arXiv subjects

X. J. Yang

Publications and source records attributed to X. J. Yang.

At least 19 recordsLinked to original sources

arXiv2026

Widespread Detection of Aromatic and Aliphatic Emission in the Dual Quasar J0749+2255 at Cosmic Noon

Based on JWST/MIRI integral field observations, we report a widespread detection of aromatic and aliphatic hydrocarbon emission at rest-frame 3.3 and 3.4 micron in SDSSJ074922.96+225511.7 (hereafter J0749+2255), a dual quasar at redshift z~2.17, corresponding to a cosmic age of ~3 billion years after the Big Bang, a time period known as the "cosmic noon" when star formation and black hole growth peak. With the 3.3 micron emission ascribed to aromatic C--H stretches of small PAH molecules and the 3.4 micron emission assigned to aliphatic C--H stretches of aliphatic sidegroups attached to PAHs, we utilize the observed intensities of the 3.3 and 3.4 micron emission bands to estimate the aliphatic fractions of PAHs and their variations across J0749+2255, which is, to our knowledge, the most distant object to date in which both aromatics and aliphatics have ever been detected. We find that both the 3.3 and 3.4 micron emission bands are pronounced and the aliphatic fractions are surprisingly high in the most luminous regions centered on the two quasar nuclei, suggesting that not only small PAHs (of ~20--30 carbon atoms) but also their attached aliphatic sidegroups survive in intense ultraviolet radiation arising from extreme starburst.

astro-ph.GA↗

arXiv2024

Tracing Rayleigh-Taylor instability from measured periodic modulation in laser driven proton beams

Rayleigh-Taylor (RT) instability occurs in a variety of scenario as a consequence of fluids of different densities pushing against the density gradient. For example, it is expected to occur in the ion acceleration of solid density targets driven by high intensity lasers and is crucial for the acceleration process. Yet, it is essential to understand the dynamics of the RT instability, a typical way to measure this phenomenon requires sophisticated diagnostics such as streak X ray radiography. Here, we report on experimental observation on periodic modulation in the energy spectrum of laser accelerated proton beams. Interestingly, theoretical model and two-dimensional particle-in-cell simulations, in good agreement with the experimental finding, indicated that such modulation is associated with periodic modulated electron density induced by transverse Rayleigh-Taylor-like instability. Furthermore, the correlation between the RT instability and the ion acceleration provides an interpretation to trace the development of the RT instability from the modulated proton spectrum. Our results thus suggest a possible tool to diagnose the evolution of the RT instability, and may have implications for further understanding for the accelerating mechanisms as well as optimization strategies for laser driven ion acceleration.

physics.plasm-ph↗

arXiv2024

Where Have All the Sulfur Atoms Gone? Polycyclic Aromatic Hydrocarbon as a Possible Sink for the Missing Sulfur in the Interstellar Medium. I. The C--S Band Strengths

Despite its biogeneic and astrochemical importance, sulfur (S), the 10th most abundant element in the interstellar medium (ISM) with a total abundance of S/H~2.2E-5, largely remains undetected in molecular clouds. Even in the diffuse ISM where S was previously often believed to be fully in the gas phase, in recent years observational evidence has suggested that S may also be appreciably depleted from the gas. What might be the dominant S reservoir in the ISM remains unknown. Solid sulfides like MgS, FeS and SiS_2 are excluded as a major S reservoir due to the undetection of their expected infrared spectral bands in the ISM. In this work, we explore the potential role of sulfurated polycyclic aromatic hydrocarbon (PAH) molecules -- PAHs with sulfur heterocycles (PASHs) -- as a sink for the missing S. Utilizing density function theory, we compute the vibrational spectra of 18 representative PASH molecules. It is found that these molecules exhibit a prominent, C--S stretching band at ~10 micron and two relatively weak, C--S deformation bands at 15 and 25 micron that are not mixed with the nominal PAH bands at 6.2, 7.7, 8.6, 11.3 and 12.7 micron If several parts per million of S (relative to H) are locked up in PAHs, the 10 micron C--S band would be detectable by Spitzer and JWST. To quantitatively explore the amount of S/H depleted in PASHs, detailed comparison of the infrared emission spectra of PASHs with the Spitzer and JWST observations is needed.

astro-ph.GA↗

arXiv2024

Investigation into the origin of the soft excess in Ark 564 using principal component analysis

