scholarly journals ASCA Observations of the Crab-Like Pulsar PSR B0540 – 69

2000 ◽  
Vol 177 ◽  
pp. 343-346
Author(s):  
F. Nagase ◽  
T. Endo ◽  
M. Hirayama ◽  
N. Kawai ◽  
M. Itoh
Keyword(s):  
Spectral Analysis ◽  
High Stability ◽  
Pulse Frequency ◽  
Frequency Change ◽  
Archival Data ◽  
Crab Pulsar ◽  
The Past ◽  
Temporal Properties ◽  
Photon Index ◽  
Single Power

AbstractWe report on the spectral and temporal properties of the 50 ms pulsar PSR B0540–69 using ASCA archival data obtained during 1993 to 1995. From the spectral analysis it was found that the spectra of the whole (nebular and pulsed) emission and pulsed emission in the range 1-10 keV can be represented by a single power law of photon index, Γ = 2.00 ± 0.02 and Γpulsed= 1.7 ± 0.3 respectively. The parameters for pulse frequency change during 1993-1995 were obtained using the 9 pulse frequency measurements with ASCA. The parameters derived from the ASCA observations are consistent with the previous measurements, suggesting high stability of this pulsar, ΔΩ/Ω ≲ 0.5 × 10−7over the past 10 years. These results confirm similarity of this pulsar with the Crab pulsar.

scholarly journals Magnetar X-ray emission mechanisms

2012 ◽  
Vol 8 (S291) ◽  
pp. 160-160
Author(s):  
Silvia Zane
Keyword(s):  
Spectral Analysis ◽  
Physical Interpretation ◽  
Spectral Properties ◽  
Gamma Ray ◽  
X Ray ◽  
Spectral Components ◽  
Self Consistent ◽  
Photon Index ◽  
Index 2 ◽  
Surface Fields

AbstractSoft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are peculiar X-ray sources which are believed to be magnetars: ultra-magnetized neutron stars which emission is dominated by surface fields (often in excess of 1E14 G, i.e. well above the QED threshold).Spectral analysis is an important tool in magnetar astrophysics since it can provide key information on the emission mechanisms. The first attempts at modelling the persistent (i.e. outside bursts) soft X-ray (¡10 keV) spectra of AXPs proved that a model consisting of a blackbody (kT 0.3-0.6 keV) plus a power-law (photon index 2-4) could successfully reproduce the observed emission. Moreover, INTEGRAL observations have shown that, while in quiescence, magnetars emit substantial persistent radiation also at higher energies, up to a few hundreds of keV. However, a convincing physical interpretation of the various spectral components is still missing.In this talk I will focus on the interpretation of magnetar spectral properties during quiescence. I will summarise the present status of the art and the currents attempts to model the broadband persistent emission of magnetars (from IR to hard Xrays) within a self consistent, physical scenario.

Experimenting on the past: a case study on changing analysability in English ly-adverbs

2017 ◽  
Vol 21 (2) ◽  
pp. 317-340 ◽  
Author(s):  
HENDRIK DE SMET ◽  
FREEK VAN DE VELDE
Keyword(s):  
Negative Correlation ◽  
Historical Data ◽  
Frequency Change ◽  
Data Sets ◽  
The Past ◽  
Analogous Composition ◽  
Using Data ◽  
Complex Words ◽  
Experimental Findings

While it is undoubtedly true that historical data do not lend themselves well to the reproduction of experimental findings, the availability of increasingly extensive data sets has brought some experimenting within practical reach. This means that certain predictions based on a combination of synchronic observations and uniformitarian thinking are now testable. Synchronic evidence shows a negative correlation between analysability in morphologically complex words and various measures of frequency. It is therefore expected that when the frequency of morphologically complex items changes, their analysability will change along with this. If analysability decreases, this should in turn be reflected in decreasing sensitivity to priming by items with analogous composition. The latter prediction is in principle testable on diachronic data, offering a way of verifying the diachronic effect of frequency change on analysability. In this spirit, the present article examines the relation between changing frequency and priming sensitivity, as a proxy to analysability. This is done for a sample of 250 English ly-adverbs, such as roughly, blindly, publicly, etc. over the period 1950–2005, using data from the Hansard Corpus. Some of the expected relations between frequency and analysability can be shown to hold, albeit with great variation across lexical items. At the same time, much of the variation in our measure of analysability cannot be accounted for by frequency or frequency change alone.

scholarly journals Detection of gamma-ray transients with wild binary segmentation

