Visual stress, its treatment with spectral filters, and its relationship to visually induced motion sickness

We review the concept of visual stress and its relation to neurological disease. Visual stress can occur from the observation of images with unnatural spatial structure and an excess of contrast energy at spatial frequencies to which the visual system is generally most sensitive. Visual stress can often be reduced using spectral filters, provided the colour is selected with precision to suit each individual. The use of such filters and their effects on reading speed are reviewed. The filters have been shown to benefit patients with a variety of neurological conditions other than reading difficulty, all associated with an increased risk of seizures. © 2009 Elsevier Ltd

The Paschen jump as a diagnostic of the diffuse nebular continuum emission in active galactic nuclei

Research at UCI has been supported in part by the NSF grant No. AST-1907290. Support at UCI for HST programs 14744 and 15124 was provided by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. E.C. acknowledges funding support from HST program number 15413 (for Mrk 110) and NSF grant No. AST-1909199. L.C.H. is supported by the National Science Foundation of China (grant Nos. 11721303, 11991052) and the National Key R&D Program of China (2016YFA0400702). M.C.B. gratefully acknowledges support from the NSF through grant AST-2009230. V.U. acknowledges funding support from the NASA Astrophysics Data Analysis Program grant # 80NSSC20K0450. M.V. gratefully acknowledges support from the Independent Research Fund Denmark via grant No. DFF 8021-00130. G.J.F. acknowledges support by the NSF (grant Nos. 1816537, 1910687), NASA (grant Nos. ATP 17-ATP17-0141, 19-ATP19-0188), and STScI (grant Nos. HST-AR-15018 and HST-GO-16196.003-A). J.M.G. gratefully acknowledges support from NASA under the awards 80NSSC17K0126 and 80NSSC19K1638. W.N.B. acknowledges support from NSF grant No. AST-2106990.Photoionization modeling of active galactic nuclei (AGN) predicts that diffuse continuum (DC) emission from the broad-line region makes a substantial contribution to the total continuum emission from ultraviolet through near-infrared wavelengths. Evidence for this DC component is present in the strong Balmer jump feature in AGN spectra, and possibly from reverberation measurements that find longer lags than expected from disk emission alone. However, the Balmer jump region contains numerous blended emission features, making it difficult to isolate the DC emission strength. In contrast, the Paschen jump region near 8200 Å is relatively uncontaminated by other strong emission features. Here, we examine whether the Paschen jump can aid in constraining the DC contribution, using Hubble Space Telescope Space Telescope Imaging Spectrograph spectra of six nearby Seyfert 1 nuclei. The spectra appear smooth across the Paschen edge, and we find no evidence of a Paschen spectral break or jump in total flux. We fit multicomponent spectral models over the range 6800–9700 Å and find that the spectra can still be compatible with a significant DC contribution if the DC Paschen jump is offset by an opposite spectral break resulting from blended high-order Paschen emission lines. The fits imply DC contributions ranging from ∼10% to 50% at 8000 Å, but the fitting results are highly dependent on assumptions made about other model components. These degeneracies can potentially be alleviated by carrying out fits over a broader wavelength range, provided that models can accurately represent the disk continuum shape, Fe ii emission, high-order Balmer line emission, and other components.Publisher PDFPeer reviewe

Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He ii λ4686 broad emission-line light curves lag that of the 5100 +-optical continuum by 4.17+0.36-0.36 and 0.79+0.35-0.34 days, respectively. The Hβ lag relative to the 1158 ultraviolet continuum light curve measured by the Hubble Space Telescope is ∼50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ∼50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He ii(+O iii]), and Si iv(+O iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the R BLR-L AGN relation based on the past behavior of NGC 5548

Universidad y organizaciones sociales en relación a los procesos de organización popular

A partir del hecho ocurrido el pasado 2 de abril de 2013 y a modo de profundización de los procesos de organización territorial que se venían llevando adelante en el barrio de Villa Elvira, específicamente en la Unidad Básica ubicada en 7 y 629, se comenzó a trabajar desde la Facultad de Periodismo y Comunicación Social en articulación con la Juventud Peronista (JP/BA) y otros jóvenes provenientes de distintos espacios institucionales tales como, Facultad de Trabajo Social, Facultad de Arquitectura y la Facultad de Bellas Artes, para facilitar la llegada del Estado Nacional a barrios marginales que no son reconocidos como tales por el Municipio de la Ciudad de La Plata. Además se llevó adelante la generación de una red de relación con las distintas políticas públicas y sociales que se estaban ejecutando en esos lugares, impulsando la participación de jóvenes de escuelas secundarias, Plan de Finalización de Estudios Secundarios y Primarios (FinES) y en articulación con el Instituto Nacional de Economía Social y Solidaria (INAES) para la conformación de cooperativas de trabajo, Administración Nacional de la Seguridad Social (ANSES), Asignación Universal por Hijo (AUH) y programas como Impulsores de tu país para vos, Yo Mamá, Emprendedoras con Vocación Argentina (EVA), Jóvenes con más y mejor trabajo. Así como, también, trabajando en conjunto con espacios de promoción cultural como tecnopolis y turismo social. Éstas son algunas de las herramientas que el Estado Nacional generó a partir del 2003 con el cambio de paradigma y en repuesta a las demandas que la sociedad argentina venía realizando a los gobiernos neoliberales que llevaron adelante las políticas de ajuste a sectores como educación, salud, empleo, seguridad social, vivienda, industria nacional y soberanía energética, entre otros. (Párrafo extraído del texto a modo de resumen)Eje temático: Territorio - Territorio en foco: intervenciones, producción de conocimiento, y acciones colectivas desde Villa Elvira, Partido de La PlataFacultad de Trabajo Socia

