J/A+A/610/A61ivo://CDS.VizieR/J/A+A/610/A61doi:10.26093/cds/vizier.36100061CDSPumpe D.Gabler M.Steininger T.Ensslin T.A.2018-03-12T09:16:55Z2018-03-02T16:01:36ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgiant-starsx-ray-sourcesspectroscopyQuasi-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 {nu}=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~6x10^13^-3x10^14^G (SGR 1806-20) and a relatively low shear velocity inside the crust compared to previous findings.2018A&A...610A..61Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/610/A61CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/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)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/610/A61https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/610/A61http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/610/A61https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/610/A61https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/610/A61http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/610/A61GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-raydefaultJ/A+A/610/A61/listList of filesplotShow the plotmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFileNameName of the file in subdirectory filesmeta.id;meta.filecharNNumber of pointsmeta.numberintScaleValue of 1 pixel (1)stat.value;instr.pixelcharTitleTitle of the filemeta.title;meta.filechar