So far radial velocity (RV) measurements have discovered ~25 stars to host multiple planets. The statistics imply that many of the known hosts of transiting planets should have additional planets, yet none have been solidly detected. They will be soon, via complementary search methods of RV, transit-time variations (TTV) of the known planet, and transits of the additional planet. When they are found, what can transit measurements add to studies of multiplanet dynamical evolution? First, mutual inclinations become measurable, for comparison to the solar system's disk-like configuration. Such measurements will give important constraints to planet-planet scattering models, just as the RV measurements of eccentricity have done. Second, the Rossiter-McLaughlin effect measures stellar obliquity, which can be modified by two-planet dynamics with a tidally evolving inner planet. Third, TTV is exquisitely sensitive to planets in mean motion resonance. Two planets differentially migrating in the disk can establish such resonances, and tidal evolution of the planets can break them, so the configuration and frequency of these resonances as a function of planetary parameters will constrain these processes.
Ground-based searches for transiting Jupiter-sized planets have so far produced few detections of planets, but many of stellar systems with eclipse depths, durations, and orbital periods that resemble those expected from planets. I show that these detection rates are consistent with our present knowledge of binary and multiple-star systems, and of Jovian-mass extrasolar planets. Upcoming space-based searches for transiting Earth-sized planets will be largely unaffected by the sources of false alarms that afflict current ground-based searches, with one exception, namely distant eclipsing binari…
The transits of a planet on a Keplerian orbit occur at time intervals exactly equal to the period of the orbit. If a second planet is introduced the orbit is not Keplerian and the transits are no longer exactly periodic. We compute the magnitude of these variations in the timing of the transits, dt. We investigate analytically several limiting cases: (i) interior perturbing planets with much smaller periods; (ii) exterior perturbing planets on eccentric orbits with much larger periods; (iii) both planets on circular orbits with arbitrary period ratio but not in resonance; and (iv) planets on i…
The proposed Transiting Exoplanet Survey Satellite (TESS) will survey the entire sky to locate the nearest and brightest transiting extrasolar planets with orbital periods up to about 36 days. Here we estimate the number and kind of astrophysical false positives that TESS will report, along with the number of extrasolar planets. These estimates are then used to size the ground-based follow-up observing efforts needed to confirm and characterize the planets. We estimate that the needed observing resources will be about 1400 telescope-nights of imaging with 0.5m to 1m-class telescopes, 300 teles…
Ground-based photometric surveys have led to the discovery of six transiting exoplanets, five of which were detected by the OGLE survey. The FLAMES multi-object spectrograph on the VLT has permitted a very efficient follow-up of the OGLE transit candidates, characterising not only the 5 planets but also more than 50 systems producing similar photometric signatures -- mainly eclipsing binaires. The presence of these ubiquitous "impostors" is a challenge for transit surveys. Another difficulty is the presence of red noise in the photometry, which implies a much lower sensitivity to transiting pl…
We report the discovery and characterisation of OGLE-TR-122b, the smallest main-sequence star to date with a direct radius determination. OGLE-TR-122b transits around its solar-type primary every 7.3-days. With M=0.092+-0.009 Mo and R=0.120 +0.024-0.013 Ro, it is by far the smallest known eclipsing M-dwarf. The derived mass and radius for OGLE-TR-122b are in agreement with the theoretical expectations. OGLE-TR-122b is the first observational evidence that stars can indeed have radii comparable or even smaller than giant planets. In such cases, the photometric signal is exactly that of a transi…
We have undertaken a long-term project, Planets in Stellar Clusters Extensive Search (PISCES), to search for transiting planets in open clusters. In this paper we present the results for NGC 6791 -- a very old, populous, metal rich cluster. We have monitored the cluster for over 300 hours, spread over 84 nights. We have not detected any good transiting planet candidates. Given the photometric precision and temporal coverage of our observations, and current best estimates for the frequency and radii of short-period planets, the expected number of detectable transiting planets in our sample is 1…
Transiting planets manifest themselves by a periodic dimming of their host star by a fixed amount. On the other hand, light curves of transiting circumbinary (CB) planets are expected to be neither periodic nor to have a single depth while in transit, making BLS [Kovacs et al. 2002] almost ineffective. Therefore, a modified version for the identification of CB planets was developed - CB-BLS. We show that using CB-BLS it is possible to find CB planets in the residuals of light curves of eclipsing binaries (EBs) that have noise levels of 1% or more. Using CB-BLS will allow to easily harness the …
Through a simple physical argument we show that the slant optical depth through the atmosphere of a "hot Jupiter" planet is 35-90 times greater than the normal optical depth. This not unexpected result has direct consequences for the method of transmission spectroscopy for characterizing the atmospheres of transiting giant planets. The atmospheres of these planets likely contain minor condensates and hazes which at normal viewing geometry have negligible optical depth, but at slant viewing geometry have appreciable optical depth that can obscure absorption features of gaseous atmospheric speci…
