DYNAMICAL MASSES IN BLACK HOLE X-RAY BINARIES

Jorge Casares (IAC)

Outline1.- Dynamical Masses: techniques, limitations and

systematics

2.- Bowen emission: dynamical masses during outburst

3.- Search for dormant BH XTs: IPHAS/UVEX surveys

4.- Conclusions

• Mass distribution of BHs has strong impact in SNe models, evolution of massive stars, chemical enrichment

• Stellar evolution models predict ~ 108 BH remnants (Brown & Bethe 94).

• But only BHs in interacting binaries can be easily detected

and weighed accurately.

• Best evidence for BH is dynamical i.e. a compact object with Mx > 3 M

1.- BHs in XRBs

The Classic Method: Weighing BHs

1) Radial velocity curve

BHs do not burst nor pulse dynamical

information must be extracted from donor star.

Three experiments:

f (M) < MX

2

33orb

)1(

sin

2)(

q

iM

G

KPMf X

q=MC/MX

V404 Cyg

R=λ/Δλ≥1500 required

Weighing BHs

2) Measure Vrot sini

XC

rot

MMq

qqK

iV

/

)1(462.0sin 3/23/1

R=λ/Δλ≥5000 required

e.g. in V404 Cyg we measure Vsini=40 km/s and then q=0.06

Weighing BHs

3) Fit ellipsoidal modulation

Amplitude is strong function of inclination

GRO J1655-40 (Orosz & Bailyn. 97)

f(M) + q + i complete solution

BHs in HMXBs: Cyg X-1

Typically O9.7 Iab has ≈ 33 M (and then MX ≈ 7 M, i=90º)

2

33orb

)/1(

sin

2)(

XC

X

MM

iM

G

KPMf

= 0.25 M

• Optical counterpart: O9.7 Iab (=HD 226868)

• Velocity K= 64 km/s and Porb= 5.6 d. (Webster & Murdin; Bolton 1972)

• Mass transfer is powered by stellar winds determination of q & i through Vsini and ellipsoidal fits can be biased low

• But donor likely undermassive by factor ≤3 (van den Heuvel & Ostriker 73)

M33 X-7: First eclipsing BHEclipsing X-ray source with a 3.45d period (Peres et al. 1989)

First ellipsoidal fits and radial velocity curve of the O7-8III donor (Orosz et al. 2007)

Eclipse+distance constrain parameter space:

RC=19.6±1 R, f=0.78±0.02 i=74.6±1.0o

Mc=70±7 M Mx=15.7±1.5 M

BHs in X-ray Transients

A0620-00

QUIESCENCE: companion dominates optical flux radial velocity studies

OUTBURST: Companion 103 fainter than X-ray irradiated disc

Low mass donors have no winds and fill Roche lobes

System Porb f(M) Spect. Type Classification Mx

GRS 1915+105 33.5 d: 9.5 ± 3.0 M K/MIII Transient 14.0 ±4.4 M

V404 Cyg 6.470 d 6.08 ± 0.06 M K0IV ,, 12 ±2 M

Cyg X-1 5.600 d 0.244 ± 0.005 M 09.7Iab Persistent 10 ± 3 M

LMC X-1 4.229 d 0.14 ± 0.05 M 07III ,, 10.9 ± 1.4 M

M33 X-7 3.453 d 0.46 ± 0.08 M 07-8III ,, 15.7±1.5 M

XTE J1819-254 2.817 d 2.74 ± 0.04 M B9III Transient 7.1 ± 0.3 M

GRO J1655-40 2.620 d 2.73 ± 0.09 M F3/5IV ,, 6.3 ± 0.3 M

BW Cir 2.545d 5.75 ± 0.30 M G5IV ,, >7.8 M

GX 339-4 1.754 d 5.8 ± 0.5 M -- ,, >6.0 M

LMC X-3 1.704 d 2.3 ± 0.3 M B3 V Persistent 7.6 ± 1.3 M

XTE J1550-564 1.542 d 7.65 ± 0.38 M G8/K8IV Transient 9.1 ±0.6 M

4U 1543-475 1.125 d 0.25 ± 0.01 M A2V ,, 9.4 ±1.1 M

H1705-250 0.520 d 4.65 ± 0.21 M K3/7V ,, 6 ±2 M

GS 1124-684 0.433 d 3.01 ± 0.15 M K3/5V ,, 7.0 ± 0.6 M

XTE J1859+226 0.382 d : 7.4 ± 1.1 M : -- ,,

GS2000+250 0.345 d 5.01 ± 0.12 M K3/7V ,, 7.5 ±0.3 M

A0620-003 0.325 d 2.72 ± 0.06 M K4V ,, 6.6 ±0.3 M XTE J1650-500 0.3205 d 2.73 ± 0.56 M K4V ,, >2.5 M GRS 1009-45 0.283 d 3.17 ± 0.12 M K7/M0V ,, 5.2 ± 0.6 M

