arXiv subjects

G. Torres

Publications and source records attributed to G. Torres.

At least 55 records · Page 3Linked to original sources

arXiv2013

Kepler-62: A five-planet system with planets of 1.4 and 1.6 Earth radii in the Habitable Zone

We present the detection of five planets -- Kepler-62b, c, d, e, and f -- of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii, orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4 and 267.3 days, respectively. The outermost planets (Kepler-62e & -62f) are super-Earth-size (1.25 < planet radius/earth radius < 2.0) planets in the habitable zone (HZ) of their host star, receiving 1.2 +- 0.2 and 0.41 +- 0.05 times the solar flux at Earth's orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 Gyr suggest that both planets could be solid: either with a rocky composition or composed of mostly solid water in their bulk.

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arXiv2012

HAT-P-42b and HAT-P-43b. Two Inflated Transiting Hot Jupiters from the HATNet Survey

First identified from the HATNet wide-field photometric survey, these candidate transiting planets were then followed-up with a variety of photometric observations. Determining the planetary nature of the objects and characterizing the parameters of the systems were mainly done with the SOPHIE spectrograph at the 1.93m telescope at OHP and the TRES spectrograph at the 1.5m telescope at FLWO. HAT-P-42b and HAT-P-43b are typical hot Jupiters on circular orbits around early-G/late-F main sequence host stars, with periods of 4.641876\pm0.000032 and 3.332688\pm0.000016 days, masses of 0.975\pm0.126 and 0.660\pm0.083 Mjup, and radii of 1.277\pm0.149 and 1.283+0.057-0.034 Rjup, respectively. These discoveries increase the sample of planets with measured mean densities, which is needed to constrain theories of planetary interiors and atmospheres. Moreover, their hosts are relatively bright (V < 13.5) facilitating further follow-up studies.

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arXiv2012

Two 'b's in the Beehive: The Discovery of the First Hot Jupiters in an Open Cluster

We present the discovery of two giant planets orbiting stars in Praesepe (also known as the Beehive Cluster). These are the first known hot Jupiters in an open cluster and the only planets known to orbit Sun-like, main-sequence stars in a cluster. The planets are detected from Doppler shifted radial velocities; line bisector spans and activity indices show no correlation with orbital phase, confirming the variations are caused by planetary companions. Pr0201b orbits a V=10.52 late F dwarf with a period of 4.4264 +/- 0.0070 days and has a minimum mass of 0.540 +/- 0.039 Mjup, and Pr0211b orbits a V=12.06 late G dwarf with a period of 2.1451 +/- 0.0012 days and has a minimum mass of 1.844 +/- 0.064 Mjup. The detection of 2 planets among 53 single members surveyed establishes a lower limit on the hot Jupiter frequency of 3.8 (+5.0)(-2.4) % in this metal-rich open cluster. Given the precisely known age of the cluster, this discovery also demonstrates that, in at least 2 cases, giant planet migration occurred within 600 Myr after formation. As we endeavor to learn more about the frequency and formation history of planets, environments with well-determined properties -- such as open clusters like Praesepe -- may provide essential clues to this end.

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arXiv2012

HAT-P-39b--HAT-P-41b: Three Highly Inflated Transiting Hot Jupiters

We report the discovery of three new transiting extrasolar planets orbiting moderately bright (V=11.1 to 12.4) F stars. The planets have periods of P = 2.6940 d to 4.4572 d, masses of 0.60 M_J to 0.80 M_J, and radii of 1.57 R_J to 1.73 R_J. They orbit stars with masses between 1.40 M_sun and 1.51 M_sun. The three planets are members of an emerging population of highly inflated Jupiters with 0.4 M_J < M < 1.5 M_J and R > 1.5 R_J.

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arXiv2012

Dynamical Measurements of the Young Upper Scorpius Triple NTTS 155808-2219

The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was previously identified as a ~17-day period single-lined spectroscopic binary with a tertiary component at 0.21 arcseconds. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, both with and without adaptive optics, we measured radial velocities of all three components. Reanalysis of the single-lined visible light observations, made from 1987 to 1993, also yielded radial velocity detections of the three stars. Combining visible light and infrared data to compute the orbital solution produces orbital parameters consistent with the single-lined solution and a mass ratio of q = 0.78 +/- 0.01 for the SB. We discuss the consistency between our results and previously published data on this system, our radial-velocity analysis with both observed and synthetic templates, and the possibility that this system is eclipsing, providing a potential method for the determination of the stars' absolute masses. Over the ~20 year baseline of our observations, we have measured the acceleration of the SB's center-of-mass in its orbit with the tertiary. Long-term, adaptive optics imaging of the tertiary will eventually yield dynamical data useful for component mass estimates.

