Absence of nebular He{\sc ii} $λ$4686 constrains the UV emission from the Ultraluminous X-ray pulsar NGC~1313~X--2

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Autores principales: Gúrpide, Andrés, Segura, Noel Castro, Soria, Roberto, Middleton, Matthew
Formato: Preprint
Publicado: 2024
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author Gúrpide, Andrés
Segura, Noel Castro
Soria, Roberto
Middleton, Matthew
author_facet Gúrpide, Andrés
Segura, Noel Castro
Soria, Roberto
Middleton, Matthew
contents While much has been learned in recent decades about the X-ray emission of the extragalactic Ultraluminous X-ray sources (ULXs), their radiative output in the UV band remains poorly constrained. Understanding of the full ULX spectral energy distribution (SED) is imperative to constrain the accretion flow geometry powering them, as well as their radiative power. Here we present constraints on the UV emission of the pulsating ULX (PULX) NGC~1313~X--2 based on the absence of nebular {He{\sc ii} $λ$4686} emission in its immediate environment. To this end, we first perform multi-band spectroscopy of the ULX to derive three realistic extrapolations of the SED into the unaccessible UV, each predicting varying levels of UV luminosity. We then perform photo-ionization modelling of the bubble nebula and predict the {He{\sc ii} $λ$4686} fluxes that should have been observed based on each of the derived SEDs. We then compare these predictions with the derived upper limit on {\heii} from MUSE data, which allows us to infer a UV luminosity $L_\mathrm{UV} \lesssim 1 \times 10^{39}$ erg/s in the PULX NGC~1313~X--2. Comparing the UV luminosity inferred with other ULXs, our work suggests there may be an intrinsic difference between hard and soft ULXs, either related to different mass-transfer rates and/or the nature of the accretor. However, a statistical sample of ULXs with inferred UV luminosities is needed to fully determine the distinguishing features between hard and soft ULXs. Finally, we discuss ULXs ionising role in the context of the nebular {He{\sc ii} $λ$4686} line observed in star-forming, metal-poor galaxies.
format Preprint
id arxiv_https___arxiv_org_abs_2405_13714
institution arXiv
publishDate 2024
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spellingShingle Absence of nebular He{\sc ii} $λ$4686 constrains the UV emission from the Ultraluminous X-ray pulsar NGC~1313~X--2
Gúrpide, Andrés
Segura, Noel Castro
Soria, Roberto
Middleton, Matthew
High Energy Astrophysical Phenomena
While much has been learned in recent decades about the X-ray emission of the extragalactic Ultraluminous X-ray sources (ULXs), their radiative output in the UV band remains poorly constrained. Understanding of the full ULX spectral energy distribution (SED) is imperative to constrain the accretion flow geometry powering them, as well as their radiative power. Here we present constraints on the UV emission of the pulsating ULX (PULX) NGC~1313~X--2 based on the absence of nebular {He{\sc ii} $λ$4686} emission in its immediate environment. To this end, we first perform multi-band spectroscopy of the ULX to derive three realistic extrapolations of the SED into the unaccessible UV, each predicting varying levels of UV luminosity. We then perform photo-ionization modelling of the bubble nebula and predict the {He{\sc ii} $λ$4686} fluxes that should have been observed based on each of the derived SEDs. We then compare these predictions with the derived upper limit on {\heii} from MUSE data, which allows us to infer a UV luminosity $L_\mathrm{UV} \lesssim 1 \times 10^{39}$ erg/s in the PULX NGC~1313~X--2. Comparing the UV luminosity inferred with other ULXs, our work suggests there may be an intrinsic difference between hard and soft ULXs, either related to different mass-transfer rates and/or the nature of the accretor. However, a statistical sample of ULXs with inferred UV luminosities is needed to fully determine the distinguishing features between hard and soft ULXs. Finally, we discuss ULXs ionising role in the context of the nebular {He{\sc ii} $λ$4686} line observed in star-forming, metal-poor galaxies.
title Absence of nebular He{\sc ii} $λ$4686 constrains the UV emission from the Ultraluminous X-ray pulsar NGC~1313~X--2
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2405.13714