A dataset provided by the European Space Agency

Name: Hercules X-1: Variability of the cyclotron line energy Ecyc and the question of NS free precession
Published: 2025-03-25T09:54:36Z

Proposal ID	0920009
Obs ID	09200090001, 09200090002, 09200090003
Title	Hercules X-1: Variability of the cyclotron line energy Ecyc and the question of NS free precession
Download Data Associated to the proposal	https://isla.esac.esa.int/tap/download/bundle?format=ascii_curl&product_id=prop_id:0920009
DOI	https://doi.org/10.57780/esa-cmsyik8
Author	Staubert
Abstract	We propose to observe Her X-1 during INTEGRAL s AO-9 for a total observing time of 600 ksec: covering one Main-On with two INTEGRAL orbits, the first near the maximum of the Main-On , the second during its decay, plus one INTEGRAL orbit during the following Short-On . Our general objective is to continue the long-term covering of this enigmatic source by INTEGRAL, in order to investigate two (intimately related) aspects: A. the physics of generating the cyclotron line and the reasons behind the variability of Ecyc as a function of time, luminosity, 35 day precession-phase and 1.24 s pulse-phase, and B. the question whether the neutron star (NS) does really precess with a period of 35 days in strict synchronization with the accretion disk. If the observed systematic variations of the shape of the pulse profiles are indeed due to the NS s precession, then we would have to conclude that the precessional period is changing by a few percent every few years, which most likely requires some changes in the structure of matter and/or magnetic field of the NS s interior. This may open a new channel to the understanding of the properties of matter at supra-nuclear densities. On the other hand, some observational results seriously challenge the idea of NS precession in Her X-1.
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 Constraints on positron annihilation kinematics in the inner Galaxy - Siegert, Thomas, Crocker, Roland M.,Diehl, Roland,Krause, Martin G. H.,Panther, Fiona H.,Pleintinger, Moritz M. M.,Weinberger, Christoph (2019-07-01) http://ui.adsabs.harvard.edu/#abs/2019A&A...627A.126S 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 Discovery of blue companions to two southern Cepheids: WW Car and FN Vel - Kovtyukh, V., Szabados, L.,Chekhonadskikh, F.,Lemasle, B.,Belik, S. (2015-04-01) http://ui.adsabs.harvard.edu/#abs/2015MNRAS.448.3567K Dose Measured On-Board INTEGRAL After More Than 12 Years in Space - Claret, Arnaud, Laurent, Philippe,Sauvageon, Aymeric,Savchenko, Volodymyr (2015-12-01) http://ui.adsabs.harvard.edu/#abs/2015ITNS...62.2784C 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 Gamma-ray spectroscopy of positron annihilation in the Milky Way - Siegert, Thomas, Diehl, Roland,Khachatryan, Gerasim,Krause, Martin G. H.,Guglielmetti, Fabrizia,Greiner, Jochen,Strong, Andrew W.,Zhang, Xiaoling (2016-02-01) http://ui.adsabs.harvard.edu/#abs/2016A&A...586A..84S INTEGRAL 11-year hard X-ray survey above 100 keV - Krivonos, R., Tsygankov, S.,Lutovinov, A.,Revnivtsev, M.,Churazov, E.,Sunyaev, R. (2015-04-01) http://ui.adsabs.harvard.edu/#abs/2015MNRAS.448.3766K 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 Leptonic origin of the 100 MeV γ-ray emission from the Galactic centre - Malyshev, D., Chernyakova, M.,Neronov, A.,Walter, R. (2015-10-01) http://ui.adsabs.harvard.edu/#abs/2015A&A...582A..11M Long-term change in the cyclotron line energy in Hercules X-1 - Staubert, R., Klochkov, D.,Wilms, J.,Postnov, K.,Shakura, N. I.,Rothschild, R. E.,Furst, F.,Harrison, F. A. (2014-12-01) http://ui.adsabs.harvard.edu/#abs/2014A&A...572A.119S 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 Search for 511 keV emission in satellite galaxies of the Milky Way with INTEGRAL/SPI - Siegert, Thomas, Diehl, Roland,Vincent, Aaron C.,Guglielmetti, Fabrizia,Krause, Martin G. H.,Boehm, Celine (2016-10-01) http://ui.adsabs.harvard.edu/#abs/2016A&A...595A..25S Searching for γ-Ray Blazar Candidates among the Unidentified INTEGRAL Sources - Massaro, F., Paggi, A.,D Abrusco, R.,Tosti, G. (2012-05-01) http://ui.adsabs.harvard.edu/#abs/2012ApJ...750L..35M Sub-GeV dark matter annihilation: limits from Milky Way observations with INTEGRAL - Siegert, Thomas, Calore, Francesca,Serpico, Pasquale Dario (2024-02-01) http://ui.adsabs.harvard.edu/#abs/2024MNRAS.528.3433S 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 Galactic ²⁶Al Emission Map as Revealed by INTEGRAL SPI - Bouchet, Laurent, Jourdain, Elisabeth,Roques, Jean-Pierre (2015-03-01) http://ui.adsabs.harvard.edu/#abs/2015ApJ...801..142B 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 The INTEGRAL/IBIS AGN catalogue - I. X-ray absorption properties versus optical classification - Malizia, A., Bassani, L.,Bazzano, A.,Bird, A. J.,Masetti, N.,Panessa, F.,Stephen, J. B.,Ubertini, P. (2012-11-01) http://ui.adsabs.harvard.edu/#abs/2012MNRAS.426.1750M Type I X-ray Bursts Detected by the JEM-X Telescope Onboard the INTEGRAL Observatory in 2003-2015 - Chelovekov, I. V., Grebenev, S. A.,Mereminskiy, I. A.,Prosvetov, A. V. (2017-12-01) http://ui.adsabs.harvard.edu/#abs/2017AstL...43..781C 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	2012-04-01T06:11:44Z / 2012-04-21T21:11:21Z
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	2025-03-25T09:54:36Z
Publisher And Registrant	European Space Agency
Credit Guidelines	European Space Agency, Staubert, 2025, 'Hercules X-1: Variability of the cyclotron line energy Ecyc and the question of NS free precession', 1.0, European Space Agency, https://doi.org/10.57780/esa-cmsyik8