We used photometry from the Kepler satellite to characterize the variability of four radio-loud active galactic nuclei (AGNs) on timescales from years to minutes. The Kepler satellite produced nearly ...continuous high precision data sets which provided better temporal coverage than possible with ground based observations. We have now accumulated 11 quarters of data, eight of which were reported in our previous paper. In addition to constructing power spectral densities (PSDs) and characterizing the variability of the last three quarters, we have linked together the individual quarters using a multiplicative scaling process, providing data sets spanning ~2.8 yr with >98% coverage at a 30 minute sampling rate. We compute PSDs on these connected data sets that yield power law slopes at low frequencies in the approximate range of -1.5 to -2.0, with white noise seen at higher frequencies. These PSDs are similar to those of both the individual quarters and to those of ground-based optical observations of other AGNs. We also have explored a PSD binning method intended to reduce a bias toward shallow slope fits by evenly distributing the points within the PSDs. This tends to steepen the computed PSD slopes, especially when the low frequencies are relatively poorly fit. We detected flares lasting several days in which the brightness increased by ~15%-20% in one object, as well a smaller flare in another. Two AGNs showed only small, ~1%-2%, fluctuations in brightness.
We have used Kepler photometry to characterize variability in four radio-loud active galactic nuclei (AGN; three quasars and one object tentatively identified as a Seyfert 1.5 galaxy) on timescales ...from minutes to months, comparable to the light crossing time of the accretion disk around the central supermassive black hole or the base of the relativistic jet. Kepler's almost continuous observations provide much better temporal coverage than is possible from ground-based observations. We report the first such data analyzed for quasars. We have constructed power spectral densities using eight Kepler quarters of long-cadence (30-minute) data for three AGN, six quarters for one AGN and two quarters of short-cadence (1-minute) data for all four AGN. On timescales longer than about 0.2-0.6 days, we find red noise with mean power-law slopes ranging from -1.8 to -1.2, consistent with the variability originating in turbulence either behind a shock or within an accretion disk. Each AGN has a range of red noise slopes which vary slightly by month and quarter of observation. No quasi-periodic oscillations of astrophysical origin were detected. We detected flares of several days long when brightness increased by 3%-7% in two objects. No flares on timescales of minutes to hours were detected. Our observations imply that the duty cycle for enhanced activity in these radio-loud AGN is small. These well-sampled AGN light curves provide an impetus to develop more detailed models of turbulence in jets and instabilities in accretion disks.
We present analysis of precision radial velocities (RV) of 1134 mostly red giant stars in the southern sky, selected as candidate astrometric grid objects for the Space Interferometry Mission (SIM). ...Only a few (typically, two or three) spectroscopic observations per star have been collected, with the main goal of screening binary systems. The estimated rate of spectroscopic binarity in this sample of red giants is 32 per cent at the 0.95 confidence level, and 46 per cent at the 0.75 confidence. The true binarity rate is likely to be higher, because our method is not quite sensitive to very wide binaries and low-mass companions. The estimated lower and upper bounds of stellar RV jitter for the entire sample are 24 and 51 m s..., respectively; the adopted mean value is 37 m s... A few objects of interest are identified with large variations of RV, implying abnormally high mass ratios. (ProQuest: ... denotes formulae/symbols omitted.)
It is perhaps inevitable that the academic study of learning disabilities is often undertaken by established scholars with little lived experience of the condition. So, what has it been like for ...someone from outside the academy, with a long career in the arts, who is also the father of a severely learning‐disabled young man, to write a book‐length history of learning disabilities in culture and society? How is it possible to reconcile such a biological reality with the many caveats about the social construction of the condition? How can we retain a belief in scientific analysis when the categorisation of learning‐disabled people seems to have caused as many problems as it solves? Furthermore, how can such an account be attempted when so much of the written record is by people who are placed in positions of power over learning‐disabled people and when the true voice of experience is so often silenced, or, like the author's son, silent? The attempt to answer these questions reveals a field rich with contradiction. Despite some advances, much of the social and cultural history of learning disabilities tells a tale of neglect, abandonment and abuse, with confused cultural attitudes too often shaping practice. When the telescope is reversed, however, severe learning disabilities provide us with a kind of Brechtian “alienation effect” which reveals the fault lines running through so many progressive movements and helps us to frame them historically, while also challenging assumptions about how those with severe learning disabilities are regarded and can best be given the support and freedom that they need.
Accessible summary
My son has severe learning disabilities and the experience of being his dad has changed my life. I am writing a book‐length history of learning disabilities to find out how changing attitudes have led to changing practice. I am not learning disabled.
The history of learning‐disabled people is, for the most part, painful. We should not rely too much on the accounts of those in positions of power and draw on the small amount of history told by learning‐disabled people that exists.
I explore how some of the most positive moments in history have been bad for learning‐disabled people. I explain how this can help us understand what we need to do if their lives are to be improved.
I am interested in how learning‐disabled people have been represented in culture and society, and how this affects how they live.
