{{Short description|Quasar located in the constellation of Coma Berenices}} {{Infobox galaxy|name=[[Parkes Catalogue of Radio Sources|PKS]] 1222+216|epoch=[[J2000.0]]|constellation name=[[Coma Berenices]]|ra={{RA|12|24|54.45}}<ref name="ned" />|dec={{DEC|+21|22|46.38}}<ref name="ned" />|z=0.433826<ref name="ned" />|h_radial_v=130,058 [[kilometer per second|km/s]]<ref name="ned" />|dist_ly=4.695 [[light years|Gly]]|appmag_v=17.50|type=Blazar LPQ<ref name="ned" />|size=~{{convert|104.2|kpc|ly|abbr=on|lk=on|order=flip}} (estimated){{r|ned}}|notes=VHE emitter, [[blazar]]|names=[[Fourth Cambridge Survey|4C]] 21.35, [[2MASS]] J12245446+2122463, [[Lyon-Meudon Extragalactic Database|LEDA]] 2819691, [[Seventh Cambridge Survey|7C]] 1222+2139, [[Sloan Digital Sky Survey|SDSS]] J122454.45+212246.3, ON +238, CoNFIG 134, [[ROSAT|RX]] J1224.9+2122, TeV J1224+213, [[International Celestial Reference Frame|ICRF]] J122454.4+212246, 2PBC J1224.8+2122<ref name="ned" />|image=File:Image of PKS 1222+216.png|caption=[[Sloan Digital Sky Survey|SDSS]] image of PKS 1222+216. The galaxy on the bottom left of the image is the spiral galaxy, PGC 40438.}}
'''PKS 1222+216''' also known as '''4C 21.35''', is a [[quasar]] located in the constellation of [[Coma Berenices]]. The [[redshift]] of the object is (z) 0.433, estimating the object to be located 4.6 billion [[light-year]]s from Earth<ref name="ned">{{Cite web |title=NED Search results for PKS 1222+216 |url=https://ned.ipac.caltech.edu/byname?objname=PKS+1222+216&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 |access-date=2025-09-06 |website=NASA/IPAC Extragalactic Database}}</ref> and it was first discovered by astronomers in 1966 as a [[Astronomical radio source|radio source]].<ref>{{Cite journal |last1=Long |first1=R. J. |last2=Smith |first2=M. A. |last3=Stewart |first3=P. |last4=Williams |first4=P. J. S. |date=1966-12-01 |title=The Radio Spectra of Sources in the Fourth Cambridge Catalogue |url=https://watermark02.silverchair.com/mnras134-0371.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAA14wggNaBgkqhkiG9w0BBwagggNLMIIDRwIBADCCA0AGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMjebUC-1x8gumFRtyAgEQgIIDEdYz3L2dvjHXfGYTWYlYRwHiu4DrP4FnRsqG0nM89hC3NxDbDxqMNepDmUgtXrn-uj5LTL1NcRWSmDzkF73390r9ksFYQQVqhyGq7TZL0yc-aricGLPc_PDxg04Mcq8gfrK3R_xLszceeCX34U91VKYJY_SlCsTHBcwe4EC5sqkzxeEPrzdJVUTzGKvq4pfP0DnvY0liMagsi_bLEWVbNhAfU2i9nhg0nSN5104RHdQXALqgvaUli2reYgzwCULLqQN-s4tKXkI59-XVt5eGRAS06KpSALtoknOhB36CciKu5hl-9pZHTCcGTC951kDeSH7PIt80dpSckg1ML4BPAMV52aS-LO804lMim_NDlnouEPKHcuo9MqWXs6YiU3LdkimqWBQniK9uAJ8XKgQndHIzB1auQT-TCxmg7dSZCA5le4VN9n6glvjl1yRDz4GraegtHIZcR3MP3dz8RiH964mgtE75iNkrYsrCB9TuJXlEbrZIsCdfyKMPXp87mQtIvQ9pTAvVS4vRivMWGAF4lvEwPJWK4aeqzYLw1HqAu2Z0v3oAh1BSkKGa6bP8yeN76bTMaPX5Bya0l1U33EWvr2nRVp-CHhQMXSMuB8bcfl5dVsNELlTk27ndJMgb7IJjCFkfudyZgfn6_4sKmd1kncmffNonVoz1XfTazZ6FE3dzXRUKg_2qoJkijgD7YShEpM2-AwDQtZrtxJd3LkkaXziWoy8KzWZcCRo9VfK-dX7jrUY_qzPXcLWgSjbuC-9kgOJZxWv4_FcYLVJiN4re4_DLh3IIbLoMFM6zOyUzs0_InR6-czF-TA-r46cHT5PyUv8t87DW37Im31nBPQL83Sz39lYqwKXXirtiZtdxrGmr6QoktGxF2hH40SUzI2viZRxR6AYZwulEHXVxh6adSwoLH-TvByeO_UmoNJ0n_jwA9AD4L49bHr1QcyqvQirQ2fIkfjgBWE_mN3yurQyKvR9KB7WcFfo9wncVst8rAOMnBTGiK3PU2lArWUOWvJtuxpWyJRaGednuDCQMM5QC0P-L |journal=Monthly Notices of the Royal Astronomical Society |volume=134 |issue=4 |pages=371–388 |doi=10.1093/mnras/134.4.371 |doi-access=free | bibcode=1966MNRAS.134..371L |issn=0035-8711}}</ref> The [[radio spectrum]] of PKS 1222+216 is considered as flat, thus the classification of it being a [[flat-spectrum radio quasar]].