Kupfer T.,California Institute of Technology |
Van Roestel J.,Radboud University Nijmegen |
Brooks J.,University of California at Santa Barbara |
Geier S.,University of Tübingen |
And 21 more authors.
Astrophysical Journal | Year: 2017
We present the discovery of the hot subdwarf B star (sdB) binary PTF1 J082340.04+081936.5. The system has an orbital period of Porb = 87.49668(1) minutes (0.060761584(10) days), making it the second-most compact sdB binary known. The light curve shows ellipsoidal variations. Under the assumption that the sdB primary is synchronized with the orbit, we find a mass of MsdB = 0.45+0.09 -0.07 M⊙, a companion white dwarf mass of MWD = 0.46+ 0.12 -0.09 M⊙, and a mass ratio of q = MWD/MsdB = 1.03+0.10 -0.08. The future evolution was calculated using the MESA stellar evolution code. Adopting a canonical sdB mass of MsdB = 0.47 M⊙, we find that the sdB still burns helium at the time it will fill its Roche lobe if the orbital period was less than 106 minutes at the exit from the last common envelope (CE) phase. For longer CE exit periods, the sdB will have stopped burning helium and turned into a C/O white dwarf at the time of contact. Comparing the spectroscopically derived log g and Teff with our MESA models, we find that an sdB model with a hydrogen envelope mass of 5 × 10-4 M⊙ matches the measurements at a post-CE age of 94 Myr, corresponding to a post-CE orbital period of 109 minutes, which is close to the limit to start accretion while the sdB is still burning helium. © 2017. The American Astronomical Society. All rights reserved.
Magdis G.E.,University of Oxford |
Magdis G.E.,National institute for astrophysics |
Rigopoulou D.,University of Oxford |
Rigopoulou D.,Rutherford Appleton Laboratory |
And 25 more authors.
Astrophysical Journal | Year: 2014
We present Herschel far-IR photometry and spectroscopy as well as ground-based CO observations of an intermediate redshift (0.21 ≤ z ≤ 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (L IR > 1011.5 L ⊙). With these measurements, we trace the dust continuum, far-IR atomic line emission, in particular [C II] 157.7 μm, as well as the molecular gas of z ∼ 0.3 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and perform a detailed investigation of the interstellar medium of the population. We find that the majority of Herschel-selected intermediate redshift (U)LIRGs have L C II/L FIR ratios that are a factor of about 10 higher than that of local ULIRGs and comparable to that of local normal and high-z star-forming galaxies. Using our sample to bridge local and high-z [C II] observations, we find that the majority of galaxies at all redshifts and all luminosities follow an L C II-L FIR relation with a slope of unity, from which local ULIRGs and high- z active-galactic-nucleus-dominated sources are clear outliers. We also confirm that the strong anti-correlation between the L C II/L FIR ratio and the far-IR color L 60/L 100 observed in the local universe holds over a broad range of redshifts and luminosities, in the sense that warmer sources exhibit lower L C II/L FIR at any epoch. Intermediate redshift ULIRGs are also characterized by large molecular gas reservoirs and by lower star formation efficiencies compared to that of local ULIRGs. The high L C II/L FIR ratios, the moderate star formation efficiencies (L IR/ or L IR/), and the relatively low dust temperatures of our sample (which are also common characteristics of high-z star-forming galaxies with ULIRG-like luminosities) indicate that the evolution of the physical properties of (U)LIRGs between the present day and z > 1 is already significant by z ∼ 0.3. © 2014. The American Astronomical Society. All rights reserved.
Inome Y.,Konan University |
Ambrosi G.,National Institute of Nuclear Physics, Italy |
Awane Y.,Kyoto University |
Baba H.,Ibaraki University |
And 150 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014
The Large Size Telescopes, LSTs, located at the center of the Cherenkov Telescope Array, CTA, will be sensitive for low energy gamma-rays. The camera on the LST focal plane is optimized to detect low energy events based on a high photon detection efficiency and high speed electronics. Also the trigger system is designed to detect low energy showers as much as possible. In addition, the camera is required to work stably without maintenance in a few tens of years. In this contribution we present the design of the camera for the first LST and the status of its development and production. © 2014 SPIE.
Biller B.A.,University of Edinburgh |
Biller B.A.,Max Planck Institute for Astronomy |
Vos J.,University of Edinburgh |
Bonavita M.,University of Edinburgh |
And 17 more authors.
