We report the discovery of WTS1b, the first extrasolar planet found by the WFCAM Transit Survey. ... more We report the discovery of WTS1b, the first extrasolar planet found by the WFCAM Transit Survey. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby- Eberly Telescope (HET) allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V = 16.13), and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the companion of 3.35 days, a planetary mass of 4.01 ± 0.35 MJ, and a planetary radius of 1.49 +0.16 −0.18 RJ. WTS1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 MJ.
We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey,... more We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ∼ 16 were constructed for ∼ 60 000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, highresolution spectra taken at the Hobby-Eberly Telescope allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01±0.35MJ , and a planetary radius of 1.49 −0.18 RJ . WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5MJ .
Monthly Notices of the Royal Astronomical Society, 2012
We report the discovery of 16 detached M-dwarf eclipsing binaries with J < 16 mag and provide a d... more We report the discovery of 16 detached M-dwarf eclipsing binaries with J < 16 mag and provide a detailed characterisation of three of them, using high-precision infrared light curves from the WFCAM Transit Survey (WTS). Such systems provide the most accurate and model-independent method for measuring the fundamental parameters of these poorly understood yet numerous stars, which currently lack sufficient observations to precisely calibrate stellar evolution models. We fully solve for the masses and radii of three of the systems, finding orbital periods in the range 1.5 < P < 4.9 days, with masses spanning 0.35 − 0.50M ⊙ and radii between 0.38 − 0.50R ⊙ , with uncertainties of ∼ 3.5 − 6.4% in mass and ∼ 2.7 − 5.5% in radius. Close-companions in short-period binaries are expected to be tidally-locked into fast rotational velocities, resulting in high levels of magnetic activity. This is predicted to inflate their radii by inhibiting convective flow and increasing star spot coverage. The radii of the WTS systems are inflated above model predictions by ∼ 3 − 12%, in agreement with the observed trend, despite an expected lower systematic contribution from star spots signals at infrared wavelengths. We searched for correlation between the orbital period and radius inflation by combining our results with all existing M-dwarf radius measurements of comparable precision, but we found no statistically significant evidence for a decrease in radius inflation for longer period, less active systems. Radius inflation continues to exists in non-synchronised systems indicating that the problem remains even for very low activity M-dwarfs. Resolving this issue is vital not only for understanding the most populous stars in the Universe, but also for characterising their planetary companions, which hold the best prospects for finding Earth-like planets in the traditional habitable zone.
We report the discovery of WTS-2 b, a typical hot Jupiter in an unusually close 1.02-day orbit to... more We report the discovery of WTS-2 b, a typical hot Jupiter in an unusually close 1.02-day orbit to a K-dwarf star. This is the second planet to be discovered in the infrared light curves of the WFCAM Transit Survey (WTS) and is only one-and-a-half times the separation from its host star at which is would be destroyed by Roche lobe overflow. The predicted remaining lifetime of the planet is just 38 Myrs, assuming a tidal dissipation quality factor of Q = 10 6 . The magnitude of Q is largely unconstrained by observations, thus WTS-2 b provides a useful calibration point for theories describing how frictional processes within a host star affect the tidal orbital evolution of its companion giant planets. It is expected that stars with large convective envelopes are more efficient at dissipating the orbital energy of the planet, and WTS-2 b provides an observational constraint in the sparsely populated K-dwarf regime. In addition, despite its relatively faint magnitude, the favourable size ratio of the WTS-2 star-planet system and the predicted hot equilibrium temperature of the planet will make it possible to characterise the planet's atmosphere via secondary eclipse measurements using existing ground-based instrumentation.