<ref>{{Cite journal |last1=Tavecchio |first1=F. |last2=Becerra-Gonzalez |first2=J. |last3=Ghisellini |first3=G. |last4=Stamerra |first4=A. |last5=Bonnoli |first5=G. |last6=Foschini |first6=L. |last7=Maraschi |first7=L. |date=2011-10-01 |title=On the origin of the γ-ray emission from the flaring blazar PKS 1222+216 |url=https://www.aanda.org/articles/aa/abs/2011/10/aa17204-11/aa17204-11.html |journal=Astronomy & Astrophysics |language=en |volume=534 |pages=A86 |doi=10.1051/0004-6361/201117204 |arxiv=1104.0048 |bibcode=2011A&A...534A..86T |issn=0004-6361}}</ref><ref>{{Cite web |title=ATel #5921: Quasar PKS 1222+21 in outburst |url=https://www.astronomerstelegram.org/?read=5921 |access-date=2025-09-07 |website=The Astronomer's Telegram}}</ref>
== Description ==
=== Flaring activity === PKS 1222+216 is a [[blazar]], mainly being optically violently variable on the [[electromagnetic spectrum]] and also described as a [[Very-high-energy gamma ray|very high energy]] emitter.<ref>{{Cite web |title=ATel #5981: Detection of Persistent VHE emission from PKS 1222+216 (4C +21.35) with VERITAS |url=https://www.astronomerstelegram.org/?read=5981 |access-date=2025-09-07 |website=The Astronomer's Telegram}}</ref><ref>{{Cite journal |last1=Nalewajko |first1=Krzysztof |last2=Begelman |first2=Mitchell C. |last3=Cerutti |first3=Benoît |last4=Uzdensky |first4=Dmitri A. |last5=Sikora |first5=Marek |date=October 2012 |title=Energetic constraints on a rapid gamma-ray flare in PKS 1222+216 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=425 |issue=4 |pages=2519–2529 |doi=10.1111/j.1365-2966.2012.21721.x |bibcode=2012MNRAS.425.2519N |doi-access=free |issn=0035-8711|arxiv=1202.2123 }}</ref><ref>{{Cite web |last1=Nowakowski |first1=Tomasz |last2=Phys.org |title=Astronomers investigate jet kinematics of the blazar 4C+21.35 |url=https://phys.org/news/2019-04-astronomers-jet-kinematics-blazar-4c2135.html |access-date=2025-09-07 |website=phys.org |language=en}}</ref> When first observed in April 2009 it was shown to be in an active phase, with an increasing amount of gamma-ray flux reaching around 4.6 ± 1.6 × 10<sup>−7</sup> photons cm<sup>−2</sup> s<sup>−1</sup>.<ref>{{Cite web |title=ATel #2021: Fermi LAT detection of increasing gamma-ray activity of blazar PKS 1222+216 |url=https://www.astronomerstelegram.org/?read=2021 |access-date=2025-09-06 |website=The Astronomer's Telegram}}</ref> By December 15, 2009, the source's flux had reached 3.4 ± 0.5 × 10<sup>−6</sup> photons cm<sup>−2</sup> s<sup>−1</sup>, marking this as an increase by a factor of 40.<ref>{{Cite web |title=ATel #2349: Fermi LAT confirmation of a strong GeV flare from 4C 21.35 (PKS 1222+21) |url=https://www.astronomerstelegram.org/?read=2349 |access-date=2025-09-06 |website=The Astronomer's Telegram}}</ref>
