arXiv subjects

Jacco Vink

Publications and source records attributed to Jacco Vink.

At least 91 records · Page 5Linked to original sources

arXiv2021

The Post-impact Evolution of the X-ray Emitting Gas in SNR 1987A Viewed by XMM-Newton

Since 1996 the blast wave driven by SN 1987A has been interacting with the dense circumstellar material, which provides us with a unique opportunity to study the early evolution of a newborn supernova remnant (SNR). Based on the XMM-Newton RGS and EPIC-pn X-ray observations from 2007 to 2019, we investigated the post-impact evolution of the X-ray emitting gas in SNR 1987A. The hot plasma is represented by two non-equilibrium ionization components with temperature of $\sim0.6$ keV and $\sim2.5$ keV. The low-temperature plasma has a density $\sim2400$ cm$^{-3}$, which is likely dominated by the lower density gas inside the equatorial ring (ER). The high-temperature plasma with a density $\sim550$ cm$^{-3}$ could be dominated by the H II region and the high-latitude material beyond the ring. In the last few years, the emission measure of the low-temperature plasma has been decreasing, indicating that the blast wave has left the main ER. But the blast wave is still propagating into the high-latitude gas, resulting in the steadily increase of the high-temperature emission measure. In the meantime, the average abundances of N, O, Ne, and Mg are found to be declining, which may reflect the different chemical compositions between two plasma components. We also detected the Fe K lines in most of the observations, showing increasing flux and centroid energy. We interpret the Fe K lines as from a third hot component, which may come from the reflected shock-heated gas or originate from Fe-rich ejecta clumps, shocked by the reverse shock.

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arXiv2021

The radial supernova remnant distribution in the Galaxy

Supernovae are the dominant source of chemical enrichment of galaxies, and they are an important source of energy to heat the interstellar medium and accelerate cosmic rays. Our knowledge of supernovae in the Milky Way is based mostly on the study of Galactic supernova remnants (SNRs), providing an (incomplete) record to supernova activity over the last ~100,000 yr. Here we report on an investigation of the spatial distribution of Galactic SNRs. Given the limited number of SNRs it is common to assume a functional form for the Galactocentric distribution of SNRs. However, several functional forms have been used in the past, without much justification for the radial distribution. For example, one often used functional form implies that no supernova activity is present in the Galactic Centre region. However, the presence of a magnetar and a SNR near the Galactic Centre suggest that a spatial distribution with zero SNRs at the Galactic Centre is not realistic. In light of these concerns we reevaluate the Galactic SNR distribution. We provide a brief outline of the main detection biases in finding SNRs and we investigate whether or not the use of the most common functional form is justified and how it compares to other models for the SNR distribution. We do this by analysing the longitudinal distribution of SNRs. We find that a simple exponential distribution is the most consistent and simplest model for describing the radial SNR distribution in the Galaxy and draw comparisons with the massive star formation and metallicity distributions.

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arXiv2020

Chemical abundances in Sgr A East: evidence for a Type Iax supernova remnant

Recent observations have shown a remarkable diversity of observational behaviors and explosion mechanisms in thermonuclear supernovae (SNe). An emerging class of peculiar thermonuclear SNe, called Type Iax, show photometric and spectroscopic behaviors distinct from normal Type Ia. Their origin remains highly controversial, but pure turbulent deflagration of white dwarfs (WDs) has been regarded as the leading formation theory. The large population of Type Iax indicates the existence of unidentified Galactic Type Iax supernova remnants (SNRs). We report evidence that SNR Sgr A East in the Galactic center resulted from a pure turbulent deflagration of a Chandrasekhar-mass carbon-oxygen WD, an explosion mechanism used for Type Iax SNe. Our X-ray spectroscopic study of Sgr A East using 3 Ms of Chandra data shows a low ratio of intermediate-mass elements to Fe and large Mn/Fe and Ni/Fe ratios. This abundance pattern does not accord with the core-collapse or normal Type Ia models. Sgr A East is thus the first Galactic SNR for which a likely Type Iax origin has been proposed and the nearest target for studying this peculiar class. We compared Sgr A East with the Fe-rich SNRs 3C 397 and W49B, which also have high Mn and Cr abundances and were claimed to result from deflagration-to-detonation explosions of Chandrasekhar-mass WDs (although with disputes). Our study shows that they have distinct abundance patterns. The X-ray spectroscopic studies of thermonuclear SNRs provide observational evidence for the theories that there are diverse explosion channels and various metal outputs for Chandrasekhar-mass WDs.