Monthly Notices of the Royal Astronomical Society, 2012
We report on the discovery of four ultra-short period (P 0.18 days) eclipsing M-dwarf binaries in... more We report on the discovery of four ultra-short period (P 0.18 days) eclipsing M-dwarf binaries in the WFCAM Transit Survey. Their orbital periods are significantly shorter than of any other known main-sequence binary system, and are all significantly below the sharp period cut-off at P ∼ 0.22 days as seen in binaries of earlier type stars. The shortest-period binary consists of two M4 type stars in a P = 0.112 day orbit. The binaries are discovered as part of an extensive search for short-period eclipsing systems in over 260,000 stellar lightcurves, including over 10,000 M-dwarfs down to J=18 mag, yielding 25 binaries with P 0.23 days. In a popular paradigm, the evolution of short period binaries of cool main-sequence stars is driven by loss of angular momentum through magnetised winds. In this scheme, the observed P ∼0.22 day period cut-off is explained as being due to timescales that are too long for lower-mass binaries to decay into tighter orbits. Our discovery of low-mass binaries with significantly shorter orbits implies that either these timescales have been overestimated for M-dwarfs, e.g. due to a higher effective magnetic activity, or that the mechanism for forming these tight M-dwarf binaries is different from that of earlier type main-sequence stars.
Monthly Notices of the Royal Astronomical Society, 2013
The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom In... more The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom Infrared Telescope (UKIRT), designed to discover planets around M dwarfs. The WTS acts as a poor-seeing backup programme for the telescope, and represents the first dedicated wide-field near-infrared transit survey. Observations began in 2007 gathering J-band photometric observations in four (seasonal) fields. In this paper we present an analysis of the first of the WTS fields, covering an area of 1.6 square degrees. We describe the observing strategy of the WTS and the processing of the data to generate lightcurves. We describe the basic properties of our photometric data, and measure our sensitivity based on 950 observations. We show that the photometry reaches a precision of ∼ 4 mmag for the brightest unsaturated stars in lightcurves spanning almost 3 years. Optical (SDSS griz) and near-infrared (UKIRT ZY JHK) photometry is used to classify the target sample of 4600 M dwarfs with J magnitudes in the range 11-17. Most have spectral-types in the range M0-M2. We conduct Monte Carlo transit injection and detection simulations for short period (<10 day) Jupiterand Neptune-sized planets to characterize the sensitivity of the survey. We investigate the recovery rate as a function of period and magnitude for 4 hypothetical star-planet cases: M0-2+Jupiter, M2-4+Jupiter, M0-2+Neptune, M2-4+Neptune. We find that the WTS lightcurves are very sensitive to the presence of Jupiter-sized short-period transiting planets around M dwarfs. Hot Neptunes produce a much weaker signal and suffer a correspondingly smaller recovery fraction. Neptunes can only be reliably recovered with the correct period around the rather small sample (∼ 100) of the latest M dwarfs (M4-M9) in the WTS. The non-detection of a hot-Jupiter around an M dwarf by the WFCAM Transit Survey allows us to place an upper limit of 1.7-2.0 per cent (at 95 per cent confidence) on the planet occurrence rate.
Monthly Notices of the Royal Astronomical Society, 2012
We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey,... more We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ∼ 16 were constructed for ∼ 60 000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, highresolution spectra taken at the Hobby-Eberly Telescope allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01±0.35 M J , and a planetary radius of 1.49 +0.16 −0.18 R J. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 M J .
Monthly Notices of the Royal Astronomical Society, 2014
We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (M P = 1.12M J , R... more We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (M P = 1.12M J , R P = 1.363R J) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ∼ 20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ∼ 40 Myr, assuming a tidal dissipation quality factor of Q ′ ⋆ = 10 6. Q ′ ⋆ is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T shift ∼ 17 seconds after 15 years assuming Q ′ ⋆ = 10 6. A shift less than this would place a direct observational constraint on the lower limit of Q ′ ⋆ in this system. We also report a correction to the previously published expected T shift for WASP-18 b, finding that T shift = 356 seconds after 10 years for Q ′ ⋆ = 10 6 , which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q ′ ⋆ via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straightforward constraints on Q ′ ⋆ will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.
