High‐resolution simulations and visualization of protoplanetary disks: structure of the flow in the vicinity of a massive planet     

P. Cieciela&#x;g  T. Plewa  M. Ryczka 《Astronomische Nachrichten》2000,321(3):171-174

A problem of mass flow in the immediate vicinity of a planet embedded in a protoplanetary disk is studied numerically in two dimensions. Large differences in temporal and spatial scales involved suggest that a specialized discretization method for solution of hydrodynamical equations may offer great savings in computational resources, and can make extensive parameter studies feasible. Preliminary results obtained with help of Adaptive Mesh Refinement technique and high‐order explicit Eulerian solver are presented. This combination of numerical techniques appears to be an excellent tool which allows for direct simulations of mass flow in vicinity of the accretor at moderate computational cost. The present communication is focused on the structure of the outer part of the circumplanetary disk. We employ the multifluid option to the hydrodynamical solver to prove that the circumplanetary disk is composed of the gas transfered into it from the edges of the gap.  相似文献   

Search for circum‐planetary material and orbital period variations of short‐period Kepler exoplanet candidates     

Z. Garai  G. Zhou  J. Budaj  R.F. Stellingwerf 《Astronomische Nachrichten》2014,335(10):1018-1036

A unique short‐period (P = 0.65356(1) d) Mercury‐size Kepler exoplanet candidate KIC012557548b has been discovered recently by Rappaport et al. (2012). This object is a transiting disintegrating exoplanet with a circum‐planetary material–comet‐like tail. Close‐in exoplanets, like KIC012557548b, are subjected to the greatest planet‐star interactions. This interaction may have various forms. In certain cases it may cause formation of the comet‐like tail. Strong interaction with the host star, and/or presence of an additional planet may lead to variations in the orbital period of the planet. Our main aim is to search for comet‐like tails similar to KIC012557548b and for long‐term orbital period variations. We are curious about frequency of comet‐like tail formation among short‐period Kepler exoplanet candidates. We concentrate on a sample of 20 close‐in candidates with a period similar to KIC012557548b from the Kepler mission. We first improved the preliminary orbital periods and obtained the transit light curves. Subsequently we searched for the signatures of a circum‐planetary material in these light curves. For this purpose the final transit light curve of each planet was fitted with a theoretical light curve, and the residuals were examined for abnormalities. We then searched for possible long‐term changes of the orbital periods using the method of phase dispersion minimization. In 8 cases out of 20 we found some interesting peculiarities, but none of the exoplanet candidates showed signs of a comet‐like tail. It seems that the frequency of comet‐like tail formation among short‐period Kepler exoplanet candidates is very low. We searched for comet‐like tails based on the period criterion. Based on our results we can conclude that the short‐period criterion is not enough to cause comet‐like tail formation. This result is in agreement with the theory of the thermal wind and planet evaporation (Perez‐Becker & Chiang 2013). We also found 3 cases of candidates which showed some changes of the orbital period. Based on our results we can see that orbital period changes are not caused by comet‐like tail disintegration processes, but rather by possible massive outer companions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Spectroscopic verification of suspected planetary nebulae. IV.     

L. Kohoutek  R. Pauls 《Astronomische Nachrichten》2001,322(3):171-178

Verification of 7 objects as PNe (Table 1/A) as well as misclassification of 5 objects as PNe (Table 1/C) are discussed according to our CCD spectra; the status of 4 objects (Table 1/B) remains uncertain. In Table we give the estimates of line‐strengths and the measured intensities of emission lines as well as the derived hel. radial velocities and their standard deviations.  相似文献   

Spectroscopic verification of suspected planetary nebulae. III.     

L. Kohoutek  R. Pauls 《Astronomische Nachrichten》1994,315(6):409-412

Classification of eight objects as planetary nebulae (Table I/A) was confirmed according to our image tube spectra; as to further two objects (Table 1/B) their status remains unclear. In Table 2 we give estimates of line-strengths, derived heliocentric radial velocities and their standard deviations.  相似文献