Crystal structure, magnetism and magnetocaloric properties of Mn\u3csub\u3e2−x\u3c/sub\u3eSn\u3csub\u3e0.5\u3c/sub\u3eGa\u3csub\u3e0.5\u3c/sub\u3e (x=0, 0.3, 0.5, 0.8) alloys

Magnetic refrigeration based on the magnetocaloric effect has attracted recent attention due to advantages such as high efficiency and environmental friendliness. We have investigated the structural, magnetic and magnetocaloric properties of Mn2−xSn0.5Ga0.5 (x=0, 0.3, 0.5, 0.8) alloys prepared using arc-melting and meltspinning techniques with prospects for magnetic refrigeration. The Mn2−xSn0.5Ga0.5 alloys, except for Mn1.2Sn0.5Ga0.5, have a single-phase hexagonal crystal structure. The Mn1.2Sn0.5Ga0.5 alloy also contains a small amount of MnSn2 impurity phase. The Curie temperature and high-field (30 kOe) magnetization at 55 K decrease with increasing Mn concentration from 306 K and 64.1 emu/g (1.07 μB/Mn) for Mn1.2Sn0.5Ga0.5 to 262 K and 46.7 emu/g (0.85 μB/Mn) for Mn2Sn0.5Ga0.5, respectively. The peak values of magnetic entropy change are relatively small with ΔSM,max=1.7 Jkg−1K−1for Mn1.5Sn0.5Ga0.5 at 30 kOe. Despite this, these materials show considerable relative cooling power (RCP) along with a wide working temperature range near room temperature and negligible magnetic and thermal hysteresis, where Mn1.2Sn0.5Ga0.5 shows a highest RCP of 102.3 Jkg−1 at 30 kOe

Large Area X-ray Proportional Counter (LAXPC) in Orbit Performance : Calibration, background, analysis software

The Large Area X-ray Proportional Counter (LAXPC) instrument on-board AstroSat has three nominally identical detectors for timing and spectral studies in the energy range of 3--80 keV. The performance of these detectors during the five years after the launch of AstroSat is described. Currently, only one of the detector is working nominally. The variation in pressure, energy resolution, gain and background with time are discussed. The capabilities and limitations of the instrument are described. A brief account of available analysis software is also provided.Comment: Accepted for publication in JA

The curious activity in the nucleus of NGC 4151: jet interaction causing variability?

A key characteristic of many active galactic nuclei (AGNs) is their variability, but its origin is poorly understood, especially in the radio domain. Williams et al. (2017) reported a ∼50 per cent increase in peak flux density of the AGN in the Seyfert galaxy NGC 4151 at 1.5 GHz with the e-MERLIN array. We present new high-resolution e-MERLIN observations at 5 GHz and compare these to archival MERLIN observations to investigate the reported variability. Our new observations allow us to probe the nuclear region at a factor three times higher resolution than the previous e-MERLIN study. We separate the core component, C4, into three separate components: C4W, C4E, and X. The AGN is thought to reside in component C4W, but this component has remained constant between epochs within uncertainties. However, we find that the Eastern-most component, C4E, has increased in peak flux density from 19.35 ± 1.10 to 37.09 ± 1.86 mJy beam−1, representing an 8.2σ increase on the MERLIN observations. We attribute this peak flux density increase to continue interaction between the jet and the emission line region (ELR), observed for the first time in a low-luminosity AGNs such as NGC 4151. We identify discrete resolved components at 5 GHz along the jet axis, which we interpret as areas of jet–ELR interaction

LeMMINGs III. The e-MERLIN legacy survey of the Palomar sample: exploring the origin of nuclear radio emission in active and inactive galaxies through the [O iii] – radio connection

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O III] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H II and absorption line galaxies (ALGs)] galaxies. Using [O III] luminosity (⁠L[OIII]⁠) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O III] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H II galaxies dominate with Lcore∝M0.61±0.33BH and Lcore∝L0.79±0.30[OIII]⁠. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with Lcore∝M1.5−1.65BH and Lcore∝L0.99−1.31[OIII] for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H II galaxies always display (although low) signatures of radio-emitting BH activity, with L1.5GHz≳1019.8 W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates (⁠m˙⁠). Radio-quiet and radio-loud LINERs are powered by low-m˙ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-m˙ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H II galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local active galaxies