We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.

When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47 days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.

The Kepler space mission is devoted to finding Earth-size planets orbiting other stars in their habitable zones. Its large, 105 deg 2 field of view features over 156,000 stars that are observed continuously to detect and characterize planet transits. Yet, this high-precision instrument holds great promise for other types of objects as well. Here we present a comprehensive catalog of eclipsing binary stars observed by Kepler in the first 44 days of operation, the data being publicly available through MAST as of 2010 June 15. The catalog contains 1879 unique objects. For each object, we provide its Kepler ID (KID), ephemeris (BJD 0 , P 0 ), morphology type, physical parameters (T eff , log g, E(B − V )), the estimate of third light contamination (crowding), and principal parameters (T 2 /T 1 , q, fillout factor, and sin i for overcontacts, and T 2 /T 1 , (R 1 + R 2 )/a, e sin ω, e cos ω, and sin i for detached binaries). We present statistics based on the determined periods and measure the average occurrence rate of eclipsing binaries to be ∼1.2% across the Kepler field. We further discuss the distribution of binaries as a function of galactic latitude and thoroughly explain the application of artificial intelligence to obtain principal parameters in a matter of seconds for the whole sample. The catalog was envisioned to serve as a bridge between the now public Kepler data and the scientific community interested in eclipsing binary stars.

Cygnus X-1 is a binary star system that is comprised of a black hole and a massive giant companion star in a tight orbit. Building on our accurate distance measurement reported in the preceding paper, we first determine the radius of the companion star, thereby constraining the scale of the binary system. To obtain a full dynamical model of the binary, we use an extensive collection of optical photometric and spectroscopic data taken from the literature. By using all of the

We report photometric and spectroscopic observations of the black hole binary GRO J1655[40 in complete quiescence. In contrast to the 1995 photometry, the light curves from 1996 are almost completely dominated by ellipsoidal modulations from the secondary star. Model Ðts to the light curves, which take into account the temperature proÐle of the accretion disk and eclipse e †ects, yield an inclination of and a mass ratio of The precision of our determii \ 69¡ .50^0¡ .08Q \ M 1 /M 2 \ 2.99^0.08. nations of i and Q allow us to determine the black hole mass to an accuracy of B4% (M 1 \ 7.02^0.22The secondary starÏs mass is The position of the secondary on the M _ ).M 2 \ 2.34^0.12 M _ . Hertzsprung-Russell diagram is consistent with that of a B2.3 star that has evolved o † the main M _ sequence and is halfway to the start of the giant branch. Using the new spectra, we present an improved value of the spectroscopic period radial velocity semiamplitude (P \ 2d . 62157^0d . 00015), (K \ 228.2^2.2 km s~1), and mass function [ f (M) \ 3.24^0.09Based on the new spectra of the M _ ]. source and spectra of several MK spectral type standards, we classify the secondary star as F3 IVÈF6 IV. Evolutionary models suggest an average mass transfer rate for such a system of M 0 2 \ 3.4 ] 10~9 g s~1, which is much larger than the average mass transfer rates implied in the M _ yr~1 \ 2.16 ] 1017 other six transient black hole systems but is still barely below the critical mass transfer rate required for stability.

