Hemphill: updated simbad link

2018-07-11T18:38:34Z

updated simbad link

Kuehnel: Created page with "Category:Accreting X-ray Pulsars Also known as: V* QV Nor [http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 Name=V*+QV+Nor&submi..."

2018-04-18T14:33:47Z

Created page with "Category:Accreting X-ray Pulsars Also known as: V* QV Nor [http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 Name=V*+QV+Nor&submi..."

New page

[[Category:Accreting X-ray Pulsars]]

Also known as: V* QV Nor [http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 Name=V*+QV+Nor&submit=display+all+measurements#lab_meas SIMBAD]

'''Monitoring data''':
[http://gammaray.msfc.nasa.gov/batse/pulsar/data/histories.html CGRO/BATSE]
[http://xte.mit.edu/asmlc/srcs/x1538-522.html RXTE/ASM]
[http://swift.gsfc.nasa.gov/docs/swift/results/transients/H1538-522/ Swift/BAT]
[http://maxi.riken.jp/top/index.php?cid=1&jname=j1542-523 MAXI]
[http://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/4u1538.html Fermi/GBM pulsed flux]

= Coordinates =
RA 15h 42m 23.36s, Dec -52° 23' 9.6" 
RA 235°.597 , Dec -52°.386 
l 327°.420 , b +2°.164

= Binary system =

Distance estimated 6.4±1.0 kpc by <ref name="Reynolds92" />.

Neutron star mass: Mx=1.06+0.41-0.34 Msol <ref name="vKerkwijk95" />.

QV Nor mass Mopt=16.4+5.2-4.0 Msol <ref name="vKerkwijk95" />.

QV Nor mass Mopt=19.8±3.3 Msol <ref name="Reynolds92" />.

== Orbit ==

{| class="wikitable"
! Parameter
! Value
! Unit
! Reference
|-
| Porb
| 3.728366±0.000032
| days
| <ref name="Clark00" />
|-
| Tpi/2
| 50,450.206±0.014
| MJD
| <ref name="Clark00" />
|-
| a sin i
| 56.6±0.7
| lt-sec
| <ref name="Clark00" />
|-
| e
| 0.174±0.015
|
| <ref name="Clark00" />
|-
| omega
| 64±9
| deg
| <ref name="Clark00" />
|-
| P-dot(orb)/P(orb)
| (-2.9±2.1)x10-6
| yr-1
| <ref name="Clark00" />
|-
| a0
| 47,221.488
| MJD
| <ref name="Clark00" />
|-
| a1
| 3.728366±0.000032
| days
| <ref name="Clark00" />
|-
| a2
| (-5.5±4.0)x10-8
| days
| <ref name="Clark00" />
|}
Tpi/2 = a0 + a1N + a2N2 where N is the orbit number after a0

== Optical Companion ==

'''Names''': QV Nor, 2MASS J15422335-5223095 
B0Iab supergiant (<ref name="Reynolds92" />).

{| class="wikitable"
!Parameter
!Value
!Unit
!Reference
|-
|B
| 16.3
| mag
| Simbad
|-
|R
| 13.500
| mag
| Simbad
|-
|J
| 10.385
| mag
| Simbad
|-
|H
| 9.910
| mag
| Simbad
|-
|K
| 9.677
| mag
| Simbad
|}

= Available data =

To be filled in later.

