arXiv subjects

Peter G. Jonker

Publications and source records attributed to Peter G. Jonker.

At least 73 records · Page 4Linked to original sources

arXiv2017

X-ray Binaries

This chapter discusses the implications of X-ray binaries on our knowledge of Type Ibc and Type II supernovae. X-ray binaries contain accreting neutron stars and stellar--mass black holes which are the end points of massive star evolution. Studying these remnants thus provides clues to understanding the evolutionary processes that lead to their formation. We focus here on the distributions of dynamical masses, space velocities and chemical anomalies of their companion stars. These three observational features provide unique information on the physics of core collapse and supernovae explosions within interacting binary systems. There is suggestive evidence for a gap between ~2-5 Msun in the observed mass distribution. This might be related to the physics of the supernova explosions although selections effects and possible systematics may be important. The difference between neutron star mass measurements in low-mass X-ray binaries (LMXBs) and pulsar masses in high-mass X-ray binaries (HMXBs) reflect their different accretion histories, with the latter presenting values close to birth masses. On the other hand, black holes in LMXBs appear to be limited to <~12 Msun because of strong mass-loss during the wind Wolf-Rayet phase. Detailed studies of a limited sample of black-hole X-ray binaries suggest that the more massive black holes have a lower space velocity, which could be explained if they formed through direct collapse. Conversely, the formation of low-mass black holes through a supernova explosion implies that large escape velocities are possible through ensuing natal and/or Blaauw kicks. Finally, chemical abundance studies of the companion stars in seven X-ray binaries indicate they are metal-rich (all except GRO J1655-40) and possess large peculiar abundances of alpha-elements (Abridged)

astro-ph.HE↗

arXiv2016

A radio jet from the optical and x-ray bright stellar tidal disruption flare ASASSN-14li

The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly-launched jet. The multi-wavelength properties of the source present a natural analogy with accretion state changes of stellar mass black holes, suggesting all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection.

astro-ph.HE↗

arXiv2015

A Dynamical Study of the Black Hole X-ray Binary Nova Muscae 1991

We present a dynamical study of the Galactic black hole binary system Nova Muscae 1991 (GS/GRS 1124-683). We utilize 72 high resolution Magellan Echellette (MagE) spectra and 72 strictly simultaneous V-band photometric observations; the simultaneity is a unique and crucial feature of this dynamical study. The data were taken on two consecutive nights and cover the full 10.4-hour orbital cycle. The radial velocities of the secondary star are determined by cross-correlating the object spectra with the best-match template spectrum obtained using the same instrument configuration. Based on our independent analysis of five orders of the echellette spectrum, the semi-amplitude of the radial velocity of the secondary is measured to be K_2 = 406.8+/-2.7 km/s, which is consistent with previous work, while the uncertainty is reduced by a factor of 3. The corresponding mass function is f(M) = 3.02+/-0.06 M_\odot. We have also obtained an accurate measurement of the rotational broadening of the stellar absorption lines (v sin i = 85.0+/-2.6 km/s) and hence the mass ratio of the system q = 0.079+/-0.007. Finally, we have measured the spectrum of the non-stellar component of emission that veils the spectrum of the secondary. In a future paper, we will use our veiling-corrected spectrum of the secondary and accurate values of K_2 and q to model multi-color light curves and determine the systemic inclination and the mass of the black hole.

astro-ph.HE↗

arXiv2015

A Clean Sightline to Quiescence: Multiwavelength Observations of the High Galactic Latitude Black Hole X-ray Binary Swift J1357.2-0933

We present coordinated multiwavelength observations of the high Galactic latitude (b=+50 deg) black hole X-ray binary (XRB) J1357.2-0933 in quiescence. Our broadband spectrum includes strictly simultaneous radio and X-ray observations, and near-infrared, optical, and ultraviolet data taken 1-2 days later. We detect Swift J1357.2-0933 at all wavebands except for the radio (f_5GHz < 3.9 uJy/beam). Given current constraints on the distance (2.3-6.3 kpc), its 0.5-10 keV X-ray flux corresponds to an Eddington ratio Lx/Ledd = 4e-9 -- 3e-8 (assuming a black hole mass of 10 Msun). The broadband spectrum is dominated by synchrotron radiation from a relativistic population of outflowing thermal electrons, which we argue to be a common signature of short-period quiescent BHXBs. Furthermore, we identify the frequency where the synchrotron radiation transitions from optically thick-to-thin (approximately 2-5e14 Hz, which is the most robust determination of a 'jet break' for a quiescent BHXB to date. Our interpretation relies on the presence of steep curvature in the ultraviolet spectrum, a frequency window made observable by the low amount of interstellar absorption along the line of sight. High Galactic latitude systems like Swift J1357.2-0933 with clean ultraviolet sightlines are crucial for understanding black hole accretion at low luminosities.

