Abstract
We propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the ...time-series of the first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude δ Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae stars.
In the analysis of variable stars, the problem of sampling is central. This article focusses on the determination of the Nyquist frequency. It is well defined in the case of regular sampling. ...However, the time series of variable stars observations are generally unevenly sampled. Fourier analysis using the spectral window furnishes some clues about the equivalent Nyquist frequency in the irregular case. Often it is pushed very high, and thus very short periods can be detected. A specific example is shown, drawn from MACHO databases.
The semi-detached eclipsing binary system BP Muscae has been analysed using the Wilson-Devinney program. Light curves have been obtained in the Geneva 7-colour photometric system, and radial velocity ...curves for both components have been measured with the spectrograph Coralie. The physical and orbital parameters have been determined through a self-consistent simultaneous solution of light curves in seven colours and of the radial velocity curves of both components. The absolute elements of the components are, for the primary (mass gainer), $M_1 = 2.40 \pm 0.01~M_{\odot}$, $R_1 = 2.64 \pm 0.01~R_{\odot}$, $M_{\rm bol_1} = 0.66 \pm 0.04$, $T_{\rm eff_1} = 9180 \pm 90$ K, and for the secondary (mass loser), $M_2 = 0.68 \pm 0.01~M_{\odot}$, $R_2 = 3.76~R_{\odot}$, $M_{\rm bol_2} = 2.40 \pm 0.08$, $T_{\rm eff_2} = 5160 \pm 90$ K. The semi-major axis A of the relative orbit is $13.617 \pm 0.019~R_{\odot}$. The spectral type of the components are A0.5/1.5 V (primary) and about G5 III. The distance to BP Mus is evaluated as $562 \pm 17$ pc, and the colour excess EB2-V1 as $0.220 \pm 0.014$.
The semi-detached eclipsing binary system
CF Puppis (
P=7.65 days) has been analysed using the Wilson–Devinney program. Light curves have been obtained in the G
eneva 7-colour photometric system, and ...radial velocity curves for both components have been measured with the cross-correlation technique. The physical and orbital parameters have been determined through a self-consistent simultaneous solution of light curves in seven colours and of the radial velocity curves of both components. The absolute elements of the components are, for the primary (mass gainer),
M
1=1.84±0.04
M
⊙,
R
1=3.06±0.01
R
⊙,
M
bol
1
=1.74±0.02,
T
eff
1
=6671±27 K, and for the secondary (mass loser),
M
2=0.38±0.01
M
⊙,
R
2=5.39
R
⊙,
M
bol
2
=2.51±0.02,
T
eff
2
=4202±17 K. The semi-major axis
A of the relative orbit is 21.28±0.15
R
⊙. The estimated spectral types of the components are about F3 IV (primary) and K2/3 III.
CF Pup has one of the coolest component A among the Algol systems. The equatorial rotational velocities are 24.8 (primary) and 37.0 km s
−1. The secondary is clearly synchronized, and the primary is nearly synchronized (
v
syn=20.2 km s
−1). The distance to
CF Pup is evaluated to 506
±
16 pc, and the colour excess
EB2-V1 to 0.033
±
0.017.
We propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the time-series of the ...first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude delta Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae stars. PUBLICATION ABSTRACT
Intestinal calcium absorption from milk containing lactose (+) and from another containing glucose (-) was studied in eight patients with normal lactase (NL) and seven lactase-deficient (LD) subjects ...to determine if lactase deficiency is implicated in Ca absorption. The results were compared with data obtained from Ca ingestion in a water solution. Ca absorption was measured by a double-isotope technique and the kinetic indices were obtained by a deconvolution method. With (-), Ca absorption was identical in NL and LD subjects and slightly higher than with water solution (15%, NS). With (+), Ca absorption in NL subjects was identical with that from water solution; in LD subjects it increased (23%, p less than 0.02). These data indicate that: Ca is absorbed equally well from milk as from water solution; (+) favors Ca absorption in LD subjects, which suggests that milk ingestion might be encouraged in LD subjects to avoid Ca deficiency; and (-) should be a valuable alternative for lactose-intolerant patients.
Light curves of the semi-detached eclipsing binary system TZ Eridani in the Geneva 7-colour photometric system were analysed using the Wilson-Devinney programme. The physical and orbital parameters ...have been determined through a self-consistent simultaneous solution of the seven light curves and of the radial velocity curves of both components. The following absolute elements of the components are, for the primary (mass gainer), $M_1 = 1.97 \pm 0.06$ $M_{\odot}$, $R_1 = 1.69 \pm$ 0.03 $R_{\odot}$, $M_{\rm bol_1} = 2.36 \pm 0.09$, $T_{\rm eff_1} = 7770 \pm 100$ K, and for the secondary (mass loser), $M_2 = 0.37 \pm 0.01$ $M_{\odot}$, $R_2 = 2.60 \pm 0.04$ $R_{\odot}$, $M_{\rm bol_2} = 3.74 \pm 0.13$, $T_{\rm eff_2} = 4570\ \pm$ 100 K. The semi-major axis A of the relative orbit is $10.57 \pm$ 0.16 $R_{\odot}$. The regular increase of the period is described. The spectral type of the components are A5/6 V (primary) and K0/1 III. The secondary has exhibited a long-term luminosity increase of about 0.06 in V between Dec. 1983 and Dec. 1996. The distance to TZ Eri is evaluated to 270 ± 12 pc.
The ESA Gaia mission will provide a multi-epoch database for a billion of objects, including variable objects that comprise stars, active galactic nuclei and asteroids. We highlight a few of Gaia’s ...properties that will benefit the study of variable objects, and illustrate with two examples the work being done in the preparation of the data processing and object characterization. The first example relates to the analysis of the nearly simultaneous multi-band data of Gaia with the Principal Component Analysis techniques, and the second example concerns the classification of Gaia time series into variability types. The results of the ground-based processing of Gaia’s variable objects data will be made available to the scientific community through the intermediate and final ESA releases throughout the mission.
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