Showing papers by "Omer Tamuz published in 2006"
TL;DR: In this article, the authors provided a full orbital solution of the planetary system around mu Ara, which turns out to be the second system known to harbor 4 planetary companions, including a new planet on an almost circular 310 days-period and with a mass of 0.52 M_Jup.
Abstract: The mu Ara planetary system is rather complex: It contains two already known planets, mu Ara b with P=640 days and mu Ara c with P=9.64 days, and a third companion on a wide but still poorly defined orbit. Even with three planets in the system, the data points keep anomalously high dispersion around the fitted solution. The high residuals are only partially due to the strong p-mode oscillations of the host star. We have therefore studied in this paper the possible presence of a fourth planet in the system. During the past years we have carried out additional and extremely precise radial-velocity measurements with the HARPS spectrograph. We provide in this paper a full orbital solution of the planetary system around mu Ara. It turns out to be the second system known to harbor 4 planetary companions. Thanks to the new data points acquired with HARPS we can confirm the presence of mu Ara c at P=9.64 days, which produces a coherent RV signal over more than two years. The new orbital fit sets the mass of mu Ara c to 10.5 M_Earth. Furthermore, we present the discovery of mu Ara d, a new planet on an almost circular 310 days-period and with a mass of 0.52 M_Jup. Finally, we give completely new orbital parameters for the longest-period planet, mu Ara e. It is the first time that this companion is constrained by radial-velocity data into a dynamical stable orbit, which leaves no doubt about its planetary nature. (Abridged).
106 citations
TL;DR: A new algorithm, Eclipsing Binary Automated Solver (EBAS), is presented, designed to analyse light curves of eclipsing binaries, based on the relatively fast EBOP code, and introduces a new 'alarm' goodness-of-fit statistic that takes into account correlation between neighbouring residuals.
Abstract: We present a new algorithm, Eclipsing Binary Automated Solver (EBAS), to analyse light curves of eclipsing binaries. The algorithm is designed to analyse large numbers of light curves, and is therefore based on the relatively fast EBOP code. To facilitate the search for the best solution, EBAS uses two parameter transformations. Instead of the radii of the two stellar components, EBAS uses the sum of radii and their ratio, while the inclination is transformed into the impact parameter. To replace human visual assessment, we introduce a new ‘alarm’ goodness-of-fit statistic that takes into account correlation between neighbouring residuals. We perform extensive tests and simulations that show that our algorithm converges well, finds a good set of parameters and provides reasonable error estimation.
62 citations
TL;DR: The Eclipsing Binary Automated Solver (EBAS) as mentioned in this paper uses the sum of radii and their ratio, while the inclination is transformed into the impact parameter to facilitate the search for the best solution.
Abstract: We present a new algorithm -- Eclipsing Binary Automated Solver (EBAS), to analyse lightcurves of eclipsing binaries. The algorithm is designed to analyse large numbers of lightcurves, and is therefore based on the relatively fast EBOP code. To facilitate the search for the best solution, EBAS uses two parameter transformations. Instead of the radii of the two stellar components, EBAS uses the sum of radii and their ratio, while the inclination is transformed into the impact parameter. To replace human visual assessment, we introduce a new 'alarm' goodness-of-fit statistic that takes into account correlation between neighbouring residuals. We perform extensive tests and simulations that show that our algorithm converges well, finds a good set of parameters and provides reasonable error estimation.
50 citations
TL;DR: In this paper, the authors presented EBAS, a new fully automated algorithm to analyse the light curves of eclipsing binaries, based on the EBOP code, and applied the new algorithm to the whole sample of 2580 binaries found in the Optical Gravitational Lensing Experiment (OGLE) Large Magellanic Cloud (LMC) photometric survey and derive the orbital elements for 1931 systems.
Abstract: In the first paper of this series, we presented EBAS – Eclipsing Binary Automated Solver, a new fully automated algorithm to analyse the light curves of eclipsing binaries, based on the EBOP code. Here, we apply the new algorithm to the whole sample of 2580 binaries found in the Optical Gravitational Lensing Experiment (OGLE) Large Magellanic Cloud (LMC) photometric survey and derive the orbital elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC, we construct a well-defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 d. We also estimate the total number of binaries in the LMC with the same characteristics, and not only the eclipsing binaries, to be about 5000. This figure leads us to suggest that (0.7 ± 0.4) per cent of the main-sequence B-type stars in the LMC are found in binaries with periods shorter than 10 d. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars. On the other hand, the binary frequency found by Hubble Space Telescope (HST) photometric searches within the late main-sequence stars of 47 Tuc is only slightly higher and still consistent with the frequency we deduced for the B stars in the LMC.
42 citations
TL;DR: In this article, the authors presented EBAS, a new fully automated algorithm to analyse the lightcurves of eclipsing binaries, based on the EBOP code, and applied the new algorithm to the whole sample of 2580 binaries found in the OGLE LMC photometric survey and derived the orbital elements for 1931 systems.
Abstract: In the first paper of this series we presented EBAS, a new fully automated algorithm to analyse the lightcurves of eclipsing binaries, based on the EBOP code. Here we apply the new algorithm to the whole sample of 2580 binaries found in the OGLE LMC photometric survey and derive the orbital elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC we construct a well defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 days. We also estimate the total number of binaries in the LMC with the same characteristics, and not only the eclipsing binaries, to be about 5000. This figure leads us to suggest that 0.7 +- 0.4 percent of the main-sequence B-type stars in the LMC are found in binaries with periods shorter than 10 days. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars. On the other hand, the binary frequency found by HST photometric searches within the late main-sequence stars of 47 Tuc is only slightly higher and still consistent with the frequency we deduced for the B stars in the LMC.
