HST Images of the Eclipsing Pulsar B1957+20

We have obtained images of the eclipsing pulsar binary PSR~B1957+20 using the Planetary Camera of the Hubble Space Telescope. The high spatial resolution of this instrument has allowed us to separate the pulsar system from a nearby background star which has confounded ground-based observations of this system near optical minimum. Our images limit the temperature of the backside of the companion to T \simlt 2800~K, about a factor of two less than the average temperature of the side of the companion facing the pulsar, and provide a marginal detection of the companion at optical minimum. The magnitude of this detection is consistent with previous work which suggests that the companion nearly fills its Roche lobe and is supported through tidal dissipation.Comment: uuencoded gzip-compressed postscript: 10 pages of text plus 2 postscript figures. This preprint is available in various formats from http://archer.stsci.edu:1024/~fruchter/HST_1957/1957.html or http://electra.stsci.edu:1024/~fruchter/HST_1957/1957.htm

Shipment consolidation with two demand classes: Rationing the dispatch capacity

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.ejor.2018.03.016 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/We analyze the problem faced by a logistics provider that dispatches shipment orders (parcels or larger packages) of two order classes, viz. expedited and regular. Shipment orders arrive according to a compound Poisson process for each class. Upon an arrival, the logistics provider may continue consolidating arriving orders by paying a holding cost. Alternatively, the provider may dispatch, at a fixed cost, a vehicle containing (a portion of) the load consolidated so far. In addition, the provider must specify the composition of each dispatch by allocating (rationing) the volume of the vehicle between expedited and regular shipment orders. We model this problem as a continuous-time Markov Decision Process and minimize the expected discounted total cost. We prove the existence of quantity-based optimal threshold policies under particular conditions. We also structurally analyze the thresholds of these optimal policies. Based on these structural properties, we develop an efficient solution approach for large problem instances which are difficult to solve using the conventional policy-iteration method. For two real-life applications, we show that the quantity-based threshold policies derived using the proposed approach outperform the time policies used in practice.Türkiye Bilimsel ve Teknolojik Araştirma Kurumu [1059B191400567

Studying the Pulsation of Mira Variables in the Ultraviolet

We present results from an empirical study of the Mg II h & k emission lines of selected Mira variable stars, using spectra from the International Ultraviolet Explorer (IUE). The stars all exhibit similar Mg II behavior during the course of their pulsation cycles. The Mg II flux always peaks after optical maximum near pulsation phase 0.2-0.5, although the Mg II flux can vary greatly from one cycle to the next. The lines are highly blueshifted, with the magnitude of the blueshift decreasing with phase. The widths of the Mg II lines are also phase-dependent, decreasing from about 70 km/s to 40 km/s between phase 0.2 and 0.6. We also study other UV emission lines apparent in the IUE spectra, most of them Fe II lines. These lines are much narrower and not nearly as blueshifted as the Mg II lines. They exhibit the same phase-dependent flux behavior as Mg II, but they do not show similar velocity or width variations.Comment: 26 pages, 12 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty; to appear in Ap

The relational dimensions of renovation: Implications for retrofit policy

Retrofitting the UK's housing stock is essential if the UK is to meet its climate commitments. Wider research has addressed how weaknesses in the drafting and implementation of retrofit policy have slowed progress in this area, including the tendency to treat homeowners as discrete, isolated decision makers. We contribute to this research by exploring the wider dynamics that underpin decision-making in and around households. We make this contribution by adapting Hargreaves and Middlemiss's research into the social relations of daily energy use, and Zelizer's research into the social relations of money, to consider how social relations influence decision-making over home renovations. Our findings are based on semi-structured interviews with homeowners in Otley, West Yorkshire, which we conducted from September to December 2021. This interview data demonstrates how the dynamic nature of relations with family and friends, tradespeople, gender, and money, shapes the reasons why people undertake renovations and what they aim to gain from undertaking these works. Focusing on wider renovations enabled us to speak with people who are not already engaged with retrofit policy, shedding light on possible interventions that target ‘able-to-pay’ owner-occupiers. For instance, we highlight the need to identify how people develop trust with tradespeople; account for different social groups' relations to the home; and to foreground how the role of the home changes through time

