A survey for planetary transits in the field of NGC 7789 (original) (raw)
Related papers
A new search for planet transits in NGC 6791
Astronomy and Astrophysics, 2007
Context. Searching for planets in open clusters allows us to study the effects of dynamical environment on planet formation and evolution. Aims. Considering the strong dependence of planet frequency on stellar metallicity, we studied the metal rich old open cluster NGC 6791 and searched for close-in planets using the transit technique. Methods. A ten-night observational campaign was performed using the Canada-France-Hawaii Telescope (3.6m), the San Pedro Mártir telescope (2.1m), and the Loiano telescope (1.5m). To increase the transit detection probability we also made use of the Bruntt et al. eight-nights observational campaign. Adequate photometric precision for the detection of planetary transits was achieved. Results. Should the frequency and properties of close-in planets in NGC 6791 be similar to those orbiting field stars of similar metallicity, then detailed simulations foresee the presence of 2-3 transiting planets. Instead, we do not confirm the transit candidates proposed by . The probability that the null detection is simply due to chance coincidence is estimated to be 3%-10%, depending on the metallicity assumed for the cluster. Conclusions. Possible explanations of the null-detection of transits include: (i) a lower frequency of close-in planets in star clusters; (ii) a smaller planetary radius for planets orbiting super metal rich stars; or (iii) limitations in the basic assumptions. More extensive photometry with 3-4m class telescopes is required to allow conclusive inferences about the frequency of planets in NGC 6791.
A dearth of planetary transits in the direction of NGC 6940
Monthly Notices of …, 2005
We present results of our survey for planetary transits in the field of NGC 6940. We think nearly all of our observed stars are field stars. We have obtained high precision (∼3-10 millimags at the bright end) photometric observations of ∼50,000 stars spanning 18 nights in an attempt to identify low amplitude and short period transit events. We have used a matched filter analysis to identify 14 stars that show multiple events, and four stars that show single transits. Of these 18 candidates, we have identified two that should be further researched. However, none of the candidates are convincing hot Jupiters.
Searching for planetary transits in the field of open cluster NGC 6819I
Monthly Notices of …, 2003
We present results from our survey for planetary transits in the field of the intermediate age (∼2.5 Gyr), metal-rich ([Fe/H]∼+0.07) open cluster NGC 6819. We have obtained highprecision time-series photometry for over 38,000 stars in this field and have developed an effective matched-filter algorithm to search for photometric transits. This algorithm identified 8 candidate stars showing multiple transit-like events, plus 3 stars with single eclipses. On closer inspection, while most are shown to be low mass stellar binaries, some of these events could be due to brown dwarf companions. The data for one of the single-transit candidates indicates a minimum radius for the companion similar to that of HD 209458b.
A search for planets in the old open cluster NGC 6791
Astronomy & Astrophysics, 2003
We describe the results of a search for transit-like events caused by giant planets occulting stars in the old, metal-rich open cluster NGC 6791 based on BVI-colour photometry from eight nights of observations with the 2.54m Nordic Optical Telescope. To extract the light curves we have used both PSF photometry (DAOPHOT) and the difference imaging technique (ISIS). We have re-analyzed observations from earlier campaigns to search for multiple transits, determine periods of long-period variables, and detect eclipsing binaries. We confirm 20 known variables and have discovered 22 new low-amplitude variables with amplitudes in the range 7--40 mmag and periods 1--16 days. We have found the primary and secondary eclipses of two eclipsing binaries based on the new and older photometric campaigns. The search for transits-like events has turned up a few single-transit candidates. The transit depths are 10 mmag in both the V and I filters over periods of 1.0--2.5 hours, but future observations are required to see whether identical transit-like events recur in these same stars.
A Photometric Search for Planets in the Open Cluster NGC 7086
The Astronomical Journal, 2006
In an attempt to discover short-period, Jupiter-mass planets orbiting solar-type stars in open clusters, we searched for planetary transits in the populous and relatively unstudied open cluster NGC 7086. A color-magnitude diagram constructed from new B and V photometry is presented, along with revised estimates of the cluster's color excess, distance modulus, and age. Several turnoff stars were observed spectroscopically in order to determine a color excess of E(B À V ) ¼ 0:83 AE 0:02. Empirically fitting the main sequences of two young open clusters and the semiempirical zero-age main sequence of Vandenberg and Poll yielded a distance modulus of (V À M V ) ¼ 13:4 AE 0:3 mag. This corresponds to a true distance modulus of (m À M ) 0 ¼ 10:8 mag or a distance of 1.5 kpc to NGC 7086. These values were used with isochrones from the Padova group to obtain a cluster age of 100 Myr. Eleven nights of R-band photometry were used to search for planetary transits. Differential magnitudes were constructed for each star in the cluster. Light curves for each star were produced on a night-to-night basis and inspected for variability. No planetary transits were apparent; however, some interesting variable stars were discovered: a pulsating variable that appears to be a member of the Dor class and four possible eclipsing binary stars, one of which actually may be a multiple system.
