arXiv subjects

Jacco Vink

Publications and source records attributed to Jacco Vink.

At least 145 records · Page 8Linked to original sources

arXiv2009

Suzaku Observation of the RCW86 Northeastern Shell

This paper reports the Suzaku results on the northeast shell of RCW 86. With the spatial and spectral analysis, we separated the X-rays into three distinct components; low (kT_e~0.3keV) and high (kT_e~1.8keV) temperature plasmas and a non-thermal component, and discovered their spatial distributions are different from each other. The low temperature plasma is dominated at the east rim, whereas the non-thermal emission is the brightest at the northeast rim which is spatially connected from the east rim. The high temperature plasma, found to contain the ~6.42keV line (K alpha of low-ionized iron), is enhanced at the inward region with respect to the east rim and has no spatial correlation with the non-thermal X-ray (the northeast). The Fe-Kalpha line, therefore, is not related to the non-thermal emission but originates from Fe-rich ejecta heated to the high temperatures by the reverse shock. Since the metal abundances of the low temperature plasma are sub-solar, the most possible origin of this component is interstellar medium heated by a blast wave. The non-thermal X-ray, which has a power-law index of ~2.8, is likely to be synchrotron emission. A possible scenario to explain these morphologies and spectra is: A fast moving blast wave in a thin cavity of OB association collided with a dense interstellar medium or cloud at the east region very recently. As the result, the reverse shock in this interior decelerated, and arrived at the Fe-rich region of the ejecta and heated it. In the northeast rim, on the other hand, the blast wave is still moving fast, and accelerated high energy electrons to emit synchrotron X-rays.

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arXiv2008

Multiwavelength Signatures of Cosmic Ray Acceleration by Young Supernova Remnants

An overview is given of multiwavelength observations of young supernova remnants, with a focus on the observational signatures of efficient cosmic ray acceleration. Some of the effects that may be attributed to efficient cosmic ray acceleration are the radial magnetic fields in young supernova remnants, magnetic field amplification as determined with X-ray imaging spectroscopy, evidence for large post-shock compression factors, and low plasma temperatures, as measured with high resolution optical/UV/X-ray spectroscopy. Special emphasis is given to spectroscopy of post-shock plasma's, which offers an opportunity to directly measure the post-shock temperature. In the presence of efficient cosmic ray acceleration the post-shock temperatures are expected to be lower than according to standard equations for a strong shock. For a number of supernova remnants this seems indeed to be the case.

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arXiv2008

Non-thermal bremsstrahlung from supernova remnants and the effect of Coulomb losses

I investigate the shape of the electron cosmic ray spectrum in the range up to ~1000 keV, assuming that the acceleration process at the shock results in a power law in momentum, and that downstream of the shock the spectrum is affected by Coulomb interactions with background electrons only. In the non-relativistic regime one can analytically determine the energy of an electron starting with a certain energy, and use this result to produce an electron cosmic ray spectrum, modified by Coulomb losses. An analytic expression for the electron spectrum is obtained that depends on the parameter n_e t, which can be estimated from a similar parameter used to characterize the line spectra of supernova remnants. For the brightest supernova remnants n_e t > 1e11 cm^-3 s,and most of the electrons accelerated to < 100 keV have lost their energy. Because of its high radio flux, Cas A is the most likely candidate for non-thermal bremsstrahlung. Although it has n_e t ~ 2e11 cm^-3 s, one may expect to pick up non-thermal bremsstrahlung above 100 keV with current hard X-ray detectors.

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arXiv2007

Supernova remnants with magnetars: clues to magnetar formation

I discuss the lack of observational evidence that magnetars are formed as rapidly rotating neutron stars. Supernova remnants containing magnetars do not show the excess of kinetic energy expected for such a formation scenario, nor is there any evidence for a relic pulsar wind nebula. However, it could be that magnetars are formed with somewhat slower rotation periods, or that not all excess rotational energy was used to boost the explosion energy, for example as a result of gravitational radiation. Another observational tests for the rapid initial period hypothesis is to look for statistical evidence that about 1% of the observed supernovae have an additional 1E40-1E44 erg/s excess energy during the first year, caused by the spin down luminosity of a magnetar. An alternative scenario for the high magnetic fields of magnetars is the fossil field hypothesis, in which the magnetic field is inherited from the progenitor star. Direct observational tests for this hypothesis are harder to formulate, unless the neutron star formed in the SN1987A explosion emerges as a slowly rotating magnetar. Finally, I point out the possible connection between the jets in Cas A and its X-ray point source: the jets in Cas A may indicate that the explosion was accompanied by an X-ray flash, probably powered by a rapidly rotating compact object. However, the point source in Cas A does not seem to be a rapidly rotating neutron star, suggesting that the neutron star has slowed down considerably in 330 yr, requiring a magnetar-like field.

