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We present both photometry and spectra of the individual images of the quadruple gravitational lens system Q 2237+0305. Comparison of spectra obtained at two epochs, separated by ∼3 yr, shows evidence for significant changes in the emission line-to-continuum ratio of the strong ultraviolet C IV λ1549, C III ] λ1909 and Mg II λ2798 lines. The short, ∼1 day, light-travel time differences between the sight lines to the four individual quasar images rule out any explanation based on intrinsic variability of the source. The spectroscopic differences thus represent direct detection of microlensing-induced spectroscopic differences in a quasar. The observations allow constraints to be placed on the relative spatial scales in the nucleus of the quasar, with the ultraviolet continuum arising in a region of ≲0.05 pc in extent, while the broad emission-line material is distributed on scales much greater than this. 相似文献
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S. J. Warren D. J. Mortlock S. K. Leggett D. J. Pinfield D. Homeier S. Dye R. F. Jameson N. Lodieu P. W. Lucas A. J. Adamson F. Allard D. Barrado y Navascués M. Casali K. Chiu N. C. Hambly P. C. Hewett P. Hirst M. J. Irwin A. Lawrence M. C. Liu † E. L. Martín R. L. Smart L. Valdivielso B. P. Venemans 《Monthly notices of the Royal Astronomical Society》2007,381(4):1400-1412
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S. Dye N. W. Evans V. Belokurov S. J. Warren P. Hewett 《Monthly notices of the Royal Astronomical Society》2008,388(1):384-392
We model the extremely massive and luminous lens galaxy in the Cosmic Horseshoe Einstein ring system J1004+4112, recently discovered in the Sloan Digital Sky Survey. We use the semilinear method of Warren & Dye, which pixelizes the source surface brightness distribution, to invert the Einstein ring for sets of parametrized lens models. Here, the method is refined by exploiting Bayesian inference to optimise adaptive pixelization of the source plane and to choose between three differently parametrized models: a singular isothermal ellipsoid, a power-law model and a Navarro, Frenk & White (NFW) profile. The most probable lens model is the power law with a volume mass density ρ∝ r −1.96±0.02 and an axis ratio of ∼0.8. The mass within the Einstein ring (i.e. within a cylinder with projected distance of ∼30 kpc from the centre of the lens galaxy) is (5.02 ± 0.09) × 1012 M ⊙ , and the mass-to-light ratio is ∼30. Even though the lens lies in a group of galaxies, the preferred value of the external shear is almost zero. This makes the Cosmic Horseshoe unique amongst large separation lenses, as almost all the deflection comes from a single, very massive galaxy with little boost from the environment. 相似文献
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A. C. Becker E. Agol N. M. Silvestri J. J. Bochanski C. Laws A. A. West G. Basri V. Belokurov D. M. Bramich J. M. Carpenter P. Challis K. R. Covey R. M. Cutri N. W. Evans M. Fellhauer A. Garg G. Gilmore P. Hewett P. Plavchan D. P. Schneider C. L. Slesnick S. Vidrih L. M. Walkowicz D. B. Zucker 《Monthly notices of the Royal Astronomical Society》2008,386(1):416-424
We report on Two-Micron All-Sky Survey (2MASS) J01542930+0053266, a faint eclipsing system composed of two M dwarfs. The variability of this system was originally discovered during a pilot study of the 2MASS Calibration Point Source Working Data base. Additional photometry from the Sloan Digital Sky Survey yields an eight-passband light curve from which we derive an orbital period of 2.639 0157 ± 0.000 0016 d. Spectroscopic followup confirms our photometric classification of the system, which is likely composed of M0 and M1 dwarfs. Radial velocity measurements allow us to derive the masses (M1 = 0.66 ± 0.03 M⊙ ; M2 = 0.62 ± 0.03 M⊙ ) and radii (R1 = 0.64 ± 0.08 R⊙ ; R2 = 0.61 ± 0.09 R⊙ ) of the components, which are consistent with empirical mass–radius relationships for low-mass stars in binary systems. We perform Monte Carlo simulations of the light curves which allow us to uncover complicated degeneracies between the system parameters. Both stars show evidence of Hα emission, something not common in early-type M dwarfs. This suggests that binarity may influence the magnetic activity properties of low-mass stars; activity in the binary may persist long after the dynamos in their isolated counterparts have decayed, yielding a new potential foreground of flaring activity for next generation variability surveys. 相似文献
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P. A. Conlon P. T. Gallagher R. T. J. McAteer J. Ireland C. A. Young P. Kestener R. J. Hewett K. Maguire 《Solar physics》2008,248(2):297-309
Magnetohydrodynamic turbulence is thought to be responsible for producing complex, multiscale magnetic field distributions
in solar active regions. Here we explore the multiscale properties of a number of evolving active regions using magnetograms
from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The multifractal spectrum was obtained by using a modified box-counting method to study the relationship between
magnetic-field multifractality and region evolution and activity. The initial emergence of each active region was found to
be accompanied by characteristic changes in the multifractal spectrum. Specifically, the range of multifractal structures
(D
div) was found to increase during emergence, as was their significance or support (C
div). Following this, a decrease in the range in multifractal structures occurred as the regions evolved to become large-scale,
coherent structures. From the small sample considered, evidence was found for a direct relationship between the multifractal
properties of the flaring regions and their flaring rate. 相似文献
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We present K -band imaging of fields around 30 strong Ca ii absorption-line systems, at 0.7 < z < 1.2 , three of which are confirmed damped Lyman α systems. A significant excess of galaxies is found within 6.0 arcsec (≃50 kpc) from the absorber line of sight. The excess galaxies are preferentially luminous compared to the population of field galaxies. A model in which field galaxies possess a luminosity-dependent cross-section for Ca ii absorption of the form ( L / L *)0.7 reproduces the observations well. The luminosity-dependent cross-section for the Ca ii absorbers appears to be significantly stronger than the established ( L / L *)0.4 dependence for Mg ii absorbers. The associated galaxies lie at large physical distances from the Ca ii -absorbing gas; we find a mean impact parameter of 24 kpc ( H 0 = 70 km s−1 Mpc−1 ) . Combined with the observed number density of Ca ii absorbers the large physical separations result in an inferred filling factor of only ∼10 per cent. The physical origin of the strong Ca ii absorption remains unclear, possible explanations vary from very extended discs of the luminous galaxies to associated dwarf galaxy neighbours, remnants of outflows from the luminous galaxies, or tidal debris from cannibalism of smaller galaxies. 相似文献
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Nikhil Padmanabhan Tamás Budavári David J. Schlegel Terry Bridges Jonathan Brinkmann Russell Cannon rew J. Connolly Scott M. Croom István Csabai Michael Drinkwater Daniel J. Eisenstein Paul C. Hewett Jon Loveday Robert C. Nichol Kevin A. Pimbblet Roberto De Propris Donald P. Schneider Ryan Scranton Uro Seljak Tom Shanks István Szapudi Alexander S. Szalay David Wake 《Monthly notices of the Royal Astronomical Society》2005,359(1):237-250