A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat
The study of fast variability properties in X-ray binaries advances our understanding of the physical processes and geometric properties of the accretion flow around the compact object. In this work, we study the evolution of the timing properties of Cygnus X-1 with AstroSat/LAXPC, during the transi...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adf1a5 |
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| author | Sandeep K. Rout Federico García Mariano Méndez Abhay Kumar Santosh Vadawale David M. Russell Pei Jin |
| author_facet | Sandeep K. Rout Federico García Mariano Méndez Abhay Kumar Santosh Vadawale David M. Russell Pei Jin |
| author_sort | Sandeep K. Rout |
| collection | DOAJ |
| description | The study of fast variability properties in X-ray binaries advances our understanding of the physical processes and geometric properties of the accretion flow around the compact object. In this work, we study the evolution of the timing properties of Cygnus X-1 with AstroSat/LAXPC, during the transition of the source from the hard to soft state in 2017. We use a novel frequency-segmented technique to fit simultaneously the cross spectra and parts of the power spectra and coherence function with a multi-Lorentzian model and predict the phase lags and the complementary parts of the power spectra and coherence function. We study the evolution of the frequency and power of the main variability components that are present throughout all the states. In particular, we identify previously undetected variability components, one of which manifests as a narrow dip in the coherence function and a broad drop in the phase-lag spectrum at the same frequency. This dip in coherence, which we detect for the first time in Cygnus X-1 at energies above 3 keV, appears in a state in which the source shows high-amplitude radio variability and significant hard X-ray polarization. While the contribution of the compact jet in X-rays is debated in the literature, this study provides a new avenue for investigating jet properties as well as the geometry of the Comptonizing medium. |
| format | Article |
| id | doaj-art-6611f4f370554d8eaf3cb34d5e149c2c |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-6611f4f370554d8eaf3cb34d5e149c2c2025-08-25T16:35:40ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0199014310.3847/1538-4357/adf1a5A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSatSandeep K. Rout0https://orcid.org/0000-0001-7590-5099Federico García1https://orcid.org/0000-0001-9072-4069Mariano Méndez2https://orcid.org/0000-0003-2187-2708Abhay Kumar3https://orcid.org/0000-0001-5298-8303Santosh Vadawale4https://orcid.org/0000-0002-2050-0913David M. Russell5https://orcid.org/0000-0002-3500-631XPei Jin6https://orcid.org/0009-0000-9011-7365New York University Abu Dhabi , PO Box 129188, Abu Dhabi, UAE ; sandeep.rout@nyu.edu; Center for Astrophysics and Space Science (CASS), New York University Abu Dhabi , PO Box 129188, Abu Dhabi, UAEInstituto Argentino de Radioastronomá (CCT La Plata, CONICET; CICPBA; UNLP) , C.C.5, B1894 Villa Elisa, Buenos Aires, ArgentinaKapteyn Astronomical Institute, University of Groningen , PO Box 800, NL-9700 AV Groningen, The NetherlandsINAF Istituto di Astrofisica e Planetologia Spaziali , Via del Fosso del Cavaliere 100, 00133 Roma, ItalyPhysical Research Laboratory , Navrangpura, Ahmedabad, Gujarat 380009, IndiaNew York University Abu Dhabi , PO Box 129188, Abu Dhabi, UAE ; sandeep.rout@nyu.edu; Center for Astrophysics and Space Science (CASS), New York University Abu Dhabi , PO Box 129188, Abu Dhabi, UAEKapteyn Astronomical Institute, University of Groningen , PO Box 800, NL-9700 AV Groningen, The NetherlandsThe study of fast variability properties in X-ray binaries advances our understanding of the physical processes and geometric properties of the accretion flow around the compact object. In this work, we study the evolution of the timing properties of Cygnus X-1 with AstroSat/LAXPC, during the transition of the source from the hard to soft state in 2017. We use a novel frequency-segmented technique to fit simultaneously the cross spectra and parts of the power spectra and coherence function with a multi-Lorentzian model and predict the phase lags and the complementary parts of the power spectra and coherence function. We study the evolution of the frequency and power of the main variability components that are present throughout all the states. In particular, we identify previously undetected variability components, one of which manifests as a narrow dip in the coherence function and a broad drop in the phase-lag spectrum at the same frequency. This dip in coherence, which we detect for the first time in Cygnus X-1 at energies above 3 keV, appears in a state in which the source shows high-amplitude radio variability and significant hard X-ray polarization. While the contribution of the compact jet in X-rays is debated in the literature, this study provides a new avenue for investigating jet properties as well as the geometry of the Comptonizing medium.https://doi.org/10.3847/1538-4357/adf1a5Stellar mass black holesX-ray binary starsAccretionTime series analysis |
| spellingShingle | Sandeep K. Rout Federico García Mariano Méndez Abhay Kumar Santosh Vadawale David M. Russell Pei Jin A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat The Astrophysical Journal Stellar mass black holes X-ray binary stars Accretion Time series analysis |
| title | A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat |
| title_full | A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat |
| title_fullStr | A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat |
| title_full_unstemmed | A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat |
| title_short | A Hidden Pulse: Uncovering a New Timing Signal in Cygnus X-1 with AstroSat |
| title_sort | hidden pulse uncovering a new timing signal in cygnus x 1 with astrosat |
| topic | Stellar mass black holes X-ray binary stars Accretion Time series analysis |
| url | https://doi.org/10.3847/1538-4357/adf1a5 |
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