GRO J0422+32 0.212 d 1.19 ± 0.02 M M2 V ,, 4 ± 1M

XTE J1118+480 0.171 d 6.3 ± 0.2 M K5/M0V ,, 6.8 ± 0.4 M

Galactic Black Holes with dynamical evidenceOrosz 2003; Charles & Coe 2006

Orosz et al. 2009 (LMC X-1), Cantrell et al. 2010 (A0620-00); Orsoz et al. 2010 (J1550-564)

P=30.8d Neil et al. 2007

Filippenko & Chornock 2001 IAUC7644

Late Results on XTE J1859+226

GTC 10.4m spectroscopy

2x3 hr blocks in July & Aug 2010

K≈520 km/s

f(M)=4-4.5 M

Orbital period is not 9.2 hr (Filippenko & Chornock 2001 IAUC 7644) but either 6.6 or 7.7 hr

Corral-Santana et al. 2010 submitted

9.2 hr

Typical errors 20%

Mass spectrum of BHs17 reliable masses of BHs: 4-16 M

– Do BH masses cluster at a particular value?– What are the edges of the BH distribution?

Limited by errors and poor statistics New strategies required

Systematics in Ellipsoidal Fits 1) Superhumps: modulation a few % longer than orbital caused by precessing disc

XTE J1118+480: near quiescence (Zurita et al. 2002)

Typically seen in outburst, when disc exceeds 3:1 resonance radius (O’Donoghue & Charles 1996)

Systematics in Ellipsoidal Fits2) Rapid aperiodic variability:

Zurita, Casares & Shahbaz (2003)

All SXTs show flaring activity when observed at high time resolution.

~ 6hr flares in V404 Cyg Pavlenko et al. (1996)

flaring originate in the disc whose contribution fades with λ Fits in the IR assumed to be safe

Systematics in Ellipsoidal Fits2) Rapid aperiodic variability: varies with time for a particular system

Cantrell et al. (2008)

i=51 ± 1 deg Mx=6.6 ± 0.3 M Cantrell et al. (2010)

i=37 ± 6 deg Mx=10 ± 2 M Shahbaz et al. (1994)

i=41 ± 3 deg Mx=11 ± 2 M Gelino et al. (2001)

A0620-00

Critical because inclination dominates the mass error budget

The Future: astrometry of donor stars

Space Interferometry Mission (SIM 2016)

Will provide accurate inclinations and masses ≤5%

calibrate ellipsoidal fits

High sensitivity : 20th mag

Angular resolution: 3.5μas

BH BINARY a/D (μas)V404 Cyg 61GRS J1915+105 40Cyg X-1 33GRO J1655-40 18A 0620-00 14

VLTI+GRAVITY(2013): will provide 10 μas for mK=15 and will resolve V404 Cyg and GRS 1915+105

SWIFT J1753-0127: remained in low-hard state since discovery

32 BH Candidates: prime targets for rv studies

2005 2007 2009 2010

Evidence for superhump variability with P=3.24hr (Zurita et al. 2008)

Shortest period BH binary

Outburst Amplitude vs Porb correlation (Shahbaz & Kuulkers 1998)

BH Candidates: SWIFT J1753.5-0127

Since P=3.24hr then ΔV ≈ 10 and Vquiescent ~ 26

Too faint for dynamical studies

Black Hole Candidates

Only a few are brighter than R~23 (limit of 10m Telescopes)

Beyond R~23 we need ELT

New strategies to expand sample of dynamical BHs:

1.- Dynamical studies during outburst

2.- Search for new quiescent BHs

Steeghs & Casares 2002

NIII/CIII HeII

● Classic Black Hole candidate● Quiescence in 2000-01 ● 2002 outburst

NIII/CIII emission lines

Shahbaz et al. 2001

AAT+NTT VLT

Bowen Emission from the Donor

Detection of sharp high excitation emission lines

Most prominent are CIII/NIII at λλ4630-40

NIII powered by fluorescence

Doppler shift traces orbit of heated companion

GX 339-4

1.- Dynamical studies during outburst:

GX 339-4

Kem=317 ±10 km/s K2 f(M) 5.8 ± 0.5 M Black Hole!!