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arXiv2007

Constraining supernova models using the hot gas in clusters of galaxies

The hot Intra-Cluster Medium (ICM) in clusters of galaxies is a very large repository of metals produced by supernovae. We aim to accurately measure the abundances in the ICM of many clusters and compare these data with metal yields produced by supernovae. Using the data archive of the XMM-Newton X-ray observatory, we compile a sample of 22 clusters. We fit spectra extracted from the core regions and determine the abundances of silicon, sulfur, argon, alcium, iron, and nickel. The abundances from the spectral fits are subsequently fitted to supernova yields determined from several supernova type Ia and core-collapse supernova models. We find that the argon and calcium abundances cannot be fitted with currently favoured supernova type Ia models. We obtain a major improvement of the fit, when we use an empirically modified delayed-detonation model that is calibrated on the Tycho supernova remnant. The two modified parameters are the density where the sound wave in the supernova turns into a shock and the ratio of the specific internal energies of ions and electrons at the shock. Our fits also suggest that the core-collapse supernovae that contributed to the enrichment of the ICM had progenitors which were already enriched. The Ar/Ca ratio in clusters is a good touchstone for determining the quality of type Ia models. The core-collapse contribution, which is about 50% and not strongly dependent on the IMF or progenitor metallicity, does not have a significant impact on the Ar/Ca ratio. The number ratio between supernova type Ia and core-collapse supernovae suggests that binary systems in the appropriate mass range are very efficient (~ 5-16%) in eventually forming supernova type Ia explosions.

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arXiv2006

XMM-Newton high-resolution spectroscopy reveals the chemical evolution of M 87

We present here a study of chemical abundances in the giant elliptical galaxy M 87 using high-resolution spectra obtained with the Reflection Grating Spectrometers during two deep XMM-Newton observations. While we confirm the two-temperature structure of the inter-stellar medium (ISM) in M 87, we also show that a continuous temperature distribution describes the data equally well. The high statistics allows us, for the first time, to determine relatively accurate abundance values also for carbon and nitrogen. The comparison of the abundance ratios of C, N, O and Fe in the ISM of M 87 with those in the stellar population of our Galaxy shows that the relative contribution of core-collapse supernovae to the enrichment of the ISM in M 87 is significantly less than in the Milky Way and indicates that the enrichment of the ISM by iron through Type Ia supernovae and by carbon and nitrogen is occurring in parallel. This suggests that the main source of carbon and nitrogen in M 87 are the low- and intermediate-mass asymptotic giant branch stars. From the oxygen to iron abundance ratio in the hot gas we estimate that the relative number of core collapse and type Ia supernovae contributing to the enrichment of the ISM in the core of M 87 is ~60% and ~40% respectively. The spatial distributions of iron and oxygen are different. While the oxygen abundance distribution is flat the iron abundance peaks in the core and has a gradient throughout the ~4' wide field of view of the instrument, suggesting an early enrichment by core-collapse supernovae and a continuous contribution of type Ia supernovae.

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arXiv2006

The X-ray synchrotron emission of RCW 86 and the implications for its age

We report here X-ray imaging spectroscopy observations of the northeastern shell of the supernova remnant RCW 86 with Chandra and XMM-Newton. Along this part of the shell the dominant X-ray radiation mechanism changes from thermal to synchrotron emission. We argue that both the presence of X-ray synchrotron radiation and the width of the synchrotron emitting region suggest a locally higher shock velocity of V_s = 2700 km/s and a magnetic field of B = 24+/-5 microGauss. Moreover, we also show that a simple power law cosmic ray electron spectrum with an exponential cut-off cannot explain the broad band synchrotron emission. Instead a concave electron spectrum is needed, as predicted by non-linear shock acceleration models. Finally, we show that the derived shock velocity strengthens the case that RCW 86 is the remnant of SN 185.

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arXiv2006

Supernova remnant energetics and magnetars: no evidence in favour of millisecond proto-neutron stars

It is generally accepted that Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are magnetars, i.e. neutron stars with extremely high surface magnetic fields ($B > 10^{14}$ G). The origin of these high magnetic fields is uncertain, but a popular hypothesis is that magnetars are born with an initial spin period not much exceeding the convective overturn time (~3ms), which results in a powerful dynamo action, amplifying the seed magnetic field to $> ~10^{15}$ G. Part of this rotation energy is then expected to power the supernova through rapid magnetic braking. It is therefore possible that magnetars creation is accompanied by supernovae that are an order of magnitude more energetic than normal supernovae, provided their initial spin period is ~1 ms. However, we list here evidence that the explosion energies of these supernova remnants associated with AXPs and SGRs -- Kes 73 (AXP 1E 1841-045), CTB 109 (AXP 1E2259+586) and N49 (SGR 0526-66) -- are close to the canonical supernova explosion energy of $10^{51}$~erg, suggesting an initial spin period of > ~5ms. We therefore do not find evidence that magnetars are formed from rapidly rotating proto-neutron stars, allowing for the possibility that they descend from stellar progenitor with high magnetic field cores, and we discuss the merits of both formation scenarios. In an appendix we describe the analysis of XMM-Newton observations of Kes 73 and N49 used to derive the explosion energies for these remnants.