UV/Optical disk reverberation lags despite a faint X-ray corona in the AGN Mrk 335

We present the first results from a 100-day Swift, NICER and ground-based X-ray/UV/optical reverberation mapping campaign of the Narrow-Line Seyfert 1 Mrk 335, when it was in an unprecedented low X-ray flux state. Despite dramatic suppression of the X-ray variability, we still observe UV/optical lags as expected from disk reverberation. Moreover, the UV/optical lags are consistent with archival observations when the X-ray luminosity was >10 times higher. Interestingly, both low- and high-flux states reveal UV/optical lags that are 6-11 times longer than expected from a thin disk. These long lags are often interpreted as due to contamination from the broad line region, however the u band excess lag (containing the Balmer jump from the diffuse continuum) is less prevalent than in other AGN. The Swift campaign showed a low X-ray-to-optical correlation (similar to previous campaigns), but NICER and ground-based monitoring continued for another two weeks, during which the optical rose to the highest level of the campaign, followed ~10 days later by a sharp rise in X-rays. While the low X-ray countrate and relatively large systematic uncertainties in the NICER background make this measurement challenging, if the optical does lead X-rays in this flare, this indicates a departure from the zeroth-order reprocessing picture. If the optical flare is due to an increase in mass accretion rate, this occurs on much shorter than the viscous timescale. Alternatively, the optical could be responding to an intrinsic rise in X-rays that is initially hidden from our line-of-sight.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 8 figures, 3 table

Universidad y organizaciones sociales en relación a los procesos de organización popular

A partir del hecho ocurrido el pasado 2 de abril de 2013 y a modo de profundización de los procesos de organización territorial que se venían llevando adelante en el barrio de Villa Elvira, específicamente en la Unidad Básica ubicada en 7 y 629, se comenzó a trabajar desde la Facultad de Periodismo y Comunicación Social en articulación con la Juventud Peronista (JP/BA) y otros jóvenes provenientes de distintos espacios institucionales tales como, Facultad de Trabajo Social, Facultad de Arquitectura y la Facultad de Bellas Artes, para facilitar la llegada del Estado Nacional a barrios marginales que no son reconocidos como tales por el Municipio de la Ciudad de La Plata. Además se llevó adelante la generación de una red de relación con las distintas políticas públicas y sociales que se estaban ejecutando en esos lugares, impulsando la participación de jóvenes de escuelas secundarias, Plan de Finalización de Estudios Secundarios y Primarios (FinES) y en articulación con el Instituto Nacional de Economía Social y Solidaria (INAES) para la conformación de cooperativas de trabajo, Administración Nacional de la Seguridad Social (ANSES), Asignación Universal por Hijo (AUH) y programas como Impulsores de tu país para vos, Yo Mamá, Emprendedoras con Vocación Argentina (EVA), Jóvenes con más y mejor trabajo. Así como, también, trabajando en conjunto con espacios de promoción cultural como tecnopolis y turismo social. Éstas son algunas de las herramientas que el Estado Nacional generó a partir del 2003 con el cambio de paradigma y en repuesta a las demandas que la sociedad argentina venía realizando a los gobiernos neoliberales que llevaron adelante las políticas de ajuste a sectores como educación, salud, empleo, seguridad social, vivienda, industria nacional y soberanía energética, entre otros. (Párrafo extraído del texto a modo de resumen)Eje temático: Territorio - Territorio en foco: intervenciones, producción de conocimiento, y acciones colectivas desde Villa Elvira, Partido de La PlataFacultad de Trabajo Socia

AGN STORM 2: V. Anomalous Behavior of the CIV Light Curve in Mrk 817

An intensive reverberation mapping campaign on the Seyfert 1 galaxy Mrk817 using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) revealed significant variations in the response of the broad UV emission lines to fluctuations in the continuum emission. The response of the prominent UV emission lines changes over a $\sim$60-day duration, resulting in distinctly different time lags in the various segments of the light curve over the 14 months observing campaign. One-dimensional echo-mapping models fit these variations if a slowly varying background is included for each emission line. These variations are more evident in the CIV light curve, which is the line least affected by intrinsic absorption in Mrk817 and least blended with neighboring emission lines. We identify five temporal windows with distinct emission line response, and measure their corresponding time delays, which range from 2 to 13 days. These temporal windows are plausibly linked to changes in the UV and X-ray obscuration occurring during these same intervals. The shortest time lags occur during periods with diminishing obscuration, whereas the longest lags occur during periods with rising obscuration. We propose that the obscuring outflow shields the ultraviolet broad lines from the ionizing continuum. The resulting change in the spectral energy distribution of the ionizing continuum, as seen by clouds at a range of distances from the nucleus, is responsible for the changes in the line response.Comment: 20 pages, 8 figures, submitted to Ap

AGN STORM 2. IV. Swift X-ray and ultraviolet/optical monitoring of Mrk 817

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble UV continuum light curves, we measure interband continuum lags, $\tau(\lambda)$, that increase with increasing wavelength roughly following $\tau(\lambda) \propto \lambda^{4/3}$, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve - the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad line region gas that sees an absorbed ionizing continuum.Comment: 20 pages, 13 figures, 3 tables, accepted for publication in Ap

AGN STORM 2. I. First results: A Change in the Weather of Mrk 817

We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad-line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura–Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad-line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission-line variability. The correlation recovered in the next 42 days of the campaign, as Mrk 817 entered a less obscured state. The short C IV and Lyα lags suggest that the accretion disk extends beyond the UV broad-line region. Unified

The James Webb Space Telescope Mission

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 $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ 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