Intra-night optical variability of misaligned active galaxies

Debbijoy Bhattacharya, Sanna Gulati, C. S. Stalin

Research output: Contribution to journalArticle

Abstract

The majority of the γ -ray sources detected by the Fermi Gamma-ray Space Telescope belong to the blazar class of active galactic nuclei (AGNs). In addition to blazars, a minority of non-blazar AGNs is also found to be γ -ray emitters. A class of AGNs with large jet to line-of-sight angle are termed as misaligned AGNs (MAGNs). A significant fraction of γ -ray emitting non-blazar AGNs belong to this class. The detection of these sources in γ -rays suggests that most of their emission originate in the jet. Considering jet origin of intra-night optical variability (INOV), one thus can expect to observe strong presence of INOV in these γ -ray detected MAGN. However, no observations exist on their INOV nature. We therefore, have carried out a first search for INOV on a sample of six MAGN, that comprises three FR I, two Steep Spectrum Radio Quasars (SSRQs)/Compact Steep Spectrum (CSS) and one FR II galaxy. Our observations carried out on a total of eight nights for a duration of ∼29 h, reveal that MAGNs show large amplitude (between 2 and 10 per cent) INOV with a duty cycle of about 50 per cent, including both variable and probably variable sources, which is similar to that shown by blazars. Though INOV has been detected in MAGNs, differences if any between the INOV characteristics of FR I, SSRQs/CSS, and FR II types of MAGNs could not be unambiguously established owing to limited observations. Nevertheless, the first detection of INOV in MAGNs points to their jet based origin.

Original languageEnglish
Pages (from-to)3382-3389
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume483
Issue number3
DOIs
Publication statusPublished - 01-01-2019

Fingerprint

active galaxies
night
active galactic nuclei
rays
radio
radio spectra
blazars
quasars
Fermi Gamma-ray Space Telescope
minorities
line of sight
emitters
galaxies
detection
cycles

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Intra-night optical variability of misaligned active galaxies",
abstract = "The majority of the γ -ray sources detected by the Fermi Gamma-ray Space Telescope belong to the blazar class of active galactic nuclei (AGNs). In addition to blazars, a minority of non-blazar AGNs is also found to be γ -ray emitters. A class of AGNs with large jet to line-of-sight angle are termed as misaligned AGNs (MAGNs). A significant fraction of γ -ray emitting non-blazar AGNs belong to this class. The detection of these sources in γ -rays suggests that most of their emission originate in the jet. Considering jet origin of intra-night optical variability (INOV), one thus can expect to observe strong presence of INOV in these γ -ray detected MAGN. However, no observations exist on their INOV nature. We therefore, have carried out a first search for INOV on a sample of six MAGN, that comprises three FR I, two Steep Spectrum Radio Quasars (SSRQs)/Compact Steep Spectrum (CSS) and one FR II galaxy. Our observations carried out on a total of eight nights for a duration of ∼29 h, reveal that MAGNs show large amplitude (between 2 and 10 per cent) INOV with a duty cycle of about 50 per cent, including both variable and probably variable sources, which is similar to that shown by blazars. Though INOV has been detected in MAGNs, differences if any between the INOV characteristics of FR I, SSRQs/CSS, and FR II types of MAGNs could not be unambiguously established owing to limited observations. Nevertheless, the first detection of INOV in MAGNs points to their jet based origin.",
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Intra-night optical variability of misaligned active galaxies. / Bhattacharya, Debbijoy; Gulati, Sanna; Stalin, C. S.

In: Monthly Notices of the Royal Astronomical Society, Vol. 483, No. 3, 01.01.2019, p. 3382-3389.

Research output: Contribution to journalArticle

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T1 - Intra-night optical variability of misaligned active galaxies

AU - Bhattacharya, Debbijoy

AU - Gulati, Sanna

AU - Stalin, C. S.

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