arXiv subjects

Pierre Maggi

Publications and source records attributed to Pierre Maggi.

At least 19 recordsLinked to original sources

arXiv2026

Fast Optical Variability of the TeV Blazar PKS 1725+123 Observed by SVOM-VT and Insights from Multi-wavelength Follow-up Observations

PKS 1725+123 is a flat-spectrum radio quasar (FSRQ) with a redshift of $z=0.586$. The detection of this object in the TeV band was reported by the MAGIC telescopes and H.E.S.S. in August 2025. Subsequently, we promptly initiated Target-of-Opportunity observations using the Space-based multi-band astronomical Variable Objects Monitor (SVOM) satellite. By analyzing the observational optical data from SVOM-VT and comprehensively examining the Fermi-LAT and Swift-XRT observational data, it was found that the source is in a high-flux state across the optical, X-ray, and GeV $\gamma$-ray bands around the time of the TeV detections. Its optical flux reaches a historically unprecedented high level and shows significant variability on timescale as short as minutes. The variability is accompanied by changes in the color index, exhibiting a bluer when brighter behavior during the high-flux state. Based on the simultaneous multi-wavelength data, we construct the broadband spectral energy distribution (SED) of the source in the high-flux state. PKS 1725+123 demonstrates a remarkably high synchrotron peak frequency, which is distinctly different from that of other FSRQs. We propose a two-zone spine-sheath jet model to reproduce this SED. The optical--X-ray emission is generated by the synchrotron process of the relativistic electrons within a compact zone. The inverse Compton (IC) scattering processes of the same electron population contribute to the low-energy end of the Fermi-LAT spectrum, while the high-energy end of the Fermi-LAT spectrum is ascribed to the IC scattering of the synchrotron photons within the compact zone by the higher-energy electrons in an extended region.

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arXiv2026

Multiwavelength Analysis of the Einstein Probe X-ray Transient EP240305a

We report multiwavelength observations of EP240305a, an uncatalogued X-ray transient detected by the Einstein Probe on March 5, 2024. The source exhibits distinct characteristics across the X-ray, optical, near-infrared, and radio bands. The soft X-ray observations show two significant flares lasting ~100-250 s, accompanied by rapid flux decay in a few days, and the optical and near-infrared data reveal a faint, candidate counterpart. In contrast, the radio observations expose a long-term spectral evolution from a self-absorbed to an optically thin state within two months, implying discrete jet ejection. We compare EP240305a with known classes of X-ray transients and find that it is unlikely to be associated with long-timescale transients such as jetted tidal disruption events or X-ray binaries. Its properties also disfavor a short-timescale stellar flare origin. Although the absence of optical spectroscopy prevents a redshift determination, the source exhibits properties similar to those of gamma-ray-dark gamma-ray burst-like transients, which may be associated with relativistic jets viewed off-axis or with choked jets. The discovery of EP240305a, along with other uncataloged transients detected by the Einstein Probe, underscores the scientific potential of highly sensitive X-ray survey telescopes and rapid-response multiwavelength follow-up observations in exploring the nature of atypical astronomical transients.

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arXiv2025

GRB 240715A: Revealing Novel Intrinsic Mechanism by Different Individual Pulse

The Space-based multiband astronomical Variable Objects Monitor (SVOM), detected its first short gamma-ray burst, GRB 240715A, in-flight, which was jointly observed by Fermi. Based on observational data of SVOM/GRM and Fermi/GBM, we perform a comprehensive temporal and spectral analysis for individual pulse in the prompt emission of this burst, and novel characteristics are revealed. Firstly, opposite evolutions of spectral lag are found in the first and third pulse of this burst. Second, the large negative lag of the first pulse is an outlier in short GRB sample, especially when the pulse duration is considered. Spectral analysis shows that the negative lag of the first pulse is caused by the evolution of spectrum index, and is irrelevant to Epeak, which is inconsistent with the previous study. The intrinsic mechanism is probably attributed to electron cooling in the decaying magnetic field, which leads to the continuous hardening of the spectrum index and results in negative lag. Furthermore, spectral analysis also shows that the third pulse is more likely to be described by a quasi-thermal spectrum, indicating the existence of photospheric emission. It is difficult to explain how the synchrotron radiation appears before photospheric emission in a single GRB and some assumptions are discussed.