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arXiv2006

X-ray High Resolution and Imaging Spectroscopy of Supernova Remnants

The launch of Chandra and XMM-Newton has led to important new findings concerning the X-ray emission from supernova remnants. These findings are a result of the high spatial resolution with which imaging spectroscopy is now possible, but also some useful results have come out of the grating spectrometers of both X-ray observatories, despite the extended nature of supernova remnants. The findings discussed here are the evidence for slow equilibration of electron and ion temperatures near fast supernova remnant shocks, the magnetic field amplification near remnant shocks due to cosmic ray acceleration, a result that has come out of studying narrow filaments of X-ray synchrotron emission, and finally the recent findings concerning Fe-rich ejecta in Type Ia remnants and the presence of a jet/counter jet system in the Type Ib supernova remnant Cas A.

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arXiv2006

The X-ray properties of young radio-loud AGN

We present XMM-Newton observations of a complete sample of five archetypal young radio-loud AGN, also known Gigahertz Peaked Spectrum (GPS) sources. They are among the brightest and best studied GPS/CSO sources in the sky, with radio powers in the range L_{5GHz}=10^{43-44} erg/s and with 4 sources having measured kinematic ages of 570 to 3000 yrs. All sources are detected, and have 2-10 keV luminosities from 0.5 to 4.8x10^{44} erg/s. In comparison with the general population of radio galaxies, we find that: 1) GPS galaxies show a a range in absorption column densities similar to other radio galaxies. We therefore find no evidence that GPS galaxies reside in significantly more dense circumnuclear environment, such that they could be hampered in their expansion. 2) The ratio of radio to X-ray luminosity is significantly higher than for classical radio sources. This is consistent with an evolution scenario in which young radio sources are more efficient radio emitters than large extended objects at a constant accretion power. 3) Taking the X-ray luminosity of radio sources as a measure of ionisation power, we find that GPS galaxies are significantly underluminous in their [OIII]_{5007 Angstrom}, including a weak trend with age. This is consistent with the fact that the Stroemgren sphere should still be expanding in these young objects. This would mean that here we are witnessing the birth of the narrow line region of radio-loud AGN.

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arXiv2006

High Energy Emission from Supernova Remnants

This paper discusses several aspects of current research on high energy emission from supernova remnants, covering the following main topics: 1) The recent evidence for magnetic field amplification near supernova remnant shocks, which makes that cosmic rays are more efficiently accelerated than previously thought. 2) The evidence that ions and electrons in some remnants have very different temperatures, and only equilibrate through Coulomb interactions. 3) The evidence that the explosion that created Cas A was asymmetric, and seems to have involved a jet/counter jet structure. And finally, 4), I will argue that the unremarkable properties of supernova remnants associated with magnetars candidates, suggest that magnetars are not formed from rapidly (P ~ 1 ms) rotating proto-neutron stars, but that it is more likely that they are formed from massive progenitors stars with high magnetic fields.

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arXiv2005

XMM-Newton Spectroscopy of the Cluster of Galaxies 2A 0335+096

We present here the results of a deep (130 ks) XMM-Newton observation of the cluster of galaxies 2A 0335+096. The deep exposure allows us to study in detail its temperature structure and its elemental abundances. We fit three different thermal models and find that the multi-temperature wdem model fits our data best. We find that the abundance structure of the cluster is consistent with a scenario where the relative number of Type Ia supernovae contributing to the enrichment of the intra-cluster medium is ~25%, while the relative number of core collapse supernovae is ~75%. Comparison of the observed abundances to the supernova yields does not allow us to put any constrains on the contribution of Pop III stars to the enrichment of the ICM. Radial abundance profiles show a strong central peak of both Type Ia and core collapse supernova products. Both the temperature and iron abundance maps show an asymmetry in the direction of the elongated morphology of the surface brightness. In particular the temperature map shows a sharp change over a brightness edge on the southern side of the core, which was identified as a cold front in the Chandra data. This suggests that the cluster is in the process of a merger with a subcluster. Moreover, we find that the blobs or filaments discovered in the core of the cluster by Chandra are, contrary to the previous results, colder than the ambient gas and they appear to be in pressure equilibrium with their environment.

