Neutron Stars/X-ray Binaries

Jeremy Hare

We are very pleased to welcome Jeremy Hare as a guest blogger today. Jeremy is a co-author of a study led by George Pavlov from Pennsylvania Statue University and Oleg Kargaltsev from George Washington University that is the subject of our most recent press release, on a binary system named LS 2883. Jeremy is about to begin his fourth year of graduate school at GWU working under Oleg Kargaltsev. He studies high-mass gamma-ray binaries, mainly in X-rays, and the classification of X-ray sources using machine learning. He tells us that LS 2883 was the first research project he worked on in graduate school and that it has been “very exciting to study!”

High mass gamma-ray binaries are rare objects in the Galaxy. These binaries consist of a massive star (usually with a mass greater than 10 solar masses) and a compact object, a neutron star or black hole. Many high-mass stars have a disk of material around them, which the compact object can interact with as it nears the star in its (often elliptical) orbit. High-mass gamma-ray binaries can accelerate particles to extreme energies of 10 TeV (=1012 electron volts, or eV) or higher, which is comparable to the energies that are currently being produced at the Large Hadron Collider. These particles then scatter off of lower energy photons (packets of electromagnetic energy that make up light) produced by the star, transferring some of their energy and boosting the photon’s energy to the GeV (109 eV) and TeV energy range.

We are pleased to welcome guest blogger Sebastian Heinz, a Professor in the Astronomy Department at the University of Wisconsin-Madison. Sebastian led the team that discovered light echoes around Circinus X-1, the subject of our latest press release. He received his Ph.D. at the University of Colorado at Boulder. He studies relativistic jets − a phenomenon observed around black holes and neutron stars and started investigating the neutron star Circinus X-1 star when he was a Chandra Postdoctoral Fellow at MIT.

Some astronomical discoveries are straightforward − you observe something and it is immediately clear what you have found and what the consequences are. Often, though, astronomy requires the combination of different people’s skills and different kinds of data to solve a puzzle. This was definitely one of those puzzles.

When we downloaded the data from our long Chandra observation of the neutron star Circinus X-1 in early 2014, it was immediately clear that we were looking at an exceptionally bright light echo. Light echoes are created just like sound echoes, when light waves bounce off an obstacle (in this case dust clouds). Because their path has a kink in it, the bounced light waves take longer to arrive at the telescope than the waves that didn't bounce. Our echo resulted from a two-month long huge X-ray outburst Circinus X-1 had had in late 2013 (see the X-ray movie from MAXI included here), making it the largest, brightest, most spectacular set of X-ray rings to date, which is why we jokingly call Circinus X-1 the "Lord of the Rings".

Data from NASA's Chandra X-ray Observatory has helped provide a rare opportunity to determine the distance to an object on the other side of the Milky Way galaxy, as described in our latest press release

A supernova that signals the death of a massive star sends titanic shock waves rumbling through interstellar space. An ultra-dense neutron star is usually left behind, which is far from dead, as it spews out a blizzard of high-energy particles. Two new images from NASA's Chandra X-ray Observatory provide fascinating views - including an enigmatic lobster-like feature - of the complex aftermath of a supernova.

Nanda Rea. Credit: N. Rea

Last week, the Committee on Space Research (COSPAR) announced the awards that will be presented at their upcoming meeting in August in Moscow. One of the winners of the Yakov B. Zeldovich Medals -- a joint award of COSPAR and the Russian Academy of Sciences conferred on young scientists for excellence and achievements – will go to Nanda Rea.

Dr. Rea is an assistant professor at the Institute of Space Sciences (CSIC-IEEC) in Barcelona and the Anton Pannekoek Institute (API) at the University of Amsterdam. She has spent much of her career studying magnetars, a special class of neutron stars that have some of the strongest magnetic fields in the Universe.

An extraordinary jet trailing behind a runaway pulsar is seen in this composite image that contains data from NASA's Chandra X-ray Observatory (purple), radio data from the Australia Compact Telescope Array (green), and optical data from the 2MASS survey (red, green, and blue). The pulsar - a spinning neutron star - and its tail are found in the lower right of this image (mouse over the image for a labeled version). The tail stretches for 37 light years , making it the longest jet ever seen from an object in the Milky Way galaxy, as described in our press release.

Lucia Pavan graduated with a master thesis in astronomy at the University of Padova (the same town from which Galileo discovered Jupiter's moons). Four years later she also got her PhD in Physics at the same university, working on "magnetars" -a particular kind of pulsars, with the highest magnetic fields. After the PhD, she obtained a postdoc position at the University of Geneva - Switzerland, working at the INTEGRAL Science Data Center (ISDC). In between, she moved to the US, working at University of Wisconsin-Madison for a few months. She currently lives in Geneva, working at the ISDC.

When I started to work on the sources discovered by the INTEGRAL satellite, I didn’t expect to find an object that was extraordinary not only for the properties of its emission, but also for its extension and shape in the sky. And yet this was the case when I came across IGR J11014-6103.

INTEGRAL is an ESA satellite in operation since 2002, sensitive mainly to X-ray and gamma-ray bands. The satellite has been accumulating data since the beginning of the mission, providing information on an always-growing number of X-ray emitters. It is thanks to this ability that new objects are continuously discovered. A large fraction of the sources that INTEGRAL has found still lacks any physical classification, a perfect area for new findings to be done.