ABSTRACT We have identified photometric white dwarf candidates in the WFCAM transit survey throug... more ABSTRACT We have identified photometric white dwarf candidates in the WFCAM transit survey through a reduced proper motion versus colour approach. Box-fitting with parameters adjusted to detect the unique signature of a white dwarf + planet/brown dwarf transit/eclipse event was performed, as well as looking for variability due to the irradiation of the companions atmosphere by the white dwarf&#39;s high UV flux. We have also performed a simple sensitivity analysis in order to assess the ability of the survey to detect companions to white dwarfs via the transit method.
Monthly Notices of the Royal Astronomical Society, 2013
Halo subdwarfs, metal deficient dwarfs. View project Develop data analysis tools to detect low ma... more Halo subdwarfs, metal deficient dwarfs. View project Develop data analysis tools to detect low mass planets around Sun-like stars using radial velocity technique View project
ABSTRACT The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-... more ABSTRACT The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that difference-photometry light curves present an important improvement for stars with J &gt; 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the box-fitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J ≤ 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes.
Monthly Notices of the Royal Astronomical Society, 2014
ABSTRACT We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12M... more ABSTRACT We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12MJ, Rp=1.363RJ) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ~20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ~40 Myr, assuming a tidal dissipation quality factor of Q&amp;#39;*=10^6. Q&amp;#39;* is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T_shift~17 seconds after 15 years assuming Q&amp;#39;*=10^6. A shift less than this would place a direct observational constraint on the lower limit of Q&amp;#39;* in this system. We also report a correction to the previously published expected T_shift for WASP-18 b, finding that T_shift=356 seconds after 10 years for Q&amp;#39;*=10^6, which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q&amp;#39;* via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straight-forward constraints on Q&amp;#39;* will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.
ABSTRACT The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United K... more ABSTRACT The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom Infrared Telescope (UKIRT). We conduct Monte Carlo transit injection and detection simulations for short period (&lt;10 day) Jupiter-sized planets to characterize the sensitivity of the survey. We investigate the recovery rate as a function of period and magnitude in 2 hypothetical star-planet cases: M0-2 + hot Jupiter, M2-4 + hot Jupiter. We find that the WTS lightcurves are very sensitive to the presence of Jupiter-sized short-period transiting planets around M dwarfs. The non-detection of a hot-Jupiter around an M dwarf by the WFCAM Transit Survey allows us to place a firm upper limit of 1.9 per cent (at 95 per cent confidence) on the planet occurrence rate.
Monthly Notices of the Royal Astronomical Society, 2010
We study the 3D distribution of matter at z ∼ 2 using high-resolution spectra of quasistellar obj... more We study the 3D distribution of matter at z ∼ 2 using high-resolution spectra of quasistellar object (QSO) pairs and simulated spectra drawn from cosmological hydrodynamical simulations. We present a sample of 15 QSOs, corresponding to 21 baselines of angular separations evenly distributed between ∼1 and 14 arcmin, observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory Very Large Telescope (ESO-VLT). The observed correlation functions of the transmitted flux in the H I Lyman α forest transverse to and along the line of sight are in agreement, implying that the distortions in redshift space due to peculiar velocities are relatively small and -within the relatively large error bars -not significant. The clustering signal is significant up to velocity separations of ∼300 km s −1 , corresponding to about 5 h −1 comoving Mpc. Compatibility at the 2σ level has been found both for the autocorrelation and cross-correlation functions and for the set of the cross-correlation coefficients. The analysis focuses in particular on two QSO groups of the sample, the Sextet and the Triplet. Searching for alignments in the redshift space between Lyman α absorption lines belonging to different lines of sight, it has been possible to discover the presence of a wide H I structure extending over about 10 Mpc in comoving space, and give constraints on the sizes of two cosmic underdense regions in the intergalactic medium, which have been detected with a 91 and 86 per cent significance level, respectively, in the Sextet and the Triplet.
