Monitoring High-Energy Transientswith MAXI

Nobuyuki Kawai (Tokyo Tech)on behalf of the MAXI Team

Monitor of All-Sky X-ray Image• Mission started August 2009
• Ops approved until Mar 2018
• Real-time link ~70%

Matsuoka et al. 2009

1. MAXI

Scans withISS rotation

1.5 deg (FWHM)
3.0 deg (at bottom)

Slit + Slats collimator

160 deg

SlitSlatCollimator

3Celestial sphere

Particle background rate

1-dimensional
position
sensitive
detector
proportional counter

X-ray CCD

Operating in equatorial region

Nova-Alert System

Negoro+ 2016,
PASJ

TKSC/JAXA

RIKEN&MAXIMLs(& ATel/GCN)

Nova Alert
System< 10 sec (Real)~ 1.5 h (Stored)Various Timescales to Investigate
50 sectbin = 1 s, 3 s, 10 s, 30 s
40 ~ 200 sec (50 µs resolution, GSC)
1 scanX, g-raybursts
Superburst
SFXT
Star Flares
X-ray novae
AGN Flares

5 days92 m

X-ray burst
From 4U 1916-053

Superburst + Outburst
From EXO 1745-248
Serino+ 2012

4 orbits ~ 6 h
50 days
1 day

4 daysBH Outburst
MAXI J1659-152
Negoro+ 2010,Yamaoka+ 2011

X-ray New “MAXI” Transients/Novae
5(+1) X-ray novae were newly discovered in the last 3yrs.
BHC: J1535
NS: J1957, J1807, J1621
Unknown: J1501(J0636+146, a GRB?)

Brightest Black Hole X-ray
nova in this century,
discovered on 2017 Sep 2

J1501-026
J1659-152

J1807+132

J1647-227

J1535-571

J1735-304
J1619-383

J1932+091

J1421-613
J1409-619

J1957+032
J1910-057(J0636+146)
J1305-704
J0556-332

J1543-564

J1828-249
J1836-194

Negoro+ 2016

J1621-501
GRB 121225A(Sw J1741.5-6548)

J0158-744

Total 21 : 7 black holes, 11 neutron stars, 1 white dwarf and 1(+1) unknown.
6Flux distribution of alerts on different time scales(Negoro+ 2016)MAXI Transients•

1 scanGinga/ASM
1 day

6h1d

XRB SLX 1735-269, IGR J1724-3257– + GRBs•

MAXI J0636+146, MAXI J1957+032– + Hyper Star flares, SFXTs, …

RXTE/ASM 1 day4d•

H 1743-322, 4U 1711-34, GRS 1716+....

•

4U 0728-25z

New class object in halo?
Low-mass Fast X-ray
Transients (LFXT) !?
(AMXP ? Burst Only Src?)

Sun
Edge-on View
J1957+032
4 kpc distance is assumed
for J1619, J1932, J1957

optical/radio
follow-upessential©NASA/JPL-Caltech

Blackhole binary : MAXI J1535-571
MAXI science news 61•

#'(5(&5('$0#3$:017$$5  "!10   (2 $0'0$/(',5# !(.  163+163 %()13(,5 8,)5+$'$.41'(5(&5(',5  ,7(+1634  %()13( 8,)5
#017$4($3&+ 231*3$/+$''(5(&5(',5$651/$5,&$..:•#  ,0&3($4('5+().69$0'
3($&+(' 3$%10 (2 58$45+(%3,*+5(45#3$:017$4,0&(#8$4
.$60&+('58$45+(5+ %3,*+5(45,0+,4513:0)$&5,58$45+(%3,*+5(45#3$:017$
4,0&( 5+$5,4,05+( 45 &(0563:

•8,)56 !+$0'3$+$7(
1%4(37('#$48(..$4125,&$.
$0',0)3$3('5(.(4&12(4•5($/3(2135('$&1/2.(9',4-.,0(,0
5+(42(&536/$0'$8,5+*11'2+1510
45$5,45,&4;!(.  MAXI sky map on 2017 Sep. 19.

