High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability
We have performed simultaneous X-ray and optical spectroscopic observations of the low-mass X-ray binary Cygnus X-2. We have used a new data system attached to the Low Resolution Imaging Spectrograph (LRIS) instrument on Keck II to obtain spectra with a mean time resolution of 72.075 ms, simultaneou...
| Päätekijät: | , , , , |
|---|---|
| Aineistotyyppi: | Journal article |
| Kieli: | English |
| Julkaistu: |
2004
|
| _version_ | 1826260707374530560 |
|---|---|
| author | O'Brien, K Horne, K Gomer, R Oke, J van der Klis, M |
| author_facet | O'Brien, K Horne, K Gomer, R Oke, J van der Klis, M |
| author_sort | O'Brien, K |
| collection | OXFORD |
| description | We have performed simultaneous X-ray and optical spectroscopic observations of the low-mass X-ray binary Cygnus X-2. We have used a new data system attached to the Low Resolution Imaging Spectrograph (LRIS) instrument on Keck II to obtain spectra with a mean time resolution of 72.075 ms, simultaneous with pointed X-ray observations using the Proportional Counter Array (PCA) onboard RKTE. In this paper, we have analysed the variability in both wavebands on time-scales of 16 s. During our observations Cygnus X-2 covered all three branches of the Z-curve, allowing us to study how the changes in X-ray spectral state affect the optical emission. As the optical flux rises, the X-ray intensity first rises on the horizontal branch (0 < S z < 1) but then falls on the normal branch (1 < S z < 2) and flaring branch (2 < S z < 3), where S z is a rank number characterizing the position on the Z-curve. This linear increase in the optical flux with S z indicates the optical flux is a good predictor of the accretion rate (possibly normalized by its own long-term average) inferred from the Z-state S z. We have used this correlation to decompose the total X-ray count rate into three distinct spectral components. |
| first_indexed | 2024-03-06T19:09:57Z |
| format | Journal article |
| id | oxford-uuid:166d65cf-178e-4c8f-b74a-dbaeefb8049b |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T19:09:57Z |
| publishDate | 2004 |
| record_format | dspace |
| spelling | oxford-uuid:166d65cf-178e-4c8f-b74a-dbaeefb8049b2022-03-26T10:31:16ZHigh-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variabilityJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:166d65cf-178e-4c8f-b74a-dbaeefb8049bEnglishSymplectic Elements at Oxford2004O'Brien, KHorne, KGomer, ROke, Jvan der Klis, MWe have performed simultaneous X-ray and optical spectroscopic observations of the low-mass X-ray binary Cygnus X-2. We have used a new data system attached to the Low Resolution Imaging Spectrograph (LRIS) instrument on Keck II to obtain spectra with a mean time resolution of 72.075 ms, simultaneous with pointed X-ray observations using the Proportional Counter Array (PCA) onboard RKTE. In this paper, we have analysed the variability in both wavebands on time-scales of 16 s. During our observations Cygnus X-2 covered all three branches of the Z-curve, allowing us to study how the changes in X-ray spectral state affect the optical emission. As the optical flux rises, the X-ray intensity first rises on the horizontal branch (0 < S z < 1) but then falls on the normal branch (1 < S z < 2) and flaring branch (2 < S z < 3), where S z is a rank number characterizing the position on the Z-curve. This linear increase in the optical flux with S z indicates the optical flux is a good predictor of the accretion rate (possibly normalized by its own long-term average) inferred from the Z-state S z. We have used this correlation to decompose the total X-ray count rate into three distinct spectral components. |
| spellingShingle | O'Brien, K Horne, K Gomer, R Oke, J van der Klis, M High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title | High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title_full | High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title_fullStr | High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title_full_unstemmed | High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title_short | High-speed Keck II and RXTE spectroscopy of Cygnus X-2 - I. Three X-ray components revealed by correlated variability |
| title_sort | high speed keck ii and rxte spectroscopy of cygnus x 2 i three x ray components revealed by correlated variability |
| work_keys_str_mv | AT obrienk highspeedkeckiiandrxtespectroscopyofcygnusx2ithreexraycomponentsrevealedbycorrelatedvariability AT hornek highspeedkeckiiandrxtespectroscopyofcygnusx2ithreexraycomponentsrevealedbycorrelatedvariability AT gomerr highspeedkeckiiandrxtespectroscopyofcygnusx2ithreexraycomponentsrevealedbycorrelatedvariability AT okej highspeedkeckiiandrxtespectroscopyofcygnusx2ithreexraycomponentsrevealedbycorrelatedvariability AT vanderklism highspeedkeckiiandrxtespectroscopyofcygnusx2ithreexraycomponentsrevealedbycorrelatedvariability |