We report the discovery of WTS1b, the first extrasolar planet found by the WFCAM Transit Survey. ... more We report the discovery of WTS1b, the first extrasolar planet found by the WFCAM Transit Survey. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby- Eberly Telescope (HET) allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V = 16.13), and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the companion of 3.35 days, a planetary mass of 4.01 ± 0.35 MJ, and a planetary radius of 1.49 +0.16 −0.18 RJ. WTS1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 MJ.
We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey,... more We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ∼ 16 were constructed for ∼ 60 000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, highresolution spectra taken at the Hobby-Eberly Telescope allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01±0.35MJ , and a planetary radius of 1.49 −0.18 RJ . WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5MJ .
Monthly Notices of the Royal Astronomical Society, 2012
We report the discovery of 16 detached M-dwarf eclipsing binaries with J < 16 mag and provide a d... more We report the discovery of 16 detached M-dwarf eclipsing binaries with J < 16 mag and provide a detailed characterisation of three of them, using high-precision infrared light curves from the WFCAM Transit Survey (WTS). Such systems provide the most accurate and model-independent method for measuring the fundamental parameters of these poorly understood yet numerous stars, which currently lack sufficient observations to precisely calibrate stellar evolution models. We fully solve for the masses and radii of three of the systems, finding orbital periods in the range 1.5 < P < 4.9 days, with masses spanning 0.35 − 0.50M ⊙ and radii between 0.38 − 0.50R ⊙ , with uncertainties of ∼ 3.5 − 6.4% in mass and ∼ 2.7 − 5.5% in radius. Close-companions in short-period binaries are expected to be tidally-locked into fast rotational velocities, resulting in high levels of magnetic activity. This is predicted to inflate their radii by inhibiting convective flow and increasing star spot coverage. The radii of the WTS systems are inflated above model predictions by ∼ 3 − 12%, in agreement with the observed trend, despite an expected lower systematic contribution from star spots signals at infrared wavelengths. We searched for correlation between the orbital period and radius inflation by combining our results with all existing M-dwarf radius measurements of comparable precision, but we found no statistically significant evidence for a decrease in radius inflation for longer period, less active systems. Radius inflation continues to exists in non-synchronised systems indicating that the problem remains even for very low activity M-dwarfs. Resolving this issue is vital not only for understanding the most populous stars in the Universe, but also for characterising their planetary companions, which hold the best prospects for finding Earth-like planets in the traditional habitable zone.
We report the discovery of WTS-2 b, a typical hot Jupiter in an unusually close 1.02-day orbit to... more We report the discovery of WTS-2 b, a typical hot Jupiter in an unusually close 1.02-day orbit to a K-dwarf star. This is the second planet to be discovered in the infrared light curves of the WFCAM Transit Survey (WTS) and is only one-and-a-half times the separation from its host star at which is would be destroyed by Roche lobe overflow. The predicted remaining lifetime of the planet is just 38 Myrs, assuming a tidal dissipation quality factor of Q = 10 6 . The magnitude of Q is largely unconstrained by observations, thus WTS-2 b provides a useful calibration point for theories describing how frictional processes within a host star affect the tidal orbital evolution of its companion giant planets. It is expected that stars with large convective envelopes are more efficient at dissipating the orbital energy of the planet, and WTS-2 b provides an observational constraint in the sparsely populated K-dwarf regime. In addition, despite its relatively faint magnitude, the favourable size ratio of the WTS-2 star-planet system and the predicted hot equilibrium temperature of the planet will make it possible to characterise the planet's atmosphere via secondary eclipse measurements using existing ground-based instrumentation.
