ELTE Gothard Astrophysical Observatory

Szombathely, Hungary

ELTE Gothard Astrophysical Observatory

Szombathely, Hungary
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Bohlin R.C.,US Space Telescope Science Institute | Meszaros S.,ELTE Gothard Astrophysical Observatory | Fleming S.W.,US Space Telescope Science Institute | Gordon K.D.,US Space Telescope Science Institute | And 3 more authors.
Astronomical Journal | Year: 2017

The Space Telescope Imaging Spectrograph has measured the spectral energy distributions for several stars of types O, B, A, F, and G. These absolute fluxes from the CALSPEC database are fit with a new spectral grid computed from the ATLAS-APOGEE ATLAS9 model atmosphere database using a chi-square minimization technique in four parameters. The quality of the fits are compared for complete LTE grids by Castelli & Kurucz (CK04) and our new comprehensive LTE grid (BOSZ). For the cooler stars, the fits with the MARCS LTE grid are also evaluated, while the hottest stars are also fit with the NLTE Lanz & Hubeny OB star grids. Unfortunately, these NLTE models do not transition smoothly in the infrared to agree with our new BOSZ LTE grid at the NLTE lower limit of T eff = 15,000 K. The new BOSZ grid is available via the Space Telescope Institute MAST archive and has a much finer sampled IR wavelength scale than CK04, which will facilitate the modeling of stars observed by the James Webb Space Telescope. Our result for the angular diameter of Sirius agrees with the ground-based interferometric value. © 2017. The American Astronomical Society. All rights reserved.

Hayden M.R.,New Mexico State University | Bovy J.,Institute for Advanced Study | Holtzman J.A.,New Mexico State University | Nidever D.L.,University of Michigan | And 40 more authors.
Astrophysical Journal | Year: 2015

Using a sample of 69,919 red giants from the SDSS-III/APOGEE Data Release 12, we measure the distribution of stars in the [/Fe] versus [Fe/H] plane and the metallicity distribution functions (MDFs) across an unprecedented volume of the Milky Way disk, with radius 3 < R < 15 kpc and height kpc. Stars in the inner disk (R < 5 kpc) lie along a single track in [/Fe] versus [Fe/H], starting with -enhanced, metal-poor stars and ending at [/Fe] ∼ 0 and [Fe/H] ∼ +0.4. At larger radii we find two distinct sequences in [/Fe] versus [Fe/H] space, with a roughly solar- sequence that spans a decade in metallicity and a high- sequence that merges with the low- sequence at super-solar [Fe/H]. The location of the high- sequence is nearly constant across the disk.

Meszaros S.,ELTE Gothard Astrophysical Observatory | Meszaros S.,Indiana University Bloomington | Martell S.L.,University of New South Wales | Shetrone M.,University of Texas at Austin | And 25 more authors.
Astronomical Journal | Year: 2015

We investigate the light-element behavior of red giant stars in northern globular clusters (GCs) observed by the SDSS-III Apache Point Observatory Galactic Evolution Experiment. We derive abundances of 9 elements (Fe, C, N, O, Mg, Al, Si, Ca, and Ti) for 428 red giant stars in 10 GCs. The intrinsic abundance range relative to measurement errors is examined, and the well-known C-N and Mg-Al anticorrelations are explored using an extreme-deconvolution code for the first time in a consistent way. We find that Mg and Al drive the population membership in most clusters, except in M107 and M71, the two most metal-rich clusters in our study, where the grouping is most sensitive to N. We also find a diversity in the abundance distributions, with some clusters exhibiting clear abundance bimodalities (for example M3 and M53) while others show extended distributions. The spread of Al abundances increases significantly as cluster average metallicity decreases as previously found by other works, which we take as evidence that low metallicity, intermediate mass AGB polluters were more common in the more metal-poor clusters. The statistically significant correlation of [Al/Fe] with [Si/Fe] in M15 suggests that 28Si leakage has occurred in this cluster. We also present C, N, and O abundances for stars cooler than 4500 K and examine the behavior of A(C+N+O) in each cluster as a function of temperature and [Al/Fe]. The scatter of A(C+N+O) is close to its estimated uncertainty in all clusters and independent of stellar temperature. A(C+N+O) exhibits small correlations and anticorrelations with [Al/Fe] in M3 and M13, but we cannot be certain about these relations given the size of our abundance uncertainties. Star-to-star variations of -element (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters. © 2015. The American Astronomical Society. All rights reserved..

