Vela X-1

{{Short description|X-ray emission source in the constellation Vela}}

{{About|the high-mass X-ray binary system|pulsar associated with the Vela supernova remnant|Vela Pulsar}}

{{Starbox begin

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{{Starbox image

| image = 250px

| caption = A visual band light curve for GP Velorum, adapted from Tjemkes et al. (1986)

}}

{{Starbox observe

| epoch=J2000.0 (ICRS)

| constell=Vela

| ra={{RA|09|02|06.861}}

| dec={{DEC|-40|33|16.90}}

| appmag_v = 6.87

}}

{{Starbox character

| class = B0.5Ia

| appmag_1_passband =B

| appmag_1 =7.301

| appmag_2_passband = V

| appmag_2 =6.926

| appmag_3_passband = J

| appmag_3 ={{val|5.833|0.020}}

| appmag_4_passband = H

| appmag_4 ={{val|5.705|0.034}}

| appmag_5_passband = K

| appmag_5 ={{val|5.596|0.024}}

| r-i =

| v-r =

| b-v = 0.50{{cite journal

|last1=Klare |first1=G.

|last2=Neckel |first2=T.

|year=1977

|title=UBV, Hβ and polarization measurements of 1660 southern OB stars

|journal=Astronomy and Astrophysics Supplement

|volume=27 |pages=215

|bibcode=1977A&AS...27..215K

}}

| u-b =−0.51

| variable =Complex{{cn|date=July 2022}}

}}

{{Starbox astrometry

| prop_mo_ra=−4.822

| prop_mo_dec=9.282

| parallax=0.4962

| p_error=0.0152

| parallax_footnote={{cite Gaia DR3|5620657678322625920}}

| dist_ly=

| dist_pc=

}}

{{Starbox catalog

| names=Supergiant component: GP Vel, HD 77581, SAO 220767, HIP 44368, CPD−40°3072, CD−40°4838;
X-ray component: 1XRS 09002-403, 1RXS J090207.0-403311, 4U 0900-40}}

{{Starbox reference|Simbad=V*+GP+Vel}}

{{Starbox end}}

Vela X-1 is a pulsing, eclipsing high-mass X-ray binary (HMXB) system, associated with the Uhuru source 4U 0900-40 and the supergiant star HD 77581.

The X-ray emission of the neutron star is caused by the capture and accretion of matter from the stellar wind of the supergiant companion. Vela X-1 is the prototypical detached HMXB.

{{ cite journal

|last1=Mauche |first1=C. W.

|last2=Liedahl |first2=D. A.

|last3=Akiyama |first3=S.

|last4=Plewa |first4=T.

|year=2007

|title=Hydrodynamic and Spectral Simulations of HMXB Winds

|journal=Progress of Theoretical Physics Supplement

|volume=169 |pages=196–199

|arxiv=0704.0237

|bibcode=2007PThPS.169..196M

|doi=10.1143/PTPS.169.196

|s2cid=17149878

}}

The orbital period of the system is 8.964 days, with the neutron star being eclipsed for about two days of each orbit by HD 77581. It has been given the variable star designation GP Velorum, and it varies from visual magnitude 6.76 to 6.99.

The spin period of the neutron star is about 283 seconds, and gives rise to strong X-ray pulsations.

The mass of the pulsar is estimated to be at least {{val|1.88|0.13}} solar masses.

{{cite journal

|last1=Quaintrell |first1=H.

|display-authors=etal

|year=2003

|title=The mass of the neutron star in Vela X-1 and tidally induced non-radial oscillations in GP Vel

|journal=Astronomy and Astrophysics

|volume=401 |pages=313–324

|arxiv=astro-ph/0301243

|bibcode=2003A&A...401..313Q

|doi=10.1051/0004-6361:20030120

|s2cid=5602110

}}