The Monitor project: the search for transits in the open cluster NGC 2362
Monthly Notices of the Royal Astronomical Society, 2008
We present the results of a systematic search for transiting planets in a ∼5 Myr open cluster, NGC 2362. We observed ∼1200 candidate cluster members, of which ∼475 are believed to be genuine cluster members, for a total of ∼100 hours. We identify 15 light curves with reductions in flux that pass all our detection criteria, and 6 of the candidates have occultation depths compatible with a planetary companion. The variability in these six light curves would require very large planets to reproduce the observed transit depth. If we assume that none of our candidates are in fact planets then we can place upper limits on the fraction of stars with hot Jupiters (HJs) in NGC 2362. We obtain 99% confidence upper limits of 0.22 and 0.70 on the fraction of stars with HJs (f p ) for 1-3 and 3-10 day orbits, respectively, assuming all HJs have a planetary radius of 1.5R Jup . These upper limits represent observational constraints on the number of stars with HJs at an age 10 Myr, when the vast majority of stars are thought to have lost their protoplanetary discs. Finally, we extend our results to the entire Monitor Project, a survey searching young, open clusters for planetary transits, and find that the survey as currently designed should be capable of placing upper limits on f p near the observed values of f p in the solar neighbourhood.
University of St.Andrews Open Cluster Survey for Hot Jupiters
arXiv (Cornell University), 2002
We are using the Isaac Newton Telescope Wide Field Camera to survey open cluster fields for transiting hot Jupiter planets. Clusters were selected on the basis of visibility, richness of stars, age and metallicity. Observations of NGC 6819, 6940 and 7789 began in 1999 and continued in 2000. We have developed an effective matched-filter transit-detection algorithm which has proved its ability to identify very low amplitude eclipse events in real data. Here we present our results for NGC 6819. We have identified 7 candidates showing transit-like events. Colour information suggests that most of the companion bodies are likely to be very-low-mass stars or brown dwarfs, intrinsically interesting objects in their own right.
Outcome of Six Candidate Transiting Planets from a TrES Field in Andromeda
2006
Driven by the incomplete understanding of the formation of gas giant extrasolar planets and of their mass-radius relationship, several ground-based, wide-field photometric campaigns are searching the skies for new transiting extrasolar gas giants. As part of the Trans-atlantic Exoplanet Survey (TrES), in 2003/4 we monitored approximately 30,000 stars (9.5 ≤ V ≤ 15.5) in a 5.7 • × 5.7 • field in Andromeda with three telescopes over five months. We identified six candidate transiting planets from the stellar light curves. From subsequent follow-up observations, we rejected each of these as an astrophysical false positive, i.e. a stellar system containing an eclipsing binary, whose light curve mimics that of a Jupiter-sized planet transiting a sun-like star. We discuss here the procedures followed by the TrES team to reject false positives from our list of candidate transiting hot Jupiters. We present these candidates as early examples of the various types of astrophysical false postives found in the TrES campaign, and discuss what we learned from the analysis.
Detection of a transit by the planetary companion of HD 80606
We report the detection of a transit egress by the ~ 3.9-Jupiter-mass planet HD 80606b, an object in a highly-eccentric orbit (e ~ 0.93) about its parent star of approximately solar type. The astrophysical reality of the signal of variability in HD 80606 is confirmed by observation with two independent telescope systems, and checks against several reference stars in the field. Differential photometry with respect to the nearby comparison star HD 80607 provides a precise light curve. Modelling of the light curve with a full eccentric-orbit model indicates a planet/star-radius ratio of 0.1057 +/- 0.0018, corresponding to a planet radius of 1.029 R_J for a solar-radius parent star; and a precise orbital inclination of 89.285 +/- 0.023 degrees, giving a total transit duration of 12.1 +/- 0.4 hours. The planet hence joins HD 17156b in a class of highly eccentric transiting planets, in which HD 80606b has both the longest period and most eccentric orbit. The recently reported discovery of a secondary eclipse of HD 80606b by the Spitzer Space Observatory permits a combined analysis with the mid-time of primary transit in which the orbital parameters of the system can be tightly constrained. We derive a transit ephemeris of T_tr = HJD (2454876.344 +/- 0.011) + (111.4277 +/- 0.0032) E.
The Astronomical Journal, 2016
The past two decades have seen a significant advancement in the detection, classification, and understanding of exoplanets and binaries. This is due, in large part, to the increase in use of small-aperture telescopes (<20 cm) to survey large areas of the sky to milli-mag precision with rapid cadence. The vast majority of the planetary and binary systems studied to date consists of main-sequence or evolved objects, leading to a dearth of knowledge of properties at early times (<50 Myr). Only a dozen binaries and one candidate transiting Hot Jupiter are known among pre-main-sequence objects, yet these are the systems that can provide the best constraints on stellar formation and planetary migration models. The deficiency in the number of wellcharacterized systems is driven by the inherent and aperiodic variability found in pre-main-sequence objects, which can mask and mimic eclipse signals. Hence, a dramatic increase in the number of young systems with high-quality observations is highly desirable to guide further theoretical developments. We have recently completed a photometric survey of threenearby (<150 pc) and young (<50 Myr) moving groups with a small-aperture telescope. While our survey reached the requisite photometric precision, the temporal coverage was insufficient to detect Hot Jupiters. Nevertheless, we discovered 346 pre-main-sequence binary candidates, including 74 high-priority objects for further study.