The Case of ESO 243-49 HLX-1 - XMM

Evidence for Intermediate Mass Black Holes
The Case of ESO 243-49 HLX-1
Sean Farrell | Sydney Institute for Astronomy (SIfA), The University of Sydney, Australia
In collaboration with: Natalie Webb (IRAP) | Didier Barret (IRAP) | Mathieu Servillat (CfA) | Olivier Godet (IRAP)
The Case of ESO 243-49 HLX-1
› The discovery of ESO 243-49 HLX-1
› Confirming the redshift with the VLT
› X-ray variability with XMM-Newton, Chandra & Swift
› Radio observations with the Australian Telescope Compact Array
› The UV/optical/near-IR counterpart with Hubble
› Summary & conclusions
The Case of ESO 243-49 HLX-1
Discovery of the Brightest ULX
› HLX-1 discovered coincident with
edge-on spiral galaxy ESO 243-49
(Farrell et al. 2009)
› At galaxy distance of ~100 Mpc,
max. unabsorbed 0.2 – 10 keV
Lx = 1.1 x 1042 erg s-1
› Previous record held by ULX in
Cartwheel galaxy: Lx ~ 1041 erg s-1
(e.g. Gao et al. 2003)
› Large-scale variability with possible
spectral state changes observed,
ruling out multiple sources
VLT R-band image of the galaxy ESO 243-49 with the
position of HLX-1 indicated by the white circle
(Farrell et al., 2009, Nature, 460, 73)
(Godet et al. 2009)
The Case of ESO 243-49 HLX-1
Confirming the redshift
› Faint (R~24 mag) optical counterpart
detected within Chandra error circle
(Soria et al. 2010)
› Follow-up spectroscopy with VLT
detected Hα in emission at redshift
consistent with host galaxy
(Wiersema et al. 2010)
Above: VLT I-band images of ESO 243-49 before (top) and after
(bottom) subtraction of the diffuse galaxy light. Right: FORS2
spectra, red = HLX-1, blue = background, black = bkg subtracted
The Case of ESO 243-49 HLX-1
X-ray variability
› Significant variability by a
factor of ~50 observed
~380 d?
~380 d
› Light curve follows Fast Rise
Exponential Decay (FRED)
› Timescale incompatible with
thermal-viscous disc
instability model
› Radiation-pressure disc
instability may be possible
(physics still controversial;
Hirose et al. 2009a,b)
› Modulated mass-transfer
due to tidal stripping of
companion star in eccentric
orbit more likely
Swift X-ray Telescope (XRT) Light Curve of HLX-1
(Lasota et al. 2011)
Godet et al. 2009; Lasota et al. (2011); Servillat et al. (2011)
The Case of ESO 243-49 HLX-1
Belloni (2010)
Servillat et al. (2011)
See Poster B25 by Mathieu Servillat
LED ~ 1.1 x 1042 erg s-1, MBH ~ 8,500 M
The Case of ESO 243-49 HLX-1
X-ray spectral state transitions of HLX-1
Thermal plasma
contribution from
host galaxy
› HLX-1 observe to transition
between high/soft, soft
intermediate, and low/hard states
› Temperature varies as Ldisc ~ T4,
consistent with geometrically thin
optically thick disc
› Fitting thermally dominated spectra
with relativistic models (BHSPEC,
KERRBB, KERRDISK) constrains
mass to ~103 < MBH < 105 M
(Davis et al. 2011; Godet et al. 2011)
Servillat et al. (2011)
The Case of ESO 243-49 HLX-1
Athena vs XMM-Newton
The Case of ESO 243-49 HLX-1
› Observed HLX-1 with ATCA following
transition from low/hard to high/soft
See Poster B30
› Detected 40 μJy point source at X-ray
position (4.2σ when compared to
Webb et al. 2011)
by background
Natalie flux;
› Follow-up observation ~3 months
later failed to detect radio emission
› Variability rules out radio nebula
› Radio emission most likely
associated with jet-ejection event
› Using fundamental plane relation (e.g.
