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|name=SAX J1808.4−3658
|name=SAX J1808.4−3658
|constell=[[Sagittarius (constellation)|Sagittarius]]
|constell=[[Sagittarius (constellation)|Sagittarius]]
|ra={{RA|17|45|39.73}}<ref name=simbad>{{cite simbad|title=SAX J1808.4-3658|accessdate=15 January 2017}}</ref>
|ra={{RA|18|08|27.54}}<ref name=simbad>{{cite simbad|title=SAX J1808.4-3658|accessdate=15 January 2017}}</ref>
|dec={{DEC|−29|00|29.7}}<ref name=simbad/>
|dec={{DEC|−36|58|44.3}}<ref name=simbad/>
|class=[[Neutron star]]
|class=[[Neutron star]]
|appmag_v=16.51
|appmag_v=16.51
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|Simbad=SAX+J1808.4-3658
|Simbad=SAX+J1808.4-3658
}}
}}
A transient X-ray source first discovered in 1996 by the Italian-Dutch [[BeppoSAX]] satellite, '''SAX J1808.4−3658''' revealed X-ray pulsations at the 401&nbsp;Hz neutron star spin frequency when it was observed during a subsequent outburst in 1998 by [[NASA]]'s [[Rossi X-ray Timing Explorer|RXTE]] satellite.<ref>{{cite journal|doi=10.1038/28557|title=A millisecond pulsar in an X-ray binary system|year=1998|last1=Wijnands|first1=Rudy|last2=van der Klis|first2=Michiel|journal=[[Nature (journal)|Nature]]|bibcode = 1998Natur.394..344W|volume=394|issue=6691|pages=344–346|s2cid=4428048}}</ref> The [[neutron star]] is orbited by a [[brown dwarf]] binary companion with a likely mass of 0.05 solar masses, every 2.01 hours. [[X-ray burster|X-ray burst]] oscillations and quasi-periodic oscillations in addition to coherent X-ray pulsations have been seen from SAX J1808.4-3658, making it a Rosetta stone for interpretation of the timing behavior of [[low-mass X-ray binary|low-mass X-ray binaries]].
The first accreting millisecond pulsar discovered in 1998 by the Italian-Dutch [[BeppoSAX]] satellite, '''SAX J1808.4−3658''' revealed X-ray pulsations at the 401&nbsp;Hz neutron star spin frequency when it was observed during a subsequent outburst in 1998 by [[NASA]]'s [[Rossi X-ray Timing Explorer|RXTE]] satellite.<ref>{{cite journal|doi=10.1038/28557|title=A millisecond pulsar in an X-ray binary system|year=1998|last1=Wijnands|first1=Rudy|last2=van der Klis|first2=Michiel|journal=[[Nature (journal)|Nature]]|bibcode = 1998Natur.394..344W|volume=394|issue=6691|pages=344–346|s2cid=4428048}}</ref> The [[neutron star]] is orbited by a [[brown dwarf]] binary companion with a likely mass of 0.05 solar masses, every 2.01 hours. [[X-ray burster|X-ray burst]] oscillations and quasi-periodic oscillations in addition to coherent X-ray pulsations have been seen from SAX J1808.4-3658, making it a Rosetta stone for interpretation of the timing behavior of [[low-mass X-ray binary|low-mass X-ray binaries]].


[[File:V4580SgrLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|red band]] [[light curve]] for V4580 Sagittarii, adapted from Elebert ''et al.'' (2009)<ref name="Elebert"/>]]
[[File:V4580SgrLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|red band]] [[light curve]] for V4580 Sagittarii, adapted from Elebert ''et al.'' (2009)<ref name="Elebert"/>]]
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{{Reflist|refs=
{{Reflist|refs=


