arXiv subjects

J. Chapman

Publications and source records attributed to J. Chapman.

17 recordsLinked to original sources

arXiv2025

Challenging historical novae: AT Cnc (1645), Te-11 (483), and M22 (BC 48) revisited

Connections between novae with shells and historical observations are crucial for astrophysical understanding of long-term evolution of shells and cataclysmic variables. Three of five previously considered links are revisited here: extended features in M22 in BC48, Te-11 in 483, and AT Cnc in 1645. We aim to develop a procedure to check whether these links are credible. Literal translations of the Chinese texts, historically based arguments, and close readings are combined with astrophysics, (peak brightness, decay time estimate, shell age expansion model calculation, etc.). (a) Nandou's second star, near which the BC48 `guest star' was reported, is identified as tau Sgr, not lambda Sgr, far from the M22 location. A nova in M22 would peak at only m=6.4 \pm 1.4 mag, and thus a description as a `blue-white' `melon' does not fit; it was likely a comet. (b) The imprecise position (`Shen['s] east') of the `guest star' in 483, its extended (dipper-like) radiance, and the context speak for a bolide. Considering the new (larger) Gaia distance and small extinction towards Te-11 (outside a cloud), its bi-polar morphology and current expansion velocity point to a planetary nebula; as a nova, the shell expansion age is 1100-2000 yr from detailed supersonic expansion calculations. (c) Most certainly, Mars was meant when the source for 1645 reported `a large star entered Yugui'; the verb implies motion. AT Cnc lies neither in Yugui's asterism box nor in the eponymous lunar mansion range. The fluid drag expansion age of AT Cancri's ejecta is 128-631 yr. All three exact ages are unsubstantiated. True novae or nova shells can be connected to historical records only if the position and object type are plausible. Duration, brightness (light curve), and color (evolution) should fit and could provide more astrophysical insight ...

astro-ph.SR↗

arXiv2024

The Mira discovery problem -- Observations by David Fabricius in 1596 and 1609 (and by others before?): Positional accuracy, brightness, color index, and period

The pulsating variable star Mira (omikron Ceti) was observed by David Fabricius (Frisia) in 1596 and 1609. We review suggested previous detections (e.g. China, Hipparchos). We analyze all Mira records from Fabricius in their historical context. Fabricius measured the separation of Mira to other stars to \pm 1.6-1.7'. From his texts, we derive a brightness (slightly brighter than Hamal) of ca. 1.9 \pm 0.1 mag and a color index B-V \simeq 1.3-1.4 mag (`like Mars') for 1596 Aug 3 (jul.). Mira started to fainten 19 days later and was observed until mid/late Oct. We show why such a red star cannot be followed by the naked eye until ca. 6 mag: For Mira's color at disappearance and altitude from Frisia, the limit is reduced by ca. 1.0 mag. Since Fabricius connected the Mira brightening with the close-by prograde Jupiter, he re-detected it only 12 years later, probably shortly before a relatively bright maximum - discoveries are strongly affected by biases. A Mira period of 330.2 days is consistent with both the oldest data (from Fabricius 1596 to Hevelius 1660) and the most current data (VSX 2004-2023), so that we see no evidence for secular period or phase shifts. (We also present Fabricius' observations of P Cygni in 1602.)

astro-ph.SR↗

arXiv2023

The New Small Wheel electronics

The increase in luminosity, and consequent higher backgrounds, of the LHC upgrades require improved rejection of fake tracks in the forward region of the ATLAS Muon Spectrometer. The New Small Wheel upgrade of the Muon Spectrometer aims to reduce the large background of fake triggers from track segments that are not originated from the interaction point. The New Small Wheel employs two detector technologies, the resistive strip Micromegas detectors and the "small" Thin Gap Chambers, with a total of 2.45 Million electrodes to be sensed. The two technologies require the design of a complex electronics system given that it consists of two different detector technologies and is required to provide both precision readout and a fast trigger. It will operate in a high background radiation region up to about 20 kHz/cm$^{2}$ at the expected HL-LHC luminosity of $\mathcal{L}$=7.5$\times10^{34}$cm$^{-2}$s$^{-1}$. The architecture of the system is strongly defined by the GBTx data aggregation ASIC, the newly-introduced FELIX data router and the software based data handler of the ATLAS detector. The electronics complex of this new detector was designed and developed in the last ten years and consists of multiple radiation tolerant Application Specific Integrated Circuits, multiple front-end boards, dense boards with FPGA's and purpose-built Trigger Processor boards within the ATCA standard. The New Small Wheel has been installed in 2021 and is undergoing integration within ATLAS for LHC Run 3. It should operate through the end of Run 4 (December 2032). In this manuscript, the overall design of the New Small Wheel electronics is presented.

hep-ex↗

arXiv2021

Orbit determination just from historical observations? Test case: The comet of AD 760 is identified as 1P/Halley

