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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