Black Holes and related projects

Black Holes and related projects

Black holes exist in various places in the Universe. The University of Athens Observatory performs follow-up observations in some special cases, where multi-wavelegth campaigns aim towards understanding their nature.

OJ 287 is a BL Lac object (blazar) at redshift z = 0.306 that has shown double-peaked bursts at regular intervals of ~12 yr during the last ~40 yr. Optical photopolarimetric monitoring data from 2005 to 2009 were studied, with the aim to analyse variability patterns and statistical properties of the optical polarization light curve. A strong preferred position angle in optical polarization was found after this study. The preferred position angle can be explained by separating the jet emission into two components: an optical polarization core and chaotic jet emission. This can possibly suggest that both the double-peaked bursts and the evolution of the optical polarization position angle could be explained as a sign of resonant accretion of magnetic field lines, a 'magnetic breathing' of the disc.

Artistic impression of blazar OJ 287 and a combined X-ray (Chandra) and radio image (VLA).

The study of the binary black hole OJ287 is still undergoing and so far it gave two publications in refereed journals:

  • Villforth et al. 'Variability and stability in blazar jets on time-scales of years: optical polarization monitoring of OJ 287 in 2005-2009', 2010, MNRAS, 402, 2087

  • Valtonen et al. 'Tidally Induced Outbursts in OJ 287 during 2005-2008', 2009, ApJ, 698, 781

  • Optical Monitoring Of The Active Black Hole V404 Cyg was started on 15 June 2015, after the SWIFT trigger for a possible gamma-ray busrt. This black hole binary was followed for the next 75 nights in optical R-band, utilizing the 0.40 m f/8 robotic and remote controlled telescope at the University of Athens Observatory.

    The black hole binary system V404 Cyg gave a large outburst on June 15, 2015. An artistic representation of the binary system is given at top left figure, while a sample of an active photometric behavior is shown at top right figure. Continuous monitoring of this target from the University of Athens Observatory resulted in a 75-day long photometric light curve, part of which is shown in the bottom plot.

    The study of V404 Cyg resulted so far in the following announcements:

  • Gazeas, K.; Vasilopoulos, G.; Petropoulou, M.; Sapountzis, K., 2015, ATel, 7650, 1
  • Vasilopoulos G, Gazeas, K., Petropoulou M., Sapountzis K., 2015, 12th HEL.AS. Conference, Thessaloniki, Greece

  • Team members

    Collaboration between the University of Athens (Greece) and several other Institutes worldwide. Among them, the major collaborators are:

  • Kosmas Gazeas, Apostolos Mastichiadis, Konstantinos Sapountzis
  • University of Athens, GR 15784 Zografos, Athens, Greece
  • Maria Petropoulou
  • Purdue University, West Lafayette, Indiana, IN 47907-2036, USA
  • George Vasilopoulos
  • Max-Planck-Institut für extraterrestrische Physik, Garching bei Muenchen, D-85741, Germany
  • Stazsek Zola, Gopal Bhatta, Arti Goyal
  • Astronomical Observatory of the Jagiellonian University, Krakow, ul. Orla, 30-244, Poland
  • Alexios Liakos
  • National Observatory of Athens, Greece

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