The new planets were identified using 671 days of data from the NASA Kepler spacecraft 10 . As part of its mission 11 to detect Earth-like planets via the transit method, Kepler is monitoring over 2,000 eclipsing binary stars 12,13 . From these we selected a sample of 750 systems with orbital periods ranging from 0.9 to 276 days, and for which eclipses of both stars occur. For each system, we measured the eclipse times and searched for departures from strict periodicity, as would be produced by gravitational perturbations from a third body.All 750 systems were searched by eye for planetary transits, with particular attention to an 18% subset that exhibited significant differences between the periods derived from the deeper primary eclipses, and those from the shallower secondary eclipses (for details see the Supplementary Information, SI). This led to the discovery of Kepler-34 and Kepler-35, and a candidate system KOI-2939. KOI-2939 (Kepler Input Catalog 14 number 05473556) exhibited a single transit at BJD 2,454,996.995 ± 0.010 of duration 2.5 hours and depth 0.18%. The transit duration constrains the size and velocity of the third body and is consistent with a Jovian planet transiting the secondary star, but we cannot verify its planetary nature. We defer discussion for a future investigation.The stars of Kepler-34 have an orbital period of 28 days, with a period difference between primary and secondary eclipses of 4.91 ± 0.59 s. Three transits were detected (Fig 1), with the first and second being transits of the primary star, while the third is of the secondary star. Notably the transit durations are all different, ruling out the most common type of "false positive," a background eclipsing binary. Circumbinary transits naturally vary in duration as a consequence of the changing velocity of the stars. The Kepler photometry were supplemented by spectroscopic observations of the radial-velocity variations of both stars (Fig. 1f), in order to determine the orbital scale and sizes of all three bodies. The photometric and spectroscopic data were fit with a model 9,15 that accounts for the three-body gravitational dynamics and the loss of light due to eclipses and transits (see SI). The model fit confirms that the transiting body is a planet with 22% the mass of Jupiter (69 Earth masses) and 76% the radius of Jupiter (8.6 Earth radii). The primary and secondary stars are similar to the Sun. With the spectra we also measured the effective temperature and abundance of heavy elements (metallicity) of both stars. The observed stellar parameters match the Yonsei-Yale theoretical models of stellar evolution 16 for an age of 5-6 Gyr. The parameters and uncertainties are given in Table 1, with details in the SI.The stars of Kepler-35 have an orbital period of 21 days, with a period difference between primary and secondary eclipses of 1.89 ± 0.48 s. Four transits were detected (Fig. 2 b,c,d,e). The first, second, and fourth events are transits of the primary star, and the weaker third event is a transit of the secondary st...

We examine the distribution of masses of black holes in transient low mass X-ray binary systems. A Bayesian analysis suggests that it is probable that six of the seven systems with measured mass functions have black hole masses clustered near seven solar masses. There appears to be a significant gap between the masses of these systems and those of the observed neutron stars. The remaining source, V404 Cyg, has a mass significantly larger than the others, and our analysis suggests that it is probably drawn from a different distribution. Selection effects do not appear to play a role in producing the observed mass distribution, which may be explained by currently unknown details of the supernova explosions and of binary evolution prior to the supernova.Comment: 22 pages including figures, submitted to Ap

We continue to investigate the X-ray properties of the black hole binary XTE J1550À564. By grouping observations (1998)(1999) according to the type of low-frequency quasiperiodic oscillation (LFQPO) identified in a previous paper, we show evidence that two high-frequency QPOs (HFQPOs) occur simultaneously near 184 and 276 Hz. We can model the QPO profiles while assuming that the central frequencies are related by a 3 : 2 ratio. In one group, there is some evidence of a broad feature at the fundamental frequency of 92 Hz. We also investigate the 2000 April outburst, and we confirm the suggestion of Miller et al. that a 270 Hz QPO is accompanied by a second feature near 180 Hz. The histogram for the 28 individual HFQPO detections in XTE J1550À564 shows two peaks near 184 and 276 Hz, while there is a notable exception in the 143 Hz QPO detected on 1998 October 15. Similarly, all of the 13 HFQPO detections in the black hole binary GRO J1655À40 occur at two frequencies that are related by a 3 : 2 ratio. We next investigate all of the energy spectra for XTE J1550À564, and we find a systematic increase in the strength of the power-law component as the stronger of the two HFQPOs shifts from 276 to 184 Hz. A strikingly similar result is seen in the spectra of GRO J1655À40 when the stronger HFQPO shifts from 450 to 300 Hz. The fundamental HFQPO frequencies for the two X-ray sources scale as M À1 , which is consistent with the hypotheses that these HFQPOs represent some kind of oscillation rooted in general relativity (GR) and that the two black holes have similar values of the dimensionless spin parameter. We discuss physical mechanisms that may explain these HFQPOs. A resonance between orbital and radial coordinate frequencies is one possibility suggested by Abramowicz & Kluzniak. For XTE J1550À564, this would imply moderate values for the dimensionless spin parameter (0:1 < a à < 0:6), with similar results for GRO J1655À40. A resonance between polar and radial coordinate frequencies allows additional values for a * above 0.9. There remain serious uncertainties regarding the physical mechanism whereby resonances in coordinate frequencies may produce HFQPOs. We also discuss models for '' diskoseismic '' oscillations. In this case, the concept that the inner disk behaves as a resonance cavity in GR has certain attractions for explaining HFQPOs, but integral harmonics are not predicted for the three types of diskoseismic modes derived for adiabatic perturbations in a thin accretion disk.