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AO 0235+164
The BL Lac object AO 0235+164
Observation data (J2000.0 epoch)
Constellation	Aries
Right ascension	02 38 38.930
Declination	+16° 36′ 59.275″
Redshift	0.940000
Heliocentric radial velocity	281,805 km/s
Distance	7.537 Gly
Apparent magnitude (V)	15.5
Apparent magnitude (B)	16.46
Characteristics
Type	blazar;FRSQ, BL Lac
Notable features	Optical variable blazar
Other designations
LEDA 2823185, PKS 0235+164, NVSS J023838+163658, 4FGL J0238.6+1637, OD +160

AO 0235+164 is a BL Lacertae object (BL Lac object) located in the constellation of Aries, 7.5 billion light years from Earth. It has a redshift of 0.94. It was first discovered as an astronomical radio source by astronomers between 1967 and 1970, and formally identified with a red stellar object in 1975. Because of its extreme variability at both radio and optical wavelengths across the electromagnetic spectrum, this BL Lac object has been referred to as a blazar.

Description

AO 0235+164 is shown to be in a flaring state. It also had two major outbursts in 1975 and 1987. Another outburst occurred in 1997 the duration of which was on the order of 800 days with a maximum luminosity of 9.86 x 10 erg s suggesting a microlensing event scenario.

During a Fermi Large Area Telescope multi-wavelength observation between August 2008 and February 2009, the blazar underwent a high state showing intense gamma ray activity before falling to a low state. It displayed near-infrared flares in 2014 and 2017. By 2020, AO 0235+164 had brightened again, displaying an optical flare that reached its peak in 2021. However, when compared to previous flares, it is shown weaker despite emission at all wavelengths increasing from gamma rays to millimeter waves and its light curve exhibiting a multi-peak structure with sharp variability at high energies.

The optical brightness of AO 0235+164 is known to vary across different time scales ranging from a few hours in optical to a long period of time in radio. During the last three nights in January 2024, its brightness level significantly increased rapidly over 2 magnitudes in the R-band.

The source of AO 0235+164 is substantially resolved, however no structural position angle is distinguished . Additionally AO 0235+165 also contains a compact core with a weak extended structure located north-northwest from it, indicating a result of a small viewing angle found for the source. A component can be seen 0.7 mas away from the core with a position angle of = 7°. The radio components also have superluminal velocities reaching as fast as β ~ 30h (h = H/100 km Mpc s).

AO 0235+164 contains a supermassive black hole in its center. Based on analysis of a broad magnesium spectral line in its spectrum, the mass is 7.9 x 10 M_ʘ. Alternatively, it might also contain a close binary black hole system with estimated similar masses of order of 10 M_ʘ with velocities of 10 and 5 x 10 kilometers per seconds.