Carlberg J.K.,Carnegie Institution of Washington | Smith V.V.,National Optical Astronomy Observatory | Cunha K.,Observatorio Nacional | Cunha K.,University of Arizona | And 18 more authors.
Astrophysical Journal | Year: 2015

A Li-rich red giant (RG) star (2M19411367+4003382) recently discovered in the direction of NGC 6819 belongs to the rare subset of Li-rich stars that have not yet evolved to the luminosity bump, an evolutionary stage where models predict Li can be replenished. The currently favored model to explain Li enhancement in first-ascent RGs like 2M19411367+4003382 requires deep mixing into the stellar interior. Testing this model requires a measurement of 12C/13C, which is possible to obtain from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. However, the Li-rich star also has abnormal asteroseismic properties that call into question its membership in the cluster, even though its radial velocity and location on color-magnitude diagrams are consistent with membership. To address these puzzles, we have measured a wide array of abundances in the Li-rich star and three comparison stars using spectra taken as part of the APOGEE survey to determine the degree of stellar mixing, address the question of membership, and measure the surface gravity. We confirm that the Li-rich star is a RG with the same overall chemistry as the other cluster giants. However, its is significantly lower, consistent with the asteroseismology results and suggestive of a very low mass if the star is indeed a cluster member. Regardless of the cluster membership, the 12C/13C and C/N ratios of the Li-rich star are consistent with standard first dredge-up, indicating that Li dilution has already occurred, and inconsistent with internal Li enrichment scenarios that require deep mixing. © 2015. The American Astronomical Society. All rights reserved..

Shetrone M.,University of Texas at Austin | Bizyaev D.,New Mexico State University | Bizyaev D.,Moscow State University | Lawler J.E.,University of Wisconsin - Madison | And 19 more authors.
Astrophysical Journal, Supplement Series | Year: 2015

We present the H-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The APOGEE line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the APOGEE line list, which is one of the critical inputs for the APOGEE Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134,457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec, and Turbospectrum formats. The limitations of the line lists along with guidance for its use on different spectral types are discussed. We also present a list of H-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for APOGEE observations spanning a wide range of stellar parameters. © 2015. The American Astronomical Society. All rights reserved.

Shporer A.,California Institute of Technology | Shporer A.,Jet Propulsion Laboratory | O'Rourke J.G.,California Institute of Technology | Knutson H.A.,California Institute of Technology | And 15 more authors.
Astrophysical Journal | Year: 2014

Kepler-13Ab (= KOI-13.01) is a unique transiting hot Jupiter. It is one of very few known short-period planets orbiting a hot A-type star, making it one of the hottest planets currently known. The availability of Kepler data allows us to measure the planet's occultation (secondary eclipse) and phase curve in the optical, which we combine with occultations observed by warm Spitzer at 4.5 μm and 3.6 μm and a ground-based occultation observation in the Ks band (2.1 μm). We derive a day-side hemisphere temperature of 2750 ± 160 K as the effective temperature of a black body showing the same occultation depths. Comparing the occultation depths with one-dimensional planetary atmosphere models suggests the presence of an atmospheric temperature inversion. Our analysis shows evidence for a relatively high geometric albedo, A g = . While measured with a simplistic method, a high A g is supported also by the fact that the one-dimensional atmosphere models underestimate the occultation depth in the optical. We use stellar spectra to determine the dilution, in the four wide bands where occultation was measured, due to the visual stellar binary companion 1.″15 ± 0.″05 away. The revised stellar parameters measured using these spectra are combined with other measurements, leading to revised planetary mass and radius estimates of Mp = 4.94-8.09 M J and Rp = 1.406 ± 0.038 R J. Finally, we measure a Kepler midoccultation time that is 34.0 ± 6.9 s earlier than expected based on the midtransit time and the delay due to light-travel time and discuss possible scenarios. © 2014. The American Astronomical Society. All rights reserved..

