case, visible meteors would extend very close to the surface of Triton. In addition, the variation in the meteoroid impact velocity as Triton orbits Neptune produces a large variation in the brightness of meteors with orbital phase, a unique Solar System phenomenon.  相似文献   

Extinction due to amorphous carbon grains in red quasars from the Sloan Digital Sky Survey     

B. Czerny  J. Li  Z. Loska  R. Szczerba 《Monthly notices of the Royal Astronomical Society》2004,348(3):L54-L57

  相似文献   

The effect of rotational gravity darkening on magnetically torqued Be star discs     

J. C. Brown  D. Telfer  Q. Li  R. Hanuschik  J. P. Cassinelli  A. Kholtygin 《Monthly notices of the Royal Astronomical Society》2004,352(3):1061-1072

  相似文献   

Mass transfer in tidally unstable compact binaries     

M. R. Truss 《Monthly notices of the Royal Astronomical Society》2005,356(4):1471-1476

The 2001 outburst of WZ Sagittae has shown the most compelling evidence yet for an enhancement of the mass-transfer rate from the donor star during a dwarf nova outburst in the form of hotspot brightening. I show that, even in this extreme case, the brightening can be attributed to tidal heating near the interaction point of an accretion stream with the expanding edge of an eccentric accretion disc, with no need at all for an increase in the mass-transfer rate. Furthermore, I confirm previous suggestions that an increase in mass-transfer rate through the stream damps any eccentricity in an accretion disc and suppresses the appearance of superhumps, in contradiction to observations. Tidal heating is expected to be most significant in systems with small mass ratios. It follows that systems like WZ Sagittae – which has a tiny mass ratio – are those most likely to show a brightening in the hotspot region.  相似文献   

Kinematic properties and stellar populations of faint early-type galaxies – I. Velocity dispersion measurements of central Coma galaxies     

A. Matkovi&#;  R. Guzmán 《Monthly notices of the Royal Astronomical Society》2005,362(1):289-300

We present velocity dispersion measurements for 69 faint early-type galaxies in the core of the Coma cluster, spanning  −22.0 ≲ M_R ≲−17.5 mag  . We examine the   L –σ  relation for our sample and compare it to that of bright elliptical galaxies (Es) from the literature. The distribution of the the faint early-type galaxies in the   L –σ  plane follows the relation   L ∝σ^2.01±0.36  , which is significantly shallower from   L ∝σ⁴  as defined for the bright Es. While increased rotational support for fainter early-type galaxies could account for some of the difference in slope, we show that it cannot explain it. We also investigate the colour–σ relation for our Coma galaxies. Using the scatter in this relation, we constrain the range of galaxy ages as a function of their formation epoch for different formation scenarios. Assuming a strong coordination in the formation epoch of faint early-type systems in Coma, we find that most had to be formed at least 6 Gyr ago and over a short 1-Gyr period.  相似文献   

Do accretion discs regulate the rotation of young stars?   总被引：1，自引：0，他引：1  

S. P. Littlefair  Tim Naylor  Ben Burningham  R. D. Jeffries 《Monthly notices of the Royal Astronomical Society》2005,358(2):341-352

We present a photometric study of I -band variability in the young cluster IC 348. The main purpose of the study was to identify periodic stars. In all, we find 50 periodic stars, of which 32 were previously unknown. For the first time in IC 348, we discover periods in significant numbers of lower-mass stars  ( M < 0.25 M_⊙)  and classical T Tauri stars. This increased sensitivity to periodicities is a result of the enhanced depth and temporal density of our observations, compared with previous studies. The period distribution is at first glance similar to that seen in the Orion nebula cluster (ONC), with the higher-mass stars  ( M > 0.25 M_⊙)  showing a bi-modal period distribution concentrated around periods of 2 and 8 d, and the lower-mass stars showing a uni-modal distribution, heavily biased towards fast rotators. Closer inspection of the period distribution shows that the higher-mass stars show a significant dearth of fast rotators, compared to the ONC, whilst the low-mass stars are rotating significantly faster than those in Orion. We find no correlation between rotation period and K – L colour or Hα equivalent width.
We also present a discussion of our own IC 348 data in the context of previously published period distributions for the ONC, the Orion flanking fields and NGC 2264. We find that the previously claimed correlation between infrared excess and rotation period in the ONC might, in fact, result from a correlation between infrared excess and mass. We also find a marked difference in period distributions between NGC 2264 and IC 348, which presents a serious challenge to the disc-locking paradigm, given the similarity in ages and disc fractions between the two clusters.  相似文献   

Formation of Kuiper-belt binaries through multiple chaotic scattering encounters with low-mass intruders     

Sergey A. Astakhov  Ernestine A. Lee  David Farrelly 《Monthly notices of the Royal Astronomical Society》2005,360(2):401-415

  相似文献   

XMM–Newton observations of polars in low accretion states     

Gavin Ramsay  Mark Cropper  Kinwah Wu  K. O. Mason  F. A. Córdova  W. Priedhorsky 《Monthly notices of the Royal Astronomical Society》2004,350(4):1373-1384

  相似文献