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arXiv2012

HAT-P-34b -- HAT-P-37b: Four Transiting Planets More Massive Than Jupiter Orbiting Moderately Bright Stars

We report the discovery of four transiting extrasolar planets (HAT-P-34b - HAT-P-37b) with masses ranging from 1.05 to 3.33 MJ and periods from 1.33 to 5.45 days. These planets orbit relatively bright F and G dwarf stars (from V = 10.16 to V = 13.2). Of particular interest is HAT-P-34b which is moderately massive (3.33 MJ), has a high eccentricity of e = 0.441 +/- 0.032 at P = 5.4526540+/-0.000016 d period, and shows hints of an outer component. The other three planets have properties that are typical of hot Jupiters.

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arXiv2012

HAT-P-38b: A Saturn-Mass Planet Transiting a Late G Star

We report the discovery of HAT-P-38b, a Saturn-mass exoplanet transiting the V=12.56 dwarf star GSC 2314-00559 on a P = 4.6404 d circular orbit. The host star is a 0.89Msun late G-dwarf, with solar metallicity, and a radius of 0.92Rsun. The planetary companion has a mass of 0.27MJ, and radius of 0.82RJ. HAT-P-38b is one of the closest planets in mass and radius to Saturn ever discovered.

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arXiv2011

Absolute dimensions of eclipsing binaries. XXIX. The Am-type systems SW Canis Majoris and HW Canis Majoris

CONTEXT: Accurate physical properties of eclipsing stars provide important constraints on models of stellar structure and evolution, especially when combined with spectroscopic information on their chemical composition. Empirical calibrations of the data also lead to accurate mass and radius estimates for exoplanet host stars. Finally, accurate data for unusual stellar subtypes, such as Am stars, also help to unravel the cause(s) of their peculiarities. AIMS: We aim to determine the masses, radii, effective temperatures, detailed chemical composition and rotational speeds for the Am-type eclipsing binaries SW CMa (A4-5m) and HW CMa (A6m) and compare them with similar normal stars. METHODS: Accurate radial velocities from the Digital Speedometers of the Harvard-Smithsonian Center for Astrophysics were combined with previously published uvby photometry to determine precise physical parameters for the four stars. A detailed abundance analysis was performed from high-resolution spectra obtained with the Nordic Optical Telescope (La Palma). RESULTS: We find the masses of the (relatively evolved) stars in SW CMa to be 2.10 and 2.24 solar masses, with radii of 2.50 and 3.01 solar radii, while the (essentially zero-age) stars in HW CMa have masses of 1.72 and 1.78 solar masses, radii of 1.64 and 1.66 solar radii -- all with errors well below 2%. Detailed atmospheric abundances for one or both components were determined for 14 elements in SW CMa ([Fe/H] = +0.49/+0.61 dex) and 16 in HW CMa ([Fe/H] = +0.33/+0.32 dex); both abundance patterns are characteristic of metallic-line stars. Both systems are well fit by current stellar evolution models for assumed bulk abundances of [Fe/H] = +0.05 and +0.23, respectively ([alpha/Fe] = 0.0), and ages of about 700 Myr and 160 Myr.

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arXiv2011

A Surprising Dynamical Mass for V773~Tau~B

We report on new high-resolution imaging and spectroscopy on the multiple T Tauri star system V773 Tau over the 2003 -- 2009 period. With these data we derive relative astrometry, photometry between the A and B components, and radial velocity (RV) of the A-subsystem components. Combining these new data with previously published astrometry and RVs, we update the relative A-B orbit model. This updated orbit model, the known system distance, and A subsystem parameters yields a dynamical mass for the B component for the first time. Remarkably the derived B dynamical mass is in the range of 1.7 -- 3.0 M$_\sun$. This is much higher than previous estimates, and suggests that like A, B is also a multiple stellar system. Among these data, spatially-resolved spectroscopy provide new insight into the nature of the B component. Similar to A, these near-IR spectra indicate that the dominant source in B is of mid-K spectral type. If B is in fact a multiple star system as suggested by the dynamical mass estimate, the simplest assumption is that B is composed of similar $\sim$ 1.2 M$_\sun$ PMS stars in a close ($<$ 1 AU) binary system. This inference is supported by line-shape changes in near-IR spectroscopy of B, tentatively interpreted as changing RV among components in V773 Tau B. Relative photometry indicate that B is highly variable in the near-IR. The most likely explanation for this variability is circum-B material resulting in variable line-of-sight extinction. The distribution of this material must be significantly affected by both the putative B multiplicity, and the A-B orbit.

