Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, ...changing-look quasars (CLQs). These surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line AGN. To better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for CLQs across the full Sloan Digital Sky Survey (SDSS) footprint using spectroscopically confirmed quasars from the SDSS DR7 catalog. Our primary selection requires large-amplitude ( mag, mag) variability over any of the available time baselines probed by the SDSS and Pan-STARRS 1 surveys. We employ photometry from the Catalina Sky Survey to verify variability behavior in CLQ candidates where available, and confirm CLQs using optical spectroscopy from the William Herschel, MMT, Magellan, and Palomar telescopes. For our adopted signal-to-noise ratio threshold on variability of broad Hβ emission, we find 17 new CLQs, yielding a confirmation rate of 20%. These candidates are at lower Eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. Based on our sample, the CLQ fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420 increases from 1.5 to 6. We release a catalog of more than 200 highly variable candidates to facilitate future CLQ searches.
Despite their factor of ∼108 difference in black hole mass, several lines of evidence suggest possible similarities between black hole accretion flows in active galactic nuclei (AGN) and Galactic ...X-ray binaries. However, it is still unclear whether the geometry of the disk-corona system in X-ray binaries directly scales up to AGN and whether this analogy still holds in different accretion states. We test this AGN/X-ray binary analogy by comparing the observed correlations between the UV-to-X-ray spectral index ( OX) and Eddington ratio in AGN to those predicted from observations of X-ray binary outbursts. This approach probes the geometry of their disk-corona systems as they transition between different accretion states. We use new Chandra X-ray and ground-based rest-UV observations of faded "changing-look" quasars to extend this comparison to lower Eddington ratios of <10−2, where observations of X-ray binaries predict a softening of OX in AGN. We find that the observed correlations between the OX and Eddington ratio of AGN displays a remarkable similarity to accretion state transitions in prototypical X-ray binary outbursts, including an inversion of this correlation at a critical Eddington ratio of ∼10−2. Our results suggest that the structures of black hole accretion flows directly scale across a factor of ∼108 in black hole mass and across different accretion states, enabling us to apply theoretical models of X-ray binaries to explain AGN phenomenology.
The Fundamental Plane of black hole activity is a relation between X-ray luminosity, radio luminosity and black hole mass for hard-state Galactic black holes and their supermassive analogues. The ...Fundamental Plane suggests that, at low-accretion rates, the physical processes regulating the conversion of an accretion flow into radiative energy could be universal across the entire black hole mass scale. However, there is still a need to further refine the Fundamental Plane in order to better discern the radiative processes and their geometry very close to the black hole, in particular the source of hard X-rays. Further refinement is necessary because error bars on the best-fitting slopes of the Fundamental Plane are generally large, and also the inferred coefficients can be sensitive to the adopted sample of black holes. In this work, we regress the Fundamental Plane with a Bayesian technique. Our approach shows that sub-Eddington black holes emit X-ray emission that is predominantly optically thin synchrotron radiation from the jet, provided that their radio spectra are flat or inverted. X-ray emission dominated by very radiatively inefficient accretion flows is excluded at the >3σ level. We also show that it is difficult to place Fanaroff-Riley type I (FR I) galaxies on to the Fundamental Plane because their X-ray jet emission is highly affected by synchrotron cooling. On the other hand, BL Lac objects (i.e. relativistically beamed sub-Eddington AGN) fit on to the Fundamental Plane. Including a uniform subset of high-energy peaked BL Lac objects from the Sloan Digital Sky Survey, we find sub-Eddington black holes with flat/inverted radio spectra follow log L
X= (1.45 ± 0.04)log L
R− (0.88 ± 0.06)log M
BH− 6.07 ± 1.10, with σint= 0.07 ± 0.05 dex. Finally, we discuss how the effects of synchrotron cooling of jet emission from the highest black hole masses can bias Fundamental Plane regressions, perhaps leading to incorrect inferences on X-ray radiation mechanisms.
Tropical reef systems are transitioning to a new era in which the interval between recurrent bouts of coral bleaching is too short for a full recovery of mature assemblages. We analyzed bleaching ...records at 100 globally distributed reef locations from 1980 to 2016. The median return time between pairs of severe bleaching events has diminished steadily since 1980 and is now only 6 years. As global warming has progressed, tropical sea surface temperatures are warmer now during current La Niña conditions than they were during El Niño events three decades ago. Consequently, as we transition to the Anthropocene, coral bleaching is occurring more frequently in all El Niño-Southern Oscillation phases, increasing the likelihood of annual bleaching in the coming decades.
