{{Short description|BL Lac object in the constellation Draco}} {{Infobox galaxy|name=S5 1803+784|epoch=[[J2000.0]]|constellation name=[[Draco (constellation)|Draco]]|ra={{RA|18|00|45.683}}|dec={{DEC|+78|28|04.018}}|z=0.691000|h_radial_v=207,157 [[kilometer per second|km/s]]|dist_ly=6.419 [[light year|Gly]]|appmag_v=15.90|appmag_b=16.4|type=FRSQ, BL LAC|names=[[IRAS]] 18036+7827, S5 1803+78, [[NRAO VLA Sky Survey|NVSS]] J180045+782805, WMAP 072, 4FGL J1800.6+7828, [[Sixth Cambridge Survey of Radio Sources|6C]] B180338.9+782745|image=File:Image of S5 1803+784.jpg|caption=The BL Lac object S5 1803+784.}}
'''S5 1803+784''' is a [[BL Lacertae object]]<ref>{{Cite journal |last1=Strom |first1=R. G. |last2=Biermann |first2=P. L. |date=1991-02-01 |title=1803+784 : a BL Lacertae object with remarkable radio properties. |url=https://ui.adsabs.harvard.edu/abs/1991A&A...242..313S/abstract |journal=Astronomy and Astrophysics |volume=242 |pages=313 |bibcode=1991A&A...242..313S |issn=0004-6361}}</ref> located in the far northern [[constellation]] of [[Draco (constellation)|Draco]]. It has an estimated [[redshift]] (''z'') of 0.68<ref>{{Cite journal |last1=Nesci |first1=R. |last2=Massaro |first2=E. |last3=Maesano |first3=M. |last4=Montagni |first4=F. |last5=Sclavi |first5=S. |last6=Venturi |first6=T. |last7=Dallacasa |first7=D. |last8=D'Alessio |first8=F. |date=July 2002 |title=Optical and Radio Monitoring of S5 1803+784 |url=https://iopscience.iop.org/article/10.1086/341038/pdf |journal=The Astronomical Journal |volume=124 |issue=1 |pages=53–64 |doi=10.1086/341038 |bibcode=2002AJ....124...53N |issn=0004-6256|arxiv=astro-ph/0204365 }}</ref> and was first discovered as an [[astronomical radio source]] in 1981 by a team of [[astronomer]]s.<ref>{{Cite journal |last1=Biermann |first1=P. |last2=Duerbeck |first2=H. |last3=Eckart |first3=A. |last4=Fricke |first4=K. |last5=Johnston |first5=K. J. |last6=Kuhr |first6=H. |last7=Liebert |first7=J. |last8=Pauliny-Toth |first8=I. I. K. |last9=Schleicher |first9=H. |last10=Stockman |first10=H. |last11=Strittmatter |first11=P. A. |last12=Witzel |first12=A. |date=July 1981 |title=Observations of six flat spectrum sources from the 5 GHz survey |url=https://articles.adsabs.harvard.edu//full/1981ApJ...247L..53B/L000053.000.html |journal=The Astrophysical Journal |volume=247 |pages=L53 |doi=10.1086/183588 |bibcode=1981ApJ...247L..53B |issn=0004-637X}}</ref> This object is also classified as a [[blazar]] because of its extreme variability on the [[electromagnetic spectrum]]<ref>{{Cite journal |last1=Carrasco |first1=L. |last2=Porras |first2=A. |last3=Escobedo |first3=G. |last4=Recillas |first4=E. |date=2022-07-01 |title=A New NIR Flare of the Blazar HB89 1803+784 |url=https://ui.adsabs.harvard.edu/abs/2022ATel15505....1C/abstract |journal=The Astronomer's Telegram |volume=15505 |pages=1|bibcode=2022ATel15505....1C }}</ref><ref>{{Cite journal |last1=Nesci |first1=R. |last2=Maesano |first2=M. |last3=Massaro |first3=E. |last4=Montagni |first4=F. |last5=Trenta |first5=F. |date=1999-01-01 |title=BVRI photometry of the blazar S5 1803+78. |url=https://ui.adsabs.harvard.edu/abs/1999MmSAI..70..233N/abstract |journal=Memorie della Societa Astronomica Italiana |volume=70 |pages=233–234 |bibcode=1999MmSAI..70..233N |issn=0037-8720}}</ref> and a source of [[gamma ray]] activity.