X-ray Bursts from the Accreting Millisecond Pulsar XTE J1814-338

Since the discovery of the accreting millisecond pulsar XTE J1814-338 a total of 27 thermonuclear bursts have been observed from the source with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE). Spectroscopy of the bursts, as well as the presence of continuous burst oscillations, suggests that all but one of the bursts are sub-Eddington. The remaining burst has the largest peak bolometric flux of 2.64 x E^-8 erg/sec/cm^2, as well as a gap in the burst oscillations, similar to that seen in Eddington limited bursts from other sources. Assuming this burst was Eddington limited we obtain a source distance of about 8 kpc. All the bursts show coherent oscillations at the 314.4 Hz spin frequency. The burst oscillations are strongly frequency and phase locked to the persistent pulsations. Only two bursts show evidence for frequency drift in the first few seconds following burst onset. In both cases the initial drift corresponds to a spin down of a few tenths of a Hz. The large oscillation amplitude during the bursts confirms that the burst flux is modulated at the spin frequency. We detect, for the first time, a significant first harmonic component in burst oscillations. The ratio of countrate in the first harmonic to that in the fundamental can be > 0.25 and is, on average, less than that of the persistent pulsations. If the pulsations result from a single bright region on the surface, the harmonic strength suggests the burst emission is beamed, perhaps due to a stronger magnetic field than in non-pulsing LMXBs. Alternatively, the harmonic content could result from a geometry with two bright regions.Comment: AASTeX, 15 pages, 4 figures. Accepted for publication in the Astrophysical Journal Letter

Variable-Frequency QPOs from the Galactic Microquasar GRS 1915+105

We show that the galactic microquasar GRS 1915+105 exhibits quasi-periodic oscillations (QPOs) whose frequency varies continuously from 1-15 Hz, during spectrally hard dips when the source is in a flaring state. We report here analyses of simultaneous energy spectra and power density spectra at 4 s intervals. The energy spectrum is well fit at each time step by an optically thick accretion disk plus power law model, while the power density spectrum consists of a varying red noise component plus the variable frequency QPO. The features of both spectra are strongly correlated with one another. The 1-15 Hz QPOs appear when the power law component becomes hard and intense, and themselves have an energy spectrum consistent with the power law component (with root mean square amplitudes as high as 10%). The frequency of the oscillations, however, is most strikingly correlated with the parameters of the thermal disk component. The tightest correlation is between QPO frequency and the disk X-ray flux. This fact indicates that the properties of the QPO are not determined by solely a disk or solely a corona.Comment: Accepted to ApJ Letters, 12 pages, 3 figures, AASTEX forma

Rossi X-ray Timing Explorer Observations of the X-ray Pulsar EXO 1722-363 - a Candidate Eclipsing Supergiant System

Observations made of the X-ray pulsar EXO 1722-363 using the Proportional Counter Array and All Sky Monitor on board the Rossi X-ray Timing Explorer reveal the orbital period of this system to be 9.741 +/- 0.004 d from periodic changes in the source flux. The detection of eclipses, together with the values of the pulse and orbital periods, suggest that this source consists of a neutron star accreting from the stellar wind of an early spectral type supergiant companion. Pulse timing measurements were also obtained but do not strongly constrain the system parameters. The X-ray spectra can be well fitted with a model consisting of a power law with a high energy cutoff and, for some spectra, a blackbody component with a temperature of approximately 0.85 keV.Comment: Accepted for publication in The Astrophysical Journal. 27 pages including 10 figure

Large Torque Variations in Two Soft Gamma Repeaters

We have monitored the pulse frequencies of the two soft gamma repeaters SGR 1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily Rossi X-ray Timing Explorer Proportional Counter Array observations. In both sources, we observe large changes in the spin-down torque up to a factor of ~4, which persist for several months. Using long baseline phase-connected timing solutions as well as the overall frequency histories, we construct torque noise power spectra for each SGR. The power spectrum of each source is very red (power-law slope ~-3.5). The torque noise power levels are consistent with some accreting systems on time scales of ~1 year, yet the full power spectrum is much steeper in frequency than any known accreting source. To the best of our knowledge, torque noise power spectra with a comparably steep frequency dependence have only been seen in young, glitching radio pulsars (e.g. Vela). The observed changes in spin-down rate do not correlate with burst activity, therefore, the physical mechanisms behind each phenomenon are also likely unrelated. Within the context of the magnetar model, seismic activity cannot account for both the bursts and the long-term torque changes unless the seismically active regions are decoupled from one another.Comment: 26 pages, 11 figures included, accepted for publication in ApJ, analysis of torque noise power density spectra is revised from previous version and minor text changes were mad