2020 ◽  
Vol 493 (3) ◽  
pp. 4428-4441
Author(s):  
S Antier ◽  
K Barynova ◽  
P Fryzlewicz ◽  
C Lachaud ◽  
G Marchal-Duval
Keyword(s):  
Gamma Ray ◽  
Change Point Detection ◽  
Archival Data ◽  
Data Set ◽  
Temporal Properties ◽  
Background Removal ◽  
Segmentation Analysis ◽  
Binary Segmentation ◽  
Blind Search ◽  
Detection Search

ABSTRACT In the context of time domain astronomy, we present an offline detection search of gamma-ray transients using a wild binary segmentation analysis called F-WBSB targeting both short and long gamma-ray bursts (GRBs) and covering the soft and hard gamma-ray bands. We use NASA Fermi/GBM archival data as a training and testing data set. This paper describes the analysis applied to the 12 NaI detectors of the Fermi/GBM instrument. This includes background removal, change-point detection that brackets the peaks of gamma-ray flares, the evaluation of significance for each individual GBM detector, and the combination of the results among the detectors. We also explain the calibration of the ∼ 10 parameters present in the method using one week of archival data. Finally, we present our detection performance result for 60 d of a blind search analysis with F-WBSB by comparing to both the onboard and offline GBM search as well as external events found by others surveys such as Swift-BAT. We detect 42/44 onboard GBM events but also other gamma-ray flares at a rate of 1 per hour in the 4–50 keV band. Our results show that F-WBSB is capable of recovering gamma-ray flares, including the detection of soft X-ray long transients. FWBSB offers an independent identification of GRBs in combination with methods for determining spectral and temporal properties of the transient as well as localization. This is particularly useful for increasing the GRB rate and that will help the joint detection with gravitational-wave events.

scholarly journals Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4−650224

2019 ◽  
Vol 622 ◽  
pp. A211 ◽  
Author(s):  
Francesco Coti Zelati ◽  
Alessandro Papitto ◽  
Domitilla de Martino ◽  
David A. H. Buckley ◽  
Alida Odendaal ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Broad Band ◽  
Optical Emission ◽  
Bimodal Distribution ◽  
X Ray ◽  
The Past ◽  
Upper Limits ◽  
Photon Index ◽  
Multi Wavelength ◽  
Absorbed Power

We report on a multi-wavelength study of the unclassified X-ray source CXOU J110926.4−650224 (J1109). We identified the optical counterpart as a blue star with a magnitude of ∼20.1 (3300–10500 Å). The optical emission was variable on timescales from hundreds to thousands of seconds. The spectrum showed prominent emission lines with variable profiles at different epochs. Simultaneous XMM-Newton and NuSTAR observations revealed a bimodal distribution of the X-ray count rates on timescales as short as tens of seconds, as well as sporadic flaring activity. The average broad-band (0.3–79 keV) spectrum was adequately described by an absorbed power law model with photon index of Γ = 1.63  ±  0.01 (at 1σ c.l.), and the X-ray luminosity was (2.16  ±  0.04)  ×  1034 erg s−1 for a distance of 4 kpc. Based on observations with different instruments, the X-ray luminosity has remained relatively steady over the past ∼15 years. J1109 is spatially associated with the gamma-ray source FL8Y J1109.8−6500, which was detected with Fermi at an average luminosity of (1.5  ±  0.2)  ×  1034 erg s−1 (assuming the distance of J1109) over the 0.1–300 GeV energy band between 2008 and 2016. The source was undetected during ATCA radio observations that were simultaneous with NuSTAR, down to a 3σ flux upper limit of 18 μJy beam−1 (at 7.25 GHz). We show that the phenomenological properties of J1109 point to a binary transitional pulsar candidate currently in a sub-luminous accretion disk state, and that the upper limits derived for the radio emission are consistent with the expected radio luminosity for accreting neutron stars at similar X-ray luminosities.

Rethinking Legitimation: Positional and Mediated Legitimation Processes for Croatian NGOs

2019 ◽  
Vol 62 (4) ◽  
pp. 475-498
Author(s):  
Laura J. Heideman
Keyword(s):  
Civil Society ◽  
Organizational Form ◽  
Civil Society Organizations ◽  
Archival Data ◽  
Civil Society Organization ◽  
Political Transitions ◽  
Dominant Form ◽  
The Past ◽  
Multiple Audiences ◽  
New Type

How do new forms of organizations legitimate themselves? Nongovernmental organizations (NGOs) have emerged as a dominant form of civil society organization in the past 35 years, often in societies undergoing social and political transitions. This paper analyzes legitimation processes for NGOs in postwar and postcommunist Croatia using interview and archival data. Starting from a principle that legitimation is a process involving multiple audiences, I examine the mechanisms NGOs use to legitimate themselves to different audiences. I find that Croatian civil society organizations adopted the NGO organizational form to legitimate themselves to international actors, who in turn pressured the Croatian government to accept these organizations as legitimate. However, the actions NGOs took to legitimate themselves to international actors undermined their legitimacy with the Croatian public. This case demonstrates that legitimation is a challenging prospect for a new type of organization, especially given the fragile nature of mediated legitimacy and the conflicting priorities of different audiences.