We combined a principal component analysis (PCA) and spectroscopy to investigate the origin of the soft excess in narrow-line Seyfert 1 galaxy Ark 564 with XMM-Newton observations over a period of ten years. We find that the principal components in different epochs are very similar, suggesting stable variability patterns in this source. More importantly, although its spectra could be equally well fitted by the two soft excess models, simulations show that the principal components from the relativistically smeared reflection model match the data well. At the same time, the principal components from the warm corona model show significant inconsistency. This finding indicates that the soft excess in Ark 564 originates from the relativistically smeared reflection, rather than the Comptonization in the warm corona, thereby favoring the reflection origin or the "hybrid" origin of the soft excess. Furthermore, the presence of the narrow absorption features in the spectra suggests that the soft excess is unlikely to originate from absorptions due to possible outflowing winds. Our results indicate that the PCA coupled with spectral analysis is a promising approach to exploring the origin of the soft excess in active galactic nuclei (AGNs).

astro-ph.HE↗

arXiv2023

Polycyclic Aromatic Hydrocarbon Molecules and the 2175 Angstrom Interstellar Extinction Bump

The exact nature of the 2175 Angstrom extinction bump, the strongest spectroscopic absorption feature superimposed on the interstellar extinction curve, remains unknown ever since its discovery in 1965. Popular candidate carriers for the extinction bump include nano-sized graphitic grains and polycyclic aromatic hydrocarbon (PAH) molecules. To quantitatively evaluate PAHs as a possible carrier, we perform quantum chemical computations for the electronic transitions of 30 compact, pericondensed PAH molecules and their cations as well as anions with a wide range of sizes from 16 to 96 C atoms and a mean size of 43 C atoms. It is found that a mixture of such PAHs, which individually exhibit sharp absorption features, show a smooth and broad absorption band that resembles the 2175 Angstrom interstellar extinction bump. Arising from π^{*} --π, the width and intensity of the absorption bump for otherwise randomly-selected and uniformly-weighted PAH mixtures, do not vary much with PAH sizes and charge states, whereas the position shifts to longer wavelengths as PAH size increases. While the computed bump position, with the computational uncertainty taken into account, appears to agree with that of the interstellar extinction bump, the computed width is considerably broader than the interstellar bump if the molecules are uniformly weighted. It appears that, to account for the observed bump width, one has to resort to PAH species of specific sizes and structures.

astro-ph.GA↗

arXiv2023

The 2175 Angstrom Interstellar Extinction Bump: Is the Wavelength Variable?

The most striking characteristics of the mysterious 2175 Angstrom extinction bump, the strongest spectroscopic absorption feature seen on the interstellar extinction curve, are the invariant central wavelength and variable bandwidth: its peak position at 2175 Angstrom is remarkably constant while its bandwidth varies from one line of sight to another. However, recent studies of the lines of sight toward a number of Herbig Ae/Be stars have revealed that the extinction bump exhibits substantial shifts from the canonical wavelength of 2175 Angstrom. In this work we revisit these lines of sight and take a physical approach to determine the ultraviolet (UV) extinction curve for each line of sight. It is found that the wavelengths of the derived UV extinction bumps are around 2200 Angstrom and the scatters are considerably smaller than that of the previous study based on the same set of Herbig Ae/Be stars, consistent with the conventional wisdom. Nevertheless, the scatters are still appreciably larger than that associated with the nominal bump position of 2175 Angstrom. This is discussed in the context that Herbig Ae/Be stars are not well-suited for interstellar extinction studies.

astro-ph.GA↗

arXiv2023

Aliphatics and Aromatics in the Universe: The Pre-JWST Era

The so-called "unidentified infrared emission" (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micron ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs often have an aliphatic component (e.g., aliphatic sidegroups like methyl --CH3 may be attached as functional groups to PAHs) as revealed by the detection in many UIE sources of the aliphatic C--H stretching feature at 3.4 micron. With its unprecedented sensitivity, unprecedented spatial resolution and high spectral resolution, the James Webb Space Telescope (JWST) holds great promise for evolutionizing the studies of aliphatics and aromatics in the universe. To facilitate analyzing JWST observations, we present a theoretical framework for determining the aliphatic fractions (η_ali) of PAHs, the fractions of C atoms in aliphatic units, from the emission intensity ratios of the 3.4 micron feature to the 3.3 micron feature. To demonstrate the effectiveness of this framework, we compile the 3.3 and 3.4 micron UIE data obtained in the pre-JWST era for an as complete as possible sample, and then apply the framework to these pre-JWST data. We derive a median aliphatic fraction of <η_ali>=5.4\% and find that the aliphatic fractions are the highest in protoplanetary nebulae illuminated by cool stars lacking ultraviolet radiation. Nevertheless, the "hardness" of stellar photons is not the only factor affecting the PAH aliphaticity, other factors such as the starlight intensity may also play an important role.

