1,422 research outputs found
F-GAMMA: Variability Doppler factors of blazars from multiwavelength monitoring
Recent population studies have shown that the variability Doppler factors can
adequately describe blazars as a population. We use the flux density variations
found within the extensive radio multi-wavelength datasets of the F-GAMMA
program, a total of 10 frequencies from 2.64 up to 142.33 GHz, in order to
estimate the variability Doppler factors for 58 -ray bright sources,
for 20 of which no variability Doppler factor has been estimated before. We
employ specifically designed algorithms in order to obtain a model for each
flare at each frequency. We then identify each event and track its evolution
through all the available frequencies for each source. This approach allows us
to distinguish significant events producing flares from stochastic variability
in blazar jets. It also allows us to effectively constrain the variability
brightness temperature and hence the variability Doppler factor as well as
provide error estimates. Our method can produce the most accurate (16\% error
on average) estimates in the literature to date.Comment: 9 pages, 7 figures, accepted for publication in MNRA
Scale invariant jets: from blazars to microquasars
Black holes, anywhere in the stellar-mass to supermassive range, are often
associated with relativistic jets. Models suggest that jet production may be a
universal process common in all black hole systems regardless of their mass.
Although in many cases observations support such hypotheses for microquasars
and Seyfert galaxies, little is known on whether boosted blazar jets also
comply with such universal scaling laws. We use uniquely rich multiwavelength
radio light curves from the F-GAMMA program and the most accurate Doppler
factors available to date to probe blazar jets in their emission rest frame
with unprecedented accuracy. We identify for the first time a strong
correlation between the blazar intrinsic broad-band radio luminosity and black
hole mass, which extends over 9 orders of magnitude down to microquasars
scales. Our results reveal the presence of a universal scaling law that bridges
the observing and emission rest frames in beamed sources and allows us to
effectively constrain jet models. They consequently provide an independent
method for estimating the Doppler factor, and for predicting expected radio
luminosities of boosted jets operating in systems of intermediate or
tens-of-solar mass black holes, immediately applicable to cases as those
recently observed by LIGO.Comment: 13 pages, 4 figures, accepted for publication in AP
F-GAMMA: Multi-frequency radio monitoring of Fermi blazars. The 2.64 to 43 GHz Effelsberg light curves from 2007-2015
The advent of the Fermi-GST with its unprecedented capability to monitor the
entire 4 pi sky within less than 2-3 hours, introduced new standard in time
domain gamma-ray astronomy. To explore this new avenue of extragalactic physics
the F-GAMMA programme undertook the task of conducting nearly monthly,
broadband radio monitoring of selected blazars from January 2007 to January
2015. In this work we release all the light curves at 2.64, 4.85, 8.35, 10.45,
14.6, 23.05, 32, and 43 GHz and present first order derivative data products
after all necessary post-measurement corrections and quality checks; that is
flux density moments and spectral indices. The release includes 155 sources.
The effective cadence after the quality flagging is around one radio SED every
1.3 months. The coherence of each radio SED is around 40 minutes. The released
dataset includes more than measurements. The median fractional
error at the lowest frequencies (2.64-10.45 GHz) is below 2%. At the highest
frequencies (14.6-43 GHz) with limiting factor of the atmospheric conditions,
the errors range from 3% to 9%, respectively.Comment: Accepted for publication in Section: Catalogs and data of Astronomy &
Astrophysic
From Solar Proton Burning to Pionic Deuterium through the Nambu-Jona-Lasinio model of light nuclei
Within the Nambu-Jona-Lasinio model of light nuclei (the NNJL model),
describing strong low-energy nuclear interactions, we compute the width of the
energy level of the ground state of pionic deuterium. The theoretical value
fits well the experimental data. Using the cross sections for the reactions
nu_e + d -> p + p + e^- and nu_e + d -> p + n + nu_e, computed in the NNJL
model, and the experimental values of the events of these reactions, detected
by the SNO Collaboration, we compute the boron neutrino fluxes. The theoretical
values agree well with the experimental data and the theoretical predictions
within the Standard Solar Model by Bahcall. We argue the applicability of the
constraints on the astrophysical factor for the solar proton burning, imposed
by helioseismology, to the width of the energy level of the ground state of
pionic deuterium. We show that the experimental data on the width satisfy these
constraints. This testifies an indirect measurement of the recommended value of
the astrophysical factor for the solar proton burning in terrestrial
laboratories in terms of the width of the energy level of the ground state of
pionic deuterium.Comment: 10 pages, no figures, Late
Minimal symmetric Darlington synthesis
We consider the symmetric Darlington synthesis of a p x p rational symmetric
Schur function S with the constraint that the extension is of size 2p x 2p.
Under the assumption that S is strictly contractive in at least one point of
the imaginary axis, we determine the minimal McMillan degree of the extension.
In particular, we show that it is generically given by the number of zeros of
odd multiplicity of I-SS*. A constructive characterization of all such
extensions is provided in terms of a symmetric realization of S and of the
outer spectral factor of I-SS*. The authors's motivation for the problem stems
from Surface Acoustic Wave filters where physical constraints on the
electro-acoustic scattering matrix naturally raise this mathematical issue
Comparing the aesthetic experience of classic–romantic and contemporary classical music: An interview study (Online First)
Current models of aesthetic experience of music (AEM) have emerged in the recent years capitalizing on evidence from psychology and neuroscience research, thus modeling mainly cognitive and information processes in the brain. However, a large part of the empirical research on which these models are based is related to Western tonal music, while another style of Western music, namely, contemporary classical music (CCM), has been almost neglected. CCM is often dissonant and lacks a tonal hierarchical structure, as, for example, in serial musical pieces. The current study qualitatively explored aesthetic dimensions of a CCM experience by contrasting it to classic–romantic music (CM). To this end, 16 semi-structured interviews with experts of both CCM (n = 8) and CM (n = 8) were conducted. The interview guide consisted of questions relating to physiological, affective, and cognitive dimensions of music listening. We applied qualitative content analysis on the textual material and compared the emerging main and sub-themes between the groups. Our findings show that especially the categories of expectations, physiological and emotional responses, pleasurable aspects, and, lastly, existential relevance revealed striking differences which allow us to conclude that CM and CCM afford distinguishable types of AEM in listeners
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