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@ARTICLE{Aharonian:618771,
      author       = {Aharonian, F. and Ait Benkhali, F. and Aschersleben, J. and
                      Ashkar, H. and Backes, M. and Barbosa Martins, Victor and
                      Batzofin, R. and Becherini, Y. and Berge, David and
                      Bernlöhr, K. and Böttcher, M. and Boisson, C. and Bolmont,
                      J. and de Bony de Lavergne, M. and Borowska, J. and
                      Bouyahiaoui, M. and Brose, R. and Brown, A. and Brun, F. and
                      Bruno, B. and Bulik, T. and Burger-Scheidlin, C. and Caroff,
                      S. and Casanova, S. and Celic, J. and Cerruti, M. and Chand,
                      T. and Chandra, S. and Chen, A. and Chibueze, J. and
                      Chibueze, O. and Cotter, G. and Damascene Mbarubucyeye, J.
                      and Devin, J. and Djuvsland, J. and Dmytriiev, A. and
                      Egberts, K. and Einecke, S. and Ernenwein, J.-P. and
                      Fontaine, G. and Funk, S. and Gabici, S. and Gallant, Y. A.
                      and Glawion, D. and Glicenstein, J. F. and Goswami, P. and
                      Grolleron, G. and Haerer, L. and Heß, B. and Hofmann, W.
                      and Holch, Tim Lukas and Holler, M. and Huang, Zhiqiu and
                      Jamrozy, M. and Jankowsky, F. and Joshi, V. and
                      Jung-Richardt, I. and Kasai, E. and Katarzyński, K. and
                      Khangulyan, D. and Khatoon, R. and Khélifi, B. and
                      Kluźniak, W. and Komin, Nu. and Kosack, K. and Kostiunin,
                      Dmitriy and Kundu, A. and Lang, R. G. and Le Stum, S. and
                      Leitl, F. and Lemière, A. and Lemoine-Goumard, M. and
                      Lenain, J.-P. and Leuschner, F. and Mackey, J. and Malyshev,
                      D. and Martí-Devesa, G. and Marx, R. and Mehta, Abhay and
                      Meintjes, P. J. and Mitchell, A. and Moderski, R. and
                      Mohrmann, L. and Montanari, A. and Moulin, E. and Murach,
                      Thomas and de Naurois, M. and Niemiec, J. and Ohm, Stefan
                      and de Ona Wilhelmi, Emma Maria and Ostrowski, M. and Panny,
                      S. and Panter, M. and Parsons, R. D. and Pensec, U. and
                      Peron, G. and Prokhorov, D. A. and Pühlhofer, G. and Punch,
                      M. and Quirrenbach, A. and Regeard, M. and Reimer, A. and
                      Reimer, O. and Reis, I. and Ren, H. and Rieger, F. and
                      Rudak, B. and Ruiz-Velasco, E. and Sahakian, V. and
                      Salzmann, H. and Santangelo, A. and Sasaki, M. and Schäfer,
                      J. and Schüssler, F. and Schutte, H. M. and Shapopi, J. N.
                      S. and Spencer, S. and Stawarz, Ł. and Steenkamp, R. and
                      Steinmassl, S. and Steppa, C. and Streil, K. and Sushch, I.
