Variability of Be Stars in Southern Open Clusters

We recently discovered a large number of highly active Be stars in the open cluster NGC 3766, making it an excellent location to study the formation mechanism of Be star disks. To explore whether similar disk appearances and/or disappearances are common among the Be stars in other open clusters, we present here multiple epochs of H-alpha spectroscopy for 296 stars in eight open clusters. We identify 12 new transient Be stars and confirm 17 additional Be stars with relatively stable disks. By comparing the H-alpha equivalent widths to the photometric y - H-alpha colors, we present a method to estimate the strength of the H-alpha emission when spectroscopy is not available. For a subset of 128 stars in four open clusters, we also use blue optical spectroscopy and available Stromgren photometry to measure their projected rotational velocities, effective temperatures, and polar surface gravities. We combine our Be star detections from these four clusters to investigate physical differences between the transient Be stars, stable Be stars, and normal B-type stars with no line emission. Both types of Be stars are faster rotating populations than normal B-type stars, and we find no significant physical differences between the transient and stable Be stars in our sample.Comment: Accepted to ApJ; small corrections to Table 5 and associated figure

A Self-Propelling Wheel : Prefigured Recurrence in Nietzsche\u27s The Birth of Tragedy

One of Friedrich Nietzsche’s central doctrines, the doctrine of eternal recurrence, asks us to consider how we would feel if we had to repeat our lives exactly as we have lived them. Rather than despair at this possibility, Nietzsche describes the kind of attitude we would adopt if we desired nothing more. He labels such an attitude as “Dionysian”: we rejoice in every pain and every joy that has colored our lives and use them as creative fodder for the future. This identification links the doctrine to Nietzsche’s earlier work on aesthetics, The Birth of Tragedy, where he describes the driving forces behind Greek tragic art, the Apollonian and Dionysian. In this text, Nietzsche also marks a decline in that tragic art through a loss of the Dionysian which signifies a greater decline in Western society. With the absence of the Dionysian, Western thought cannot address the challenges of pessimism which results in a crisis of values. I argue that Nietzsche’s doctrine of eternal recurrence reconciles us with pessimism and thus allows for a creation of new values. Therefore, The Birth of Tragedy describes the conditions that necessitates the doctrine of eternal recurrence, and, in turn, the doctrine addresses the crisis first outlined in The Birth of Tragedy. I further propose that we can re-read the doctrine in light of the aesthetics of The Birth of Tragedy to nuance our understanding of the Dionysian attitude we must adopt in order to overcome the crisis of meaning in our lives

A Stellar Rotation Census of B Stars: from ZAMS to TAMS

Two recent observing campaigns provide us with moderate dispersion spectra of more than 230 cluster and 370 field B stars. Combining them and the spectra of the B stars from our previous investigations ($\sim$430 cluster and $\sim$100 field B stars) yields a large, homogeneous sample for studying the rotational properties of B stars. We derive the projected rotational velocity $V\sin i$, effective temperature, gravity, mass, and critical rotation speed $V_{\rm crit}$ for each star. We find that the average $V\sin i$ is significantly lower among field stars because they are systematically more evolved and spun down than their cluster counterparts. The rotational distribution functions of $V_{\rm eq}/V_{\rm crit}$ for the least evolved B stars show that lower mass B stars are born with a larger proportion of rapid rotators than higher mass B stars. However, the upper limit of $V_{\rm eq}/V_{\rm crit}$ that may separate normal B stars from emission line Be stars (where rotation promotes mass loss into a circumstellar disk) is smaller among the higher mass B stars. We compare the evolutionary trends of rotation (measured according to the polar gravity of the star) with recent models that treat internal mixing. The spin-down rates observed in the high mass subset ($\sim 9 M_\odot$) agree with predictions, but the rates are larger for the low mass group ($\sim 3 M_\odot$). The faster spin down in the low mass B stars matches well with the predictions based on conservation of angular momentum in individual spherical shells. Our results suggest the fastest rotators (that probably correspond to the emission line Be stars) are probably formed by evolutionary spin up (for the more massive stars) and by mass transfer in binaries (for the full range of B star masses).Comment: 44 pages, 10 figures, accepted for publication in Ap

The Ideology of Madness: the Rejected Artist vs. the Capitalist Society in As I Lay Dying