= Background =

The accreting X-ray pulsar, 4U 1538-522, has been observed by every
X-ray satellite since UHURU, and quite possibly was detected
in earlier rocket <ref name="Friedman67" />, balloon <ref name="Lewin68" />, and
satellite <ref name="Hudson69" /> observations. <ref name="Davidson77b" /> and
<ref name="Becker77" /> discovered pulsations at 528 s from a source
designated A1540-53, whose position was later updated to be coincident
with 4U 1538-522 <ref name="Davidson77" />. <ref name="Becker77" /> used the 9 day
OSO-8 observation to derive a 3.73 day orbital period from
the Doppler modulation of the observed pulse period. <ref name="Apparo78" />
localized the source to 40" with SAS-3, and then <ref name="Schwartz78" />
further refined the position error box to #12'' with HEAO-1,
thereby reducing the number of candidate optical counterparts noted in
<ref name="Cowley77" /> to a single one -- #12, a B0 supergiant designated as
QV Nor. Independently, <ref name="Parkes78" /> obtained spectra of the stars
in the SAS-3 error circle and identified star 12 to be the
counterpart of 4U 1538-522. Later photometric observations by
<ref name="Crampton78" /> detected the 3.73 d orbital variability in the
absorption and emission line radial velocity curves. A mass estimate
from the X-ray and optical data yields a neutron star mass
Mx=1.06+0.41-0.34
Msol and companion star mass Mopt=16.4+5.2-4.0 Msol
<ref name="vKerkwijk95" />. The 4U 1538-522 system is similar to other high mass
X-ray binary systems, such as Vela X-1 <ref name="Kreykenbohm08" /> and
4U 1907+09 <ref name="IntZand98" />,<ref name="Fritz06" />, with long pulse periods (hundreds of
seconds), short orbital periods (<10 days), and flaring.
The spin and orbital periods place 4U 1538-522 among the
X-ray binary systems with a supergiant companion that underfills its Roche
lobe.

= The Present Situation =

== Timing ==

Until the launch of the BATSE instrument, the sparse
satellite-by-satellite pulse period measurements had shown that
4U 1538-522 had been spinning down. Somewhere in the mid to late 1980's
this trend reversed and continuous BATSE measurements over 8 years
revealed a continuous spin-up trend <ref name="Rubin97" />. This trend has
continued at least through 2003, e.g. RXTE results <ref name="Baykal06" />.
The recent spin frequency measurements by the GBM on the Fermi
satellite [[http://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/4u1538.html]]
shows that the source underwent another torque reversal in 2008 (approximately) and has been spinning down since. The current pulse period is approximately 526.1 s.

== Spectrum ==

Initial descriptions of the spectrum included a power law modified at
low energies by photoelectric absorption plus an iron line, and at
high energies by a cutoff to an exponential shape,
e.g. <ref name="White83" />. A cyclotron resonant scattering feature
(CRSF or cyclotron line) at 20 keV was discovered by
<ref name="Clark90" /> from Ginga observations, which also showed a
modulation in the cyclotron line strength and centroid with pulse
phase. Broad band spectra were obtained in 1998 using
BeppoSAX <ref name="Robba01" />, and in 1997/2001 using RXTE
<ref name="Coburn02" />. The cyclotron line was detected at ~21 keV with a marginal indication
of a second feature at 51+4-3 keV from BeppoSAX
<ref name="Robba01" />. Phase-resolved spectroscopy by RXTE in
8 broad phase bins <ref name="Coburn02" /> revealed that the
cyclotron line centroid exhibited maxima coincident with the two pulse
peaks, which may be an indication of emission from both magnetic
poles. In addition, the power law index was seen to be flatter on the
falling portions of the pulse peaks, as has been seen in other pulsars.
The pulsed light curve from RXTE
showed significant energy-dependent structure, including a single,
broad, flat-topped main pulse which narrowed above 10 keV, a second
smaller pulse above 2 keV, and variation in the shape of the secondary
pulse with increasing energy <ref name="Coburn02" />.

'''References'''

← Older revision		Revision as of 18:38, 11 July 2018
Line 2:		Line 2:


−	Also known as: V* QV Nor [http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 ~~Name=V*+QV+Nor&submit=display+all+measurements#lab_meas~~ SIMBAD]	+	Also known as: V* QV Nor ([http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 SIMBAD])

	'''Monitoring data''':		'''Monitoring data''':

4U 1538-52 - Revision history

Hemphill: updated simbad link

Kuehnel: Created page with "Category:Accreting X-ray Pulsars Also known as: V* QV Nor [http://simbad.harvard.edu/simbad/sim-id?mescat.distance=on&mescat.xmm=on&Ident=%403458274 Name=V*+QV+Nor&submi..."