EXOSAT observations of 4U 1705-44 - Type I bursts and persistent emission

Langmeier, A.; Sztajno, M.; Hasinger, G.; Truemper, J.; Gottwald, Manfred

doi:10.1086/165826

Cited by 52 publications

(42 citation statements)

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“…Its peak flux of 6 Â 10 À10 ergs cm À2 s À1 (2-8 keV) is a factor of 40 below those of Eddington-limited bursts observed previously from this source with the BeppoSAX WFC (10 À8 ergs cm À2 s À1 ). Faint bursts are not uncommon from LMXBs, but they are usually preceded by bright bursts tens of minutes before (e.g., Langmeier et al 1987;Gottwald et al 1986), and are thought to occur in fuel that was not burnt in the previous burst Fujimoto et al 1987). However, no burst was observed from GRS 1741.9À2853 in the 7 hr of Chandra observations prior to the weak burst, and the fluence of the burst (10 38 ergs) is an order of magnitude smaller than the amount of nuclear energy that could have been stored in accreted hydrogen during the Chandra observation prior to the burst (0:04 Â 2:5 Â 10 4 s Â 10 36 ergs s À1 ¼ 10 39 ergs; see Fig.…”

Section: Discussionmentioning

confidence: 99%

The X‐Ray Binary GRS 1741.9−2853 in Outburst and Quiescence

Muno¹,

Baganoff²,

Arabadjis³

2003

ApJ

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We report Chandra and XMM-Newton observations of the transient neutron star low-mass X-ray binary GRS 1741.9À2853. Chandra detected the source in outburst on 2000 October 26 at an X-ray luminosity of $10 36 ergs s À1 (2-8 keV; 8 kpc), and in quiescence on 2001 July 18 at $10 32 ergs s À1 . The latter observation is the first detection of GRS 1741.9À2853 in quiescence. We obtain an accurate position for the source of 17 h 45 m 29 33, À28 54 0 49>7 (J2000), with an uncertainty of 0>7. GRS 1741.9À2853 was not detected significantly in three other Chandra observations, nor in three XMM-Newton observations, indicating that the luminosity of the source in quiescence varies by at least a factor of 5 from (<0:9 5:0Þ Â 10 32 ergs s À1 (2-8 keV). A weak X-ray burst with a peak luminosity of 5 Â 10 36 ergs s À1 above the persistent level was observed with Chandra during the outburst on 2000 October 26. The energy of this burst, 10 38 ergs, is unexpectedly low and may suggest that the accreted material is confined to the polar caps of the neutron star. A search of the literature reveals that GRS 1741.9À2853 was observed in outburst with ASCA in the fall of 1996 as well, when the BeppoSAX WFC detected the three previous X-ray bursts from this source. The lack of X-ray bursts from GRS 1741.9À2853 at other epochs suggests that it produces bursts only during transient outbursts when the accretion rate onto the surface of the neutron star is about 10 À10 M yr À1 . A similar situation may hold for other low-luminosity bursters recently identified from WFC data.

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Section: Discussionmentioning

confidence: 99%

The X‐Ray Binary GRS 1741.9−2853 in Outburst and Quiescence

Muno¹,

Baganoff²,

Arabadjis³

2003

ApJ

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“…4U 1705-44 is an X-ray burster (Sztajno et al 1985;Langmeier et al 1987), whose bursting activity and frequency depends on persistent emission. The source is characterized by variability between low and high intensity states.…”

Section: Introductionmentioning

confidence: 99%

Broadband observations of the X-ray burster 4U1705-44 withBeppoSAX

Piraino

Santangelo

Mück

et al. 2016

A&A

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Context. 4U 1705-44 is one of the most-studied type I X-ray burster and Atoll sources. This source represents a perfect candidate to test different models proposed to self-consistently track the physical changes occurring between different spectral states because it shows clear spectral state transitions. Aims. The broadband coverage, the sensitivity and energy resolution of the BeppoSAX satellite offers the opportunity to disentangle the components that form the total X-ray spectrum and to study their changes according to the spectral state. Methods. Using two BeppoSAX observations carried out in August and October 2000, respectively, for a total effective exposure time of ∼100 ks, we study the spectral evolution of the source from a soft to hard state. Energy spectra are selected according to the source position in the color-color diagram (CCD). Results. We succeeded in modeling the spectra of the source using a physical self-consistent scenario for both the island and banana branches (the double Comptonization scenario). The components observed are the soft Comptonization and hard Comptonization, the blackbody, and a reflection component with a broad iron line. When the source moves from the banana state to the island state, the parameters of the two Comptonization components change significantly and the blackbody component becomes too weak to be detected. Conclusions. We interpret the soft Comptonization component as emission from the hot plasma surrounding the neutron star, hard Comptonization as emission from the disk region, and the blackbody component as emission from the inner accretion disk. The broad feature in the iron line region is compatible with reflection from the inner accretion disk.

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“…4U 1705−44 is a persistent bright source that shows type I X-ray burst (Langmeier et al 1987) and kHz quasi-periodic oscillations (Ford et al 1998;Olive et al 2003). From some bursts that show photospheric radius expansion, its distance is estimated at 7.4 kpc, toward the Galactic ridge (Forman et al 1978;Galloway et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Testing reflection features in 4U 1705−44 withXMM-Newton,BeppoSAX, and RXTE in the hard and soft states

Egron

Salvo

Motta

et al. 2013

A&A

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We use data from the bright atoll source 4U 1705−44 taken with XMM-Newton, BeppoSAX, and RXTE both in the hard and in the soft state to perform a self-consistent study of the reflection component in this source. Although the data from these X-ray observatories are not simultaneous, the spectral decomposition is shown to be consistent among the different observations, when the source flux is similar. We have therefore selected observations performed at similar flux levels in the hard and soft states to study the spectral shape in these two states in a broad-band (0.1−200 keV) energy range, with good energy resolution, and using self-consistent reflection models. These reflection models provide a good fit for the X-ray spectrum both in the hard and in the soft state in the whole spectral range. We discuss the differences in the main spectral parameters we find in both states, providing evidence that the inner radius of the optically thick disk slightly recedes in the hard state.

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EXOSAT observations of 4U 1705-44 - Type I bursts and persistent emission

Cited by 52 publications

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The X‐Ray Binary GRS 1741.9−2853 in Outburst and Quiescence

The X‐Ray Binary GRS 1741.9−2853 in Outburst and Quiescence

Broadband observations of the X-ray burster 4U1705-44 withBeppoSAX

Testing reflection features in 4U 1705−44 withXMM-Newton,BeppoSAX, and RXTE in the hard and soft states

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