High-dispersion absorption-line spectroscopy of AE Aqr

High-dispersion time-resolved spectroscopy of the unique magnetic cataclysmic variable AE Aqr is presented. A radial velocity analysis of the absorption lines yields K2= 168.7 ± 1 km s−1. Substantial deviations of the radial velocity curve from a sinusoid are interpreted in terms of intensity variations over the secondary star's surface. A complex rotational velocity curve as a function of orbital phase is detected which has a modulation frequency of twice the orbital frequency, leading to an estimate of the binary inclination angle that is close to 70°. The minimum and maximum rotational velocities are used to indirectly derive a mass ratio of q= 0.6 and a radial velocity semi-amplitude of the white dwarf of K1= 101 ± 3 km s−1. We present an atmospheric temperature indicator, based on the absorption-line ratio of Fe I and Cr I lines, whose variation indicates that the secondary star varies from K0 to K4 as a function of orbital phase. The ephemeris of the system has been revised, using more than 1000 radial velocity measurements, published over nearly five decades. From the derived radial velocity semi-amplitudes and the estimated inclination angle, we calculate that the masses of the stars are M1= 0.63 ± 0.05 M⊙; M2= 0.37 ± 0.04 M⊙, and their separation is a= 2.33 ± 0.02 R⊙. Our analysis indicates the presence of a late-type star whose radius is larger, by a factor of nearly 2, than the radius of a normal main-sequence star of the same mass. Finally, we discuss the possibility that the measured variations in the rotational velocity, temperature and spectral type of the secondary star as functions of orbital phase may, like the radial velocity variations, be attributable to regions of enhanced absorption on the star's surface

Investigation relative to the Roentgen Satellite (ROSAT)

Reports include: High Resolution Observations of the Central Region of M31; The X-ray Emission of Low-X-ray-Luminosity Early-Type Galaxies: Gas Versus Compact Sources; Interaction Between Cluster Gas and Radio Features of Cygnus A; Hot Gas and Dark Halos in Early-Type Galaxies; A Gravitational Lens in X-rays - 0957+461; How Massive are Early-Type Galaxies?; Three Crab-Like SNR in the Large Magellanic Cloud; and Soft X-ray Emission from Boundary Layers in Cataclysmic Variables. Papers submitted to the Astrophysical Journal are attached

The NASA X-Ray Mission Concepts Study

The 2010 Astrophysics Decadal Survey recommended a significant technology development program towards realizing the scientific goals of the International X-ray Observatory (IXO). NASA has undertaken an X-ray mission concepts study to determine alternative approaches to accomplishing IXO's high ranking scientific objectives over the next decade given the budget realities, which make a flagship mission challenging to implement. The goal of the study is to determine the degree to which missions in various cost ranges from $300M to$2B could fulfill these objectives. The study process involved several steps. NASA released a Request for Information in October 2011, seeking mission concepts and enabling technology ideas from the community. The responses included a total of 14 mission concepts and 13 enabling technologies. NASA also solicited membership for and selected a Community Science Team (CST) to guide the process. A workshop was held in December 2011 in which the mission concepts and technology were presented and discussed. Based on the RFI responses and the workshop, the CST then chose a small group of notional mission concepts, representing a range of cost points, for further study. These notional missions concepts were developed through mission design laboratory activities in early 2012. The results of all these activities were captured in the final X-ray mission concepts study report, submitted to NASA in July 2012. In this presentation, we summarize the outcome of the study. We discuss background, methodology, the notional missions, and the conclusions of the study report

Developing a relational approach to energy demand: A methodological and conceptual guide

In a recent review of research on the role of social relations in shaping energy demand, authors documented increasing interest in relational approaches to energy [1]. Relational approaches to energy conceive of human behaviour as produced and reproduced by social relations and interactions, placing relationships at the centre of inquiry, as well as understanding these relationships in the context of infrastructure and the built environment. In this paper, we build on a relational approach in new economic sociology, and on our research project about the social relations of energy retrofit, to offer a methodological and conceptual guide to those working on energy demand topics. We detail the ontological and epistemological starting points of our relational approach, and articulate how research can be designed to capture the role of social relations in shaping decision-making on energy, as well as to offer innovative insights for policy-makers and practitioners. We use our experience in a research project on energy retrofit as a case study, reflecting on the practical aspects of this research approach to provide suggestions for research design for those interested in doing similar work. This includes defining key concepts and the way they interact in a conceptual framework for a relational approach to energy. We also offer some conceptually driven research questions as a starting point for energy research projects. We finish by discussing the potential for further application of these ideas in research, policy and practice