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arXiv2020

Revisiting the distance, environment and supernova properties of SNR G57.2+0.8 that hosts SGR 1935+2154

We have performed a multi-wavelength study of supernova remnant (SNR) G57.2+0.8 and its environment. The SNR hosts the magnetar SGR 1935+2154, which emitted an extremely bright ms-duration radio burst on 2020 Apr 28 (The Chime/Frb Collaboration et al. 2020; Bochenek et al. 2020). We used the 12CO and 13CO J=1-0 data from the Milky Way Image Scroll Painting (MWISP) CO line survey to search for molecular gas associated with G57.2+0.8, in order to constrain the physical parameters (e.g., the distance) of the SNR and its magnetar. We report that SNR G57.2+0.8 is likely impacting the molecular clouds (MCs) at the local standard of rest (LSR) velocity V_{LSR} ~ 30 km/s and excites a weak 1720 MHz OH maser with a peak flux density of 47 mJy/beam. The chance coincidence of a random OH spot falling in the SNR is <12%, and the OH-CO correspondence chance is 7% at the maser spot. This combines to give < 1% false probability of the OH maser, suggesting a real maser detection. The LSR velocity of the MCs places the SNR and magnetar at a kinematic distance of d=6.6 +/- 0.7 kpc. The nondetection of thermal X-ray emission from the SNR and the relatively dense environment suggests G57.2+0.8 be an evolved SNR with an age $t>1.6 \times 10^4$ (d/6.6 kpc) yr. The explosion energy of G57.2+0.8 is lower than $2 \times 10^{51}(n_0/10 cm^{-3})^{1.16} (d/~6.6 kpc)^{3.16}$ erg, which is not very energetic even assuming a high ambient density $n_0$ = 10 cm$^{-3}$. This reinforces the opinion that magnetars do not necessarily result from very energetic supernova explosions.

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arXiv2020

Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum

Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD cameras, which creates a degeneracy between the best-fit values of abundances and emission measure. The combined contribution of shocked ambient medium and ejecta to the X-ray emission complicates the determination of the ejecta mass and chemical composition, leading to big uncertainties in mass estimates and it can introduce a bias in the comparison between the observed ejecta composition and the yields predicted by explosive nucleosynthesis. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature which may allow us to discriminate between metal-rich and pure-metal plasmas in X-ray spectra of SNRs. We studied the behavior of the most common X-ray emission processes of an optically thin plasma in the high-abundance regime. We investigated spectral features of bremsstrahlung, radiative recombination continua (RRC) and line emission, by exploring a wide range of chemical abundances, temperatures and ionization parameters. We synthesized X-ray spectra from a 3D hydrodynamic (HD) simulation of Cas A, by using the response matrix from the Chandra/ACIS-S CCD detector and that of the XRISM/Resolve X-ray calorimeter. We found that a bright RRC shows up when the plasma is made of pure-metal ejecta, and a high spectral resolution is needed to identify this ejecta signature. We verified the applicability of our novel diagnostic tool and we propose a promising target for the future detection of such spectral feature: the southeastern Fe-rich clump of Cas A. While there is no way to unambiguously reveal pure-metal ejecta emission with CCD detectors, X-ray calorimeters will be able to pinpoint the presence of pure-metal RRC and to recover correctly absolute mass and the chemical composition of the ejecta.