Recent advances in techniques of critical close reading of historical texts can now be applied to records of pre-telescopic celestial observations - allowing significant progress for analyzing and solving orbits of past comets: we exemplify our method by solving the orbit of the comet in AD 760 only with historical observations and then identify it with 1P/Halley. A detailed eyewitness record with drawing of a comet in AD 760 in the Syriac Chronicle of Zuqnin (finished AD 775/6) was not yet included in the study of its orbit - the Chinese reports alone do not yield a sufficient number of dated positions. We analyze the Syriac and Chinese sources with critical methods for quantitative astronomical usage, we also consider a few further records from the Mediterranean and West Asian area. With our conservatively derived dated positions we can determine the best fitting Keplerian orbital solution by least squares fitting yielding the orbital elements; the parameter ranges for non-periodic solutions and highly eccentric periodic solutions are consistent with each other. The allowed parameter ranges for perihelion distance and inclination are sufficiently small to identify the comet with 1P/Halley. Although 1P/Halley is the only comet, where the telescopic orbit is credibly linked to pre-telescopic returns, e.g. to AD 760, our identification confirms claims from extrapolating telescopic observations backward in time - here independently based on historical data. In particular, we obtained a precise perihelion time (760 May 19.1 \pm 1.7). The inferior conjunction between comet and Sun as on the previously published orbit (760 May 31.9) is shifted by about one day compared to our new orbit (June 1.8), only the new one is consistent with the last observation (June 1.0) before conjunction as reported in the Chronicle of Zuqnin. We also study the comet's brightness evolution ...

astro-ph.EP↗

arXiv2017

New sunspots and aurorae in the historical Chinese text corpus? Comments on uncritical digital search applications

We review some applications of the method of electronic searching for historical observations of sunspots and aurorae in the Chinese text corpus by Hayakawa et al. etc. However, we show strong shortcomings in the digital search technique as applied by them: almost all likely true sunspot and aurora records were presented before (e.g. Xu et al. 2000), which is not mentioned in those papers; the remaining records are dubious and often refer to other phenomena, neither spots nor aurorae (this also applies to Hayakawa et al. 2017c). Most of the above publications include very few Chinese texts and translations, and their tables with abbreviated keywords do not allow the reader to consider alternative interpretations (the tables also do not specify which records mention night-time). We have compared some of their event tables with previously published catalogs and found various discrepancies. There are also intrinsic inconsistencies, misleading information (lunar phase for day-time events), and dating errors. We present Chinese texts and translations for some of their presumable new aurorae: only one can be considered a likely true aurora (AD 604 Jan); some others were selected on the sole basis of the use of the word "light" or "rainbow". Several alleged new aurorae present observations beside the Sun during day-time. There are well-known comets among their presumable aurorae. We also discuss, (i) whether "heiqi ri pang" can stand for black spot(s) "on one side of" or "beside" the sun, (ii) aurora color confusion in Hayakawa et al. (2015, 2016), and (iii) whether "white" and "unusual rainbows" can be aurorae.

astro-ph.SR↗

arXiv2015

A pilot ASKAP survey of radio transient events in the region around the intermittent pulsar PSR J1107-5907

We use observations from the Boolardy Engineering Test Array (BETA) of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope to search for transient radio sources in the field around the intermittent pulsar PSR J1107-5907. The pulsar is thought to switch between an "off" state in which no emission is detectable, a weak state and a strong state. We ran three independent transient detection pipelines on two-minute snapshot images from a 13 hour BETA observation in order to 1) study the emission from the pulsar, 2) search for other transient emission from elsewhere in the image and 3) to compare the results from the different transient detection pipelines. The pulsar was easily detected as a transient source and, over the course of the observations, it switched into the strong state three times giving a typical timescale between the strong emission states of 3.7 hours. After the first switch it remained in the strong state for almost 40 minutes. The other strong states lasted less than 4 minutes. The second state change was confirmed using observations with the Parkes radio telescope. No other transient events were found and we place constraints on the surface density of such events on these timescales. The high sensitivity Parkes observations enabled us to detect individual bright pulses during the weak state and to study the strong state over a wide observing band. We conclude by showing that future transient surveys with ASKAP will have the potential to probe the intermittent pulsar population.

astro-ph.SR↗

arXiv2015

Superconductivity in Ca-doped graphene

Graphene, a zero-gap semimetal, can be transformed into a metallic, semiconducting or insulating state by either physical or chemical modification. Superconductivity is conspicuously missing among these states despite considerable experimental efforts as well as many theoretical proposals. Here, we report superconductivity in calcium-decorated graphene achieved by intercalation of graphene laminates that consist of well separated and electronically decoupled graphene crystals. In contrast to intercalated graphite, we find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among intercalants used in our experiments such as potassium, caesium and lithium. Ca-decorated graphene becomes superconducting at ~ 6 K and the transition temperature is found to be strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration. In addition to the first evidence for superconducting graphene, our work shows a possibility of inducing and studying superconductivity in other 2D materials using their laminates.

