On the Red Edge of the δ Scuti Instability Strip

The S Scuti star catalogue is used to derive the observational locations of such stars on the HR diagram. The theoretical and observational instability strips are compared to check the theoretical red edge obtained by considering nonlocal time-dependent convection theory. The observational instability strip almost overlaps with the theoretical one, but the observed blue and red envelopes are hotter than the theoretical edges. The distribution of S Scuti stars in the pulsation strip is not uniform.     

Statistics of the Instability Strip of β Cephei Stars

We present a study of the β Cephei instability strip based on a sample of 49 stars of this type.After deriving their effective temperatures and luminosities from their observed(B-V),(U-B) colors and parallaxes we find their positions in the HR diagram to be mostly confined to the main sequence,and their masses to lie between 7 M and 30 M.Their distribution on the HR diagram matches well with our previous theoretical instability strip which has an upper bound in the luminosity and rather tight boundaries in the effective temperature.     

On the Large-Scale Structure of the Universe as given by the Voronoi Diagrams

The size distributions of 2D and 3D Voronoi cells and of cells of Vp(2,3),-2D cut of 3D Voronoi diagram-are explored, with the single-parameter (re-scaled) gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp(2,3) map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.     

Time-dependent Behaviour of the Low Amplitude δ Scuti Star HD 52788

Wavelet transform is applied to reanalyze the low amplitude δ Scuti star HD 52788, which exhibits complex light variations with uncertain frequency solutions. We gain an insight into the strong instability of pulsation present in the star. Based on an estimate of the star‘s physical parameters, its evolutionary status is determined. An attempt of asteroseismic modelling failed to predict the observed dense frequencies. Because of its varying pulsation spectrum, HD 52788 is a distinctive and very interesting object among δ Sct stars for testing current models of stellar evolution and pulsation.     

Pulsation analysis of the high amplitude δ Scuti star CW Serpentis

Time-series photometric observations were made for the high amplitudeδScuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories,Chinese Academy of Sciences.After performing the frequency analysis of the light curves,we confirmed the fundamental frequency of f=5.28677 c d 1,together with seven harmonics of the fundamental frequency,which are newly detected.No additional frequencies were detected.The O C diagram,produced with the 21 newly determined times of maximum light combined with those provided in the literature,helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355±0.000000003 d.     

On the Geometry of Broad-Line Regions in BL Lac Objects

The geometry of broad-line regions (BLRs) in active galactic nuclei (AGNs) is still controversial. We use a sample of BL Lac objects, of which the black hole masses Mbh are estimated from their host galaxy absolute magnitude at R-band, MR, by using the empirical relation between MR and black hole mass Mbh. The sizes of the broad-line regions for Mgn are derived from the widths of Mgn lines and the black hole masses. Compared with the empirical relation between BLR size RBLR and MgII line luminosity LMgII, it is found the BLR sizes in the BL Lac objects derived in this paper are 2-3 orders of magnitude higher. If the BLR geometry of these sources is disklike, then the viewing angle between the axis and the line of sight is in the range of ~ 2°-15°, which is consistent with the unification scheme.     

On the Correlation between Radio Properties and Black Hole Mass of Quasars

The question whether the radio properties of quasars are related to the mass of the central black hole or the accretion rate is important for our understanding of the formation of relativistic jets, but no consensus has been reached from statistical analyses. Using two large quasar samples, one radio-selected, one optical-selected, we re-exarnined these relations and find that previous differences between radio- and optical- selected samples can be ascribed, at least partly, to the effect of the narrow line component. All previous claimed correlations are much weaker, if exist at all.