(Hynes et al. 2003 ApJ 583 L95)

Multigausian fit to NIII lines

Determine f (M) in new SXTs during outburst before they fade (and are lost in quiescence)

Porb=1.76 d from HeII velocities

Echo Tomography● Time delays between X-ray and optical variability to map reprocessing regions in a

binary

O(t) = X(t) * T(t-)

T(t-) depends on geometry and varies with orbital phase

• disc geometry

• binary separation a

• inclination i

• mass ratio q=M2/MXCredit: K.0’Brien

Most works use broad band filters delays consistent with disc reprocessing

=0.42

=0.52

=0.60

=0.73

Bowen line Echo Tomography : Sco X-1

W5

W4

W1 W2

W3

Muñoz-Darias et al. 2007 Flaring Branch

Narrow filters to amplify reprocessed signal from companion: Bowen+HeII & continuum continuum subtracted lightcurves of lines

Discovered at a rate ~1.7/yr since GINGA

BH SXTs known are the tip of iceberg of Galactic population

BH demography: how many?

Extrapolation of SXTs since late 80’s + assuming outburst duty cycle ~ 50 yrs suggest ~ 103 dormant BH SXTs (van den Heuvel 93, Romani 98)

17 dynamical BHs

32 BH candidates

XTE

GINGA

GRANAT

CGROASCA

SAX

INTEGRAL

SWIFTMAXI

Cen

X-2

ROSAT

2.- Search for new quiescent BHs

The IPHAS/UVEX Survey

● INT Photometric Surveys of the northern Galactic plane (|b|<5º) in Hα , r’,i’ (IPHAS) and u’,g’, HeI5876 (UVEX) down to r’=20 (Drew et al. 2005)

● Covers ~1800 sq. deg with ~5x105 Hα emitters in 300 Mill. stellar objects (0.1%)

CV

BH XRT

IPHAS/UVEX/2MASS

Cross-match of IPHAS/UVEX /2MASS with these colour cuts yields ~5000 candidates.

Most will still be contaminants so follow-up spectroscopy required

for confirmation.

Conclusions

● Best way to measure BH masses is through dynamical studies of X-ray binaries

● SXTs provide many more & cleaner cases than HMXBs: 17 confirmed BHs with masses in the range 4—14 M

(caution with systematics in ellip. mod. and hence i)

● Tip of iceberg of hidden population of ~103 BH binaries● Better statistics & ≤10% errors needed to derive

constraints to close binary evolution and SNe models.

Conclusions

2 possible avenues to increase the population:● Exploit Bowen Fluorescence to get dynamical

information during outburst.● Discover new hybernant BHs using appropriate

colour cuts in deep surveys such as IPHAS/UVEX.

Faint quiescent counterparts in crowded fields hamper radial velocity studies of donor star

XTE J1752-223

OUTBURST: 26 Oct 2009 IMACS i=15-16

Torres et al. ATel#2263

DECAY TO QUIESCENCE: Aug 2010 WHT i>18.9

Russell et al. ATel #2775

Corral-Santana et al. ATel #2818

• Radial velocity curve of the 06.5V((f)) indicate Porb=3.906 d (Casares et al. 2005). But the orbital parameters depend on the spectral lines used.

• First γ-ray Binary detected by HESS at TeV with Lγ=1034 ergs/s

A low mass BH in LS 5039 ?

We adopted the HeII solution

HI and HeI may be contaminated by wind emission because show larger scatter and the solution is blue-shiftted (as expected by contamination from P-Cygni)

• Spacially resolved radio emission Microquasar or pulsar wind?

1) We fitted UNIFIED MODELS (NLTE+Sphericity) to stellar spectrum to yield Teff, log g, M, R and V∞

The result suggests that LS 5039 might be a black hole with 3-5 solar masses

2) Donor almost fills Roche lobe at periastron assume is pseudo-synchronized

Combining 1+2+orbital solution we get a full solution to the masses.

iPRe

eiV c sin

)1(

)1(2sin 1

orb2/3

2/1

i = 23.2 -- 26.8o

BH Candidates

TOTAL = 49 BH transients in 44 years, 17 with dynamical evidence

Kem/K2= 1- f (1+q) with f () 1

The K-correction Measures the displacement of emission line region wrt center of mass

0 f 1

Real K2 can be determined with extra information on q and .

Muñoz-Darias et al. 2005

f = 1

f = 0

( = disc opening angle)

XTE/VLT campaign on burster 4U 1636-536

3 bursts detected at orbital phases 0.20, 0.55 and 0.83

June 2007

χ2 fits to the 3 burst delays as function of continuum subtraction yields i=45-50deg and optimum subtraction ~0.85

Muñoz-Darias, O’Brien et al., in preparation

Time lag varies with amount of continuum subraction, approaching prediction for model with Mns=1.4 Msun, q=0.3, i=36-60, α=12deg