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Monitoring observations of SMC X-1's excursions (MOOSE)-I. Programme description and initial high state spectral results

Monitoring observations of SMC X-1's excursions (MOOSE)-I. Programme description and initial high state spectral results
Monitoring observations of SMC X-1's excursions (MOOSE)-I. Programme description and initial high state spectral results
SMC X-1 has exhibited three superorbital period excursions since the onset of X-ray monitoring beginning with the Rossi X-ray Timing Explorer's launch in 1995. TheNeutron star Interior Composition Explorer has recently probed a fourth observed excursion beginning in 2021 with our programme monitoring observations of SMC X-1’s excursions (MOOSE). These sensitive new MOOSE data probe different superorbital periods and phases within them. Spectral fits to the high-state continuum during 2021 April to 2022 January show that the intrinsic spectral shapes are characterized by a soft (kT ∼ 0.19 keV) disc component and a hard (Γ ∼ 0.7) power-law tail. When the 2021–2022 NICER observations, taken during an excursion, are compared to 2016 XMM–Newton observations (outside of an excursion), we find little evidence for intrinsic spectral variability across the high states, but find evidence for a >3σ change in the absorption, although we caution that there may be calibration differences between the two instruments. Thus, over different lengths of superorbital periods, we see little evidence for intrinsic spectral changes in the high state. Upcoming studies of the pulse profiles may shed light on the mechanism behind the excursions.
Astrophysics - High Energy Astrophysical Phenomena
0035-8711
5457–5464
Dage, Kristen C.
e40ee1bb-898d-4f6c-b902-7f3620f611aa
Brumback, McKinley
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Neilsen, Joey
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Hu, Chin-Ping
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Altamirano, Diego
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Bahramian, Arash
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Charles, Philip A.
0429b380-0754-4dc1-8def-885c7fa6a086
Clarkson, William I.
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Haggard, Daryl
29179449-da8e-4e11-9ea6-33f3e040e354
Hickox, Ryan C.
fa3d8d11-419b-4625-892f-7183fba98e8a
Kennea, Jamie
fe98d3ce-4906-4b92-bb69-0e7891f73427
Dage, Kristen C.
e40ee1bb-898d-4f6c-b902-7f3620f611aa
Brumback, McKinley
c87f4650-6acd-46b0-85b3-70938fee5684
Neilsen, Joey
9038bd94-0f91-4ff3-882e-a943be398aeb
Hu, Chin-Ping
38ee07da-9735-4ef2-9662-35d9f0dc747b
Altamirano, Diego
d5ccdb09-0b71-4303-9538-05b467be075b
Bahramian, Arash
390154f6-92b9-4e9f-9c5e-2eeaec97460a
Charles, Philip A.
0429b380-0754-4dc1-8def-885c7fa6a086
Clarkson, William I.
a67ad1b5-83da-46ae-a5f2-08700d014052
Haggard, Daryl
29179449-da8e-4e11-9ea6-33f3e040e354
Hickox, Ryan C.
fa3d8d11-419b-4625-892f-7183fba98e8a
Kennea, Jamie
fe98d3ce-4906-4b92-bb69-0e7891f73427

Dage, Kristen C., Brumback, McKinley, Neilsen, Joey, Hu, Chin-Ping, Altamirano, Diego, Bahramian, Arash, Charles, Philip A., Clarkson, William I., Haggard, Daryl, Hickox, Ryan C. and Kennea, Jamie (2022) Monitoring observations of SMC X-1's excursions (MOOSE)-I. Programme description and initial high state spectral results. Monthly Notices of the Royal Astronomical Society, 514 (4), 5457–5464. (doi:10.1093/mnras/stac1674).

Record type: Article

Abstract

SMC X-1 has exhibited three superorbital period excursions since the onset of X-ray monitoring beginning with the Rossi X-ray Timing Explorer's launch in 1995. TheNeutron star Interior Composition Explorer has recently probed a fourth observed excursion beginning in 2021 with our programme monitoring observations of SMC X-1’s excursions (MOOSE). These sensitive new MOOSE data probe different superorbital periods and phases within them. Spectral fits to the high-state continuum during 2021 April to 2022 January show that the intrinsic spectral shapes are characterized by a soft (kT ∼ 0.19 keV) disc component and a hard (Γ ∼ 0.7) power-law tail. When the 2021–2022 NICER observations, taken during an excursion, are compared to 2016 XMM–Newton observations (outside of an excursion), we find little evidence for intrinsic spectral variability across the high states, but find evidence for a >3σ change in the absorption, although we caution that there may be calibration differences between the two instruments. Thus, over different lengths of superorbital periods, we see little evidence for intrinsic spectral changes in the high state. Upcoming studies of the pulse profiles may shed light on the mechanism behind the excursions.

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2206.06558 - Accepted Manuscript
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Accepted/In Press date: 16 June 2022
e-pub ahead of print date: 16 June 2022
Published date: 9 July 2022
Additional Information: arXiv:2206.06558
Keywords: Astrophysics - High Energy Astrophysical Phenomena

Identifiers

Local EPrints ID: 469205
URI: http://eprints.soton.ac.uk/id/eprint/469205
ISSN: 0035-8711
PURE UUID: 42659e9b-0285-4eff-a42c-27ae745e41c6
ORCID for Diego Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 09 Sep 2022 16:37
Last modified: 24 Nov 2022 02:46

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Contributors

Author: Kristen C. Dage
Author: McKinley Brumback
Author: Joey Neilsen
Author: Chin-Ping Hu
Author: Arash Bahramian
Author: William I. Clarkson
Author: Daryl Haggard
Author: Ryan C. Hickox
Author: Jamie Kennea

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