Abstract
We conduct an all-sky search for continuous gravitational waves in the LIGO O2 data from the Hanford and Livingston detectors. We search for nearly monochromatic signals with frequency ...20.0 Hz ≤
f
≤ 585.15 Hz and spin-down
Hz s
−1
. We deploy the search on the Einstein@Home volunteer-computing project and follow-up the waveforms associated with the most significant results with eight further search stages, reaching the best sensitivity ever achieved by an all-sky survey up to 500 Hz. Six of the inspected waveforms pass all the stages but they are all associated with hardware injections, which are fake signals simulated at the LIGO detector for validation purposes. We recover all these fake signals with consistent parameters. No other waveform survives, so we find no evidence of a continuous gravitational wave signal at the detectability level of our search. We constrain the
h
0
amplitude of continuous gravitational waves at the detector as a function of the signal frequency, in half-Hz bins. The most constraining upper limit at 163.0 Hz is
h
0
= 1.3 × 10
−25
, at the 90% confidence level. Our results exclude neutron stars rotating faster than 5 ms with equatorial ellipticities larger than 10
−7
closer than 100 pc. These are deformations that neutron star crusts could easily support, according to some models.
Abstract
We conduct searches for continuous gravitational waves from seven pulsars that have not been targeted in continuous wave searches of Advanced LIGO data before. We target emission at exactly ...twice the rotation frequency of the pulsars and in a small band around such a frequency. The former search assumes that the gravitational-wave quadrupole is changing in a phase-locked manner with the rotation of the pulsar. The latter search over a range of frequencies allows for differential rotation between the component emitting the radio signal and the component emitting the gravitational waves, for example the crust or magnetosphere versus the core. Timing solutions derived from the Arecibo 327 MHz Drift-Scan Pulsar Survey observations are used. No evidence of a signal is found and upper limits are set on the gravitational-wave amplitude. For one of the pulsars we probe gravitational-wave intrinsic amplitudes just a factor of 3.8 higher than the spin-down limit, assuming a canonical moment of inertia of 10
38
kg m
2
. Our tightest ellipticity constraint is 1.5 × 10
−8
, which is a value well within the range of what a neutron star crust could support.
Abstract
We present results of a search for periodic gravitational wave signals with frequencies between 20 and 400 Hz from the neutron star in the supernova remnant G347.3-0.5 using LIGO O2 public ...data. The search is deployed on the volunteer computing project Einstein@Home, with thousands of participants donating compute cycles to make this endeavour possible. We find no significant signal candidate and set the most constraining upper limits to date on the amplitude of gravitational wave signals from the target, corresponding to deformations below 10
−6
in a large part of the band. At the frequency of best strain sensitivity, near 166 Hz, we set 90% confidence upper limits on the gravitational wave intrinsic amplitude of
h
0
90
%
≈
7.0
×
10
−
26
. Over most of the frequency range our upper limits are a factor of 20 smaller than the indirect age-based upper limit.
We report results of the most sensitive search to date for periodic gravitational waves from Cassiopeia A, Vela Jr., and G347.3 with frequency between 20 and 1500 Hz. The search was made possible by ...the computing power provided by the volunteers of the Einstein@Home project and improves on previous results by a factor of 2 across the entire frequency range for all targets. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to sensitivity depths between 54 1/Hz and 83 1/Hz, depending on the target and the frequency range. At the frequency of best strain sensitivity, near 172 Hz, we set 90% confidence upper limits on the gravitational wave intrinsic amplitude of h090%≈10−25, probing ellipticity values for Vela Jr. as low as 3×10−8, assuming a distance of 200 pc.
ABSTRACT
The Fermi Large Area Telescope gamma-ray source 3FGL J2039.6–5618 contains a periodic optical and X-ray source that was predicted to be a ‘redback’ millisecond pulsar (MSP) binary system. ...However, the conclusive identification required the detection of pulsations from the putative MSP. To better constrain the orbital parameters for a directed search for gamma-ray pulsations, we obtained new optical light curves in 2017 and 2018, which revealed long-term variability from the companion star. The resulting orbital parameter constraints were used to perform a targeted gamma-ray pulsation search using the Einstein@Home-distributed volunteer computing system. This search discovered pulsations with a period of 2.65 ms, confirming the source as a binary MSP now known as PSR J2039–5617. Optical light-curve modelling is complicated, and likely biased, by asymmetric heating on the companion star and long-term variability, but we find an inclination i ≳ 60°, for a low pulsar mass between $1.1\, \mathrm{M}_{\odot } \lt M_{\rm psr} \lt $ 1.6 M⊙, and a companion mass of 0.15–$0.22\, \mathrm{M}_{\odot }$, confirming the redback classification. Timing the gamma-ray pulsations also revealed significant variability in the orbital period, which we find to be consistent with quadrupole moment variations in the companion star, suggestive of convective activity. We also find that the pulsed flux is modulated at the orbital period, potentially due to inverse Compton scattering between high-energy leptons in the pulsar wind and the companion star’s optical photon field.
