478 research outputs found
An intriguing correlation between the masses and periods of the transiting planets
No full textWe point out an intriguing relation between the masses of the transiting planets and their orbital periods. For the six currently known transiting planets, the data are consistent with a decreasing linear relation. The other known short-period planets, discovered through radial-velocity techniques, seem to agree with this relation. We briefly speculate about a tentative physical model to explain such a dependence. Key words: planetary systems. 1 I N T RO D U C T I O N The actual masses of most extrasolar planets are not known. Because radial-velocity data do not yield orbital inclinations, only minimum masses can be derived for those planets. Some information about the masses could be gained through Hipparcos astrometry (Pourbaix & Arenou 2001; Zucker & Mazeh 2001), but no definite masses. So far, the actual masses can be derived only for planets that exhibit transits, indicating orbital inclinations close to 90◦. The first transiting plane
A search for wide visual companions of exoplanet host stars: The Calar Alto Survey
No full textWe have carried out a search for co-moving stellar and substellar companions around 18 exoplanet host stars with the infrared camera MAGIC at the 2.2 in Calar Alto telescope, by comparing our images with images from the all sky surveys 2MASS, POSS I and II. Four stars of the sample namely HD 80606, 55 Cnc, HD 46375 and BD- 10 degrees 3166, are listed as binaries in the Washington Visual Double Star Catalogue (WDS). The binary nature of HD 80606, 55 Cnc, and HD 46375 is confirmed with both astrometry as well as photometry, thereby the proper motion of the companion of HD 46375 was determined here for the first time. We derived the companion masses as well as the longterm stability regions for additional companions in these three binary systems. We can rule out further stellar companions around all stars in the sample with projected separations between 270 AU and 2500 AU, being sensitive to substellar companions with masses down to similar to 60 M-Jup (S/N = 3). Furthermore we present evidence that the two components of the WDS binary BD- 10 degrees 3166 are unrelated stars, i.e this system is a visual pair. The spectrophotometric distance of the primary (a KO dwarf) is similar to 67 pc, whereas the presumable secondary BD- 10 degrees 3166 B (a M4 to M5 dwarf) is located at a distance of 13 pc in the foreground. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators
No full textWe present a large sample of stellar rotation periods for Kepler Objects of Interest (KOIs), based on three years of public Kepler data. These were measured by detecting periodic photometric modulation caused by star spots, using an algorithm based on the autocorrelation function (ACF) of the light curve, developed recently by McQuillan, Aigrain and Mazeh (2013). Of the 1919 main-sequence exoplanet hosts analyzed, robust rotation periods were detected for 737. Comparing the detected stellar periods to the orbital periods of the innermost planet in each system reveals a notable lack of close-in planets around rapid rotators. It appears that only slowly spinning stars, with rotation periods longer than 5-10 days, host planets on orbits shorter than 3 days, although the mechanism(s) that lead(s) to this is not clear
The Sys-Rem Detrending Algorithm: Implementation and Testing
No full textSys-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
Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
No full textWe analyzed 3 years of data from the Kepler space mission to derive rotation periods of main-sequence stars below 6500 K. Our automated autocorrelation-based method detected rotation periods between 0.2 and 70 days for 34,030 (25.6%) of the 133,030 main-sequence Kepler targets (excluding known eclipsing binaries and Kepler Objects of Interest), making this the largest sample of stellar rotation periods to date. In this paper we consider the detailed features of the now well-populated period-temperature distribution and demonstrate that the period bimodality, first seen by McQuillan, Aigrain and Mazeh (2013) in the M-dwarf sample, persists to higher masses, becoming less visible above 0.6 M_sun. We show that these results are globally consistent with the existing ground-based rotation-period data and find that the upper envelope of the period distribution is broadly consistent with a gyrochronological age of 4.5 Gyrs, based on the isochrones of Barnes (2007), Mamajek and Hillenbrand (2008) and Meibom et al. (2009). We also performed a detailed comparison of our results to those of Reinhold et al. (2013) and Nielsen et al. (2013), who have measured rotation periods of field stars observed by Kepler. We examined the amplitude of periodic variability for the stars with detected rotation periods, and found a typical range between ~950 ppm (5th percentile) and ~22,700 ppm (95th percentile), with a median of ~5,600 ppm. We found typically higher amplitudes for shorter periods and lower effective temperatures, with an excess of low-amplitude stars above ~5400 K
