Browsing Research Articles (Statistics & Population Studies) by Issue Date
Now showing items 120 of 162

IC and RC band timeseries observations of some bright ultracool dwarfs
(Oxford University Press, 2005)The results of more than 100 h of CCD photometric monitoring of 10 L dwarfs and two T dwarfs are presented. Reasonable evidence is shown for IC band variability in DENIS 0255−4700, DENIS 1705−0516 and 2M 2104−1037. ... 
The analysis of irregularly observed stochastic astronomical timeseries – I. Basics of linear stochastic differential equations
(Oxford University Press, 2005)The theory of loworder linear stochastic differential equations is reviewed. Solutions to these equations give the continuous time analogues of discrete time autoregressive timeseries. Explicit forms for the power ... 
JHKs timeseries observations of a few ultracool dwarfs
(Oxford University Press, 2005)The M8.5 object SSSPM J0109−5101 has recently been shown to be both a periodic and a flaring variable, based on optical observations in the extreme red. More than 16 h of monitoring in the nearinfrared (NIR) reported ... 
Evidence for rapid evolution of periodic variations in an ultracool dwarf
(Oxford University Press, 2006)The results of three short photometric monitoring runs on the L0 dwarf 2MASS J06050196−2342270, during three consecutive nights, are presented. The observations show the persistent presence of a 2.4h period, with an IC ... 
The Nyquist frequency for irregularly spaced timeseries: a calculation formula
(Oxford University Press, 2006)Eyer & Bartholdi showed that the Nyquist frequency of irregularly sampled timeseries can be very high. In this paper, a calculation formula for the Nyquist frequency is presented. In practice there is an upper limit of ... 
Son preference and contraceptive practice among tribal groups in rural South India
(KamlaRaj Enterprises, 2006)This paper examines the son preference and contraceptive practice among tribal groups in rural south India. Parents’ preferences for the sex of their children have constituted an important theme in population and social ... 
Nearinfrared timeseries photometry of six fields in the young open cluster IC 2391
(Oxford University Press, 2006)Fields containing targets of spectral types later than M5 were monitored in JHKs for about 7 h each. None of the targets showed variability at levels exceeding 0.02 (or smaller, in some cases). Seven new variable stars ... 
The analysis of indexed astronomical time series – X. Significance testing of O − C data
(Oxford University Press, 2006)It is assumed that O − C (‘observed minus calculated’) values of periodic variable stars are determined by three processes, namely measurement errors, random cycletocycle jitter in the period, and possibly longterm ... 
Photometry of the magnetic white dwarf SDSS 121209.31+013627.7
(Oxford University Press, 2006)The results of 27 h of time series photometry of SDSS 121209.31+013627.7 are presented. The binary period established from spectroscopy is confirmed and refined to 0.061 412 d (88.43 min). The photometric variations are ... 
A reassessment of the nearest neighbour alignment of the Xray isophotes of galaxy clusters
(Oxford University Press, 2006)Alignment is defined as the tendency of the distribution of pointing angles between the major axes of clusters and their nearest neighbours to be more concentrated towards small values for small nearest neighbour distances, ... 
On the upper limit on stellar masses in the Large Magellanic Cloud cluster R136
(Oxford University Press, 2006)A truncated powerlaw distribution is fitted to the 29 largest stellar masses known in R136. Two different statistical techniques are used, with comparable results. An upper limit to the mass distribution of the order ... 
Fitting sinusoids to observations of rotating spotted stars
(Oxford University Press, 2007)It is assumed that K blocks (e.g. seasons) of observations are available, and the parameters characterizing a fixedfrequency sinusoidal variability (mean light level, amplitude, phase) are constant within each of the ... 
Improved SAAO–2MASS photometry transformations
(Oxford University Press, 2007)Nearinfrared photometry of 599 stars is used to calculate transformations from the South African Astronomical Observatory (SAAO) JHK system to the TwoMicron AllSky Survey (2MASS) JHKS system. Both severalterm formal ... 
HE0230–4323: an unusual pulsating hot subdwarf star
(Oxford University Press, 2007)HE 0230−4323 is a known binary, consisting of a subdwarf star and a companion which is not observable in the optical. Photometric measurements reported in this paper have shown it to be both a reflectioneffect and a ... 
Multivariate comparisons of the period–lightcurve shape distributions of Cepheids in five galaxies
(Oxford University Press, 2007)A number of published tests suitable for the comparison of multivariate distributions are described. The results of a small power study, based on realistic Cepheid log period – Fourier coefficient data, are presented. ... 
KPD 0629–0016, a slowly pulsating hot subdwarf star
(Oxford University Press, 2007)The results of nine CCD photometric observing runs on KPD 0629–0016 are presented. During six of the runs measurements were obtained alternately through B and V filters. Four periodicities, for which there is good agreement ... 
What can be deduced from open cluster metallicity measurements?
(Oxford University Press, 2007)The dependence of [Fe/H] on galactocentric distance, distance from the galactic midplane and age is studied. Both ordinary leastsquares and nonparametric regression in the form of a ‘generalized additive model’ are ... 
Further observations of Hipparcos red stars and standards for UBV(RI)C photometry
(Oxford University Press, 2007)We present homogeneous and standardized UBV(RI)C JHK photometry for over 100 M stars selected from an earlier paper on the basis of apparent photometric constancy. L photometry has been obtained for stars brighter than ... 
The detailed forms of the LMC Cepheid PL and PLC relations
(Oxford University Press, 2007)Possible deviations from linearity of the Large Magellanic Cloud Cepheid period–luminosity (PL) and period–luminosity–colour (PLC) relations are investigated. Two data sets are studied, respectively from the Optical ... 
HE 0230–4323: An unusual pulsating hot subdwarf star
(Oxford University Press, 2007)HE 0230−4323 is a known binary, consisting of a subdwarf star and a companion which is not observable in the optical. Photometric measurements reported in this paper have shown it to be both a reflectioneffect and a ...