Light Curves

1. 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) • This ratio is called the hardness Light curves of the outburst taken from Krimm et al.

2. 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 (so-called ‘Z Sources’) or lack the observed hard/high flux • The transitions from hard to soft-intermediate are thought to be faster with neutron stars Hardness vs. Flux (Intensity), taken from Krimmet al. 1The paper did not include individual spectrum

3. 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.

4. 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) • 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 Jet of M87’s Supermassive BH

5. Detecting High Energy Radio Jets Material rotates around BH, some of which is Ionized. 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.