We present theoretical predictions for photometric and spectroscopic signatures of rings around transiting extrasolar planets. On the basis of a general formulation for the transiting signature in the stellar light curve and the velocity anomaly due to the Rossiter effect, we compute the expected signals analytically for a face-on ring system, and numerically for more general configurations. We study the detectability of a ring around a transiting planet located at a=3AU for a variety of obliquity and azimuthal angles, and find that it is possible to detect the ring signature both photometrica…
The star XO-5 (GSC 02959-00729, V=12.1, G8V) hosts a Jupiter-sized, Rp=1.15+/-0.12 Rjup, transiting extrasolar planet, XO-5b, with an orbital period of P=4.187732+/-0.00002 days. The planet mass (Mp=1.15+/-0.08 Mjup) and surface gravity (gp=22+/-5 m/s^2) are significantly larger than expected by empirical Mp-P and Mp-P-[Fe/H] relationships. However, the deviation from the Mp-P relationship for XO-5b is not large enough to suggest a distinct type of planet as is suggested for GJ 436b, HAT-P-2b, and XO-3b. By coincidence XO-5 overlies the extreme H I plume that emanates from the interacting gala…
We calculate the theoretical evolution of the radii of all fourteen of the known transiting extrasolar giant planets (EGPs) for a variety of assumptions concerning atmospheric opacity, dense inner core masses, and possible internal power sources. We incorporate the effects of stellar irradiation and customize such effects for each EGP and star. Looking collectively at the family as a whole, we find that there are in fact two radius anomalies to be explained. Not only are the radii of a subset of the known transiting EGPs larger than expected from previous theory, but many of the other objects …
(Abridged) The solar system gas giant planets are oblate due to their rapid rotation. A measurement of the planet's projected oblateness would constrain the planet's rotational period. Planets that are synchronously rotating with their orbital revolution will be rotating too slowly to be significantly oblate; these include planets with orbital semi-major axes <~ 0.2AU (for M_P ~ M_J and M_* ~ M_sun). Jupiter-like planets in the range of orbital semi-major axes 0.1 AU to 0.2 AU will tidally evolve to synchronous rotation on a timescale similar to main sequence stars' lifetimes. In this case an …
Transiting planets manifest themselves by a periodic dimming of their host star by a fixed amount. On the other hand, light curves of transiting circumbinary (CB) planets are expected to be neither periodic nor to have a single depth while in transit. These propertied make the popular transit finding algorithm BLS almost ineffective so a modified version of BLS for the identification of CB planets was developed - CB-BLS. We show that using this algorithm it is possible to find CB planets in the residuals of light curves of eclipsing binaries that have noise levels of 1% and more - quality that…
We have searched for absorption in several common atomic species due to the atmosphere or exosphere of the transiting extrasolar planet HD 209458b, using high precision optical spectra obtained with the Subaru High Dispersion Spectrograph (HDS). Previously we reported an upper limit on H alpha absorption of 0.1% (3 sigma) within a 5.1Åband. Using the same procedure, we now report upper limits on absorption due to the optical transitions of Na D, Li, H alpha, H beta, H gamma, Fe, and Ca. The 3 sigma upper limit for each transition is approximately 1% within a 0.3Åband (the core of the line), an…
Future surveys for transiting extrasolar planets, including the space-based mission Kepler (Borucki et al 2003), are expected to detect hundreds of Jovian mass planets and tens of terrestrial mass planets. For many of these newly discovered planets, the intervals between successive transits will be measured with an accuracy of 0.1--100 minutes. We show that these timing measurements will allow for the detection of additional planets in the system (not necessarily transiting), via their gravitational interaction with the transiting planet. The transit time variations depend on the mass of the a…
Many of the planets discovered via the radial velocity technique are hot Jupiters in 3-5 day orbits with ~10$% chance of transiting their parent star. However, radial velocity surveys for extra-solar planets generally require substantial amounts of large telescope time in order to monitor a sufficient number of stars due to the single-object capabilities of the spectrograph. A multi-object Doppler survey instrument has been developed which is based on the dispersed fixed-delay interferometer design. We present simulations of the expected results from the Sloan Doppler survey based on calculate…
In the ongoing HATNet survey we have detected a giant planet, with radius 1.33 +/- 0.06 RJup and mass 1.06 +/- 0.12 MJup, transiting the bright (V = 10.5) star GSC 03239-00992. The planet is in a circular orbit with period 3.852985 +/- 0.000005 days and mid-transit epoch 2,454,035.67575 +/- 0.00028 (HJD). The parent star is a late F star with mass 1.29 +/- 0.06 Msun, radius 1.46 +/- 0.06 Rsun, Teff ~ 6570 +/- 80 K, [Fe=H] = -0.13 +/- 0.08 and age ~ 2.3+/-^{0.5}_{0.7}Gy. With this radius and mass, HAT-P-6b has somewhat larger radius than theoretically expected. We describe the observations and …
We have undertaken a long-term project, Planets in Stellar Clusters Extensive Search (PISCES), to search for transiting planets in open clusters. In this paper we present the results for NGC 2158, an intermediate age, populous cluster. We have monitored the cluster for over 260 hours, spread over 59 nights. We have detected one candidate transiting low luminosity object, with eclipse depth of 3.7% in the R-band. If the host star is a member of the cluster, the eclipse depth is consistent with a 1.7 R_J object. Cluster membership of the host is supported by its location on the cluster main sequ…