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arXiv2025

A New Radio Continuum Study of the Large Magellanic Cloud Supernova Remnant MC SNR J0519-6902

We present a new radio continuum study of the Large Magellanic Cloud supernova remnant (SNR) MC SNR J0519-6902. With a diameter of ~8 pc, this SNR shows a radio ring-like morphology with three bright regions toward the north, east, and south. Its linear polarisation is prominent with average values of 5 +- 1% and 6 +- 1% at 5500 and 9000 MHz, and we find a spectral index of -0.62 +- 0.02 , typical of a young SNR. The average rotation measure is estimated at -124 +- 83 rad m-2 and the magnetic field strength at ~11 muG. We also estimate an equipartition magnetic field of 72 +- 5 muG and minimum explosion energy of Emin = 2.6x1048 erg. Finally, we identified an H I cloud that may be associated with MC SNR J0519-6902, located in the southeastern part of the remnant, along with a potential wind-bubble cavity.

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arXiv2025

Evolution of the Comptonizing medium of the black-hole candidate Swift J1727.8$-$1613 along the hard to hard-intermediate state transition using NICER

We analyse the properties of the Comptonizing medium in the black-hole X-ray binary Swift J1727.8$-$1613 using the time-dependent Comptonization model vkompth, using NICER observations of type-C QPOs in the hard and hard-intermediate states. During the 2023 outburst of the source, we measure the rms and phase lags of the QPO across 45 observations as the QPO frequency, $\nu_{\rm QPO}$, evolves from $\sim 0.3$ Hz to $\sim 7$ Hz. By simultaneously fitting the time-averaged spectrum of the source and the rms and lag spectra of the QPO, we derive the evolution of the disk and corona parameters. At $\nu_{\rm QPO} = 0.34$ Hz, the QPO phase lags are hard, with 10 keV photons lagging 0.5 keV photons by $\sim 0.5$ rad. As $\nu_{\rm QPO}$ increases, the lags for the same energy bands decrease, reaching near zero at $\nu_{\rm QPO} \sim 1.2$ Hz, and then reverse to soft lags of $\sim -1.1$ rad at $\nu_{\rm QPO} \sim 7$ Hz. Initially, the inner radius of the accretion disk is truncated at $\sim 30-40 R_g$ (assuming a 10 solar-mass black hole) and, as the QPO frequency increases, the truncation radius decreases down to $\sim 10 R_g$. Initially, two coronas of sizes of $\sim 6.5 \times 10^3$ km and $\sim 2 \times 10^3$ km, extend over the disk and are illuminated by different regions of the disk. As the QPO frequency increases, both the coronas shrink to $\sim 2 \times 10^3$ km at $\nu_{\rm QPO} = 2.5$ Hz. Following a data gap, one corona expands again, peaking at a size of $\sim 2 \times 10^4$ km. We interpret the evolution of the coronal size in the context of accompanying radio observations, discussing its implications for the interplay between the corona and the jet.

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arXiv2025

Science objectives of the Einstein Probe mission

The Einstein Probe (EP) is an interdisciplinary mission of time-domain and X-ray astronomy. Equipped with a wide-field lobster-eye X-ray focusing imager, EP will discover cosmic X-ray transients and monitor the X-ray variability of known sources in 0.5-4 keV, at a combination of detecting sensitivity and cadence that is not accessible to the previous and current wide-field monitoring missions. EP can perform quick characterisation of transients or outbursts with a Wolter-I X-ray telescope onboard. In this paper, the science objectives of the Einstein Probe mission are presented. EP is expected to enlarge the sample of previously known or predicted but rare types of transients with a wide range of timescales. Among them, fast extragalactic transients will be surveyed systematically in soft X-rays, which include {\gamma}-ray bursts and their variants, supernova shock breakouts, and the predicted X-ray transients associated with binary neutron star mergers. EP will detect X-ray tidal disruption events and outbursts from active galactic nuclei, possibly at an early phase of the flares for some. EP will monitor the variability and outbursts of X-rays from white dwarfs, neutron stars and black holes in our and neighbouring galaxies at flux levels fainter than those detectable by the current instruments, and is expected to discover new objects. A large sample of stellar X-ray flares will also be detected and characterised. In the era of multi-messenger astronomy, EP has the potential of detecting the possible X-ray counterparts of gravitational wave events, neutrino sources, and ultra-high energy {\gamma}-ray and cosmic ray sources. EP is expected to help advance the studies of extreme objects/phenomena and their underlying physical processes revealed in the dynamic X-ray universe, as well as studies in other areas of X-ray astronomy.

