arXiv subjects

Patrick J. Kavanagh

Publications and source records attributed to Patrick J. Kavanagh.

29 records · Page 2Linked to original sources

arXiv2021

European Historical Evidence of the Supernova of AD 1054 Balkan Medieval Tombstones

In a previous work, we establish that the acclaimed 'Arabic' records of SN 1054 from ibn Butlan originate from Europe. Also, we reconstructed the European sky at the time of the event and find that the 'new star' (SN 1054) was in the west while the planet Venus was on the opposite side of the sky (in the east) with the Sun sited directly between these two equally bright objects, as documented in East-Asian records. Here, we investigate the engravings on tombstones (stećci) from several necropolises in present-day Bosnia and Herzegovina (far from the influence of the Church) as a possible European 'record' of SN 1054. Certainly, knowledge and understanding of celestial events (such as supernovae) were somewhat poor in the mid-XI century.

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arXiv2021

European Historical Evidence Of The Supernova Of Ad 1054 Sky Above Europe On 4th July 1054

We investigate possible reasons for the absence of historical records of the supernova of 1054 in Europe. At the same time, we search for the new evidences as well. We establish that the previously acclaimed 'Arabic' records from ibn Butlan originate from Europe. As one of the most prominent scientists of the era, he was in Constantinople at the time of the supernova and actively participated in the medieval Church feud known as the Great Schism. Next, we reconstruct the European sky at the time of the event and find that the 'new star' (SN 1054) was in the west while the planet Venus was on the opposite side of the sky (in the east) with the Sun sited directly between these two equally bright objects, as documented in East-Asian records.

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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$α$, [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$α$ 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

The nature of point source fringes in mid-infrared spectra acquired with the James Webb Space Telescope

The constructive and destructive interference in different layers of the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) detector arrays modulate the detected signal as a function of wavelength. Additionally, sources of different spatial profiles show different fringe patterns. Dividing by a static fringe flat could hamper the scientific interpretation of sources whose fringes do not match that of the fringe flat. We find point source fringes measured by the MIRI Medium-Resolution Spectrometer (MRS) to be reproducible under similar observing conditions. We want, thus, to identify the variables, if they exist, that would allow for a parametrization of the signal variations induced by point source fringe modulations. We do this by analyzing MRS detector plane images acquired on the ground. We extracted the fringe profile of multiple point source observations and studied the amplitude and phase of the fringes as a function of field position and pixel sampling of the point spread function of the optical chain. A systematic variation in the amplitude and phase of the point source fringes is found over the wavelength range covered by the test sources (4.9-5.8 $μ$m). The variation depends on the fraction of the point spread function seen by the detector pixel. We identify the non-uniform pixel illumination as the root cause of the reported systematic variation. We report an improvement after correction of 50% on the 1$σ$ standard deviation of the spectral continuum. A 50% improvement is also reported in line sensitivity for a benchmark test with a spectral continuum of 100 mJy. The improvement in the shape of weak lines is illustrated using a T Tauri model spectrum. Consequently, we verify that fringes of extended sources and potentially semi-extended sources and crowded fields can be simulated by combining multiple point source fringe transmissions.

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arXiv2020

Deep XMM-Newton observations of the northern disk of M31 II: Tracing the hot interstellar medium

Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disk of M 31 is similar to other galaxy disks.

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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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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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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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arXiv2014

