First observations of Eta Car with H.E.S.S. II Eva Leser . 35th - PowerPoint PPT Presentation

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡ First observations of Eta Car with H.E.S.S. II Eva ¡Leser ¡. ¡35th ¡ICRC ¡. ¡Busan ¡. ¡Korea ¡. ¡July ¡13th ¡2017 ¡

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡ Detection of Eta Car with H.E.S.S. Eva ¡Leser ¡. ¡35th ¡ICRC ¡. ¡Busan ¡. ¡Korea ¡. ¡July ¡13th ¡2017 ¡

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡ Eta Carinae Hubble Space Telescope Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 3 ¡ July 13th 2017

Eta Carinae § Binary stellar system of luminous blue variable ~ 100 M ⊙ & O- or B- type companion ~ 30 M ⊙ § Period of 5.5 years (last periastron: June 2014) § Broad coverage in radio, mm, IR, optical and X-ray bands § hard X-ray emission established by INTEGRAL and Suzaku, but not confirmed by 2016 XMM-Newton and NuSTAR results § based on Fermi data: first full orbit observations in high energies published in 2015 Eta Carinae is the only colliding-wind binary detected in high-energy γ -rays! ¡ Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 4 ¡ July 13th 2017

Colliding-Wind Binaries as particle accelerators § Binary star systems with high-mass stars (OB-type or Wolf-Rayet), driving supersonic winds NASA's Goddard Space Flight Center/ § Particle acceleration in shock regions, Non-thermal emission predicted: T. Madura § Radio and X-rays: Synchrotron radiation e - § Gamma-rays: Inverse Compton scattering § π 0 decay p Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 5 ¡ July 13th 2017

Observations of Eta Carinae in γ -rays § Fermi (& AGILE) experiments reported high energy γ -ray emission by Eta Carinae § Low- & high-energy component in energy spectrum: 0.2 – 10 GeV & 10 – 300 GeV Periastron Fermi-LAT Reitberger et al. § 2012: H.E.S.S. paper with upper limits H.E.S.S. collaboration 2012 Apastron (2015) Fermi energy spectrum and upper limits by H.E.S.S. Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 6 ¡ July 13th 2017

The High Energy Stereoscopic System: H.E.S.S. § Imaging atmospheric Cherenkov telescope in southern hemisphere (Khomas Highland, Namibia) § 4 telescopes with 12 m diameter, one 28 m diameter telescope § Energy range: 10s of GeV - 10s of TeV § Field of view: 5°/3.5° diameter § Allows for monoscopic and stereoscopic observation modes Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 7 ¡ July 13th 2017

The 2014/2015 data set § Phase: 0.78 – 0.93 M. Balboa, R. Walter (2017) before periastron, all five H.E.S.S. telescopes -> mono- and stereoscopic reconstruction possible § Phase: 0.96 – 1.1 after periastron, 28 m diameter telescope only -> only monoscopic reconstruction § Both datasets span15 h Lightcurve of 7 years of Fermi data Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 8 ¡ July 13th 2017

Night sky background in Eta Carinae x10 higher than usual strong fluctuations NOAO/AURA/NSF Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 9 ¡ July 13th 2017

Handling the night sky background § Instrument: Study impact on instrument -> increase cameras Reaching more homogeneity in shower distributions threshold § Low-level data analysis: Increasing the first image cleaning H.E.S.S. PRELIMINARY § discard ~ 10% noisiest events from beginning § less than 1.5% pure NSB photons NSB map left in analysis § Remaining noise: § Tailored MC simulations for observations-> correctly treating NSB, turned-off pixels etc § Different analysis methods and regions with different NSB tested Profile of NSB and excessmap Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 10 ¡ July 13th 2017

The first results H.E.S.S. PRELIMINARY Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 11 ¡ July 13th 2017

Eta Car as seen with H.E.S.S. Significance map § Orbital phases: 0.78 – 0.93. 0.93-1.1 § 13.6 σ H.E.S.S. PRELIMINARY § 1070 γ in 25 h § 0.6 ± 0.57 γ /mn, signal/background = 0.2 § Energy threshold: 180 GeV Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 12 ¡ July 13th 2017

Spectral energy distribution PL ¡with ¡Index ¡4.04 ¡± ¡0.36 ¡(stat) ¡± ¡1.06 ¡(syst) ¡ before ¡periastron ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ ¡ 3.52 ¡± ¡0.23 ¡(stat) ¡± ¡0.33 ¡(syst) ¡ aNer ¡periastron ¡ H.E.S.S. PRELIMINARY Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 13 ¡ July 13th 2017

Summary and outlook § Stable detection : in monoscopic and stereoscopic mode in two independent analysis chains § Careful investigation of NSB from the very beginning § Detection before and after periastron § More details in coming paper § New data coming! § Eta Car constantly observed since 2014 ESO VLT § Next periastron in February 2020 – H.E.S.S. full orbit observations First detection of a colliding-wind binary in VHE γ -rays! Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 14 ¡ July 13th 2017

Back-up Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 15 ¡ July 14th 2017

Possible contamination? § Single gaussian can not be rejected @ 95% significance level § Contribution of southern excess ~ 20% § Contribution of NSB: Excess/100 MHz NSB = 0.04 ± 0.03 Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 16 ¡ July 14th 2017

Possible origins for source extension § Nearby weak (~6 σ ) Fermi source J1043.6-5930: distance 0.26 ° § No significant emission § Excess emission south of Eta Car: distance 0.29 ° § Analysis yields 6 σ § Maximum contribution to spectrum 20% Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 17 ¡ July 14th 2017

Source Fits Extension ¡[ ° ] ¡ Offset ¡from ¡ SkyMap ¡ nominal ¡posiAon ¡ [ ° ] ¡ Before ¡periastron ¡ 0.088 ¡± ¡0.012 ¡ 0.05 ¡ Monoscopic ¡ reconstrucQon ¡ Stereoscopic ¡ 0.143 ¡± ¡0.021 ¡ 0.06 ¡ reconstrucQon ¡ AGer ¡periastron ¡ 0.098 ¡± ¡0.010 ¡ 0.05 ¡ Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 18 ¡ July 14th 2017

Outline § Eta Car – a special case of a colliding-wind binary § H.E.S.S. § The new H.E.S.S. data set § Preparations § Results before periastron § Results after periastron § Sanity checks § Spectrum § Outlook & summary Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 19 ¡ July 14th 2017

Second phase: after periastron Significance map § After periastron, monoscopic H.E.S.S. PRELIMINARY reconstruction § Orbital phases: 0.96 – 1.1 § 10.3 σ § 540.7 γ in 15 h § 0.57 ± 0.06 γ /mn, signal/background = 0.2 § Energy threshold: 197 GeV Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 20 ¡ July 14th 2017

First phase: before periastron II Significance map § Stereoscopic reconstruction H.E.S.S. PRELIMINARY § Orbital phases: 0.78 – 0.93 § 7.2 σ § 464.2 γ in 15 h § 0.65 ± 0.09 γ /mn, § signal/background = 0.1 § Energy threshold: 220 GeV Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 21 ¡ July 14th 2017