!3$04,5,101)
$&&3(5,10',4-MAXI light curve of MAXI J1535-571

8

MAXI J0158-744: unique soft X-ray transient

9MAXI GSC Allsky Image
GalacticCoordinate• 2011-11-11 05:05:59 (UT)• GRB 111111A• Soft X-ray transient ( < 5 keV)

• Swift follow-up lead toidentification to a star near SMC(Be star at 60 kpc)

Morii et al. 2013

10MAXI J0158-744
X-ray light curve• Duration ≈ hour

X-ray Flux

– (1300 s <ΔT< 1.1 x 104 s)

MAXI MAXI SSCGSC• Extremely luminous– 1040 erg / s– x100 solar mass Eddington
luminosity

Swift XRT
days

Morii et al. 2013

0.1110• supersoft X-ray source atlate phaseà white dwarf– classical/recurrent nova?
• but x104 more luminous than
known nova X-ray emission– (shocked ISM? Li et al. 2012)10

Nova (nuclear fusion) explosion
rare

Morii et al. (2013)

WD-Be binary system (MAXI J0158-744)
Be starCircumstellar
disk

Very massive
O-Ne white dwarf

Nova ignited
with a lessaccumulation

Luminous (100LE) andExploded out quickly
Thermal Ne line
11

Credit: Takuya Ohkawa

MAXI GRBs and transients (2—20 keV)

: only MAXI (43): MAXI + other (39 prompt + 7 afterglows)

Serino et al. (2014)
http://maxi.riken.jp/grbs/
12Flux and Hardness !  !

MAXI+other ○Only MAXI ▲

1/2 of MAXI GRBs are"Only MAXI" events
Only MAXI GRBs
tend to Soft and Dim
many of them
are XRFs?



! 
Slide by M. Serino13

MAXI Unidentified Short Soft Transient (MUSST)• Detected only in X-ray band (MAXI 2-10 keV) : Soft– No detection by Swift/BAT (15-50 keV)

• Fades out before Swift/XRT follow-up at a half day later : Shorttransient• No detection by Swift/XRT ends up unidentified– MAXI localization (0.3deg) is insufficient for optical follow-ups.

• Rapid X-ray follow-up is desired while it is still bright(100 mCrab in 1 minutes, 1 mCrab in 20 minutes).

⇒ NICER

8 MUSSTs in 8 years of MAXI
flux
name
llbb [Crab][Crab]ref.erence
reference
name
GRB
161123A
255.8 +14.7-69.6 0.1
0.1 AtelAtel#8050
MAXIJ1714-130 9.6,
#8050
MAXI354.6 +46.8+46.8 0.44
0.44 AtelAtel#7954
MAXIJ1501-026
J1501-026 354.6,#7954
GRB150428C
139.3 +30.6+11.2 0.1
0.2 GCNGCN#17772MAXI
J1540-158 351.6,#17568
MAXI
351.6 -12.6+30.60.2
0.1 ATel GCN#17568MAXIJ1540-158
J0545+043 201.1,#6066
GRB140814A
140930A
106.2,#16855
GRB
139.9 -6.8+66.4 11 GCNGCN#16686
GRB 140814A#16686
MAXI
J0545+043 139.9,
201.1 +66.4-12.6 10.2 GCNATel#6066
GRB130407A
26.4,+35.64GCN#14359GRB 130407A
26.4 +35.6 4
GCN #14359
MAXIJ1631-639
324.4-10.8
0.12
ATel#3316
MAXI J1631-639 324.4 -10.8 0.12
ATel
#3316

A MUSST,
GRB
140814A.
Reported
asaGRB,butnodetection
by
Swift follow-up.
X-ray image at
discovery andlight curve in the scan. Soft (= no detection in10-20keV) is a different point from a GRB.

14

What are these short soft transients?
•••••

gamma-ray bursts with very low Epeak
stellar flares
igniting classical novae
tidal disruption events
low-luminosity GRB w/SN(~ SN2006aj/GRB060218)• SN shock breakout (~ SN2008D)• very short AGN (blazar) flare• soft extended emission of short GRBs
– neutron star merger — GW source (?)

• …

15

MAXI for GW event(a) before merger(b) ≈2 seconds
Neutron star binary
GW(c) ≈100 seconds

off-axis GRB?
cocoonemission?

(d) 1–10 days

black hole
shock in ejecta?
radio-activity?

accretion disk
relativistic jet

viewing
direction
afterglow visible
at a large angle

ejectashort GRB
(X/gamma-ray)

GRB afterglow, beamed(X/gamma-ray, optical)

kilonova: radioactive
decay of ejecta(UVàopticalàNIR)MAXI will measure
X-ray emission at theearly post-merger
phase of neutron starmerger events

MAXI observation
Emission from Double Neutron Star Merger in time sequence andpossible X-ray emission processes

16Framework of GW Analysis• Nova-Alert system is always running regardlessof GW event or not
GW150914

GW151226• Search weak candidate and calculate X-ray flux upper limits

from MAXI/GSC observation in the error region of GW event
when we receive the GW skymap data from GraceDB
17

“X-ray upper limits of GW150914 with MAXI”
PASJ in press (Kawai et al.)Nova-search◇ 1-orbit trigger event 4-orbits triggercWB_skymap• Triggered at 2015/09/14 09:50:45 UTC• Scan in the GW error region started T0+4 to +25 min• Scan in one-orbit covered 95% of cWB skymap region by 6 GSC cameras• Nova-Alert detected no significant variability with 3 σ in the GW error

region.

