Search for X-ray Transientswith MAXI

Nobuyuki Kawai (Tokyo Tech)M. Serino (RIKEN), H. Negoro (Nihon U.)

on behalf of the MAXI Team

• MAXIInstrumentation andoperation• Observations forGW150914andresults incontext• Observations forGW151226

Monitor of All-Sky X-ray Image

Matsuoka et al. 2009

Mission started August 2009Ops approved until ~ March 2018

Instruments and Observation6 x 2 GSC (Gas Slit Camera)

2-20 keV, Time Resolution 50 µsMihara+ 2011, Sugizaki+ 2011

2 x SSC (Solid-state Slit Camera) 0.7-7 keV, Time Resolution 5.865 s

Tsunemi+ 2010, Tomida+ 2011

SSC

(slit)collimator

ProportionalCounter

slit

NovaAlertSystem

<10sec(Real)~1.5h(Stored)

TKSC/JAXA

RIKEN&

MAXIMLs

(& ATel/GCN)

Nova-Alert System Negoro+2016,PASJ

MAXI Transients : 17 sources in 6 years

J1659-152 (GRB100925A)

J1543-564J1836-194

J1305-704

J1910-057(SwiftJ1910.2-0546)

J1828-249

J1647-227

J0556-332J1409-619

MAXIJ0158-744GRB121225A(SwiftJ1741.5-6548)

J1932+091

1WhiteDwarf, 6NeutronStars,6BlackHoleCandidates, and1unknown

J1735-304(SwiftJ1734-3027?)J1421-613

2.5Blackholes

MAXIJ1659-152(GRB100925A)

MAXI1543-564MAXI1836-194

MAXI1305-704MAXIJ1828-249

6 Black holes discovered by MAXI

MAXIJ1910-057(SwiftJ1910.2-0546)

55500 56000565002009.82014.4

(out of 12 BHCs discovered since Aug 2009)

Negoro etal.(2014)

500days

2.5Blackholes

Negoro 2008

J1543(l,b)=(325.1,-1.1)d >12kpc ?(Stiele+ 2012)

J1305(l,b)=(304.2,-7.6)

8.5 kpc

MAXI watches through the whole Galaxy.12 kpc

F=aLEdd/4pd2

a =0.01-0.04(Maccarone 2003)Soft-to-HardTransition

J1828(l,b)=(8.1,-6.5)d >12kpc !?

2.5Blackholes

MAXI J0158-744: unique soft X-ray transient

• 2011-11-11 05:05:59 (UT)• GRB 111111A• Soft X-ray transient ( < 5 keV)

MAXI GSC All-sky Image

Galactic Coordinate

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

8

Morii etal.2013

1 10days

X-ra

y F

lux

0.1

X-ray light curve

MAXI SSC

Swift XRT

MAXIGSC

MAXI J0158-744• Duration≈hour

– (1300s<ΔT<1.1x104 s)

• Extremelyluminous– 1040 erg/s– x100solarmassEddingtonluminosity

• supersoft X-raysourceatlatephaseàwhitedwarf– classical/recurrentnova?

• butx104 moreluminous thanknownnovaX-rayemission

– (shockedISM?Lietal.2012)9

Morii et al. 2013

9

10

WD-Be binary system (MAXI J0158-744)

Credit: Takuya Ohkawa

Very massiveO-Ne white dwarf

Be star

Circumstellardisk

PressRelease fromRIKEN(2013.11.14)

Nova ignited with a less accumulation

Luminous (100LE) andExploded out quickly

rare

Thermal Ne line

Morii etal.(2013)Nova(nuclearfusion)explosion

TidalDisruptionEvents- Astarapproaching toagiantblackholeinthe

centerofagalaxyistornintopiecesbythetidalforce.Thedebrisaccretes totheblackhole.

- LongtimemonitoringofMAXIguaranteesasingleevent,notoneoftheAGNactivities.

- MAXI detected threeTDEduring2009-2012.

MJD(DAY)55650 55750 55850

Flux(m

Crab)

0

2

6

4

8

nT=-1.92 (-0.73/+0.58)

MAXI2-10keV

SwiftJ1644+57withSwift/BATandMAXI/GSC SwiftJ2058+05withMAXI/GSC

2011/3/28

2011/5/20

Burrowsetal.Nature2011

GRB Reports to GCN

Swift-BAT Fermi INTEGRALCALET +

othersMAXI MAXI/All

2011 71 8 3 6 3 3.3%

2012 84 17 5 3 11 9.2%

2013 79 28 6 0 4 3.4%

2014 88 32 3 4 8 5.9%

2015 86 28 4 4 18 12.9%

2016 19 5 1 3 5 15.2%note: these numbers are not complete.