Szabo R.,Hungarian Academy of Sciences | Sarneczky K.,Hungarian Academy of Sciences | Sarneczky K.,Gothard Lendulet Research Team | Szabo G.M.,Hungarian Academy of Sciences | And 11 more authors.
Astronomical Journal | Year: 2015

Unlike NASA's original Kepler Discovery Mission, the renewed K2 Mission will target the plane of the Ecliptic, observing each field for approximately 75 days. This will bring new opportunities and challenges, in particular the presence of a large number of main-belt asteroids that will contaminate the photometry. The large pixel size makes K2 data susceptible to the effects of apparent minor planet encounters. Here, we investigate the effects of asteroid encounters on photometric precision using a subsample of the K2 engineering data taken in 2014 February. We show examples of asteroid contamination to facilitate their recognition and distinguish these events from other error sources. We conclude that main-belt asteroids will have considerable effects on K2 photometry of a large number of photometric targets during the Mission that will have to be taken into account. These results will be readily applicable for future space photometric missions applying large-format CCDs, such as TESS and PLATO. © 2015. The American Astronomical Society. All rights reserved..

Szabo G.M.,ELTE Gothard Astrophysical Observatory | Szabo G.M.,Hungarian Academy of Sciences | Szabo G.M.,Gothard Lendulet Research Team | Simon A.,Hungarian Academy of Sciences | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

Kepler-13b is a most intriguing exoplanet system due to the rapid precession rate, exhibiting several exotic phenomena.We analysed Kepler short cadence data up to Quarter 14, with a total time-span of 928 d, to reveal changes in transit duration, depth, asymmetry and identify the possible signals of stellar rotation and low-level activity.We investigated long-term variations of transit light curves testing for duration, peak depth and asymmetry. We also performed cluster analysis on Kepler quarters. We computed the autocorrelation function of the out-oftransit light variations. Transit duration, peak depth and asymmetry evolve slowly, due to the slowly drifting transit path through the stellar disc. The detected transit shapes will map the stellar surface on the time-scale of decades. We found a very significant clustering pattern with 3-orbit period. Its source is very probably the rotating stellar surface, in the 5:3 spin- orbit resonance reported in a previous study. The autocorrelation function of the out-of-transit light variations, filtered to 25.4 h and harmonics, shows slow variations and a peak around 300-360 d period, which could be related to the activity cycle of the host star. © 2013 The Authors.

Moor A.,Hungarian Academy of Sciences | Abraham P.,Hungarian Academy of Sciences | Kospal A.,European Space Agency | Szabo Gy.M.,Hungarian Academy of Sciences | And 11 more authors.
Astrophysical Journal Letters | Year: 2013

Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, β Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of ∼6.″0 × 5.″4 (540 × 490 AU) and disk inclination of ∼25°. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist. © 2013. The American Astronomical Society. All rights reserved.

Moor A.,Hungarian Academy of Sciences | Henning T.,Max Planck Institute for Astronomy | Juhasz A.,Institute of Astronomy | Abraham P.,Hungarian Academy of Sciences | And 12 more authors.
Astrophysical Journal | Year: 2015

Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10-40 Myr old systems. We used the APEX and IRAM 30 m radio telescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3-2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk at both 70 and 100 μm, with a characteristic radius of ∼170 AU. While in stellar properties HD 131835 resembles β Pic, its dust disk properties are similar to those of the most massive young debris disks. With the detection of gas in HD 131835 the number of known debris disks with CO content has increased to four, all of them encircling young (≤40 Myr) A-type stars. Based on statistics within 125 pc, we suggest that the presence of a detectable amount of gas in the most massive debris disks around young A-type stars is a common phenomenon. Our current data cannot conclude on the origin of gas in HD 131835. If the gas is secondary, arising from the disruption of planetesimals, then HD 131835 is a comparably young, and in terms of its disk, more massive analog of the β Pic system. However, it is also possible that this system, similar to HD 21997, possesses a hybrid disk, where the gas material is predominantly primordial, while the dust grains are mostly derived from planetesimals. © 2015. The American Astronomical Society. All rights reserved..

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