VizieR Online Data Catalog: Accurate SB2 radial velocities (Kiefer+, 2018)
No full textVizieR On-line Data Catalog: J/MNRAS/474/731. Originally published in: 2018MNRAS.474..731KThe observations were performed at the T193 telescope of the Haute-Provence Observatory, with the SOPHIE spectrograph. SOPHIE is dedicated to the search of extrasolar planets, and, thanks to its high resolution (R~75000), it enables accurate stellar RVs to be measured for SB2 components. The RVs of the components are derived using the TwO-Dimensional CORrelation algorithm TODCOR (Zucker & Mazeh 1994ApJ...420..806Z; Zucker et al. 2004, Cat. J/A+A/426/695). (3 data files)
On the binary nature of the γ-ray sources AGL J2241+4454 (= MWC 656) and HESS J0632+057 (= MWC 148)
No full textWe present optical spectroscopy of MWC 656 and MWC 148, the proposed optical counterparts of the gamma-ray sources AGL J2241+4454 and HESS J0632+0 57, respectively. The main parameters of the Halpha emission line (EW, FWHM and centroid velocity) in these stars are modulated on the proposed orbital periods of 60.37 and 321 days, respectively. These modulations are likely produced by the resonant interaction of the Be discs with compact stars in eccentric orbits. We also present radial velocity curves of the optical stars folded on the above periods and obtain the first orbital elements of the two gamma-ray sources thus confirming their binary nature. Our orbital solution support eccentricities e~0.4 and 0.83+-0.08 for MWC 656 and MWC 148, respectively. Further, our orbital elements imply that the X-ray outbursts in HESS J0632+057/MWC 148 are delayed ~0.3 orbital phases after periastron passage, similarly to the case of LS I +61 303. In addition, the optical photometric light curve maxima in AGL J2241+4454/MWC 656 occur ~0.25 phases passed periastron, similar to what is seen in LS I +61 303. We also find that the orbital eccentricity is correlated with orbital period for the known gamma-ray binaries. This is explained by the fact that small stellar separations are required for the efficient triggering of VHE radiation. Another correlation between the EW of Halpha and orbital period is also observed, similarly to the case of Be/X-ray binaries. These correlations are useful to provide estimates of the key orbital parameters Porb and e from the Halpha line in future Be gamma-ray binary candidates
VizieR Online Data Catalog: Gaia SB2 radial velocity curves (Kiefer+, 2016)
No full textVizieR On-line Data Catalog: J/MNRAS/458/3272. Originally published in: 2016MNRAS.458.3272KThe observations were performed at the T193 telescope of the Haute-Provence Observatory, with the SOPHIE spectrograph. SOPHIE is dedicated to the search of extrasolar planets, and, thanks to its high resolution (R~75000), it enables accurate stellar RVs to be measured for SB2 components. The RVs of the components are derived using the TwO-Dimensional CORrelation algorithm todcor (Zucker & Mazeh 1994ApJ...420..806Z; Zucker et al. 2004, Cat. J/A+A/426/695). (2 data files)
Observational Evidence for Tidal Interaction in Close Binary Systems
No full textThis paper reviews the rich corpus of observational evidence for tidal
effects, mostly based on photometric and radial-velocity measurements.
This is done in a period when the study of binaries is being
revolutionized by large-scaled photometric surveys that are detecting
many thousands of new binaries and tens of extrasolar planets.
We begin by examining the short-term effects, such as ellipsoidal
variability and apsidal motion. We next turn to the long-term
effects, of which circularization was studied the most: a transition
period between circular and eccentric orbits has been derived for
eight coeval samples of binaries. The study of synchronization and
spin-orbit alignment is less advanced. 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. We also discuss synchronization in PMS and young
stars, and compare the emerging timescale with the circularization
timescale.
We next examine 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 elaborate on the
impact of the pumped eccentricity on the tidal evolution of close
binaries residing in triple systems, which may shrink the binary separation.
Finally we consider the extrasolar planets and the observational
evidence for tidal interaction with their parent stars. This includes
a mechanism that can induce radial drift of short-period planets,
either inward or outward, depending on the planetary radial position
relative to the corotation radius. Another effect is the
circularization of planetary orbits, the evidence for which can be
found in eccentricity-versus-period plot of the planets already known.
Whenever possible, the paper attempts to address the possible
confrontation between theory and observations, and to point out
noteworthy cases and observations that can be performed in the future
and may shed some light on the key questions that remain open
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