{{Short description|Barred spiral galaxy in the constellation Draco}} {{Infobox galaxy|name=[[Markarian galaxies|Markarian]] 817|image=File:Markarian 817 (captured by the Hubble Space Telescope).jpg|caption=Mrk 817 taken by [[Hubble Space Telescope]]|epoch=J2000|constellation name=[[Draco (constellation)|Draco]]|ra=14h 36m 22.068s|dec=+58d 47m 39.38s|z=0.031328|h_radial_v=9,392 [[kilometer per second|km/s]]|dist_ly=456 [[Mly]] (140 [[Megaparsec|Mpc]])|appmag_v=14.6|size=28.69 [[kiloparsec|kpc]] (93,500 [[Light-year|ly]]) (''diameter; [[Galaxy#Isophotal diameter|D<sub>25</sub> isophote]]'')<ref name="ned"/>|type=SBc, [[Seyfert Galaxy|Sy 1.5]]<ref name="ned"/>|size_v=0.6' x 0.6'|notes=[[Seyfert galaxy]]|names=[[Uppsala General Catalogue|UGC]] 9412, SBS 1434+590, [[Catalogue of Galaxies and of Clusters of Galaxies|CGCG]] 296-015, [[IRAS]] 14349+5900, [[Principal Galaxies Catalogue|PGC]] 52202}}'''Markarian 817''' is a [[barred spiral galaxy]] located in the constellation [[Draco (constellation)|Draco]]. It is located 456 million [[light-year]]s from [[Earth]], which, given its apparent [[dimension]]s, means that Markarian 817 is about 94,000 light-years across.<ref name = "ned">{{Cite web |title=Your NED Search Results |url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=38482&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1 |access-date=2026-03-12 |website=ned.ipac.caltech.edu}}</ref> It is a [[Seyfert galaxy]].
== Features == The nucleus of Markarian 817 is found to be [[Active galactic nucleus|active]]. It is classified as a [[Seyfert galaxy|Seyfert]] 1.5<ref>{{Cite journal |last1=IIic |first1=D. |last2=Popovic |first2=L C |last3=Bon |first3=E. |last4=Mediavilla |first4=E. G. |last5=Chavushyan |first5=V. H. |title=Complex emission line region of Mrk 817 |journal=Monthly Notices of the Royal Astronomical Society|date=2006 |volume=371 |issue=4 |pages=1610–1616 |doi=10.1111/j.1365-2966.2006.10744.x |doi-access=free |arxiv=astro-ph/0607253 |bibcode=2006MNRAS.371.1610I }}</ref> or Seyfert 1.2 galaxy by the recent work done, according to Koss et al. 2017.<ref>{{Cite journal |last1=Koss |first1=Michael |last2=Trakhtenbrot |first2=Benny |last3=Ricci |first3=Claudio |last4=Lamperti |first4=Isabella |last5=Oh |first5=Kyuseok |last6=Berney |first6=Simon |last7=Schawinski |first7=Kevin |last8=Baloković |first8=Mislav |last9=Baronchelli |first9=Linda |last10=Crenshaw |first10=D. Michael |last11=Fischer |first11=Travis |last12=Gehrels |first12=Neil |last13=Harrison |first13=Fiona |last14=Hashimoto |first14=Yasuhiro |last15=Hogg |first15=Drew |date=2017-11-01 |title=BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics |journal=The Astrophysical Journal |language=en |volume=850 |issue=1 |pages=74 |doi=10.3847/1538-4357/aa8ec9 |doi-access=free |arxiv=1707.08123 |bibcode=2017ApJ...850...74K |issn=0004-637X}}</ref> The nucleus sits in a barred spiral galaxy, close to face-on and not typical for optically selected unobscured Seyferts.<ref>{{Cite journal |last1=McLeod |first1=K. K. |last2=Rieke |first2=G. H. |date=1995-03-01 |title=Near-Infrared Imaging of CfA Seyfert Galaxies |url=https://ui.adsabs.harvard.edu/abs/1995ApJ...441...96M |journal=The Astrophysical Journal |volume=441 |pages=96 |doi=10.1086/175339 |bibcode=1995ApJ...441...96M |issn=0004-637X}}</ref> There is evidence of [[Cosmic dust|dust]] along the galaxy's bar according to the [[Hubble Space Telescope|Hubble]] image.<ref>{{Cite journal |last1=Pogge |first1=Richard W. |last2=Martini |first2=Paul |date=2002-04-20 |title=''Hubble Space Telescope''Imaging of the Circumnuclear Environments of the CfA Seyfert Galaxies: Nuclear Spirals and Fueling |url=https://iopscience.iop.org/article/10.1086/339400 |journal=The Astrophysical Journal |volume=569 |issue=2 |pages=624–640 |doi=10.1086/339400 |arxiv=astro-ph/0201185 |bibcode=2002ApJ...569..624P |issn=0004-637X}}</ref>