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arXiv2011

Report of IAU Commission 30 on Radial Velocities (2009-2012)

Brief summaries are given of the following subjects of interest to IAU Commission 30: Large-scale radial-velocity surveys; The role of radial-velocity measurements in studies of stellar angular momentum evolution and stellar age; Radial velocities in open clusters; Toward higher radial-velocity precision; High-precision radial velocities applied to studies of binary stars; Doppler boosting effect; Working groups (Stellar radial velocity bibliography; Radial velocity standards; Catalogue of orbital elements of spectroscopic binaries [SB9]).

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arXiv2011

The architecture of the hierarchical triple star KOI 928 from eclipse timing variations seen in Kepler photometry

We present a hierarchical triple star system (KIC 9140402) where a low mass eclipsing binary orbits a more massive third star. The orbital period of the binary (4.98829 Days) is determined by the eclipse times seen in photometry from NASA's Kepler spacecraft. The periodically changing tidal field, due to the eccentric orbit of the binary about the tertiary, causes a change in the orbital period of the binary. The resulting eclipse timing variations provide insight into the dynamics and architecture of this system and allow the inference of the total mass of the binary ($0.424 \pm 0.017 \text{M}_\odot$) and the orbital parameters of the binary about the central star.

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arXiv2011

Young Exoplanet Transit Initiative (YETI)

We present the Young Exoplanet Transit Initiative (YETI), in which we use several 0.2 to 2.6m telescopes around the world to monitor continuously young (< 100 Myr), nearby (< 1 kpc) stellar clusters mainly to detect young transiting planets (and to study other variability phenomena on time-scales from minutes to years). The telescope network enables us to observe the targets continuously for several days in order not to miss any transit. The runs are typically one to two weeks long, about three runs per year per cluster in two or three subsequent years for about ten clusters. There are thousands of stars detectable in each field with several hundred known cluster members, e.g. in the first cluster observed, Tr-37, a typical cluster for the YETI survey, there are at least 469 known young stars detected in YETI data down to R=16.5 mag with sufficient precision of 50 milli-mag rms (5 mmag rms down to R=14.5 mag) to detect transits, so that we can expect at least about one young transiting object in this cluster. If we observe 10 similar clusters, we can expect to detect approximately 10 young transiting planets with radius determinations. The precision given above is for a typical telescope of the YETI network, namely the 60/90-cm Jena telescope (similar brightness limit, namely within +/-1 mag, for the others) so that planetary transits can be detected. For planets with mass and radius determinations, we can calculate the mean density and probe the internal structure. We aim to constrain planet formation models and their time-scales by discovering planets younger than 100 Myr and determining not only their orbital parameters, but also measuring their true masses and radii, which is possible so far only by the transit method. Here, we present an overview and first results. (Abstract shortened)

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arXiv2011

HAT-P-32b and HAT-P-33b: Two Highly Inflated Hot Jupiters Transiting High-Jitter Stars

We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V=11.289 star GSC 3281-00800, with a period P = 2.150008 d. The stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high velocity jitter (~80m/s). Assuming a circular orbit, the star has a mass of 1.16+-0.04 M_sun, and radius of 1.22+-0.02 R_sun, while the planet has a mass of 0.860+-0.164 MJ, and a radius of 1.789+-0.025 RJ. When the eccentricity is allowed to vary, the best-fit model results in a planet which is close to filling its Roche Lobe. Including the constraint that the planet cannot exceed its Roche Lobe results in the following best-fit parameters: e = 0.163+-0.061, Mp = 0.94+-0.17 MJ, Rp = 2.04+-0.10 RJ, Ms = 1.18+0.04-0.07 M_sun and Rs = 1.39+-0.07 R_sun. The second planet, HAT-P-33b, orbits the bright V=11.188 star GSC 2461-00988, with a period P = 3.474474 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter (~50m/s). In this case spectral line bisector spans are significantly anti-correlated with the radial velocity residuals, and we use this correlation to reduce the residual rms to ~35m/s. We find the star has a mass of either 1.38+-0.04 M_sun or 1.40+-0.10 M_sun, and a radius of either 1.64+-0.03 R_sun or 1.78+-0.28 R_sun, while the planet has a mass of either 0.762+-0.101 MJ or 0.763+-0.117 MJ, and a radius of either 1.686+-0.045 RJ or 1.827+-0.290 RJ, for an assumed circular orbit or for the best-fit eccentric orbit respectively. Due to the large bisector span variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date.