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arXiv2024

First Study of the Supernova Remnant Population in the Large Magellanic Cloud with eROSITA

The study of the entire population of SNRs in a galaxy helps us to understand the underlying stellar populations, the environments, in which the SNRs are evolving, and the stellar feedback on the ISM. The all-sky survey carried out by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board Spektrum-Roentgen-Gamma (Spektr-RG, SRG) has provided us with spatially and spectrally resolved X-ray data of the entire Large Magellanic Cloud (LMC) and its immediate surroundings in the soft X-ray band down to 0.2 keV. We performed a multiwavelength analysis of previously known SNR candidates and newly detected SNRs and SNR candidates. We applied the Gaussian gradient magnitude (GGM) filter to the eROSITA images of the LMC to highlight the edges of the shocked gas in order to find new SNRs. We compared the X-ray images with those of their optical and radio counterparts to investigate the true nature of the extended emission. We used the Magellanic Cloud Emission Line Survey (MCELS) for the optical data. For the radio comparison, we used data from the Australian Square Kilometre Array Pathfinder (ASKAP) survey of the LMC. Using the VISTA survey of the Magellanic Clouds (VMC) we have investigated the possible progenitors of the new SNRs and SNR candidates in our sample. We present the most updated catalogue of SNRs in the LMC. The eROSITA data have allowed us to confirm 1 of the previous SNR candidates and discover 16 new extended sources. We confirm 3 of them as new SNRs, while we propose the remaining 13 as new X-ray SNR candidates. We also present the first analysis of the follow-up XMM-Newton observation of MCSNR J0456-6533 discovered with eROSITA. Among the new candidates, we propose J0614-7251 (4eRASSU J061438.1-725112) as the first X-ray SNR candidate in the outskirts of the LMC.

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arXiv2023

XMM2ATHENA, the H2020 project to improve XMM-Newton analysis software and prepare for Athena

XMM-Newton, a European Space Agency observatory, has been observing the X-ray, ultra-violet and optical sky for 23 years. During this time, astronomy has evolved from mainly studying single sources to populations and from a single wavelength, to multi-wavelength or messenger data. We are also moving into an era of time domain astronomy. New software and methods are required to accompany evolving astronomy and prepare for the next generation X-ray observatory, Athena. Here we present XMM2ATHENA, a programme funded by the European Union's Horizon 2020 research and innovation programme. XMM2ATHENA builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC), including key members of this consortium and the Athena Science ground segment, along with members of the X-ray community. The project is developing and testing new methods and software to allow the community to follow the X-ray transient sky in quasi-real time, identify multi-wavelength or messenger counterparts of XMM-Newton sources and determine their nature using machine learning. We detail here the first milestone delivery of the project, a new online, sensitivity estimator. We also outline other products, including the forthcoming innovative stacking procedure and detection algorithms to detect the faintest sources. These tools will then be adapted for Athena and the newly detected or identified sources will enhance preparation for observing the Athena X-ray sky.

