J/A+A/610/A61 SGR 1806-20 & SGR 1900+14 quasi-periodic oscill. (Pumpe+, 2018)
Search for quasi periodic signals in magnetar giant flares.
Bayesian inspection of SGR 1806-20 and SGR 1900+14.
Pumpe D., Gabler M., Steininger T., Ensslin T.A.
<Astron. Astrophys. 610, A61 (2018)>
=2018A&A...610A..61P 2018A&A...610A..61P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; X-ray sources ; Spectroscopy
Keywords: X-rays: bursts - stars: magnetars - stars: oscillations -
stars: neutron - methods: statistical
Abstract:
Quasi-periodic oscillations (QPOs) discovered in the decaying tails of
giant flares of magnetars are believed to be torsional oscillations of
neutron stars. These QPOs have a high potential to constrain
properties of high-density matter. In search for quasi-periodic
signals, we study the light curves of the giant flares of SGR 1806-20
and SGR 1900+14, with a non-parametric Bayesian signal inference
method called D3PO. The D3PO algorithm models the raw photon counts as
a continuous flux and takes the Poissonian shot noise as well as all
instrument effects into account. It reconstructs the logarithmic flux
and its power spectrum from the data. Using this fully noise-aware
method, we do not confirm previously reported frequency lines at
ν=17Hz because they fall into the noise-dominated regime. However,
we find two new potential candidates for oscillations at 9.2Hz
(SGR 1806-20) and 7.7Hz (SGR 1900+14). If these are real and the
fundamental magneto-elastic oscillations of the magnetars, current
theoretical models would favour relatively weak magnetic fields
B∼6x1013-3x1014G (SGR 1806-20) and a relatively low shear
velocity inside the crust compared to previous findings.
Description:
In the files you may find the reconstructed light curve and power
spectrum of SGR 1806-20 and SGR 1900+14, using two different
smoothness enforcing prior.
For all reconstructions we used a regular grid. Each pixel in the time
domain has volume of 1/800s and its harmonic domain 1/655Hz. The
interactive plot allows you to zoom into specific regions of interest.
Objects:
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RA (2000) DE Designation(s)
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18 08 39.32 -20 24 40.1 SGR 1806-20 = PSR J1808-2024
19 07 13. +09 19 36. SGR 1900+14 = GBS 1900+14
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 120 8 List of files
files/* . 8 Individual files
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See also:
J/A+A/496/765 : R light-curve of TT Ari (Kim+, 2009)
J/ApJ/728/9 : XTE J1701-462 quasi-periodic oscillations (Barret+, 2011)
J/MNRAS/426/1701 : High-frequency QPO in black hole binaries (Belloni+, 2012)
J/MNRAS/428/1704 : XTE J1550-564 quasi-periodic oscillations (Li+, 2013)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- FileName Name of the file in subdirectory files
14- 19 I6 --- N Number of points
21- 27 A7 --- Scale Value of 1 pixel (1)
29-120 A92 --- Title Title of the file
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Note (1): For reconstructed light curves, the "X" value of the plot, Time in s,
should be the line number divided by 800.
For reconstructed power spectra, the "X" value of the plot, Freq in Hz,
should be the line number divided by 655.
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Acknowledgements:
Daniel Pumpe, dpumpe(at)mpa-garching.mpg.de,
Michael Gabler, miga(at)mpa-garching.mpg.de
(End) Patricia Vannier [CDS] 27-Nov-2017