Astrophysical Journal Letters | Year: 2015
As part of our ongoing NTT SoFI survey for variability in young free-floating planets and low-mass brown dwarfs, we detect significant variability in the young, free-floating planetary-mass object PSO J318.5-22, likely due to rotational modulation of inhomogeneous cloud cover. A member of the 23 ± 3 Myr β Pic moving group, PSO J318.5-22 has Teff = K and a mass estimate of 8.3 ± 0.5 MJup for a 23 ± 3 Myr age. PSO J318.5-22 is intermediate in mass between 51 Eri b and β Pic b, the two known exoplanet companions in the β Pic moving group. With variability amplitudes from 7% to 10% in JS at two separate epochs over 3-5 hr observations, we constrain the rotational period of this object to >5 hr. In KS, we marginally detect a variability trend of up to 3% over a 3 hr observation. This is the first detection of weather on an extrasolar planetary-mass object. Among L dwarfs surveyed at high photometric precision (<3%), this is the highest amplitude variability detection. Given the low surface gravity of this object, the high amplitude preliminarily suggests that such objects may be more variable than their high-mass counterparts, although observations of a larger sample are necessary to confirm this. Measuring similar variability for directly imaged planetary companions is possible with instruments such as SPHERE and GPI and will provide important constraints on formation. Measuring variability at multiple wavelengths can help constrain cloud structure. © 2015. The American Astronomical Society. All rights reserved.
Pinsonneault M.H.,Ohio State University |
Elsworth Y.,University of Birmingham |
Elsworth Y.,University of Aarhus |
Epstein C.,Ohio State University |
And 53 more authors.
Astrophysical Journal, Supplement Series | Year: 2014
We present the first APOKASC catalog of spectroscopic and asteroseismic properties of 1916 red giants observed in the Kepler fields. The spectroscopic parameters provided from the Apache Point Observatory Galactic Evolution Experiment project are complemented with asteroseismic surface gravities, masses, radii, and mean densities determined by members of the Kepler Asteroseismology Science Consortium. We assess both random and systematic sources of error and include a discussion of sample selection for giants in the Kepler fields. Total uncertainties in the main catalog properties are of the order of 80 K in T eff, 0.06 dex in [M/H], 0.014 dex in log g, and 12% and 5% in mass and radius, respectively; these reflect a combination of systematic and random errors. Asteroseismic surface gravities are substantially more precise and accurate than spectroscopic ones, and we find good agreement between their mean values and the calibrated spectroscopic surface gravities. There are, however, systematic underlying trends with T eff and log g. Our effective temperature scale is between 0 and 200 K cooler than that expected from the infrared flux method, depending on the adopted extinction map, which provides evidence for a lower value on average than that inferred for the Kepler Input Catalog (KIC). We find a reasonable correspondence between the photometric KIC and spectroscopic APOKASC metallicity scales, with increased dispersion in KIC metallicities as the absolute metal abundance decreases, and offsets in T eff and log g consistent with those derived in the literature. We present mean fitting relations between APOKASC and KIC observables and discuss future prospects, strengths, and limitations of the catalog data. © 2014. The American Astronomical Society. All rights reserved.
Bufano F.,National institute for astrophysics |
Bufano F.,Andrés Bello University |
Pian E.,National institute for astrophysics |
Pian E.,Normal School of Pisa |
And 56 more authors.
Astrophysical Journal | Year: 2012
We present the spectroscopic and photometric evolution of the nearby (z = 0.059) spectroscopically confirmed Type Ic supernova, SN2010bh, associated with the soft, long-duration gamma-ray burst (X-ray flash) GRB100316D. Intensive follow-up observations of SN2010bh were performed at the ESO Very Large Telescope (VLT) using the X-shooter and FORS2 instruments. Thanks to the detailed temporal coverage and the extended wavelength range (3000-24800Å), we obtained an unprecedentedly rich spectral sequence among the hypernovae, making SN2010bh one of the best studied representatives of this SN class. We find that SN2010bh has a more rapid rise to maximum brightness (8.0 ± 1.0 rest-frame days) and a fainter absolute peak luminosity (L bol ≈ 3 × 1042 erg s-1) than previously observed SN events associated with GRBs. Our estimate of the ejected 56Ni mass is 0.12 ± 0.02 M o. From the broad spectral features, we measure expansion velocities up to 47,000kms-1, higher than those of SNe 1998bw (GRB980425) and 2006aj (GRB060218). Helium absorption lines He I λ5876 and He I 1.083 μm, blueshifted by 20,000-30,000kms-1 and 28,000-38,000kms-1, respectively, may be present in the optical spectra. However, the lack of coverage of the He I 2.058 μm line prevents us from confirming such identifications. The nebular spectrum, taken at 186days after the explosion, shows a broad but faint [O I] emission at 6340Å. The light curve shape and photospheric expansion velocities of SN2010bh suggest that we witnessed a highly energetic explosion with a small ejected mass (E k ≈ 1052 erg and M ej ≈ 3 Mo). The observed properties of SN2010bh further extend the heterogeneity of the class of GRB SNe. © © 2012. The American Astronomical Society. All rights reserved.