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arXiv2021

The ASKAP-EMU Early Science Project: 888 MHz Radio Continuum Survey of the Large Magellanic Cloud

We present an analysis of a new 120 deg$^{2}$ radio continuum image of the Large Magellanic Cloud (LMC) at 888 MHz with a bandwidth of 288 MHz and beam size of $13\rlap{.}^{\prime\prime}9\times12\rlap{.}^{\prime\prime}1$, from the Australian Square Kilometre Array Pathfinder (ASKAP) processed as part of the Evolutionary Map of the Universe (EMU) survey. The median Root Mean Squared noise is 58 $\mu$Jy beam$^{-1}$. We present a catalogue of 54,612 sources, divided over a GOLD list (30,866 sources) complete down to 0.5 mJy uniformly across the field, a SILVER list (22,080 sources) reaching down to $<$ 0.2 mJy and a BRONZE list (1,666 sources) of visually inspected sources in areas of high noise and/or near bright complex emission. We discuss detections of planetary nebulae and their radio luminosity function, young stellar objects showing a correlation between radio luminosity and gas temperature, novae and X-ray binaries in the LMC, and active stars in the Galactic foreground that may become a significant population below this flux level. We present examples of diffuse emission in the LMC (H II regions, supernova remnants, bubbles) and distant galaxies showcasing spectacular interaction between jets and intracluster medium. Among 14,333 infrared counterparts of the predominantly background radio source population we find that star-forming galaxies become more prominent below 3 mJy compared to active galactic nuclei. We combine the new 888 MHz data with archival Australia Telescope Compact Array data at 1.4 GHz to determine spectral indices; the vast majority display synchrotron emission but flatter spectra occur too. We argue that the most extreme spectral index values are due to variability.

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arXiv2020

New Optically Identified Supernova Remnants in the Large Magellanic Cloud

We present a new optical sample of three Supernova Remnants and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud(LMC). These objects were originally selected using deep H$\alpha$, [SII] and [OIII] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC's main body. Together with previously suggested MCSNR J0541-6659, we confirm the SNR nature for two additional new objects: MCSNR J0522-6740 and MCSNRJ0542-7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [SII]/H$\alpha$ a emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509-6402 to be a special example of the remnant of a possible Type Ia Supernova which is situated some 2$^\circ$ ($\sim 1.75$kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of $\sim 2$. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.

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arXiv2020

A variable ionized disk wind in the black-hole candidate EXO 1846-031

After 34 years, the black-hole candidate EXO 1846-031 went into outburst again in 2019. We investigate its spectral properties in the hard intermediate and the soft states with NuSTAR and Insight-HXMT. A reflection component has been detected in the two spectral states but possibly originating from different illumination spectra: in the intermediate state, the illuminating source is attributed to a hard coronal component, which has been commonly observed in other X-ray binaries, whereas in the soft state the reflection is probably produced by the disk self-irradiation. Both cases support EXO 1846-031 as a low inclination system of ~40 degrees. An absorption line is clearly detected at ~7.2 keV in the hard intermediate state, corresponding to a highly ionized disk wind (log {\xi} > 6.1) with a velocity up to 0.06c. Meanwhile, quasi-simultaneous radio emissions have been detected before and after the X-rays, implying the co-existence of disk winds and jets in this system. Additionally, the observed wind in this source is potentially driven by magnetic forces. The absorption line disappeared in the soft state and a narrow emission line appeared at ~6.7 keV on top of the reflection component, which may be evidence for disk winds, but data with the higher spectral resolution are required to examine this.

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arXiv2020

The evolution of the broadband temporal features observed in the black-hole transient MAXI J1820+070 with Insight-HXMT

We study the evolution of the temporal properties of MAXI 1820+070 during the 2018 outburst in its hard state from MJD 58190 to 58289 with Insight-HXMT in a broad energy band 1-150 keV. We find different behaviors of the hardness ratio, the fractional rms and time lag before and after MJD 58257, suggesting a transition occurred at around this point. The observed time lags between the soft photons in the 1-5 keV band and the hard photons in higher energy bands, up to 150 keV, are frequency-dependent: the time lags in the low-frequency range, 2-10 mHz, are both soft and hard lags with a timescale of dozens of seconds but without a clear trend along the outburst; the time lags in the high-frequency range, 1-10 Hz, are only hard lags with a timescale of tens of milliseconds; first increase until around MJD 58257 and decrease after this date. The high-frequency time lags are significantly correlated to the photon index derived from the fit to the quasi-simultaneous NICER spectrum in the 1-10 keV band. This result is qualitatively consistent with a model in which the high-frequency time lags are produced by Comptonization in a jet.