Abstract
The current sample of 12 radio-quiet isolated neutron stars that emit strongly in X-rays (XINSs) is both small and heterogeneous, limiting its usefulness for understanding the physics of ...neutron star atmospheres and cooling rates and for constraining the equation of state of neutron degenerate matter. Utilizing the ROSAT 1RXS and 2RXS data sets, in conjunction with the Sloan Digital Sky Survey Data Release 17 and other companion multiwavelength surveys, we have extended previous searches for blank-field X-ray source candidate XINSs, ultimately recovering two known XINSs while identifying 46 new, unstudied candidate fields devoid of likely multiwavelength counterparts. In this publication, we describe our selection approach and provide detailed information regarding our sample of new candidate XINSs. Future opportunities to verify or to refute these X-ray sources as isolated neutron stars by obtaining more accurate X-ray source positions, quality X-ray spectra, or deeper optical imaging are also discussed.
Social support is a known protective factor against the negative psychological impact of natural disasters. Most past research has examined how the effects of exposure to traumatic events influences ...whether someone meets diagnostic criteria for depression and posttraumatic stress disorder (PTSD); it has also suggested sequelae of disaster exposure depends on whether survivors are displaced from their homes. To capture the full range of the psychological impact of natural disasters, we examined the buffering effects of social support on depressive symptoms and cluster‐specific PTSD symptoms, with consideration of displacement status. In a survey conducted 18 to 24 months after Hurricane Katrina, 810 adults exposed to the disaster reported the number of Katrina‐related traumatic events experienced, perceived social support 2 months post‐Katrina, and cluster‐specific PTSD and depressive symptoms experienced since Katrina. Analyses assessed the moderating effects of social support and displacement and the conditional effects of displacement status. Social support significantly buffered the negative effect of Katrina‐related traumatic events on depressive symptoms, B = −0.10, p = .001, and avoidance and arousal PTSD symptoms, B = −0.02, p = .035 and B = −0.02, p = .042, respectively. Three‐way interactions were nonsignificant. Conditional effects indicated social support buffered development of depressive symptoms across all residents; however, the moderating effects of support on avoidance and arousal symptoms only appeared significant for nondisplaced residents. Results highlight the protective effects of disaster‐related social support among nondisplaced individuals, and suggest displaced individuals may require more formal supports for PTSD symptom reduction following a natural disaster.
Resumen
Spanish s by the Asociación Chilena de Estrés Traumático (ACET)
El Apoyo Social Modera los Efectos de la Exposición a Desastres Naturales sobre los Síntomas de Depresión y Trastorno de Estrés Postraumático: Efectos para Residentes Trasladados y No‐Trasladados
APOYO SOCIAL MODERA LOS EFECTOS DE LOS DESASTRES NATURALES
El apoyo social es un factor protector conocido contra el impacto psicológico negativo de los desastres naturales. La mayoría de la investigación previa ha examinado cómo la exposición a eventos traumáticos influencia la posibilidad de cumplir los criterios diagnósticos para depresión y trastorno de estrés postraumático (TEPT); también se ha sugerido que las secuelas de la exposición a desastres dependen de si los sobrevivientes son trasladados de sus hogares. Para capturar el rango completo del impacto psicológico de los desastres naturales, examinamos los efectos de amortiguadores que ejerce el apoyo social en síntomas depresivos y los dominios sintomáticos dentro del TEPT, considerando el estado de Trasladado o No‐Trasladado. En una encuesta realizada 18 a 24 meses tras el huracán Katrina, 810 adultos expuestos a ese desastre reportaron el número de eventos traumáticos experimentados relacionados con Katrina, apoyo social percibido dos meses después de Katrina, y dominios sintomáticos de TEPT y síntomas de depresión sufridos desde Katrina. El análisis examinó los efectos moderadores del apoyo social y de la situación de traslado, así como los efectos condicionales del estatus de trasladado. El apoyo social mitigó significativamente los efectos negativos de los eventos traumáticos relacionados con Katrina en síntomas depresivos, B = ‐0.10, p = .001, así como los dominios sintomáticos de evitación e hiperactivación en TEPT (B = ‐0.02, p = .035 y B = ‐0.02, p = .042, respectivamente). Las interacciones en tres direcciones fueron no significativas. Los efectos condicionales mostraron que el apoyo social amortiguó el desarrollo de síntomas depresivos en todos los individuos; sin embargo, los efectos moderadores del apoyo sobre los síntomas de evitación e hiperactivación sólo alcanzaron significancia para personas no‐trasladadas. Estos resultados enfatizan los efectos protectores del apoyo social en desastres en individuos no trasladados, y sugieren que individuos trasladados podrían requerir apoyos más formales para reducir los síntomas de TEPT después de un desastre natural.