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arXiv2005

Gamma-ray Observations of Explosive Nucleosynthesis Products

In this review I discuss the various gamma-ray emission lines that are expected and have been observed from radioactive explosive nucleosynthesis products. The most important gamma-ray lines result from the decay chains of Ni-56, Ni-57, and Ti-44. Ni-56 is the prime explosive nucleosynthesis product of Type Ia supernovae, but Ni-56 is also a product of core-collapse supernovae. Gamma-ray line emission from its daughter product, Co-56, has been detected from SN1987A. The early occurrence of this emission indicates that some fraction of Ni-56, which is synthesized in the innermost supernova layers, must have mixed with the outermost ejecta. Special attention is given to the gamma-ray line emission of the decay chain of Ti-44, giving line emission at 68 keV, 78 keV, and 1157keV. Given its decay time of 86 yr, one expects this line emission from young supernova remnants. The Ti-44 production is very sensitive to the explosion properties This makes Ti-44 an ideal tool to study the inner layers of the supernova explosion. The gamma-ray line emission from Ti-44 has so far only been detected from the supernova remnant Cas A. I discuss these detections, which were made by COMPTEL and BeppoSAX, which suggest a Ti-44 yield of (1.5+/-1.0)x10^{-4} Msun. Moreover, I present some preliminary results of Cas A observations by INTEGRAL, which has yielded a 3sigma detection of the 68 keV line with the ISGRI instrument at a level consistent with the BeppoSAX results. A preliminary analysis of the vailable INTEGRAL-SPI data indicates that narrow line emission (Delta v < 1000 km/s) can be almost excluded at the 2sigma level. (Abridged)

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arXiv2004

High Resolution X-ray Spectroscopy of SN 1006

I discuss the high resolution XMM-Newton Reflection Grating Spectrometer (RGS) spectrum of SN1006. SN1006 is one of the best examples of a supernova remnant that is far out of ionization equilibrium. Moreover, optical, UV and X-ray data indicate that it is also out of temperature equilibrium. I discuss the X-ray evidence for this. In addition I discuss the lower resolution RGS spectrum of the eastern rim of SN 1006. Despite the lower resolution, the spectrum contains significant evidence for an asymmetric expansion velocity. Two likely solutions fit the O VII triplet. One with no significant thermal broadening and a shell velocity of \~6500 km/s, and one with significant broadening and a shell velocity of ~9500 km/s. The first solution seems the most plausible, as it is consistent with radio expansion measurements, which suggest a decelerated shell.

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arXiv2004

A Million-Second Chandra View of Cassiopeia A

We introduce a million-second observation of the supernova remnant Cassiopeia A with the Chandra X-ray Observatory. The bipolar structure of the Si-rich ejecta (NE jet and SW counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

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arXiv2004

Non-thermal X-ray Emission from Supernova Remnants

Recent studies of narrow, X-ray synchrotron radiating filaments surrounding young supernova remnants indicate that magnetic fields strengths are relatively high, B ~ 0.1 mG, or even higher, and that diffusion is close to the Bohm limit. I illustrate this using Cas A as an example. Also older remnants such as RCW 86 appear to emit X-ray synchrotron radiation, but the emission is more diffuse, and not always confined to a region close to the shock front. I argue that for RCW 86 the magnetic field is likely to be low (B ~ 17 microGauss), and at the location where the shell emits X-ray synchrotron radiation the shock velocity is much higher than the average shock velocity of ~600 km/s.

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arXiv2004

The continued spectral evolution of the neutron star RX J0720.4-3125

We observed the isolated neutron star RX J720.4-3125 with Chandra's Low Energy Transmission Grating Spectrometer, following the XMM-Newton discovery of long term spectral evolution of this source. The new observation shows that the spectrum of RX J720.4-3125 has continued to change in the course of 5 months. It has remained hard, similar to the last XMM-Newton observation, but the strong depression observed with XMM-Newton at long wavelengths has disappeared. Contrary to the XMM-Newton observations, the new Chandra observation shows that the flux increase at short wavelengths and the decrease at long wavelengths do not necessarily occur simultaneously.

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arXiv2004

High Resolution X-ray Spectroscopy of G292.0+1.8/MSH 11-54

We present a preliminary analysis of XMM-Newton observations of the oxygen-rich supernova remnant G292.0+1.8 (MSH 11-54). Although the spatial extent of the remnant is 8 arcmin the bright central bar is narrow (1'-2') resulting in RGS spectra of a high spectral quality. This allows us to spectroscopically identify a cool, Te = 0.3 keV, and underionized component, resolve details of the Fe-L complex, and resolve the forbidden and resonant lines of the O VII triplet. We are also able to constrain the kinematics of the remnant using Ne IX as observed in the second order spectrum, and O VIII in the first order spectrum. We do not find evidence for O VII line shifts or Doppler broadening (sigma_v < 731 km/s), but line broadening of the Ne X Ly-alpha line seems to be present, corresponding to sigma_v ~ 1500 km/s.

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