astro-ph.HE↗

arXiv2015

Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant X-Ray Light Echo

Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up observations with Chandra and XMM-Newton from 40 to 80 days after the flare reveal a bright X-ray light echo in the form of four well-defined rings with radii from 5 to 13 arcminutes, growing in radius with time. The large fluence of the flare and the large column density of interstellar dust towards Circinus X-1 make this the largest and brightest set of rings from an X-ray light echo observed to date. By deconvolving the radial intensity profile of the echo with the MAXI X-ray lightcurve of the flare we reconstruct the dust distribution towards Circinus X-1 into four distinct dust concentrations. By comparing the peak in scattering intensity with the peak intensity in CO maps of molecular clouds from the Mopra Southern Galactic Plane CO Survey we identify the two innermost rings with clouds at radial velocity ~ -74 km/s and ~ -81 km/s, respectively. We identify a prominent band of foreground photoelectric absorption with a lane of CO gas at ~ -32 km/s. From the association of the rings with individual CO clouds we determine the kinematic distance to Circinus X-1 to be $D_{Cir X-1} = 9.4^{+0.8}_{-1.0}$ kpc. This distance rules out earlier claims of a distance around 4 kpc, implies that Circinus X-1 is a frequent super-Eddington source, and places a lower limit of $Γ\gtrsim 22$ on the Lorentz factor and an upper limit of $θ_{jet} \lesssim 3^{\circ}$ on the jet viewing angle.

astro-ph.HE↗

arXiv2014

Constraints on Relativistic Jets in Quiescent Black Hole X-ray Binaries from Broadband Spectral Modeling

The nature of black hole jets at the lowest detectable luminosities remains an open question, largely due to a dearth of observational constraints. Here, we present a new, nearly-simultaneous broadband spectrum of the black hole X-ray binary (BHXB) XTE J1118+480 at an extremely low Eddington ratio (L_x~1e-8.5 L_Edd). Our new spectral energy distribution (SED) includes the radio, near-infrared, optical, ultraviolet, and X-ray wavebands. XTE J1118 is now the second BHXB at such a low Eddington ratio with a well-sampled SED, providing new constraints on highly sub-Eddington accretion flows and jets, and opening the door for comparison studies. We apply a multi-zone jet model to the new broadband SED, and we compare our results to previous fits to the same source using the same model at 4-5 decades higher luminosity. We find that after a BHXB transitions to the so-called quiescent spectral state, the jet base becomes more compact (by up to an order of magnitude) and slightly cooler (by at least a factor of two). Our preferred model fit indicates that jet particle acceleration is weaker after the transition into quiescence. That is, accelerated non-thermal particles no longer reach high enough Lorentz factors to contribute significant amounts of synchrotron X-ray emission. Instead, the X-ray waveband is dominated by synchrotron self-Compton emission from a population of mildly relativistic electrons with a quasi-thermal velocity distribution associated with the jet base. The corresponding (thermal) synchrotron component emits primarily in the infrared through ultraviolet wavebands. Our results on XTE J1118 are consistent with broadband modeling for A0620-00 and for Sgr A*. The above could therefore represent a canonical baseline geometry for accreting black holes in quiescence. We conclude with suggestions for future studies to further investigate the above scenario.

astro-ph.HE↗

arXiv2013

The Galactic Bulge Survey: completion of the X-ray survey observations

We provide the Chandra source list for the last ~quarter of the area covered by the Galactic Bulge Survey (GBS). The GBS targets two strips of 6\degr x 1\degr (12 square degrees in total), one above (1\degr<b<2\degr) and one below (-2\degr<b<-1\degr) the Galactic plane in the direction of the Galactic Center at X-ray, optical and near-infrared wavelengths. For the X-ray part of the survey we use 2 ks per Chandra pointing. We find 424 X-ray sources in the 63 Chandra observations we report on here. These sources are in addition to the 1216 X-ray sources discovered in the first part of the GBS survey described before. We discuss the characteristics and the X-ray variability of the brightest of the sources as well as the radio properties from existing radio surveys. We point out an interesting asymmetry in the number of X-ray sources as a function of their Galactic l and b coordinates which is probably caused by differences in average extinction towards the different parts of the GBS survey area.

