arXiv subjects

Tsevi Mazeh

Publications and source records attributed to Tsevi Mazeh.

At least 127 records · Page 7Linked to original sources

arXiv2008

The Transit Light Curve Project. VIII. Six Occultations of the Exoplanet TrES-3

We present photometry of the exoplanet host star TrES-3 spanning six occultations (secondary eclipses) of its giant planet. No flux decrements were detected, leading to 99%-confidence upper limits on the planet-to-star flux ratio of 0.00024, 0.0005, and 0.00086 in the i, z, and R bands respectively. The corresponding upper limits on the planet's geometric albedo are 0.30, 0.62, and 1.07. The upper limit in the i band rules out the presence of highly reflective clouds, and is only a factor of 2-3 above the predicted level of thermal radiation from the planet.

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arXiv2007

Observational Evidence for Tidal Interaction in Close Binary Systems

This paper reviews the rich corpus of observational evidence for tidal effects in short-period binaries. We review the evidence for ellipsoidal variability and for the observational manifestation of apsidal motion in eclipsing binaries. Among the long-term effects, circularization was studied the most, and a transition period between circular and eccentric orbits has been derived for eight coeval samples of binaries. As binaries are supposed to reach synchronization before circularization, one can expect finding eccentric binaries in pseudo-synchronization state, the evidence for which is reviewed. The paper reviews the Rossiter-McLaughlin effect and its potential to study spin-orbit alignment. We discuss the tidal interaction in close binaries that are orbited by a third distant companion, and review the effect of pumping the binary eccentricity by the third star. We then discuss the idea that the tidal interaction induced by the eccentricity modulation can shrink the binary separation. The paper discusses the extrasolar planets and the observational evidence for tidal interaction with their parent stars which can induce radial drift of short-period planets and circularization of planetary orbits. The paper reviews the revolution of the study of binaries that is currently taking place, driven by large-scaled photometric surveys that are detecting many thousands of new binaries and tens of extrasolar planets. In particular, we review several studies that have been used already thousands of lightcurves of eclipsing binaries to study tidal circularization of early-type stars in the LMC.

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arXiv2007

Supplementary Information for "A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33"

This Supplementary Information provides details about the spectral extraction (crowding issues and the removal of nebular lines), a discussion about the distance to M33, a model for the O-star wind and the measurement of the true photospheric X-ray eclipse width Theta, and details about ellipsoidal modelling. It also contains five related figures, one related table, and additional references.

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arXiv2007

A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33

Stellar-mass black holes are discovered in X-ray emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses >10 solar masses, which is consistent with the fact that the most massive stellar black holes known so all have masses within 1 sigma of 10 solar masses. Here we report a mass of 15.65 +/- 1.45 solar masses for the black hole in the recently discovered system M33 X-7, which is located in the nearby galaxy Messier 33 (M33) and is the only known black hole that is in an eclipsing binary. In order to produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45 day orbit about its 70.0 +/- 6.9 solar mass companion, there must have been a ``common envelope'' phase of evolution in which a significant amount of mass was lost from the system. We find the common envelope phase could not have occured in M33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.