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arXiv2019

A novel method for component separation of extended sources in X-ray astronomy

In high-energy astronomy, spectro-imaging instruments such as X-ray detectors allow investigation of the spatial and spectral properties of extended sources including galaxy clusters, galaxies, diffuse interstellar medium, supernova remnants and pulsar wind nebulae. In these sources, each physical component possesses a different spatial and spectral signature, but the components are entangled. Extracting the intrinsic spatial and spectral information of the individual components from this data is a challenging task. Current analysis methods do not fully exploit the 2D-1D (x,y,E) nature of the data, as the spatial and spectral information are considered separately. Here we investigate the application of a Blind Source Separation algorithm that jointly exploits the spectral and spatial signatures of each component in order to disentangle them. We explore the capabilities of a new BSS method (General Morphological Component Analysis; GMCA), initially developed to extract an image of the Cosmic Microwave Background from Planck data, in an X-ray context. The performance of GMCA on X-ray data is tested using Monte-Carlo simulations of supernova remnant toy models, designed to represent typical science cases. We find that GMCA is able to separate highly entangled components in X-ray data even in high contrast scenarios, and can extract with high accuracy the spectrum and map of each physical component. A modification is proposed to improve the spectral fidelity in the case of strongly overlapping spatial components, and we investigate a resampling method to derive realistic uncertainties associated to the results of the algorithm. Applying the modified algorithm to the deep Chandra observations of Cassiopeia A, we are able to produce detailed maps of the synchrotron emission at low energies (0.6-2.2 keV), and of the red/blue shifted distributions of a number of elements including Si and Fe K.

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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 $\gamma$-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 $\gamma$-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 $\lesssim 20~\mu$G. Upper limits on the confidence intervals of three sectors reached $\gtrsim 30~\mu$G though these were poorly constrained. The generally low $B$-field values suggests a leptonic-dominated origin for the TeV $\gamma$-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) $\mu$G which is again consistent with the leptonic TeV $\gamma$-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 $\gamma$-rays.

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arXiv2018

X-Ray Luminosity and Size Relationship of Supernova Remnants in the LMC

The Large Magellanic Cloud (LMC) has $\sim$60 confirmed supernova remnants (SNRs). Because of the known distance, 50 kpc, the SNRs' angular sizes can be converted to linear sizes, and their X-ray observations can be used to assess X-ray luminosities ($L_X$). We have critically examined the LMC SNRs' sizes reported in the literature to determine the most plausible sizes. These sizes and the $L_X$ determined from \emph{XMM-Newton} observations are used to investigate their relationship in order to explore the environmental and evolutionary effects on the X-ray properties of SNRs. We find: (1) Small LMC SNRs, a few to 10 pc in size, are all of Type Ia with $L_X>10^{36}$ ergs s$^{-1}$. The scarcity of small core-collapse (CC) SNRs is a result of CCSNe exploding in the low-density interiors of interstellar bubbles blown by their massive progenitors during their main sequence phase. (2) Medium-sized (10-30 pc) CC SNRs show bifurcation in $L_X$, with the X-ray-bright SNRs either in an environment associated with molecular clouds or containing pulsars and pulsar wind nebulae and the X-ray-faint SNRs being located in low-density interstellar environments. (3) Large (size$>$30 pc) SNRs show a trend of $L_X$ fading with size, although the scatter is large. The observed relationship between $L_X$ and sizes can help constrain models of SNR evolution.

