Binary Star System Precisely Timed with Pulsar’s Gamma-rays

0FGL J2339.8–0530 – that is the catalog name of a celestial object which the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope identified as a source of intense gamma radiation in 2009. Observations at other wavelengths in the following years suggested a possible explanation for its nature: a millisecond pulsar in a binary system with a companion star, each orbiting their common center of mass every 4.6 hours. Pulsars are rapidly rotating compact remnants born in the explosions of massive stars. They can be observed through their lighthouse-like beams of radio waves and gamma-rays.

In a binary system whose catalog name is 0FGL J2339.8–0530, the companion’s magnetic activity affects the orbital period of the system. The changing magnetic field interacts with the plasma inside the star and deforms it. As the shape of the star varies its gravitational field also changes, which in turn affects the pulsar orbit (right). This can explain the observed orbital period variations (left). The binary system and the companion are to scale, the pulsar has been magnified. The companion’s deformation is exaggerated

Treasure hunting in archive data reveals clues about black holes’ diet

 

Andrea Merloni and members of his team from the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching, near Munich, were exploring the huge archive of the Sloan Digital Sky Survey (SDSS) in preparation for a future X-ray satellite mission. The SDSS has been observing a large fraction of the night sky with its optical telescope; in addition, spectra have been taken of distant galaxies and black holes. For a variety of reasons, some objects got the spectra taken more than once. And when the team was looking at one of the objects with multiple spectra, they were struck by an extraordinary change in one of the objects under study, with the catalogue number SDSS J0159+0033.

A snapshot image from a computer simulation of a star disrupted by a supermassive black hole. The red-orange plumes show the debris of the star after its passage near the black hole (located close to the bottom left corner of the image). About half of the disrupted star moves in elliptical orbits around the black hole and forms an accretion disc which eventually shines brightly in optical and X-rays. Source: Max-Planck-Gesellschaft

A black hole under the gravitational lens

Sky chart (left) of the enlargement by factors of up to 20, caused by a star in the foreground galaxy. The gamma ray region of the blazar behind it moves across this pattern (white cross). The image this creates (right) is amplified to different degrees. The splitting into several images which can also be seen on the right cannot be resolved with gamma ray telescopes. At the top left of the image on the right is the blazar as it would appear without the lens effect. 

Galaxy HDF850.1 can be seen as it was 12.5 billion years ago

An international team of astronomers led by Fabian Walter of the Max Planck Institute for Astronomy has managed for the first time to determine the distance of the galaxy HDF850.1, well-known among astronomers as being one of the most productive star-forming galaxies in the observable universe. The galaxy is at a distance of 12.5 billion light years. Hence, we see it as it was 12.5 billion years ago, when the universe was less than 10% of its current age. Even more of a surprise, HDF850.1 turns out to be part of a group of around a dozen protogalaxies that formed within the first billion years of cosmic history – only one of two such primordial clusters known to date. The work is being published in the journal Nature.

View of the Northern target area for the "Great Observatories Origins Deep Survey" (GOODS-N). The position of the Hubble Deep Field and, within that field, the position of the submillimeter galaxy HDF850.1, are shown separately. HDF850.1 is invisible for observations using ordinary, visible light. Credit: GOODS-N, STScI / NASA, F. Walter (MPIA)