Millisecond Pulsations from a Low‐Mass X‐Ray Binary in the Galactic Center Region

Strohmayer, Tod E.; Jahoda, K.; Giles, A. B.; Lee, Umin

doi:10.1086/304522

Cited by 113 publications

(129 citation statements)

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“…During the burst, X-ray emission is often quasi-periodic (e.g., Strohmayer et al 1997a), possibly as a result of rotational modulation of the inhomogeneities in the burning matter. During the outburst the burning layer expands by a factor of about 10 (Joss 1978;Paczyński 1983) and according to Strohmayer et al (1997b) the subsequent contraction accounts for the observed frequency shifts. Heyl (2000) noticed that in calculating these frequency shifts one should take into account various relativistic effects such as the Lense-Thirring frame-dragging and the AbramowiczLasota (Abramowicz & Lasota 1974, 1986Barrabes et al 1995) centrifugal-force reversal.…”

Section: Introductionmentioning

confidence: 97%

The centrifugal force reversal and X-ray bursts

Abramowicz

Kluźniak

Lasota

2001

A&A

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Abstract. Heyl (2000) made an interesting suggestion that the observed shifts in QPO frequency in type I X-ray bursts could be influenced by the same geometrical effect of strong gravity as the one that causes centrifugal force reversal discovered by Abramowicz & Lasota (1974). However, his main result contains a sign error. Here we derive the correct formula and conclude that constraints on the M (R) relation for neutron stars deduced from the rotational-modulation model of QPO frequency shifts are of no practical interest because the correct formula implies a weak condition R * > 1.3RS, where RS is the Schwarzschild radius. We also argue against the relevance of the rotational-modulation model to the observed frequency modulations.

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Section: Introductionmentioning

confidence: 97%

The centrifugal force reversal and X-ray bursts

Abramowicz

Kluźniak

Lasota

2001

A&A

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“…Coherent (or near coherent) oscillations have been detected with RXTE in type I bursts from: 1636-53, 1728-34, KS1731-34, MXB1743-29, Aql X-l (see [14], [18], [19], [20]), and in 1702-43 (Swank, private communication). Not all bursts show these oscillations.…”

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confidence: 99%

“…In the case of 1728-34 the rotation period is then ~2.75 msec [14]; for 1636-53 and KS1731-260, the rotation frequencies are probably half the frequency observed in the type I bursts which translates into spin periods of ~3.45 msec and 3.82 msec, respectively (see [18], [20]). …”

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confidence: 99%

“…One would then expect to see the oscillations early on in a burst as has been observed (Strohmayer, private communication). However, it is puzzling why these oscillations in several cases have been observed only during the decay portion of the bursts (see [14], [19]), and, which is even more surprising, during the post contraction portion of bursts that showed radius expansion (see [14], [19], [20]). It is also not clear why in two sources the observed frequency in the type I bursts is twice that of the difference frequency between the HF and the LF peak.…”

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confidence: 99%

“…To assume the presence of two hot spots on the neutron star (resulting from a nuclear flash) seems abit ad hoc. The oscillations observed during the type I bursts can have very small drifts (<1.5 Hz) in frequency; it is unclear what causes these small drifts (see [16], [20] …”

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X-Ray Burst Sources

Lewin

1998

Highlights astron.

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For detailed reviews on X-ray burst sources, covering most information that was available prior to 1994, see [1].Since those reviews there have been very important new developments. First, a surprisingly new animal, GRO J1744-28 (better known as the Bursting Pulsar), made its debut in 1995. Second, but NOT last, in 1996/97 kHz pulsations were discovered in the persistent emission of several burst sources, and near coherent pulsations were detected in type I X-ray bursts.The Bursting Pulsar. GRO J1744-28 was discovered with BATSE on 1995 December 2, when over 80 hard X-ray bursts with durations of 10-30 s were detected [2]. The pulsar period is 467 ms, and pulsations are detected in the persistent emission and in the type II bursts (see [3], [4]). The pulsar is in a nearly circular orbit (e < 1.1 x 10~3) with an 11.8 day orbital period [3]. The very small X-ray mass function indicates that the companion is most likely a low-mass (M < 1M 0 ) star. GRO J1744-28 joins just 7 other pulsars detected in low-mass X-ray binary (LMXB) systems.The first major outburst of the source lasted from its discovery on 1995 December 2 until 1995 May. A less intense reactivation was observed during 1995 June-July. The beginning of a second major outburst was detected with BATSE on 1996 December 2, exactly one year after the first detection of the source [5]. The second large outburst is nearly a carbon-copy of the first. The long-term light curves show similar profiles. In both outbursts the rate of repetitive X-ray bursts was 150-200 per day (corrected for Earth occultation and live time) on the first day of activity; thereafter the rate settled down to 30-50 per day for the duration of the outburst [6].Observations with OSSE on CGRO showed that the phase of the 467 ms pulsations during and after bursts lags the phase prior to bursts by as much as 90 ms [7]. Observations with RXTE confirmed the pulse phase lags after bursts [8] and showed that the persistent emission following bursts is often depressed below its pre-burst level [9]. The RXTE PCA spectrum of the source is typical of X-ray pulsars [9]. The brightest bursts observed with RXTE in 1996 January had peak intensities of ~75 Crab (although this number is somewhat uncertain due to large dead time corrections). At an assumed distance of 7 kpc this corresponds to an assumed isotropic burst peak luminosity in excess of 50 Eddington luminosities! Kouveliotou et al. suggested that the repetitive bursts are caused by an instability in the accretion flow onto the neutron star [2]. A thermonuclear flash (type I X-ray burst) model for the repetitive bursts is excluded because the persistent X-ray emission during 1995 December 2 and 1996 December 2 was insufficient to account for the required replenishment of burnt fuel through accretion. The upper limits for the ratio, a, of the 20-100 keV persistent emission to the timeaveraged burst emission are a < 4 (3

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Millisecond X-Ray Pulsars and QPOs

Lamb

NATO Science Series II. Mathematics, Physics and Chemistry

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Millisecond Pulsations from a Low‐Mass X‐Ray Binary in the Galactic Center Region

Cited by 113 publications

References 17 publications

The centrifugal force reversal and X-ray bursts

The centrifugal force reversal and X-ray bursts

X-Ray Burst Sources

Millisecond X-Ray Pulsars and QPOs

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