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arXiv2017

Statistical Analysis of Supernova Remnants in the Large Magellanic Cloud

We construct the most complete sample of supernova remnants (SNRs) in any galaxy - the Large Magellanic Cloud (LMC) SNR sample. We study their various properties such as spectral index ($α$), size and surface-brightness. We suggest an association between the spatial distribution, environment density of LMC SNRs and their tendency to be located around supergiant shells. We find evidence that the 16 known type Ia LMC SNRs are expanding in a lower density environment compared to the Core-Collapse (CC) type. The mean diameter of our entire population (74) is 41 pc, which is comparable to nearby galaxies. We didn't find any correlation between the type of SN explosion, ovality or age. The $N(<D)$ relationship of $a={0.96}$ implies that the randomised diameters are readily mimicking such an exponent. The rate of SNe occurring in the LMC is estimated to be $\sim$1 per 200 yr. The mean $α$ of the entire LMC SNR population is $α=-0.52$, which is typical of most SNRs. However, our estimates show a clear flattening of the synchrotron $α$ as the remnants age. As predicted, our CC SNRs sample are significantly brighter radio emitters than the type Ia remnants. We also estimate the $Σ- D$ relation for the LMC to have a slope $\sim3.8$ which is comparable with other nearby galaxies. We also find the residency time of electrons in the galaxy ($4.0-14.3$ Myr), implying that SNRs should be the dominant mechanism for the production and acceleration of CRs.

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arXiv2016

Fe K and ejecta emission in SNR G15.9+0.2 with XMM-Newton

Aims: We present a study of the Galactic supernova remnant SNR G15.9+0.2 with archival XMM-Newton observations. Methods: EPIC data are used to investigate the morphological and spectral properties of the remnant, searching in particular for supernova ejecta and Fe K line emission. By comparing the SNR's X-ray absorption column density with the atomic and molecular gas distribution along the line of sight, we attempt to constrain the distance to the SNR. Results: Prominent line features reveal the presence of ejecta. Abundance ratios of Mg, Si, S, Ar, and Ca strongly suggest that the progenitor of SNR G15.9+0.2 was a massive star with a main sequence mass likely in the range 20-25 $M_{\odot}$, strengthening the physical association with a candidate central compact object detected with Chandra. Using EPIC's collective power, Fe K line emission from SNR G15.9+0.2 is detected for the first time. We measure the line properties and find evidence for spatial variations. We discuss how the source fits within the sample of SNRs with detected Fe K emission and find that it is the core-collapse SNR with the lowest Fe K centroid energy. We also present some caveats regarding the use of Fe K line centroid energy as a typing tool for SNRs. Only a lower limit of 5 kpc is placed on the distance to SNR G15.9+0.2, constraining its age to $t_{SNR} \gtrsim 2$ kyr.

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arXiv2015

Two evolved supernova remnants with newly identified Fe-rich cores in the Large Magellanic Cloud

Aims. We present a multi-wavelength analysis of the evolved supernova remnants MCSNR J0506-7025 and MCSNR J0527-7104 in the Large Magellanic Cloud. Methods. We used data from XMM-Newton, the Australian Telescope Compact Array, and the Magellanic Cloud Emission Line Survey to study their broadband emission and used Spitzer and HI data to gain a picture of their environments. We performed a multi-wavelength morphological study and detailed radio and X-ray spectral analyses to determine their physical characteristics. Results. Both remnants were found to have bright X-ray cores, dominated by Fe L-shell emission, consistent with reverse shock heated ejecta with determined Fe masses in agreement with Type Ia explosion yields. A soft X-ray shell, consistent with swept-up interstellar medium, was observed in MCSNR J0506-7025, suggestive of a remnant in the Sedov phase. Using the spectral fit results and the Sedov self-similar solution, we estimated the age of MCSNR J0506-7025 to be ~16-28 kyr, with an initial explosion energy of (0.07-0.84)x10^51 erg. A soft shell was absent in MCSNR J0527-7104, with only ejecta emission visible in an extremely elongated morphology extending beyond the optical shell. We suggest that the blast wave has broken out into a low density cavity, allowing the shock heated ejecta to escape. We found that the radio spectral index of MCSNR J0506-7025 is consistent with the standard ~0.5 for SNRs. Radio polarisation at 6 cm indicates a higher degree of polarisation along the western front and at the eastern knot, with a mean fractional polarisation across the remnant of P~(20 \pm 6)%. Conclusions. The detection of Fe-rich ejecta in the remnants suggests that both resulted from Type Ia explosions. The newly identified Fe-rich cores in MCSNR J0506-7025 and MCSNR J0527-7104 makes them members of the expanding class of evolved Fe-rich remnants in the Magellanic Clouds.

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