The Pacific Northwest National Laboratory developed a risk framework for modeling high-impact, low-frequency power grid events to support risk-informed decisions. In this paper, we briefly recap the ...framework and demonstrate its implementation for seismic and geomagnetic hazards using a benchmark reliability test system. We describe integration of a collection of models implemented to perform hazard analysis, fragility evaluation, consequence estimation, and postevent restoration. We demonstrate the value of the framework as a multihazard power grid risk assessment and management tool. The research will benefit transmission planners and emergency planners by improving their ability to maintain a resilient grid infrastructure against impacts from major events.
Precision astrometry at microarcsecond accuracy has applications for a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument ...with flexible scheduling that delivers parallaxes at about 4 muas on targets as faint as V = 20, and differential accuracy of 0.6 muas on bright targets. The science topics are drawn primarily from the team key projects, selected in 2000, for the Space Interferometry Mission PlanetQuest (SIM PlanetQuest). We use the capabilities of this mission to illustrate the importance of the next level of astrometric precision in modern astrophysics. SIM PlanetQuest is currently in the detailed design phase, having completed in 2005 all of the enabling technologies needed for the flight instrument. It will be the first space-based long-baseline Michelson interferometer designed for precision astrometry. SIM PlanetQuest will contribute strongly to many astronomical fields, including stellar and galactic astrophysics, planetary systems around nearby stars, and the study of quasar and AGN nuclei. Using differential astrometry SIM PlanetQuest will search for planets with masses as small as Earth orbiting in the 'habitable zone' around the nearest stars, and could discover many dozen if Earth-like planets are common. It will characterize the multiple-planet systems that are now known to exist, and it will be able to search for terrestrial planets around all of the candidate target stars in the Terrestrial Planet Finder and Darwin mission lists. It will be capable of detecting planets around young stars, thereby providing insights into how planetary systems are born and how they evolve with time. Precision astrometry allows the measurement of accurate dynamical masses for stars in binary systems. SIM PlanetQuest will observe significant numbers of very high- and low-mass stars, providing stellar masses to 1%, the accuracy needed to challenge physical models. Using precision proper-motion measurements, SIM PlanetQuest will probe the Galactic mass distribution, and, through studies of tidal tails, the formation and evolution of the Galactic halo. SIM PlanetQuest will contribute to cosmology through improved accuracy of the Hubble constant. With repeated astrometric measurements of the nuclei of active galaxies, SIM PlanetQuest will probe the dynamics of accretion disks around supermassive black holes, and the relativistic jets that emerge from them.
The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) mission is part of the NASA Astrophysics Medium Explorer (MIDEX) program and will perform the ...first near-infrared all-sky spectral survey from a Low Earth, sun-synchronous, polar orbit. As a space-based observatory, SPHEREx will use spectroscopy to measure hundreds of millions of galaxies and a diversity of astronomical phenomena. With this capability, SPHEREx will produce a three-dimensional map of the universe, which scientists will use to answer questions about the early universe, the history of galaxies, and the prevalence of life-sustaining molecules in planet-forming regions of space. Relying on a robust instrument design with a single observing mode, SPHEREx will map the entire sky four times during its 25-month on-orbit survey period. It will survey the sky in optical, as well as near-infrared light, specifically obtaining near-infrared 0.75-5.0\ \mu\mathrm{m} spectra every 6″ over the entire sky. SPHEREx is designed for strong scientific synergies with other missions and observatories, with a resulting goal of a rich legacy archive of data that can be used by the community on numerous scientific investigations. SPHEREx is managed by the Jet Propulsion Laboratory-a division of California Institute of Technology-for NASA's Science Mission Directorate in Washington, DC. The mission's Principal Investigator is based at Caltech, which is also developing the payload in collaboration with JPL. Ball Aerospace is supplying the spacecraft bus. The Korea Astronomy and Space Science Institute (KASI) is an instrument and science partner for the mission. Data will be processed and archived at Caltech's IPAC. In addition to scientists from Caltech, JPL, and KASI, the scientific analysis will include scientists from numerous institutions. This paper provides a preliminary overview of the mission and its concept of operation, as well as an overview of the design of the observatory's spacecraft bus, the instrument, the software architecture, the mission system, and the ground data system. A curated list of key and driving design trade studies are also presented. It is expected that subsequent planned publications will provide intermediate project updates and eventual science results from on-orbit operations.
A Midsummer Night's Dream (5.1.209-10)1 I DO NOT THINK I have ever understood Theseus's comments about acting so clearly. Because in July of this year I saw something I have never seen before: a ...group of profoundly disabled young people staging a version of Shakespeare's great comedy and making the audience see not just the play but the world afresh. More common is the use of derogatory terms about SLDs in modern drama. ...in the first few lines of Nina Raine's critically acclaimed Consent (2017) a new mother expresses relief that her baby is not "retarded" and the same vile word is used in Annie Baker's The Flick (2013) without raising an eyebrow. There are of course many playwrights and theater people actively engaged in offering us something better. ...last year I was asked for practical advice from the director and producer of Stephanie Martin's Joy (2017), a significant new play which features two young women with Down Syndrome and a lad with moderate cognitive difficulties. Because most forms of diversity-race, gender, sexual orientation, even physical disabilities-require only minimal adjustments, the hard realities of SLDs are sometimes forgotten.
PDF
