Energy Spectra and High-Frequency Oscillations in 4U 0614+091

Ford, Eric; Kaaret, Philip; Chen, K.; Tavani, M.; Barret, D.; Bloser, Peter F.; Grindlay, J.; Harmon, B. A.; Pačiesas, W. S.; Zhang, S. N.

doi:10.1086/310827

Cited by 52 publications

(46 citation statements)

References 22 publications

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“…Kaaret et al (1998) described certain correlations in the atoll sources (neutron star binaries) 4U 0614+091 and 4U 1608À52 that might also be due to independent disk and halo flows. In those sources, the frequency of the kilohertz quasi-periodic oscillations (QPOs) correlates well with the power-law index (Kaaret et al 1998) and, for 4U 0614+091, with the disk blackbody flux (Ford et al 1997). Neither these sources, nor the kilohertz QPO sources in general, show a long-term correlation between QPO frequency and luminosity.…”

Section: Discussionmentioning

confidence: 94%

Two Different Long‐Term Behaviors in Black Hole Candidates: Evidence for Two Accretion Flows?

Smith

Heindl

Swank

2002

ApJ

189

178

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We discuss the results of long-term hard X-ray monitoring of Galactic black hole candidates 1E 1740.7À2942, GRS 1758À258, Cyg X-1, GX 339À4, and Cyg X-3 with the Rossi X-Ray Timing Explorer. The objects divide into two classes. In the first class, exemplified by Cyg X-1, luminosity and spectral hardness evolve simultaneously. In the second class, the relation is more complicated: the softest spectra occur while the count rate is dropping. Most models of accretion, tailored to Cyg X-1, do not predict the second sort of behavior. One interpretation is a simple model with two simultaneous, independent accretion flows: a thin disk and a hot halo. A drop in the accretion rate affecting both flows would propagate through the halo immediately but might take up to several weeks to propagate through the disk. While the inner halo is thus temporarily depleted compared to the disk, a temporary soft state is expected. This picture is supported by the observation that those sources that show delays (1E 1740.7À2942, GRS 1758À258, and GX 339À4) are expected to have low-mass companions, and those that do not (Cyg X-1, Cyg X-3) are known or thought to have high-mass companions. Low-mass companions imply accretion by Roche lobe overflow, with a high specific angular momentum in the accreting material, and therefore a large disk with a long viscous timescale. Wind accretion from massive companions is expected to result in a much smaller disk and thus little viscous delay.

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Section: Discussionmentioning

confidence: 94%

Two Different Long‐Term Behaviors in Black Hole Candidates: Evidence for Two Accretion Flows?

Smith

Heindl

Swank

2002

ApJ

189

178

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“…Generally, for 4U 0614+091 photon indices for the power-law component are found to be between 2 and 3 and temperatures for the soft blackbody component are between kT = 0.5 and 1.5 keV. Total fluxes (1−20 keV) are typically between 1 and 5 × 10 −9 erg s −1 cm −2 (Barret & Grindlay 1995;Ford et al 1996Ford et al , 1997; see also Piraino et al 1999;Fiocchi et al 2008). Our four most accurate measurements for these components are provided in Table 3.…”

Section: Persistent Emissionmentioning

confidence: 99%

What ignites on the neutron star of 4U 0614+091?

Kuulkers¹,

Zand

Atteia

et al. 2010

A&A

103

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The low-mass X-ray binary 4U 0614+091 is a source of sporadic thermonuclear (type I) X-ray bursts. We find bursts with a wide variety of characteristics in serendipitous wide-field X-ray observations by the WATCH on EURECA, the ASM on RXTE, the WFCs on BeppoSAX, the FREGATE on HETE-2, the IBIS/ISGRI on INTEGRAL, and the BAT on Swift, as well as pointed observations with the PCA and HEXTE on RXTE. Most of the bursts are bright, i.e., they reach a peak flux of about 15 Crab, but a few are weak and only reach a peak flux below a Crab. One of the bursts shows a very strong photospheric radius-expansion phase. This allows us to evaluate the distance to the source, which we estimate to be 3.2 kpc. The burst durations vary generally from about 10 s to 5 min. However, after one of the intermediate-duration bursts, a faint tail is seen to at least about 2.4 h after the start of the burst. One very long burst was observed, which lasted for several hours. This superburst candidate was followed by a normal type-I burst only 19 days later. This is, to our knowledge, the shortest burst-quench time among the superbursters. The observation of a superburst in this system is difficult to reconcile if the system is accreting at about 1% of the Eddington limit. We describe the burst properties in relation to the persistent emission. No strong correlations are apparent, except that the intermediate-duration bursts occurred when 4U 0614+091's persistent emission was lowest and calm, and when bursts were infrequent (on average roughly one every month to 3 months). The average burst rate increased significantly after this period. The maximum average burst recurrence rate is about once every week to 2 weeks. The burst behaviour may be partly understood if there is at least an appreciable amount of helium present in the accreted material from the donor star. If the system is an ultra-compact X-ray binary with a CO white-dwarf donor, as has been suggested, this is unexpected. If the bursts are powered by helium, we find that the energy production per accumulated mass is about 2.5 times less than expected for pure helium matter.