Multi-frequency study of DEM L299 in the Large Magellanic Cloud

We have studied the HII region DEM L299 in the Large Magellanic Cloud to understand its physical characteristics and morphology in different wavelengths. We performed a spectral analysis of archived XMM-Newton EPIC data and studied the morphology of DEM L299 in X-ray, optical, and radio wavelengths. We used H alpha, [SII], and [OIII] data from the Magellanic Cloud Emission Line Survey and radio 21 cm line data from the Australia Telescope Compact Array (ATCA) and the Parkes telescope, and radio continuum data from ATCA and the Molonglo Synthesis Telescope. Our morphological studies imply that, in addition to the supernova remnant SNR B0543-68.9 reported in previous studies, a superbubble also overlaps the SNR in projection. The position of the SNR is clearly defined through the [SII]/H alpha flux ratio image. Moreover, the optical images show a shell-like structure that is located farther to the north and is filled with diffuse X-ray emission, which again indicates the superbubble. Radio 21 cm line data show a shell around both objects. Radio continuum data show diffuse emission at the position of DEM L299, which appears clearly distinguished from the HII region N 164 that lies south-west of it. We determined the spectral index of SNR B0543-68.9 to be alpha=-0.34, which indicates the dominance of thermal emission and therefore a rather mature SNR. We determined the basic properties of the diffuse X-ray emission for the SNR, the superbubble, and a possible blowout region of the bubble, as suggested by the optical and X-ray data. We obtained an age of 8.9 (3.5-18.1) kyr for the SNR and a temperature of 0.64 (0.44-1.37) keV for the hot gas inside the SNR, and a temperature of the hot gas inside the superbubble of 0.74 (0.44-1.1) keV. We conclude that DEM L299 consists of a superposition of SNR B0543-68.9 and a superbubble, which we identified based on optical data.

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arXiv2012

Multiwavelength study of the newly confirmed supernova remnant MCSNR J0527-7104 in the Large Magellanic Cloud

The Large Magellanic Cloud (LMC) hosts a rich and varied population of supernova remnants (SNRs). Optical, X-ray, and radio observations are required to identify these SNRs, as well as to ascertain the various processes responsible for the large array of physical characteristics observed. In this paper we attempted to confirm the candidate SNR [HP99] 1234, identified in X-rays with ROSAT, as a true SNR by supplementing these X-ray data with optical and radio observations. Optical data from the Magellanic Cloud Emission Line Survey (MCELS) and new radio data from the Molonglo Observatory Synthesis Telescope (MOST), in addition to the ROSAT X-ray data, were used to perform a morphological analysis of this candidate SNR. An approximately ellipsoidal shell of enhanced [SII], typical of an SNR ([SII]/Halpha > 0.4), was detected in the optical. This enhancement is coincident with faint radio emission at 36 cm. Using the available data we estimated the size of the remnant to be ~5.1' x 4.0' (~75 pc x 59 pc). However, the measurement along the major-axis was somewhat uncertain due to a lack of optical and radio emission at its extremities and the poor resolution of the X-ray data. Assuming this SNR is in the Sedov phase and adopting the ambient mass density of 1.2x10^-25 g cm^-3 measured in a nearby HII region, an age estimate of ~25 kyr was calculated for a canonical initial explosion energy of 10^51 erg. However, this age estimate should be treated cautiously due to uncertainties on the adopted parameters. Analysis of the local stellar population suggested a type Ia event as a precursor to this SNR, however, a core-collapse mechanism could not be ruled out due to the possibility of the progenitor being a runaway massive star. With the detection of X-ray, radio and optical line emission with enhanced [SII], this object was confirmed as an SNR and we assign the identifier MCSNR J0527-7104.

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arXiv2012

XMM-Newton view of the N 206 superbubble in the Large Magellanic Cloud

We perform an analysis of the X-ray superbubble in the N 206 HII region in the Large Magellanic Cloud using current generation facilities to gain a better understanding of the physical processes at work in the superbubble and to improve our knowledge of superbubble evolution. We used XMM-Newton observations of the N 206 region to produce images and extract spectra of the superbubble diffuse emission. Morphological comparisons with Halpha images from the Magellanic Cloud Emission Line Survey were performed, and spectral analysis of the diffuse X-ray emission was carried out. We derived the physical properties of the hot gas in the superbubble based on the results of the spectral analysis. We also determined the total energy stored in the superbubble and compared this to the expected energy input from the stellar population to assess the superbubble growth rate discrepancy for N 206. We find that the brightest region of diffuse X-ray emission is confined by a Halpha shell, consistent with the superbubble model. In addition, faint emission extending beyond the Halpha shell was found, which we attribute to a blowout region. The spectral analysis of both emission regions points to a hot shocked gas as the likely origin of the emission. We determine the total energy stored in the bubble and the expected energy input by the stellar population. However, due to limited data on the stellar population, the input energy is poorly constrained and, consequently, no definitive indication of a growth rate discrepancy is seen. Using the high-sensitivity X-ray data from XMM-Newton and optical data from the Magellanic Cloud Emission Line Survey has allowed us to better understand the physical properties of the N 206 superbubble and address some key questions of superbubble evolution.

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