A study conducted in February 2011, shows that the active core is not fixed as it shows strong variabilities in [[X-ray]]s and [[Ultraviolet|ultraviolet rays]] (UV). The X-ray [[luminosity]] varies by a factor of ~40 over 20 years, while the UV [[Continuum mechanics|continuum]]/[[Emission spectrum|emission]] lines vary at the most by a factor of ~2.3 over the past 30 years.<ref>{{Cite journal |last1=Winter |first1=Lisa M. |last2=Danforth |first2=Charles |last3=Vasudevan |first3=Ranjan |last4=Brandt |first4=W. N. |last5=Scott |first5=Jennifer |last6=Froning |first6=Cynthia |last7=Keeney |first7=Brian |last8=Shull |first8=J. Michael |last9=Penton |first9=Steve |last10=Mushotzky |first10=Richard |last11=Schneider |first11=Donald P. |last12=Arav |first12=Nahum |date=2011-02-01 |title=Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817 |url=https://ui.adsabs.harvard.edu/abs/2011ApJ...728...28W |journal=The Astrophysical Journal |volume=728 |issue=1 |pages=28 |doi=10.1088/0004-637X/728/1/28 |arxiv=1012.0592 |bibcode=2011ApJ...728...28W |hdl=10919/25845 |issn=0004-637X}}</ref><ref>{{Cite journal |last1=Morales |first1=Anthony M. |last2=Miller |first2=Jon M. |last3=Cackett |first3=Edward M. |last4=Reynolds |first4=Mark T. |last5=Zoghbi |first5=Abderahmen |date=2019-01-01 |title=X-Ray and UV Monitoring of the Seyfert 1.5 Galaxy Markarian 817 |journal=The Astrophysical Journal |language=en |volume=870 |issue=1 |pages=54 |doi=10.3847/1538-4357/aaeff9 |doi-access=free |arxiv=1812.06945 |bibcode=2019ApJ...870...54M |issn=0004-637X}}</ref>
A 2021 study shows that the X-ray spectrum in Markarian 817 is highly absorbed and there are new blueshifted, broad, and narrow UV [[absorption lines]], suggesting a dust-free, ionized obscurer that is located in the inner [[Active galactic nucleus|broad-line region]], partially covering the central source.<ref name=":0">{{Cite journal |last1=Kara |first1=Erin |last2=Mehdipour |first2=Missagh |last3=Kriss |first3=Gerard A. |last4=Cackett |first4=Edward M. |last5=Arav |first5=Nahum |last6=Barth |first6=Aaron J. |last7=Byun |first7=Doyee |last8=Brotherton |first8=Michael S. |last9=De Rosa |first9=Gisella |last10=Gelbord |first10=Jonathan |last11=Hernández Santisteban |first11=Juan V. |last12=Hu |first12=Chen |last13=Kaastra |first13=Jelle |last14=Landt |first14=Hermine |last15=Li |first15=Yan-Rong |date=2021-12-01 |title=AGN STORM 2. I. First results: A Change in the Weather of Mrk 817 |journal=The Astrophysical Journal |volume=922 |issue=2 |pages=151 |doi=10.3847/1538-4357/ac2159 |doi-access=free |arxiv=2105.05840 |bibcode=2021ApJ...922..151K |issn=0004-637X}}</ref> During the first 55 days, [[scientist]]s observed there is a [[Decoupling (cosmology)|de-coupling]] of the UV continuum and the UV broad emission line [[Variability hypothesis|variability]]. The next 42 days of the campaign showed the correlation recovering, as Markarian 817 entered the less obscured state. The short C IV and Lyα lags suggest that the [[accretion disk]] extends beyond the UV broad-line region.<ref name=":0" />
Markarian 817 has become a notable target of the AGN STORM 2 project, in which a group of [[astronomer]]s led by Edward M. Cackett from the [[Wayne State University]] in [[Detroit]], monitored the galaxy with the [[Neil Gehrels Swift Observatory]] for 15 months, during which they obtained [[observation]]s in X-rays and six ultraviolet/optical filters to shed more light on Markarian 817.<ref>{{Cite web |last1=Nowakowski |first1=Tomasz |last2=Phys.org |title=Observations shed more light on the properties of the galaxy Markarian 817 |url=https://phys.org/news/2023-07-properties-galaxy-markarian.html |access-date=2024-05-12 |website=phys.org |language=en}}</ref>
Further observations done in 2022 showed that the source flux in Markarian 817 has declined compared to that recorded at a prior point during the 19-year mission. From the deep [[XMM-Newton|XMM Newton]] and [[NuSTAR]] observations, the spectra presents a complex X-ray wind which consists of neutral and ionized absorption zones. Three [[velocity]] components are detected from the part of the structured ultra-fast [[Outflow boundary|outflow]] with v/c = 0.043 (+0.007,-0.003), v/c = 0.079 (+0.003,-0.0008), and v/c = 0.074 (+0.004,-0.005).<ref name=":1">{{Citation |last1=Zak |first1=Miranda K. |title=Fierce Feedback in an Obscured, Sub-Eddington State of the Seyfert 1.2 Markarian 817 |date=2023-12-11 |arxiv=2312.06487 |last2=Miller |first2=Jon M. |last3=Behar |first3=Ehud |last4=Brandt |first4=William N. |last5=Brenneman |first5=Laura |last6=Draghis |first6=Paul A. |last7=Kammoun |first7=Elias |last8=Koss |first8=Michael J. |last9=Reynolds |first9=Mark T.|journal=The Astrophysical Journal |volume=962 |issue=1 |pages=L1 |doi=10.3847/2041-8213/ad1407 |doi-access=free |bibcode=2024ApJ...962L...1Z }}</ref> These suggest that the wind likely arises at radii that are smaller compared to the optical [[broad line region]].<ref name=":1" />
