Photometry and the light curve of the optical counterpart of the eclipsing millisecond pulsar 1957+20

We confirm the discovery of the optical counterpart to the eclipsing millisecond pulsar 1957 + 20 recently reported by Fruchter, Stinebring, and Taylor and identified earlier by Kulkarni et al. and Fruchter and colleagues. A nearly complete light curve derived from 58 CCD images taken in the Gunn r band has been obtained and found to match the 9.17 hr orbital period of the pulsar. As expected, minimum and maximum light correspond to orbital phases 0.25 and 0.75, respectively. The amplitude of the variation is 0.85 mag with apparent magnitudes of Gunn-Thuan r = 19.36, or V ≃ 19.7, and colors (g - r) = 0.66, or (B -V) ≃ 1.2, at maximum light, and uncorrected for interstellar extinction. However, the centroid of the previously proposed optical counterpart displays a 9.17 hr periodic wobble with amplitude of ~0.”5, indicating the presence of a field star separated by ≃ 1". Assuming that minimum light is due entirely to the field star, the pulsar companion would have peak apparent magnitudes of r = 20.05, or V ≃ 20.3, and colors (g - r) = 0.45, or (B - V) ≃ 1.0, again not including extinction. If the extinction is assumed to be = 1 mag, the corrected color is found to be (g - r) = 0.11, or (B - V) ≃ 0.7, which corresponds to an effective temperature of 5800 K. Based on modeling the heating of and reradiation from the companion, we obtain a synthetic light curve that matches the observed sharp rise to maximum light and flat, broad minimum. By matching the model to the observed brightness and color of the counterpart it is possible to rule out a high extinction (A_V ≃ 3 mag) to the source due to the high luminosity required. For A_V between 1 and 2 mag the inferred stellar radius lies between 0.07 R⊙ and 0.2 R⊙, depending on distance. Assuming the distance 0.9 kpc derived from the radio dispersion measure, and an extinction of A_V = 1 mag, we derive an absolute visual magnitude of the pulsar companion of 10.5 and its radius to be ≃ 0.16 R_⊙, close to that of a degenerate hydrogen dwarf

Cobalt removal from wastewater using pine sawdust

Agricultural wastes can cause environmental problems if not well managed, but there is a lot of potential to use these wastes as raw material in other processes. In this investigation, pine sawdust was evaluated as an adsorbent in the treatment of wastewater containing cobalt ions. A two-level three-factor full-factorial experimental design with centre points was used to study the interactive effect of the operating parameters in order to achieve the best conditions for the batch adsorption of cobalt ions. A response surface analysis was also conducted to further understand the interactions amongst the factors such as adsorbent dose, solution pH and initial concentration. In addition, adsorption isotherms, namely the Freundlich and Langmuir, were used to characterize the removal of cobalt from the wastewater. It was observed that the combined effect of low adsorbent dose, high pH and high initial concentration of wastewater resulted in the highest adsorption capacity. The Freundlich isotherm provided a better fit to the experimental data than the Langmuir isotherm. Moreover, pine sawdust showed adsorption capabilities for cobalt, and hence it could be an option in the quest to use waste to treat wastewater

The Relationship of Organizational Justice and Interpersonal Attraction in Survivors’ Acceptance of Co-Worker Terminations

The main purpose of this study was to examine the relationship of organizational justice and interpersonal attraction in survivors’ acceptance of co-worker terminations. Four scenarios were tested manipulating high and low levels of the two independent variables (organizational justice and interpersonal attraction) and their effects on the dependent variable (level of acceptance of coworker terminations). Findings indicate justice during the termination process is more important than how much the coworker was liked on the survivors’ acceptance of coworker terminations. The practical implication is that organizations must be careful to insure that terminations are done in a just manner in order to engender the acceptance of the surviving workforce

Affective organizational commitment and organizational citizenship behavior: examining the relationship through the lens of equity sensitivity

The main purpose of this study was to test the relationship between affective organizational commitment (AOC), organizational citizenship behavior (OCB), and equity sensitivity, which heretofore has not been examined. Results revealed an interaction between AOC and equity sensitivity such that persons with an entitled orientation exhibited higher levels of OCB as their degree of AOC increased. Individuals with an entitled orientation and lower levels of AOC exhibited the lowest levels of OCB. This research suggests that organizations should focus on improving the level of AOC in order to increase the citizenship behavior of their entitled members. The moderating effect of equity sensitivity may help to explain why the relationship between AOC and OCB has been characterized as modest or weak in previous research studies

Relativistic Corrections in White Dwarf Asteroseismology

With the precision now afforded by modern space-based photometric observations from the retired K2 and current TESS missions, the effects of general relativity (GR) may be detectable in the light curves of pulsating white dwarfs (WDs). Almost all WD models are calculated using a Newtonian description of gravity and hydrodynamics. To determine if inclusion of GR leads to observable effects, we used idealized models of compact stars and made side-by-side comparison of mode periods computed using a (i) Newtonian and (ii) GR description of the equilibrium structure and nonradial pulsations. For application to white dwarfs, it is only necessary to include the first post-Newtonian (1PN) approximation to GR. The mathematical nature of the linear nonradial pulsation problem is then qualitatively unchanged and the GR corrections can be written as extensions of the classic Dziembowski equations. As such, GR effects might easily be included in existing asteroseismology codes. The idealized stellar models are (i) \pn1 relativistic polytropes and (ii) stars with cold degenerate-electron equation of state featuring a near-surface chemical transition from $\mu_e = 2$ to $\mu_e = 1$, simulating a surface hydrogen layer. Comparison of Newtonian and 1PN normal mode periods reveals fractional differences on the order of the surface gravitational redshift $z$. For a typical WD, this fractional difference is $\sim 10^{-4}$ and is greater than the period uncertainty $\sigma_{\Pi}/\Pi$ of many white dwarf pulsation modes observed by TESS. A consistent theoretical modeling of periods observed in these stars should in principle include GR effects to 1PN order