astro-ph.HE↗

arXiv2013

V4641 Sgr: a candidate precessing microblazar

The X-ray spectrum of the Galactic X-ray binary V4641 Sgr in outburst has been found to exhibit a remarkably broad emission feature above 4 keV, with inferred equivalent widths up to 2 keV. Such a feature was first detected during the X-ray flaring activity associated with the giant outburst that the source experienced in 1999 September. The extraordinarily large equivalent width line was then ascribed to reflection/reprocessing of fluorescent Fe emission within an extended optically thick outflow enshrouding the binary system as a result of a short-lived, super-Eddington accretion episode. Making use of new and archival X-ray observations, we show here that a similar feature persists over four orders of magnitude in luminosity, down to Eddington ratios as low as log(L_Edd) = -4.5, where the existence of an optically thick envelope appears at odds with any viable accretion flow model. Possible interpretations for this highly unusual X-ray spectrum include a blend of Doppler shifted/boosted Fe lines from unresolved X-ray jets (a la SS433), or, the first Galactic analog of a blazar spectrum, where the >4 keV emission would correspond to the onset of the Inverse Compton hump. Either requires a low inclination angle of the jet with respect to the line of sight, in agreement with the estimates for the 1999 superluminal jet (i_jet<10 deg). The fast variability of the feature, combined with the high orbital axis inclination (60 deg< i_orb<71 deg), argue for a rapidly precessing accretion flow around V4641 Sgr, possibly leading to a transient microblazar behavior.

astro-ph.HE↗

arXiv2013

The X-ray properties of the black hole transient MAXI J1659-152 in quiescence

We present new Chandra X-ray observations of the transient black hole X-ray binary MAXI J1659-152 in quiescence. These observations were made more than one year after the end of the source's 2010-2011 outburst. We detect the source at a 0.5-10 keV flux of 2.8(8)e-15 erg/cm^2/s, which corresponds to a luminosity of ~1.2e31 (d/ 6 kpc)^2 erg/s. This level, while being the lowest at which the source has been detected, is within factors of ~2 of the levels seen at the end of the initial decay of the outburst and soon after a major reflare of the source. The quiescent luminosity of MAXI J1659-152, which is the shortest-orbital-period black hole X-ray binary (~2.4 hr), is lower than that of neutron-star X-ray binaries with similar periods. However, it is higher than the quiescent luminosities found for black hole X-ray binaries with orbital periods ~2-4 times longer. This could imply that a minimum quiescent luminosity may exist for black hole X-ray binaries, around orbital periods of ~5-10 hr, as predicted by binary-evolution models for the mass transfer rate. Compared to the hard state we see a clear softening of the power-law spectrum in quiescence, from an index of 1.55(4) to an index of 2.5(4). We constrain the luminosity range in which this softening starts to fractional Eddington luminosities of (0.18-6.2)e-5 (d/ 6 kpc)^2 (M/ 8 Msun), which is consistent with the ranges inferred for other sources.

astro-ph.HE↗

arXiv2013

The X-ray Spectral Evolution of Galactic Black Hole X-ray Binaries Toward Quiescence

Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio l_x = L_{0.5-10 keV}}/L_{Edd} < 1e-5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index and l_x in the low-hard state does not continue once a BHXB enters quiescence. Instead, the photon index plateaus to an average value of 2.08+/-0.07 by the time l_x reaches approximately 1e-5. l_x~1e-5 is thus an observationally-motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models, and across the black hole mass scale.

astro-ph.HE↗

arXiv2012

Chandra X-ray and Gemini near-infrared observations of the eclipsing msec pulsar SWIFT J1749.4-2807 in quiescence

We report on Chandra X-ray and Gemini-North near-infrared K-band observations of the eclipsing accretion-powered millisecond X-ray pulsar SWIFT J1749.4-2807 in quiescence. Using the Chandra observation we derive a source position of Right Ascencion: 17:49:31.73 and Declination:-28:08:05.08. The position is accurate to 0.6" (90 per cent confidence). We find one source at a magnitude K=18.44+-0.03 with a position fully consistent with the accurate Chandra X-ray localization and a second source at K=19.2+-0.1 that falls close to the edge of the error circle in the deep K-band images. The presence of a few weaker sources as suggested by previous H-band observations presented in the literature cannot the ruled out. There is marginal evidence that the brighter of the these two sources is variable. Follow-up spectroscopy of this potential counterpart will show if this source is the true counterpart to SWIFT J1749.4-2807. If so, baring the presence of complicating effects such as heating of the mass-donor star, it would allow for the mass of the neutron star to be measured through the measurement of periodic radial velocity variations.

astro-ph.HE↗

arXiv2012

The black hole candidate MAXIJ1659-152 in and towards quiescence in X-ray and radio

