Real-Time Chasing of X-ray Transients with SVOM MXT
The article discusses the real-time chasing of X-ray transients using the Micro-channel X-ray Telescope (MXT) on the SVOM satellite. It explains the goals, characteristics, and simulations of the MXT instrument, including its ability to observe Gamma-Ray Bursts (GRBs) and afterglows with high precision localization. The article also covers the MXT Simulator, localization algorithms, and event file analysis for verification purposes.
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Chasing X-ray transients with SVOM / MXT in real time LAURA GOSSET CEA
2 Micro-channel X-ray Telescope Goal = Observe GRBs and afterglows and localize them precisely Characteristics Energy range : 0.2 10 keV Field of view : 57 x 57 arcmin Detector 256 x 256 pixels (75 m) Lobster Eye optics Focalise X-rays thanks to reflections in micropores PSF MXT < PSF ECLAIRs ~ 6 arcmin vs 1 degree Lobster Eye pinciple MXT 0 reflection = diffuse patch / 1 reflection = arms / 2 reflections = central spot Localisation error Calculation on board MXT < 1 arcmin vs ECLAIRs < 10 arcmin MXT = transmit the position to ground based telescopes in real time Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
3 MXT Simulator : MXT instrument Goal = Simulate realistic MXT observations MXT PSF and effective area Modelled by ray-tracing simulations (Leicester goup) New configuration of the optics : 25 MPOs against 21 Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
4 MXT Simulator : GRB IN GRB characteristics Source position Satellite attitude Spectral model Temporal model The simulator is coded in IDL Source spectral model : XSPEC format Parameters IN are at the choice of the user Simulator => simulator configurable OUT BG noise = from Leicester group Photon characteristics Position Energy Arrival time Pattern Origin (source / background) Pile-up Simulator configurable + event file Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
5 MXT Simulator : Event file Pattern, origin and pile up are used for verification aims Pattern distribution (MPE) MPE TRoPIC2 camera : S=27.78%, D=51.63%, T=10.75%, Q=9.84% (Al-K =1.5keV) Swift pattern Photon characteristics given by the MXT simulator Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
6 Localization algorithms Goal = develop localization algorithms onboard SVOM 2D methods = efficient at high fluxes but not at low fluxes 1D methods = efficient at high and low fluxes Use of a larger part of the signal including arms of the psf ICOG / IWCOG and maximum 1D + barycentre are equivalent max1D+bar : less calculation time Maximum 1D + barycentre = good compromise between precision and calculation time R90 = Radius in which 90% of the distances between the true position and the find one are contained Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
7 Simulation of XRT GRB afterglow Goals Simulate samples seen in a large field of wavelength Simulate all the XRT GRBs to obtain statistics values o o Convertion of XRT count rate light curves into MXT observations MXT count rates obtained using effective areas and XPSEC simulations + XRT light curves Counts rates ratio Histogram of count rates ratio between XRT and MXT Peak around 2 and 2.5 Major part of the ratio between 2 and 4 Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
8 MXT results golden sample : GRB 110205A Localisation < 15 arcsec after few hundred seconds Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
9 MXT results golden sample : GRB 081007 Localisation < 50 arcsec after 1000 sec Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
10 MXT results golden sample : GRB 090426 Localisation < 60 arcsec after 10 000 sec Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
11 MXT results : gravitational waves Goal = detect the X-ray counterpart of a GW alert GRB Redshift GRB Redshit 050509B 0.79 100724A 0.9 050813 0.48 101219A 2.6 Hypothesis : short GRBs due to : Coalescence of 2 neutons stars at z=0.1 (Adv. Ligo/Virgo horizon in 2020; Abadie 2010) up to 400 yr-1. 051221A 1.39 130603B 0.12 060502B 0.46 131004A 0.38 061201 0.11 140622A 0.45 061217 0.59 140903A 0.9 070429B 0.35 141212A 0.82 However short GRBs are beamed The expected rate over the entire sky within the Ligo/Virgo horizon can be as low as 0.01 yr-1 (Ghirlanda et al. 2016) 070724A 0.95 150101B 0.11 071227 0.71 150120A 0.28 080905A 0.35 150423A 0.54 090426 0.71 160624A 1.8 090510 1.28 161104A 0.22 Is MXT able to detect and analyze them ? Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
12 MXT preliminary results on gravitational wave alerts: GRB 070724A Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
13 MXT preliminary results on gravitational wave alerts: GRB 070724A 0 hour >104 counts Localisation = 12 arcsec 2 hours 12 hours Few thousands counts Localisation ~ 20 arcsec Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
14 MXT preliminary results on gravitational wave alerts: GRB 061201 After 6 hours still ok, but no signal after 12 hours Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
15 Conclusion Work in progress : GRBs: Complete the multi wavelength sutdy on the GRB golden sample Study and analyze the complete XRT GRB afterglow sample Work on different gravitational wave cases Take into account the SVOM tiling strategy Hyphothesis of formation (NS-BH, WD-NS, WD-BH etc.) Simulation of isotropic X-ray emission from theoretical studies (e.g. Siegel & Cioli 2016) Laura Gosset Chasing X-ray transients with SVOM / MXT in real time 24/04/2017
