All Sky Monitors ‐̶̵̵̵̵ - ‐̶̵̵̵̵ - - RXTE / MAXI / Einstein Probe(EP)

Restless universe Rui Huang

Thanks Prof. Feng & Prof. Cui outline

• Why ASM?

• ASM/RXTE • MAXI • Einstein Probe

• Summary Why we need all sky monitor ?

The sky is rich in transients of many types Transients! USA ASM/RXTE 1995/12/30-2012/01/03 All Sky Monitor/Rossi X-Ray Timing Explorer

Xenon gas

anodes

3 Scanning Shadow Camera • Coded Mask • FOV : 6° x 90° • Xenon proportional counter (charge-division technique) • 2-10 keV • 90 cm2 • 30 mCrab ALAN M. LEVINE, et al. APJ.1996 ASM/RXTE 1995/12/30-2012/01/03 All Sky Monitor/Rossi X-Ray Timing Explorer

orbit: ~500km ~90 min exposed for 90s in one direction

ALAN M. LEVINE,et al. APJ.1996 Japan Monitor of All-Sky X-ray Image

MAXI 2009/07/16-Present onboard ISS (International Space Station)

Gas Slit Camera

• Xe + CO2(1%) • 2-30 keV • 5350 cm2 • 1.5° x 160° • 18% @5.9keV

Gas Slit camera Solid-state Slit Camera • CCD • 0.5-12 keV • 200 cm2 • 1.5 x 90 Masaru MATSUOKA,et al. 2009 ° ° • 3% @5.9keV Hamamatsu Photonics CCD • Objects located along a great circle stay for 45 s in the FOV of the MAXI cameras, where the time of stay is the shortest in the MAXI normal direction (for a great circle). China Einstein Probe (EP) May be launched in 2022 WXT: Wide Field X-ray Telescope FXT: follow up X-ray telescope

I'm going into space!

micro-pore Reflect rather than refracting

• WXT (Wide Field X-ray Telescope) First image from the prototype of micro-pore (MPO) lobster-eye optics • lobster-eye

• 60° X 60° FOV • FXT (follow up X-ray telescope) • 5’ • Wolter I • CMOS • 1° X 1° FOV (Complementary Metal • < 2’’ Oxide Semiconductor) • CCD • 0.5-4 keV • 0.3-8 keV • 170 eV @1keV • 170 eV @1keV • 0.1 mCrab • 0.3 mCrab possible design Weimin Yuan, et al. 2018 strategy of observation

• 97 min per orbits • 20 min one direction. • Only the night sky in the opposite direction of the sun is monitored. • Only half sky is monitored in one day. Sensitivity Sensitivity represent the dimmest sources that the telescope can observe. 휎 BAt 휎 B 푅 = = 휂퐴푡 휂 At XTE/ASM Fov: 30 mCrab 3 X 6° X 90° 2-10 keV

MAXI 2 X (1.5° X 160° + 1.5° X 90°) 1 mCrab 0.5-30 keV 0.3 mCrab 60° X 60° 0.5 - 4keV Einstein Probe

from Neil Gehrels’s report in ISSI In the photon energy range from 2 to 10 keV, Beijing Dynamic Universe Forum 2014 1 Crab equals 2.4 · 10−8 erg cm−2 s−1 = 15 keV cm−2 s−1 = 2.4 · 10−11 W m−2 Summary

• All Sky Monitor is necessary!

• ASM/RXTE -past • shadow camera • 30 mCrab 1620 square degree • MAXI -present • slit camera • 1 mCrab 750 square degree • WXT/EP -future • lobster eye better sensitivity and larger FOV • 0.3 mCrab 3600 square degree

• Time domain astronomy Summary Cost resolution Time resolution Energy energy range sensitivity resolution Spatial Fov resolution) (detector detector area detector optical system Time orbit observation Strategy of ？ satellite minutes 90 , about 500Km minutes of 80% the sky every 90 fix at one direction for 90s. million 350 dollar time bins also available inteegration90s time,1/8 s 2 Time? condition? how long mCrab 20 in what arcmin x 15 3 square 90 cm technique) counter (charge Xenon proportional Coded Mask there shadow cameras segments?3 detectors (about years) 16 1995/12/30 ASM/RXTE 6 x 90 square square 90 6 x degrees - 10keV - 2012/01/03 2012/01/03 - division 9 years 9 ) 2009/7/16 MAXI(GSC) GSC: 160kg 520 kg GSC: kg in 520 160kg total International Space Station about minutes 92 with ISS • • 0.1ms ; 18%(5.9keV); 2 2m Crab limit for day 1 degree 0.1 square degrees x160 1.5 mm 1 5350 sensitive detector) ; (1 + CO21%) two proportional counter(Xe Slat Collimator Gas Slit Camera - 30 KeV KeV 30 all sky ensure the courage of procession rotate - present (almost with ISS - D position of the orbit - - MAXI(SSC) - - - - s 5.8 3%? <=150eV(5.9keV) 0.5 degree 0.1 degrees square x90 1.5 mm 0.025 200cm2 dimension sum up to one CCDs Slat Collimator Camera Solid - 12 keV 12 - state Slit maybe launch 3y ,goal 2022.plan year 5 EP(WXT) wide field x WXT:17kg WXT:17kg 12 X Satellite about 97min • • • eV 170 1keV @ 0.5 one level? 5 60 X (effective ~3 cm2 area@ 1keV cm2 1728 CMOS per module 2X2 cm) cm 6 X K,6 4 CMOS(4 K X lobster ( degrees and module)per 12 1 arcmin billion RMB module(6X6 MPO,300 square 5h 5h for times3 orbits cover half of sky half sky monitored one day. direction of the sun is monitored. Only the night sky in the opposite 20 - 4keV min Micro focal one direction. , - pore Optics plane - ray telescope ) ) so only 100kg eV 170 1keV @ 0.3 <2' 1 ?X 1 38' @1keV) (effective area cm2 >=120 pn focal length) Wolter I (1.6 m 1 telescope follow up EP(FXT) - CCD maybe - 8 keV