References

1. Snijders, M. A. J.; Boksenberg, A.; Penston, M. V.; Sargent, W. L. W. (1982-12-01). "IUE observations of the BL Lac object AO 0235 + 164". Monthly Notices of the Royal Astronomical Society. 201 (3): 801–805. doi:10.1093/mnras/201.3.801. ISSN 0035-8711.
2. Pedrosa, J. Escudero; Agudo, I.; Tramacere, A.; Marscher, A. P.; Jorstad, S.; Weaver, Z. R.; Casadio, C.; Thum, C.; Myserlis, I.; Fuentes, A.; Traianou, E.; Kim, J.-Y.; Kramer, J.; López-Coto, R.; D’Ammando, F. (2024-02-01). "Repeating flaring activity of the blazar AO 0235+164". Astronomy & Astrophysics. 682: A100. arXiv:2311.01157. Bibcode:2024A&A...682A.100E. doi:10.1051/0004-6361/202346885. ISSN 0004-6361.
3. "AO 0235+164 - Frankfurt Quasar Monitoring". quasar.square7.ch. Retrieved 2024-10-23.
4. Spinrad, H.; Smith, H. E. (1975-10-01). "AO 0235+164 a red BL Lacertae object". The Astrophysical Journal. 201: 275–276. Bibcode:1975ApJ...201..275S. doi:10.1086/153883. ISSN 0004-637X.
5. Kutkin, A. M.; Pashchenko, I. N.; Lisakov, M. M.; Voytsik, P. A.; Sokolovsky, K. V.; Kovalev, Y. Y.; Lobanov, A. P.; Ipatov, A. V.; Aller, M. F.; Aller, H. D.; Lahteenmaki, A.; Tornikoski, M.; Gurvits, L. I. (2018-04-21). "The extreme blazar AO 0235+164 as seen by extensive ground and space radio observations". Monthly Notices of the Royal Astronomical Society. 475 (4): 4994–5009. arXiv:1801.04892. doi:10.1093/mnras/sty144. ISSN 0035-8711.
6. Bychkova, V. S.; Vol’vach, A. E.; Kardashev, N. S.; Larionov, M. G.; Vlasyuk, V. V.; Spiridonova, O. I.; Vol’vach, L. N.; Lähteenmäki, A.; Tornikoski, M.; Aller, M. F.; Aller, H. D. (September 2015). "Long-term monitoring of the blazars AO 0235+164 and S5 0716+714 in the optical and radio ranges". Astronomy Reports. 59 (9): 851–864. Bibcode:2015ARep...59..851B. doi:10.1134/s1063772915080016. ISSN 1063-7729.
7. Raiteri, C. M.; Villata, M.; Kadler, M.; Ibrahimov, M. A.; Kurtanidze, O. M.; Larionov, V. M. (December 2006). "Multifrequency variability of the blazar AO 0235+164. The WEBT campaign in 2004-2005 and long-term SED analysis". Astronomy & Astrophysics. 459 (3): 731–743. arXiv:astro-ph/0608627. doi:10.1051/0004-6361:20065744. ISSN 0004-6361.
8. Mihov, Boyko; Slavcheva-Mihova, Lyuba (2023-09-01). "High-activity state of the blazar AO 0235+164". The Astronomer's Telegram. 16253: 1. Bibcode:2023ATel16253....1M.
9. Vince, Oliver; Damljanovic, Goran; Gupta, Alok C. (2023-08-01). "The blazar AO 0235+164 is brightening in Optical bands". The Astronomer's Telegram. 16204: 1. Bibcode:2023ATel16204....1V.
10. Chen, Y. J.; Jiang, D. R. (September 2001). "The spectral energy distribution of AO 0235+164 during two active optical phases" (PDF). Astronomy & Astrophysics. 376 (1): 69–76. Bibcode:2001A&A...376...69C. doi:10.1051/0004-6361:20010921. ISSN 0004-6361.
11. Webb, James R.; Howard, Emily; Benítez, Erika; Balonek, Tom; McGrath, Elizabeth; Shrader, Chris; Robson, Ian; Jenkins, Pamela (July 2000). "The 1997 Outburst of AO 0235+164: Evidence for a Microlensing Event?". The Astronomical Journal. 120 (1): 41–46. Bibcode:2000AJ....120...41W. doi:10.1086/301432. ISSN 0004-6256.
12. Ackermann, M.; Ajello, M.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R. (May 2012). "MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008–2009 FLARING STATE". The Astronomical Journal. 751 (159): 159. arXiv:1207.2932. Bibcode:2012ApJ...751..159A. doi:10.1088/0004-637X/751/2/159.
13. Carrasco, L.; Porras, A.; Recillas, E.; Mayya, D. Y.; Chavushyan, V.; Carraminana, A. (2014-10-01). "A recent NIR Flare of the QSO PKS0235+164". The Astronomer's Telegram. 6627: 1. Bibcode:2014ATel.6627....1C.
14. Carrasco, L.; Escobedo, G.; Recillas, E.; Porras, A.; Chavushyan, V.; Mayya, D. Y. (2017-11-01). "A new NIR Flare of the Blazar PKS0235+164". The Astronomer's Telegram. 11001: 1. Bibcode:2017ATel11001....1C.
15. Pedrosa, Juan Escudero; Agudo, Iván; Moritz, Till; Marscher, Alan P.; Jorstad, Svetlana; Tramacere, Andrea; Casadio, Carolina; Thum, Clemens; Myserlis, Ioannis; Sievers, Albrecht; Otero-Santos, Jorge; Morcuende, Daniel; López-Coto, Rubén; D’Ammando, Filippo; Bonnoli, Giacomo (2024-09-01). "The flaring activity of blazar AO 0235+164 in 2021" (PDF). Astronomy & Astrophysics. 689: A56. arXiv:2405.10141. Bibcode:2024A&A...689A..56E. doi:10.1051/0004-6361/202449726. ISSN 0004-6361.
16. ^ Cheong, Whee Yeon; Lee, Sang-Sung; Kim, Sang-Hyun; Kang, Sincheol; Kim, Jae Young; Rani, Bindu; Readhead, Anthony C S; Kiehlmann, Sebastian; Lähteenmäki, Anne; Tornikoski, Merja; Tammi, Joni; Ramakrishnan, Venkatessh; Agudo, Iván; Fuentes, Antonio; Traianou, Efthalia (2023-10-25). "A near magnetic-to-kinetic energy equipartition flare from the relativistic jet in AO 0235 + 164 during 2013–2019". Monthly Notices of the Royal Astronomical Society. 527 (1): 882–894. arXiv:2310.16296. doi:10.1093/mnras/stad3250. ISSN 0035-8711.
17. Lorey, C.; Reinhart, D.; Steineke, R.; Feige, M.; Zottmann, N.; Huesam, S.; Horst, B.; Kaplan, F.; Ludwig, J.; Scherbantin, A.; Mannheim, K.; Elsaesser, D. (2024-01-01). "Rapid increase in the optical brightness of the blazar AO 0235+164". The Astronomer's Telegram. 16403: 1. Bibcode:2024ATel16403....1L.
18. Gabuzda, D. C.; Cawthorne, T. V. (2000-12-21). "VLBI polarization images of eight compact active galactic nuclei at λ = 1.3 cm". Monthly Notices of the Royal Astronomical Society. 319 (4): 1056–1066. Bibcode:2000MNRAS.319.1056G. doi:10.1046/j.1365-8711.2000.03881.x. ISSN 0035-8711.
19. Jorstad, Svetlana G.; Marscher, Alan P.; Mattox, John R.; Wehrle, Ann E.; Bloom, Steven D.; Yurchenko, Alexei V. (June 2001). "Multiepoch Very Long Baseline Array Observations of EGRET-detected Quasars and BL Lacertae Objects: Superluminal Motion of Gamma-Ray Bright Blazars". The Astrophysical Journal Supplement Series. 134 (2): 181–240. arXiv:astro-ph/0101570. Bibcode:2001ApJS..134..181J. doi:10.1086/320858. ISSN 0067-0049.
20. Wang, Hongtao (2014-02-20). "The optical periodic analysis of BL Lac object AO 0235+164". Astrophysics and Space Science. 351 (1): 281–287. Bibcode:2014Ap&SS.351..281W. doi:10.1007/s10509-014-1840-z. ISSN 0004-640X.
21. Roy, Abhradeep; Gupta, Alok C.; Chitnis, Varsha R.; Cellone, Sergio A.; Raiteri, Claudia M.; Romero, Gustavo E.; Wiita, Paul J.; Chatterjee, Anshu; Combi, Jorge A.; Liao, Mai; Sarkar, Arkadipta; Villata, Massimo (2023-02-23). "Study of Variability in Long-term Multiwavelength Optical Lightcurves of Blazar AO 0235+164". The Astrophysical Journal Supplement Series. 265 (1): 14. arXiv:2301.01944. Bibcode:2023ApJS..265...14R. doi:10.3847/1538-4365/acb059. ISSN 0067-0049.
22. Vol'vach, A. E.; Larionov, M. G.; Vol'vach, L. N.; Lähteenmäki, A.; Tornikoski, M.; Aller, M. F.; Aller, H. D.; Sasada, M. (2015-02-01). "Physical characteristics of the Blazar AO 0235+164". Astronomy Reports. 59 (2): 145–155. Bibcode:2015ARep...59..145V. doi:10.1134/S1063772914120117. ISSN 1063-7729.

