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

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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

SLIDE 1

First observations of Eta Car with H.E.S.S. II

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡

Eva ¡Leser ¡. ¡35th ¡ICRC ¡. ¡Busan ¡. ¡Korea ¡. ¡July ¡13th ¡2017 ¡

SLIDE 2

Detection of Eta Car with H.E.S.S.

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡

Eva ¡Leser ¡. ¡35th ¡ICRC ¡. ¡Busan ¡. ¡Korea ¡. ¡July ¡13th ¡2017 ¡

SLIDE 3

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

Eta Carinae

By ¡Nathan ¡Smith ¡(University ¡of ¡California, ¡Berkeley), ¡and ¡NASA ¡ Hubble Space Telescope

SLIDE 4

§ 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

Eta Carinae is the only colliding-wind binary detected in high-energy γ-rays!

¡

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 5

§ Binary star systems with high-mass stars (OB-type or Wolf-Rayet), driving supersonic winds § Particle acceleration in shock regions, Non-thermal emission predicted:

§ Radio and X-rays: Synchrotron radiation § Gamma-rays: Inverse Compton scattering § π0 decay

Colliding-Wind Binaries as particle accelerators

NASA's Goddard Space Flight Center/

T. Madura

e- p

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 6

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 § 2012: H.E.S.S. paper with upper limits

Fermi energy spectrum and upper limits by H.E.S.S.

H.E.S.S. collaboration 2012 Fermi-LAT Reitberger et al. (2015)

Periastron Apastron

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 7

§ 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

bservation modes

The High Energy Stereoscopic System: H.E.S.S.

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 8

§ Phase: 0.78 – 0.93 before periastron, all five telescopes -> mono- and stereoscopic reconstruction possible § Phase: 0.96 – 1.1 after periastron, 28 m diameter telescope only ->

nly monoscopic

reconstruction

§ Both datasets span15 h

The 2014/2015 data set

Lightcurve of 7 years of Fermi data

H.E.S.S.

M. Balboa, R. Walter (2017)

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 9

Night sky background in Eta Carinae

NOAO/AURA/NSF

x10 higher than usual strong fluctuations

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 10

Handling the night sky background

§ Instrument: Study impact on instrument -> increase cameras threshold § Low-level data analysis: Increasing the first image cleaning

§ discard ~ 10% noisiest events from beginning § less than 1.5% pure NSB photons left in analysis

§ Remaining noise:

§ Tailored MC simulations for

bservations-> correctly treating

NSB, turned-off pixels etc § Different analysis methods and regions with different NSB tested

NSB map Profile of NSB and excessmap Reaching more homogeneity in shower distributions H.E.S.S. PRELIMINARY

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 11

The first results

H.E.S.S. PRELIMINARY

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 12

Eta Car as seen with H.E.S.S.

Significance map

§ Orbital phases: 0.78 – 0.93. 0.93-1.1 § 13.6 σ § 1070 γ in 25 h § 0.6 ± 0.57 γ/mn, signal/background = 0.2 § Energy threshold: 180 GeV

H.E.S.S. PRELIMINARY

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 13

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 July 13th 2017

SLIDE 14

§ 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 § Next periastron in February 2020 – H.E.S.S. full orbit

bservations

First detection of a colliding-wind binary in VHE γ-rays!

Summary and outlook

ESO VLT

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 13th 2017

SLIDE 15

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

Back-up

SLIDE 16

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

§ 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

Possible contamination?

SLIDE 17

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea 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%

SLIDE 18

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

Source Fits

Extension ¡[°] ¡ Offset ¡from ¡ nominal ¡posiAon ¡ [°] ¡

SkyMap ¡

Before ¡periastron ¡ Monoscopic ¡ reconstrucQon ¡

0.088 ¡± ¡0.012 ¡ 0.05 ¡

Stereoscopic ¡ reconstrucQon ¡

0.143 ¡± ¡0.021 ¡ 0.06 ¡

AGer ¡periastron ¡

0.098 ¡± ¡0.010 ¡ 0.05 ¡

SLIDE 19

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

§ 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

Outline

SLIDE 20

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

Second phase: after periastron

Significance map

§ After periastron, monoscopic 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

H.E.S.S. PRELIMINARY

SLIDE 21

Eva Leser . 35th International Cosmic Ray Conference. Busan, Korea July 14th 2017

First phase: before periastron II

§ Stereoscopic reconstruction § 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

Significance map H.E.S.S. PRELIMINARY