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arXiv2019

Low-frequency radio absorption in Tycho's supernova remnant

Tycho's SNR is the remnant of the type Ia supernova explosion SN1572. In this work we present new low-frequency radio observations with the LOFAR Low-Band and High-Band Antennae, centred at 58 MHz and 143 MHz, and with an angular resolution of 41'' and 6'' respectively. We compare these maps to VLA maps at 327 MHz and 1420 MHz, and detect the effect of low-frequency absorption in some regions of the remnant due to the presence of free electrons along the line-of-sight. We investigate two origins for the low-frequency free-free absorption that we observe: external absorption from foreground, and internal absorption from Tycho's unshocked ejecta. The external absorption could be due to an ionised thin, diffuse cavity surrounding the SNR (although this cavity would need to be very thin to comply with the neutral fraction required to explain the remnant's optical lines), or it could be due to an over-ionised molecular shell in the vicinity of the remnant. We note that possible ionising sources are the X-ray emission from Tycho, its cosmic rays, or radiation from Tycho's progenitor. For the internal absorption, we are limited by our understanding of the spectral behaviour of the region at unabsorbed radio frequencies. However, the observations are suggestive of free-free absorption from unshocked ejecta inside Tycho's reverse shock.

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arXiv2019

ESA Voyage 2050 white paper: A Polarized View of the Hot and Violent Universe

Since the birth of X-ray Astronomy, spectacular advances have been seen in the imaging, spectroscopic and timing studies of the hot and violent X-ray Universe, and further leaps forward are expected in the future. On the other hand, polarimetry is very much lagging behind: after the measurements of the Crab Nebula and Scorpius X-1, obtained by OSO-8 in the 70s, no more observations have been performed in the classical X-ray band, even if some interesting results have been obtained in hard X-rays and in soft gamma-rays. The NASA/ASI mission IXPE, scheduled for the launch in 2021, is going to provide for the first time imaging X-ray polarimetry in the 2-8 keV band thanks to its photoelectric polarimeter, coupled with ~25'' angular resolution X-ray mirrors. Its orders of magnitude improvement in sensitivity with respect to the OSO-8 Bragg polarimeter implies scientifically meaningful polarimetric measurements for at least the brightest specimens of most classes of X-ray sources. In 2027, the Chinese-led mission eXTP should also be launched. In addition to timing and spectroscopic instruments, eXTP will have on board photoelectric polarimeters very similar to those of IXPE, but with a total effective area 2-3 times larger. Building on IXPE results, eXTP will increase the number of sources for which significant polarimetric measurements could be obtained. However, further progresses, such as exploring a broader energy range, considering a larger effective area, improving the angular resolution, and performing wide-field polarization measurements, are needed to reach a mature phase for X-ray polarimetry. In the first part of this White Paper we will discuss a few scientific cases in which a next generation X-ray Polarimetry mission can provide significant advances. In the second part, a possible concept for a medium-class Next Generation X-ray Polarimetry (NGXP) mission will be sketched.

astro-ph.IM↗

arXiv2019

Spatially resolved X-ray study of supernova remnants that host magnetars: Implication of their fossil field origin

Magnetars are regarded as the most magnetized neutron stars in the Universe. Aiming to unveil what kinds of stars and supernovae can create magnetars, we have performed a state-of-the-art spatially resolved spectroscopic X-ray study of the supernova remnants (SNRs) Kes 73, RCW 103, and N49, which host magnetars 1E 1841-045, 1E 161348-5055, and SGR 0526-66, respectively. The three SNRs are O- and Ne-enhanced and are evolving in the interstellar medium with densities of >1--2 cm$^{-3}$. The metal composition and dense environment indicate that the progenitor stars are not very massive. The progenitor masses of the three magnetars are constrained to be < 20 Msun (11--15 Msun for Kes 73, < 13 Msun for RCW 103, and ~13 --17 Msun for N49). Our study suggests that magnetars are not necessarily made from very massive stars, but originate from stars that span a large mass range. The explosion energies of the three SNRs range from $10^{50}$ erg to ~2$\times 10^{51}$ erg, further refuting that the SNRs are energized by rapidly rotating (millisecond) pulsars. We report that RCW 103 is produced by a weak supernova explosion with significant fallback, as such an explosion explains the low explosion energy (~$10^{50}$ erg), small observed metal masses ($M_{\rm O}\sim 4\times 10^{-2}$ Msun and $M_{\rm Ne}\sim 6\times 10^{-3}$ Msun), and sub-solar abundances of heavier elements such as Si and S. Our study supports the fossil field origin as an important channel to produce magnetars, given the normal mass range ($M_{\rm ZAMS} < 20$ Msun) of the progenitor stars, the low-to-normal explosion energy of the SNRs, and the fact that the fraction of SNRs hosting magnetars is consistent with the magnetic OB stars with high fields.

