Enhanced gamma-ray activity from Eta Carinae

ATel #13329; G. Piano (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Verrecchia, C. Pittori, F. Lucarelli (SSDC and INAF/OAR), M. Cardillo, C. Casentini, A. Ursi (INAF/IAPS), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), I. Donnarumma (ASI), S. Vercellone (INAF/OA-Brera), F. Gianotti, M. Trifoglio (INAF/IASF-Bo), A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF-Mi), A. Chen (Wits University), A. Argan, E. Costa, E. Del Monte, Y. Evangelista, M. Feroci, F. Lazzarotto, I. Lapshov, L. Pacciani, P. Soffitta, V. Vittorini (INAF/IAPS), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti (INAF/IASF-Bo), A. Pellizzoni, M. Pilia, A. Trois (INAF/OA-Cagliari), G. Barbiellini, E. Vallazza (INFN Trieste), F. Longo (Univ. Trieste and INFN Trieste), A. Morselli, P. Picozza (INFN and Univ. Roma Tor Vergata), M. Prest (Univ. dell'Insubria), P. Lipari, D. Zanello (INFN and Univ. Roma Sapienza), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Ferrari (Univ. Torino and CIFS), F. Paoletti (East Windsor RSD Hightstown and INAF/IAPS), A. Antonelli, P. Giommi, L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 4 Dec 2019; 13:41 UT
Credential Certification: Giovanni Piano (giovanni.piano@inaf.it)

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AGILE is detecting gamma-ray emission above 100 MeV from a source positionally consistent with the colliding wind binary Eta Carinae. Integrating from 2019-11-26 UT 00:00:00 to 2019-11-28 UT 12:00:00 (MJD: 58813.0 - 58815.5), a preliminary multi-source likelihood analysis yields a detection at coordinates (l, b) = (288.3, -0.7) +/- 0.7 deg (99% C.L. stat.) +/- 0.1 deg (syst.), with a significance above 4 sigma and a gamma-ray flux F(>100 MeV) = (2.2 +/- 0.8) x 10^-6 photons/cm^2/s.

An X-ray flare (2-10 keV) from Eta Carinae was recently detected by NICER between November 15 and 28, 2019 (ATel # 13327). The AGILE detection is coincident with the peak X-ray emission observed by NICER on November 28, 2019.

The binary system has an orbital period of 5.53 years (~2023 days). The next periastron passage should occur at the end of February 2020. This high-energy gamma-ray activity is consistent with the emission pattern of October 2008, when AGILE observed a peak gamma-ray emission from Eta Carinae a few months before the periastron passage of January 2009 (Tavani et al., ApJ 698, L142, 2009).

The AGILE-GRID detection was obtained while AGILE is observing in spinning mode, surveying a large fraction of the sky each day. The source can be monitored with the public mobile application "AGILEScience" developed by the AGILE Team, available for both Android and iOS devices.

Multifrequency observations of Eta Carinae are strongly encouraged.