HERAFitter Alekhin, S; Behnke, O; Belov, P ...
The European physical journal. C, Particles and fields,
07/2015, Letnik:
75, Številka:
7
Journal Article
Recenzirano
Odprti dostop
HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum ...Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.
Self-report survey data were collected from 797 adolescents (47.2% Latino, 52.8% Black) in North Carolina. Path analyses were conducted to examine relationships between youth perceptions of maternal ...and paternal monitoring, neighborhood crime/drugs, friends' delinquency, peer victimization, minor substance use, and major substance use. After establishing a good fitting model, multigroup models were conducted for Blacks vs. Latinos. The results indicated perceived maternal monitoring (and paternal monitoring for Latinos) was directly related to decreased exposure to neighborhood crime/drugs and friends' delinquency. For Latinos and Blacks, maternal and paternal monitoring were directly related to gateway substance use, and indirectly related to major substance use through gateway substance use. Additionally, friends' delinquency and peer victimization were directly related to gateway and major substance use for Blacks and Latinos. Thus, exposure to neighborhood crime/drugs was indirectly related to substance use through friends' delinquency and peer victimization.
Youth Development Programs (YDPs) can serve as effective mechanisms to alleviate social and psychological adversities while enhancing and developing resilience among youth. Recently, more YDPs have ...incorporated sport within Sport for Development (SFD) models to achieve these goals. Due to the growing Latino population in the US and the wide achievement gap between Latinos and other demographic populations, there is a need to explore programs that may support individual development as well as long-term change with regard to social inequality. There is also a need to better understand the ecological contexts within SFD programs and how these contexts may support underserved youth. Specifically, using an ecological systems perspective, this study seeks to explore the implementation of a sport program by a YDP in order to examine the ecological processes that may support or inhibit the efficacy of sport programs working with underserved youth. Juntos is a YDP that primarily serves Latinx youth and families by assisting youth with graduating high school and pursuing higher education opportunities. Juntos incorporates two annual soccer tournaments (i.e., Kicking it with Juntos and Copa Unidos). A qualitative case study approach was implemented in two counties in North Carolina. Interviews were conducted with tournament participants, county coordinators and planning committee members. Findings found three key themes related to three ecological levels 1. At the Microsystem level, sport was implemented to engage youth and connect to non-sport program outcomes, but divergent perceptions of goals among stakeholders potentially inhibited intentional implementation. At the Mesosystem level, sport provided a mechanism to engage in collaborative relationships and encouraged parental participation. At the Macrosystem level, sport celebrated Latino culture and attempted to address social barriers facing Latinx youth, but some aspects of culture may have created barriers to access for girls. Findings suggested that while the programs emphasized mesosystem engagement, more integration across exosystem and macrosystem levels may be needed for sustainable outcomes.
Guided by Bronfenbrenner’s bioecological framework, this study examined the roles of Latino adolescents’ reports of discrimination, neighborhood risk, parent-child conflict over culture, and parental ...support in relation to their self-esteem and depression. Analysis of self-report data from 383 ninth grade, Latino students from one Los Angeles high school was used to validate a Multigroup Structural Equation Model of self-esteem and depressive symptoms for boys and girls. As expected, self-esteem was negatively and significantly related to depressive symptoms, yet the influence of other factors were less clear. Five paths marked the influence of mothers’ and fathers’ interactions on youths’ outcomes, demonstrating a strong path from fathers’ support to adolescent self-esteem and differing paths from cultural conflict with mother and father to youth outcomes. Neighborhood risks were significantly related to boys’ and girls’ self-esteem and depressive symptoms, especially for boys. Societal discrimination was significantly related to youths’ reports of depressive symptoms yet not significantly related to self-esteem. Results are discussed in terms of applications for both practice and future research.
Experimental tests of QCD Behnke, O
Journal of physics. Conference series,
05/2008, Letnik:
110, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A brief review is presented of experimental tests of hard hadronic scattering processes at the high energy colliders HERA, LEP and TEVATRON The covered topics are: proton structure, determination of ...αs, diffractive physics, underlying event and fragmentation studies.
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