We measured temporal and emission properties of quiescent magnetars using archival Chandra and XMM-Newton data, produced a list of the properties for 17 magnetars, and revisited previously suggested correlations between the properties. Our studies carried out with a larger sample, better spectral characterizations, and more thorough analyses not only confirmed previously-suggested correlations but also found new ones. The observed correlations differ from those seen in other neutron-star populations but generally accord with magnetar models. Specifically, the trends of the intriguing correlations of blackbody luminosity (𝐿BB) with the spin-inferred dipole magnetic field strength (𝐵S) and characteristic age (𝜏c) were measured to be 𝐿BB ∝ 𝐵1.5 S and 𝐿BB ∝ 𝜏−0.6 c , supporting the twisted magnetosphere and magnetothermal evolution models for magnetars. We report the analysis results and discuss our findings in the context of magnetar models.

We report X-ray timing and spectral properties of the pulsar PSR J0205+6449 measured using NuSTAR and Chandra observatories. We measure the pulsar's rotation frequency v = 15:20102357(9) s-1 and its derivative v = -4.5(1) X 10-11 s-2 during the observation period, and model the 2~30 keV on-pulse spectrum of the pulsar with a power law having a photon index Γpsr = 1.07 ± 0.16 and a 2~30 keV flux F2-30 keV = 7.3±0.6 X 10-13 erg cm-2 s-1. The Chandra 0.5-10 keV data are analyzed for an investigation of the pulsar's thermal emission properties. We use thermal and non-thermal emission models to t the Chandra spectra and infer the surface temperature T1 and luminosity Lth of the neutron star to be T∞ = 0.5 - 0.8 MK and Lth = 1 - 5 X 1032 erg s-1. This agrees with previous results which indicated that PSR J0205+6449 has a low surface temperature and luminosity for its age of 800{5600 yrs.

We present IR ux density measurements, models of the broadband SED, and results of SED modeling for the Pulsar Wind Nebula (PWN) 3C 58. We nd that the Herschel ux density seems to be slightly lower than suggested by interpolation of previous measurements in nearby wavebands, implying that there may be multiple electron populations in 3C 58. We model the SED using a simple stationary one-zone and a more realistic time-evolving multi-zone scenario. The latter includes variations of ow properties in the PWN (injected energy, magnetic eld, and bulk speed), radiative energy losses, adiabatic expansion, and diusion, similar to previous PWN models. From the modeling, we nd that a PWN age of 2900{5400 yrs is preferred and that there may be excess emission at  1011 Hz. The latter may imply multiple populations of electrons in the PWN.

We report on the timing properties of the ‘Crab twin’ pulsar PSR B0540−69 measured with X-ray data taken with the Swift telescope over a period of 1100 days. The braking index of the pulsar was estimated to be n = 0.03±0.013 in a previous study performed in 2015 with 500-day Swift data. This small value of n is unusual for pulsars, and a comparison with an old estimate of n ≈ 2.1 for the same target determined ∼10 years earlier suggests a dramatic change in the braking index. To confirm the small value and therefore the large change of n, we used 1100-day Swift observations including the data used in the earlier determination of n = 0.03. In this study we find that the braking index of PSR B0540−69 is n = 0.163 ± 0.001, somewhat larger than 0.03. Since the measured value of n is still much smaller than 2.1, we can confirm the dramatic change in the braking index for this pulsar.

We present analysis results of Korean VLBI Network (KVN) four-band data for the highly variable blazar 3C 279. We measured the 22, 43, 86, and 129 GHz flux densities and spectral indices of the source using contemporaneous data taken over 5.6 years. We used the discrete correlation function to investigate correlations between the radio emission properties and those measured in the optical (2 × 1014 – 1.5 × 1015 Hz), X-ray (0.3–10 keV), and gamma-ray (0.1–300 GeV) bands. We found a significant correlation between the radio spectral index and gamma-ray flux without a time delay and interpreted the correlation using an extended jet scenario for blazar emission.

We report on our Galactic plane searches for magnetars in the archival Chandra X-ray Observatory (CXO) data. We summarize the properties of known magnetars and use them to establish a procedure for magnetar searches. The procedure includes four steps: source finding, spectral characterization, optical counterpart checks, and period searches. We searched 1,282 archival CXO observations, found 32,838 X-ray sources, and selected 25 intriguing candidates using the developed procedure. Although we do not firmly identify a magnetar among them, we significantly reduced the number of targets in future magnetar searches to be done with better X-ray telescopes.