Two powerful [[Gamma ray|gamma-ray]] flares were detected from PKS 1222+216 by various observations in April and June 2010.<ref>{{Cite journal |last1=Striani |first1=E. |last2=Verrecchia |first2=F. |last3=Donnarumma |first3=I. |last4=Vercellone |first4=S. |last5=Tavani |first5=M. |last6=Bulgarelli |first6=A. |last7=Gianotti |first7=F. |last8=Trifoglio |first8=M. |last9=Chen |first9=A. |last10=Giuliani |first10=A. |last11=Mereghetti |first11=S. |last12=Caraveo |first12=P. |last13=Perotti |first13=F. |last14=D'Ammando |first14=F. |last15=Del Monte |first15=E. |date=June 2010 |title=AGILE detection of a gamma-ray flare from the blazar 4C+21.35 (PKS 1222+21) |url=https://ui.adsabs.harvard.edu/abs/2010ATel.2686....1S/abstract |journal=The Astronomer's Telegram |language=en |volume=2686 |pages=1 |bibcode=2010ATel.2686....1S }}</ref><ref name=":0">{{Cite journal |last1=Tanaka |first1=Y. T. |last2=Stawarz |first2=Ł |last3=Thompson |first3=D. J. |last4=D'Ammando |first4=F. |last5=Fegan |first5=S. J. |last6=Lott |first6=B. |last7=Wood |first7=D. L. |last8=Cheung |first8=C. C. |last9=Finke |first9=J. |last10=Buson |first10=S. |last11=Escande |first11=L. |last12=Saito |first12=S. |last13=Ohno |first13=M. |last14=Takahashi |first14=T. |last15=Donato |first15=D. |date=May 2011 |title=Fermi Large Area Telescope Detection of Bright γ-Ray Outbursts from the Peculiar Quasar 4C +21.35 |url=https://ui.adsabs.harvard.edu/abs/2011ApJ...733...19T/abstract |journal=The Astrophysical Journal |language=en |volume=733 |issue=1 |pages=19 |doi=10.1088/0004-637X/733/1/19 |bibcode=2011ApJ...733...19T |issn=0004-637X|arxiv=1101.5339 }}</ref><ref>{{Cite journal |last1=Kushwaha |first1=Pankaj |last2=Singh |first2=K. P. |last3=Sahayanathan |first3=Sunder |date=2014-11-05 |title=BRIGHTEST''Fermi''-LAT FLARES OF PKS 1222+216: IMPLICATIONS ON EMISSION AND ACCELERATION PROCESSES |url=https://doi.org/10.1088/0004-637x/796/1/61 |journal=The Astrophysical Journal |volume=796 |issue=1 |pages=61 |doi=10.1088/0004-637x/796/1/61 |arxiv=1409.8201 |bibcode=2014ApJ...796...61K |issn=1538-4357}}</ref> The object displayed a broken [[Power law|power-law]] form with observed spectra breaks near the ranges between 1 and 3 GeV [[photon]]s.<ref name=":0" /> The optical polarimetric observations also noted the variability of the source in both [[Polarization (waves)|polarization]] and position angle, with a detected decrease in [[brightness]] levels of 0.34 [[Magnitude (astronomy)|magnitude]] between 19 and 22 June in [[V band]].<ref>{{Cite web |title=ATel #2693: Optical polarimetric observations of 4C +21.35 (PKS 1222+21) during the gamma-ray flare |url=https://www.astronomerstelegram.org/?read=2693 |access-date=2025-09-06 |website=The Astronomer's Telegram}}</ref> Following the flare of April 2010, the source exhibited an immense increase in [[Infrared|near-infrared]] flux.<ref>{{Cite web |title=ATel #2626: NIR Flaring of PKS1222+216 |url=https://www.astronomerstelegram.org/?read=2626 |access-date=2025-09-06 |website=The Astronomer's Telegram}}</ref>
In 2014 PKS 1222+216 underwent several more flaring periods. When detected, both flares (Flare A and Flare B) were shown to be accompanied by two subflares, occurring within a time span of three days. The subflare of Flare A displayed a slow rising trend, reaching a [[Maximum and minimum|maximum]] at MJD (56699 ± 0.5), subsequently followed by a rapid decrease. Subflare 2 of Flare A, displayed an increase to its maximum peak, before displaying a slow [[Rise time|decay time]]. The [[flux]] for Flare A has been estimated as 3.2 ± 0.42 × 10<sup>−6</sup> photon cm<sup>−2</sup> s<sup>−1</sup>. The subflares of Flare B on the other hand, showed a rapid [[rise time]], subsequently followed by a slow decay time lasting 0.6 days.<ref>{{Cite journal |last1=Chatterjee |first1=Anshu |last2=Roy |first2=Abhradeep |last3=Sarkar |first3=Arkadipta |last4=Chitnis |first4=Varsha R |date=2021-12-01 |title=Temporal and spectral study of PKS B1222 + 216 flares in 2014 |journal=Monthly Notices of the Royal Astronomical Society |volume=508 |issue=2 |pages=1986–2001 |doi=10.1093/mnras/stab2747 |doi-access=free |issn=0035-8711|arxiv=2105.10891 }}</ref>