cond-mat.supr-con↗

arXiv2015

Discovery of HI gas in a young radio galaxy at $z = 0.44$ using the Australian Square Kilometre Array Pathfinder

We report the discovery of a new 21-cm HI absorption system using commissioning data from the Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder (ASKAP). Using the 711.5 - 1015.5 MHz band of ASKAP we were able to conduct a blind search for the 21-cm line in a continuous redshift range between $z = 0.4$ and 1.0, which has, until now, remained largely unexplored. The absorption line is detected at $z = 0.44$ towards the GHz-peaked spectrum radio source PKS B1740$-$517 and demonstrates ASKAP's excellent capability for performing a future wide-field survey for HI absorption at these redshifts. Optical spectroscopy and imaging using the Gemini-South telescope indicates that the HI gas is intrinsic to the host galaxy of the radio source. The narrow OIII emission lines show clear double-peaked structure, indicating either large-scale outflow or rotation of the ionized gas. Archival data from the \emph{XMM-Newton} satellite exhibit an absorbed X-ray spectrum that is consistent with a high column density obscuring medium around the active galactic nucleus. The HI absorption profile is complex, with four distinct components ranging in width from 5 to 300 km s$^{-1}$ and fractional depths from 0.2 to 20 per cent. In addition to systemic HI gas, in a circumnuclear disc or ring structure aligned with the radio jet, we find evidence for a possible broad outflow of neutral gas moving at a radial velocity of $v \sim 300$ km s$^{-1}$. We infer that the expanding young radio source ($t_{\rm age} \approx 2500$ yr) is cocooned within a dense medium and may be driving circumnuclear neutral gas in an outflow of $\sim$ 1 $\mathrm{M}_{\odot}$ yr$^{-1}$.

astro-ph.GA↗

arXiv2015

ASKAP HI imaging of the galaxy group IC 1459

We present HI imaging of the galaxy group IC 1459 carried out with six antennas of the Australian SKA Pathfinder equipped with phased-array feeds. We detect and resolve HI in eleven galaxies down to a column density of $\sim10^{20}$ cm$^{-2}$ inside a ~6 deg$^2$ field and with a resolution of ~1 arcmin on the sky and ~8 km/s in velocity. We present HI images, velocity fields and integrated spectra of all detections, and highlight the discovery of three HI clouds -- two in the proximity of the galaxy IC 5270 and one close to NGC 7418. Each cloud has an HI mass of $10^9$ M$_\odot$ and accounts for ~15% of the HI associated with its host galaxy. Available images at ultraviolet, optical and infrared wavelengths do not reveal any clear stellar counterpart of any of the clouds, suggesting that they are not gas-rich dwarf neighbours of IC 5270 and NGC 7418. Using Parkes data we find evidence of additional extended, low-column-density HI emission around IC 5270, indicating that the clouds are the tip of the iceberg of a larger system of gas surrounding this galaxy. This result adds to the body of evidence on the presence of intra-group gas within the IC 1459 group. Altogether, the HI found outside galaxies in this group amounts to several times $10^9$ M$_\odot$, at least 10% of the HI contained inside galaxies. This suggests a substantial flow of gas in and out of galaxies during the several billion years of the group's evolution.

astro-ph.GA↗

arXiv2014

The Australian Square Kilometre Array Pathfinder: System Architecture and Specifications of the Boolardy Engineering Test Array

This paper describes the system architecture of a newly constructed radio telescope - the Boolardy Engineering Test Array, which is a prototype of the Australian Square Kilometre Array Pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a 6-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least 9 dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.

astro-ph.IM↗

arXiv2014

Long paths in the distance graph over large subsets of vector spaces over finite fields

Let $E \subset {\Bbb F}_q^d$, the $d$-dimensional vector space over a finite field with $q$ elements. Construct a graph, called the distance graph of $E$, by letting the vertices be the elements of $E$ and connect a pair of vertices corresponding to vectors $x,y \in E$ by an edge if $||x-y||={(x_1-y_1)}^2+\dots+{(x_d-y_d)}^2=1$. We shall prove that if the size of $E$ is sufficiently large, then the distance graph of $E$ contains long non-overlapping paths and vertices of high degree.

math.CO↗

arXiv2014

Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 8: Instrumentation Frontier

These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 8, on the Instrumentation Frontier, discusses the instrumentation needs of future experiments in the Energy, Intensity, and Cosmic Frontiers, promising new technologies for particle physics research, and issues of gathering resources for long-term research in this area.