抽象
Traditional and Simplified Chinese s by AsianSTSS
Social Support Moderates Effects of Natural Disaster Exposure on Depression and PTSD Symptoms: Effects for Displaced and Non‐Displaced Residents
Traditional Chinese
標題: 社會支持會調節天災經歷對抑鬱症及PTSD症狀的影響:在有和無跟家園分離的人的效應
撮要: 我們已知社會支持是天災導致的負面心理影響的保護因素。過往大部分研究亦檢視創傷經歷怎樣影響當事人是否符合患抑鬱症和創傷後壓力症(PTSD)的標準;亦指出天災經歷的後遺症如何, 視乎生還者是否跟家園分離。為了解天災構成的全面心理影響, 本研究檢視社會支持對於抑鬱症狀及PTSD症狀的特殊聚類構成的緩衝效應, 亦考慮到樣本與家園分離的狀況。在颶風卡特里娜發生18 至24月後, 810名經歷此天災的成人接受調查, 報告了他們經歷與此颶風相關的創傷事件數目、颶風發生兩個月後的社會支持感知、以及他們在颶風後的PTSD特殊症狀聚類和抑鬱症狀。我們分析社會支持及跟家園分離產生的調節效應, 以及跟家園分離的狀況產生的制約效應。社會支持顯著地緩衝了與颶風卡特里娜相關的創傷事件對抑鬱症狀(B = ‐0.10, p = .001)、和PTSD裡的迴避與警覺症狀(分別為B = ‐0.02, p = .035 與B = ‐0.02, p = .042)構成的負面影響。三向的交互作用並不顯著。制約效應反映, 在所有居民中社會支持都緩衝了抑鬱症狀的發展。然而, 社會支持對迴避和警覺症狀的調節效應, 卻只在沒與家園分離的樣本中顯著。結果凸顯出天災相關的社會支持對沒與家園分離的人產生保護效應, 並反映與家園分離的人可能需要更多專業支持, 以減輕天災後的PTSD症狀。
Simplified Chinese
标题: 社会支持会调节天灾经历对抑郁症及PTSD症状的影响:在有和无跟家园分离的人的效应
撮要: 我们已知社会支持是天灾导致的负面心理影响的保护因素。过往大部分研究亦检视创伤经历怎样影响当事人是否符合患抑郁症和创伤后压力症(PTSD)的标准;亦指出天灾经历的后遗症如何, 视乎生还者是否跟家园分离。为了解天灾构成的全面心理影响, 本研究检视社会支持对于抑郁症状及PTSD症状的特殊聚类构成的缓冲效应, 亦考虑到样本与家园分离的状况。在飓风卡特里娜发生18 至24月后, 810名经历此天灾的成人接受调查, 报告了他们经历与此飓风相关的创伤事件数目、飓风发生两个月后的社会支持感知、以及他们在飓风后的PTSD特殊症状聚类和抑郁症状。我们分析社会支持及跟家园分离产生的调节效应, 以及跟家园分离的状况产生的制约效应。社会支持显著地缓冲了与飓风卡特里娜相关的创伤事件对抑郁症状(B = ‐0.10, p = .001)、和PTSD里的回避与警觉症状(分别为B = ‐0.02, p = .035 与B = ‐0.02, p = .042)构成的负面影响。三向的交互作用并不显著。制约效应反映, 在所有居民中社会支持都缓冲了抑郁症状的发展。然而, 社会支持对回避和警觉症状的调节效应, 却只在没与家园分离的样本中显著。结果凸显出天灾相关的社会支持对没与家园分离的人产生保护效应, 并反映与家园分离的人可能需要更多专业支持, 以减轻天灾后的PTSD症状。
The well-known bluer-when-brighter trend observed in quasar variability is a signature of the complex processes in the accretion disk and can be a probe of the quasar variability mechanism. Using a ...sample of 604 variable quasars with repeat spectra in the Sloan Digital Sky Survey-I/II (SDSS), we construct difference spectra to investigate the physical causes of this bluer-when-brighter trend. The continuum of our composite difference spectrum is well fit by a power law, with a spectral index in excellent agreement with previous results. We measure the spectral variability relative to the underlying spectra of the quasars, which is independent of any extinction, and compare to model predictions. We show that our SDSS spectral variability results cannot be produced by global accretion rate fluctuations in a thin disk alone. However, we find that a simple model of an inhomogeneous disk with localized temperature fluctuations will produce power-law spectral variability over optical wavelengths. We show that the inhomogeneous disk will provide good fits to our observed spectral variability if the disk has large temperature fluctuations in many independently varying zones, in excellent agreement with independent constraints from quasar microlensing disk sizes, their strong UV spectral continuum, and single-band variability amplitudes. Our results provide an independent constraint on quasar variability models and add to the mounting evidence that quasar accretion disks have large localized temperature fluctuations.
