Transcript ppt - ciera

The UltraLuminous X-ray
source NGC 1313 X-2
Paola
Mucciarelli
Department of Astronomy, University of Padova
Department of Physics, University of Padova
INAF-Astronomical Observatory of Padova
In collaboration with:
• Zampieri, Turolla, Treves, Falomo,
Chieregato, Kaaret & di Stefano.
NGC1313 X-2: X-ray properties
 NGC1313 is a nearby spiral
galaxy hosting two ULXs,
NGC1313 X-1 and X-2, and the
interacting supernova 1978K.
NGC1313 X-1
NGC1313 X-2
 NGC1313 X-2 is a well known ULX,
variable on a timescale of
months.
 Assuming that at maximum the
source radiates at the Eddington
limit, a mass of 50 M is derived
for the compact remnant.
♣ The XMM spectrum shows
statistical evidence for a
MCD component with kT=0.2 keV
(Miller et al. 2003 ,Zampieri
et al. 2004)
MBH~ 90f4 M
MODEST-6, August 29-31, 2005
NGC1313 X-2: optical counterpart
NGC 1313 X-2 optical counterpart was identified
in an ESO 3.6m R band image, using the Chandra
position with an uncertainty of 0.7 (Zampieri et
al., 2004).
In archive ESO VLT (BVR) band images the
counterpart is resolved in two distinct
point-like sources, C1 and C2, separated
by 0.7”(Mucciarelli et al., in prep.).
Taking into account Galactic absorption:
C1: R=23.5, (B-V)0=-0.2
(V-R)0=-0.2
C2: R=23.4, (B-V)0>1.0
(V-R)0=0.4
(R-I)0=0.2(from
Liu et al. 2005)
Both object are nor an AGN (absence of
redshifted emission lines and very high
fX/fR) neither foreground stars.
MODEST-6, August 29-31, 2005
C1: BO-O9 main sequence star of 20M
in NGC 1313
C2: G supergiant of about 10M in
NGC 1313
Conclusions
Two optical counterparts are detected (on VLT
images) inside the Chandra error box of the ULX
NGC 1313 X-2.
Irrespectively of wich of the two objects is the
actual counterpart, NGC 1313 X-2 appears to be a
high mass X-ray binary with a massive donor star.
At the present stage, there seems to be no
compelling argument to rule out any of the two
object C1 and C2 as possible counterpart.
Follow up optical spectroscopy under optimal
seeing conditions and with the slit along the line
of conjunction C1-C2 is crucial to disentangle the
emission from the two objects.
Theoretical modelling may also help to
distinguish the counterpart
(Patruno & Zampieri, in prep.)
MODEST-6, August 29-31, 2005