Follow-up observations of the Crab pulsar with MAGIC and re-analysis of archival data

2012 ◽  
Author(s):  
T. Y. Saito ◽  
F. Dazzi ◽  
G. Giavitto ◽  
K. Hirotani ◽  
S. Klepser ◽  
...  
Keyword(s):  
Archival Data ◽  
Crab Pulsar

Resolving the Issues of Capon and APES Approach for Projecting Enhanced Spectral Estimation

2016 ◽  
Vol 6 (2) ◽  
pp. 725
Author(s):  
Kantipudi MVV Prasad ◽  
H.N. Suresh
Keyword(s):  
Signal Processing ◽  
Spectral Analysis ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Simple Technique ◽  
Spectral Estimation ◽  
Research Work ◽  
Research Community ◽  
The Past ◽  
Power Spectral

There are various applications on signal processing that is highly dependent on preciseness and accuracy of the outcomes in spectrum of signals. Hence, from the past two decades the research community has recognized the benefits, significance, as well as associated problems in carrying out a model for spectral estimation. While in-depth investigation of the existing literatures shows that there are various attempts by the researchers to solve the issues associated with spectral estimations, where majority of teh research work is inclined towards addressing problems associated with Capon and APES techniques of spectral analysis. Therefore, this paper introduces a very simple technique towards resolving the issues of Capon and APES techniques. The outcome of the study was analyzed using correlational factor and power spectral density to find the proposed system offers better spectral estimations compared to existing system.

scholarly journals From Crab Pulsar to Magnetar?

2004 ◽  
Vol 218 ◽  
pp. 257-260 ◽  
Author(s):  
A. G. Lyne
Keyword(s):  
Magnetic Field ◽  
Crab Pulsar ◽  
The Past ◽  
Interesting Possibility ◽  
Vela Pulsar ◽  
The Magnetic Field ◽  
Better Than ◽  
Field Enhancements

We review the evolution of the Crab pulsar's rotational history during the past 35 years. Representing 3.7% of the pulsar's age, it is possible to estimate the likely development of the magnetic field and characteristic age much better than previously. The increasing magnetic field of this pulsar and of other young pulsars, most dramatically the Vela pulsar, raises the interesting possibility that these objects might evolve into magnetars. We discuss the observational case for such a proposal, but note that the origin of these field enhancements may be associated with glitch activity. However, it is understood no better than the origin of the magnetar fields, but may be one and the same.

scholarly journals Archives, linked data and the digital humanities: increasing access to digitised and born-digital archives via the semantic web

2021 ◽  
Author(s):  
Ashleigh Hawkins
Keyword(s):  
Digital Humanities ◽  
Linked Data ◽  
Large Scale ◽  
Scale Up ◽  
Digital Data ◽  
Archival Data ◽  
Digital Archives ◽  
The Past ◽  
Data Production ◽  
Machine Readable

AbstractMass digitisation and the exponential growth of born-digital archives over the past two decades have resulted in an enormous volume of archives and archival data being available digitally. This has produced a valuable but under-utilised source of large-scale digital data ripe for interrogation by scholars and practitioners in the Digital Humanities. However, current digitisation approaches fall short of the requirements of digital humanists for structured, integrated, interoperable, and interrogable data. Linked Data provides a viable means of producing such data, creating machine-readable archival data suited to analysis using digital humanities research methods. While a growing body of archival scholarship and praxis has explored Linked Data, its potential to open up digitised and born-digital archives to the Digital Humanities is under-examined. This article approaches Archival Linked Data from the perspective of the Digital Humanities, extrapolating from both archival and digital humanities Linked Data scholarship to identify the benefits to digital humanists of the production and provision of access to Archival Linked Data. It will consider some of the current barriers preventing digital humanists from being able to experience the benefits of Archival Linked Data evidenced, and to fully utilise archives which have been made available digitally. The article argues for increased collaboration between the two disciplines, challenges individuals and institutions to engage with Linked Data, and suggests the incorporation of AI and low-barrier tools such as Wikidata into the Linked Data production workflow in order to scale up the production of Archival Linked Data as a means of increasing access to and utilisation of digitised and born-digital archives.

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