A dataset provided by the European Space Agency

Name: Hercules X-1: The decay of the cyclotron line energy E_cyc with time. Does it continue to decay further?
Published: 2025-03-25T09:54:38Z

Proposal ID	1220032
Obs ID	12200320001, 12200320002
Title	Hercules X-1: The decay of the cyclotron line energy E_cyc with time. Does it continue to decay further?
Download Data Associated to the proposal	https://isla.esac.esa.int/tap/download/bundle?format=ascii_curl&product_id=prop_id:1220032
DOI	https://doi.org/10.57780/esa-vtffuw8
Author	Staubert
Abstract	We propose to observe Her~X-1 during INTEGRALs AO-12 for a total observing time 400 ksec: covering a substantial part of one ``Main-On with two INTEGRAL revolutions, the first near the maximum of the ``Main-On, the second during its decay.Our general objective is to continue the long-term covering of this enigmatic source by INTEGRAL, in order to investigate the physics of generating the cyclotron line and the reasons for thevariability of E_cyc, in particular as a function of time. There is now clear evidencethat E_cyc decreased by >4 keV between 1996 and 2012. The physics behind this behavior is not understood so far, but is most likely connected to fundamental aspects of highly magnetized neutron stars: its structure and the physics of accretion. We speculate that the decrease of E_cyc is due to a progressing burial or screening of the magnetic field at the polar cap by the continuing accretion. The observational result of the secular decay of a cyclotron line energy is unique and was only possible through an intense effort of monitoring Her~X-1 with all satellite instruments capable of covering the hard X-ray range. A further objective is to continue to investigate the variation of E_cyc as a function of luminosity and of phase of the 35 day variation. In case ofacceptance of this INTEGRAL proposal, NuStar will make every effort to schedule acoordinated observation.
Publications	Background modelling for I3-ray spectroscopy with INTEGRAL/SPI - Siegert, Thomas, Diehl, Roland,Weinberger, Christoph,Pleintinger, Moritz M. M.,Greiner, Jochen,Zhang, Xiaoling (2019-06-01) http://ui.adsabs.harvard.edu/#abs/2019A&A...626A..73S Comparing simulated ²⁶Al maps to gamma-ray measurements - Pleintinger, Moritz M. M., Siegert, Thomas,Diehl, Roland,Fujimoto, Yusuke,Greiner, Jochen,Krause, Martin G. H.,Krumholz, Mark R. (2019-12-01) http://ui.adsabs.harvard.edu/#abs/2019A&A...632A..73P Cyclotron line energy in Hercules X-1: stable after the decay - Staubert, R., Ducci, L.,Ji, L.,Furst, F.,Wilms, J.,Rothschild, R. E.,Pottschmidt, K.,Brumback, M.,Harrison, F. (2020-10-01) http://ui.adsabs.harvard.edu/#abs/2020A&A...642A.196S Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV - Siegert, Thomas, Berteaud, Joanna,Calore, Francesca,Serpico, Pasquale D.,Weinberger, Christoph (2022-04-01) http://ui.adsabs.harvard.edu/#abs/2022A&A...660A.130S Extreme relativistic electron fluxes in the Earths outer radiation belt: Analysis of INTEGRAL IREM data - Meredith, Nigel P., Horne, Richard B.,Sandberg, Ingmar,Papadimitriou, Constantinos,Evans, Hugh D. R. (2017-07-01) http://ui.adsabs.harvard.edu/#abs/2017SpWea..15..917M Gamma-Ray Emission of ⁶⁰Fe and ²⁶Al Radioactivity in Our Galaxy - Wang, W., Siegert, T.,Dai, Z. G.,Diehl, R.,Greiner, J.,Heger, A.,Krause, M.,Lang, M.,Pleintinger, M. M. M.,Zhang, X. L. (2020-02-01) http://ui.adsabs.harvard.edu/#abs/2020ApJ...889..169W INTEGRAL/SPI {$gamma$}-ray line spectroscopy. Response and background characteristics - Diehl, Roland, Siegert, Thomas,Greiner, Jochen,Krause, Martin,Kretschmer, Karsten,Lang, Michael,Pleintinger, Moritz,Strong, Andrew W.,Weinberger, Christoph,Zhang, Xiaoling (2018-03-01) http://ui.adsabs.harvard.edu/#abs/2018A&A...611A..12D New hard X-ray sources discovered in the ongoing INTEGRAL Galactic plane survey after 14 yr of observations - Krivonos, Roman A., Tsygankov, Sergey S.,Mereminskiy, Ilya A.,Lutovinov, Alexander A.,Sazonov, Sergey Yu.,Sunyaev, Rashid A. (2017-09-01) http://ui.adsabs.harvard.edu/#abs/2017MNRAS.470..512K ²⁶Al gamma rays from the Galaxy with INTEGRAL/SPI - Pleintinger, Moritz M. M., Diehl, Roland,Siegert, Thomas,Greiner, Jochen,Krause, Martin G. H. (2023-04-01) http://ui.adsabs.harvard.edu/#abs/2023A&A...672A..53P Surround and Squash: the impact of superbubbles on the interstellar medium in Scorpius-Centaurus OB2 - Krause, Martin G. H., Burkert, Andreas,Diehl, Roland,Fierlinger, Katharina,Gaczkowski, Benjamin,Kroell, Daniel,Ngoumou, Judith,Roccatagliata, Veronica,Siegert, Thomas,Preibisch, Thomas (2018-11-01) http://ui.adsabs.harvard.edu/#abs/2018A&A...619A.120K The Galactic Bulge Diffuse Emission in Broadband X-Rays with NuSTAR - Perez, Kerstin, Krivonos, Roman,Wik, Daniel R. (2019-10-01) http://ui.adsabs.harvard.edu/#abs/2019ApJ...884..153P The INTEGRAL/IBIS AGN catalogue: an update - Malizia, A., Landi, R.,Molina, M.,Bassani, L.,Bazzano, A.,Bird, A. J.,Ubertini, P. (2016-07-01) http://ui.adsabs.harvard.edu/#abs/2016MNRAS.460...19M VerticaVertical position of the Sun with gamma-rays - Siegert, Thomas, (2019-12-01) http://ui.adsabs.harvard.edu/#abs/2019A&A...632L...1S Water megamaser emission in hard X-ray selected AGN - Panessa, F., Castangia, P.,Malizia, A.,Bassani, L.,Tarchi, A.,Bazzano, A.,Ubertini, P. (2020-09-01) http://ui.adsabs.harvard.edu/#abs/2020A&A...641A.162P X-ray absorption in INTEGRAL active galactic nuclei. Host galaxy inclination - Malizia, A., Bassani, L.,Stephen, J. B.,Bazzano, A.,Ubertini, P. (2020-07-01) http://ui.adsabs.harvard.edu/#abs/2020A&A...639A...5M
Temporal Coverage	2015-08-02T01:38:10Z / 2015-08-09T11:53:46Z
Version	1.0
Mission Description	The INTEGRAL (International Gamma-Ray Astrophysics Laboratory) mission, launched by the European Space Agency (ESA) on October 17, 2002, was designed to study high-energy phenomena in the universe. INTEGRAL was operating until february 2025 and it was equipped with three high-energy instruments: the Imager on Board the INTEGRAL Satellite (IBIS), the Spectrometer on INTEGRAL (SPI), and the JEM-X (Joint European Monitor for X-rays). Its Optical Monitoring Camera (OMC) provided optical V-band magnitude measurements, complementing the high-energy observations.
Creator Contact	https://www.cosmos.esa.int/web/integral/helpdesk
Date Published	2025-03-25T09:54:38Z
Publisher And Registrant	European Space Agency
Credit Guidelines	European Space Agency, Staubert, 2025, 'Hercules X-1: The decay of the cyclotron line energy E_cyc with time. Does it continue to decay further?', 1.0, European Space Agency, https://doi.org/10.57780/esa-vtffuw8