<ref>{{Cite journal |last1=Giroletti |first1=M. |last2=Ciprini |first2=S. |last3=La Mura |first3=G. |date=2022-03-01 |title=Fermi-LAT detection of highest gamma-ray daily flux from the BL Lac S5 1803+78 |url=https://ui.adsabs.harvard.edu/abs/2022ATel15292....1G/abstract |journal=The Astronomer's Telegram |volume=15292 |pages=1|bibcode=2022ATel15292....1G }}</ref> According to preliminary analysis in May 2011, the source of S5 1803+784 has a gamma ray flux (''E'' >100 [[Electronvolt|MeV]]) of {{nowrap|1.1 ± 0.2 × 10<sup>−6</sup>}} {{nowrap|photon cm<sup>−2</sup> s<sup>−1</sup>}}.<ref>{{Cite journal |last=Reyes |first=Luis C. |date=2011-05-01 |title=Fermi LAT detection of a GeV flare from blazar S5 1803+78 |url=https://ui.adsabs.harvard.edu/abs/2011ATel.3322....1R/abstract |journal=The Astronomer's Telegram |volume=3322 |pages=1|bibcode=2011ATel.3322....1R }}</ref> == Description == S5 1803+784 is in a constant flaring state.<ref>{{Cite web |last1=Nowakowski |first1=Tomasz |last2=Phys.org |title=Study investigates flaring activity of blazar S5 1803+78 |url=https://phys.org/news/2022-04-flaring-blazar-s5.html |access-date=2024-11-05 |website=phys.org |language=en}}</ref><ref>{{Cite journal |last1=Pursimo |first1=Tapio |last2=Ojha |first2=Roopesh |last3=Dahle |first3=Haakon |date=2020-05-01 |title=Bright Optical Flare in the flaring gamma-ray BL Lac S5 1803+784 |url=https://ui.adsabs.harvard.edu/abs/2020ATel13711....1P/abstract |journal=The Astronomer's Telegram |volume=13711 |pages=1|bibcode=2020ATel13711....1P }}</ref> In April 2020, S5 1803+784 had a major outburst followed by more flaring episodes. During this period, S5 1803+784 exhibited highest [[flux]] level of 1.1 × 10<sup>−6</sup> ph cm<sup>−2</sup> s<sup>−1</sup> while in pre-flaring region, a low flux was shown below 0.2 × 10<sup>−6</sup> ph cm<sup>−2</sup> s<sup>−1</sup>.<ref>{{Cite journal |last1=Priya |first1=Shruti |last2=Prince |first2=Raj |last3=Agarwal |first3=Aditi |last4=Bose |first4=Debanjan |last5=Özdönmez |first5=Aykut |last6=Ege |first6=Ergün |date=2022-04-15 |title=Multiwavelength temporal and spectral analysis of Blazar S5 1803+78 |journal=Monthly Notices of the Royal Astronomical Society |volume=513 |issue=2 |pages=2239–2251 |doi=10.1093/mnras/stac1009 |doi-access=free |issn=0035-8711|arxiv=2204.04739 }}</ref> In August 2020, S5 1803+784 entered a new flaring phase which lasted for 57 days. Its source [[brightness]] varied from 13.617 ± 0.009 to 15.888 ± 0.01 in [[Photometric system|R-bands]], which the brightest-ever state for S5 1803+783 was observed on August 25.<ref>{{Cite journal |last1=Agarwal |first1=A. |last2=Pandey |first2=Ashwani |last3=Özdönmez |first3=Aykut |last4=Ege |first4=Ergün |last5=Kumar Das |first5=Avik |last6=Karakulak |first6=Volkan |date=2022-07-01 |title=Characterizing the Optical Nature of the Blazar S5 1803+784 during Its 2020 Flare |journal=The Astrophysical Journal |volume=933 |issue=1 |pages=42 |doi=10.3847/1538-4357/ac6cef |doi-access=free |issn=0004-637X|arxiv=2205.02171 }}</ref> It is also known to show [[Infrared|near-infrared]] flares.<ref>{{Cite journal |last1=Carrasco |first1=L. |last2=Escobedo |first2=G. |last3=Porras |first3=A. |last4=Recillas |first4=E. |last5=Felix |first5=L. |date=2023-11-01 |title=A recent NIR Flare and similar amplitude fluctuations near maximum light of the blazar [HB89] 1803+784 |url=https://ui.adsabs.harvard.edu/abs/2023ATel16344....1C/abstract |journal=The Astronomer's Telegram |volume=16344 |pages=1|bibcode=2023ATel16344....1C }}</ref>