In this paper we report on Expanded Very Large Array radio and Chandra and Swift X-ray observations of the outburst decay of the transient black hole candidate MAXI J1659-152 in 2011. We discuss the distance to the source taking the high inclination into account and we conclude that the source distance is probably 6+-2 kpc. The lowest observed flux corresponds to a luminosity of 2x10^31 (d/6 kpc)^2 erg/s This, together with the orbital period of 2.4 hr reported in the literature, suggests that the quiescent X-ray luminosity is higher than predicted on the basis of the orbital period -- quiescent X-ray luminosity relationship. The relation between the accretion and ejection mechanisms can be studied using the observed correlation between the radio and X-ray luminosities as these evolve over an outburst. We determine the behaviour of MAXI J1659-152 in the radio -- X-ray diagram at low X-ray luminosities using the observations reported in this paper and at high X-ray luminosities using values reported in the literature. At high X-ray luminosities the source lies closer to the sources that follow a correlation index steeper than 0.6-0.7. However, when compared to other sources that follow a steeper correlation index, the X-ray luminosity in MAXI J1659-152 is also lower. The latter can potentially be explained by the high inclination of MAXI J1659-152 if the X-ray emission comes from close to the source and the radio emission is originating in a more extended region. However, it is probable that the source was not in the canonical low-hard state during these radio observations and this may affect the behaviour of the source as well. At intermediate X-ray luminosities the source makes the transition from the radio underluminous sources in the direction of the relation traced by the 'standard' correlation similar to what has been reported for H1743-322. (abridged)

astro-ph.HE↗

arXiv2009

Linking jet emission and X-ray properties in the peculiar neutron star X-ray binary Circinus X-1

We present the results of simultaneous X-ray and radio observations of the peculiar Z-type neutron star X-ray binary Cir X-1, observed with the Rossi X-ray timing explorer satellite and the Australia Telescope Compact Array in 2000 October and 2002 December. We identify typical Z source behaviour in the power density spectra as well as characteristic Z patterns drawn in an X-ray hardness-intensity diagram. Power spectra typical of bright atoll sources have also been identified at orbital phases after the periastron passage, while orbital phases before the periastron passage are characterized by power spectra that are typical neither of Z nor of atoll sources. We investigate the coupling between the X-ray and the radio properties, focusing on three orbital phases when an enhancement of the radio flux density has been detected, to test the link between the inflow (X-ray) and the outflow (radio jet) to/from the compact object. In two out of three cases we associate the presence of the radio jet to a spectral transition in the X-rays, although the transition does not precede the radio flare, as detected in other Z sources. An analogous behaviour has recently been found in the black hole candidate GX 339-4. In the third case, the radio light curve shows a similar shape to the X-ray light curve. We discuss our results in the context of jet models, considering also black hole candidates.

astro-ph.HE↗

arXiv2007

The cold neutron star in the soft X-ray transient 1H 1905+000

We report on our analysis of 300 ks of Chandra observations of the neutron star soft X-ray transient 1H1905+000 in quiescence. We do not detect the source down to a 95% confidence unabsorbed flux upper limit of 2E-16 erg cm-2 s-1 in the 0.5-10 keV energy range for an assumed Gamma=2 power law spectral model. A limit of 1.4E-16 erg cm-2 s-1 is derived if we assume that the spectrum of 1H1905+000 in quiescence is described well with a black body of temperature of 0.2 keV. For the upper limit to the source distance of 10 kpc this yields a 0.5-10 keV luminosity limit of 2.4E30 / 1.7E30 erg/s for the abovementioned power law or black body spectrum, respectively. This luminosity limit is lower than the luminosity of A0620-00, the weakest black hole soft X-ray transient in quiescence reported so far. Together with the uncertainties in relating the mass transfer and mass accretion rates we come to the conclusion that the claim that there is evidence for the presence of a black hole event horizon on the basis of a lower quiescent luminosity for black holes than for neutron stars is unproven. We also briefly discuss the implications of the low quiescent luminosity of 1H1905+000 for the neutron star equation of state. Using deep Magellan images of the field of 1H1905+000 obtained at excellent observing conditions we do not detect the quiescent counterpart at the position of the outburst optical counterpart down to a magnitude limit of i'>25.3. This can be converted to a limit on the absolute magnitude of the counterpart of I>9.6 which implies that the counterpart can only be a brown or a white dwarf.

astro-ph↗

arXiv2005

The X-ray Position and Optical Counterpart of the Accretion-Powered Millisecond Pulsar XTE J1814-338