The Ursinus Weekly, April 30, 1962

Feldstein, Shinnick and Kelly elected new class presidents • Young Democrats foresee active year under Ryan • Coeds elect reps to WSGA council • ZX & KDK winners in Pi Nu songfest • 2-part art seminar of Y successfully completed • UC mile relayers place 3rd Friday in Penn relays • Haeussner elected president of MSGA • Women voters tap new dorm officers • Y officers reveal new appointments to \u2762-63 cabinet • Myers voted veep of statewide PSEA • IFS weekend features Saylor, Hawkins rock & roll group • Debaters place in New York tourney • Spring blooms to enliven campus • Meistersingers in fine voice finish season on campus • Editorial: Right to review • Letters to the editor • Germany revisited, then to Amsterdam • Carp\u27s Washington of capitol\u27s past • Greek gleanings • Netwomen defeat Penn Varsity, JV\u27s • Lacrossers smash Penn, Swarthmore, deadlock Shipley • Cindercrew downs F&M, sets records in Swarthmore tilt • Siebmen cripple W. Maryland, lose in Hopkins upset • Tennismen suffer • Openings in Africa teaching program • Ursinus coed to enter county beauty pageanthttps://digitalcommons.ursinus.edu/weekly/1318/thumbnail.jp

Discovery of a New Transient Magnetar Candidate: XTE J1810-197

We report the discovery of a new X-ray pulsar, XTE J1810-197. The source was serendipitously discovered on 2003 July 15 by the Rossi X-ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin-period and a soft spectrum (photon index ~ 4). We detect the source in earlier RXTE observations back to 2003 January. These show that a transient outburst began between 2002 November 17 and 2003 January 23 and that the pulsar has been spinning down since then, with a high rate Pdot ~ 10^-11 s/s showing significant timing noise, but no evidence for Doppler shifts due to a binary companion. The rapid spin-down rate and slow spin-period imply a super-critical magnetic field B=3x10^14 G and a young characteristic age < 7600 yr. These properties are strikingly similar to those of anomalous X-ray pulsars and soft gamma repeaters, making the source a likely new magnetar. A follow-up Chandra observation provided a 2".5 radius error circle within which the 1.5 m Russian-Turkish Optical Telescope RTT150 found a limiting magnitude of R_c=21.5, in accord with other recently reported limits. The source is present in archival ASCA and ROSAT data as well, at a level 100 times fainter than the \~ 3 mCrab seen in 2003. This suggests that other X-ray sources that are currently in a state similar to the inactive phase of XTE J1810-197 may also be unidentified magnetars awaiting detection via a similar activity.Comment: Submitted to ApJL; 4 pages; 4 figure

The Discovery of a Neutron Star with a Spin Frequency of 530 Hz in A1744-361

We report the detection with the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) of 530 Hz burst oscillations in a thermonuclear (type I) burst from the transient X-ray source A1744-361. This is only the second burst ever observed from this source, and the first to be seen in any detail. Our results confirm that A1744-361 is a low mass X-ray binary (LMXB) system harboring a rapidly rotating neutron star. The oscillations are first detected along the rising edge of the burst, and they show evidence for frequency evolution of a magnitude similar to that seen in other burst sources. The modulation amplitude and its increase with photon energy are also typical of burst oscillations. The lack of any strong indication of photospheric radius expansion during the burst suggests a 9 kpc upper limit of the source distance. We also find energy dependent dips, establishing A1744-361 as a high inclination, dipping LMXB. The timescale between the two episodes of observed dips suggests an orbital period of ~ 97 minutes. We have also detected a 2 - 4 Hz quasi-periodic-oscillation (QPO) for the first time from this source. This QPO appears consistent with ~ 1 Hz QPOs seen from other high-inclination systems. We searched for kilohertz QPOs, and found a suggestive 2.3 sigma feature at 800 Hz in one observation. The frequency, strength, and quality factor are consistent with that of a lower frequency kilohertz QPO, but the relatively low significance argues for caution, so we consider this a tentative detection requiring confirmation.Comment: 8 pages, 4 figures, published in ApJ Letter

