Abstract
Aims: We report a serendipitous detection of rapid, large amplitude flux
density variations in the highly core-dominated, flat-spectrum radio
quasar 1156+295 during an observing session at the Very Long Baseline
Array (VLBA). Methods: The source was observed as a part of the
MOJAVE survey programme with the VLBA at 15 GHz on February 5, 2007.
Large amplitude variability in the correlated flux density,
unexplainable in terms of the source structure, was first discovered
while processing the data, and later confirmed by calibrating the
antenna gains using 24 other sources observed in the experiment. Results: The source shows variations in the correlated flux density as
high as 40% on a timescale of only 2.7 h. This places 1156+295 between
the classical IDV sources and the so-called intra-hour variables. The
observed variability timescale and the modulation index of 13% are
consistent with interstellar scintillation by a nearby, highly turbulent
scattering screen. The large modulation index at 15 GHz implies a
scattering measure that is atypically high for a high galactic latitude
source such as 1156+295.
Original language | English |
---|---|
Pages (from-to) | L33-L36 |
Journal | Astronomy and Astrophysics |
Volume | 489 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2008 |
MoE publication type | A1 Journal article-refereed |
Keywords
- galaxies: active
- galaxies: jets
- galaxies: quasars:
- individual: QSO 1156+295
- techniques: interferometric
- scattering
- ISM: structure