First Keck Nulling Observations of a Young Stellar Object: Probing the Circumstellar Environment of the Herbig Ae star MWC 325

We present the first N-band nulling plus K- and L-band V2 observations of a young stellar object, MWC325, taken with the 85 m baseline Keck Interferometer. The Keck nuller was designed for the study of faint dust signatures associated with debris disks, but it also has a unique capability for studying the temperature and density distribution of denser disks found around young stellar objects. Interferometric observations of MWC 325 at K, L and N encompass a factor of five in spectral range and thus, especially when spectrally dispersed within each band, enable characterization of the structure of the inner disk regions where planets form. Fitting our observations with geometric models such as a uniform disk or a Gaussian disk show that the apparent size increases monotonically with wavelength in the 2-12 um wavelength region, confirming the widely held assumption based on radiative transfer models, now with spatially resolved measurements over broad wavelength range, that disks are extended with a temperature gradient. The effective size is a factor of about 1.3 and 2 larger in the L-band and N-band, respectively, compared to that in the K-band. The existing interferometric measurements and the spectral energy distribution can be reproduced by a flat disk or a weakly-shadowed nearly flat-disk model, with only slight flaring in the outer regions of the disk, consisting of representative "sub-micron" (0.1 um) and "micron" (2 um) grains of a 50:50 ratio of silicate and graphite. This is marked contrast with the disks previously found in other Herbig Ae/Be stars suggesting a wide variety in the disk properties among Herbig Ae/Be stars.Comment: Accepted for publication in the Ap

Quality of Education and Innovation-Driven Development: the New Ukrainian School Reform

Introduction. Accelerating human progress is a result of the growing role of innovations. This requires the development of an innovative person as an effective actor of their implementation and support. Primary, and secondary education is very important factor for this. The New Ukrainian School (NUS) reform that has been being implemented since 2016 shall adequately meet current challenges and trends. Problem Statement. To this end, it is very important to identify the key intra-system and contextual factors influencing the quality of school education, first of all in reading, mathematics, and natural sciences, in terms of the development of an innovative person. Purpose. The purpose of this research is to determine the endogenous (internal) and exogenous (external) factors that effectively influence the educational quality, in order to optimize the NUS implementation in the present-day conditions. Materials and Methods. Multifactor system analysis (in particular statistical, correlation, and comparative techniques) of big global databases on human development, international assessment of the quality of primary and basic secondary education, development of world research and university spheres and features of the NUS implementation in Ukraine. Results. The probable global connections between the quality of school education and the factors of internal educational and external contextual impact on the educational quality have been identified. Among the considered nine factors effecting the quality of student education in reading, mathematics, and science, the most influential (resonant) and stable are the endogenous ones, namely, the mean years of schooling, and the share of R&D expenditure in GDP, with the latter having a greater impact. The recommendations for improving the efficiency of the NUS have been given. Conclusions. The effectiveness of school education reform, in particular, NUS, may be raised by taking into account the deterministic effect of endogenous and exogenous factors on the quality of education.Вступ. Прискорення прогресу людства зумовлене зростанням ролі інновацій, що потребує формування ефективногосуб’єкта їх здійснення та підтримки — інноваційної людини, за формування якої відповідальна сфера освіти, особливо початкова та середня освітні ланки. Реформа «Нова українська школа» (НУШ), яка впроваджується з 2016 р., має адекватно спрямовуватися з огляду на сучасні виклики й тенденції. Проблематика. Важливою в цьому контексті є ідентифікація ключових внутрішньосистемних і контекстуальних факторів впливу на якість шкільної освіти, насамперед з читання, математики, природничих наук, задля розвиткуінноваційної людини. Мета. З’ясування ендогенних та екзогенних чинників ефективного впливу на освітню якість для оптимізації реалізації НУШ у сучасних умовах. Матеріали й методи. Використано багатофакторний системний аналіз, зокрема статистичний, кореляційний, порівняльний, метод великих баз нових глобальних даних щодо людського розвитку, міжнародного оцінювання якості початкової і базової середньої освіти, розвитку світової наукової й університетської сфер та особливостей впровадження НУШ в Україні. Результати. З’ясовано глобальні вірогідні зв’язки між якістю шкільної освіти та факторами внутрішньо-освітянського та зовнішньо-контекстуального впливу на якість освіти. З-поміж розглянутих дев’яти чинників якості освіти школярів з читання, математики і природничих наук, особливо впливовими (резонансними) і стійкими виявилисяендогенна фактична тривалість освіти та екзогенна частка ВВП, що спрямовується на наукову сферу. При цьому впливовість зазначеної частки ВВП більша, ніж тривалості освіти. Обґрунтовано рекомендації щодо підвищення ефективності НУШ. Висновки. Підвищити результативність реформування шкільної освіти, зокрема на засадах НУШ, можна шляхом урахування детерміністичної дії на якість освіти низки ендо- і екзогенних факторів впливу

ASTRA: ASTrometry and phase-Referencing Astronomy on the Keck interferometer

ASTRA (ASTrometric and phase-Referencing Astronomy) is an upgrade to the existing Keck Interferometer which aims at providing new self-phase referencing (high spectral resolution observation of YSOs), dual-field phase referencing (sensitive AGN observations), and astrometric (known exoplanetary systems characterization and galactic center general relativity in strong field regime) capabilities. With the first high spectral resolution mode now offered to the community, this contribution focuses on the progress of the dual field and astrometric modes.Comment: 10 pages, 6 figures, 2 tables, SPIE 201

