View source for W49B

{{Short description|Supernova remnant nebula in the constellation Aquila}}
{{Infobox supernova
| image = Image:Supernova Remnant W49B in x-ray, radio, and infrared.jpg
| image_size = 280px
| caption = W49B image from [[Chandra X-Ray Observatory|Chandra]] (x-rays in blue and green), the [[Palomar Observatory]] (infrared in yellow), and [[Very Large Array]] (radio in pink)
| epoch = [[J2000.0]]
| type = S
| SNRtype =
| host = 
| constellation = [[Aquila (constellation)|Aquila]]
| ra = {{RA|19|11|09}}<ref name=simbad/>
| dec = {{DEC|+09|06|24}}<ref name=simbad/>
| gal = 043.275 -00.190
| discovery = 
| iauc = 
| mag_v =
| distance = {{convert|10|kpc|ly|lk=on}}<ref name=zhu/>
| notes = 
}}

'''W49B''' (also known as '''SNR G043.3-00.2''' or '''3C 398''') is a [[nebula]] in [[Westerhout 49]] (W49). The nebula is a [[supernova remnant]], probably from a [[Type Ib and Ic supernovae|type Ib or Ic]] [[supernova]] that occurred around 1,000 years ago. It may have produced a [[gamma-ray burst]] and is thought to have left a [[black hole]] remnant.

==Nebula==
W49B is a supernova remnant (SNR) located roughly 33,000 [[light-years]] from Earth.<ref name=zhu/> Radio wavelengths show a shell four [[arc minute]]s across. There are [[infrared]] "rings" (about 25 light-years in diameter) forming a "barrel", and intense [[X-ray]] radiation coming from [[Forbidden mechanism|forbidden emission]] of [[nickel]] and [[iron]] in a bar along its axis. W49B is also one of the most luminous SNRs in the galaxy at [[gamma-ray]] wavelengths.<ref name=lopez/> It is invisible at optical wavelengths.<ref name=lopez2009/>

W49B has a number of other unusual properties. It shows [[x-ray]] emission from [[chromium]] and [[manganese]], something seen in only one other SNR. The iron in the nebula is seen only in the western half of the nebula, while other elements are distributed throughout the nebula.<ref name=lopez/>

The outer shell is interpreted as a wind-blown bubble of molecular [[hydrogen]] within the interstellar medium, commonly seen around hot luminous stars. Away from the galactic plane, there is little gas and it is very faint optically. The shell is around 10 [[parsec]]s across and 1.9 parsecs thick. Inside the shell are the x-ray jets. Where the southeastern jet reaches the shell there is a bow-shock.<ref name=keohane/>

==Supernova==
The quantity of iron and nickel within the SNR, and its asymmetric nature, imply a jet-driven type Ib or Ic supernova produced by a star with an initial mass around {{solar mass|25|link=y}}. Such supernovae are thought to be the source of some long-duration gamma-ray bursts.<ref name=lopez/> The properties of the SNR suggest that the supernova occurred about 1,000 years ago.<ref name=lopez2009/>

Due to large amounts of galactic dust, the supernova would have been invisible to Earthly viewers.{{cn|date=September 2020}}

The quantities of heavy elements such as chromium and manganese, produced by the explosive nucleosynthesis of [[silicon]] during the supernova itself, suggests that the explosion was not sufficiently energetic to produce a gamma-ray burst but does not rule it out entirely.<ref name=miceli/>

==Remnant==
The remnant from a core collapse supernova may be a [[neutron star]] or black hole. No neutron star can be detected within W49B although it would be expected to be clearly visible. This, and the models which best reproduce the nebula, imply that the remnant is a black hole.<ref name=lopez/>

==See also==
* [[List of supernova remnants]]

==References==
{{reflist|refs=

<ref name=miceli>{{cite journal|bibcode=2008AdSpR..41..390M|arxiv=astro-ph/0701475|title=A physical interpretation of the jet-like X-ray emission from supernova remnant W49B|journal=Advances in Space Research|volume=41|issue=3|pages=390|last1=Miceli|first1=M.|last2=Decourchelle|first2=A.|last3=Ballet|first3=J.|last4=Bocchino|first4=F.|last5=Hughes|first5=J.|last6=Hwang|first6=U.|last7=Petre|first7=R.|year=2008|doi=10.1016/j.asr.2007.01.030|s2cid=119072005 }}</ref>

<ref name=lopez>{{cite journal|doi=10.1088/0004-637X/764/1/50|arxiv=1301.0618|title=The Galactic Supernova Remnant W49B Likely Originates from a Jet-Driven, Core-Collapse Explosion|journal=The Astrophysical Journal|volume=764|pages=50|year=2013|last1=Lopez|first1=Laura A.|last2=Ramirez-Ruiz|first2=Enrico|last3=Castro|first3=Daniel|last4=Pearson|first4=Sarah|issue=1 |bibcode = 2013ApJ...764...50L |s2cid=15588994 }}</ref>

<ref name=keohane>{{cite journal|bibcode=2007ApJ...654..938K|arxiv=astro-ph/0609533|title=A Near-Infrared and X-Ray Study of W49 B: A Wind Cavity Explosion|journal=The Astrophysical Journal|volume=654|issue=2|pages=938|last1=Keohane|first1=Jonathan W.|last2=Reach|first2=William T.|last3=Rho|first3=Jeonghee|last4=Jarrett|first4=Thomas H.|year=2007|doi=10.1086/509311|s2cid=118832025 }}</ref>

<ref name=simbad>{{cite simbad|title=W49B|access-date=2017-05-12}}</ref>

<ref name=lopez2009>{{cite journal|bibcode=2009ApJ...691..875L|arxiv=0810.0009|title=Tools for Dissecting Supernova Remnants Observed with Chandra: Methods and Application to the Galactic Remnant W49B|journal=The Astrophysical Journal|volume=691|pages=875–893|last1=Lopez|first1=L. A.|last2=Ramirez-Ruiz|first2=E.|last3=Pooley|first3=D. A.|last4=Jeltema|first4=T. E.|year=2009|issue=1 |doi=10.1088/0004-637X/691/1/875|s2cid=14835718 }}</ref>

<ref name=zhu>{{cite journal|bibcode=2014ApJ...793...95Z|arxiv=1407.8260|title=Supernova Remnant W49B and Its Environment|journal=The Astrophysical Journal|volume=793|issue=2|pages=95|last1=Zhu|first1=H|last2=Tian|first2=W. W|last3=Zuo|first3=P|year=2014|doi=10.1088/0004-637X/793/2/95|s2cid=119228478 }}</ref>

}}

==External links==
*{{cite web|url=http://www.science20.com/news_articles/w49b_did_explosion_create_our_galaxys_youngest_black_hole-103633 |title=W49B: Did An Explosion Create Our Galaxy's Youngest Black Hole? |date=2013-02-13|access-date=2017-05-12}}

*{{cite web|url=https://www.newscientist.com/blogs/shortsharpscience/2013/02/youngest-black-hole.html |title=Baby black hole is swaddled in a supernova remnant |author=Flora Graham |publisher=[[New Scientist]] |date=2013-02-15|access-date=2017-05-12}}

{{Stars of Aquila}}

{{DEFAULTSORT:W49B}}
[[Category:Aquila (constellation)]]
[[Category:Supernova remnants]]
[[Category:Gamma-ray bursts]]
[[Category:3C objects|398]]