Carbon-Rich Mira Variables: Radial Velocities and Distances

Optical radial velocities have been measured for 38 C-type Mira variables. These data together with others in the literature are used to study the differences between optical and CO mm observations for C-Miras and the necessary corrections to the optical velocities are derived in order to obtain the true radial velocities of the variables. The difference between absorption and emission line velocities is also examined. A particularly large difference (+30 km\s) is found in the case of the H-alpha emission line. A catalogue is given of 177 C-Miras with estimated distances and radial velocities. The distances are based on bolometric magnitudes derived in Paper I using SAAO observations or (for 60 of the stars) using non-SAAO photometry. In the latter case the necessary transformations to the SAAO system are derived. These data will be used in paper III to study the kinematics of the C-Miras.Comment: 11 pages, accepted for publication in MNRA

Adaptive Filters Revisited - RFI Mitigation in pulsar observations

Pulsar detection and timing experiments are applications where adaptive filters seem eminently suitable tools for radio-frequency-interference (RFI) mitigation. We describe a novel variant which works well in field trials of pulsar observations centred on an observing frequency of 675 MHz, a bandwidth of 64 MHz and with 2-bit sampling. Adaptive filters have generally received bad press for RFI mitigation in radio astronomical observations with their most serious drawback being a spectral echo of the RFI embedded in the filtered signals. Pulsar observations are intrinsically less sensitive to this as they operate in the (pulsar period) time domain. The field trials have allowed us to identify those issues which limit the effectiveness of the adaptive filter. We conclude that adaptive filters can significantly improve pulsar observations in the presence of RFI.Comment: Accepted for publication in Radio Scienc

Remarkable changes in the near-infrared spectrum of the nova-like variable V4332 Sgr

We report on recent near-IR observations of V4332 Sgr - the nova-like variable that erupted in 1994. Its rapid, post-outburst evolution to a cool M type giant/supergiant, soon after its outburst, had showed that it was an unusual object differing from other eruptive variables like classical/symbiotic novae or born-again AGB stars. The present study of V4332 Sgr was motivated by the keen interest in the recent eruption of V838 Mon - which along with V4332 Sgr - is believed to belong to a new class of objects (we propose they may be called "quasi-novae"). Our observations show new developments in the evolution of V4332 Sgr. The most striking feature is the detection of several molecular bands of AlO - a rarely seen molecule in astronomical spectra - in the JHK spectra. Many of these bands are being detected for the first time. The only other detection of some of these AlO bands are in V838 Mon, thereby showing further spectral similarities between the two objects. JHK photometry shows the development of a new dust shell around V4332 Sgr with a temperature of ~ 900K. This dust shell does not appear to be associated with ejecta of the 1994 outburst but is due to a second mass-loss episode which is not expected in a classical nova outburst. The cold molecular environment, suggested by the AlO emission, is also not expected in novae ejecta. We model the AlO bands and also discuss the possible formation mechanism of the AlO.Comment: To appear in Ap.J(L), 3 figure

Rotational spectroscopy of AlO: Low N transitions of astronomical interest in the X^2 Sigma^+ state

The detection of rotational transitions of the AlO radical at millimeter wavelengths from an astronomical source has recently been reported. In view of this, rotational transitions in the ground X^2 Sigma^+ state of AlO have been reinvestigated. Comparisons between Fourier transform and microwave data indicate a discrepancy regarding the derived value of gamma_D in the v = 0 level of the ground state. This discrepancy is discussed in the light of comparisons between experimental data and synthesized rotational spectra in the v = 0, 1 and 2 levels of X^2 Sigma^+. A list of calculated rotational lines in v = 0, 1 and 2 of the ground state up to N' = 11 is presented which should aid astronomers in analysis and interpretation of observed AlO data and also facilitate future searches for this radical.Comment: To appear in Astronomy and Astrophysic

Euthanasia and counterfactual consent.