Keck Interferometer autoaligner: algorithms and techniques

The Keck Interferometer includes an autoalignment system consisting of pop-up targets located at strategic locations along the beam trains of each arm of the instrument along with a sensor and control system. We briefly describe the hardware of the system and then proceed to a description of the two operational modes of the system. These are: 1) to provide an initial alignment of the coude paths in each arm, and 2) to recover coude alignments between changes of the static delay sled positions. For the initial alignment mode, we review the system performance requirements along with the software used for image acquisition and centroiding. For coudé alignment recovery, we describe beam-train surveys through the static delay (Long Delay Line) and criteria for a successful recovery of a coudé alignment. Finally, we describe the results of testing of the autoalignment system

Keck Interferometer Nuller Data Reduction and On-Sky Performance

We describe the Keck Interferometer nuller theory of operation, data reduction, and on-sky performance, particularly as it applies to the nuller exozodiacal dust key science program that was carried out between 2008 February and 2009 January. We review the nuller implementation, including the detailed phasor processing involved in implementing the null-peak mode used for science data and the sequencing used for science observing. We then describe the Level 1 reduction to convert the instrument telemetry streams to raw null leakages, and the Level 2 reduction to provide calibrated null leakages. The Level 1 reduction uses conservative, primarily linear processing, implemented consistently for science and calibrator stars. The Level 2 processing is more flexible, and uses diameters for the calibrator stars measured contemporaneously with the interferometer’s K-band cophasing system in order to provide the requisite accuracy. Using the key science data set of 462 total scans, we assess the instrument performance for sensitivity and systematic error. At 2.0 Jy we achieve a photometrically-limited null leakage uncertainty of 0.25% rms per 10 minutes of integration time in our broadband channel. From analysis of the Level 2 reductions, we estimate a systematic noise floor for bright stars of ~0.2% rms null leakage uncertainty per observing cluster in the broadband channel. A similar analysis is performed for the narrowband channels. We also provide additional information needed for science reduction, including details on the instrument beam pattern and the basic astrophysical response of the system, and references to the data reduction and modeling tools

Milliarcsecond N-Band Observations of the Nova RS Ophiuchi: First Science with the Keck Interferometer Nuller

We report observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nuller (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N-band from 8 to 12.5 microns in a nulling mode. By fitting the unique KIN data, we have obtained an angular size of the mid-infrared continuum of 6.2, 4.0, or 5.4 mas for a disk profile, gaussian profile (FWHM), and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at ! 17 AU from the WD, that are not found in the inner regime. Our evidence suggests that these features have been excited by the nova flash in the outer spatial regime before the blast wave reached these regions. These identifications support a model in which the dust appears to be present between outbursts and is not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.Comment: 41 pages, 10 figure

The dusty AGB star RS CrB: first mid-infrared interferometric observations with the Keck Telescopes

We report interferometric observations of the semi-regular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner. The light was dispersed by a low-resolution spectrometer, allowing simultaneous measurement of the source visibility and intensity spectra from 8 to 12 microns. The interferometric observations allow a non-ambiguous determination of the dust shell spatial scale and relative flux contribution. Using a simple spherically-symmetric model, in which a geometrically thin shell surrounds the stellar photosphere, we find that ~30% to ~70% of the overall mid-infrared flux - depending on the wavelength - originates from 7-8 stellar radii. The derived shell opacity profile shows a broad peak around 11 microns (tau ~ 0.06), characteristic of Mg-rich silicate dust particles.Comment: Accepted for publication in ApJ Letter

The near-infrared size-luminosity relations for Herbig Ae/Be disks

We report the results of a sensitive K-band survey of Herbig Ae/Be disk sizes using the 85-m baseline Keck Interferometer. Targets were chosen to span the maximum range of stellar properties to probe the disk size dependence on luminosity and effective temperature. For most targets, the measured near-infrared sizes (ranging from 0.2 to 4 AU) support a simple disk model possessing a central optically-thin (dust-free) cavity, ringed by hot dust emitting at the expected sublimation temperatures (T_sub~1000-1500K). Furthermore, we find a tight correlation of disk size with source luminosity R propto L^(1/2) for Ae and late Be systems (valid over more than 2 decades in luminosity), confirming earlier suggestions based on lower-quality data. Interestingly, the inferred dust-free inner cavities of the highest luminosity sources (Herbig B0-B3 stars) are under-sized compared to predictions of the optically-thin cavity model, likely due to optically-thick gas within the inner AU.Comment: Accepted by Astrophysical Journal; 24 pages, 4 figures, 4 table

Limits on Gravitational-Wave Emission from Selected Pulsars Using LIGO Data

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10^(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10^(-5) for the four closest pulsars

Interferometer Observations of Subparsec-scale Infrared Emission in the Nucleus of NGC 4151

We report novel, high-angular resolution interferometric measurements that imply the near-infrared nuclear emission in NGC 4151 is unexpectedly compact. We have observed the nucleus of NGC 4151 at 2.2 microns using the two 10-meter Keck telescopes as an interferometer and find a marginally resolved source ~0.1 pc in diameter. Our measurements rule out models in which a majority of the K band nuclear emission is produced on scales larger than this size. The interpretation of our measurement most consistent with other observations is that the emission mainly originates directly in the central accretion disk. This implies that AGN unification models invoking hot, optically thick dust may not be applicable to NGC 4151.Comment: 9 pages, 1 figure, accepted for publication in the Astrophysical Journal, Letter