How Not to Miss the Supernova of the Century: Gamma-Ray Alarms for a Galactic Type Ia Event

Transcription

1 Fermi satellite Swift satellite How Not to Miss the Supernova of the Century: Gamma-Ray Alarms for a Galactic Type Ia Event Xilu Wang Brian D. Fields University of Illinois at Urbana and Champaign Amy Yarleen Lien(NASA/GSFC) Kepler s SNR Credit: NASA/ESA/JHU/R.Sankri t & W.Blair

2 A Galactic SN Ia May Be Unnoticed ØOptical or IR? large extinction in the plane > faint A V >10 us MW SN Ia ØRadio or soft X-ray? not seen for SN2014J ØNeutrinos? > weak and in low energy (see Kneller s poster; and Horiuchi s talk for Galactic CCSN neutrino) Ø GW? > frequency lower than LIGO sensitivity ØA Galactic SN Ia could happen anywhere any time >It s possible that we ll miss it! 6/26/17 1

3 Type Ia SN: Gamma-rays as monitor of (confirmed by SN2014J) 56 Ni 56 Co a Galactic SN Ia τ =8.8days 56 Co + γ τ =111.3days Line energy span from 158keV to 2.6MeV MW is optically thin to gamma-rays. A gamma-ray detector is in need: sensitive to above energy range; continuously monitors the sky! 56 Fe + γ 6/26/17 2

4 Fermi Gamma-ray Burst Monitor Credit: Fermi website PARAMETER Energy range Energy resolution Field of view CURRENT CAPABILITY ~8 kev 40 MeV NaI: 8 kev 1 MeV BGO: 150 kev 40 MeV 12% FWHM at 511keV 9.5 steradian 6/26/17 3

5 Swift Credit: Swift website Detectors Energy range BAT (Burst Alert Telescope) kev XRT (X-ray Telescope) kev UVOT (Ultraviolet and Optical Telescope) nm 6/26/17 4

6 Nearest Recent Type Ia: SN2014J 2014J in M82, at 3.5Mpc INTEGRAL/SPI data: Jan 31- Apr Ni lines and 56 Co lines seen ~20 days after the explosion Strong 56 Co line detection at late times SN2014J in M82 Credit: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright 56 Ni 56 Co + γ 56 Co 56 Fe + γ Normalize to the observation 6/26/17 5 Credit: Credit: Churazov Diehl et et al. al

7 If a Galactic SN Ia goes off, how will we confirm the signal is from a SN Ia? GRB This is not a SN! τ 56 Ni τ 56 Co = 8.8 days = days 6/26/17 6

8 Galactic Type Ia Alarm: Approach Galactic SN Ia: Use earliest SN2014J detection at 17 days to constrain the parameters in a Ejecta+shell model Fiducial distance: 10 kpc Expanding v~5000 km/s SN Ejecta us D~10kpc MW SN Ia observer 56 Ni core 56 Ni shell (opt. thin) 6/26/17 7

9 PRELIMINARY GBM Spectra Day τ 56 Ni τ 56 Co = 8.8 days = days Ni 158keV Co 847keV 6/26/17 8

10 PRELIMINARY BAT Spectra Day Ni 158keV τ 56 Ni τ 56 Co = 8.8 days = days 6/26/17 9

11 GBM Localization Earth Occultation SN Ia Angular resolution: 0.5 for β = 0 to 1.25 for β = 66 GBM orbit(signal) Congratulations! We localize the SN Ia within degree! Earth GBM orbit(no signal) 6/26/17 10

12 PRELIMINARY GBM Light Curve 847keV bin BGO detector Day 24 Count rate Adapt a LIGO-inspired algorithm (George & Huerta 2016): search for and extract a SN signal from the data Time 6/26/17 11

13 Swift localization Swift can slew to the event within minutes, Other telescopes like HST need ~1 day to slew Swift is critical for this first day! BAT: localizes to within arcminutes XRT & UVOT: further localization to arcseconds if seen 6/26/17 12 Credit: Swift website

