2017/3/3

MAXI によるIceCubeアラートへの対応
Searching for Counterparts of Neutrino Events with MAXI

Motoko Serino (RIKEN)
マルチメッセンジャー天文学研究会@千葉大学

on behalf of the MAXI Team

1Introduction• MAXI/GSC observations of IceCube-160731A
ATel #9313; H. Negoro, et al.; on 4 Aug 2016; 01:14 UT• We report on MAXI/GSC observations of the neutrino event IceCube160731A …
At 02:32 UT on 2016 July 31 (about 37 min after the IceCube event
trigger), MAXI/GSC scanned the error region of the event at (R.A.,Dec) = (214.54, -0.33) with a radius of 0.75 deg. No significant excess
emission was detected from the region, and we obtained the 2-20keV 3-sigma upper limit of 0.104 photons/cm2/s (corresponding toapproximately 32 mCrab) for a point source at the above position.
We also investigated transient events around the region from 2016
July 20 to August 3, but no significant events were found. A typical 220 keV 3-sigma upper limit for one day was 0.03 photons/cm2/s (~9mCrab). MAXI continues to observe the region every 92 min.

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Contents• Operation and Observation of MAXI• MAXI Nova-Alert System• Sensitivity and Coverage• Observations of Transients• Searches for Neutrino Event Counterparts• Summary

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MAXI instruments©NASA• MAXI (Monitor of All-sky X-ray Image)• Observation started in August 2009
• Two science instruments• Gas Slit Camera (GSC) 2-20 keV• Solid-state Slit Camera (SSC) 0.7-10 keV

JEM-EF• GSC has larger effective area and covering fraction• Large FoV/Observe whole sky• MAXI can cover entire error region even if the localization is not accurate• Always monitoring• The data before the trigger are available• Alert system is available• Transient events can be found automatically• Real time alert via MAXI mailing lists
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4Field of View and Scan
• Two FoVs (3 x 160 deg)Z

• about 2% of the whole sky• 92 min orbitH

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5Orbit and Operation of GSC
80
70
60

90

Obs. start
10 min2030
Efficiency: 40%

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Obs. stop

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50
40

GSC off

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1 orbit (~92 min)1025 20太陽Sco X-1

1070

Galactic sources60

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55

60

2025

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Crab7

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MAXI
NOVA-ALERTSYSTEM
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MAXI/ISS

Ground System
TDRS
MSFC(US)RIKEN
TKSC/JAXA

Nova-Alert sys.
MAXI Database(store/process)
Alert (high priority)
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Web serverInternet

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Alert (normal)
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Novasearch + Alert System• Novasearch: pick up pixels with flux excesses• generating light curves for each HEALPix pixel(4 energy bands, 8 timescales)• selecting the pixels with increasing flux
• sending ”trigger” information to Alert System• Alert System: select significant events• excluding bright variable sources, solar events,particle events, etc.
• combining the information from Novasearch andjudging "significance"• sending alert/warning mails and running quick look tool

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マルチメッセンジャー天文学研究会@千葉大学

10Automatic/Manual Alerts to ML• MAXI mailing lists :5 categories
X-ray star, new-transient,AGN, nova-cv, supernova• "burst" (highestsignificance) events are
directly sent from AlertSystem• otherwise send manually
after the check by duty
scientist (当番)2017/3/3

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MASIV and “MOXI(目視ぃ)”• MAXI All Sky Image Viewer• Web interface for finding transients by visual inspection from MAXI
all-sky image

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3 degtime

Localization of Transients

65

60

t: time

55

50

-15
-25 -20
45
-30
-35
40
-45 -40
x: position
along the detector anode-wire direction

detector
3 deg
constant source-10

PSF of a constant source

time

70

typical scan transit
40-50 sec+or+
uncertainty+

large systematic error
for short transients2017/3/3

short transient

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SENSITIVITY &COVERAGE
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Exposure and Sensitivity• No significant source was detected→ upper limit• (1) report typical upper limit of Nova-Alert System• (2) calculate from the background counts
timescale

1 scan4 orbit

1 day

4 days

2-4 keV80-120

50-70

25

15

4-10 keV

100

35

15

8

from
Negoro et al. 2016

Typical 3σ upper limit (mCrab) by Nova-Alert System

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Exposure and Coverage• GSC covers
85% of the sky in
95%
100%

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92 min
1 day
3 weeks

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1 orbit (~92 min)Sun
Sco X-1

Galactic sources

Crabtypically 85% of the whole sky
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1 day after the detectionSun
Sco X-1

Galactic sources

Crabtypically 95% of the whole sky
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OBSERVATIONSOF TRANSIENTS
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MAXI GRBs : 70 events in 7 years
observed by other instruments? ーyes:no:

http://maxi.riken.jp/grbs
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MUSST: MAXI Unidentified
Short Soft Transient• only detected in 2-10 keV• no detection in the nextscan• no detection in Swift/XRT
follow-up
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MAXI GRB and MUSST
all GRB+MUSST

8-20keV/2-8keV

r: MAXI+other sat.
g: MAXI only
b: MUSST
counterpart(candidate)○:yes△▽:
no□:no follow-up
hardness is not available
for MAXI J1501-026

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short hard emission in GSC• normal: 1-2 cameras

2017/3/3• hard: all cameras

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2017/3/3

SEARCHES FOR
NEUTRINO EVENTCOUNTERPARTS
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IceCube-160731 & 161210• IceCube-160731(ATel 9313)• IceCube-161210(GCN 20248)• First scan

• First scan

• 37min after the trigger• 12min after the trigger• 2-20 keV 3-sigma upper limit
0.104 photons/cm2/s• 4-10 keV 3-sigma upper limit
20 mCrab• from July 20 to August 3• no significant event• 2-20 keV 3-sigma upper limit
0.03 photons/cm2/s (one day)2deg

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2-20 keV-30 − +5 hour25Summary• MAXI’s strong points• Real time alert• Data before the trigger are available• Upper limit (3σ, 4-10 keV)
• 100 mCrab for 1 scan, 1 5mCrab for 1 day• Observations in 2016
• IceCube-160731: first scan observation started 37 min after the trigger• IceCube-161210: first scan observation started 12 min after the trigger• upper limits are reported to ATel/GCN

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MAXI on-demand data
Click “On-demand” button on
http://maxi.riken.jp/top/or
http://maxi.riken.jp/mxondem/

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