18

“X-ray upper limits of GW151226 with MAXI”

PASJ in press (Serino et al.)• Triggered at 2015-12-26 03:38:53.648 UTC• At the trigger time, GSC was observed in the GW error region: cover 1% of theregion at that time
• Scan in one-orbit covered 84.8% of bayestar skymap region by 6 GSC cameras• Nova-Alert detected a short excess event with a low significance (2.85σ) fromT0+5257 to 5260 sec

Nova-search◇ 1-orbit trigger event□ 4-orbits trigger

one day scanbayestar_skymap
short excess

19

“X-ray upper limits of GW151226 with MAXI”

PASJ in press (Serino et al.)Short excess in the GW error region
GSC Light curve in 4-10 keV• (R.A., Dec): (19.913, −14.480 deg) with error of elliptical circle
0.46°,0.49° (+systematic 0.1°)• X-ray flux: 5.1+2.1−1.8 ×10−2 counts cm−2s−1 ~43 ±16 mCrab

20

GW 170817
••
•
•
•

Sugita+ 201712:23 (-18 min pre GW) MAXI scanned the field with no detection
12:41 GW170817 (MAXI in high particle flux region)
12:44 MAXI resumed observation
17:21 (+4.6 hours post GW) first observation (partial)
18:55~ full coverage; no detection

21

MAXI for GW counterpart search•

MAXI has sensitivity to detect the “extended” X-ray emission and early
afterglow of SGRBs, if observation takes place within an orbit (~85% of thewhole sky)Afterglow of SGRBs scaled toGW170817 distance (40 Mpc)
GRB050709 Villasenor et al. 2005

MAXI X-ray upper limits
for GW170817

Short
hardpulse

MAXI typical one-orbit
sensitivity

HETE-2
2–25 keV

Chandra“Soft extended emission”

22

MAXI/GSC observations ofIceCube-170922A and TXS 0506+056

ATel #10838; H. Negoro

We reexamine MAXI/GSC data for the high-energy neutrino event IceCube-170922A
detected at 20:54:30.43 on 2017 September 22 (GCN #21916), and recently active blazer
TXS 0506+056 in the IceCube error region (ATel #10791, #10792, #10794, #10799, #10801,#10817, #10830, #10831, #10833, also see ATel #10773, 17787).
MAXI/GSC scanned the IceCube error region at 20:49 and 22:21 on September 22
before and after the event, and detected no significant X-ray enhancement. The 4-10
keV 1-sigma upper limits are both 16 mCrab.
We also produced 2-4 keV and 4-10 keV X-ray light curves at the position of TXS 0506+056
with the PSF-fit method (Morii et al. 2016, PASJ, 68, S11). The 4-10 keV X-ray light curveshows a flare-like event peaking at 0.040 (+0.022, -0.019) c/s/cm2 (~34 mCrab) in the scantransit at 16:53 on September 23, and the 4-10 keV X-ray flux averaged over 4 scans from12:15 to 16:53 on September 23 is 0.021(+0.009, -0.008) c/s/cm2 (~ 18 mCrab, 2.6 sigma
level detection). The 2-4 keV X-ray light curve, however, do not show similar excess for theabove period. and the point-source is not so visible even in the 4-10 keV X-ray image.
Any flux excess corresponding to the Gamma-ray flare after September 15 (ATel #10791) isnot recognized either in the 2-4 keV or 4-10 keV X-ray longterm light curve.

MAXI/GSC observations ofIceCube-170922A and TXS 0506+056

ATel #10838; H. Negoro

IceCubeLong-term monitoring of AGN: Mrk 421

MAXI Light curve (3-10 keV) of theBlazar Mrk 421 for 3 years.