MAXI Trigger:XRT follow-up ToO: 160101A (+13.2 ks, afterglow detection)160206A(+46.2 ks, 2 candidates)151205C (+11.1 ks, No), 160102A (+10.8 ks, No)

No ToO: 151216A, 160104B, 160107A (Fermi, CALET)

Swift/BAT (faster) Trigger:detection: 151112A (BAT +36 s), 160227A (BAT +185 s)no detection: 151027A

Alert issued 12 sec

2-4 keV

4-10 keV

10-20 keV

GRB 160102A

MAXI GRBs and transients (2—20 keV)

13

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

http://maxi.riken.jp/grbs/Serinoetal.(2014)

GRB localization with MAXI

14

MAXI Short Transient with no XRT counterparts

15

GCN#17772 Atel #7954GCN#17568GCN#16686ATel #6066GCN#14359 ATel #3316

GRB150428CMAXIJ1501-026MAXIJ1540-158 GRB140814A MAXIJ0545+043GRB130407A MAXIJ1631-639

MAXIlightcurvesnotcorrectedforcollimatortransmission

Nofluxinhighenergyband

2015-04-282015-08-262015-03-11 2014-08-142014-04-12 2013-04-072011-04-29

(l,b)=(139.1,+11.3) (354.6,+46.8)(351.6,+30.6) (139.9,+66.4)(201.1,-12.6) (26.4,+35.6)(324.4-10.8)

flux0.16Crab0.44Crab0.1Crab0.23Crab 0.2Crab 0.17Crab0.12Crab

2-4 keV

4-10 keV

10-20 keV

11’FOV

0 1 2 5 10 21 42 85 171 341 680

GW150914 (T0+4~92 min)

(Serino etal.GCN19013)

Sun

2-20 keV 3-s upper limit: 0.1 counts s–1 cm-2 ≈ 30 mCrab≈ 1 × 10–9 erg s–1 cm-2

0 11 31 74 157 326 659 1323 2663 5312 1058

GW150914 (T0+0~1 day)

2-20 keV 3-s upper limit: 8 mCrab ≈ 3 × 10–10 erg s–1 cm-2

MAXI on GW150914

1scan(≤92min)

1day

5min ~

Wherethereisnowill,theremightbeawaytoaGWstar!?

MAXI observations for GW150914 Timescale

(s)Flux

(erg s–1 cm-2)Luminosity*

(erg s–1)Radiated

Energy (erg) EX/EGW

1 orbit 1000 < 9.5 × 10–10 < 1.9 × 1046 < 1.9 × 1049 < 3.5 × 10–6

1 day 8.6 × 104 < 2.3 × 10–10 < 4.6 × 1045 < 4.0 × 1050 < 7.4 × 10–5

10 days 8.6 × 105 < 0.8 × 10–10 < 1.6 × 1045 < 1.4 × 1051 < 2.6 × 10–4

* Distance 410 Mpc assumed

• Eddington luminosity for 62 M☉ BH ≈1040 erg s–1

• Radiated energy in GW: EGW = DMc2 ≈ 5.4 × 1054 erg

MAXI on GW150914

10-2 10-1 100 101 102 103 104 105 10610-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Time since Trigger (sec)

Flux

(erg

/s/c

m^2

)

MAXI on GW150914

▲

10-2 10-1 100 101 102 103 104 105 10610-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Time since Trigger (sec)

Flux

(erg

/s/c

m^2

)

Fermi GBM possible detection(extrapolated to 2–20 keV flux

averaged over 1 second assuming photon index –1.4)

MAXI could have marginally detected GBM SGRB if it was in the field of view

Short GRB 050709The only short GRB observed in soft X-ray

Chandra

HST Fox et al. 2005

z=0.160Dwarf irregular galaxySFR = 0.2 Msun/yr

HETE-2

Short hard pulse

“Soft extended emission”

Villasenor et al. 2005

2–25 keV

HETE-2

●

●

▲

10-2 10-1 100 101 102 103 104 105 10610-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Time since Trigger (sec)

Flux

(erg

/s/c

m^2

)

MAXI sensitivity for

SGRB in GW range

GRB 050709Short pulse

MAXI could easily detect “short pulse” and “soft extended emission” of GRB 050709

GRB 050709Extended emission

GRB 050709Afterglow (Chandra)

▲

●

●

10-2 10-1 100 101 102 103 104 105 10610-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Time since Trigger (sec)

Flux

(erg

/s/c

m^2

)

MAXI sensitivity for

SGRB in GW range

GRB 050709 scaled to 100 Mpc

“Soft extended emission” or X-ray afterglow of a short GRB at O2 BNS range may be detected by MAXI in the following scan

Summary• MAXI scans about 60-80% of the sky in one orbit (92 min), and more than 90%

in a day.• We can provide a fast (<30 sec) alert for bright bursts.• MAXI is detecting ~10 short transients per year. About half of them are

confirmed as GRBs simultaneously detected by other satellites. There can be other class(es) of objects yet to be identified.

• MAXI discovered 17 new sources in 7 years including 6 black hole binaries and a white dwarf/Be system. The latter exhibited a ultra-luminous explosion at ignition of a nova.

• A large fraction of GW150914 region was covered in 1000s, yielding a flux upper limit ~10–10 erg s–1 cm–2.

• MAXI can constrain the short GRB scenarios for DNS merger at <100 Mpc (O2 range)

• Instantaneous field of view of MAXI is 2% of the sky. iWF-MAXI (FoV >10% sky) has been proposed.