H1821+643

{{Short description|Quasar in the constellation Draco}} {{Infobox quasar | name = H1821+643 | image =File:H1821+643.jpg | caption=Chandra X-ray Observatory image of H1821+643 | epoch = J2000.0 | ra = {{RA|18|21|57.2365}}  | dec = {{DEC|+64|20|36.226}} | constellation name = Draco | z = 0.2970 | dist_ly = {{convert|3.4|Gly|Gpc}} | type = Quasar | appmag_v = 14.24 | size_v = | notes = | names = | luminosity_specify }}

'''H1821+643''' is an extraordinarily luminous, radio-quiet quasar in the constellation of Draco. <ref name=joe> {{cite journal |last1 = Walker |first1 = S. A. |last2 = Fabian |first2 = A. C. |last3 = Russell |first3 = H. R. |last4 = Sanders |first4 = J. S. |year = 2014 |title = The effect of the quasar H1821+643 on the surrounding intracluster medium: Revealing the underlying cooling flow | journal=Monthly Notices of the Royal Astronomical Society | volume=442 | issue=3 | pages=2809 | arxiv=1405.7522 | bibcode=2014MNRAS.442.2809W | doi=10.1093/mnras/stu1067 | doi-access=free }} </ref> The associated Active Galactic Nucleus (AGN) is situated in the Brightest Central Galaxy (BCG) of a massive (<math>\sim 6.3 \times 10^{14} M_\odot</math>), strong cooling flow cluster, CL 1821+64.<ref name="J S-R"/> Russel et al. (2010) spatially isolated its X-ray signal from the surrounding cluster in Chandra X-ray observatory observations and computed <math>L_\odot = 10^{47} erg/s</math> from the observed X-ray luminosity.<ref name="J S-R"> {{cite journal | last1=Sisk-Reynés | first1=Júlia | last2=Reynolds | first2=Christopher S. | last3=Matthews | first3=James H. | last4=Smith | first4=Robyn N. | date=2022 | title=Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643 | journal=Monthly Notices of the Royal Astronomical Society | volume=514 | issue=2 | page=2568 | arxiv=2205.12974 | bibcode=2022MNRAS.514.2568S | doi=10.1093/mnras/stac1389 | doi-access=free }}</ref>

==Supermassive black hole== The SMBH centred in CL 1821+64 is believed to be among the most massive in the known Universe.<ref name="J S-R"/> A variety of techniques have found different values for the mass. 5 studies found values <math>M_{BH} \sim 10^9 M_\odot</math>. Kim et al. (2004) and Floyd et al. (2008) used galactic bulge luminosity fits derived from Hubble data to find <math>10^9 M_\odot</math> and <math>3 \times 10^9 M_\odot</math> respectively. Russell et al. (2010) provided a rough estimate of <math>M_{BH} \sim 3 \times 10^9</math>{{solar mass}}.<ref name="J S-R"/> This was an underestimate with <math>\log(\Delta M_{BH}/M_\odot) \geq 1</math>. Kolman et al. (1991) and Shapovalova (2016) independently modelled the quasar UV spectrum to find <math>M_{BH} \sim 3 \times 10^9 M_\odot</math>. Capellupo et al. (2017) found <math>M_{BH} \sim 3 \times 10^9</math> using <math>H\beta</math> line emissions. 2 independent X-ray studies found significantly higher values. Reynolds et al. (2014) found <math>6\times10^9 M_\odot</math> by modelling reflection from the accretion disc and Walker et al. found <math>3\times10^{10} M_\odot</math> by modelling the interaction of the black hole with the Intracluster medium (ICM) as a Compton-cooled feeding cycle. <math>M_{BH}</math> is in the range <math>\log(M_{BH}/M_\odot) \sim 9.2 - 10.5</math>.<ref name="J S-R"/>

The Schwarzschild diameter of this black hole is between {{convert|9.4|Tm|AU|lk=on}} and {{convert|188|Tm|AU|lk=on}}, which is about 16 times the diameter of Pluto's orbit. If the hole were a Euclidean sphere, the average density would be 18 g/m3, <math>\sim 1 \%</math> the density of air at sea level on Earth.<ref group="lower-alpha">Mass 3.0×1010 * 2.0×1030=6.0×1040 kg. Volume at radius 8.6×1013 m is 2.66×1042 m3.</ref>

==Footnotes== {{notelist}}

==References== {{Reflist}}

==External links== * [https://simbad.u-strasbg.fr/simbad/sim-id?Ident=H1821%2B643 Simbad], SIMBAD * [https://ned.ipac.caltech.edu/byname?objname=H1821%2B643&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 NED], NED, NASA/IPAC Extragalactic Database

{{DEFAULTSORT:H1821 643}} Category:Draco (constellation) Category:Quasars Category:Supermassive black holes