== Black hole == [[File:Strong black hole winds reshape a galaxy ESA25463575.tiff|thumb|An artist's impression of ultra-fast winds blasting out from the center of Markarian 817]] The central [[black hole]] in Markarian 817 has an estimated mass of {{val|4.9|0.8|e=7|u=[[solar mass]]es}} according to Peterson et al. 2004.<ref>{{Cite journal |last1=Zak |first1=M. K. |last2=Miller |first2=J. M. |last3=Reynolds |first3=M. T. |last4=Gediman |first4=B. |last5=Han |first5=C. |last6=Hemrattaphan |first6=Y. |date=2022-04-01 |title=Recent Swift Monitoring of Mrk 817 Reveals an Extremely Low Flux State |url=https://ui.adsabs.harvard.edu/abs/2022ATel15316....1Z |journal=The Astronomer's Telegram |volume=15316 |pages=1|bibcode=2022ATel15316....1Z }}</ref> The winds of Mrk 817 move at many millions of [[Kilometre|kilometers]] per hour, thus cleaning up [[Interstellar medium|interstellar gas]] from their region of space. This cuts off the rate of production of new [[star]]s being formed in Markarian 817, leaving very little matter to feed the accretion disk.<ref>{{Cite web |title=Strong black hole winds reshape a galaxy |url=https://www.esa.int/ESA_Multimedia/Images/2024/02/Strong_black_hole_winds_reshape_a_galaxy |access-date=2024-05-12 |website=www.esa.int |language=en}}</ref> This suggests that the black hole is experiencing a "temper tantrum" and is responsible for shaping its host galaxy.<ref>{{Cite web |author1=Joanna Thompson |date=2024-02-07 |title=Star-killing 'black hole wind' spotted in a distant galaxy could explain a major mystery at the Milky Way's center |url=https://www.livescience.com/space/black-holes/star-killing-black-hole-wind-spotted-in-a-distant-galaxy-could-explain-a-major-mystery-at-the-milky-ways-center |access-date=2024-05-12 |website=livescience.com |language=en}}</ref>
In an article in which Markarian 817 and another Seyfert galaxy [[NGC 7469]] is studied, it is revealed both AGNs displayed time lags in the broad emission line, including H, He, HeI and HeII and also the FeII for Markarian 817 with respect to the varying [[Continuum mechanics|continuum]] at 5100~Å.<ref name=":2">{{Cite journal |last1=Lu |first1=Kai-Xing |last2=Wang |first2=Jian-Guo |last3=Zhang |first3=Zhi-Xiang |last4=Huang |first4=Ying-Ke |last5=Xu |first5=Liang |last6=Xin |first6=Yu-Xin |last7=Yu |first7=Xiao-Guang |last8=Ding |first8=Xu |last9=Wang |first9=De-Qing |last10=Feng |first10=Hai-Cheng |date=2021-09-01 |title=Reverberation Mapping Measurements of Black Hole Masses and Broad-Line Region Kinematics in Mrk 817 and NGC 7469 |journal=The Astrophysical Journal |volume=918 |issue=2 |pages=50 |doi=10.3847/1538-4357/ac0c78 |doi-access=free |arxiv=2106.10589 |bibcode=2021ApJ...918...50L |issn=0004-637X}}</ref> From the relationship of [[line width]]s and time lags, both galaxies showed that the broad-line regions (BLR) dynamics are consistent with the viral predication. Data provided from Markarian 817 showed almost the same kinetic structures, in which the time lags in the red wing is larger compared to the time lags in the blue wing. This indicates the BLR of Keplerian motion seemly has outflowing components during the monitoring period.<ref name=":2" />
== See also ==
* [[Markarian 590]] – a Seyfert galaxy in Cetus * [[Markarian 273]] – a Seyfert and ultraluminous infrared galaxy
== References == <references />
[[Category:Seyfert galaxies]] [[Category:Markarian galaxies|0817]] [[Category:Draco (constellation)]] [[Category:UGC objects|09412]] [[Category:Principal Galaxies Catalogue objects|052202]] [[Category:Barred spiral galaxies]] [[Category:IRAS catalogue objects|14349+5900]]