Monthly Notices of the Royal Astronomical Society, 2012
We report on the discovery of four ultra-short period (P 0.18 days) eclipsing M-dwarf binaries in... more We report on the discovery of four ultra-short period (P 0.18 days) eclipsing M-dwarf binaries in the WFCAM Transit Survey. Their orbital periods are significantly shorter than of any other known main-sequence binary system, and are all significantly below the sharp period cut-off at P ∼ 0.22 days as seen in binaries of earlier type stars. The shortest-period binary consists of two M4 type stars in a P = 0.112 day orbit. The binaries are discovered as part of an extensive search for short-period eclipsing systems in over 260,000 stellar lightcurves, including over 10,000 M-dwarfs down to J=18 mag, yielding 25 binaries with P 0.23 days. In a popular paradigm, the evolution of short period binaries of cool main-sequence stars is driven by loss of angular momentum through magnetised winds. In this scheme, the observed P ∼0.22 day period cut-off is explained as being due to timescales that are too long for lower-mass binaries to decay into tighter orbits. Our discovery of low-mass binaries with significantly shorter orbits implies that either these timescales have been overestimated for M-dwarfs, e.g. due to a higher effective magnetic activity, or that the mechanism for forming these tight M-dwarf binaries is different from that of earlier type main-sequence stars.
Monthly Notices of the Royal Astronomical Society, 2013
The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom In... more The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom Infrared Telescope (UKIRT), designed to discover planets around M dwarfs. The WTS acts as a poor-seeing backup programme for the telescope, and represents the first dedicated wide-field near-infrared transit survey. Observations began in 2007 gathering J-band photometric observations in four (seasonal) fields. In this paper we present an analysis of the first of the WTS fields, covering an area of 1.6 square degrees. We describe the observing strategy of the WTS and the processing of the data to generate lightcurves. We describe the basic properties of our photometric data, and measure our sensitivity based on 950 observations. We show that the photometry reaches a precision of ∼ 4 mmag for the brightest unsaturated stars in lightcurves spanning almost 3 years. Optical (SDSS griz) and near-infrared (UKIRT ZY JHK) photometry is used to classify the target sample of 4600 M dwarfs with J magnitudes in the range 11-17. Most have spectral-types in the range M0-M2. We conduct Monte Carlo transit injection and detection simulations for short period (<10 day) Jupiterand Neptune-sized planets to characterize the sensitivity of the survey. We investigate the recovery rate as a function of period and magnitude for 4 hypothetical star-planet cases: M0-2+Jupiter, M2-4+Jupiter, M0-2+Neptune, M2-4+Neptune. We find that the WTS lightcurves are very sensitive to the presence of Jupiter-sized short-period transiting planets around M dwarfs. Hot Neptunes produce a much weaker signal and suffer a correspondingly smaller recovery fraction. Neptunes can only be reliably recovered with the correct period around the rather small sample (∼ 100) of the latest M dwarfs (M4-M9) in the WTS. The non-detection of a hot-Jupiter around an M dwarf by the WFCAM Transit Survey allows us to place an upper limit of 1.7-2.0 per cent (at 95 per cent confidence) on the planet occurrence rate.
Monthly Notices of the Royal Astronomical Society, 2012
We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey,... more We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ∼ 16 were constructed for ∼ 60 000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, highresolution spectra taken at the Hobby-Eberly Telescope allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01±0.35 M J , and a planetary radius of 1.49 +0.16 −0.18 R J. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 M J .
Monthly Notices of the Royal Astronomical Society, 2014
We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (M P = 1.12M J , R... more We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (M P = 1.12M J , R P = 1.363R J) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ∼ 20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ∼ 40 Myr, assuming a tidal dissipation quality factor of Q ′ ⋆ = 10 6. Q ′ ⋆ is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T shift ∼ 17 seconds after 15 years assuming Q ′ ⋆ = 10 6. A shift less than this would place a direct observational constraint on the lower limit of Q ′ ⋆ in this system. We also report a correction to the previously published expected T shift for WASP-18 b, finding that T shift = 356 seconds after 10 years for Q ′ ⋆ = 10 6 , which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q ′ ⋆ via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straightforward constraints on Q ′ ⋆ will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.