We report the precise optical and X-ray localization of the 3.2 ms accretion-powered X-ray pulsar XTE J1814-338 with data from the Chandra X-Ray Observatory as well as optical observations conducted during the 2003 June discovery outburst. Optical imaging of the field during the outburst of this soft X-ray transient reveals an R = 18 star at the X-ray position. This star is absent (R > 20) from an archival 1989 image of the field and brightened during the 2003 outburst, and we therefore identify it as the optical counterpart of XTE J1814-338. The best source position derived from optical astrometry is R.A. = 18h13m39.s04, Dec.= -33d46m22.3s (J2000). The featureless X-ray spectrum of the pulsar in outburst is best fit by an absorbed power-law (with photon index = 1.41 +- 0.06) plus blackbody (with kT = 0.95 +- 0.13 keV) model, where the blackbody component contributes approximately 10% of the source flux. The optical broad-band spectrum shows evidence for an excess of infrared emission with respect to an X-ray heated accretion disk model, suggesting a significant contribution from the secondary or from a synchrotron-emitting region. A follow-up observation performed when XTE J1814-338 was in quiescence reveals no counterpart to a limiting magnitude of R = 23.3. This suggests that the secondary is an M3 V or later-type star, and therefore very unlikely to be responsible for the soft excess, making synchroton emission a more reasonable candidate.

astro-ph↗

arXiv2004

X-ray variability during the quiescent state of the neutron-star X-ray transient in the globular cluster NGC 6440

The globular cluster NGC 6440 is known to harbor a bright neutron-star X-ray transient. We observed the globular cluster with Chandra on two occasions when the bright transient was in its quiescent state in July 2000 and June 2003 (both observations were made nearly 2 years after the end of their preceding outbursts). The quiescent spectrum during the first observation is well represented by a two component model (a neutron-star atmosphere model plus a power-law component which dominates at energies above 2 keV). During the second observation (which was roughly of equal duration to the first observation) we found that the power-law component could no longer be detected. Our spectral fits indicate that the effective temperature of the neutron-star surface was consistent between the two observations. We conclude that the effect of the change in power-law component caused the 0.5-10 keV flux to be a factor of ~2 lower during the second observation compared to the first observation. We discuss plausible explanations for the variations, including variable residual accretion onto the neutron star magnetosphere or some variation in the interaction of the pulsar wind with the matter still outflowing from the companion star.

astro-ph↗

arXiv2004

The hard quiescent spectrum of the neutron-star X-ray transient EXO 1745-248 in the globular cluster Terzan 5

We present a Chandra observation of the globular cluster Terzan 5 during times when the neutron-star X-ray transient EXO 1745-248 located in this cluster was in its quiescent state. We detected the quiescent system with a (0.5-10 keV) luminosity of ~2 x 10^{33} ergs/s. This is similar to several other neutron-star transients observed in their quiescent states. However, the quiescent X-ray spectrum of EXO 1745--48 was dominated by a hard power-law component instead of the soft component that usually dominates the quiescent emission of other neutron-star X-ray transients. This soft component could not conclusively be detected in EXO 1745-248 and we conclude that it contributed at most 10% of the quiescent flux in the energy range 0.5-10 keV. EXO 1745-248 is only the second neutron-star transient whose quiescent spectrum is dominated by the hard component (SAX J1808.4-3658 is the other one). We discuss possible explanations for this unusual behavior of EXO 1745-248, its relationship to other quiescent neutron-star systems, and the impact of our results on understanding quiescent X-ray binaries. We also discuss the implications of our results on the way the low-luminosity X-ray sources in globular clusters are classified.

astro-ph↗

arXiv2003

Chandra Observations of the Faintest Low-Mass X-ray Binaries

There exists a group of persistently faint galactic X-ray sources that, based on their location in the galaxy, high L_x/L_opt, association with X-ray bursts, and absence of low frequency X-ray pulsations, are thought to be low-mass X-ray binaries (LMXBs). We present results from Chandra observations for eight of these systems: 4U 1708-408, 2S 1711-339, KS 1739-304, SLX 1735-269, GRS 1736-297, SLX 1746-331, 1E 1746.7-3224, and 4U 1812-12. Locations for all sources, excluding GRS 1736-297, SLX 1746-331, and KS 1739-304 (which were not detected) were improved to 0.6" error circles (90% confidence). Our observations support earlier findings of transient behavior of GRS 1736-297, KS 1739-304, SLX 1746-331, and 2S 1711-339 (which we detect in one of two observations). Energy spectra for 4U 1708-408, 2S 1711-339, SLX 1735-269, 1E 1746.7-3224, and 4U 1812-12 are hard, with power law indices typically 1.4-2.1, which are consistent with typical faint LMXB spectra.

astro-ph↗