36 citations
01 Jan 2006
TL;DR: Sys-Sys-Rem as mentioned in this paper is a detrending algorithm designed to remove systematic effects in a large set of lightcurves obtained by a photometric survey, which works without any prior knowledge of the effects, as long as they appear in many stars of the sample.
Abstract: Sys-Rem (Tamuz, Mazeh & Zucker 2005) is a detrending algorithm designed to remove systematic effects in a large set of lightcurves obtained by a photometric survey. The algorithm works without any prior knowledge of the effects, as long as they appear in many stars of the sample. This paper presents the basic principles of Sys-Rem and discusses a parameterization used to determine the number of effects removed. We assess the performance of Sys-Rem on simulated transits injected into WHAT survey data. This test is proposed as a general scheme to assess the effectiveness of detrending algorithms. Application of Sys-Rem to the OGLE dataset demonstrates the power of the algorithm. We offer a coded implementation of Sys-Rem to the community.
13 citations
TL;DR: In this paper, a photometric follow-up of the recently discovered transiting planet WASP-1b was reported, where the authors used a variant of the EBOP code together with the Sys-Rem detrending approach to fit the light curve.
Abstract: We report on photometric follow-up of the recently discovered transiting planet WASP-1b. We observed two transits with the Wise Observatory 1m telescope, and used a variant of the EBOP code together with the Sys-Rem detrending approach to fit the light curve. Assuming a stellar mass of 1.15 M_sun, we derived a planetary radius of R_p = 1.40 +- 0.06 R_J and mass of M_p = 0.87 +- 0.07 M_J. An uncertainty of 15% in the stellar mass results in an additional systematic uncertainty of 5% in the planetary radius and of 10% in planetary mass. Our observations yielded a slightly better ephemeris for the center of the transit: T_c [HJD] = (2454013.3127 +- 0.0004) + N_tr * (2.51996 +- 0.00002). The new planet is an inflated, low-density planet, similar to HAT-P-1b and HD209458b.
6 citations
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TL;DR: The basic principles of Sys-Rem are presented and a parameterization used to determine the number of effects removed are discussed and a test is proposed as a general scheme to assess the effectiveness of detrending algorithms.
Abstract: Sys-Rem (Tamuz, Mazeh & Zucker 2005) is a detrending algorithm designed to remove systematic effects in a large set of lightcurves obtained by a photometric survey. The algorithm works without any prior knowledge of the effects, as long as they appear in many stars of the sample. This paper presents the basic principles of Sys-Rem and discusses a parameterization used to determine the number of effects removed. We assess the performance of Sys-Rem on simulated transits injected into WHAT survey data. This test is proposed as a general scheme to assess the effectiveness of detrending algorithms. Application of Sys-Rem to the OGLE dataset demonstrates the power of the algorithm. We offer a coded implementation of Sys-Rem to the community.
3 citations
TL;DR: The Eclipsing Binary Automated Solver (EBAS) as discussed by the authors uses a new goodness-of-fit statistic that takes into account correlation between neighbouring residuals to replace human visual assessment.
Abstract: We present a new algorithm, the Eclipsing Binary Automated Solver (EBAS) to analyse lightcurves of eclipsing binaries. To replace human visual assessment, we introduce a new ‘alarm’ goodness-of-fit statistic that takes into account correlation between neighbouring residuals. We apply the new algorithm to the whole sample of 2580 binaries found in the OGLE photometric survey of the LMC and derive the photometric elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC we construct a well defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 days.
2 citations
01 Aug 2006
TL;DR: In this article, the authors used EBAS to fit lightcurves of the OGLE LMC eclipsing binaries, which yielded the period distribution and frequency of all LMC short-period binaries, and not just the eclipsing systems.
Abstract: We review the results of our analysis of the OGLE LMC eclipsing binaries (Mazeh, Tamuz & North 2006), using EBAS -- Eclipsing Binary Automated Solver, an automated algorithm to fit lightcurves of eclipsing binaries (Tamuz, Mazeh & North 2006).
After being corrected for observational selection effects, the set of detected eclipsing binaries yielded the period distribution and the frequency of all LMC short-period binaries, and not just the eclipsing systems.
Somewhat surprisingly, the period distribution is consistent with a flat distribution in log P between 2 and 10 days. The total number of binaries with periods shorter than 10 days in the LMC was estimated to be about 5000. This figure led us to suggest that (0.7 ± 0.4)% of the main-sequence A- and B-type stars are found in binaries with periods shorter than 10 days. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars.
01 Jan 2006
TL;DR: A branch and bound approach to perform an exhaustive scan of the search space and enables detecting modules that are missed by previous approaches and is shown to outperform the state-of-the-art MCODE and to provide results that are more in line with current biological knowledge.
Abstract: Motivation: A major goal of systems biology is the dissection of protein machineries within the cell. The recent availability of genome-scale protein interaction networks provides a key resource for addressing this challenge. Current approaches to the problem are based on devising a scoring scheme for putative protein modules and applying a heuristic search for high-scoring modules. Results: Here we develop a branch and bound approach to perform an exhaustive scan of the search space.We show that such a search is possible and enables detecting modules that are missed by previous approaches. The modules we identify are shown to be signicantly coherent in their functional annotations and expression patterns. Our algorithm, PROMO, is shown to outperform the state-of-the-art MCODE and to provide results that are more in line with current biological knowledge.