In an optical [[light curve]], S5 1803+784 showed the overall variation greater than 3 [[Magnitude (astronomy)|magnitudes]] with the largest changes observed within three flares through no [[Periodic function|periodicity]] was found. However, the [[Radio spectrum|radio band]] variability is found different, showing modest oscillations instead of flares with a maximum [[amplitude]] of 30%.<ref>{{Cite journal |last1=Nesci |first1=R. |last2=Massaro |first2=E. |last3=Maesano |first3=M. |last4=Montagni |first4=F. |last5=Sclavi |first5=S. |last6=Venturi |first6=T. |last7=Dallacasa |first7=D. |last8=D'Alessio |first8=F. |date=2002-07-01 |title=Optical and Radio Monitoring of S5 1803+784 |url=https://ui.adsabs.harvard.edu/abs/2002AJ....124...53N/abstract |journal=The Astronomical Journal |volume=124 |issue=1 |pages=53–64 |doi=10.1086/341038 |arxiv=astro-ph/0204365 |bibcode=2002AJ....124...53N |issn=0004-6256}}</ref>
S5 1803+784 shows a peculiar radio structure with a compact radio core.<ref>{{Cite journal |last1=Airapetyan |first1=E.A. |last2=Matveenko |first2=L.I |date=1997 |title=The Fine Structure of Compact Radio Sources from Geodetic Data |url=https://articles.adsabs.harvard.edu/pdf/1997AstL...23...64A |journal=Astronomy Letters |volume=23 |issue=1 |pages=64–70}}</ref> There is a presence of an ejector [[nozzle]], 0.1 [[parsec]]s in [[diameter]] surrounded by a ring structure with both a diameter of 1.4 parsecs and a width of 0.25 parsecs.<ref>{{Cite journal |last1=Matveyenko |first1=L. I. |last2=Sivakon' |first2=S. S. |last3=Jorstad |first3=S. G. |last4=Marscher |first4=A. P. |date=2010-03-01 |title=Structural peculiarities of the AGN object 1803+784 |url=https://ui.adsabs.harvard.edu/abs/2010AstL...36..151M/abstract |journal=Astronomy Letters |volume=36 |issue=3 |pages=151–166 |doi=10.1134/S1063773710030011 |bibcode=2010AstL...36..151M |issn=0320-0108}}</ref> Furthermore, it has a weaker secondary component located 45 arcseconds south and slightly to the west side of the core with a faint [[Radiation|emission]] bridge joining them together.<ref>{{Cite journal |last1=Gabuzda |first1=D. C. |last2=Cawthorne |first2=T. V. |date=2000-12-21 |title=VLBI polarization images of eight compact active galactic nuclei at {{lambda}} = 1.3 cm |url=https://articles.adsabs.harvard.edu/pdf/2000MNRAS.319.1056G |journal=Monthly Notices of the Royal Astronomical Society |volume=319 |issue=4 |pages=1056–1066 |doi=10.1046/j.1365-8711.2000.03881.x |doi-access=free |issn=0035-8711}}</ref><ref>{{Cite journal |last1=Britzen |first1=S. |last2=Krichbaum |first2=T. P. |last3=Strom |first3=R. G. |last4=Witzel |first4=A. |last5=Muxlow |first5=T. W. B. |last6=Matveenko |first6=L. I. |last7=Campbell |first7=R. M. |last8=Alef |first8=W. |last9=Hummel |first9=C. A. |last10=Zensus |first10=A. |date=2005-11-25 |title=Large-scale motion, oscillations and a possible halo on the counter-jet side in 1803+784 |url=https://www.aanda.org/articles/aa/full/2005/47/aa1823-04/aa1823-04.html |journal=Astronomy & Astrophysics |volume=444 |issue=2 |pages=443–454 |doi=10.1051/0004-6361:20041823 |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Cassaro |first1=P. |last2=Stanghellini |first2=C. |last3=Bondi |first3=M. |last4=Dallacasa |first4=D. |last5=Della Ceca |first5=R. |last6=Zappala |first6=R.A. |date=1999 |title=Extended radio emission in BL Lac objects. I. The images |url=https://aas.aanda.org/articles/aas/pdf/1999/18/ds1030.pdf |journal=Astronomy & Astrophysics Supplement Series |volume=139 |issue=3 |pages=601–616|doi=10.1051/aas:1999511 }}</ref>
The [[Astrophysical jet|jet]] of S5 1803+784 has a complex morphology. In [[milliarcsecond]]-scales, it is described as a bend chain of seven individual jet components with both separation gaps of 0.2 and 3 mas from its core, where new components appear to be emerging from it every two years. Three of the jet components are found to approach a brightest and stationary component (1.4 mas at 8.4 GHz) exhibiting apparent [[superluminal motion]].<ref>{{Cite journal |last1=Britzen |first1=S. |last2=Witzel |first2=A. |last3=Krichbaum |first3=T. P. |last4=Beckert |first4=T. |last5=Campbell |first5=R. M. |last6=Schalinski |first6=C. |last7=Campbell |first7=J. |date=2005-09-21 |title=The radio structure of S5 1803+784 |journal=Monthly Notices of the Royal Astronomical Society |volume=362 |issue=3 |pages=966–974 |doi=10.1111/j.1365-2966.2005.09369.x |doi-access=free |issn=0035-8711}}</ref> Further studies showed in the jet's parsec-scale, most of the jet components within the inner core remain constant over a long period of time with the jet's width changing periodically around 8–9 years.<ref>{{Cite journal |last1=Britzen |first1=S. |last2=Kudryavtseva |first2=N. A. |last3=Witzel |first3=A. |last4=Campbell |first4=R. M. |last5=Ros |first5=E. |last6=Karouzos |first6=M. |last7=Mehta |first7=A. |last8=Aller |first8=M. F. |last9=Aller |first9=H. D. |last10=Beckert |first10=T. |last11=Zensus |first11=J. A. |date=February 2010 |title=The kinematics in the pc-scale jets of AGN |url=http://dx.doi.org/10.1051/0004-6361/20079267 |journal=Astronomy and Astrophysics |volume=511 |pages=A57 |doi=10.1051/0004-6361/20079267 |issn=0004-6361|arxiv=1001.1973 }}</ref> Interestingly, the jet is shaped into a [[cone]] which the 18-cm emission from the injector region is found to be weaken by a factor of 300.<ref>{{Cite journal |last1=Matveenko |first1=L. I. |last2=Witzel |first2=A. I. |date=1999 |title=The Jets of Quasars 3C 345 and 1803+784 |url=https://articles.adsabs.harvard.edu/pdf/1999AstL...25..555M |journal=Symposium - International Astronomical Union |volume=194 |pages=229–234 |doi=10.1017/s0074180900162047 |issn=0074-1809}}</ref>
== References == <references />
== External links == *[https://simbad.u-strasbg.fr/simbad/sim-id?Ident=8C%201803%2B784 S5 1803+784 on SIMBAD] *[http://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=64242&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1 S5 1803+784 on NASA/IPAC Database]
{{Draco (constellation)}}
[[Category:BL Lacertae objects]] [[Category:Draco (constellation)]] [[Category:Blazars]] [[Category:Active galaxies]] [[Category:IRAS catalogue objects|18036+7827]] [[Category:Astronomical objects discovered in 1981]]