Transcript An Unsolved Issue

Light Curves
• These light curves were taken by the
Swift Gamma-Ray Burst Explorer &
Rossi X-Ray Timing Explorer
• Each graph plots the counts of x-rays
with a particular energy per second
over the duration of the event
• Before the outburst, the flux from
the system was consistently 1/100th of
the peak
• ‘Hard’ x-rays are higher energy than
‘soft’ x-rays
• As we will see in the next slide, we
care about the ratio of the hard flux
(E > 5 keV) to the soft flux (E <5keV)
Light curves of the outburst taken from Krimm et al.
•This ratio is called the hardness
Current Interpretation
•The outburst decay rate was consistent with an x-ray burst transient
•The spectra1 showed what Krimm et al. interpreted as an iron line at 6.72 ± .58 keV
•Observations have found have found very low flux at quiescence
•This suggests that the companion star is of low mass
• Two possibilities for a LMXRB – a black
hole or a neutron star
•Neutron star x-ray hardness/intensity
curves either trace a distinct Z shape (socalled ‘Z Sources’) or lack the observed
hard/high flux
• The transitions from hard to softintermediate are thought to be faster with
neutron stars
Hardness vs. Flux (Intensity), taken from Krimm et al.
1The
paper did not include individual spectrum
Further Evidence for Candidacy
• Swift J1539.2-6227 shares many traits
with confirmed BH outbursts
• Rapid rise of hard X rays followed by a
soft flux about 8 days later is very
similar to confirmed BH GRO J155-40
• Temporary hardening in the middle of
the outburst very similar to XTE
J1859+266
• PL index, disk fraction, and rms power
all correlate with X-ray hardness in a
way that is indicative of a black hole
(see figure)
• In addition to these shared traits, no
pulsations were observed during the
recorded outburst
Hardness vs. key features from Krimm et al.
An Unresolved Issue
• Mass from the companion star falls onto
the compact object until an outburst occurs
• The properties of the outburst can help
identify the compact object
• The outburst of Swift J1539.2-6227 shows
several features of a BH, but no high-energy
radio jet was observed
Could Swift J1539.2-6227 be a neutron star
or an anomalous nova? (most likely not)
Jet of M87’s Supermassive BH
• This is a problem because these jets are
an integral part of BHs
• Due to the power of a BH’s magnetic
field, you would not expect to see a BH
without seeing a jet in every wavelength!
• Without a jet in the radio we can’t
define of Swift J1539.2-6227 as a BH
Detecting High Energy Radio Jets
1) Material rotates around BH, some of which is
Ionized.
2) Ionized Material causes moving charges,
which in-turn creates a B-field which in this case
twists causing streams of jets that can be observed
by ground-based radio observatories.
Very Large Array
Typical radio images from a BH.
Proving this anomaly
is indeed a BH.
Reason why H. A. Krimm et al. did not have radio data.
• Lack of observation time needed to confirm that this is
a BH.
• However there is really sufficient evidence to deduce
that it most probably is a BH without radio data.