astro-ph.HE↗

arXiv2019

The X-ray Polarization Probe mission concept

The X-ray Polarization Probe (XPP) is a second generation X-ray polarimeter following up on the Imaging X-ray Polarimetry Explorer (IXPE). The XPP will offer true broadband polarimetery over the wide 0.2-60 keV bandpass in addition to imaging polarimetry from 2-8 keV. The extended energy bandpass and improvements in sensitivity will enable the simultaneous measurement of the polarization of several emission components. These measurements will give qualitatively new information about how compact objects work, and will probe fundamental physics, i.e. strong-field quantum electrodynamics and strong gravity.

astro-ph.IM↗

arXiv2019

The environment of supernova remnant VRO 42.05.01 as probed with IRAM 30m molecular line observations

The environment of supernova remnants (SNRs) is a key factor in their evolution, particularly at later stages of their existence. It is often assumed that mixed-morphology (MM) SNRs evolve in very dense environments, and that their centre-filled X-ray morphology is due to interactions between the SNRs and their surroundings. We aim to determine whether MMSNR VRO 42.05.01 is embedded in, and interacting with, a dense molecular environment. We used the IRAM telescope in Pico Veleta, Spain, to search for interaction between the SNR and neighbouring molecular clouds. We observed a region of $26'\times14'$ towards the west of VRO 42.05.01 and a region of $8'\times4'$ towards the north of the remnant in the $^{12}$CO $J=1-0$, $^{13}$CO $J=1-0$, and $^{12}$CO $J=2-1$ transitions with the EMIR receiver. We made maps of the properties of the observed molecular clouds (peak temperatures, central velocities, velocity dispersions), column density along the line of sight, and ratio of the $^{12}$CO $J=2-1$ to $^{12}$CO $J=1-0$ transitions. We analyse archival optical, infrared, and radio spectroscopic data for other hints on the nature of the medium. We do not find conclusive physical proof that the SNR is interacting with the few, clumpy molecular clouds that surround it in the region of our observations, although there is some suggestion of such interaction (in a region outside our map) from infrared emission. There is a velocity gradient in one of the molecular clouds that is consistent with a stellar wind blown by a $12-14$ $M_{\odot}$ progenitor star. We reassess the literature distance to VRO 42.05.01, and propose that it has a local standard of rest velocity of $-6$ km s$^{-1}$, and that it is located $1.0\pm0.4$ kpc away (the earlier distance value was $4.5\pm1.5$ kpc). We find that a dust sheet intersects VRO 42.05.01 and is possibly related to its double shell-shaped morphology.

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arXiv2019

A study of the composite supernova remnant MSH 15-56 with Suzaku

The Galactic supernova remnant (SNR) MSH 15-56 is a member of the class of composite SNRs that consists of the remnant shell and a displaced pulsar wind nebula (PWN). The earlier X-ray observations reported the comet-like morphology of the PWN and the ejecta distribution of the SNR. In this work, we present a study of MSH 15-56 using archival Suzaku data. We investigate the nature of the emission and spectral parameters of the remnant. The X-ray spectra are well fitted with a combination of a thermal and non-thermal model with temperature ~0.6 keV and photon index ~2.0. The slightly enhanced abundances of Ne, Mg, S and enhanced abundance of Si confirm the presence of ejected material.

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arXiv2019

Astro2020 Science White Paper: Future X-ray Studies of Supernova Remnants

This is a white paper submitted in response to the call from the Astro2020 Decadal Survey Committee. We outline the scientific progress that will be made in the next few decades in the study of supernova remnants in the X-ray band, using observatories like Athena, Lynx, and AXIS.