External links

• AO 0235+164 at SIMBAD
• AO 0235+164 at NASA/IPAC Extragalactic Database

v t e Constellation of Aries
Aries in Chinese astronomy List of stars in Aries
Stars	Bayer α (Hamal) β (Sheratan) γ (Mesarthim) δ (Botein) ε ζ η θ ι κ λ μ ν ξ ο π ρ ρ ρ σ τ τ Flamsteed 1 4 7 10 11 14 15 16 19 20 21 23 26 27 29 30 31 33 35 36 38 39 (Lilii Borea) 40 41 (Bharani) 47 49 50 51 52 53 54 55 56 59 60 62 64 65 66 54 Cet 85 Cet Variable TZ UX VZ (16 Tri) HR 577 728 803 952 999 HD 12661 20367 Other BD+20°307 HIP 14810 HAT-P-25 Teegarden's Star WASP-11/HAT-P-10 WD 0145+234
Exoplanets α Arietis b HD 12661 b c HIP 14810 b c d Teegarden's Star b c WASP-11b/HAT-P-10b
Galaxies	NGC 677 680 691 694 695 716 765 770 772 781 803 817 820 821 871 877 900 901 903 904 918 935 938 972 990 992 1024 1134 1156 Other 1ES 0229+200 3C 79 4C +28.07 AO 0235+164 IC 167 IC 1801 PSO J0309+27 Segue 2 UGC 2140
Galaxy clusters MS 0302+17
Astronomical events GRB 060218
Category

• BL Lacertae objects
• Aries (constellation)
• Blazars
• Quasars
• Active galaxies
• LEDA objects
• Astronomical objects discovered in 1975