Por favor, use este identificador para citar o enlazar a este item:
http://hdl.handle.net/10261/135486
COMPARTIR / EXPORTAR:
SHARE CORE BASE | |
Visualizar otros formatos: MARC | Dublin Core | RDF | ORE | MODS | METS | DIDL | DATACITE | |
Título: | X-ray time lags and non-linear variability in the ultraluminous X-ray sources NGC 5408 X-1 and NGC 6946 X-1 |
Autor: | Hernández-García, Lorena CSIC ORCID; Vaughan, S.; Roberts, T.P.; Middleton, M. | Palabras clave: | X-rays: individual: NGC 6946 X-1 X-rays: individual: NGC 5408 X-1 X-ray general |
Fecha de publicación: | 2015 | Editor: | Oxford University Press | Citación: | Monthly Notices of the Royal Astronomical Society 453(3): 2877- 2884 (2015) | Resumen: | We present our analysis of the X-ray variability of two ultraluminous X-ray sources (ULXs) based on multiple XMM-Newton observations. We show that the linear rms-flux relation is present in eight observations of NGC 5408 X-1 and also in three observations of NGC 6946 X-1, but data from other ULXs are generally not sufficient to constrain any rms-flux relation. The presence of this relation was previously reported in only two observations of NGC 5408 X-1; our results show that this is a persistent property of the variability of NGC 5408 X-1 and extends to at least one other variable ULX. We speculate this is a ubiquitous property of ULX variability, as it is for X-ray variability in other luminous accreting sources. We also recover the time delay between hard and soft bands in NGC 5408 X-1, with the soft band (<1 keV) delayed with respect to the hard band (>1 keV) by up to ~10 s (~0.2 rad) at frequencies above ~few mHz. For the first time, we extend the lag analysis to lower frequencies and find some evidence for a reversal of the lag, a hard lag of ~1 ks at frequencies of ~0.1 mHz. Our energy-resolved analysis shows that the time delays are energy dependent. We argue that the lag is unlikely to be a result of reflection from an accretion disc ('reverberation') based on the lack of reflection features in the spectra, and the large size of the reflector inferred from the magnitude of the lag. We also argue that associating the soft lag with a quasi-periodic oscillation (QPO) in these ULXs - and drawing an analogy between soft lags in ULXs and soft lags seen in some low-frequency QPOs of Galactic X-ray binaries - is premature. | URI: | http://hdl.handle.net/10261/135486 | DOI: | 10.1093/mnras/stv1830 | Identificadores: | doi: 10.1093/mnras/stv1830 issn: 1365-2966 e-issn: 1365-2966 |
Aparece en las colecciones: | (IAA) Artículos |
Ficheros en este ítem:
Fichero | Descripción | Tamaño | Formato | |
---|---|---|---|---|
IAA_2015-MNRAS_453.pdf | 420,25 kB | Adobe PDF | Visualizar/Abrir |
CORE Recommender
SCOPUSTM
Citations
27
checked on 13-mar-2024
WEB OF SCIENCETM
Citations
24
checked on 22-feb-2024
Page view(s)
166
checked on 27-mar-2024
Download(s)
164
checked on 27-mar-2024
Google ScholarTM
Check
Altmetric
Altmetric
NOTA: Los ítems de Digital.CSIC están protegidos por copyright, con todos los derechos reservados, a menos que se indique lo contrario.