The neutron-star low-mass X-ray binary GX 9+1

Figure - An artist's impression of an accreting Low Mass X-ray Binary. The donor star fills its Roche lobe and its material overflows the inner Lagrangian points and accretes on the relativistic star. Due to the large angular momentum of the infalling material an accretion disk is formed around the compact object. Credit: ESA, NASA, and Felix Mirabel (French Atomic Energy Commission and Institute for Astronomy and Space Physics/Conicet of Argentina)

A low-mass X-ray binary (LMXB) contains a neutron star which is accreting material via Roche lobe overflow from a companion star. Due to the high angular momentum of the accretion flow an accretion disc is formed around the compact object.

In a recent paper (van den Berg & Homan 2016) the authors have determined an improved position for the luminous persistent neutron-star low-mass X-ray binary and atoll source GX 9+1 from archival Chandra X-ray Observatory data and they have identified a new near-infrared (NIR) counterpart to GX 9+1 in Ks-band images obtained with the PANIC and FourStar cameras on the Magellan Baade Telescope.

The NIR spectrum is consistent with thermal emission from a heated accretion disk, possibly with a contribution from the secondary. In this respect, GX 9+1 is similar to other bright atolls and the Z sources (typical types of neutron-star sources in low mass X-ray binaries, which present a wide variety in X-ray spectral and variability properties) whose NIR spectra do not show the slope that is expected for a dominant contribution from optically thin synchrotron emission from the inner regions of a jet.

van den Berg & Homan - 2016 (accepted in Apj) - On the origin of the near-infrared emission from the neutron-star low-mass X-ray binary GX 9+1 (arXiv)

Comments

ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

A Sapphire Super-Earth

Twenty-one light years away, in the constellation Cassiopeia, a planet by the name of HD219134 b orbits its star with a year that is just three days long. With a mass almost five times that of Earth, it is what is known as a super-Earth. Unlike our planet, however, these super-Earths were formed at high temperatures close to their host star and contain high quantities of calcium, aluminum and their oxides – including sapphire and ruby. HD219134 b is one of three candidates likely to belong to a new, exotic class of exoplanets. These objects are completely different from the majority of Earth-like planets. They have 10 to 20 percent lower densities than Earth. Researchers looked at different scenarios to explain the observed densities. For example, a thick atmosphere could lead to a lower overall density. But two of the exoplanets studied, 55 Cancri e and WASP-47 e, orbit their star so closely that their surface temperature is almost 3,000 degrees and they would have lost this ...

ALMA Discovers Cold Dust Around Nearest Star

This artist’s impression shows how the newly discovered belts of dust around the closest star to the Solar System, Proxima Centauri, may look. ALMA observations revealed the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and indicate the presence of an elaborate planetary system. These structures are similar to the much larger belts in the Solar System and are also expected to be made from particles of rock and ice that failed to form planets. Note that this sketch is not to scale — to make Proxima b clearly visible it has been shown further from the star and larger than it is in reality. Credit: ESO/M. Kornmesser Proxima Centauri is the closest star to the Sun. It is a faint red dwarf lying just four light-years away in the southern constellation of Centaurus (The Centaur). It is orbited by the Earth-sized temperate world Proxima b ...

SpaceTime

Search This Blog