Bright Black Hole X-ray Binaries
recently discovered by MAXI— MAXI J1535–571 and MAXI J1820+070 —Nobuyuki Kawai (Tokyo Tech)
Collaborators:
Katsuhiro Murata, Yuichiro Tachibana, Kotaro Morita, Ryosuke Itoh (Tokyo Tech),
Hitoshi Negoro (Nihon Univ.), Satoshi Nakahira (RIKEN), Megumi Shidatsu (EhimeUniv.) and The MAXI Team
Kumiko Morihana (Nagoya U.), Takahiro Nagayama (Kagoshima U)

High-energy gamma-rays from
NS/BH binaries• NS (pulsar) + OB star

• PSR B1259+63: pulsar wind + stellar wind è shock• NS (ms pulsar) + low-mass star• “Black widow”• BH + OB/WR star

• Cyg X-1, Cyg X-3• Gamma-ray emission related with “X-ray states”

Observational study of black holes
is even more interesting now• GW observation of ≈30 M☉ black holes• Mass range and population? Origin?

• Better sky/time domain coverage for transients• (near) all-sky X-ray monitoring by MAXI, Swift, …
• All-sky optical monitoring• e.g. All-Sky Automated Survey for Supernovae (ASAS-SN)• Timely multiwavelength follow-up observations• More radio-IR-optical facilities available for monitoringor follow-up• All-sky gamma-ray monitoring – Swift, HAWC, etc.
• CTA coming online for sensitive follow-up

Black Hole Binary (high mass)Black Hole
>3–20 Msun

Stellar wind
• Only a few known in the Galaxy• Cyg X-1, Cyg X-3, SS433(RLO, NS?)

High-mass star
10–20 Msun

Black Hole Binary (low mass)Black Hole>3–20 Msun

Low-mass star
0.1–1 Msun

Roche Lobeoverflow• mostly transient (“X-ray nova”)• ~1/year new BHB discovered

“X-ray Nova”
light curves
10 CrabX-ray flux (Crab unit)

MAXI J1535-571
1 CrabMAXI J1910-057

100 mCrab'"&+,-./**'/012

XTE J1752-223

10 mCrab
MAXI J1543-564'"'&!"!#$%&'(00!"!)%&'(!"!)*%&'(!"!)(%&'(!"!)#%&'(3451/6+789!"!)$%&'(

1001001 mCrab!"!$%&'(200200

Time (days after onset of outburst)

Microquasar modelAnatomy of an accreting black hole
Advection dominated flow + corona
Inverse Compton radiation(seed photon: disk/cyclotron)
optically thick disk
Blackbody radiation
kTin≈ 0.1–1 keV

3 rg= 6GM/c2
innermost stable circular orbit
jet

Synchrotron/SSC

Spectral States and Disk-Jet Couplingin Black Hole Binaries (Fender 2004,…)

X-ray spectrum of a black hole binary

Log n*FnTotal disk emission

Comptonized emission
from disk corona orSynchrotron/SSC
from jetBlackbody from each ring
Log n10

Monitor of All-Sky X-ray Image••••

Mission started August 2009
Ops approved until Mar 2021
Real-time link ~70%
“MAXI 10-Year” Symposiumplanned in Fall 2019

1.5 deg (FWHM)
3.0 deg (at bottom)

160 degMatsuoka et al. 2009

Celestial sphereOptical/NIR emission from Lowmass X-ray binaries• Thermal emission from the Xray irradiated disk and/or thecompanion• Synchrotron emission fromthe jet• Cyclotron emission (orComptonized —) from ADAF
Near-infrared

may constrain the system geometry and dynamics, andprovide information on accretion and radiation processes

MAXI J1535–571⇦ X-ray light curves
Hardness-Intensity
Diagram (HID) ⇩15–50 keV

2–8 keV

Nakahira et al. 2018

Follow-up observation
with IRSF 1.4 m telescope
Near-infrared• J (1.2μm), H (1.6μm), Ks (2.3μm)• less dust extinction than optical and UV• galactic plane source such as MAXI J1535-571
Sutherland observatory in South Africa• Southern Hemisphere• MAXI J1535-571
Observations• Sep 6—17: Kumiko Morihana, Takahiro Nagayama• Sep 28 — Oct 2: Katsuhiro Murata, Ryosuke ItohFn (H) [mJy]

MAXI J1535–571: 2-color fux (H vs. J)

Fn (J) [mJy]MAXI J1535–571: NIR flux properties• Variable on three time scales• Slow gradual rise (τ ≥ 10 ks)• Intermediate variation (τ ~3 ks) at plateau• Rapid variation (τ<20s)• Rapid var. amplitudes scales with total flux
• Similar colors• Redder when brighterlog Fn• Slow and rapid variations share commonproperties

