XTE J1739-285

{{Short description|Neutron star in the constellation Ophiuchus}}

{{Use dmy dates|date=April 2025}}

{{Starbox begin

| name=XTE J1739−285}}

{{Starbox observe

| epoch=J2000

| ra={{RA|17|39|53.95}}

| dec={{DEC|−28|29|46.8}}

| appmag_v=

| constell=Ophiuchus }}

{{Starbox character

| class=Q

| b-v=

| u-b=

| variable=None }}

{{Starbox astrometry

| radial_v=

| prop_mo_ra=

| prop_mo_dec=

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|- style="vertical-align: top;"

| Distance

| 39,000 Ly

{{Starbox detail

| mass=1.51{{Cite journal |arxiv = 0708.3566|bibcode = 2007PASP..119.1108Z|title = Does Submillisecond Pulsar XTE J1739−285 Contain a Weak Magnetic Neutron Star or Quark Star?|journal = Publications of the Astronomical Society of the Pacific|volume = 119|issue = 860|pages = 1108|last1 = Zhang|first1 = C. M|last2 = Yin|first2 = H. X|last3 = Zhao|first3 = Y. H|last4 = Wei|first4 = Y. C|last5 = Li|first5 = X. D|year = 2007|doi = 10.1086/522796| s2cid=15651718 }}

| radius_km=10.9

| luminosity=

| temperature=

| age= }}

{{Starbox catalog

| names=SWIFT J1740.6−2821B }}

{{Starbox reference

|Simbad=XTE+J1739-285}}

{{Starbox end}}

XTE J1739−285 is a neutron star,[http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=XTE+J1739-285+&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Low mass X-ray binary] in the constellation Ophiuchus, situated approximately 39,000 light-years from Earth. It was first observed on 19 October 1999 by NASA's

Rossi X-ray Timing Explorer satellite.

It had previously been claimed that XTE J1739−285 was the fastest-spinning celestial body yet known, with a frequency of 1122 Hz.[https://iopscience.iop.org/article/10.1086/513270/fulltext/ Evidence of 1122 Hz X-Ray Burst Oscillations from the Neutron Star X-Ray Transient XTE J1739–285] However, a re-analysis of these data by other astronomers has been unable to reproduce this result.See footnote 1 of {{cite journal | bibcode = 2008AIPC.1068...67C | title=The spin distribution of millisecond X-ray pulsars | journal=American Institute of Physics Conference Series | volume=1068 | page=67 | year=2008|arxiv = 0809.4031 |doi = 10.1063/1.3031208 | last1=Chakrabarty | first1=D | last2=Wijnands | first2=Rudy | last3=Altamirano | first3=Diego | last4=Soleri | first4=Paolo | last5=Degenaar | first5=Nathalie | last6=Rea | first6=Nanda | last7=Casella | first7=Piergiorgio | last8=Patruno | first8=Alessandro | last9=Linares | first9=Manuel | s2cid=14585824 }}

XTE J1739−285 has been proposed as a possible quark star, as well as 3C 58.