                      and Takahashi, T. and Tanaka, T. and Taylor, Andrew and
                      Terrier, R. and Thorpe-Morgan, C. and Tluczykont, M. and
                      Unbehaun, T. and van Eldik, C. and van Soelen, B. and
                      Vecchi, M. and Venter, C. and Vink, J. and Wach, T. and
                      Wagner, S. J. and Werner, F. and Wierzcholska, A. and
                      Zacharias, M. and Zdziarski, A. A. and Zech, A. and
                      Żywucka, N.},
      collaboration = {H. E. S. S.{ Collaboration}},
      title        = {{H}.{E}.{S}.{S}. observations of the 2021 periastron
                      passage of {PSR} {B}1259-63/{LS} 2883},
      journal      = {Astronomy and astrophysics},
      volume       = {687},
      issn         = {0004-6361},
      address      = {Les Ulis},
      publisher    = {EDP Sciences},
      reportid     = {PUBDB-2024-07133, arXiv:2406.18167},
      pages        = {A219},
      year         = {2024},
      note         = {accepted to $A\&A$},
      abstract     = {PSR B1259–63/LS 2883 is a gamma-ray binary system that
                      hosts a pulsar in an eccentric orbit, with a 3.4 yr period,
                      around an O9.5Ve star (LS 2883). At orbital phases close to
                      periastron passages, the system radiates bright and variable
                      non-thermal emission, for which the temporal and spectral
                      properties of this emission are, for now, poorly understood.
                      In this regard, very high-energy (VHE) emission is
                      especially useful to study and constrain radiation processes
                      and particle acceleration in the system. We report on an
                      extensive VHE observation campaign conducted with the High
                      Energy Stereoscopic System, comprised of approximately 100 h
                      of data taken over five months, from tp − 24 days to tp +
                      127 days around the system’s 2021 periastron passage
                      (where tp is the time of periastron). We also present the
                      timing and spectral analyses of the source. The VHE light
                      curve in 2021 is consistent overall with the stacked light
                      curve of all previous observations. Within the light curve,
                      we report a VHE maximum at times coincident with the third
                      X-ray peak first detected in the 2021 X-ray light curve. In
                      the light curve – although sparsely sampled in this time
                      period – we see no VHE enhancement during the second disc
                      crossing. In addition, we see no correspondence to the 2021
                      GeV flare in the VHE light curve. The VHE spectrum obtained
                      from the analysis of the 2021 dataset is best described by a
                      power law of spectral index Γ = 2.65 ± 0.04stat ±
                      0.04sys, a value consistent with the spectral index obtained
                      from the analysis of data collected with H.E.S.S. during the
                      previous observations of the source. We report spectral
                      variability with a difference of ΔΓ = 0.56 ± 0.18stat ±
                      0.10sys at $95\%$ confidence intervals, between sub-periods
                      of the 2021 dataset. We also detail our investigation into
                      X-ray/TeV and GeV/TeV flux correlations in the 2021
                      periastron passage. We find a linear correlation between
                      contemporaneous flux values of X-ray and TeV datasets,
                      detected mainly after tp + 25 days, suggesting a change in
                      the available energy for non-thermal radiation processes. We
                      detect no significant correlation between GeV and TeV flux
                      points, within the uncertainties of the measurements, from
                      ∼tp − 23 days to ∼tp + 126 days. This suggests that
                      the GeV and TeV emission originate from different electron
                      populations.Key words: radiation mechanisms: non-thermal /
                      binaries: general / pulsars: individual: PSR B1259–63/LS
                      2883⋆ Corresponding authors; e-mail:
                      contact.hess@hess-experiment.eu},
      cin          = {$Z_GA$ / $Z_HESS$ / $Z_DV$ / $Z_DZA$ / $Z_THAT$},
      ddc          = {520},
      cid          = {$I:(DE-H253)Z_GA-20210408$ / $I:(DE-H253)Z_HESS-20210408$ /
                      $I:(DE-H253)Z_DV-20210408$ / $I:(DE-H253)Z_DZA-20230622$ /
                      $I:(DE-H253)Z_THAT-20210408$},
      pnm          = {613 - Matter and Radiation from the Universe (POF4-613)},
      pid          = {G:(DE-HGF)POF4-613},
      experiment   = {EXP:(DE-H253)CTA-20150101 / EXP:(DE-H253)HESS-20170101},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {2406.18167},
      howpublished = {arXiv:2406.18167},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2406.18167;\%\%$},
      UT           = {WOS:001272307300006},
      doi          = {10.1051/0004-6361/202449612},
      url          = {https://bib-pubdb1.desy.de/record/618771},
}