Ferrigno, CarloDucci, LorenzoBozzo, EnricoKretschmar, PeterKühnel, MatthiasMalacaria, ChristianPottschmidt, KatjaSantangelo, AndreaSavchenko, VolodymyrWilms, Jörn2023-08-312023-08-312016-10-24Ferrigno, Carlo, Lorenzo Ducci, Enrico Bozzo, Peter Kretschmar, Matthias Kühnel, Christian Malacaria, Katja Pottschmidt, Andrea Santangelo, Volodymyr Savchenko, and Jörn Wilms. “Two Giant Outbursts of V0332+53 Observed with INTEGRAL.” Astronomy & Astrophysics 595 (November 1, 2016): A17. https://doi.org/10.1051/0004-6361/201628865.https://doi.org/10.1051/0004-6361/201628865http://hdl.handle.net/11603/29505Context. In July 2015, the high-mass X-ray binary V0332+53 underwent a giant outburst, a decade after the previous one. V0332+53 hosts a strongly magnetized neutron star. During the 2004–2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. Aims. The long (≈100 d) and bright (Lx ≈ 10³⁸ erg s⁻¹) 2015 outburst provided the opportunity to study the unique properties of the fundamental CRSF during another outburst and to study its dependence on the X-ray luminosity. Methods. The source was observed by the INTEGRAL satellite for ~330 ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004–2005, which have so far been left unpublished. Results. We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the 3–100 keV luminosity of E₁ ∝ −0.095(8)L₃₇ keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004–2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data, we also report on the detection of a ~34 d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.6 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Attribution 4.0 International (CC BY 4.0)https://creativecommons.org/licenses/by/4.0/Text