Discovery of X‐Ray Burst Oscillations from a Neutron Star X‐Ray Transient in the Globular Cluster NGC 6440

Kaaret, Philip; Zand, J. J. M. in ’t; Heise, J.; Tomsick, John A.

doi:10.1086/375053

Cited by 27 publications

(25 citation statements)

References 24 publications

(40 reference statements)

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“…We searched for, but did not detect, oscillations at 410 Hz in SAX J1748.9À2021 (as claimed by Kaaret et al 2003); this source has subsequently exhibited intermittent persistent pulsations at 442 Hz (Gavriil et al 2007;Altamirano et al 2008), strongly suggesting the earlier detection was spurious. We also made a targeted search around 1122 Hz for the bursts from XTE J1739À285, without success (cf.…”

Section: Thermonuclear X-ray Bursts Observed By Rxtementioning

confidence: 78%

“…A similar burst observed with the narrow-field instruments reached a peak flux of 1:7 ; 10 À8 ergs cm À2 s À1 . No bursts were detected by RXTE during the 1998 outburst, but observations during the 2001 outburst revealed 16 bursts, one of which exhibited weak evidence for burst oscillations at 409.7 Hz ( Kaaret et al 2003). A subsequent outburst was detected in PCA scans of the Galactic bulge region on 2005 May 12Y16 ( Markwardt & Swank 2005a).…”

Section: A29 1a 1744à361mentioning

confidence: 99%

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Thermonuclear (Type I) X‐Ray Bursts Observed by theRossi X‐Ray Timing Explorer

Galloway

Muno

Hartman

et al. 2008

Astrophysical Journal Supplement Series, The

659

1,177

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We have assembled a sample of 1187 thermonuclear (type I) X-ray bursts from observations of 48 accreting neutron stars by the Rossi X-ray Timing Explorer, spanning more than 10 years. The sample contains examples of two of the three theoretical ignition regimes (confirmed via comparisons with numerical models) and likely examples of the third. We present a detailed analysis of the variation of the burst profiles, energetics, recurrence times, presence of photospheric radius expansion, and presence of burst oscillations, as a function of accretion rate. We estimated the distance for 35 sources exhibiting radius-expansion bursts, and found that the peak flux of such bursts varies typically by 13%. We classified sources into two main groups based on the burst properties: (1) both long and short bursts (indicating mixed H/ He accretion), and (2) consistently short bursts (primarily He accretion), and we calculated the mean burst rate as a function of accretion rate for the two groups. The decrease in burst rate observed at >0:06Ṁ Edd (k2 ; 10 37 ergs s À1) is associated with a transition in the persistent spectral state and (as has been suggested previously) may be related to the increasing role of steady He burning. We found many examples of bursts with recurrence times <30 minutes, including burst triplets and even quadruplets. We describe the oscillation amplitudes for 13 of the 16 burst oscillation sources, as well as the stages and properties of the bursts in which the oscillations are detected. The burst properties are correlated with the burst oscillation frequency; sources spinning at <400 Hz generally have consistently short bursts, while the more rapidly spinning systems have both long and short bursts. This correlation suggests either that shear-mediated mixing dominates the burst properties, or alternatively that the nature of the mass donor (and hence the evolutionary history) has an influence on the long-term spin evolution.

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Section: Thermonuclear X-ray Bursts Observed By Rxtementioning

confidence: 78%

Section: A29 1a 1744à361mentioning

confidence: 99%

Thermonuclear (Type I) X‐Ray Bursts Observed by theRossi X‐Ray Timing Explorer

Galloway

Muno

Hartman

et al. 2008

Astrophysical Journal Supplement Series, The

659

1,177

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“…The one which is not a faint transient (XTE J1751-305; peak X-ray luminosities of a few times 10 37 erg s −1 ) had a very short outburst duration (e-folding time of only ∼7 days) resulting in a low time-averaged accretion rate similar to the other accreting millisecond pulsars. but later it was found to also exhibit bright X-ray outbursts (Kaaret et al 2003). Furthermore, the bright neutron star X-ray transient SAX J1747.0-2853 (e.g., Werner et al 2004) was seen on several occasions at luminosities of only a few times 10 35 erg s −1 (e.g., Wijnands et al 2002).…”

