Quantitative Morphology Of C/1995 O1 (Hale–Bopp) In February – April 1997     

Vanscheidt  R.  Bleul  H.  Manthey  E.  Jütte  M.  Pohlen  M.  Schmidtobreick  L.  Altmann  M.  Dieball  A.  Geffert  M.  Sanner  J.  Notni  P.  Schmoll  J. 《Earth, Moon, and Planets》1998,81(3):223-231

Extensive widefield CCD direct imaging of C/1995 O1 (Hale-Bopp) at UBVRI was carried out at Hoher List Observatory with the 1.06 m telescope (field of view 20′ × 20′) and at Potsdam Observatory with the 0.70 m telescope (field of view 8′ × 8′). The corresponding spatial resolution is 850–1000 km pix^-1and 525–590 km pix^-1, respectively. The data covers 25 nights from February 20 to April 21, 1997. In order to quantify the various features in the apparent inner coma we introduce a new tomographic method that minimizes the morphological bias caused by image processing. The tomographic analysis leads to quantitative maps refering to the position and intensity of the dust ejections for each image frame. Variability and periodicity within the inner coma can be thoroughly deduced due to various sets of consecutive nights in the observation period mentioned above. The results are compared with applications of adaptive Laplace filtering. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

On the three-dimensional structure of edge-on disc galaxies     

Michael Pohlen  Saleem Zaroubi  Reynier F. Peletier  Ralf-Jürgen Dettmar 《Monthly notices of the Royal Astronomical Society》2007,378(2):594-616

  相似文献   

Canonical Floquet theory     

William E. Wiesel  David J. Pohlen 《Celestial Mechanics and Dynamical Astronomy》1994,58(1):81-96

Classical Floquet theory is reviewed with careful attention to the case of repeated eigenvalues common in Hamiltonian systems. Floquet theory generates a canonical transformation to modal variables if the periodic matrix can be made symplectic at the initial time. It is shown that this symplectic normalization can always be carried out, again with careful attention to the degenerate case. The periodic modal vectors and canonical modal variables can always be chosen to be purely real. It is possible to introduce real valued action-angle variables for all modes. Physical interpretation of the canonical degenerate normal modal variables are offered. Finally, it is shown that this transformation enables canonical perturbation theory to be carried out using Floquet modal variables.  相似文献   

Comparing peanut-shaped `bulges' to N-body simulations and orbital calculations     

G. Aronica  E. Athanassoula  M. Bureau  A. Bosma  R.-J. Dettmar  D. Vergani  M. Pohlen 《Astrophysics and Space Science》2003,284(2):753-756

We present a near-infrared K _n-band photometric study of edge-on galaxies with a box/ peanut-shaped `bulge'. The morphology of the galaxies is analysed using unsharp masking and fits to the vertical surface brightness profiles, and the results are compared to N-body simulations and orbital calculations of barred galaxies. Both theoretical approaches reproduce the main structures observed. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献