SAX J2103.5+4545

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Also known as: GSC 03588-00834 Simbad, XTE J2103+457

Monitoring data: RXTE/ASM Swift/BAT MAXI

Coordinates

RA 21h 03m 35.71s, Dec +45° 45' 05.5"
RA 315.05992 , Dec +45.75153
l 87.1303 , b -0.6848

Binary system

Distance: 5 kpc ([1]), 6.5 kpc ([2])

Orbit

Parameter Value Unit Reference
Porb 12.68(25) days [1]
Tperiastron 51519.3(2) MJD [1]
a sin i 72(6) lt-sec [1]
e 0.4(2) [1]
omega 240(30) degrees [1]

Optical Companion

Name: not reported in [2]
B0Ve star with double-peaked Halpha emission line

Parameter Value Unit Reference
B 15.3 mag [2]
V 14.2 mag [2]
R 13.7 mag [2]

Note: [3] suggested the B star HD 200709 as possible counterpart. The distance to this star is, however, around 0.7 kpc and therefore ruled out due to the findings of [1] and [2].

Description

In February 1997, BeppoSAX discovered the transient source SAX J2103.5+4545, which was in an unusual long outburst until September of the same year ([3]). The pulse period was found to be around 358.61(3) s and the spectrum could be described well by an absorbed powerlaw ([3]). Six years later, [4] found a possible optical counterpart using the 1.3-m telescope at the Skinakas Observatory. The spectrum showed a prominent, double-peaked Halpha emission line.

Spectrum

The spectrum of SAX J2103.5+4545 can be described well by an absorbed cutoff powerlaw with an additional black body and a source intrinsic iron line ([5], [6]). Depending on the used detectors, the spectral parameters were found as follows:

Parameter Value1 Value2 Unit
NH 0.66(2) cm-2
Gamma 0.77(5) 1.0(1)
Ecut 7.89 (fix) 7.6(20) keV
Efold 27.1 (fix) 30.9(25) keV
kTbbody 1.88(2) keV

sup>1 [6], XMM- and RXTE observations
2 [5], INTEGRAL observations

No cyclotron absorption feature was found in the spectrum yet. This might be due to the fact, that the magnetic field of the source is in the order of 12(3)x1012 G ([7]), which would imply the fundamental cyclotron line to be around 140 keV.

Pulse Period & Profiles

Since its discovery in 1999 the pulse period of SAX J2103.5+4545 changed from 358.61(3) s to 354.7940(8) s at the end of 2002, indicating a long-term spin-up trend ([3], [7], respectively). This same trend was confirmed by [(biblio:Blay04)], who analyzed an INTEGRAL obvseration of the 2002 outburst. The spin-up rate during the 2002 outburst could be measured to be around 7.4(9)x10-13Hz s-1 ([7]).

The pulse profile of the source shows a strong energy dependance. At energies below 20 keV, the profile is dominated by a single, broad peak with a leading shoulder ([6]). For higher energies a secondary peak arises, which becomes more prominent with increasing energy. This behaviour can be explained by a polar cap diffusion model ([8]). Note, that this energy dependance is in contrast to other transient Be-binaries, like GRO J1008-57 or XTE J1946+274.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Cite error: Invalid <ref> tag; no text was provided for refs named Baykal00
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Cite error: Invalid <ref> tag; no text was provided for refs named Reig04
  3. 3.0 3.1 3.2 3.3 Cite error: Invalid <ref> tag; no text was provided for refs named Hulleman98
  4. Cite error: Invalid <ref> tag; no text was provided for refs named Reig03
  5. 5.0 5.1 Cite error: Invalid <ref> tag; no text was provided for refs named Blay04
  6. 6.0 6.1 6.2 Cite error: Invalid <ref> tag; no text was provided for refs named Inam04
  7. 7.0 7.1 7.2 Cite error: Invalid <ref> tag; no text was provided for refs named Baykal02
  8. Cite error: Invalid <ref> tag; no text was provided for refs named Falanga05