This article examines the character of Darl Bundren in William Faulkner’s As I Lay Dying from the position that he is an artist functioning in a society that ultimately rejects and condemns him through the vessel of ideological conceptions of madness. Topics explored include the ideology of madness, the ideological project of capitalism, queering as a weapon to support an ideology, essential characteristics of “the artist” type, and the consequences of perceived madness

Multiwavelength Observations of the Runaway Binary HD 15137

HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the first XMM-Newton observations of the system. Fits of the EPIC spectra indicate soft, thermal X-ray emission consistent with an isolated O star. Upper limits on the undetected hard X-ray emission place limits on the emission from a proposed compact companion in the system, and we rule out a quiescent neutron star in the propellor regime or a weakly accreting neutron star. An unevolved secondary companion is also not detected in our optical spectra of the binary, and it is difficult to conclude that a gravitational interaction could have ejected this runaway binary with a low mass optical star. HD 15137 may contain an elusive neutron star in the ejector regime or a quiescent black hole with conditions unfavorable for accretion at the time of our observations.Comment: Accepted to A

H-alpha Emission Variability in the gamma-ray Binary LS I +61 303

LS I +61 303 is an exceptionally rare example of a high mass X-ray binary (HMXB) that also exhibits MeV-TeV emission, making it one of only a handful of "gamma-ray binaries". Here we present H-alpha spectra that show strong variability during the 26.5 day orbital period and over decadal time scales. We detect evidence of a spiral density wave in the Be circumstellar disk over part of the orbit. The H-alpha line profile also exhibits a dramatic emission burst shortly before apastron, observed as a redshifted shoulder in the line profile, as the compact source moves almost directly away from the observer. We investigate several possible origins for this red shoulder, including an accretion disk, mass transfer stream, and a compact pulsar wind nebula that forms via a shock between the Be star's wind and the relativistic pulsar wind.Comment: Accepted to Ap

Optical Geolocation for Small Unmanned Aerial Systems

This paper presents an airborne optical geolocation system using four optical targets to provide position and attitude estimation for a sUAS supporting the NASA Acoustic Research Mission (ARM), where the goal is to reduce nuisance airframe noise during approach and landing. A large precision positioned microphone array captures the airframe noise for multiple passes of a Gulfstream III aircraft. For health monitoring of the microphone array, the Acoustic Calibration Vehicle (ACV) sUAS completes daily flights with an onboard speaker emitting tones at frequencies optimized for determining microphone functionality. An accurate position estimate of the ACV relative to the array is needed for microphone health monitoring. To this end, an optical geolocation system using a downward facing camera mounted to the ACV was developed. The 3D positioning of the ACV is computed using the pinhole camera model. A novel optical geolocation algorithm first detects the targets, then a recursive algorithm tightens the localization of the targets. Finally, the position of the sUAS is computed using the image coordinates of the targets, the 3D world coordinates of the targets, and the camera matrix. A Real-Time Kinematic GPS system is used to compare the optical geolocation system

Composition and Distribution of Extracellular Polymeric Substances in Aerobic Flocs and Granular Sludge

Extracellular polymeric substances (EPS) were quantified in flocculent and aerobic granular sludge developed in two sequencing batch reactors with the same shear force but different settling times. Several EPS extraction methods were compared to investigate how different methods affect EPS chemical characterization, and fluorescent stains were used to visualize EPS in intact samples and 20-µm cryosections. Reactor 1 (operated with a 10-min settle) enriched predominantly flocculent sludge with a sludge volume index (SVI) of 120 ± 12 ml g–1, and reactor 2 (2-min settle time) formed compact aerobic granules with an SVI of 50 ± 2 ml g–1. EPS extraction by using a cation-exchange resin showed that proteins were more dominant than polysaccharides in all samples, and the protein content was 50% more in granular EPS than flocculent EPS. NaOH and heat extraction produced a higher protein and polysaccharide content from cell lysis. In situ EPS staining of granules showed that cells and polysaccharides were localized to the outer edge of granules, whereas the center was comprised mostly of proteins. These observations confirm the chemical extraction data and indicate that granule formation and stability are dependent on a noncellular, protein core. The comparison of EPS methods explains how significant cell lysis and contamination by dead biomass leads to different and opposing conclusions