hep-ex↗

arXiv2009

Status of the LUX Dark Matter Search

The Large Underground Xenon (LUX) dark matter search experiment is currently being deployed at the Homestake Laboratory in South Dakota. We will highlight the main elements of design which make the experiment a very strong competitor in the field of direct detection, as well as an easily scalable concept. We will also present its potential reach for supersymmetric dark matter detection, within various timeframes ranging from 1 year to 5 years or more.

astro-ph.CO↗

arXiv2009

The PULSE@Parkes project: A new observing technique for long-term pulsar monitoring

The PULSE@Parkes project has been designed to monitor the rotation of radio pulsars over time spans of days to years. The observations are obtained using the Parkes 64-m and 12-m radio telescopes by Australian and international high school students. These students learn the basis of radio astronomy and undertake small projects with their observations. The data are fully calibrated and obtained with the state-of-the-art pulsar hardware available at Parkes. The final data sets are archived and are currently being used to carry out studies of 1) pulsar glitches, 2) timing noise, 3) pulse profile stability over long time scales and 4) the extreme nulling phenomenon. The data are also included in other projects such as gamma-ray observatory support and for the Parkes Pulsar Timing Array project. In this paper we describe the current status of the project and present the first scientific results from the Parkes 12-m radio telescope. We emphasise that this project offers a straightforward means to enthuse high school students and the general public about radio astronomy while obtaining scientifically valuable data sets.

astro-ph.SR↗

arXiv2005

Search for First-Generation Scalar Leptoquarks in $\bm{p \bar{p}}$ collisions at $\sqrt{s}$=1.96 TeV

We report on a search for pair production of first-generation scalar leptoquarks ($LQ$) in $p \bar{p}$ collisions at $\sqrt{s}$=1.96 TeV using an integrated luminosity of 203 $pb^{-1}$ collected at the Fermilab Tevatron collider by the CDF experiment. We observe no evidence for $LQ$ production in the topologies arising from $LQ \bar{LQ} \to eqeq$ and $LQ \bar{LQ} \to eq νq$, and derive 95% C.L. upper limits on the $LQ$ production cross section. %as a function of $β$, where $β$ is the branching fraction for $LQ \to eq$. The results are combined with those obtained from a separately reported CDF search in the topology arising from $LQ\bar{LQ} \to νq νq$ and 95% C.L. lower limits on the LQ mass as a function of $β= BR(LQ \to eq) $ are derived. The limits are 236, 205 and 145 GeV/c$^2$ for $β$ = 1, $β$ = 0.5 and $β$ = 0.1, respectively.

hep-ex↗

arXiv2004

Comparison of Three-jet Events in Proton-Antiproton Collisions at Center-of-mass Energy 1.8 TeV to Predictions from a Next-to-leading Order QCD Calculation

The properties of three-jet events with total transverse energy greater than 320 GeV and individual jet energy greater than 20 GeV have been analyzed and compared to absolute predictions from a next-to-leading order (NLO) perturbative QCD calculation. These data, of integrated luminosity 86 pb^-1, were recorded by the CDF Experiment for proton-antiproton collisions at sqrt{s}=1.8 TeV. This study tests a model of higher order QCD processes that result in gluon emission and can be used to estimate the magnitude of the contribution of processes higher than NLO. The total cross section is measured to be 466 +/- 3(stat.)^{+207}_{-70}(syst.) pb. The differential cross section is furthermore measured for all kinematically accessible regions of the Dalitz plane, including those for which the theoretical prediction is unreliable. While the measured cross section is consistent with the theoretical prediction in magnitude, the two differ somewhat in shape in the Dalitz plane.

hep-ex↗

arXiv2000

The ATCA/VLA OH 1612 MHz survey. III. Northern Galactic Plane

We present observations of the region between 5deg < l < 45deg and |b| < 3deg, in the OH 1612 MHz line, taken from 1993 to 1995 with the VLA. These observations are the last part of a larger survey, covering |l| < 45deg and |b| < 3deg, with the ATCA and the VLA. The region was systematically observed on a 30'x30' grid in (l,b) and the resulting coverage was 92%, with 965 pointings. We found 286 OH--masing objects, 161 of which are new detections and 207 have reliable IRAS point-source identifications. The outflow velocity was determined for 276 sources. A total of 766 sources were detected in the combined ATCA/VLA survey, of which 29 were detected in two regions of the survey. The source tables and spectra may be downloaded from http://msowww.anu.edu.au/~msevenst/pubs.html In this article we analyse the data statistically and give identifications with known sources where possible. The efficiency of this VLA survey is 75% of that of the ATCA Bulge survey. This efficiency was determined by comparing the detections in the region where the two surveys overlap. The completeness- and error characteristics are similar, though less homogeneous, except for the much larger errors in the flux densities. The relatively large surface number density found in the northern disk, suggests that we can see the Bar extending to higher longitudes on this side of the galactic Centre.

astro-ph↗