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arXiv2019

Supernova Remnants in High Definition

Supernova remnants (SNRs) offer the means to study SN explosions, dynamics, and shocks at sub-parsec scales. X-ray observations probe the hot metals synthesized in the explosion and the TeV electrons accelerated by the shocks, and thus they are key to test recent, high-fidelity three-dimensional SN simulations. In this white paper, we discuss the major advances possible with X-ray spectro-imaging at arcsecond scales, with a few eV spectral resolution and a large effective area. These capabilities would revolutionize SN science, offering a three-dimensional view of metals synthesized in explosions and enabling population studies of SNRs in Local Group galaxies. Moreover, this future X-ray mission could detect faint, narrow synchrotron filaments and shock precursors that will constrain the diffusive shock acceleration process.

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arXiv2019

Evidence for recent GeV brightening of the SN 1987A region

We report on a recent (2016-2018) enhancement of the GeV emission from the SN 1987A region as observed with Fermi/LAT. The observed signal is characterised by a power-law spectrum with a slope of 2.1 +/- 0.2 and is detected only at energies >1 GeV. The Fermi/LAT data constrain the position of the signal to within 0.15 degree around SN 1987A. Although a recent increase in the gamma-ray emission from SN 1987A seems to be a natural explanation for the detected emission, given the youth of the source and its rapid evolution, the Fermi/LAT location also overlaps with several other potential gamma-ray sources: 30 Dor C, Honeycomb nebula, RX J0536.9-6913, and a hypothetical, previously unknown transient source. We argue that multiwavelength observations of the region performed during the next few years can clarify the nature of the signal and encourage such observations. We also present upper limits on the time-averaged flux of SN 1987A based on 10 years of Fermi/LAT exposure, which can be used to better constrain the particle acceleration models of this source.

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arXiv2018

Magnetic field estimates from the X-ray synchrotron emitting rims of the 30 Dor C superbubble and the implications for the nature of 30 Dor C's TeV emission

The 30 Dor C superbubble is unique for its synchrotron X-ray shell, as well as being the first superbubble to be detected in TeV $γ$-rays, though the dominant TeV emission mechanism, i.e., leptonic or hadronic, is still unclear. We aim to use new Chandra observations of 30 Dor C to resolve the synchrotron shell in unprecedented detail and to estimate the magnetic ($B$) field in the postshock region, a key discriminator between TeV $γ$-ray emission mechanisms. We extracted radial profiles in the 1.5-8 keV range from various sectors around the synchrotron shell and fitted these with a projected and point spread function convolved postshock volumetric emissivity model to determine the filament widths. We then calculated the postshock magnetic field strength from these widths. We found that most of the sectors were well fitted with our postshock model and the determined $B$-field values were low, all with best fits $\lesssim 20~μ$G. Upper limits on the confidence intervals of three sectors reached $\gtrsim 30~μ$G though these were poorly constrained. The generally low $B$-field values suggests a leptonic-dominated origin for the TeV $γ$-rays. Our postshock model did not provide adequate fits to two sectors. We found that one sector simply did not provide a clean enough radial profile, while the other could be fitted with a modified model where the projected profile falls off abruptly below $\sim0.8$ times the shell radius, yielding a postshock $B$-field of 4.8 (3.7-11.8) $μ$G which is again consistent with the leptonic TeV $γ$-ray mechanism. Alternatively, the observed profiles in these sectors could result from enhancements around a shock-cloud interaction as suggested in previous works. The average $B$-field determined around the X-ray synchrotron shell of 30 Dor C suggests the leptonic scenario as the dominant emission mechanism for the TeV $γ$-rays.