Martell S.L.,University of New South Wales |
Shetrone M.D.,University of Texas at Austin |
Lucatello S.,National institute for astrophysics |
Schiavon R.P.,Liverpool John Moores University |
And 7 more authors.
Astrophysical Journal | Year: 2016
We present new identifications of five red giant stars in the Galactic halo with chemical abundance patterns that indicate they originally formed in globular clusters. Using data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Survey available through Sloan Digital Sky Survey (SDSS) Data Release 12, we first identify likely halo giants, and then search those for the well-known chemical tags associated with globular clusters, specifically enrichment in nitrogen and aluminum. We find that 2% of the halo giants in our sample have this chemical signature, in agreement with previous results. Following the interpretation in our previous work on this topic, this would imply that at least 13% of halo stars originally formed in globular clusters. Recent developments in the theoretical understanding of globular cluster formation raise questions about that interpretation, and we concede the possibility that these migrants represent a small fraction of the halo field. There are roughly as many stars with the chemical tags of globular clusters in the halo field as there are in globular clusters, whether or not they are accompanied by a much larger chemically untaggable population of former globular cluster stars. © 2016. The American Astronomical Society. All rights reserved.
Dai F.,Massachusetts Institute of Technology |
Winn J.N.,Massachusetts Institute of Technology |
Albrecht S.,University of Aarhus |
Arriagada P.,Harvard - Smithsonian Center for Astrophysics |
And 26 more authors.
Astrophysical Journal | Year: 2016
In an effort to measure the masses of planets discovered by the NASA K2 mission, we have conducted precise Doppler observations of five stars with transiting planets. We present the results of a joint analysis of these new data and previously published Doppler data. The first star, an M dwarf known as K2-3 or EPIC 201367065, has three transiting planets ("b," with radius "c," and "d," ). Our analysis leads to the mass constraints: And M c < 4.2 M ⊕ (95% confidence). The mass of planet d is poorly constrained because its orbital period is close to the stellar rotation period, making it difficult to disentangle the planetary signal from spurious Doppler shifts due to stellar activity. The second star, a G dwarf known as K2-19 or EPIC 201505350, has two planets ("b," 7.7 R ⊕; and "c," 4.9 R ⊕) in a 3:2 mean-motion resonance, as well as a shorter-period planet ("d," 1.1 R ⊕). We find M b = , M c = and M d < 14.0 M ⊕ (95% conf.). The third star, a G dwarf known as K2-24 or EPIC 203771098, hosts two transiting planets ("b," 5.7 R ⊕; and "c," 7.8 R ⊕) with orbital periods in a nearly 2:1 ratio. We find M b = and M c = . The fourth star, a G dwarf known as EPIC 204129699, hosts a hot Jupiter for which we measured the mass to be . The fifth star, a G dwarf known as EPIC 205071984, contains three transiting planets ("b," 5.4 R ⊕; "c," 3.5 R ⊕; and "d," 3.8 R ⊕), the outer two of which have a nearly 2:1 period ratio. We find M b = , M c < (95% conf.) and M d < 35 M ⊕ (95% conf.). © 2016. The American Astronomical Society. All rights reserved.
Asa'd R.S.,American University of Sharjah |
Vazdekis A.,Institute Astrofsica Of Canarias Iac |
Vazdekis A.,University of La Laguna |
Zeinelabdin S.,American University of Sharjah
Monthly Notices of the Royal Astronomical Society | Year: 2016
We use ASAD2, the new version of ASAD (Analyzer of Spectra for Age Determination), to obtain the age and reddening of 27 Large Magellanic Cloud (LMC) clusters from full fitting of integrated spectra using different statistical methods [χ2 and Kolmogorov-Smirnov (KS) test] and a set of stellar population models including GALAXEV and MILES. We show that our results are in good agreement with the colour-magnitude diagram (CMD) ages for both models, and that metallicity does not affect the age determination for the full spectrum fitting method regardless of the model used for ages with log (age/year) < 9. We discuss the results obtained by the two statistical results for both GALAXEV and MILES versus three factors: Age, signal-to-noise ratio and resolution (full width at half maximum). The predicted reddening values when using the χ2 minimization method are within the range found in the literature for resolved clusters (i.e. < 0.35); however the KS test can predict E(B - V) higher values. The sharp spectrum transition originated at ages around the supergiants contribution, at either side of the AGB peak around log (age/year) 9.0 and log (age/year) 7.8 are limiting our ability to provide values in agreement with the CMD estimates and as a result the reddening determination is not accurate. We provide the detailed results of four clusters spanning a wide range of ages. ASAD2 is a user-friendly program available for download on theWeb and can be immediately used at http://randaasad.wordpress.com/asad-package/. © 2016 The Authors.