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arXiv2007

Chandra ACIS Survey of M33 (ChASeM33): A First Look

We present an overview of the Chandra ACIS Survey of M33 (ChASeM33): A Deep Survey of the Nearest Face-on Spiral Galaxy. The 1.4 Ms survey covers the galaxy out to $R \approx 18\arcmin (\approx 4$ kpc). These data provide the most intensive, high spatial resolution assessment of the X-ray source populations available for the confused inner regions of M33. Mosaic images of the ChASeM33 observations show several hundred individual X-ray sources as well as soft diffuse emission from the hot interstellar medium. Bright, extended emission surrounds the nucleus and is also seen from the giant \hii regions NGC 604 and IC 131. Fainter extended emission and numerous individual sources appear to trace the inner spiral structure. The initial source catalog, arising from $\sim$~2/3 of the expected survey data, includes 394 sources significant at the $3σ$ confidence level or greater, down to a limiting luminosity (absorbed) of $\sim$1.6\ergs{35} (0.35 -- 8.0 keV). The hardness ratios of the sources separate those with soft, thermal spectra such as supernova remnants from those with hard, non-thermal spectra such as X-ray binaries and background active galactic nuclei. Emission extended beyond the Chandra point spread function is evident in 23 of the 394 sources. Cross-correlation of the ChASeM33 sources against previous catalogs of X-ray sources in M33 results in matches for the vast majority of the brighter sources and shows 28 ChASeM33 sources within 10\arcsec of supernova remnants identified by prior optical and radio searches. This brings the total number of such associations to 31 out of 100 known supernova remnants in M33.

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arXiv2007

The Transit Light Curve Project. VII. The Not-So-Bloated Exoplanet HAT-P-1b

We present photometry of the G0 star HAT-P-1 during six transits of its close-in giant planet, and we refine the estimates of the system parameters. Relative to Jupiter's properties, HAT-P-1b is 1.20 +/- 0.05 times larger and its surface gravity is 2.7 +/- 0.2 times weaker. Although it remains the case that HAT-P-1b is among the least dense of the known sample of transiting exoplanets, its properties are in accord with previously published models of strongly irradiated, coreless, solar-composition giant planets. The times of the transits have a typical accuracy of 1 min and do not depart significantly from a constant period.

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arXiv2007

Beaming Binaries - a New Observational Category of Photometric Binary Stars

The new photometric space-borne survey missions CoRoT and Kepler will be able to detect minute flux variations in binary stars due to relativistic beaming caused by the line-of-sight motion of their components. In all but very short period binaries (P>10d), these variations will dominate over the ellipsoidal and reflection periodic variability. Thus, CoRoT and Kepler will discover a new observational class: photometric beaming binary stars. We examine this new category and the information that the photometric variations can provide. The variations that result from the observatory heliocentric velocity can be used to extract some spectral information even for single stars.

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arXiv2007

The `666' collaboration on OGLE transits: I. Accurate radius of the planets OGLE-TR-10b and OGLE-TR-56b with VLT deconvolution photometry

Transiting planets are essential to study the structure and evolution of extra-solar planets. For that purpose, it is important to measure precisely the radius of these planets. Here we report new high-accuracy photometry of the transits of OGLE-TR-10 and OGLE-TR-56 with VLT/FORS1. One transit of each object was covered in Bessel V and R filters, and treated with the deconvolution-based photometry algorithm DECPHOT, to ensure accurate millimagnitude light curves. Together with earlier spectroscopic measurements, the data imply a radius of 1.22 +0.12-0.07 R_J for OGLE-TR-10b and 1.30 +- 0.05 R_J for OGLE-TR-56b. A re-analysis of the original OGLE photometry resolves an earlier discrepancy about the radius of OGLE-TR-10. The transit of OGLE-TR-56 is almost grazing, so that small systematics in the photometry can cause large changes in the derived radius. Our study confirms both planets as inflated hot Jupiters, with large radii comparable to that of HD 209458$b$ and at least two other recently discovered transiting gas giants.

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arXiv2007

Photometric follow-up of the transiting planet WASP-1b

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.

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arXiv2006

The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733

We present photometry of HD 189733 during eight transits of its close-in giant planet, and out-of-transit photometry spanning two years. Using the transit photometry, we determine the stellar and planetary radii and the photometric ephemeris. Outside of transits, there are quasiperiodic flux variations with a 13.4 day period that we attribute to stellar rotation. In combination with previous results, we derive upper limits on the orbital eccentricity, and on the true angle between the stellar rotation axis and planetary orbit (as opposed to the angle between the projections of those axes on the sky).

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arXiv2006

The Sys-Rem Detrending Algorithm: Implementation and Testing

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.

