221 research outputs found

    Identification of the Microlens in Event MACHO-LMC-20

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    We report on the identification of the lens responsible for microlensing event MACHO-LMC-20. As part of a \textit{Spitzer}/IRAC program conducting mid-infrared follow-up of the MACHO Large Magellanic Cloud microlensing fields, we discovered a significant flux excess at the position of the source star for this event. These data, in combination with high resolution near-infrared \textit{Magellan}/PANIC data has allowed us to classify the lens as an early M dwarf in the thick disk of the Milky Way, at a distance of ∼2\sim 2 kpc. This is only the second microlens to have been identified, the first also being a M dwarf star in the disk. Together, these two events are still consistent with the expected frequency of nearby stars in the Milky Way thin and thick disks acting as lenses.Comment: 6 pages, 4 figures, submitted to ApJ Letter

    From trust in caregivers' support to exploration : the role of openness to negative affect and self-regulation

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    Attachment theory assumes that trust in caregivers' support and exploration are closely related. Little research tried to investigate this link, nor focuses on mechanisms that might explain this association. The present studies examined whether trust is related to exploration through a serial indirect effect of openness to negative affect and self-regulation. In Study 1, 212 children, aged 8-13, completed questionnaires assessing trust, openness to negative affect, self-regulation and exploration. The results showed that trust predicted exploration, but only to the extent to which openness to negative affect and self-regulation were involved too. Study 2 refined these findings (n = 59, aged 9-12) using a behavioral measure of openness to negative affect and exploration, and with mother-reported self-regulation. Replicating this serial indirect effect of openness to negative affect and self-regulation with multiple informants and methods, the present studies advance our understanding of how trust might foster exploration in preadolescence

    The State of Ambulatory Undergraduate Internal Medicine Medical Education: Results of the 2016 Clerkship Directors in Internal Medicine Annual Survey

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    Ambulatory care is qualitatively different and valuable to the health system. Given the shifts in health care that prioritize ambulatory care, internal medicine educators see benefits to learning in this environment. Internal medicine education teaches the skills necessary for managing complex patients, including those with multiple illnesses, medications, and social needs, all of which are encountered in the practice of ambulatory internal medicine

    ExploreNEOs. III. Physical Characterization of 65 Potential Spacecraft Target Asteroids

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    Space missions to near-Earth objects (NEOs) are being planned at all major space agencies, and recently a manned mission to an NEO was announced as a NASA goal. Efforts to find and select suitable targets (plus backup targets) are severely hampered by our lack of knowledge of the physical properties of dynamically favorable NEOs. In particular, current mission scenarios tend to favor primitive low-albedo objects. For the vast majority of NEOs, the albedo is unknown. Here we report new constraints on the size and albedo of 65 NEOs with rendezvous Δv <7 km s^(–1). Our results are based on thermal-IR flux data obtained in the framework of our ongoing (2009-2011) ExploreNEOs survey using NASA's "Warm-Spitzer" space telescope. As of 2010 July 14, we have results for 293 objects in hand (including the 65 low-Δv NEOs presented here); before the end of 2011, we expect to have measured the size and albedo of ~700 NEOs (including probably ~160 low-Δv NEOs). While there are reasons to believe that primitive volatile-rich materials are universally low in albedo, the converse need not be true: the orbital evolution of some dark objects likely has caused them to lose their volatiles by coming too close to the Sun. For all our targets, we give the closest perihelion distance they are likely to have reached (using orbital integrations from Marchi et al. 2009) and corresponding upper limits on the past surface temperature. Low-Δv objects for which both albedo and thermal history may suggest a primitive composition include (162998) 2001 SK162, (68372) 2001 PM9, and (100085) 1992 UY4

    Inhibition of Linear Absorption in Opaque Materials Using Phase-Locked Harmonic Generation

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    We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second- and third-harmonic generation in strongly absorbing materials, GaAs, in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300 nm generates 650 and 435 nm second- and third-harmonic pulses that propagate across a 450−μm-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress on them its dispersive properties

    Inhibition of Linear Absorption in Opaque Materials Using Phase-Locked Harmonic Generation

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    We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second- and third-harmonic generation in strongly absorbing materials, GaAs, in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300 nm generates 650 and 435 nm second- and third-harmonic pulses that propagate across a 450−μm-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress on them its dispersive properties

    Spitzer/IRAC Limits to Planetary Companions of Fomalhaut and epsilon Eridani

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    Fomalhaut and epsilon Eridani are two young, nearby stars that possess extended debris disks whose structures suggest the presence of perturbing planetary objects. With its high sensitivity and stable point spread function, Spitzer/IRAC is uniquely capable of detecting cool, Jupiter-like planetary companions whose peak emission is predicted to occur near 4.5 um. We report on deep IRAC imaging of these two stars, taken at 3.6 and 4.5 um using subarray mode and in all four channels in wider-field full array mode. Observations acquired at two different telescope roll angles allowed faint surrounding objects to be separated from the stellar diffraction pattern. No companion candidates were detected at the reported position of Fomalhaut b with 3 sigma model-dependent mass upper limits of 3 MJ (for an age of 200 Myr). Around epsilon Eridani we instead set a limit of 4 and <1 MJ (1 Gyr model age) at the inner and outer edge of the sub-millimeter debris ring, respectively. These results are consistent with non-detections in recent near-infrared imaging searches, and set the strongest limits to date on the presence of planets outside epsilon Eridani sub-millimeter ring.Comment: Accepted by The Astrophysical Journal. Request electronic-only plates to M. Marengo ([email protected]

    The Ultraviolet-to-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars

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    We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 <= z <= 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame ~0.1-5 mum spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line-of-sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.Comment: 10 pages (emulateapj), 4 figures. Accepted for publication in Ap
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