Pulse Peak Migration during the Outburst Decay of the Magnetar SGR 1830-0645: Crustal Motion and Magnetospheric Untwisting

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dc.citation.articleNumberL27en_US
dc.citation.issueNumber2en_US
dc.citation.journalTitleThe Astrophysical Journal Lettersen_US
dc.citation.volumeNumber924en_US
dc.contributor.authorYounes, Georgeen_US
dc.contributor.authorLander, Samuel K.en_US
dc.contributor.authorBaring, Matthew G.en_US
dc.contributor.authorEnoto, Teruakien_US
dc.contributor.authorKouveliotou, Chryssaen_US
dc.contributor.authorWadiasingh, Zorawaren_US
dc.contributor.authorHo, Wynn C. G.en_US
dc.contributor.authorHarding, Alice K.en_US
dc.contributor.authorArzoumanian, Zavenen_US
dc.contributor.authorGendreau, Keithen_US
dc.contributor.authorGüver, Tolgaen_US
dc.contributor.authorHu, Chin-Pingen_US
dc.contributor.authorMalacaria, Christianen_US
dc.contributor.authorRay, Paul S.en_US
dc.contributor.authorStrohmayer, Tod E.en_US
dc.date.accessioned2022-02-04T19:19:10Zen_US
dc.date.available2022-02-04T19:19:10Zen_US
dc.date.issued2022en_US
dc.description.abstractMagnetars, isolated neutron stars with magnetic-field strengths typically ≳1014 G, exhibit distinctive months-long outburst epochs during which strong evolution of soft X-ray pulse profiles, along with nonthermal magnetospheric emission components, is often observed. Using near-daily NICER observations of the magnetar SGR 1830-0645 during the first 37 days of a recent outburst decay, a pulse peak migration in phase is clearly observed, transforming the pulse shape from an initially triple-peaked to a single-peaked profile. Such peak merging has not been seen before for a magnetar. Our high-resolution phase-resolved spectroscopic analysis reveals no significant evolution of temperature despite the complex initial pulse shape, yet the inferred surface hot spots shrink during peak migration and outburst decay. We suggest two possible origins for this evolution. For internal heating of the surface, tectonic motion of the crust may be its underlying cause. The inferred speed of this crustal motion is ≲100 m day−1, constraining the density of the driving region to ρ ∼ 1010 g cm−3, at a depth of ∼200 m. Alternatively, the hot spots could be heated by particle bombardment from a twisted magnetosphere possessing flux tubes or ropes, somewhat resembling solar coronal loops, that untwist and dissipate on the 30–40 day timescale. The peak migration may then be due to a combination of field-line footpoint motion (necessarily driven by crustal motion) and evolving surface radiation beaming. This novel data set paints a vivid picture of the dynamics associated with magnetar outbursts, yet it also highlights the need for a more generic theoretical picture where magnetosphere and crust are considered in tandem.en_US
dc.identifier.citationYounes, George, Lander, Samuel K., Baring, Matthew G., et al.. "Pulse Peak Migration during the Outburst Decay of the Magnetar SGR 1830-0645: Crustal Motion and Magnetospheric Untwisting." <i>The Astrophysical Journal Letters,</i> 924, no. 2 (2022) IOP Publishing: https://doi.org/10.3847/2041-8213/ac4700.en_US
dc.identifier.digitalYounes_2022_ApJL_924_L27en_US
dc.identifier.doihttps://doi.org/10.3847/2041-8213/ac4700en_US
dc.identifier.urihttps://hdl.handle.net/1911/111968en_US
dc.language.isoengen_US
dc.publisherIOP Publishingen_US
dc.rightsOriginal content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.en_US
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/en_US
dc.titlePulse Peak Migration during the Outburst Decay of the Magnetar SGR 1830-0645: Crustal Motion and Magnetospheric Untwistingen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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