3C 345

3C 345
Image of 3C 345 by the Hubble Space Telescope
Observation data (Epoch J2000)
ConstellationHercules
Right ascension16h 42m 58.8s[1]
Declination+39° 48′ 37″[1]
Redshift0.5934 [1]
Distance5.497 Gly
TypeOpt.var.;HPQ, FSRQ
Apparent magnitude (V)16.6[1]
Notable featuressuperluminal jet
Other designations
4C +39.48, LEDA 084767[1]
See also: Quasar, List of quasars
Total intensity image of the inner region of 3C 345 at 1.6 GHz[2]

3C 345 is a blazar/flat spectrum radio quasar located in the constellation of Hercules. It is noted for hosting a superluminal jet[3] and its variability in almost all wave bands.

Characteristics

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3C 345 has an active galactic nucleus that has been categorised as a blazar or as a flat spectrum radio quasar. The host galaxy of 3C 345 is an E3 elliptical galaxy without prominent peculiar characteristics.[4]

Superluminal jet

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When observed in radio waves, 3C 345 features a compact region with a radio jet emanating from it for 3 arcseconds and ending at a hot spot.[3] The jet appears straight for 4 milliarcseconds (mas)[3] but then curves northwards. Hot spots are visible at the counterjet direction in radio images.[5] There is also a faint halo.[3] The jet has been found to emit X-rays, up until 0.2 arcseconds from a radio hot spot, which could be in reality a bend of the jet.[5]

The components of the jet have been found to move by about 0.25–0.42 mas, which at the distance of the jet represent apparent speeds that are 5 to 15 times faster than the speed of light.[6] The radio jet exhibits superluminal motion for 0.12 to 12 mas, with apparent speeds that accelerate from ~5c to ~15c within 0.3 mas. Within the jet lies a stationary feature ~0.1 mas (with corresponds to about 0.7 pc at the distance of 3C 345) from the core, which has also been found in other blazars.[6] The viewing angle between the jet axis and the line of sight is calculated to be about 5°.[6]

Variability

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3C 345 has been known to fluctuate in brightness. For example, it brightened from magnitude 17.2 to 16.0 between 10 April 2018 and 8 May 2018 when observed in R band.[7] A bright GeV gamma-ray flare was observed by the Fermi Gamma-ray Space Telescope on 31 May 2017, as the flux increased by 40 times above average.[8] The flares in 2009 were observed simultaneously in γ-rays, X-rays and optical/UV, while there was a lag before they were observed in radiowaves.[9] A long term variability study indicates flares every 3.5 to 4 years, coinciding with the appearance of new features in the radio jets.[10]

It has been suggested that the source of the fluctuation is the presence of a binary supermassive black hole, with the two similar black holes with masses about 7.1×108 M☉ which are separated by around 0.33 pc and orbit each other with a period of 480 years. The second black hole perturbates the accretion disk, resulting to fluctuations in activity.[11] The X-rays observations indicate that the nuclear region is hidden behind a compton thick absorber with a column density of NH ≃ 1025 cm−2 that covers 75% to 85% of the X-rays source.[12]

References

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  1. ^ a b c d e "NASA/IPAC Extragalactic Database". Results for 3C 345. Retrieved 2023-06-29.
  2. ^ Pötzl, F. M.; Lobanov, A. P.; Ros, E.; Gómez, J. L.; Bruni, G.; Bach, U.; Fuentes, A.; Gurvits, L. I.; Jauncey, D. L.; Kovalev, Y. Y.; Kravchenko, E. V.; Lisakov, M. M.; Savolainen, T.; Sokolovsky, K. V.; Zensus, J. A. (April 2021). "Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron: IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature". Astronomy & Astrophysics. 648: A82. arXiv:2102.04441. Bibcode:2021A&A...648A..82P. doi:10.1051/0004-6361/202039493.
  3. ^ a b c d Zensus, J. A.; Cohen, M. H.; Unwin, S. C. (April 1995). "The Parsec-scale jet in quasar 3C 345". The Astrophysical Journal. 443: 35. Bibcode:1995ApJ...443...35Z. doi:10.1086/175501.
  4. ^ Kirhakos, Sofia; Bahcall, John N.; Schneider, Donald P.; Kristian, Jerome (20 July 1999). "The Host Galaxies of Three Radio-loud Quasars: 3C 48, 3C 345, and B2 1425+267". The Astrophysical Journal. 520 (1): 67–77. arXiv:astro-ph/9902175. Bibcode:1999ApJ...520...67K. doi:10.1086/307430. S2CID 14788813.
  5. ^ a b Kharb, P.; Lister, M. L.; Marshall, H. L.; Hogan, B. S. (1 April 2012). "Chandra and HST imaging of the Quasars PKS B0106+013 and 3C 345: Inverse Compton X-Rays and Magnetized Jets". The Astrophysical Journal. 748 (2): 81. arXiv:1201.4178. Bibcode:2012ApJ...748...81K. doi:10.1088/0004-637X/748/2/81. hdl:1721.1/95505. S2CID 54031860.
  6. ^ a b c Schinzel, F. K.; Lobanov, A. P.; Taylor, G. B.; Jorstad, S. G.; Marscher, A. P.; Zensus, J. A. (January 2012). "Relativistic outflow drives γ -ray emission in 3C 345". Astronomy & Astrophysics. 537: A70. arXiv:1111.2045. Bibcode:2012A&A...537A..70S. doi:10.1051/0004-6361/201117705. S2CID 119293038.
  7. ^ "ATel #11624: Bright optical outbursts of the FSRQ Ton 599 and 3C 345". The Astronomer's Telegram. 9 May 2018. Retrieved 29 June 2023.
  8. ^ "ATel #10453: Fermi LAT detection of a bright GeV gamma-ray flare from the FSRQ 3C 345". The Astronomer's Telegram. 2 June 2017. Retrieved 29 June 2023.
  9. ^ Berton, M.; Liao, N. H.; La Mura, G.; Järvelä, E.; Congiu, E.; Foschini, L.; Frezzato, M.; Ramakrishnan, V.; Fan, X. L.; Lähteenmäki, A.; Pursimo, T.; Abate, V.; Bai, J. M.; Calcidese, P.; Ciroi, S.; Chen, L.; Cracco, V.; Li, S. K.; Tornikoski, M.; Rafanelli, P. (June 2018). "The flat-spectrum radio quasar 3C 345 from the high to the low emission state". Astronomy & Astrophysics. 614: A148. arXiv:1707.07681. Bibcode:2018A&A...614A.148B. doi:10.1051/0004-6361/201731625. S2CID 85509432.
  10. ^ Lobanov, Andrew P.; Zensus, J. Anton (20 August 1999). "Spectral Evolution of the Parsec-Scale Jet in the Quasar 3C 345". The Astrophysical Journal. 521 (2): 509–525. arXiv:astro-ph/9903318. Bibcode:1999ApJ...521..509L. doi:10.1086/307555. S2CID 119093726.
  11. ^ Lobanov, A. P.; Roland, J. (March 2005). "A supermassive binary black hole in the quasar 3C 345". Astronomy & Astrophysics. 431 (3): 831–846. arXiv:astro-ph/0411417. Bibcode:2005A&A...431..831L. doi:10.1051/0004-6361:20041831. S2CID 12635549.
  12. ^ Eguchi, Satoshi (July 2017). "Compton thick absorber in type 1 quasar 3C 345 revealed by Suzaku and Swift/BAT". Monthly Notices of the Royal Astronomical Society. 468 (4): 4529–4538. arXiv:1703.08477. doi:10.1093/mnras/stx754.
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