ABSTRACT We have identified photometric white dwarf candidates in the WFCAM transit survey throug... more ABSTRACT We have identified photometric white dwarf candidates in the WFCAM transit survey through a reduced proper motion versus colour approach. Box-fitting with parameters adjusted to detect the unique signature of a white dwarf + planet/brown dwarf transit/eclipse event was performed, as well as looking for variability due to the irradiation of the companions atmosphere by the white dwarf&#39;s high UV flux. We have also performed a simple sensitivity analysis in order to assess the ability of the survey to detect companions to white dwarfs via the transit method.
Monthly Notices of the Royal Astronomical Society, 2013
Halo subdwarfs, metal deficient dwarfs. View project Develop data analysis tools to detect low ma... more Halo subdwarfs, metal deficient dwarfs. View project Develop data analysis tools to detect low mass planets around Sun-like stars using radial velocity technique View project
ABSTRACT The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-... more ABSTRACT The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that difference-photometry light curves present an important improvement for stars with J &gt; 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the box-fitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J ≤ 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes.
Monthly Notices of the Royal Astronomical Society, 2014
ABSTRACT We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12M... more ABSTRACT We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12MJ, Rp=1.363RJ) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ~20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ~40 Myr, assuming a tidal dissipation quality factor of Q&amp;#39;*=10^6. Q&amp;#39;* is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T_shift~17 seconds after 15 years assuming Q&amp;#39;*=10^6. A shift less than this would place a direct observational constraint on the lower limit of Q&amp;#39;* in this system. We also report a correction to the previously published expected T_shift for WASP-18 b, finding that T_shift=356 seconds after 10 years for Q&amp;#39;*=10^6, which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q&amp;#39;* via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straight-forward constraints on Q&amp;#39;* will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.
ABSTRACT The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United K... more ABSTRACT The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom Infrared Telescope (UKIRT). We conduct Monte Carlo transit injection and detection simulations for short period (&lt;10 day) Jupiter-sized planets to characterize the sensitivity of the survey. We investigate the recovery rate as a function of period and magnitude in 2 hypothetical star-planet cases: M0-2 + hot Jupiter, M2-4 + hot Jupiter. We find that the WTS lightcurves are very sensitive to the presence of Jupiter-sized short-period transiting planets around M dwarfs. The non-detection of a hot-Jupiter around an M dwarf by the WFCAM Transit Survey allows us to place a firm upper limit of 1.9 per cent (at 95 per cent confidence) on the planet occurrence rate.
Monthly Notices of the Royal Astronomical Society, 2010
We study the 3D distribution of matter at z ∼ 2 using high-resolution spectra of quasistellar obj... more We study the 3D distribution of matter at z ∼ 2 using high-resolution spectra of quasistellar object (QSO) pairs and simulated spectra drawn from cosmological hydrodynamical simulations. We present a sample of 15 QSOs, corresponding to 21 baselines of angular separations evenly distributed between ∼1 and 14 arcmin, observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory Very Large Telescope (ESO-VLT). The observed correlation functions of the transmitted flux in the H I Lyman α forest transverse to and along the line of sight are in agreement, implying that the distortions in redshift space due to peculiar velocities are relatively small and -within the relatively large error bars -not significant. The clustering signal is significant up to velocity separations of ∼300 km s −1 , corresponding to about 5 h −1 comoving Mpc. Compatibility at the 2σ level has been found both for the autocorrelation and cross-correlation functions and for the set of the cross-correlation coefficients. The analysis focuses in particular on two QSO groups of the sample, the Sextet and the Triplet. Searching for alignments in the redshift space between Lyman α absorption lines belonging to different lines of sight, it has been possible to discover the presence of a wide H I structure extending over about 10 Mpc in comoving space, and give constraints on the sizes of two cosmic underdense regions in the intergalactic medium, which have been detected with a 91 and 86 per cent significance level, respectively, in the Sextet and the Triplet.
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Papers by M. Cappetta