We propse to continue the study of the long-termevolution of the cycloron line energy Ecyc in Her X-1. The long-term decay of Ecyc discovered in data takenbetween 1993 and 2012 (Staubert etal. 2014), was confirmed by a precise measurement by NuSTAR in August 2015, firmly estabilishing a decay by ~5 keV over the last 20 yrs (Staubert et al. 2016). However, the last observing campaign in 2016, coordinated between NuSTAR and INTEGRAL has provide evidence that the decay has ended, in fact hinting at a possible increase, similar to the increase observed between 1990 and 1993. Based on the idea , that both, this increase and the subsequent long-term decay, were most likely related to the evolving configuration of the magnetic field at the accretion mounds formed by matter accumulated in the polar regions of the accreting neutron star, Staubert 2014 and Staubert et al. 2014, 2016 had speculated that a new ncrease might happen once Ecyc had reached a low level similar to the one found whenthe line was first discovered. We therefor propose to continue the monitoring of Her X-1 during AO-15 with two observations 200 kes each (about half a year apart).
Publications
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
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
Primordial black hole dark matter in the context of extra dimensions - Friedlander, Avi, Mack, Katherine J.,Schon, Sarah,Song, Ningqiang,Vincent, Aaron C. (2022-05-01) http://ui.adsabs.harvard.edu/#abs/2022PhRvD.105j3508F
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
Temporal Coverage
2018-01-20T23:57:48Z / 2018-07-16T05:18:11Z
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.
European Space Agency, Staubert, 2025, 'The cyclotron line in Her X-1: Is there a new turn-up - deviating from the 20 year long decay?', 1.0, European Space Agency, https://doi.org/10.57780/esa-yt10mm2
