摘要:

AbstractIn order to explore the mechanism of the solar cycle luminosity change observed by the Active Cavity Radiometer Irradiance Monitor (ACRIM) I experiment on board of the spacecraft Solar Maximum Mission, we examined running mean time profiles of the daily ACRIM data from the declining phase of solar cycle 21 to the rising phase of solar cycle 22. By comparing them with those of the daily sunspot number, integrated surface magnetic field flux, integrated He I 10830 Å line equivalent width data, and two kinds of data sets of the daily integrated Ca II K line index as indices of the surface magnetic activities, we found (i) that the running mean time profiles of the six independent data sets have several peaks and valleys in common in one solar cycle with time intervals on the order of a few hundreds of days, and (ii) that the peaks and valleys of the ACRIM data profiles followed the peaks and valleys of all the other five indices of the surface activities by 40 to 60 days. This time delay phenomenon suggests (i) that the luminosity modulation was not directly caused by dark and bright features of the surface magnetic activities that the other five indices represent, and (ii) that the missing sunspot radiative flux which was blocked by sub‐surface magnetic flux tubes of sunspots and sunspot groups should be re‐radiated 40 to 60 days after the surface emergence of the magnetic flux tubes. The concept of the time delay resolves the enigma of the missing sunspot radiative flux and the enigma of the ACRIM experiment that the luminosity dropped when a sunspot or a sunspot group appeared on the surface while the yearly mean of the luminosity decreased and increased along with the decrease and increase of the yearly sunspot number of the 11‐year solar cycle. A model of the mechanism to understand these phenomena is presented and its application to other stars is sug

ISSN:0004-6337    

DOI:10.1002/asna.2103150302

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2103150303

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe present a new numerical method for solving the system of partial differential equations describing the structure and evolution of a spherically symmetric star. As usual, we employ the transversal method of lines in order to split the equations into a coupled spatial and temporal part. The novel features of the algorithm are the following: (a) Instead of using the Lagrangian picture we formulate the system of partial differential equations in the Eulerian picture. (b) We reformulate the equations of stellar structure as a multipoint boundary‐value problem. By means of this reformulation the rather clumsy iterative matching procedure of stellar atmosphere and interior is avoided. (c) The multipoint boundary‐value problem is solved by the multiple shooting method. This approach not only ensures a high accuracy of the stellar models calculated at each time step but also allows the free boundaries inside the star due to different energy transport mechanisms to be located exactly. (d) The time derivatives involved in the stellar‐structure equations are discretized implicitly to second order accuracy. Moreover, at each time step, the chemical abundances are determined by using a sophisticated update procedure. In this way, a high accuracy is achieved with respect to the integration in time.The algorithm has turned out to be exceedingly reliable and numerically accurate. This is shown by the evolution of a 1M⊙star up to the hydrogen‐shell burning phase. In this example, the virial theorem, the law of mass conservation, and the law of energy conservation is fulfilled to a hitherto unattainable degree of accuracy.Since the multiple shooting method, which is at the heart of our approach, is a perfect example of a parallel algorithm, the computational speed of the algorithm might be substantially improved provided easy‐to‐program, high‐performance parallel computers with sufficiently many processors become available in

ISSN:0004-6337    

DOI:10.1002/asna.2103150304

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the first part of this study of PN towards the galactic centre we present the discovery of 24 new planetary nebulae found on the objective‐prism spectra in three ESO fields (Table 1 ‐ parameters of the survey, Tables 3 and 4 ‐ new objects). The observations of those objects are listed in Table 5. Besides, we give the classification and the positions of known objects in this area (Tab

ISSN:0004-6337    

DOI:10.1002/asna.2103150305

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA nearby group of galaxies, centered at the spiral galaxy NGC 972 and conspicuously rich in faint dwarf spheroidal galaxies, has been investigated photometrically on theBandVplates, obtained with the Tautenburg 2m Schmidt telescope. For ten certain and probable group members the equivalentBandVbrightness profiles have been extracted. Integrated magnitudes and mean colours of faint group members have been estimated. Typically, the dwarfs show a “subexponential” (i.e. a convex curvature over the linear radius) surface brightness profile and often a central excess. Their equivalent profiles are reasonably well fitted by modified isothermal (King) mod

ISSN:0004-6337    

DOI:10.1002/asna.2103150306

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2103150307

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractPhotoelectricubvyHαHβ observations of the Herbig Ae/Be star BD+61°154 are presented. The observational data are analyzed proceeding from the simple hypothesis that the light variation is mainly due to temperature changes of gaseous envelo

ISSN:0004-6337    

DOI:10.1002/asna.2103150308

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

Abstract13 objects, motly with UV excess, in a field of about 10 square degrees in the surroundings of the Triangulum galaxy were investigated and classified, using photometric, spectroscopic, and proper motion data. 9 of them are probable quasistellar objects, 3 cataclysmic variables, and 1 eclipsing binary.Die Arbeit enthält für 13 veränderliche Objekte, überwiegend mit UV‐Überschuß, die Ergebnisse der Klassifizierung auf Grund von photometrischen, spektroskopischen und Eigenbewegungs‐aten in einem etwa 10 Quadratgrad großen Feld in der weiteren Umgebung von M33. Unter diesen Objekten sind 9 vermutlich quasistellare Objekte, 3 kataklysmische Doppelsterne und ein Bedec

ISSN:0004-6337    

DOI:10.1002/asna.2103150309

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2103150310

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0004-6337    

DOI:10.1002/asna.2103150301

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY