EDP Sciences
Free Access
Issue
A&A
Volume 580, August 2015
Article Number A63
Number of page(s) 13
Section Planets and planetary systems
DOI https://doi.org/10.1051/0004-6361/201526069
Published online 03 August 2015

© ESO, 2015

1. Introduction

After 20 years from when human knowledge crossed the borders of the solar system and found a planet orbiting another main-sequence star (Mayor & Queloz 1995), we can now count more than 1800 exoplanets in our Galaxy, and marvel how physically varied and intriguing most of them are. The first class of unexpected planets with which we faced is composed by the so-called hot Jupiters, i.e. giant gaseous planets in close orbits around their host stars, able to perform a complete orbit in a relatively short time (~0.1–10 days). Even though they are rarer than small-size rocky and Neptunian planets (Fressin et al. 2013; Dressing & Charbonneau 2013; Petigura et al. 2013), there are numerous reasons that make them very interesting to study, especially those that transit their parent stars. Indeed, since hot Jupiters are more massive and larger than rocky planets, it is possible to measure their physical parameters with much better accuracy: in primis mass and radius, as well as their spin-orbit alignment (from the Rossiter-McLaughlin effect), their thermal flux and reflected light (from occultations and phase curve), the chemical composition of their atmosphere (from emission and transmission spectra), etc. Although all these parameters are accessible, even with moderate-sized ground-based telescopes, there are various aspects of the hot-Jupiter population that are not well understood. We have not find, for example, any convincing way to group them in classes based on some of their features (e.g. Hansen & Barman 2007; Fortney et al. 2008; Schlaufman 2010; Madhusudhan 2012). It has also been difficult to determine the physical mechanisms that regulate the formation, accretion, evolution and cause the migration of giant planets from the snow line (~3 au) up to roughly 0.01 au from their host stars. In this context, several scaling laws have been suggested between their parameters (e.g. Southworth et al. 2007; Knutson et al. 2010; Hartman 2010), but none seems to generally apply to all planets.

Answering the above questions is possible only by enlarging the sample at our disposal, in particular, the regions of the parameter space that are currently deserted because of observational biases. In the last three lustra, ground-based transit surveys have played a major role in exoplanet detection and, thus, in the growth of our scientific knowledge about planetary systems. In a fair competition with other teams (e.g. HATNet: Bakos et al. 2004; WASP: Pollacco et al. 2006; KELT: Pepper et al. 2007; MEARTH: Charbonneau et al. 2009; QES: Alsubai et al. 2013; APACHE: Sozzetti et al. 2013; NGTS: Wheatley et al. 2013), we are undertaking the HATSouth project, which consists of monitoring millions of stars in the southern sky to look for new exoplanet transit signals. Our survey is carried out by a network of six telescope systems, employing 24 astrographs, distributed over three continents (South America, Africa, and Australia), thus increasing the sensitive to long-period (>10 days) planets (Bakos et al. 2013).

Here we present two new transiting extrasolar planets: HATS-13b and HATS-14b. The paper is organized as follows: in Sect. 2 we summarize the detection of the photometric transit signal and the subsequent spectroscopic and photometric observations of each star to confirm the planets. In Sect. 3 we analyze the data to rule out false positive scenarios, and to determine the stellar and planetary parameters. Our findings are summarized and discussed in Sect. 4.

Table 1

Summary of photometric observations.

thumbnail Fig. 1

Phase-folded unbinned HATSouth light curves for HATS-13 (left) and HATS-14 (right). In each case we show two panels. The top panel shows the full light curve, while the bottom panel shows the light curve zoomed-in on the transit. The solid lines show the model fits to the light curves. The dark filled circles in the bottom panels show the light curves binned in phase with a bin size of 0.002.

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2. Observations

2.1. Photometric detection

The modus operandi of the HATSouth survey is comprehensively described in Bakos et al. (2013). In brief, HATSouth is a network of completely automated wide-field telescopes, consisting of six homogeneous units located at three different places in the southern hemisphere, i.e. Las Campanas Observatory (LCO) in Chile, the HESS site in Namibia, and Siding Spring Observatory (SSO) in Australia. Each unit is equipped with four 18 cm f/ 2.8 Takahashi astrographs, each working in pairs with Apogee U16M Alta 4k × 4k CCD cameras, with a total mosaic field-of-view (FOV) on the sky of 8° × 8° at a scale of 3.7 arcsec pixel-1. Observations are performed through a Sloan-r filter with an exposure time of four minutes. Scientific images are automatically calibrated and light curves are extracted by aperture photometry. They are then treated with decorrelation and detrending algorithms1 and finally run through with BLS (Box-fitting Least Squares; Kovács et al. 2002) to find periodic signals by transiting exoplanets.

The stars HATS-13 (aka 2MASS 21075075-2605479; α = 21h07m50.88s, δ = −26°05′48.0″; J2000) and HATS-14 (aka 2MASS 20525171-2541144; α = 20h52m51.60s, δ = −25°41′14.4″; J2000) are two moderately bright (V = 13.89 mag and V = 13.79 mag, respectively) stars. They were monitored between Nov. 2009 and Sept. 2010 by three of the HATSouth units, which collected more than 10 000 images for both of them. Details of the observations are reported in Table 1. The corresponding light curves, folded with a period of P ~ 3.04 and 2.77 days are plotted in Fig. 1, both clearly showing transiting-planet signals with depths of ~2% and ~1%, respectively.

2.2. Spectroscopic observations

After being selected as HATSouth planet candidates, HATS-13 and HATS-14 underwent spectral reconnaissance through low- and medium-resolution observations with the Wide Field Spectrograph (WiFeS; Dopita et al. 2007) mounted on the ANU 2.3 m telescope at SSO. This first step is very useful in the planet confirmation process because it can immediately rule out possible false positive cases, mainly caused by giant stars, F-M binary systems, and blending with faint eclipsing-binary systems.

Using WiFES, we identified both the targets as dwarf stars. HATS-13 and HATS-14 were then accurately monitored with an array of telescopes equipped with high-resolution spectrographs, covering wide ranges of optical wavelengths, to look for possible radial-velocity (RV) variations compatible with the presence of planetary companions.

Four and five spectra were observed in May 2012 for HATS-13 and HATS-14, respectively, with CYCLOPS mounted on the 3.9 m Anglo-Australian Telescope at SSO. A better RV accuracy was achieved between May and November 2012 thanks to FEROS (Kaufer & Pasquini 1998) on the MPG 2.2 m telescope at the ESO Observatory in La Silla and Coralie (Queloz et al. 2001) on the Euler 1.2 m telescope, also located in La Silla. In total, with these two instruments, we collected 32 and 31 spectra for HATS-13 and HATS-14, respectively, with an average precision of some tens of meters per second. Information about these spectropic observations are summarized in Table 2, yet we did not use all the spectra in the analysis, as some of them were discarded because of high-sky contamination. Additional details about the instruments and data-reduction processes are exhaustively discussed in previous works of the HATS team (i.e. Penev et al. 2013; Mohler-Fischer et al. 2013; Bayliss et al. 2013). In particular, Coralie and FEROS spectra were reduced using the new procedure described in Jordán et al. (2014) and Brahm et al. (2015).

To better characterize the periodic signal of the RV variation of HATS-13, it was necessary to observe this target with higher RV precision. On September 2012, we used the High Dispersion Spectrograph (HDS; Noguchi et al. 2002) on the Subaru telescope at the Observatory of Mauna Kea, Hawaii. Observations were spread over four nights and performed in a way similar to those for HATS-5 (Zhou et al. 2014), i.e. using a slit and a set-up, which guaranteed a wavelength-range coverage of 3500–6200 Å, with a resolution of R = 60 000. Ten spectra were taken using an I2 cell and another three without it (Table 2). All of HDS observations were reduced following Sato et al. (2002, 2012).

All the RV measurements, extracted from the spectra discussed here, are listed in Tables A.2 and A.3. Phased RV and BS measurements are shown for each system in Fig. 2.

Table 2

Summary of spectroscopy observations.

thumbnail Fig. 2

Phased high-precision RV measurements for HATS-13 (left), and HATS-14 (right) from HDS (filled circles), FEROS (open triangles), Coralie (filled triangles), and CYCLOPS (stars). In each case we show three panels. The top panel shows the phased measurements together with our best-fit model (see Table 4) for each system. Zero-phase corresponds to the time of mid-transit. The center-of-mass velocity has been subtracted. The second panel shows the velocity O–C residuals from the best fit. The error bars include the jitter terms listed in Table 4 added in quadrature to the formal errors for each instrument. The third panel shows the bisector spans (BS) with the mean value subtracted. Note the different vertical scales of the panels.

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2.3. Photometric follow-up observations

High-quality photometric follow-up observations of additional transit events of the two targets were subsequently performed with larger telescopes than the HATSouth units. This is also an important step because it allows us to have a precise light-curve anatomy of the planetary transits (depth, duration and sharpness) and, by constraining the eccentricity via RV variations, measure the mean density of the parent stars with high accuracy and with no systematic errors (Seager & Mallén-Ornelas 2003). As we see in Sect. 3.1, the knowledge of the stellar mean density is a very useful constraint for the determination of the other physical parameters of the two systems.

Concerning HATS-13, two complete and two incomplete transits were observed using the MPG 2.2 m, CTIO 0.9 m, and PEST 0.3 m telescopes. Two complete transit events were successfully monitored for HATS-14 with the MPG 2.2 m and PEST telescopes. Relevant information about these observations (i.e. dates, cadence, filter, precision) are reported in Table 1. In particular, the MPG 2.2 m telescope is equipped with GROND, a multi-imaging camera, able to observe a FOV of 5.4′ × 5.4′ in four different filters (similar to Sloan g,r,i,z) simultaneously (Greiner et al. 2008). Details of the GROND camera and data reduction are reported in Penev et al. (2013) and Mohler-Fischer et al. (2013), while studies of the accuracy and signal-to-noise ratio (S/N) expectations for this instrument were done by Pierini et al. (2012) and Mancini et al. (2014). The PEST telescope and data reduction method are discussed in Bayliss et al. (2013). The same information for the CTIO 0.9 m telescope have been reported by Hartman et al. (2015).

The light curves for HATS-13 and HATS-14 are shown in Figs. 3 and 4, respectively. The corresponding data, including those from the HATS units, are given in Table 3.

thumbnail Fig. 3

Left panel: unbinned transit light curves for HATS-13. The light curves have been corrected for quadratic trends in time fitted simultaneously with the transit model. The dates of the events, filters, and instruments used are indicated. Light curves following the first are displaced vertically for clarity. Our best fit from the global modelling described in Sect. 3.3 is shown by the solid lines. Right panel: residuals from the fits are displayed in the same order as the left curves. The error bars represent the photon and background shot noise, plus the readout noise.

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thumbnail Fig. 4

Similar to Fig. 3; here we show the follow-up light curves for HATS-14.

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3. Analysis

Based on the data previously presented, this section is dedicated to the derivation of the physical parameters of the HATS-13 and HATS-14 planet hosts.

3.1. Properties of the parent stars

To determine the atmospheric properties (metallicity, effective temperature and surface gravity) of the stars HATS-13 and HATS-14, we used 17 and 14 high-resolution FEROS spectra, respectively. This was accomplished by using the new routine ZASPE (Zonal Atmospherical Stellar Parameter Estimator), which is fully described in Brahm et al. (2015). The other principal stellar parameters (like mass, radius, luminosity, age, etc.) and corresponding uncertainties were estimated thanks to a Markov chain Monte Carlo (MCMC) global analysis of our photometric and spectroscopic data, following the methodology of Sozzetti et al. (2007). This is based on stellar effective temperature Teff , which we determined with ZASPE, the stellar mean density ρ, estimated from the light-curve fitting (see Sect. 3.3), and from the Yonsei-Yale (YY; Yi et al. 2001) evolutionary tracks.

Table 3

Stellar parameters for HATS-13 and HATS-14.

Table 4

Orbital and planetary parameters for HATS-13b and HATS-14b.

Spanning a range of reliable values for the metallicity, we calculated the YY isochrones for each of the two systems over a wide a range of ages and compared the resulting Teff and ρ with those estimated from the data. The best agreement returned the values of the other stellar parameters. In particular, the better estimation of the stellar logarithmic surface gravity (log g= 4.524 ± 0.017 for HATS-13 and log g= 4.484 ± 0.020 for HATS-14), was used for a second iteration of ZASPE, by fixing these values, to revise the other atmospheric parameters.

The stellar properties that we derived are reported in Table 3, along with their 1σ uncertainties. Model isochrones are shown in the panels of Fig. 5 in which the positions of the two stars in the Teff ρ diagram are also marked.

We found that both the stars are slightly smaller and less massive than the Sun, with parameters listed in Table 3. In particular, with Teff = 5523 ± 69 K, M = 0.962 ± 0.029 M, R = 0.887 ± 0.019 R, BV = 0.80 ± 0.03, VH = 1.84 ± 0.04, HATS-13 is a G5 V star, whereas HATS-14, characterized by Teff = 5346 ± 60 K, M = 0.967 ± 0.024 M, , BV = 0.83 ± 0.2, VH = 1.87 ± 0.3, has a spectral class close to the K/G transition (Pecaut & Mamajek 2013). The preferred metallicities are [ Fe / H ] = 0.050 ± 0.060 and [ Fe / H ] = 0.330 ± 0.060 for HATS-13 and HATS-14, respectively.

Table 3 also shows the magnitudes of the two stars in the optical bands (taken from APASS as listed in the UCAC 4 catalogue; Zacharias et al. 2012) and in the NIR bands (from 2MASS). We compared these values with the predicted magnitudes in each filter from the isochrones, determining the distance of the two stars, which is 476 ± 12 pc for HATS-13 and 513 ± 14 pc for HATS-14. Here the extinction was estimated assuming an RV = 3.1 law from Cardelli et al. (1989).

3.2. Excluding blend scenarios

To rule out the possibility that either HATS-13or HATS-14is a blend between an eclipsing binary and a third star (potentially in the foreground or background of the binary), we carried out a blend analysis following Hartman et al. (2012). We find that for both objects the single star with a transiting planet model fits the light curves and broad-band photometric colour data better than a blended eclipsing binary model. For HATS-13the best-fit transiting planet model is preferred with 2σ confidence over the best-fit blend model, while for HATS-14the best-fit transiting planet model is preferred with 4σ confidence. Moreover, we find that any blend model that comes close to fitting the photometric data would have been easily detected as a composite object based on the spectroscopic data (there would be two clear peaks in the CCFs, and the RVs from the highest peak would vary by more than 1 km s-1, as would the bisector spans). We conclude that both HATS-13and HATS-14are transiting planet systems. We cannot, however, rule out the possibility that either object is a blend between a transiting planet system and a third star that is fainter than the planet-hosting star. For HATS-13 we find that including a physical stellar companion with a mass greater than 0.84M leads to a worse fit than not including the companion, however, even a companion up to the mass of the primary star cannot be ruled out with greater than 5σ confidence. For HATS-14we can rule out companions with a mass greater than 0.92 M with greater than 5σ confidence, while including a companion with a mass greater than 0.5 M leads to a worse fit of the data than a non-composite system. High-resolution imaging and/or long-term RV monitoring are needed to determine if either source has a stellar companion. For the remainder of the paper, we assume both objects are single stars with transiting planets, however, if either system has a stellar companion, the true radius and mass of the planet would be larger than what we infer here (Daemgen et al. 2009).

3.3. Global modelling of the data

We modelled the HATSouth photometry, the follow-up photometry, and the high-precision RV measurements following Pál et al. (2008), Bakos et al. (2010), Hartman et al. (2012). We fit Mandel & Agol (2002) transit models to the light curves, allowing for a dilution of the HATSouth transit depth as a result of blending from neighbouring stars and over-correction by the trend-filtering method. For the follow-up light curves we include a quadratic trend in time in our model for each event to correct for systematic errors in the photometry. We fit Keplerian orbits to the RV curves allowing the zero-point for each instrument to vary independently in the fit, and allowing for an effective RV jitter which we also vary as a free parameter for each instrument. This is done following the method described in Hartman et al. (2012) and accounts for any additional noise in the RVs, either instrumental or astrophysical in origin, which is not already included in the RV uncertainties. For a further discussion of this effective jitter see Baluev (2009). We used a differential evolution Markov Chain Monte Carlo procedure to explore the fitness landscape and to determine the posterior distribution of the parameters. For HATS-14, the scatter in the Coralie and FEROS RV residuals is consistent with the uncertainties (see Fig. 2), so our modelling finds jitter values of 0 for both instruments.

The resulting parameters for each system are listed in Table 4. They were determined assuming circular orbits. We have also explored non-zero eccentricities, by varying and in the fitting process, e being the eccentricity and ω the argument of the periastron. In this case, we got that e< 0.181 ( < 0.142) at 95% confidence for HATS-3 (HATS-4).

thumbnail Fig. 5

Model isochrones from Yi et al. (2001) for the measured metallicities of HATS-13(left panel) and HATS-14(right panel). In each case, we show models for ages of 0.2 Gyr and 1.0 to 14.0 Gyr in 1.0 Gyr increments (ages increasing from left to right). The adopted values of Teff and ρ are shown together with their 1σ and 2σ confidence ellipsoids. The initial values of Teff and ρ from the first ZASPE and light curve analyses are represented with a triangle.

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thumbnail Fig. 6

Left panel: masses and radii of the known transiting extrasolar planets. The grey points denote values taken from TEPCat. Their error bars have been suppressed for clarity. HATS-13b and HATS-14b are shown in red points with error bars. Dotted lines show where density is 2.5, 1.0, 0.5, 0.25 and 0.1 ρJ. Right panel: the mass-density diagram of the currently known transiting exoplanets (taken from TEPCat). Again HATS-13b and HATS-14b are shown in red points with error bars. Four planetary models with various core masses (10, 25, 50, and 100 Earth mass) and another without a core (Fortney et al. 2007) are plotted for comparison.

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Table 4 indicates that, while HATS-14b has mass (Mp = 1.071 ± 0.070 MJ) and size () slightly larger than those of Jupiter, HATS-13 is much less massive (only Mp = 0.543 ± 0.072 MJ), but bloated (Rp = 1.212 ± 0.035 RJ). The above values lead to mean densities that are extremely different, i.e. ρp = 0.377 ± 0.058 g cm-3 for HATS-13b and  g cm-3 for HATS-14b. Curiously, even though they have different physical properties, their orbital periods (3.04 and 2.77 days) and separation from the own host star (0.041 and 0.038 au) are similar to each other.

4. Discussion and conclusions

After having monitored more than 3 million stars in its almost first five years of life, the HATSouth survey is now entering in a phase of continuous flow of exoplanet discoveries. We have presented two new hot-Jupiter transiting planets, HATS-13b and HATS-14b, both orbiting around slightly metal rich, mild main-sequence stars with a period of ~3 days. Their detection is robustly based on extensive photometric observations and numerous RV measurements, as we described in the previous sections.

Orbiting around similar stars at similar distances, the stellar radiation that the two planets receive are quite similar, i.e. ~5.4 and ~6.0 × 108 erg s-1 cm-2 for HATS-13b and HATS-14b, respectively, putting them in the pL class, according to the terminology of Fortney et al. (2008). Based on their equilibrium temperature and surface gravity (see Table 4), their atmospheric scale heights2 are ~740 and ~230 km, respectively. Hence, HATS-13b would be a suitable target for transmission-spectroscopy follow-up observations. Since it is a pL planet, we do not expect that its atmosphere hosts a large amount of absorbing molecules in the optical wavelength range (Fortney et al. 2010). However, past observations of transiting gas giants reveal that a wide diversity (e.g. Wakeford & Sing 2015) and a more sophisticated classification scheme for hydrogen-dominated exoplanetary atmospheres is necessary (see Madhusudhan et al. 2014, and references therein).

If we look at their Safranov number, HATS-13b and HATS-14b would belong to separate classes of planets and should have had quite different evolution, migration and evaporation processes (Hansen & Barman 2007). Actually, even though the parent stars have similar masses, their inferred ages differ by a factor of ~2 (see Table 3). Figure 6 shows the positions of the two new HATS planets in the current planet mass-radius plot (left panel) and planet mass-density plot (right panel). They are shown together with those of all the other known transiting exoplanets (data taken from the TEPCat catalogue3 on March 9, 2015). It can be noted immediately that they occupy two quite different positions in both the diagrams. In the left panel, HATS-14b appears to be a bit out from the population of Jupiters with masses near 1 MJ, whereas HATS-13b is in the middle of a cluster of planets with masses around 0.5 MJ and inflated radii. In addition to the position of the planets, the right panel also shows 3.2 Gyr isochrones of giant planets, with various values of core mass, at 0.045 au orbital separation from a solar analogue (Fortney et al. 2007). The plot suggests that HATS-13b should be a core-free planet, while HATS-14 should have a massive core of ~50 M. We stress that, although we cannot rule out the possibility that HATS-14 has a stellar companion, which is diluting the transit (see discussion in Sect. 3.2), our 3σ upper limit on the radius of the planet under this scenario is 1.11 RJ.


1

External Parameter Decorrelation (EPD; Bakos et al. 2010); Trend Filtering Algorithm (TFA; Kovács et al. 2005).

2

The atmospheric scale height is defined as H = kT/μmgp, where k is the Boltzmann’s constant, T is the atmospheric temperature, μm the mean molecular weight, gp is the planetary surface gravity.

3

The Transiting Extrasolar Planet Catalogue (TEPCat) is available at http://www.astro.keele.ac.uk/jkt/tepcat/ (Southworth 2011).

Acknowledgments

Development of the HATSouth project was funded by NSF MRI grant NSF/AST-0723074, operations have been supported by NASA grants NNX09AB29G and NNX12AH91H, and follow-up observations receive partial support from grant NSF/AST-1108686. A.J. acknowledges support from FONDECYT project 1130857, BASAL CATA PFB-06, and project IC120009 “Millennium Institute of Astrophysics (MAS)” of the Millenium Science Initiative, Chilean Ministry of Economy. R.B. and N.E. are supported by CONICYT- PCHA/Doctorado Nacional. R.B. and N.E. acknowledge additional support from project IC120009 “Millenium Institute of Astrophysics (MAS)” of the Millennium Science Initiative, Chilean Ministry of Economy. V.S. acknowledges support form BASAL CATA PFB-06. K.P. acknowledges support from NASA grant NNX13AQ62G. This work is based on observations made with telescopes at the ESO Observatory of La Silla. This paper also uses observations obtained with facilities of the Las Cumbres Observatory Global Telescope. Work at the Australian National University is supported by ARC Laureate Fellowship Grant FL0992131. We acknowledge the use of the AAVSO Photometric All-Sky Survey (APASS), funded by the Robert Martin Ayers Sciences Fund, and the SIMBAD database, operated at CDS, Strasbourg, France. Operations at the MPG 2.2 m Telescope are jointly performed by the Max Planck Gesellschaft and the European Southern Observatory. The imaging system GROND has been built by the high-energy group of MPE in collaboration with the LSW Tautenburg and ESO. We thank Régis Lachaume for his technical assistance during the observations at the MPG 2.2 m Telescope. We are grateful to P. Sackett for her help in the early phase of the HATSouth project. The reduced light curves presented in this work will be made available at the CDS (http://cdsweb.u-strasbg.fr/). We acknowledge the use of the following internet-based resources: the ESO Digitized Sky Survey; the TEPCat catalog; the SIMBAD data base operated at CDS, Strasbourg, France; and the arXiv scientific paper preprint service operated by Cornell University.