=== Radio Source === The structure of the source of PKS 1222+216, is compact and highly distorted with an angular extent of 17 arcseconds.<ref>{{Cite journal |last1=Hooimeyer |first1=J. R. A. |last2=Schilizzi |first2=R. T. |last3=Miley |first3=G. K. |last4=Barthel |first4=P. D. |date=July 1992 |title=Two new candidate superluminal quasars : 4C 28.45 and 4C 21.35. |url=https://articles.adsabs.harvard.edu/full/1992A%26A...261....5H |journal=Astronomy and Astrophysics |language=en |volume=261 |pages=5–8 |bibcode=1992A&A...261....5H |issn=0004-6361}}</ref> When imaged with the [[Very Large Array]] (VLA) on kiloparsec scales, it has a bright radio core surrounded by [[Radio wave|radio emission]] that is 100 [[Parsec|kiloparsecs]] in extent.<ref name=":1">{{Cite journal |last1=Ackermann |first1=M. |last2=Ajello |first2=M. |last3=Allafort |first3=A. |last4=Antolini |first4=E. |last5=Barbiellini |first5=G. |last6=Bastieri |first6=D. |last7=Bellazzini |first7=R. |last8=Bissaldi |first8=E. |last9=Bonamente |first9=E. |last10=Bregeon |first10=J. |last11=Brigida |first11=M. |last12=Bruel |first12=P. |last13=Buehler |first13=R. |last14=Buson |first14=S. |last15=Caliandro |first15=G. A. |date=2014-04-25 |title=Multifrequency Studies of the Peculiar Quasar 4C +21.35 During the 2010 Flaring Activity |url=https://iopscience.iop.org/article/10.1088/0004-637X/786/2/157 |journal=The Astrophysical Journal |volume=786 |issue=2 |pages=157 |doi=10.1088/0004-637x/786/2/157 |arxiv=1403.7534 |bibcode=2014ApJ...786..157A |hdl=10550/59461 |issn=0004-637X}}</ref> A secondary component is seen extending 12 arcseconds from the core.<ref>{{Cite journal |last1=Price |first1=Rob |last2=Gower |first2=Ann C. |last3=Hutchings |first3=J. B. |last4=Talon |first4=S. |last5=Duncan |first5=D. |last6=Ross |first6=G. |date=June 1993 |title=VLA Observations of 91 Quasars at 0.35 < Z < 1 |url=https://articles.adsabs.harvard.edu/pdf/1993ApJS...86..365P |journal=The Astrophysical Journal Supplement Series |language=en |volume=86 |pages=365 |doi=10.1086/191783 |bibcode=1993ApJS...86..365P |issn=0067-0049}}</ref><ref>{{Cite journal |last1=Jorstad |first1=Svetlana G. |last2=Marscher |first2=Alan P. |last3=Mattox |first3=John R. |last4=Aller |first4=Margo F. |last5=Aller |first5=Hugh D. |last6=Wehrle |first6=Ann E. |last7=Bloom |first7=Steven D. |date=August 2001 |title=Multiepoch Very Long Baseline Array Observations of EGRET-detected Quasars and BL Lacertae Objects: Connection between Superluminal Ejections and Gamma-Ray Flares in Blazars |journal=The Astrophysical Journal |language=en |volume=556 |issue=2 |pages=738–748 |doi=10.1086/321605 |arxiv=astro-ph/0101570 |bibcode=2001ApJ...556..738J |issn=0004-637X}}</ref> There is a [[Astrophysical jet|jet]] present in the source, originating in the northeast before abruptly bending eastwards and ending in a hotspot located 60 kiloparsecs from the core.