We present a radio-quiet quasar at z = 0.237 discovered "turning on" by the intermediate Palomar Transient Factory (iPTF). The transient, iPTF 16bco, was detected by iPTF in the nucleus of a galaxy ...with an archival Sloan Digital Sky Survey spectrum with weak narrow-line emission characteristic of a low-ionization nuclear emission-line region (LINER). Our follow-up spectra show the dramatic appearance of broad Balmer lines and a power-law continuum characteristic of a luminous ( erg s−1) type 1 quasar 12 yr later. Our photometric monitoring with PTF from 2009-2012 and serendipitous X-ray observations from the XMM-Newton Slew Survey in 2011 and 2015 constrain the change of state to have occurred less than 500 days before the iPTF detection. An enhanced broad H /O iii λ5007 line ratio in the type 1 state relative to other changing-look quasars also is suggestive of the most rapid change of state yet observed in a quasar. We argue that the >10 increase in Eddington ratio inferred from the brightening in UV and X-ray continuum flux is more likely due to an intrinsic change in the accretion rate of a preexisting accretion disk than an external mechanism such as variable obscuration, microlensing, or the tidal disruption of a star. However, further monitoring will be helpful in better constraining the mechanism driving this change of state. The rapid "turn-on" of the quasar is much shorter than the viscous infall timescale of an accretion disk and requires a disk instability that can develop around a black hole on timescales less than 1 yr.
Graphs and Algebras of Symmetric Functions Virchenko, Yu. P.; Danilova, L. P.
Journal of mathematical sciences (New York, N.Y.),
06/2023, Letnik:
272, Številka:
5
Journal Article
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f
n
defined on the Cartesian powers Ω
n
of a set Ω with a ...measure
μ
. Moreover, each of the coefficient functions
f
n
is obtained by means of a special mapping from graphs with
n
labeled vertices belonging to a fixed class. This technique has application to equilibrium statistical mechanics and to problems of enumeration of graphs.
We discussed the scale similarity (scaling) of solar proton time profiles in the 23rd solar cycles. In order to define of scaling availability, the approximation by the scaling function of time ...profiles of all significant events of the 23rd cycle was carried out for proton fluxes with energy ranges 10–30, 30–50, 50–60, 60–100, >100 MeV according to GOES data (a total of 185 time profiles were approximated). It is shown, that such approximation of time profiles is valid for the vast majority of events of the 23rd cycle (at least in the growth phase of proton fluxes), which allows you to determine with high precision the time of proton injection in solar proton events.
We report the first observation of an oscillatory photoconductivity response at the cyclotron-resonance harmonics in a nondegenerate 2D electron system formed on the free surface of liquid helium. ...The dc conductivity oscillations are detected for electrons occupying the ground surface subband. Their period is governed by the ratio of the microwave frequency to the cyclotron frequency. Theoretical analysis of the photoresponse in a strongly interacting electron system indicates that the observation can be explained by an oscillatory correction to the electron distribution function that appears for a large inelastic relaxation time because of photon-assisted scattering.
Abstract
Soluble α-synuclein aggregates varying in size, structure, and morphology have been closely linked to neuronal death in Parkinson’s disease. However, the heterogeneity of different ...co-existing aggregate species makes it hard to isolate and study their individual toxic properties. Here, we show a reliable non-perturbative method to separate a heterogeneous mixture of protein aggregates by size. We find that aggregates of wild-type α-synuclein smaller than 200 nm in length, formed during an in vitro aggregation reaction, cause inflammation and permeabilization of single-liposome membranes and that larger aggregates are less toxic. Studying soluble aggregates extracted from post-mortem human brains also reveals that these aggregates are similar in size and structure to the smaller aggregates formed in aggregation reactions in the test tube. Furthermore, we find that the soluble aggregates present in Parkinson’s disease brains are smaller, largely less than 100 nm, and more inflammatory compared to the larger aggregates present in control brains. This study suggests that the small non-fibrillar α-synuclein aggregates are the critical species driving neuroinflammation and disease progression.
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