References

Online material

Appendix A: Supplementary tables

Table A.1

Light curve data for HATS-13and HATS-14.

Table A.2

Relative radial velocities and bisector spans for HATS-13.

Table A.3

Relative radial velocities and bisector spans for HATS-14.

All Tables

Table 1

Summary of photometric observations.

Table 2

Summary of spectroscopy observations.

Table 3

Stellar parameters for HATS-13 and HATS-14.

Table 4

Orbital and planetary parameters for HATS-13b and HATS-14b.

Table A.1

Light curve data for HATS-13and HATS-14.

Table A.2

Relative radial velocities and bisector spans for HATS-13.

Table A.3

Relative radial velocities and bisector spans for HATS-14.

All Figures

thumbnail Fig. 1

Phase-folded unbinned HATSouth light curves for HATS-13 (left) and HATS-14 (right). In each case we show two panels. The top panel shows the full light curve, while the bottom panel shows the light curve zoomed-in on the transit. The solid lines show the model fits to the light curves. The dark filled circles in the bottom panels show the light curves binned in phase with a bin size of 0.002.

Open with DEXTER
In the text
thumbnail Fig. 2

Phased high-precision RV measurements for HATS-13 (left), and HATS-14 (right) from HDS (filled circles), FEROS (open triangles), Coralie (filled triangles), and CYCLOPS (stars). In each case we show three panels. The top panel shows the phased measurements together with our best-fit model (see Table 4) for each system. Zero-phase corresponds to the time of mid-transit. The center-of-mass velocity has been subtracted. The second panel shows the velocity O–C residuals from the best fit. The error bars include the jitter terms listed in Table 4 added in quadrature to the formal errors for each instrument. The third panel shows the bisector spans (BS) with the mean value subtracted. Note the different vertical scales of the panels.

Open with DEXTER
In the text
thumbnail Fig. 3

Left panel: unbinned transit light curves for HATS-13. The light curves have been corrected for quadratic trends in time fitted simultaneously with the transit model. The dates of the events, filters, and instruments used are indicated. Light curves following the first are displaced vertically for clarity. Our best fit from the global modelling described in Sect. 3.3 is shown by the solid lines. Right panel: residuals from the fits are displayed in the same order as the left curves. The error bars represent the photon and background shot noise, plus the readout noise.

Open with DEXTER
In the text
thumbnail Fig. 4

Similar to Fig. 3; here we show the follow-up light curves for HATS-14.

Open with DEXTER
In the text
thumbnail Fig. 5

Model isochrones from Yi et al. (2001) for the measured metallicities of HATS-13(left panel) and HATS-14(right panel). In each case, we show models for ages of 0.2 Gyr and 1.0 to 14.0 Gyr in 1.0 Gyr increments (ages increasing from left to right). The adopted values of Teff and ρ are shown together with their 1σ and 2σ confidence ellipsoids. The initial values of Teff and ρ from the first ZASPE and light curve analyses are represented with a triangle.

Open with DEXTER
In the text
thumbnail Fig. 6

Left panel: masses and radii of the known transiting extrasolar planets. The grey points denote values taken from TEPCat. Their error bars have been suppressed for clarity. HATS-13b and HATS-14b are shown in red points with error bars. Dotted lines show where density is 2.5, 1.0, 0.5, 0.25 and 0.1 ρJ. Right panel: the mass-density diagram of the currently known transiting exoplanets (taken from TEPCat). Again HATS-13b and HATS-14b are shown in red points with error bars. Four planetary models with various core masses (10, 25, 50, and 100 Earth mass) and another without a core (Fortney et al. 2007) are plotted for comparison.

Open with DEXTER
In the text

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