Fostering Fairness: Assessing measurement equivalence of MMIs

Introduction:The selection process for medical schools plays a critical role in identifying candidates who possess the necessary attributes and competencies to excel in the demanding field of medicine. This Multiple Mini Interviews (MMIs) have gained popularity as an assessment tool for evaluating applicants' non-cognitive skills, such as communication, empathy, and ethical judgment. Ensuring the fairness and validity of MMIs across diverse applicant groups is paramount for equitable selection processes. This study aims to investigate the extent to which:•core attributes assessed by MMIs maintain consistent meaning and interpretation across gender groups.•gender-related disparities do exist in MMI performance. •examiner gender influences student MMI performance. Method:This research analyses data collected from 2024 Bond university medical school applicants. A multigroup confirmatory factor analysis (MGCFA) approach will be employed for a comprehensive evaluation of the underlying construct validity of the MMI, assessing its consistency across different subgroups.Results:This study holds promise for shedding light on the extent to which MMIs are comparable and unbiased across different genders. By comparing the performance of female and male students, the analysis provides insights into potential variations in non-cognitive skill assessment between genders. Additionally, the analysis will investigate whether the gender of examiners influences student MMI outcomes, addressing the potential for examiner-related biases. Discussion/ConclusionBy unveiling potential measurement biases and inequities, this research contributes to the refinement of admissions procedures, ultimately fostering a more inclusive and just selection process for aspiring medical professionals. These findings hold implications for both medical education policymakers and practitioners seeking to ensure a more inclusive and equitable selection process for aspiring medical professionals.<br/

Exploring the Influence of Age as a Mediator in Gender Disparities: Personality Traits, Emotional Intelligence, and MMI

This study investigates the mediating role of age in gender differences across personality traits, emotional intelligence, and performance in Multiple Mini Interviews (MMIs), specifically within the context of medical education admissions. Personality traits, emotional intelligence, and MMI outcomes play critical roles in identifying prospective medical students who possess the necessary attributes for success in the medical field. Our dataset comprises approximately 800 individuals who are prospective students at Bond University's medical program for the year 2024. Notably, Bond Medical School embraces both undergraduate and postgraduate applicants to its medicine program, making it an ideal setting for examining these dynamics.The study will primarily analyse scores obtained from the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT), the NEO Big Five Personality Inventory, and MMI evaluations. By employing Multivariate Analysis of Variance (MANOVA) and Multivariate Analysis of Covariance (MANCOVA) techniques, with age as a covariate, we aim to elucidate the nuanced relationships between gender, age, and these critical admission criteria.Data collection is ongoing and anticipated to be complete by mid-March 2024, providing a comprehensive snapshot of the cohort. Our findings hold the potential to offer valuable insights into the intricate interplay of gender, age, and key attributes required for medical education success. Furthermore, understanding the mediating influence of age on gender disparities in these domains could inform more equitable and effective admission practices in medical education.This research contributes to the broader discourse on gender disparities in educational contexts and offers practical implications for optimizing medical admissions processes to foster diversity and inclusivity in the healthcare workforce

RXTE Observations of 1A 1744-361: Correlated Spectral and Timing Behavior

We analyze Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) data of the transient low mass X-ray binary (LMXB) system 1A 1744-361. We explore the X-ray intensity and spectral evolution of the source, perform timing analysis, and find that 1A 1744-361 shows `atoll' behavior during the outbursts. The color-color diagram indicates that this LMXB was observed in a low intensity spectrally hard (low-hard) state and in a high intensity `banana' state. The low-hard state shows a horizontal pattern in the color-color diagram, and the previously reported `dipper QPO' appears only during this state. We also perform energy spectral analyses, and report the first detection of broad iron emission line and iron absorption edge from 1A 1744-361.Comment: 20 pages, 4 tables, 4 figures, accepted for publication in Ap