<ref name="Elebert">{{cite journal |last1=Elebert |first1=P. |last2=Reynolds |first2=M. T. |last3=Callanan |first3=P. J. |last4=Hurley |first4=D. J. |last5=Ramsay |first5=G. |last6=Lewis |first6=F. |last7=Russell |first7=D. M. |last8=Nord |first8=B. |last9=Kane |first9=S. R. |last10=Depoy |first10=D. L. |last11=Hakala |first11=P. |title=Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst |journal=Monthly Notices of the Royal Astronomical Society |date=May 2009 |volume=395 |issue=884-894 |doi=10.1111/j.1365-2966.2009.14562.x |url=https://ui.adsabs.harvard.edu/abs/2009MNRAS.395..884E |access-date=13 March 2022|doi-access=free }}</ref>
<ref name="Elebert">{{cite journal |last1=Elebert |first1=P. |last2=Reynolds |first2=M. T. |last3=Callanan |first3=P. J. |last4=Hurley |first4=D. J. |last5=Ramsay |first5=G. |last6=Lewis |first6=F. |last7=Russell |first7=D. M. |last8=Nord |first8=B. |last9=Kane |first9=S. R. |last10=Depoy |first10=D. L. |last11=Hakala |first11=P. |title=Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst |journal=Monthly Notices of the Royal Astronomical Society |date=May 2009 |volume=395 |issue=884–894 |doi=10.1111/j.1365-2966.2009.14562.x |bibcode=2009MNRAS.395..884E |doi-access=free |arxiv=0901.3991 }}</ref>


}}
}}

Latest revision as of 18:48, 6 May 2024

SAX J1808.4−3658
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 18h 08m 27.54s[1]
Declination −36° 58′ 44.3″[1]
Apparent magnitude (V) 16.51
Spectral typeNeutron star
Other designations
V4580 Sgr, PSR J1808−3658, SWIFT J1808.5−3655, INTREF 881, XTE J1808−369
Database references
SIMBADdata

The first accreting millisecond pulsar discovered in 1998 by the Italian-Dutch BeppoSAX satellite, SAX J1808.4−3658 revealed X-ray pulsations at the 401 Hz neutron star spin frequency when it was observed during a subsequent outburst in 1998 by NASA's RXTE satellite.[2] The neutron star is orbited by a brown dwarf binary companion with a likely mass of 0.05 solar masses, every 2.01 hours. X-ray burst oscillations and quasi-periodic oscillations in addition to coherent X-ray pulsations have been seen from SAX J1808.4-3658, making it a Rosetta stone for interpretation of the timing behavior of low-mass X-ray binaries.

A red band light curve for V4580 Sagittarii, adapted from Elebert et al. (2009)[3]

These accreting millisecond X-ray pulsars are thought to be the evolutionary progenitors of recycled radio millisecond pulsars. A total of thirteen accreting millisecond X-ray pulsars have been discovered as of January 2011. Three of them are Intermittent millisecond X-ray pulsars (HETE J1900.1-2455, Aql X-1 and SAX J1748.9-2021), i.e. they emit pulsations sporadically during the outburst.

On 21 August 2019 (UTC; 20 August in the US), Neutron Star Interior Composition Explorer (NICER) spotted the brightest X-ray burst so far observed.[4] It came from SAX J1808.4−3658.

References

[edit]
  1. ^ a b "SAX J1808.4-3658". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 15 January 2017.
  2. ^ Wijnands, Rudy; van der Klis, Michiel (1998). "A millisecond pulsar in an X-ray binary system". Nature. 394 (6691): 344–346. Bibcode:1998Natur.394..344W. doi:10.1038/28557. S2CID 4428048.
  3. ^ Elebert, P.; Reynolds, M. T.; Callanan, P. J.; Hurley, D. J.; Ramsay, G.; Lewis, F.; Russell, D. M.; Nord, B.; Kane, S. R.; Depoy, D. L.; Hakala, P. (May 2009). "Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst". Monthly Notices of the Royal Astronomical Society. 395 (884–894). arXiv:0901.3991. Bibcode:2009MNRAS.395..884E. doi:10.1111/j.1365-2966.2009.14562.x.
  4. ^ NICER Telescope Spots Brightest X-Ray Burst Ever Observed


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