Counterfactuals about what a patient would consent to, if he were able to consent, are often cited as justifications, or partial justifications, for acts of euthanasia. In virtue of this fact, they deserve special scrutiny by moral philosophers. In Chapter I, I examine terminology that is essential to further understanding the relationship between euthanasia and counterfactual consent. I propose a definition of \u27euthanasia\u27, an analysis of \u27consent\u27, and I present a brief description of counterfactuals. In Chapter II, I consider two questions. The first is, When it is appropriate to invoke counterfactual consent in an attempt to justify an act of euthanasia? By making use of an improved version of the voluntary, nonvoluntary, and involuntary distinction among acts of euthanasia, I am able to determine when it is appropriate to cite counterfactuals about consent in an attempt to justify an act of euthanasia. The second is, to what end is counterfactual consent used? I contend that counterfactual consent does morally justify some acts of euthanasia, and defend an argument for this claim. Finally, I look at the role of counterfactual consent as a possible legal justification for acts of euthanasia. In Chapter III, I use possible world semantics to analyze counterfactual consent. Traditional counterfactuals are determined to be true if in the closest world at which their antecedent is true, their consequent is also true. Counterfactuals about consent have a less straightforward reading. I consider and reject several possible ways of reading counterfactuals about consent, before settling on the correct reading of counterfactuals about consent. In Chapter IV, I consider evidence for the truth of claims about counterfactual consent. I consider and reject the claim that no counterfactual is either true or false. I examine both Living Wills and the practice of surrogacy, neither of which offers sufficient evidence for the truth of claims about counterfactual consent. In Chapter V, I contrast counterfactual consent with actual consent. I review and refute the arguments for the claim that actual consent is preferable to counterfactual consent. I conclude by presenting a principle about the relationship between actual and counterfactual consent

Infrared Spectroscopy of U Equulei's Warm Circumstellar Gas

Medium and high resolution spectroscopy of U Equulei from 1 to 4 microns during 1997-2003 has revealed information about its unusual circumstellar envelope, observed previously at optical and radio wavelengths. Strong absorption bands of H2O and of CO dominate the 1-4um spectrum. The gas has a mean temperature of 600 K and 12C/13C =< 10. The CO 2-0 line profiles and velocities imply no net ejection or infall and indicate either rapid radial gas motions being seen along a narrow continuum beam, or absorption by orbiting gas that is nearly coincident with a highly extended continuum source. The gas could be located in a disk-like structure. The observed high column densities of warm CO and H2 normally would be associated with sufficient dust to completely obscure the star at optical wavelengths. The observations thus indicate either a highly abnormal gas-to-dust ratio, consistent with the earlier optical observation of abundant refractory metal oxides in the circumstellar gas, or peculiar geometry and/or illumination.Comment: 21 pages incl. 8 postscript figures and 1 table; typos correcte

J-type Carbon Stars in the Large Magellanic Cloud

A sample of 1497 carbon stars in the Large Magellanic Cloud has been observed in the red part of the spectrum with the 2dF facility on the AAT. Of these, 156 have been identified as J-type (i.e. 13C-rich) carbon stars using a technique which provides a clear distinction between J stars and the normal N-type carbon stars that comprise the bulk of the sample, and yields few borderline cases. A simple 2-D classification of the spectra, based on their spectral slopes in different wavelength regions, has been constructed and found to be related to the more conventional c- and j-indices, modified to suit the spectral regions observed. Most of the J stars form a photometric sequence in the K - (J-K) colour magnitude diagram, parallel to and 0.6 mag fainter than the N star sequence. A subset of the J stars (about 13 per cent) are brighter than this J star sequence; most of these are spectroscopically different from the other J stars. The bright J stars have stronger CN bands than the other J stars and are found strongly concentrated in the central regions of the LMC. Most of the rather few stars in common with Hartwick and Cowley's sample of suspected CH stars are J stars. Overall, the proportion of carbon stars identified as J stars is somewhat lower than has been found in the Galaxy. The Na D lines are weaker in the LMC J stars than in either the Galactic J stars or the LMC N stars, and do not seem to depend on temperature.Comment: 19 pages, 21 figures, Latex; in press, MNRA

Statistically Stable Estimates of Variance in Radioastronomical Observations as Tools for RFI Mitigation

A selection of statistically stable (robust) algorithms for data variance calculating has been made. Their properties have been analyzed via computer simulation. These algorithms would be useful if adopted in radio astronomy observations in the presence of strong sporadic radio frequency interference (RFI). Several observational results have been presented here to demonstrate the effectiveness of these algorithms in RFI mitigation

A morphological algorithm for improving radio-frequency interference detection

A technique is described that is used to improve the detection of radio-frequency interference in astronomical radio observatories. It is applied on a two-dimensional interference mask after regular detection in the time-frequency domain with existing techniques. The scale-invariant rank (SIR) operator is defined, which is a one-dimensional mathematical morphology technique that can be used to find adjacent intervals in the time or frequency domain that are likely to be affected by RFI. The technique might also be applicable in other areas in which morphological scale-invariant behaviour is desired, such as source detection. A new algorithm is described, that is shown to perform quite well, has linear time complexity and is fast enough to be applied in modern high resolution observatories. It is used in the default pipeline of the LOFAR observatory.Comment: Accepted for publication in A&