We re-examine the photometric and spectroscopic evidence available for the star OGLE-TR-56, recently discovered to harbor a giant planet presenting transits and orbiting with a period of 1.21 days. We investigate the possibility that the observational signatures reported might be the result of "blending" with the light of an eclipsing binary along the same line of sight. Using techniques developed earlier we perform fits to the light curve under a variety of blend configurations, subject to all observational constraints, and we infer further properties of these possible blends. We then carry o…
We present first results from the Survey for Transiting Extrasolar Planets in Stellar Systems (STEPSS). Our goal is to assess the frequency of close-in extrasolar planets around main-sequence stars in several open clusters. By concentrating on main-sequence stars in clusters of known (and varied) age, metallicity, and stellar density, we will gain insight into how these various properties affect planet formation, migration, and survival. We show preliminary results from our 19 night photometric campaign of the old, solar metallicity cluster NGC 1245. Taking into account the photometric precisi…
We report the detection of transits by the 3.1 M_Jup companion to the V=8.17 G0V star HD 17156. The transit was observed by three independant observers on Sept. 9/10, 2007 (two in central Italy and one in the Canary Islands), who obtained detections at confidence levels of 3.0 sigma, 5.3 sigma, and 7.9 sigma, respectively. The observations were carried out under the auspices of the Transitsearch.org network, which organizes follow-up photometric transit searches of known planet-bearing stars during the time intervals when transits are expected to possibly occur. Analyses of the 7.9 sigma data …
We analyze a 19-night photometric search for transiting extrasolar planets in the open cluster NGC 1245. An automated transit search algorithm with quantitative selection criteria finds six transit candidates; none are bona fide planetary transits. We characterize the survey detection probability via Monte Carlo injection and recovery of realistic limb-darkened transits. We use this to derive upper limits on the fraction of cluster members with close-in Jupiter-radii, RJ, companions. We carefully analyze the random and systematic errors of the calculation. For similar photometric noise and wea…
We investigate the effect of planetary rotation on the transit spectrum of an extrasolar giant planet. During ingress and egress, absorption features arising from the planet's atmosphere are Doppler shifted by of order the planet's rotational velocity (~1-2 km/s) relative to where they would be if the planet were not rotating. We focus in particular on the case of HD209458b, which ought to be at least as good a target as any other known transiting planet. For HD209458b, this shift should give rise to a small net centroid shift of ~60 cm/s on the stellar absorption lines. Using a detailed model…
We develop a method for predicting the yield of transiting planets from a photometric survey given the parameters of the survey (nights observed, bandpass, exposure time, telescope aperture, locations of the target fields, observational conditions, and detector characteristics), as well as the underlying planet properties (frequency, period and radius distributions). Using our updated understanding of transit surveys provided by the experiences of the survey teams, we account for those factors that have proven to have the greatest effect on the survey yields. Specifically, we include the effec…
We have measured transit times for HD 189733b passing in front of its bright (V = 7.67) chromospherically active and spotted parent star. Nearly continuous broadband optical photometry of this system was obtained with the MOST (Microvariability & Oscillations of STars) space telescope during 21 days in August 2006, monitoring 10 consecutive transits. We have used these data to search for deviations from a constant orbital period which can indicate the presence of additional planets in the system that are as yet undetected by Doppler searches. There are no transit timing variations above the le…
For extrasolar planets with orbital periods, P>10 days, radial velocity surveys find non-circular orbital eccentricities are common, <e>~0.3. Future surveys for extrasolar planets using the transit technique will also have sensitivity to detect these longer period planets. Orbital eccentricity affects the detection of extrasolar planets using the transit technique in two opposing ways: an enhancement in the probability for the planet to transit near pericenter and a reduction in the detectability of the transit due to a shorter transit duration. For an eccentricity distribution matching the cu…
We have computed evolutionary models for extrasolar planets which range in mass from 0.1 to 3.0 Jovian Masses, and which range in equilibrium temperature from 113 K to 2000 K. We present four sequences of models, designed to show the structural effects of a solid core and of internal heating due to the conversion of kinetic to thermal energy at pressures of tens of bars. The model planetary radii are intended for comparisons with radii derived from observations of transiting extrasolar planets. To provide such comparisons, we expect that of order 10 transiting planets with orbital periods less…
We discuss preliminary results from our first search campaign for transiting planets performed using Sleuth, an automated 10 cm telescope with a 6 degree square field of view. We monitored a field in Hercules for 40 clear nights between UT 2003 May 10 and July 01, and obtained an rms precision (per 15-min average) over the entire data set of better than 1% on the brightest 2026 stars, and better than 1.5% on the brightest 3865 stars. We identified no strong candidates in the Hercules field. We conducted a blind test of our ability to recover transiting systems by injecting signals into our dat…