Section: Classifying the X-ray Transientsmentioning

confidence: 98%

TheXMM-Newton/Chandramonitoring campaign of the Galactic center region

Wijnands

Zand²,

Rupen

et al. 2006

A&A

129

192

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We present the first results of our X-ray monitoring campaign on a 1.7 square degree region centered on Sgr A* using the satellites XMM-Newton and Chandra. The purpose of this campaign is to monitor the behavior (below 10 keV) of X-ray sources (both persistent and transient) which are too faint to be detected by monitoring instruments aboard other satellites currently in orbit (e.g., Rossi X-ray Timing Explorer; INTEGRAL). Our first monitoring observations (using the HRC-I aboard Chandra) were obtained on June 5, 2005. Most of the sources detected could be identified with foreground sources, such as X-ray active stars. In addition we detected two persistent X-ray binaries (1E 1743.1-2843; 1A 1742-294), two faint X-ray transients (GRS 1741.9-2853; XMM J174457-2850.3), as well as a possible new transient source at a luminosity of a few times 10 34 erg s −1 . We report on the X-ray results on these systems and on the non-detection of the transients in follow-up radio data using the Very Large Array. We discuss how our monitoring campaign can help to improve our understanding of the different types of X-ray transients (i.e., the very faint ones).

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“…NGC 6440 harbors the bright X-ray transient SAX J1748.9Ϫ2021, from which Kaaret et al (2003) claimed a detection of burst oscillations at 409.7 Hz. However, there are many other X-ray sources in the cluster (see Fig.…”

Section: The Ngc 6440 Fieldmentioning

confidence: 99%

Discovery of 442 Hz Pulsations from an X-Ray Source in the Globular Cluster NGC 6440

Gavriil

Strohmayer

Swank

et al. 2007

ApJ

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We report on the serendipitous discovery of a 442 Hz pulsar during a Rossi X-Ray Timing Explorer (RXTE) observation of the globular cluster NGC 6440. The oscillation is detected following a burstlike event which was decaying at the beginning of the observation. The timescale of the decay suggests we may have seen the tail end of a long-duration burst. Low-mass X-ray binaries (LMXBs) are known to emit thermonuclear X-ray bursts that are sometimes modulated by the spin frequency of the star, the so-called burst oscillations. The pulsations reported here are peculiar if interpreted as canonical burst oscillations. In particular, the pulse train lasted for ∼500 s, much longer than in standard burst oscillations. The signal was highly coherent and drifted down by ∼2 # 10 Ϫ3 Hz, much smaller than the ∼Hz drifts typically observed during normal bursts, but consistent with orbital motion of the neutron star. The pulsations are reminiscent of those observed during the much more energetic "superbursts"; however, the temporal profile and the energetics of the burst suggest that it was not the tail end nor the precursor feature of a superburst. Rather, it is likely that we caught a portion of an outburst from a new "intermittent" accreting millisecond pulsar, a phenomenon which until now had only been seen in HETE J1900.1Ϫ2455.

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Discovery of X‐Ray Burst Oscillations from a Neutron Star X‐Ray Transient in the Globular Cluster NGC 6440

Cited by 27 publications

References 24 publications

Thermonuclear (Type I) X‐Ray Bursts Observed by theRossi X‐Ray Timing Explorer

Thermonuclear (Type I) X‐Ray Bursts Observed by theRossi X‐Ray Timing Explorer

TheXMM-Newton/Chandramonitoring campaign of the Galactic center region

Discovery of 442 Hz Pulsations from an X-Ray Source in the Globular Cluster NGC 6440

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