astro-ph.GA↗

arXiv2023

Deuterated Polycyclic Aromatic Hydrocarbons in the Interstellar Medium: The Aliphatic C--D Band Strengths

Deuterium (D) was exclusively generated in the Big Bang and the standard Big Bang Nucleosynthesis (BBN) model predicts a primordial abundance of D/H~26ppm. As the Galaxy evolves, D/H gradually decreases because of astration. The Galactic chemical evolution (GCE) model predicts a present-day abundance of D/H~20ppm. However, observations of the local interstellar medium (ISM) have revealed that the gas-phase interstellar D/H varies considerably from one region to another and has a median abundance of D/H~13ppm, substantially lower than predicted from the BBN and GCE models. It has been suggested that the missing D atoms of D/H~7ppm could have been locked up in deuterated polycyclic aromatic hydrocarbon (PAH) molecules. However, we have previously demonstrated that PAHs with aromatic C--D units are insufficient to account for the missing D. Here we explore if PAHs with aliphatic C--D units could be a reservoir of D. We perform quantum chemical computations of the vibrational spectra of "superdeuterated" PAHs (in which one D and one H share an C atom) and PAHs attached with D-substituted methyl group, and derive the band strengths of the aliphatic C--D stretch (A_4.65). By applying the computationally derived A_4.65 to the observed aliphatic C--D emission at ~4.6--4.8 micron, we find that PAHs with aliphatic C--D units could have tied up a substantial amount of D/H and marginally account for the missing D. The possible routes to generate PAHs with aliphatic C--D units are also discussed.

astro-ph.GA↗

arXiv2021

Search for Gamma-Ray Bursts and Gravitational Wave Electromagnetic Counterparts with High Energy X-ray Telescope of \textit{Insight}-HXMT

The High Energy X-ray telescope (HE) on-board the Hard X-ray Modulation Telescope (\textit{Insight}-HXMT) can serve as a wide Field of View (FOV) gamma-ray monitor with high time resolution ($μ$s) and large effective area (up to thousands cm$^2$). We developed a pipeline to search for Gamma-Ray Bursts (GRBs), using the traditional signal-to-noise ratio (SNR) method for blind search and the coherent search method for targeted search. By taking into account the location and spectrum of the burst and the detector response, the targeted coherent search is more powerful to unveil weak and sub-threshold bursts, especially those in temporal coincidence with Gravitational Wave (GW) events. Based on the original method in literature, we further improved the coherent search to filter out false triggers caused by spikes in light curves, which are commonly seen in gamma-ray instruments (e.g. \textit{Fermi}/GBM, \textit{POLAR}). We show that our improved targeted coherent search method could eliminate almost all false triggers caused by spikes. Based on the first two years of \textit{Insight}-HXMT/HE data, our targeted search recovered 40 GRBs, which were detected by either \textit{Swift}/BAT or \textit{Fermi}/GBM but too weak to be found in our blind search. With this coherent search pipeline, the GRB detection sensitivity of \textit{Insight}-HXMT/HE is increased to about 1.5E-08 erg/cm$^2$ (200 keV$-$3 MeV). We also used this targeted coherent method to search \textit{Insight}-HXMT/HE data for electromagnetic (EM) counterparts of LIGO-Virgo GW events (including O2 and O3a runs). However, we did not find any significant burst associated with GW events.

astro-ph.HE↗

arXiv2021

The harmonic component of the millihertz quasi-periodic oscillations in 4U 1636-53

We studied the harmonics of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636-53 using the Rossi X-ray Timing Explorer observations. We detected the harmonics of the mHz QPOs in 73 data intervals, with most of them in the transitional spectra state. We found that the ratio between the rms amplitude of the harmonic and that of the fundamental remains constant in a wide range of the fundamental frequency. More importantly, we studied, for the first time, the rms amplitude of the harmonics vs. energy in 4U 1636-53 in the 2-5 keV range. We found that the rms amplitude of both the harmonic and the fundamental shows a decreasing trend as the energy increases, which is different from the behaviors reported in QPOs in certain black hole systems. Furthermore, our results suggest that not all observations with mHz QPOs have the harmonic component, although the reason behind this is still unclear.