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arXiv2011

HAT-P-28b and HAT-P-29b: Two Sub-Jupiter Mass Transiting Planets

We present the discovery of two transiting exoplanets. HAT-P-28b orbits a V=13.03 G3 dwarf star with a period P = 3.2572 d and has a mass of 0.63 +- 0.04 MJ and a radius of 1.21 + 0.11 -0.08 RJ yielding a mean density of 0.44 +- 0.09 g cm-3. HAT-P-29b orbits a V=11.90 F8 dwarf star with a period P = 5.7232 d and has a mass of 0.78 +0.08 -0.04 MJ and a radius of 1.11 +0.14 -0.08 RJ yielding a mean density of 0.71 +- 0.18 g cm-3. We discuss the properties of these planets in the context of other known transiting planets.

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arXiv2011

HAT-P-30b: A transiting hot Jupiter on a highly oblique orbit

We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V=10.419 dwarf star GSC 0208-00722. The planet has a period P=2.810595+/-0.000005 d, transit epoch Tc = 2455456.46561+/-0.00037 (BJD), and transit duration 0.0887+/-0.0015 d. The host star has a mass of 1.24+/-0.04 Msun, radius of 1.21+/-0.05 Rsun, effective temperature 6304+/-88 K, and metallicity [Fe/H] = +0.13+/-0.08. The planetary companion has a mass of 0.711+/-0.028 Mjup, and radius of 1.340+/-0.065 Rjup yielding a mean density of 0.37+/-0.05 g cm^-3. We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect we measure an angle of λ= 73.5+/-9.0 deg between the sky projections of the planet's orbit normal and the star's spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with Teff > 6250 K.

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arXiv2011

Planets from the HATNet project

We summarize the contribution of the HATNet project to extrasolar planet science, highlighting published planets (HAT-P-1b through HAT-P-26b). We also briefly discuss the operations, data analysis, candidate selection and confirmation procedures, and we summarize what HATNet provides to the exoplanet community with each discovery.

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arXiv2010

Blend Analysis of HATNet Transit Candidates

Candidate transiting planet systems discovered by wide-field ground-based surveys must go through an intensive follow-up procedure to distinguish the true transiting planets from the much more common false positives. Especially pernicious are configurations of three or more stars which produce radial velocity and light curves that are similar to those of single stars transited by a planet. In this contribution we describe the methods used by the HATNet team to reject these blends, giving a few illustrative examples.

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arXiv2010

HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars

We report the discovery of two new transiting extrasolar planets. HAT-P-18b orbits the V=12.759 K2 dwarf star GSC 2594-00646, with a period P=5.508023+-0.000006 d, transit epoch Tc=2454715.02174+-0.00020 (BJD), and transit duration 0.1131+-0.0009 d. The host star has a mass of 0.77+-0.03 Msun, radius of 0.75+-0.04 Rsun, effective temperature 4803+-80 K, and metallicity [Fe/H]=+0.10+-0.08. The planetary companion has a mass of 0.197+-0.013 Mjup, and radius of 0.995+-0.052 Rjup yielding a mean density of 0.25+-0.04 g cm-3. HAT-P-19b orbits the V=12.901 K1 dwarf star GSC 2283-00589, with a period P=4.008778+-0.000006 d, transit epoch Tc=2455091.53417+-0.00034 (BJD), and transit duration 0.1182+-0.0014 d. The host star has a mass of 0.84+-0.04 Msun, radius of 0.82+-0.05 Rsun, effective temperature 4990+-130 K, and metallicity [Fe/H]=+0.23+-0.08. The planetary companion has a mass of 0.292+-0.018 Mjup, and radius of 1.132+-0.072 Rjup yielding a mean density of 0.25+-0.04 g cm-3. The radial velocity residuals for HAT-P-19 exhibit a linear trend in time, which indicates the presence of a third body in the system. Comparing these observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are each consistent with a hydrogen-helium dominated gas giant planet with negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b in an emerging group of low-density Saturn-mass planets, with negligible inferred core masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar metallicity. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

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