X-ray and Radio Studies of the candidate Millisecond Pulsar Binary 4FGL J0935.3+0901

4FGL J0935.5+0901, a γ-ray source recently identified as a candidate redback-type millisecond pulsar binary (MSP), shows an interesting feature of having double-peaked emission lines in its optical spectrum. The feature would further suggest the source as a transitional MSP system in the sub-luminous disk state. We have observed the source with XMM-Newton and Five-hundred-meter Aperture Spherical radio Telescope (FAST) at X-ray and radio frequencies respectively for further studies. From the X-ray observation, a bimodal count-rate distribution, which is a distinctive feature of the transitional MSP systems, is not detected, while the properties of X-ray variability and power-law spectrum are determined for the source. These results help establish the consistency of it being a redback in the radio pulsar state. However no radio pulsation signals are found in the FAST observation, resulting an upper limit on the flux density of ∼ 4 µJy. Implications of these results are discussed.

Introduction

This introduction delineates the three main pillars of the book. Red music is defined within the context of the Vietnamese music industry and compared with propaganda music in other communist countries. The concept of a continuous revolution is described through reference to literature from political thinkers in Vietnam and the wider communist world. Radio and the voice are assessed as key themes in recent anthropological studies. This is followed by a review of the social history of sound reproduction, which is considered in the fields of ethnomusicology, sound studies, radio studies, and related fields. After outlining the research methodology (ethnographic and archival approaches) and structure of the book, the introduction concludes with notes on language, recordings, and musical transcriptions.

Characterising Radio Emissions in Cosmic Filaments

<p>A growing number of radio studies probe galaxy clusters into the low-power regime in which star formation is the dominant source of radio emission. However, at the time of writing no comparably deep observations have focused exclusively on the radio populations of cosmic filaments. This thesis describes the ATCA 2.1 GHz observations and subsequent analysis of two such regions - labelled Zone 1 (between clusters A3158 and A3125/A3128) and Zone 2 (between A3135 and A3145) - in the Horologium-Reticulum Supercluster (HRS). Source count profiles of both populations are discussed and a radio luminosity function for Zone 1 is generated. While the source counts of Zone 2 appear to be consistent with expected values, Zone 1 exhibits an excess of counts across a wide flux range (1 mJy</p>

Characterising Radio Emissions in Cosmic Filaments

<p>A growing number of radio studies probe galaxy clusters into the low-power regime in which star formation is the dominant source of radio emission. However, at the time of writing no comparably deep observations have focused exclusively on the radio populations of cosmic filaments. This thesis describes the ATCA 2.1 GHz observations and subsequent analysis of two such regions - labelled Zone 1 (between clusters A3158 and A3125/A3128) and Zone 2 (between A3135 and A3145) - in the Horologium-Reticulum Supercluster (HRS). Source count profiles of both populations are discussed and a radio luminosity function for Zone 1 is generated. While the source counts of Zone 2 appear to be consistent with expected values, Zone 1 exhibits an excess of counts across a wide flux range (1 mJy</p>

Sounds like ‘home’: The synchrony and dissonance of podcasting as boundary object

Working at the intersection of migration studies and radio studies, we interrogate podcasting’s potential as a practice-based activist research method. This article documents podcasting’s role in an ethnographic project conducted together with Konstkupan (The Art Hive), a migrant-focused community arts space in Malmö, Sweden. We argue that the value of podcasting as a practice-based research method exists in its potential to function as a boundary object. Boundary objects are technologies and processes bridging social worlds and providing sites of communication and translation between groups. Challenging narratives that detect a decline in podcasting’s radical potential, we argue that as a boundary object, podcasting’s political significance continues in how it convenes small, diverse, but attentive ‘listening publics’. A boundary object does not demand consensus on the meanings or representations it produces, affording space for both the synchrony and dissonance of narratives produced by migrants.

Radio studies beyond broadcasting: Towards an intermedia and inter-technological radio history

Examining radio development over a long time span from the late nineteenth to the early twenty-first century, in this article, we claim that radio history is broader than the history of broadcasting only. We suggest looking at radio history through the perspective of intermediality and inter-technology, drawing on five different examples: radiography, radiotelegraphy/radiotelephony, radar and satellites, radiomobile/mobile phones with regard to radio spectrum and packet radio networks, such as Wi-Fi. We demonstrate how and why these (and other) technologies should be considered parts of radio studies even though they do not represent classic examples of radio broadcasting. Overall, this intermedia and inter-technological perspective on radio history offers new ways of rethinking and reformulating the confines of radio studies, as well as contributes to a greater field of media studies.

Irradiation Investigation: Exploring the Molecular Gas in NGC 7293

Background: Many planetary nebulae retain significant quantities of molecular gas and dust despite their signature hostile radiation environments and energetic shocks. Photoionization and dissociation by extreme UV and (often) X-ray emission from their central stars drive the chemical processing of this material. Their well-defined geometries make planetary nebulae ideal testbeds for modeling the effects of radiation-driven heating and chemistry on molecular gas in photodissociation regions. Methods: We have carried out IRAM 30m/APEX 12m/ALMA radio studies of the Helix Nebula and its molecule-rich globules, exploiting the unique properties of the Helix to follow up our discovery of an anti-correlation between HNC/HCN line intensity ratio and central star UV Luminosity. Results: Analysis of HNC/HCN across the Helix Nebula reveals the line ratio increases with distance from the central star, and thus decreasing incident UV flux, indicative of the utility of the HNC/HCN ratio as a tracer of UV irradiation in photodissociation environments. However, modeling of the observed regions suggests HNC/HCN should decrease with greater distance, contrary to the observed trend. Conclusion: HNC/HCN acts as an effective tracer of UV irradiation of cold molecular gas. Further model studies are required.

X-ray and radio studies of SNR CTB 37B hosting the magnetar CXOU J171405.7−381031

ABSTRACT We present a Chandra and XMM–Newton study of the supernova remnant (SNR) CTB 37B, along with archival radio observations. In radio wavelengths, the SNR CTB 37B is an incomplete shell showing bright emission from the eastern side, while the X-ray morphology shows diffuse emission from regions surrounding the magnetar CXOU J171405.7–381031. We used archival H i absorption measurements to constrain the distance to the remnant and obtain D = 9.8 ± 1.5 kpc. The X-ray spectrum of the remnant is described by a thermal model in the 1–5 keV energy range, with a temperature of kT = 1.3 ± 0.1 keV. The abundances from the spectral fits are consistent with being solar or sub-solar. A small region of diffuse emission is seen to the southern side of the remnant, best fitted by a non-thermal spectrum with an unusually hard photon index of Γ = 1.3 ± 0.3. Assuming a distance of 9.8 kpc to the SNR, we infer a shock velocity of Vs = 915 ± 70 km s−1 and an explosion energy of E = (1.8 ± 0.6) × 1050 erg. The overall imaging and spectral properties of CTB 37B favour the interpretation of a young SNR (≲6200 yr old), propagating in a low-density medium under the assumption of a Sedov evolutionary phase.