Type I X-ray Burst Emission Reflected into the Eclipses of EXO 0748-676

Fuente: arXiv
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Auteurs principaux: Knight, Amy H., Eijnden, Jakob van den, Ingram, Adam, Matthews, James H., Motta, Sara E., Middleton, Matthew, Mancuso, Giulio C., Buisson, Douglas J. K., Altamirano, Diego, Fender, Rob, Roberts, Timothy P.
Format: Preprint
Publié: 2025
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author Knight, Amy H.
Eijnden, Jakob van den
Ingram, Adam
Matthews, James H.
Motta, Sara E.
Middleton, Matthew
Mancuso, Giulio C.
Buisson, Douglas J. K.
Altamirano, Diego
Fender, Rob
Roberts, Timothy P.
author_facet Knight, Amy H.
Eijnden, Jakob van den
Ingram, Adam
Matthews, James H.
Motta, Sara E.
Middleton, Matthew
Mancuso, Giulio C.
Buisson, Douglas J. K.
Altamirano, Diego
Fender, Rob
Roberts, Timothy P.
contents The neutron star X-ray binary, EXO 0748--676, was observed regularly by the Rossi X-ray Timing Explorer (RXTE) and XMM-Newton during its first detected outburst (1985 - 2008). These observations captured hundreds of asymmetric, energy-dependent X-ray eclipses, influenced by the ongoing ablation of the companion star and numerous Type I thermonuclear X-ray bursts. Here, we present the light curves of 22 Type I X-ray bursts observed by RXTE that coincide, fully or partially, with an X-ray eclipse. We identify nine instances where the burst occurs entirely within totality, seven bursts split across an egress, and six cases interrupted by an ingress. All in-eclipse bursts and split bursts occurred while the source was in the hard spectral state. We establish that we are not observing direct burst emission during eclipses since the companion star and the ablated outflow entirely obscure our view of the X-ray emitting region. We determine that the reflected flux from the outer accretion disc, even if maximally flared, is insufficient to explain all observations of in-eclipse X-ray bursts and instead explore scenarios whereby the emission arising from the X-ray bursts is scattered, either by a burst-induced rise in $N_{\rm{H}}$ that provides extra material, an accretion disc wind or the ablated outflow into our line of sight. However, the rarity of a burst and eclipse overlap makes it challenging to determine their origin.
format Preprint
id arxiv_https___arxiv_org_abs_2501_16324
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Type I X-ray Burst Emission Reflected into the Eclipses of EXO 0748-676
Knight, Amy H.
Eijnden, Jakob van den
Ingram, Adam
Matthews, James H.
Motta, Sara E.
Middleton, Matthew
Mancuso, Giulio C.
Buisson, Douglas J. K.
Altamirano, Diego
Fender, Rob
Roberts, Timothy P.
High Energy Astrophysical Phenomena
The neutron star X-ray binary, EXO 0748--676, was observed regularly by the Rossi X-ray Timing Explorer (RXTE) and XMM-Newton during its first detected outburst (1985 - 2008). These observations captured hundreds of asymmetric, energy-dependent X-ray eclipses, influenced by the ongoing ablation of the companion star and numerous Type I thermonuclear X-ray bursts. Here, we present the light curves of 22 Type I X-ray bursts observed by RXTE that coincide, fully or partially, with an X-ray eclipse. We identify nine instances where the burst occurs entirely within totality, seven bursts split across an egress, and six cases interrupted by an ingress. All in-eclipse bursts and split bursts occurred while the source was in the hard spectral state. We establish that we are not observing direct burst emission during eclipses since the companion star and the ablated outflow entirely obscure our view of the X-ray emitting region. We determine that the reflected flux from the outer accretion disc, even if maximally flared, is insufficient to explain all observations of in-eclipse X-ray bursts and instead explore scenarios whereby the emission arising from the X-ray bursts is scattered, either by a burst-induced rise in $N_{\rm{H}}$ that provides extra material, an accretion disc wind or the ablated outflow into our line of sight. However, the rarity of a burst and eclipse overlap makes it challenging to determine their origin.
title Type I X-ray Burst Emission Reflected into the Eclipses of EXO 0748-676
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2501.16324