Astronomy:3C 345
| 3C 345 | |
|---|---|
 Image of 3C 345 by the Hubble Space Telescope | |
| Observation data (Epoch J2000) | |
| Constellation | Hercules |
| Right ascension | 16h 42m 58.8s[1] |
| Declination | +39° 48′ 37″[1] |
| Redshift | 0.5934 [1] |
| Distance | 5.497 Gly |
| Type | Opt.var.;HPQ, FSRQ |
| Apparent magnitude (V) | 16.6[1] |
| Notable features | superluminal jet |
| Other designations | |
| 4C +39.48, LEDA 084767[1] | |
| See also: Quasar,List of quasars]] | |
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
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
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
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 pertubates 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
- ↑ 1.0 1.1 1.2 1.3 1.4 "NASA/IPAC Extragalactic Database". Results for 3C 345. https://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=3C+345&extend=no.
- ↑ Pötzl, F. M.; Lobanov, A. P.; Ros, E.; Gómez, J. L.; Bruni, G.; Bach, U.; Fuentes, A.; Gurvits, L. I. et al. (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. doi:10.1051/0004-6361/202039493.
- ↑ 3.0 3.1 3.2 3.3 Zensus, J. A.; Cohen, M. H.; Unwin, S. C. (April 1995). "The Parsec-scale jet in quasar 3C 345". The Astrophysical Journal 443: 35. doi:10.1086/175501. https://articles.adsabs.harvard.edu/pdf/1995ApJ...443...35Z.
- ↑ 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. doi:10.1086/307430.
- ↑ 5.0 5.1 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. doi:10.1088/0004-637X/748/2/81.
- ↑ 6.0 6.1 6.2 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. doi:10.1051/0004-6361/201117705.
- ↑ "ATel #11624: Bright optical outbursts of the FSRQ Ton 599 and 3C 345". 9 May 2018. https://www.astronomerstelegram.org/?read=11624.
- ↑ "ATel #10453: Fermi LAT detection of a bright GeV gamma-ray flare from the FSRQ 3C 345". 2 June 2017. https://www.astronomerstelegram.org/?read=10453.
- ↑ Berton, M.; Liao, N. H.; La Mura, G.; Järvelä, E.; Congiu, E.; Foschini, L.; Frezzato, M.; Ramakrishnan, V. et al. (June 2018). "The flat-spectrum radio quasar 3C 345 from the high to the low emission state". Astronomy & Astrophysics 614: A148. doi:10.1051/0004-6361/201731625.
- ↑ 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. doi:10.1086/307555.
- ↑ Lobanov, A. P.; Roland, J. (March 2005). "A supermassive binary black hole in the quasar 3C 345". Astronomy & Astrophysics 431 (3): 831–846. doi:10.1051/0004-6361:20041831. https://www.aanda.org/10.1051/0004-6361:20041831/pdf.
- ↑ 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. doi:10.1093/mnras/stx754.
External links
- 3C 345 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- 3C 345 on SIMBAD
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