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arXiv2018

Molecular gas toward supernova remnant Cassiopeia A

We mapped 12CO J=1-0, 12CO J=2-1, 13CO J=1-0, and 13CO J=2-1 lines toward supernova remnant (SNR) Cassiopeia A with the IRAM 30m telescope. The molecular clouds (MCs) along the line of sight of Cas A do not show optically thin, shock-broadened 12CO lines ($ΔV \le 7$ km s$^{-1}$ toward Cas A), or high-temperature features from shock heating ($T_k \le 22$ K toward Cas A). Therefore, we suggest that there is no physical evidence to support that the SNR is impacting the molecular gas. All the detected MCs are likely in front of Cas A, as implied by the HCO+ absorption line detected in the same velocity ranges. These MCs contribute H$_2$ column densities of $5\times 10^{21}$ cm$^{-2}$, $5\times 10^{21}$ cm$^{-2}$, and $2\times 10^{21}$ cm$^{-2}$ in the west, south, and center of the SNR, respectively. The 20 K warm gas at $V_{LSR}\sim -47$ km s$^{-1}$ is distributed along a large-scale molecular ridge in the south of Cas A. Part of the gas is projected onto Cas A, providing a foreground H$_2$ mass of $\sim 200 (d/3 kpc)^2$ Msun, consistent with the mass of cold dust (15--20 K; 2--4 Msun) found in front of the SNR. We suggest that the 20 K warm gas is heated by background cosmic rays with an ionization rate of $ζ({\rm H_2})\sim 2\times 10^{-16}$ s$^{-1}$. The cosmic rays or X-ray emission from Cas A are excluded as the heating sources of the clouds.

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arXiv2018

G7.7-3.7: a young supernova remnant probably associated with the guest star in 386 CE (SN 386)

Although the Galactic supernova rate is about 2 per century, only few supernova remnants are associated with historical records. There are a few ancient Chinese records of "guest stars" that are probably sightings of supernovae for which the associated supernova remnant is not established. Here we present an X-ray study of the supernova remnant G7.7-3.7, as observed by XMM-Newton, and discuss its probable association with the guest star of 386 CE. This guest star occurred in the ancient Chinese asterism Nan-Dou, which is part of Sagittarius. The X-ray morphology of G7.7-3.7 shows an arc-like feature in the SNR south, which is characterized by an under-ionized plasma with sub-solar abundances, a temperature of 0.4--0.8 keV, and a density of $\sim 0.5(d/4 kpc)^{-0.5}$ cm$^{-3}$. A small shock age of $1.2\pm 0.6 (d/4 kpc)^{0.5}$ kyr is inferred from the low ionization timescale of $2.4^{+1.1}_{-1.3}\times 10^{10}$ cm$^{-3}$ s of the X-ray arc. The low foreground absorption ($N_H=3.5\pm0.5\times 10^{21}$ cm$^{-2}$) of G7.7-3.7 made the supernova explosion visible to the naked eyes on the Earth. The position of G7.7-3.7 is consistent with the event of 386 CE, and the X-ray properties suggest that also its age is consistent. Interestingly, the association between G7.7-3.7 and guest star 386 would suggest the supernova to be a low-luminosity supernova, in order to explain the not very long visibility (2--4 months) of the guest star.

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arXiv2018

Spatially resolved broad-band synchrotron emission from the non-thermal limbs of SN1006

We present ~400ks NuSTAR observations of the northeast (NE) and southwest (SW) non-thermal limbs of the Galactic SNR SN1006. We discovered three sources with X-ray emission detected at >50keV. Two of them are identified as background AGN. We extract the NuSTAR spectra from a few regions along the non-thermal limbs and jointly analyze them with the XMM-Newton spectra and the radio data. The broad-band radio/X-ray spectra can be well described with a synchrotron emission model from a single population of CR electrons with a power law energy distribution and an exponential cutoff. The power law index of the electron particle distribution function (PDF) is ~1.88-1.95 for both the NE and SW limbs, and we do not find significant evidence for a variation of this index at different energy (curvature). There are significant spatial variations of the synchrotron emission parameters. The highest energy electrons are accelerated in regions with the lowest expansion velocity, which is opposite to what has been found in the Tycho's SNR. In addition to a gradual steepening of synchrotron emission from the center of the non-thermal limbs to larger azimuthal angles, we also find that both the emission spectrum and the PDF are significantly flatter in three regions in the SW limb where the shock encounters higher density ambient medium. The NE limb also shows significantly higher cutoff energy in the PDF than the SW limb. By comparing with the roughly symmetric TeV emission and largely asymmetric GeV emission from the two non-thermal limbs, we conclude that the asymmetry in the ambient medium and magnetic fields may have largely modified the acceleration and emission of CR leptons.

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