astro-ph.HE↗

arXiv2021

Deuterated Polycyclic Aromatic Hydrocarbons in the Interstellar Medium: The C--D Band Strengths of Multi-Deuterated Species

Observationally, the interstellar gas-phase abundance of deuterium (D) is considerably depleted and the missing D atoms are often postulated to have been locked up into carbonaceous solids and polycyclic aromatic hydrocarbon (PAH) molecules. An accurate knowledge of the fractional amount of D (relative to H) tied up in carbon dust and PAHs has important cosmological implications since D originated exclusively from the Big Bang and the present-day D abundance, after accounting for the astration it has experienced during the Galactic evolution, provides essential clues to the primordial nucleosynthesis and the cosmological parameters. To quantitatively explore the extent to which PAHs could possibly accommodate the observed D depletion, we have previously quantum-chemically computed the infrared vibrational spectra of mono-deuterated PAHs and derived the mean intrinsic band strengths of the 3.3 $μ$m C--H stretch (A$_{3.3}$) and the 4.4 $μ$m C--D stretch (A$_{4.4}$). Here we extend our previous work to multi-deuterated PAH species of different deuterations, sizes and structures. We find that both the intrinsic band strengths A$_{3.3}$ and A$_{4.4}$ and their ratios A$_{4.4}$/A$_{3.3}$ not only show little variations among PAHs of different deuterations, sizes and structures, they are also closely similar to that of mono-deuterated PAHs. Therefore, a PAH deuteration level (i.e., the fraction of peripheral atoms attached to C atoms in the form of D) of ~2.4% previously estimated from the observed 4.4 $μ$m to 3.3 $μ$m band ratio based on the A$_{4.4}$/A$_{3.3}$ ratio of mono-deuterated PAHs is robust.

astro-ph.GA↗

arXiv2020

Deuterated Polycyclic Aromatic Hydrocarbons in the Interstellar Medium: The C--D Band Strengths of Mono-Deuterated Species

Deuterium (D) is one of the light elements created in the big bang. As the Galaxy evolves, the D/H abundance in the interstellar medium (ISM) decreases from its primordial value due to "astration". However, the observed gas-phase D/H abundances of some interstellar sightlines are substantially lower than the expected reduction by astration alone. The missing D could have been depleted onto polycyclic aromatic hydrocarbon (PAH) molecules which are ubiquitous and abundant in interstellar regions. To quantitatively explore the hypothesis of PAHs as a possible reservoir of interstellar D, we compute quantum-chemically the infrared vibrational spectra of mono-deuterated PAHs (and their cations) of various sizes. We find that, as expected, when H in PAHs is replaced by D, the C-H stretching and bending modes at 3.3, 8.6 and 11.3 $μ$m respectively shift to longer wavelengths at $\sim$4.4, 11.4 and 15.4 $μ$m by a factor of $\sim$$\sqrt{13/7}$, the difference in reduced mass between the C-H and C-D oscillators. We derive from the computed spectra the mean intrinsic strengths of the 3.3 $μ$m C-H stretch and 4.4 $μ$m C--D stretch to be $\langle A_{3.3} \rangle \sim 13.4$ km/mol and $\langle A_{4.4} \rangle \sim 7.4$ km/mol for neutral deuterated PAHs which would dominate the interstellar 3.3 and 4.4 $μ$m emission. By comparing the computationally-derived mean ratio of $\langle A_{4.4}/A_{3.3} \rangle \sim 0.56$ for neutral PAHs with the mean ratio of the observed intensities of $\langle (I_{4.4}/I_{3.3})_{\rm obs} \rangle \sim 0.019$, we estimate the degree of deuteration (i.e., the fraction of peripheral atoms attached to C in the form of D) to be ~2.4\%, corresponding to a D-enrichment of a factor of ~1200 with respect to the interstellar D/H abundance.

astro-ph.GA↗

arXiv2020

Superhydrogenated Polycyclic Aromatic Hydrocarbon Molecules: Vibrational Spectra in the Infrared

Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) may be present in H-rich and ultraviolet-poor benign regions. The addition of excess H atoms to PAHs converts the aromatic bonds into aliphatic bonds, the strongest of which falls near 3.4 $μ$m. Therefore, superhydrogenated PAHs are often hypothesized as a carrier of the 3.4 $μ$m emission feature which typically accompanies the stronger 3.3 $μ$m aromatic C--H stretching feature. To assess this hypothesis, we use density function theory to compute the IR vibrational spectra of superhydrogenated PAHs and their ions of various sizes (ranging from benzene, naphthalene to perylene and coronene) and of various degrees of hydrogenation (ranging from minimal hydrogenation to heavy hydrogenation). For each molecule, we derive the intrinsic oscillator strengths of the 3.3 $μ$m aromatic C--H stretch ($A_{3.3}$) and the 3.4 $μ$m aliphatic C--H stretch ($A_{3.4}$). By comparing the computationally-derived mean ratio of $\langle A_{3.4}/A_{3.3}\rangle\sim1.98$ with the mean ratio of the observed intensities $\langle I_{3.4}/I_{3.3}\rangle\sim0.12$, we find that the degree of superhydrogenation --- the fraction of C atoms attached with excess H atoms --- is only $\sim2.2\%$ for neutral PAHs which predominantly emit the 3.3 and 3.4 $μ$m features. We also determine for each molecule the intrinsic band strengths of the 6.2 $μ$m aromatic C--C stretch ($A_{6.2}$) and the 6.85 $μ$m aliphatic C--H deformation ($A_{6.85}$). We derive the degree of superhydrogenation from the mean ratio of the observed intensities $\langle I_{6.85}/I_{6.2}\rangle\sim0.10$ and $\langle A_{6.85}/A_{6.2}\rangle\sim1.53$ for neutrals and $\langle A_{6.85}/A_{6.2}\rangle\sim1.23$ for cations to be $\lesssim 3.1\%$ for neutrals and $\lesssim 8.6\%$ for cations. We conclude that astrophysical PAHs are primarily aromatic and are only marginally superhydrogenated.

astro-ph.GA↗

arXiv2019

Unusual Infrared Emission toward Sgr B2: Possible Planar C$_{24}$

Interstellar graphene could be present in the interstellar medium (ISM), resulting from the photochemical processing of polycyclic aromatic hydrocarbon (PAH) molecules and/or collisional fragmentation of graphitic particles. Indeed, by comparing the observed ultraviolet (UV) extinction and infrared (IR) emission of the diffuse ISM with that predicted for graphene, as much as $\sim$ 2% of the total interstellar carbon could have been locked up in graphene without violating the observational constraints. While the possible detection of planar C$_{24}$, a small piece of a graphene sheet, has been reported towards several Galactic and extragalactic planetary nebulae, graphene has not yet been detected in interstellar environments. In this work, we search for the characteristic IR features of C$_{24}$ at $\sim$ 6.6, 9.8, 20 $μm$ toward Sgr B2, a high-mass star formation region, and find a candidate target toward R.A. (J2000) = $267^{\circ}.05855$ and Decl. (J2000) = $-28^{\circ}.01479$ in Sgr B2 whose Spitzer/IRS spectra exhibit three bands peaking at $\sim$ 6.637, 9.853 and 20.050 $μm$ which appear to be coincident with that of C$_{24}$. Possible features of C$_{60}$ are also seen in this region. The candidate region is a warm dust environment heated by massive stars or star clusters, associated with a WISE spot (a tracer of star-formation activity), close to the HII region candidate IRAS 17450-2759, and is surrounded by seven young stellar object candidates within $\sim$ 5$^{\prime}$, suggesting that the creation and/or excitation of C$_{24}$ could be related to star formation activities.

astro-ph.GA↗

arXiv2016

Bulk and surface electronic structure of trigonal structured PtBi2 studied by angle-resolved photoemission spectroscopy

PtBi2 with a layered trigonal crystal structure was recently reported to exhibit an unconventional large linear magnetoresistance, while the mechanism involved is still elusive. Using high resolution angle-resolved photoemission spectroscopy, we present a systematic study on its bulk and surface electronic structure. Through careful comparison with first-principle calculations, our experiment distinguishes the low-lying bulk bands from entangled surface states, allowing the estimation of the real stoichiometry of samples. We find significant electron doping in PtBi2, implying a substantial Bi deficiency induced disorder therein. We discover a Dirac-cone-like surface state on the boundary of the Brillouin zone, which is identified as an accidental Dirac band without topological protection. Our findings exclude quantum-limit-induced linear band dispersion as the cause of the unconventional large linear magnetoresistance.