Fender et al. 2009), mass constrained to
< 105 M
Webb et al. (2011)
The Case of ESO 243-49 HLX-1
HST Imaging of HLX-1
In Sept 2010 we obtained HST observations of HLX-1 in 6 bands (Farrell et al. in prep)
The Case of ESO 243-49 HLX-1
Composite 6-band HST image (Farrell et al. 2011, in prep)
The Case of ESO 243-49 HLX-1
Bkg galaxies
VLT FORS2 2-D spectrum
Why Hubble is necessary…
The Case of ESO 243-49 HLX-1
HST SED fitted with stellar population models
Fλ (photons/cm2/s/Å)
› Fitted HST data with
Maraston (2005)
simple stellar
population models
› X-ray spectrum
indicates contribution
from accretion disc,
so treat UV points as
upper limits
› Age, Z, and Av are
degenerate, but SED
most consistent with
young population
› Ages >>100 Myr not
consistent with SED
Farrell et al. (2011)
Wavelength (Å)
The Case of ESO 243-49 HLX-1
Broad-band Spectral Energy Distribution Fitting
› X-ray & UV bands
described by irradiated disc
› Red optical & H-band data
not consistent  need
stellar population
› Disc temp consistent with
~10,000 M black hole
› FUV luminosity of 7 x 1039
erg s-1 inconsistent with
beamed emission from
stellar mass black hole
Farrell et al. (2011)
The Case of ESO 243-49 HLX-1
Summary & Conclusions:
› X-ray luminosity of HLX-1 varies from ~10 – 400 times Eddington limit of
20 M black hole
› Spectral hysteresis observed very similar to Galactic black hole binaries
› Transient radio emission from jet ejection event  first detection of jets
from a ULX
› Mass estimates from Eddington scaling, accretion disc continuum fitting,
and jet flare luminosity all support MBH ~ 104 M
› Broad-band SED fitting indicates disc emission dominates X-ray & UV
bands, with young stellar population accounting for redder emission
› UV disc luminosity and disc irradiation rule out beaming
› Derived stellar ages inconsistent with globular cluster, instead implying
HLX-1 could be nucleus of stripped dwarf galaxy accreted by ESO 243-49
The Case of ESO 243-49 HLX-1
Thank you to all my collaborators:
› Natalie Webb, Didier Barret, Olivier Godet, Dacheng Lin (IRAP, France)
› Jean-Pierre Lasota (IAP, France/Jagiellonian University, Poland)
› Guillaume Dubus (IPAG, France/IAP, France)
› Mathieu Servillat, Ramesh Narayan, Yucong Zhu (Harvard-Smithsonian CfA, USA)
› Neil Gehrels (NASA GSFC, USA)
› Shane Davis (CITA, Canada)
› Tom Maccarone, Christian Knigge (University of Southampton, UK)
› Klaas Wiersema (University of Leicester, UK)
› Claudia Maraston, Janine Pforr (Portsmouth University, UK)
› Andrew Gosling, Ian Heywood (Oxford University, UK)
› Samantha Oates (MSSL, UK)
› Tal Alexander (Weismann Institute of Science, Israel)
› Emil Lenc (CSIRO Astronomy & Space Science, Australia)
The Case of ESO 243-49 HLX-1
The Soft Thermal Excess in ULX Spectra
For Shakura-Sunyaev
α-discs: Ldisk ~ Tin4
However, for most ULXs:
Ldisk ~ Tin-3.5
Soft component for bulk of
ULXs most likely from
outflow such as disc-wind
HLX-1 soft excess varies as
predicted for an α-disc
Servillat et al. (2011)
L vs Tdisk of a sample of ULXs from Kajava & Poutanen (2009)
The Case of ESO 243-49 HLX-1
The Black Hole Fundamental Plane
› Black hole binaries
emit radio flares
during transition from
L/H  H/S
Adapted from Merloni et al. (2003)
(e.g. Fender et al. 2009)
› Flare radio emission
can be ~10 times
non-flare luminosity
Log ( L X )  1 .41 Log ( L R )  0 .87 Log ( M BH )  5 .01
› Applying same
scaling to HLX-1
gives M ~104 M,
› Radio detection
gives conservative
upper limit of 105 M
The Case of ESO 243-49 HLX-1
Composite 6-band HST image (Farrell et al. 2011, in prep)

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