We present the final Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). This catalog comprises the largest ...selection of spectroscopically confirmed quasars to date. The full catalog includes two subcatalogs (the current versions are DR16Q_v4 and DR16Q_Superset_v3 at https://data.sdss.org/sas/dr16/eboss/qso/DR16Q/): a "superset" of all SDSS-IV/eBOSS objects targeted as quasars containing 1,440,615 observations and a quasar-only catalog containing 750,414 quasars, including 225,082 new quasars appearing in an SDSS data release for the first time, as well as known quasars from SDSS-I/II/III. We present automated identification and redshift information for these quasars alongside data from visual inspections for 320,161 spectra. The quasar-only catalog is estimated to be 99.8% complete with 0.3%-1.3% contamination. Automated and visual inspection redshifts are supplemented by redshifts derived via principal component analysis and emission lines. We include emission-line redshifts for H , Hβ, Mg ii, C iii, C iv, and Ly . Identification and key characteristics generated by automated algorithms are presented for 99,856 broad absorption-line quasars and 35,686 damped Lyman alpha quasars. In addition to SDSS photometric data, we also present multiwavelength data for quasars from the Galaxy Evolution Explorer, UKIDSS, the Wide-field Infrared Survey Explorer, FIRST, ROSAT/2RXS, XMM-Newton, and Gaia. Calibrated digital optical spectra for these quasars can be obtained from the SDSS Science Archive Server.
We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band (g, r, i, z) light curves in the Pan-STARRS Medium Deep Fields. ...As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z 1 or z 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN, we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2-3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g − r to g − i and then to g − z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.
ABSTRACT Poorly understood feedback processes associated with highly luminous black hole accretion in quasars may dramatically affect the properties of their host galaxies. We search for the effect ...of quasar feedback on surrounding gas using Planck maps of the thermal Sunyaev-Zel'dovich effect (tSZ). By stacking tSZ Compton-y maps centered on the locations of 26,686 spectroscopic quasars from the Sloan Digital Sky Survey, we detect a strong but unresolved tSZ Compton-y signal at >5 significance that likely originates from a combination of virialized halo atmosphere gas and quasar feedback effects. We show that the feedback contribution to our detected quasar tSZ signal is likely to dominate over virialized halo gas by isolating the feedback tSZ component for high- and low-redshift quasars. We find that this quasar tSZ signal also scales with black hole mass and bolometric luminosity, all consistent with general expectations of quasar feedback. We estimate the mean angularly integrated Compton-y of quasars at z 1.5 to be 3.5 × 10−6 Mpc2, corresponding to mean total thermal energies in feedback and virialized halo gas of erg, and discuss the implications for quasar feedback. If confirmed, the large total thermal feedback energetics we estimate to be 5% ( 1% statistical uncertainty) of the black hole mass will have important implications for the effects of quasar feedback on the host galaxy, as well as the surrounding intergalactic medium.
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