The University of Southampton
University of Southampton Institutional Repository

NICER discovers mHz oscillations in the "clocked" burster GS 1826-238

NICER discovers mHz oscillations in the "clocked" burster GS 1826-238
NICER discovers mHz oscillations in the "clocked" burster GS 1826-238

We report the discovery with the Neutron Star Interior Composition Explorer (NICER) of mHz X-ray brightness oscillations from the "clocked burster" GS 1826-238. NICER observed the source in the periods 2017 June 20-29, July 11-13, and September 9-15, for a total useful exposure of 34 ks. Two consecutive dwells obtained on 2017 September 9 revealed highly significant oscillations at a frequency of 8 mHz. The fractional, sinusoidal modulation amplitude increases from 0.7% at 1 keV to ≈2% at 6 keV. Similar oscillations were also detected at lower significance in three additional dwells. The oscillation frequency and amplitude are consistent with those of mHz QPOs reported in other accreting neutron star systems. A thermonuclear X-ray burst was also observed on 2017 June 22. The burst properties and X-ray colors are both consistent with GS 1826 being in a soft spectral state during these observations, findings that are confirmed by ongoing monitoring with MAXI and SWIFT-BAT. Assuming that the mHz oscillations are associated with blackbody emission from the neutron star surface, modeling of the phase-resolved spectra shows that the oscillation is consistent with being produced by modulation of the temperature component of this emission. In this interpretation, the blackbody normalization, proportional to the emitting surface area, is consistent with being constant through the oscillation cycle. We place the observations in the context of the current theory of marginally stable burning and briefly discuss the potential for constraining neutron star properties using mHz oscillations.

stars: neutron, stars: oscillations, stars: rotation, X-rays: binaries, X-rays: individual (GS 1826,238)
0004-637X
1-12
Strohmayer, T. E.
491eee42-6b4e-4dcc-a7cd-2a36ac992a7d
Gendreau, K. C.
cad26609-b22d-4c1d-ada3-4af51e2cd780
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Arzoumanian, Z.
5befbba6-f6a1-47c8-ae9e-021c5d854a64
Bult, P. M.
1d8e2ea3-e139-4d79-be5f-a172a5c23097
Chakrabarty, D.
f70eba21-20cc-4f7f-87b3-ccd8716ddea1
Chenevez, J.
25a95602-9e3d-4553-a442-5f4317ff2cd6
Guillot, S.
5d521f37-303f-4a40-9f85-fbb75b960f12
Guver, T.
e8cdef32-2de7-43b5-b34c-325c01f0bfab
Homan, J.
549baf32-2442-4247-824e-21bb018b05f5
Jaisawal, G. K.
4d5dcd39-0881-426d-8ad7-f378238405ae
Keek, L.
9dcd2383-8c45-4f7c-9d3f-fae8c29385f7
Mahmoodifar, S.
8c38d862-86dd-428d-a5ff-2cdc7bbfc223
Miller, J. M.
96531558-0e8c-4894-aeeb-c51c77e93b7e
Ozel, F.
1ef4865f-ce54-4f28-b42e-29f5b835587f
Strohmayer, T. E.
491eee42-6b4e-4dcc-a7cd-2a36ac992a7d
Gendreau, K. C.
cad26609-b22d-4c1d-ada3-4af51e2cd780
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Arzoumanian, Z.
5befbba6-f6a1-47c8-ae9e-021c5d854a64
Bult, P. M.
1d8e2ea3-e139-4d79-be5f-a172a5c23097
Chakrabarty, D.
f70eba21-20cc-4f7f-87b3-ccd8716ddea1
Chenevez, J.
25a95602-9e3d-4553-a442-5f4317ff2cd6
Guillot, S.
5d521f37-303f-4a40-9f85-fbb75b960f12
Guver, T.
e8cdef32-2de7-43b5-b34c-325c01f0bfab
Homan, J.
549baf32-2442-4247-824e-21bb018b05f5
Jaisawal, G. K.
4d5dcd39-0881-426d-8ad7-f378238405ae
Keek, L.
9dcd2383-8c45-4f7c-9d3f-fae8c29385f7
Mahmoodifar, S.
8c38d862-86dd-428d-a5ff-2cdc7bbfc223
Miller, J. M.
96531558-0e8c-4894-aeeb-c51c77e93b7e
Ozel, F.
1ef4865f-ce54-4f28-b42e-29f5b835587f

Strohmayer, T. E., Gendreau, K. C., Altamirano, D., Arzoumanian, Z., Bult, P. M., Chakrabarty, D., Chenevez, J., Guillot, S., Guver, T., Homan, J., Jaisawal, G. K., Keek, L., Mahmoodifar, S., Miller, J. M. and Ozel, F. (2018) NICER discovers mHz oscillations in the "clocked" burster GS 1826-238. Astrophysical Journal, 865 (1), 1-12, [63]. (doi:10.3847/1538-4357/aada14).

Record type: Article

Abstract

We report the discovery with the Neutron Star Interior Composition Explorer (NICER) of mHz X-ray brightness oscillations from the "clocked burster" GS 1826-238. NICER observed the source in the periods 2017 June 20-29, July 11-13, and September 9-15, for a total useful exposure of 34 ks. Two consecutive dwells obtained on 2017 September 9 revealed highly significant oscillations at a frequency of 8 mHz. The fractional, sinusoidal modulation amplitude increases from 0.7% at 1 keV to ≈2% at 6 keV. Similar oscillations were also detected at lower significance in three additional dwells. The oscillation frequency and amplitude are consistent with those of mHz QPOs reported in other accreting neutron star systems. A thermonuclear X-ray burst was also observed on 2017 June 22. The burst properties and X-ray colors are both consistent with GS 1826 being in a soft spectral state during these observations, findings that are confirmed by ongoing monitoring with MAXI and SWIFT-BAT. Assuming that the mHz oscillations are associated with blackbody emission from the neutron star surface, modeling of the phase-resolved spectra shows that the oscillation is consistent with being produced by modulation of the temperature component of this emission. In this interpretation, the blackbody normalization, proportional to the emitting surface area, is consistent with being constant through the oscillation cycle. We place the observations in the context of the current theory of marginally stable burning and briefly discuss the potential for constraining neutron star properties using mHz oscillations.

Text
NICER Discovers mHz Oscillations in the "clocked" Burster GS 1826-238 - Accepted Manuscript
Download (674kB)

More information

Accepted/In Press date: 11 August 2018
e-pub ahead of print date: 21 September 2018
Keywords: stars: neutron, stars: oscillations, stars: rotation, X-rays: binaries, X-rays: individual (GS 1826,238)

Identifiers

Local EPrints ID: 425561
URI: http://eprints.soton.ac.uk/id/eprint/425561
ISSN: 0004-637X
PURE UUID: 35176ce9-6786-4302-9068-014b3780a203
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

Catalogue record

Date deposited: 24 Oct 2018 16:30
Last modified: 16 Mar 2024 04:17

Export record

Altmetrics

Contributors

Author: T. E. Strohmayer
Author: K. C. Gendreau
Author: D. Altamirano ORCID iD
Author: Z. Arzoumanian
Author: P. M. Bult
Author: D. Chakrabarty
Author: J. Chenevez
Author: S. Guillot
Author: T. Guver
Author: J. Homan
Author: G. K. Jaisawal
Author: L. Keek
Author: S. Mahmoodifar
Author: J. M. Miller
Author: F. Ozel

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×