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arXiv2006

Searching for Variables in One of the WHAT Fields

We present preliminary results on a single field observed by WHAT, a small-aperture short focal length automated telescope with an 8.2 deg x 8.2 deg field of view, located at the Wise Observatory. The system is similar to the members of HATNet (http://cfa-www.harvard.edu/~gbakos/HAT/) and is aimed at searching for transiting extrasolar planets and variable objects. With 5 min integration time, the telescope achieved a precision of a few mmag for the brightest objects. We detect variables with amplitudes less than 0.01 mag. All 152 periodic variables are presented at http://wise-obs.tau.ac.il/~amit/236/ .

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arXiv2006

Photometric Analysis of the Optical Counterpart of the Black Hole HMXB M33 X-7

Aims: Study the high-mass X-ray binary X-7 in M33 using broad-band optical data. Methods: We used recently published CFHT r' and i' data for variable stars in M33 to extract the light curve of the optical counterpart of X-7. We combined these data with DIRECT B and V measurements in order to search for an independent optical modulation with the X-ray periodicity. The periodic modulation is modelled with the ellipsoidal effect. We used UBVRr'i' magnitudes of the system to constrain the temperature and radius of the optical component. Results: The optical data revealed a periodicity of 3.4530 +- 0.0014 days, which is consistent with the known X-ray period. Double modulation, which we attributed to ellipsoidal modulation, is clearly seen in four different optical bands. The absolute magnitude in six optical bands is most consistent with a stellar counterpart with 33000 < T_{eff} < 47000 K and 15 < R < 20 R_{\sun}. We modelled the optical periodic modulation and derived the masses of the two components as a function of the orbital inclination and the radius of the stellar component. The resulting mass range for the compact object is 1.3 < M < 23 M_{\sun}. Conclusions: The system is probably a black hole HMXB, similar to Cyg X-1, LMC X-1 and LMC X-3.

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arXiv2006

Analysis of the eclipsing binaries in the LMC discovered by OGLE: Period distribution and frequency of the short-period binaries

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.

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arXiv2006

TIRAVEL - Template Independent RAdial VELocity measurement

We propose a new approach to measure differential radial velocities, mainly for single-lined spectroscopic binaries. The proposed procedure - TIRAVEL (Template Independent RAdial VELocities) - does not rely on a prior theoretical or observed template, but instead looks for a set of relative Doppler shifts that simultaneously optimizes the alignment of all the observed spectra. We suggest a simple measure to quantify this overall alignment and use its maximum to measure the relative radial velocities. As a demonstration, we apply TIRAVEL to the observed spectra of three known spectroscopic binaries, and show that in two cases TIRAVEL performs as good as the commonly used approach, while in one case TIRAVEL yielded a better orbital solution.

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arXiv2006

Long-Term V-Band Monitoring of the Bright Stars of M33 at the Wise Observatory

We have conducted a long-term V-band photometric monitoring of M33 on 95 nights during four observing seasons (2000 - 2003). A total number of 6418 lightcurves of bright objects in the range of 14 - 21 mag have been obtained. All measurements are publicly available. A total of 127 new variables were detected, of which 28 are periodic. Ten previously known non-periodic variables were identified as periodic, 3 of which are Cepheids, and another previously known periodic variable was identified as an eclipsing binary. Our derived periods range from 2.11 to almost 300 days. For 50 variables we have combined our observations with those of the DIRECT project, obtaining lightcurves of up to 500 measurements, with a time-span of ~7 years. We have detected a few interesting variables, including a 99.3 day periodic variable with a 0.04 mag amplitude, at the position of SNR 19.

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arXiv2006

Automated analysis of eclipsing binary lightcurves. I. EBAS -- a new Eclipsing Binary Automated Solver with EBOP

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.

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arXiv2006

Automated analysis of eclipsing binary lightcurves with EBAS. II. Statistical analysis of OGLE LMC eclipsing binaries

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.

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