<ref name=":1" /><ref>{{Cite journal |last1=Saikia |first1=D. J. |last2=Wiita |first2=Paul J. |last3=Muxlow |first3=T. W. B. |date=May 1993 |title=1222+216: A Wide-Angle-Tailed Quasar? |url=https://articles.adsabs.harvard.edu/pdf/1993AJ....105.1658S |journal=The Astronomical Journal |language=en |volume=105 |pages=1658 |doi=10.1086/116544 |bibcode=1993AJ....105.1658S |issn=0004-6256}}</ref> This jet is also [[Faster-than-light|superluminal]], with at least five jet knots moving at fast speeds between the ranges of 9c and 22c. Observations also found two of these knots were shown ejecting during quasar flaring periods.<ref>{{Cite journal |last1=Troitskiy |first1=Ivan |last2=Morozova |first2=Daria |last3=Jorstad |first3=Svetlana |last4=Larionov |first4=Valery |last5=Marscher |first5=Alan |last6=Agudo |first6=Ivan |last7=Blinov |first7=Dmitry |last8=Smith |first8=Paul |last9=Troitskaya |first9=Yuliya |date=2016-11-28 |title=Multi-Frequency Monitoring of the Flat Spectrum Radio Quasar PKS 1222+216 in 2008–2015 |journal=Galaxies |volume=4 |issue=4 |pages=72 |doi=10.3390/galaxies4040072 |bibcode=2016Galax...4...72T |doi-access=free |issn=2075-4434|hdl=10261/394324 |hdl-access=free }}</ref>
== Quasi-periodic oscillation and supermassive black hole mass == In 2022, PKS 1222+216 was shown undergoing a [[Quasi-periodic oscillation (astronomy)|quasi-periodic oscillation]] with a period of around 420 days based on optical [[Photometric system|photometric]] and [[Polarimetry|polarimetric]] data observations conducted for 10 years. This is explained by a blob feature moving in [[Magnetic helicity|helical motion]] inside a jet.<ref>{{Cite journal |last1=Zhang |first1=Pengfei |last2=Wang |first2=Zhongxiang |date=2022-07-01 |title=Polarized Optical Emission of the Blazar PKS 1222+216: Discovery of a 420 day Quasiperiodic Signal |journal=The Astrophysical Journal |volume=934 |issue=1 |pages=3 |doi=10.3847/1538-4357/ac778f |arxiv=2207.10824 |bibcode=2022ApJ...934....3Z |doi-access=free |issn=0004-637X}}</ref> The central [[supermassive black hole]] mass for the quasar has been estimated as 6 × 10<sup>8</sup> [[Solar mass|M<sub>☉</sub>]] based on a virial method of its broad [[Spectral line|emission lines]].<ref>{{Cite journal |last1=Farina |first1=E. P. |last2=Decarli |first2=R. |last3=Falomo |first3=R. |last4=Treves |first4=A. |last5=Raiteri |first5=C. M. |date=2012-06-01 |title=The optical spectrum of PKS 1222+216 and its black hole mass |journal=Monthly Notices of the Royal Astronomical Society |volume=424 |issue=1 |pages=393–398 |doi=10.1111/j.1365-2966.2012.21209.x |arxiv=1205.0021 |bibcode=2012MNRAS.424..393F |doi-access=free |issn=0035-8711}}</ref><ref>{{Cite journal |last1=Lei |first1=Maichang |last2=Wang |first2=Jiancheng |date=2015-07-02 |title=Location of gamma-ray flaring region in quasar 4C +21.35 |url=https://doi.org/10.1093/pasj/psv055 |journal=Publications of the Astronomical Society of Japan |volume=67 |issue=4 |article-number=79 |doi=10.1093/pasj/psv055 |issn=2053-051X|arxiv=1505.08056 }}</ref>
== References == <references /> {{Coma Berenices}}
[[Category:Quasars]] [[Category:Coma Berenices]] [[Category:Blazars]] [[Category:Active galaxies]] [[Category:OVV quasars]] [[Category:4C objects|21.35]] [[Category:LEDA objects|2819691]] [[Category:SDSS objects]] [[Category:ROSAT objects]] [[Category:Astronomical objects discovered in 1966]]