14 Future MeV telescopes AMEGO: All-sky Medium Energy Gamma-ray Observatory Detectable SNIa rate: ~1 event per year à100 times higher than Galactic SNIa rate (~1.4 events century) PARAMETER Energy range CAPABILITY ~200 kev to >10 GeV Line sensitivity <6*10-6 ph/cm 2 /s for the 1.8 MeV 26 Al line in a 1-year scanning observation Field of view 2.5 steradian 6/26/17 13

15 Summary and Future work A Galactic SN Ia may go unnoticed but will be a large gamma-ray signal in Fermi/GBM & Swift/BAT. Fermi/GBM is an ideal alarm. Localize the confirmed SN with GBM first, Swift followup. Current/Future work: ØModels with a range of ejecta structures and the Monte Carlo code which calculate the continuum emission to simulate a range of the SNIa signals; Ø pipeline codes for Fermi & Swift SNIa detections. Funded in part by NASA Swift 6/26/17 14

16 Backup slides 6/26/17 15

17 Distance and Apparent Magnitude of A Future Galactic Supernova Adams et. al back Adams et. al /26/17 16

18 Zeroth-order Model: Ejecta+shell Assumptions: ü Uniform ejecta (Bussard et al. 1989) ü Homologous expansion: ü Focus on line emission, ignore the Compton continumm ü Thompson scattering: ü 56 Ni in both shell and ejecta (after Diehl et al s belt model): M Ni,total = 0.5M, M Ni, shell = fm Ni, total, f = 10% The total gamma-ray line flux: Φ total = Φ ejecta v r σ σ Thompson = cm 2 ( M ) Ni, ejecta + Φ shell M Ni, shell ( ) Φ Ni (E 0 ) = dn γ dtda = b E 0 M Ni, e t/τ Ni e τ 4π D 2 56m 6/26/17 p τ Ni 17

19 Zeroth-order Model Assume uniform ejecta, 56 Ni in core+shell The optical depth in ejecta is: τ ejecta = n e σ dl 3M ej σ Thomson 4πµ e m p v 2 0 t 2 ( day / t) 2 mean lifetime: τ = 8.8 days,τ 56 = days Ni 56 Co Three phases of line emission: a. t < τ week, 56 optically thick: only surface 56 Ni lines emerge Ni b. τ < t < τ t(τ 56 optically thick: lines from surface Ni 56 Co ejecta = 1), 56 Co + outermost interior 56 Co c. t > τ, optically thin: entire Co lines emerge Co 6/26/17 18

20 PRELIMINARY Light Curves Ni & Co lines signal in GBM BGO detector line Flux τ 56 Ni τ 56 Co = 8.8 days = days Time 6/26/17 19

21 PRELIMINARY Light Curves Ni & Co lines signal in GBM BGO detector line Flux τ 56 Ni τ 56 Co = 8.8 days = days Time 6/26/17 20

22 PRELIMINARY Shells model line Flux Time 6/26/17 21

23 Order-of-magnitude estimation of SNIA detection rate for AMEGO 1. AMEGO sensitivity around 847 kev line: F_3sig = 3e-6 ph cm^-2 s^-1 2. SNIA flux for the 847 kev line at day ~ 100 days in M82 (3.5 Mpc): (SN2014J: Churazov et al. 2015) ~ F_847keV = 1.e-4 ph cm^-2 s^-1 3. Detectable distance of 847 kev line: ~ D_det = (3.5 Mpc) * sqrt(1e-4/3e-6) = 20.2 Mpc 4. Local SNIA rate: (Horiuchi & Beacom 2010) R_SN ~ 3e-5 Mpc^-3 yr^-1 5. Number of detectable SNIA for AMEGO: N_SNIA_AMEGO = R_SN * (4/3)pi(D_det)^3 = 1.04 yr^-1 6/26/17 22 Courtesy to Brian Fields calculation

24 GBM/BGO orbit 6/26/17 23