Statistics and Population Studies: Recent submissions
Now showing items 141-160 of 162
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Time series photometry of the nearby brown dwarf DENIS-P J0041353-562112
(Oxford University Press, 2011)DENIS-P J0041353−562112 is a brown dwarf, with a spectral type of M7.5, which may be younger than 20 Myr. On the basis of its Hα emission-line asymmetry, it has been suggested that the object is accreting material. If ... -
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 ... -
IC and RC band time-series 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. ... -
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 fixed-frequency sinusoidal variability (mean light level, amplitude, phase) are constant within each of the ... -
Two new variable sdB stars, HE 0218−3437 and LB 1516
(Oxford University Press, 2010)We present photometry which shows that two known hot subdwarf stars, HE 0218−3437 and LB 1516, are variable. LB 1516 exhibits several frequencies in the range 12–25 cycles d−1 (periods of about 1–2 h) with amplitudes ... -
Confidence intervals for the correlation between the gamma-ray burst peak energy and the associated supernova peak brightness
(Oxford University Press, 2009)A strong correlation between the gamma-ray burster peak energy and the peak luminosity of the associated supernova was discovered by Li for four GRBs. Despite the fact that the formal significance level of the correlation ... -
PG 0907+123 and JL 194: slowly pulsating hot subdwarf stars
(Oxford University Press, 2010)Multicolour time-series photometry of two newly discovered slowly pulsating sdB stars (V1093 Her stars, also known as PG 1716 stars) is described. Both stars are fairly bright and appear, from the limited amount of data, ... -
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 2.4-h period, with an IC ... -
On the upper limit on stellar masses in the Large Magellanic Cloud cluster R136
(Oxford University Press, 2006)A truncated power-law 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 ... -
Multicolour time series photometry of 2MASS 1207−3932
(Oxford University Press, 2008)Time series photometry in VRI of the young brown dwarf Two-Micron All-Sky Survey (2MASS) J1207334−393254 is presented. Variability in I is insignificant, but amplitudes up to ∼0.2 mag in R, and ∼0.55 mag in V, are seen ... -
JHKs time-series 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 near-infrared (NIR) reported ... -
The Nyquist frequency for irregularly spaced time-series: a calculation formula
(Oxford University Press, 2006)Eyer & Bartholdi showed that the Nyquist frequency of irregularly sampled time-series can be very high. In this paper, a calculation formula for the Nyquist frequency is presented. In practice there is an upper limit of ... -
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 ... -
On multiple classes of gamma-ray bursts, as deduced from autocorrelation functions or bivariate duration/hardness ratio distributions
(Oxford University Press, 2012)Autocorrelation functions (ACFs) of 119 gamma-ray bursts (GRBs) monitored by the Burst Alert Telescope (BAT) on Swift are calculated. Contrasting with previous results for smaller numbers of bursts from other missions, ... -
Correcting CCD photometry of stars for seeing effects
(Oxford Univeristy Press, 2009)Systematic variability in stellarmagnitudes, as derived from profile fitting to CCD images,may in some instances be due to variable seeing. It is suggested that this happens in cases where the stars are unresolved pairs, ... -
Near-infrared time-series 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 ... -
Predicting gamma-ray burster redshifts from their prompt emission properties
(Oxford University Press, 2010)This paper presents a study of the relation between gamma-ray burster redshift and several of its prompt emission properties (spectral lag, light curve variability, peak energy, rise time and the peak bolometric flux ... -
Statistical tests for changes in the amplitude, frequency or phase of a sinusoidal variation
(Oxford University Press, 2009)The problem considered is that of testing for small changes over time in the properties of a sinusoidal signal contaminated by noise. Two test statistics are proposed. The first is a frequency domain statistic based on ... -
Two large amplitude slowly pulsating hot subdwarf stars
(Oxford University Press, 2011)The discovery observations of two new slowly pulsating subdwarf B stars (V1093 Her stars), BPS CS22890−74 and PB 7032, are presented. Both stars are highly multiperiodic, and have – for V1093 Her stars – large amplitudes. ... -
On the nature of the variable star UNSW-V-760
(Oxford University Press, 2011)The results of multicolour photometric monitoring over several nights of the probable X-ray source UNSW-V-760 are presented. Drawing on both present and past observations, it is shown that the star is multiperiodic and ...