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“…The spectra of these sources sometimes show a cutoff of 50-60 keV, but not always, and may extend to higher energy. Comparisons with soft X-ray measurements indicate that these sources exhibit anticorrelations between X-ray luminosity and spectral hardness (van Paradijs & van der Klis 1994; Ford et al 1997), and thus, as in BHCs, spectral behavior of the LMXB NS systems should be governed by mass accretion rate. Whether or not NS binaries have equivalent spectral states to BH binaries is not clear, but these observations support the picture of a neutron star surrounded by an accretion disk as in BH systems, differing only at the innermost regions of the disk.…”

Section: Low-mass X-ray Binaries With Neutron Starsmentioning

confidence: 99%

The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low‐Energy Gamma‐Ray Sources

Harmon

Wilson

Fishman

et al. 2004

ASTROPHYS J SUPPL S

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The Burst and Transient Source Experiment (BATSE), aboard the Compton Gamma Ray Observatory (CGRO), provided a record of the low-energy gamma-ray sky ($20-1000 keV) between 1991 April and 2000 May (9.1 yr).BATSE monitored the high-energy sky using the Earth occultation technique (EOT) for point sources whose emission extended for times on the order of the CGRO orbital period ($92 min) or greater. Using the EOT to extract flux information, a catalog of sources using data from the BATSE Large Area Detectors has been prepared. The first part of the catalog consists of results from the all-sky monitoring of 58 sources, mostly Galactic, with intrinsic variability on timescales of hours to years. For these sources, we have included tables of flux and spectral data, and outburst times for transients. Light curves (or flux histories) have been placed on the World Wide Web.We then performed a deep-sampling of these 58 objects, plus a selection of 121 more objects, combining data from the entire 9.1 yr BATSE data set. Source types considered were primarily accreting binaries, but a small number of representative active galaxies, X-ray-emitting stars, and supernova remnants were also included. The sample represents a compilation of sources monitored and/or discovered with BATSE and other high-energy instruments between 1991 and 2000, known sources taken from the HEAO 1 A-4 and Macomb & Gehrels catalogs. The deep sample results include definite detections of 83 objects and possible detections of 36 additional objects. The definite detections spanned three classes of sources: accreting black hole and neutron star binaries, active galaxies, and supernova remnants. The average fluxes measured for the fourth class, the X-ray emitting stars, were below the confidence limit for definite detection.Flux data for the deep sample are presented in four energy bands: 20-40, 40-70, 70-160, and 160-430 keV. The limiting average flux level (9.1 yr) for the sample varies from 3.5 to 20 mcrab (5 ) between 20 and 430 keV, depending on systematic error, which in turn is primarily dependent on the sky location.To strengthen the credibility of detection of weaker sources ($5-25 mcrab), we generated Earth occultation images, searched for periodic behavior using FFT and epoch folding methods, and critically evaluated the energy-dependent emission in the four flux bands. The deep sample results are intended for guidance in performing future all-sky surveys or pointed observations in the hard X-ray and low-energy gamma-ray band, as well as more detailed studies with the BATSE EOT.

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Energy Spectra and High-Frequency Oscillations in 4U 0614+091

Cited by 52 publications

References 22 publications

Two Different Long‐Term Behaviors in Black Hole Candidates: Evidence for Two Accretion Flows?

Two Different Long‐Term Behaviors in Black Hole Candidates: Evidence for Two Accretion Flows?

What ignites on the neutron star of 4U 0614+091?

The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low‐Energy Gamma‐Ray Sources

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