102 research outputs found

    Molecular Imaging of Brain Tumours

    Get PDF
    This chapter is a review of the most common radiotracers currently used in clinical brain tumour imaging, and an update of future potentially useful radiotracers for imaging brain tumours with positron emission tomography (PET). It will focus mainly on glioma—the most common type of primary brain tumour—and intracranial metastases, as the cause of the majority of morbidity and mortality in neurooncology. Emerging data support the use of somatostatin analogue PET in the treatment planning and surveillance of meningiomas. There is currently a limited role of PET in other non-glial brain neoplasms including neuronal tumours, pineal and pituitary tumours, germ cell tumours and embryonal tumours (PNET, neuroblastoma). Finally, the newest hybrid imaging modality of PET/MRI and the promise it holds for obtaining state-of-the-art structural and functional imaging data simultaneously, are concisely reviewed

    KELT-8b: A highly inflated transiting hot Jupiter and a new technique for extracting high-precision radial velocities from noisy spectra

    Get PDF
    We announce the discovery of a highly inflated transiting hot Jupiter discovered by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with Teff=5754−55+54T_{\rm eff} = 5754_{-55}^{+54} K, log⁥g=4.078−0.054+0.049\log{g} = 4.078_{-0.054}^{+0.049}, [Fe/H]=0.272±0.038[Fe/H] = 0.272\pm0.038, an inferred mass M∗=1.211−0.066+0.078M_{*}=1.211_{-0.066}^{+0.078} M⊙_{\odot}, and radius R∗=1.67−0.12+0.14R_{*}=1.67_{-0.12}^{+0.14} R⊙_{\odot}. The planetary companion has mass MP=0.867−0.061+0.065M_P = 0.867_{-0.061}^{+0.065} MJM_{J}, radius RP=1.86−0.16+0.18R_P = 1.86_{-0.16}^{+0.18} RJR_{J}, surface gravity log⁥gP=2.793−0.075+0.072\log{g_{P}} = 2.793_{-0.075}^{+0.072}, and density ρP=0.167−0.038+0.047\rho_P = 0.167_{-0.038}^{+0.047} g cm−3^{-3}. The planet is on a roughly circular orbit with semimajor axis a=0.04571−0.00084+0.00096a = 0.04571_{-0.00084}^{+0.00096} AU and eccentricity e=0.035−0.025+0.050e = 0.035_{-0.025}^{+0.050}. The best-fit linear ephemeris is T0=2456883.4803±0.0007T_0 = 2456883.4803 \pm 0.0007 BJDTDB_{\rm TDB} and P=3.24406±0.00016P = 3.24406 \pm 0.00016 days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly-irradiated gas giants. The low stellar log⁥g\log{g} and large implied radius are supported by stellar density constraints from follow-up light curves, plus an evolutionary and space motion analysis. We also develop a new technique to extract high precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of Teq=1675−55+61T_{eq}=1675^{+61}_{-55} K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.Comment: Submitted to ApJ, feedback is welcom

    Characterizing K2 planet discoveries : a super-Earth transiting the bright K dwarf HIP 116454

    Get PDF
    We report the first planet discovery from the two-wheeled Kepler (K2) mission: HIP 116454 b. The host star HIP 116454 is a bright (V = 10.1, K = 8.0) K1 dwarf with high proper motion and a parallax-based distance of 55.2 ± 5.4 pc. Based on high-resolution optical spectroscopy, we find that the host star is metal-poor with [Fe/H] =–0.16 ± 0.08 and has a radius R = 0.716 ± 0.024 R ☉ and mass M = 0.775 ± 0.027 M ☉. The star was observed by the Kepler spacecraft during its Two-Wheeled Concept Engineering Test in 2014 February. During the 9 days of observations, K2 observed a single transit event. Using a new K2 photometric analysis technique, we are able to correct small telescope drifts and recover the observed transit at high confidence, corresponding to a planetary radius of pR = 2.53 ± 0.18 R ⊕. Radial velocity observations with the HARPS-N spectrograph reveal a 11.82 ± 1.33 M ⊕ planet in a 9.1 day orbit, consistent with the transit depth, duration, and ephemeris. Follow-up photometric measurements from the MOST satellite confirm the transit observed in the K2 photometry and provide a refined ephemeris, making HIP 116454 b amenable for future follow-up observations of this latest addition to the growing population of transiting super-Earths around nearby, bright stars.Publisher PDFPeer reviewe

    Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS

    Get PDF
    While the sample of confirmed exoplanets continues to increase, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated (∌\sim1277 F⊕F_{\oplus}) and bloated Saturn-mass planet (1.69−0.06+0.05^{+0.05}_{-0.06}RJupR_{Jup} and 0.43−0.08+0.09^{+0.09}_{-0.08}MJupM_{Jup}) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82−0.03+0.03^{+0.03}_{-0.03}RJupR_{Jup} and a mass of 0.30−0.08+0.07^{+0.07}_{-0.08}~MJupM_{Jup} in a 6.40 day orbit. Despite its high insolation flux (∌\sim600 F⊕F_{\oplus}), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.37−0.04+0.05^{+0.05}_{-0.04}MJupM_{Jup} planet in a 4.88 day orbit with a grazing transit (b = 1.04−0.06+0.05^{+0.05}_{-0.06 }) that results in a poorly constrained radius of 1.61−0.64+0.46^{+0.46}_{-0.64}RJupR_{Jup}. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and JWST\textit{JWST}. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation and migration of exoplanets across various stellar types.Comment: 16 pages, 17 figures, submitted to A&

    Innovation and entrepreneurship as strategies for success among Cuban-based firms in the late years of the transatlantic slave trade

    Get PDF
    This article examines how Cuban-based firms and entrepreneurs circumvented ever- increasing risks in the illegal slave trade. The article sheds light to this question by analyzing new qualitative information of 65 Cuban-based firms against the Slavevoyages database. Our findings indicate that Cuban-based firms were entrepreneurial as they exploited the opportunities arising from the volatility of the slave trade by: (a) internalizing networks of agents which allowed the rapid diffusion of information, (b) diversifying trading goods and expanding the number of partnerships to reduce transaction costs and risk, and (c) adopting technological innovations that modified the design and use of vessels

    Another Shipment of Six Short-Period Giant Planets from TESS

    Get PDF
    We present the discovery and characterization of six short-period, transiting giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS) -- TOI-1811 (TIC 376524552), TOI-2025 (TIC 394050135), TOI-2145 (TIC 88992642), TOI-2152 (TIC 395393265), TOI-2154 (TIC 428787891), & TOI-2497 (TIC 97568467). All six planets orbit bright host stars (8.9 <G< 11.8, 7.7 <K< 10.1). Using a combination of time-series photometric and spectroscopic follow-up observations from the TESS Follow-up Observing Program (TFOP) Working Group, we have determined that the planets are Jovian-sized (RP_{P} = 1.00-1.45 RJ_{J}), have masses ranging from 0.92 to 5.35 MJ_{J}, and orbit F, G, and K stars (4753 << Teff_{eff} << 7360 K). We detect a significant orbital eccentricity for the three longest-period systems in our sample: TOI-2025 b (P = 8.872 days, ee = 0.220±0.0530.220\pm0.053), TOI-2145 b (P = 10.261 days, ee = 0.182−0.049+0.0390.182^{+0.039}_{-0.049}), and TOI-2497 b (P = 10.656 days, ee = 0.196−0.053+0.0590.196^{+0.059}_{-0.053}). TOI-2145 b and TOI-2497 b both orbit subgiant host stars (3.8 << log⁥\log g <<4.0), but these planets show no sign of inflation despite very high levels of irradiation. The lack of inflation may be explained by the high mass of the planets; 5.35−0.35+0.325.35^{+0.32}_{-0.35} MJ_{\rm J} (TOI-2145 b) and 5.21±0.525.21\pm0.52 MJ_{\rm J} (TOI-2497 b). These six new discoveries contribute to the larger community effort to use {\it TESS} to create a magnitude-complete, self-consistent sample of giant planets with well-determined parameters for future detailed studies.Comment: 20 Pages, 6 Figures, 8 Tables, Accepted by MNRA

    The James Webb Space Telescope Mission

    Full text link
    Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least 4m4m. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the 6.5m6.5m James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure
    • 

    corecore