Power spectrum of Mrk 421 by MAXI.
It connects with the ASCA points at higher frequency after break.
White triangles with lines are simulation of a power law with index of 1.6.
Black triangle with lines are extrapolation of ASCA curve (index 2.14).
Isobe et al. (2014)

PSR B1259–63

https://www.nasa.gov/mission_pages/GLAST/news/odd-couple.html

R1

GR2
1

3
2

R3

4

3
*2
14

Hirayama et al. 1996

PSR B1259-63 X-ray flux vs. orbital phase

PSR B1259–63
gamma-ray and X-ray emission near periastronDays from PeriastronM. Chernyakova et al. (2014) (2017)

PSR B1259-63
X-ray light curve

MAXI flare source
positions

Flare ID

orbital phase

Flux (1-20 keV)

L1−20keV

φ×10−10 erg cm−2 s−1×1035 [erg cm−2 s−1 ]Flare 20.085

2.81+0.51−0.60

1.77+0.32−0.37

Flare 30.641

Flare 4

0.962

7.41+0.50−2.31

4.67+0.32−1.46

Flare 50.148

4.76+0.50−0.71
3.83+0.21−0.73 (2017)

3.00+0.32−0.45
2.42+0.13−0.46

x10 ASCA flux

PSR 1259-63 flare• Accretion unlikely due to propeller effect• pulsar-stellar wind collision may be responsible• required clump density/mass comparable to thosefound in Vela X-1 and Supergiant fast X-ray
transients (SFXTs)

Animation of Supergiant Fast X-Ray
Transient, IGR J18410-0535 (c) ESA

PSR 1259-63 – Chandra observations
12/17/2011

05/19/2013

02/08,09/2014

extended source moving at 0.07c

Pavlov et al, 2015

http://chandra.harvard.edu/photo/2015/psrb1259/

Data distribution••••

MAXI data are public at MAXI Web.
403 sources are processed.
101 sources of them areprocessed every 4 hours.
Ondemand process allows users toextract MAXI data from any sky
region in any time period.
Some contribution pages available. MAXI HP http://maxi.riken.jp/

Light curve of sources

Image and spectrum
by ondemand

BeXRB monitor @ ESA
Power spectrum

MAXI 1535 monitor

BAT-MAXI transient monitor

Weekly light curves

MAXI-BAT Hardness ratio

MAXI GRB list33

publication statistics• Number of refereed papers from previous evaluation (2014.11.25) to date (2017.10.31).
(a) By MAXI team member, using MAXI data(b) By other than MAXI team member, using MAXI data(c) By observations triggered by MAXI alerts, NOT using MAXI data

this extended period•

Before previous evaluation
2009.8(2009.12)2014.11
5 yr( /yr )
(a)41
( 8.2 )(b)68
(13.6 )(c)106
(21.2 )

this extended period
2014.122017.11
3 yr( /yr )
25
( 8.3 )
76
(25.3 )
126
(42.0 )

Orange isRefereed
as of2017.10.23.

In this extended period, there are 105 papers inProceedings of MAXI 7 yr conference (2016.12). They are non-refereed, and not counted in the figure.
••••MAXI Instrument paper (Matsuoka et al. 2009) was awarded as PASJ excellent paper in 2014 March.
The number of citation was about 100 in 4 years It keeps increasing to reach 210 now.
The rate in this period is the same as before in (a) . Number of the MAXI team is almost the same.
The rate is doubled in (b). MAXI data are more widely used by more scientists.
The rate is also doubled in (c). Number of observations (=observers) triggered by MAXI Atel or GCN has
increased.
34

OHMAN (On-orbit Hookup of MAXI And NICER)NICER : Mounted in June 2017

Look at the source in X-ray,while it is still bright in X-ray.
Rapid follow-up from 2 min. after discovery
MAXI nova detection by onboard PC
Convey information to NICER on ISS.

Survey discovery space intime-domain astronomy.
Rapid decaying objects.
MUSST
GW sources
Orphan afterglow of GRB
Stellar flares
35

Future: Time-domain astronomyof Rapidly decaying objects
Rapidness of follow-up in X-ray and sensitivity
Flux

MAXI

10NICERon-orbit

CrabTDE

1XRFmCrab

10mN

XRB
oGRB

SNboSFXTsGRB

10.01SwiftSB

100

0.1

NICERground

1second

1SF

1minute

101001hour

103104

Swift follow up isvery effective.
Rapidly decreasing obj.
TDE: as Sw1644
mN: massive Nova
SB: super burst
XRB: X-ray burst
XRF: X-ray flash
sGRB: short GRBoGRB: orphan GRB
SF: stellar flare
SFXT: super giant
fast X-ray transient
SNbo: super nova
shock break out

1dayTime (s)105 after appearance

36