ASSOCIATING LONG-TERM gamma-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I+61 degrees 303

Ackermann M, Ajello M, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bonamente E, Brandt TJ, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cavazzuti E, Cecchi C, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, Dalton M, D'Ammando F, de Angelis A, Den Hartog PR, de Palma F, Dermer CD, Digel SW, Di Venere L, Drell PS, Dubois R, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Franckowiak A, Funk S, Fusco P, Gargano F, Gasparrini D, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hays E, Hill AB, Horan D, Hughes RE, Jogler T, Johannesson G, Johnson AS, Johnson TJ, Kawano T, Kerr M, Knoedlseder J, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Li J, Longo F, Lovellette MN, Lubrano P, Mayer M, Mazziotta MN, McEnery JE, Michelson PF, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nemmen R, Nuss E, Ohsugi T, Okumura A, Orienti M, Orlando E, Ormes JF, Paneque D, Papitto A, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Raino S, Rando R, Razzano M, Rea N, Reimer A, Reimer O, Scargle JD, Schulz A, Sgro C, Siskind EJ, Spandre G, Spinelli P, Takahashi H, Thayer JG, Thayer JB, Tinivella M, Torres DF, Tosti G, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Werner M, Winer BL, Wood KS (2013)

Publication Status: Published

Publication Type: Journal article

Publication year: 2013

Journal

Publisher: American Astronomical Society

Book Volume: 773

DOI: 10.1088/2041-8205/773/2/L35

Abstract

Gamma-ray binaries are stellar systems for which the spectral energy distribution (discounting the thermal stellar emission) peaks at high energies. Detected from radio to TeV gamma rays, the gamma-ray binary LS I + 61 degrees 303 is highly variable across all frequencies. One aspect of this system's variability is the modulation of its emission with the timescale set by the similar to 26.4960 day orbital period. Here we show that, during the time of our observations, the gamma-ray emission of LS I + 61 degrees 303 also presents a sinusoidal variability consistent with the previously known superorbital period of 1667 days. This modulation is more prominently seen at orbital phases around apastron, whereas it does not introduce a visible change close to periastron. It is also found in the appearance and disappearance of variability at the orbital period in the power spectrum of the data. This behavior could be explained by a quasi-cyclical evolution of the equatorial outflow of the Be companion star, whose features influence the conditions for generating gamma rays. These findings open the possibility to use gamma-ray observations to study the outflows of massive stars in eccentric binary systems.

Authors with CRIS profile

Involved external institutions

Institut de Ciències de l'Espai (ICE) Spain (ES) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) Italy (IT) University of Bari Aldo Moro / Università degli Studi di Bari Aldo Moro Italy (IT) Université Bordeaux 1, Sciences et Technologies France (FR) Italian Space Agency / Agenzia Spaziale Italiana (ASI) Italy (IT) École Polytechnique - Université Paris-Saclay France (FR) Deutsches Elektronen-Synchrotron DESY Germany (DE) University of Udine / Università degli Studi di Udine Italy (IT) Institut de Recherche en Astrophysique et Planétologie (IRAP) France (FR) Hiroshima University Japan (JP) Université Fédérale de Toulouse Midi-Pyrénées France (FR) Stanford University United States (USA) (US) Leopold-Franzens-Universität Innsbruck / University of Innsbruck Austria (AT) Ohio State University United States (USA) (US) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) Italy (IT) University of Montpellier / Université Montpellier France (FR) National Aeronautics and Space Administration (NASA) United States (USA) (US) University of Padua / Universita degli Studi di Padova Italy (IT) Stockholm University / Stockholms universitet Sweden (SE) U.S. Naval Research Laboratory United States (USA) (US) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) University of California, Berkeley United States (USA) (US) Sonoma State University United States (USA) (US) University of Iceland (UI) / Háskóli Íslands Iceland (IS) University of Denver United States (USA) (US) NYCB Real-Time Computing, Inc. United States (USA) (US) George Mason University United States (USA) (US)

How to cite

APA:

Ackermann, M., Ajello, M., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R.,... Wood, K.S. (2013). ASSOCIATING LONG-TERM gamma-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I+61 degrees 303. Astrophysical Journal Letters, 773. https://doi.org/10.1088/2041-8205/773/2/L35

MLA:

Ackermann, M., et al. "ASSOCIATING LONG-TERM gamma-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I+61 degrees 303." Astrophysical Journal Letters 773 (2013).

BibTeX: Download