Ks H J• à suggest existence of underlying stable blue component• Intermediate variation is different• Redder when brighter in J-H, small amplitude in J band
• Little change in H-Ks colorlog nRapidly variable component on color-color diagram• Consisitent with either
irradiated disk or synchrotron
emission above cooling breakwith Av≈10• “redder when brighter”
difficult for irradiated disk

Possible broad-band SED

Syn emorton ch ri ssomio n frje tIrdDetai
radiskX-ray
Comptonized
Disk emission

Two new BHCs discovered by MAXI in 2018MAXI J1813-095, MAXI J1820+070• MAXI J1813-095• 2/20 disocvery (Kawase+ ATel #11323)• Swift/XRT localization(Kennea+ #11326)• Radio-quiet BHXB (Russel+ #11356)• INTEGRAL:
power-law w/cutoff at 140 keV→ BHC hard state (Fuerst+ #11357)• MAXI J1820+070• 3/11 discovery (Kawamuro+ ATel#11399)• 0+4h optical counterpart(Deniseko #11400)• Swift XRT localization (Kennea+#11403)• Optical, Radio, X-ray
observations suggests BHC hardstate (#11418, 11420, 11423)
J1820+070

Shidatsu et al. 2018, ApJ

MAXI J1820+070
100.1
10.2
1, 6-20keVpy s-1 cm-2)
MAXI 6-20keV (Photons
10
photons/s/cm2

0.1
1.00.5

1HR (6-20 keV/ 2-6 keV)MAXI/GSC 2−20 keV

mag0.11215-50keV (Counts s-1 cm-2)
12.5
BAT 15-50keV
0.1
13 60
0204080
Days from 2018 Mar. 13 (=MJD13.558190)
1212.51313.51212.5
13
Optical/NIR
13.501020
Bright and highly variable
Days from 2018 Mar. 13 (=MJD 58190)

g’−bandmag

Swift/BAT

2-6keVkeV (Photons s-1 cm-2)
MAXI 2-6

Hard state
No state transition for 80 days

Rc−bandmag

MAXI/GSC

1Ic−band30

MAXI J1820+070
NIR-optical-X-ray spectrum

Shidatsu et al. 2018
submitted to ApJ

2018 March 24PTF

100
keV2 (Photons cm−2 s−1 keV−1)

MAXI/GSC
7yr average

10diskir0.1
power−law
Γ=1.7

WISE
0.01

NIR variable in quiescent state

fout = 5e−3
kTin = 0.35 keV
Rout/Rin = 105

110−4

10−3

0.01

0.1
Energy (keV)

110

Optical/NIR
Irradiate disk + non-thermal

100

MAXI J1820+070

Sako et al. 2018
ATel #11426
Tomo-e Gozen
CMOS camera/Kiso
March 14, 19:30-19:45 UT, 6.15 ms/frame

10-msec scale optical flares
March 14, 18:43-19:20 UT, 16.3 ms/frame

MAXI J1820+070

Red sub-second optical flaring
Gandhi et al. 2018
ATel #11437(Top) 200-second segment of simultaneous ULTRACAM lightcurves,
sampled at a cycle time of 13.8 ms. The g' band lightcurve has been
offset by 0.2 mag to match the r' median. (Bottom) Zoom-in around a
rapid sub-second flare with a peak i' amplitude of 1.6 mag andsubstructure, all within 0.3 s. The stronger red sub-second flaring isapparent in both panels.

Colour-magnitude plot of the ULTRACAM lightcurves,
showing the redder-when-brighter trend.

MAXI J1820+070
NIR-optical-X-ray spectrum

Shidatsu et al. 2018
submitted to ApJ

2018 March 24

PTF

100
keV2 (Photons cm−2 s−1 keV−1)

MAXI/GSC
7yr average

10diskir

0.1
power−law
Γ=1.7

WISE
0.01

NIR variable in quiescent state

fout = 5e−3kTin = 0.35 keV
Rout/Rin = 105

110−4

10−3

0.01

0.1
Energy (keV)

110

Optical/NIR
Irradiate disk + non-thermal

100Latest news on MAXI J1820+070
6–10 keV
Hardness Ratio

Mar 23, 2018!"#$ %&'(") %&'Jul 1

HardàSoft State transition at +120 days
SoftàHard state transition at +190 days

2—20 keV photon flux

Photon Flux
2–4 keVOct 9

Hardness Ratio!"#$ %&'(") %&'Hardness-Intensity diagram

http://maxi.riken.jp/nakahira/1820monitor/

Summary• Transient black hole binaries show non-thermalemission in radio-IR-optical bands.
• Cf. non-thermal X-ray emission - Comptonized• Probably synchrotron emission from the relativistic jet• Jet activity in X-ray “low-hard” state• Also in “very high” or “intermediate state” where thethermal disk emission is present• Interesting to look for Inverse Compton gamma-rayemission