cond-mat.str-el↗

arXiv2016

Pd site doping effect on superconductivity in Nb2Pd0.76S5

Pd site doping effect on superconductivity was investigated in quasi-one-dimensional superconductor Nb2(Pd1-xRx)0.76S5 (R=Ir, Ag) by measuring resistivity, magnetic susceptibility and Hall effect. It was found that superconducting transition temperature (Tc) is firstly slightly enhanced by partial substitution of Pd with Ir and then it is suppressed gradually as Ir content increases further. Meanwhile Ag substitution quickly suppresses the system to a nonsuperconducting ground state. Hall effect measurements indicate the variations of charge carrier density caused by Ir or Ag doping. The established phase diagram implies that the charge carrier density (or the band filling) could be one of the crucial controlling factors to determine Tc in this system.

cond-mat.supr-con↗

arXiv2013

The Carriers of the Interstellar Unidentified Infrared Emission Features: Constraints from the Interstellar C-H Stretching Features at 3.2-3.5 Micrometers

The unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micrometer, commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules, have been recently ascribed to mixed aromatic/aliphatic organic nanoparticles. More recently, an upper limit of <9% on the aliphatic fraction (i.e., the fraction of carbon atoms in aliphatic form) of the UIE carriers based on the observed intensities of the 3.4 and 3.3 micrometer emission features by attributing them to aliphatic and aromatic C-H stretching modes, respectively, and assuming A_34./A_3.3~0.68 derived from a small set of aliphatic and aromatic compounds, where A_3.4 and A_3.3 are respectively the band strengths of the 3.4 micrometer aliphatic and 3.3 micrometer aromatic C-H bonds. To improve the estimate of the aliphatic fraction of the UIE carriers, here we analyze 35 UIE sources which exhibit both the 3.3 and 3.4 micrometer C-H features and determine I_3.4/I_3.3, the ratio of the power emitted from the 3.4 micrometer feature to that from the 3.3 micrometer feature. We derive the median ratio to be ~ 0.12. We employ density functional theory and second-order perturbation theory to compute A_3.4/A_3.3 for a range of methyl-substituted PAHs. The resulting A_3.4/A_3.3 ratio well exceeds 1.4, with an average ratio of ~1.76. By attributing the 3.4 micrometer feature exclusively to aliphatic C-H stretch (i.e., neglecting anharmonicity and superhydrogenation), we derive the fraction of C atoms in aliphatic form to be ~2%. We therefore conclude that the UIE emitters are predominantly aromatic.

astro-ph.GA↗

arXiv2013

Cr-K Emission Line as a Constraint on the Progenitor Properties of Supernova Remnants

We perform a survey of the Cr, Mn and Fe-K emission lines in young supernova remnants (SNRs) with the Japanese X-ray astronomy satellite {\sl Suzaku}. The Cr and/or Mn emission lines are detected in 3C\,397 and 0519-69.0 for the first time. We also confirm the detection of these lines in Kepler, W49B, N103B and Cas A. We derive the line parameters (i.e., the line centroid energy, flux and equivalent width [EW]) for these six sources and perform a correlation analysis for the line center energies of Cr, Mn and Fe. Also included in the correlation analysis are Tycho and G344.7-0.1 for which the Cr, Mn and Fe-K line parameters were available in the literature through {\sl Suzaku} observations. We find that the line center energies of Cr correlates very well with that of Fe and that of Mn. This confirms our previous findings that the Cr, Mn and Fe are spatially co-located, share a similar ionization state, and have a common origin in the supernova nucleo-synthesis. We find that the ratio of the EW of the Cr emission line to that of Fe ($\EWR\equiv \EWCr/\EWFe$) provides useful constraints on the SNR progenitors and on the SN explosion mechanisms: for SNRs with $\EWR > 2%$, a type Ia origin is favored (e.g., N103B, G344.7-0.1, 3C\,397 and 0519-69.0); for SNRs with $\EWR < 2%$, they could be of either core-collpase origin or carbon-deflagration Ia origin.

astro-ph.HE↗