Asymptotic Giant Branch Variables in the Galaxy and the Local Group

AGB variables, particularly the large amplitude Mira type, are a vital step on the distance scale ladder. They will prove particularly important in the era of space telescopes and extremely large ground-based telescopes with adaptive optics, which will be optimized for infrared observing. Our current understanding of the distances to these stars is reviewed with particular emphasis on improvements that came from Hipparcos as well as on recent work on Local Group galaxies. In addition to providing the essential calibration for extragalactic distances Gaia may also provide unprecedented insight into the poorly understood mass-loss process itself.Comment: Accepted for publication in Astrophysics and Space Science. From a presentation at the conference "The Fundamental Cosmic Distance Scale: State of the Art and Gaia Perspective, Naples May 2011. 8 Pages, 9 Figure

Cepheid Parallaxes and the Hubble Constant

Revised Hipparcos parallaxes for classical Cepheids are analysed together with 10 HST-based parallaxes (Benedict et al.). In a reddening-free V,I relation we find that the coefficient of logP is the same within the uncertainties in our Galaxy as in the LMC, contrary to some previous suggestions. Cepheids in the inner region of NGC4258 with near solar metallicities (Macri et al.) confirm this result. We obtain a zero-point for the reddening-free relation and apply it to Cepheids in galaxies used by Sandage et al. to calibrate the absolute magnitudes of SNIa and to derive the Hubble constant. We revise their result from 62 to 70+/-5 km/s/Mpc. The Freedman et al. 2001 value is revised from 72 to 76+/-8 km/s/Mpc. These results are insensitive to Cepheid metallicity corrections. The Cepheids in the inner region of NGC4258 yield a modulus of 29.22+/-0.03(int) compared with a maser-based modulus of 29.29+/-0.15. Distance moduli for the LMC, uncorrected for any metallicity effects, are; 18.52+/-0.03 from a reddening-free relation in V,I; 18.47+/-0.03 from a period-luminosity relation at K; 18.45+/-0.04 from a period-luminosity-colour relation in J,K. Adopting a metallicity correction in V,I from Marci et al. leads to a true LMC modulus of 18.39+/-0.05.Comment: 9 pages, 1 figure, on-line material from [email protected]. Accepted for MNRA

The effect of dust obscuration in RR Tel on optical and IR long-term photometry and Fe II emission lines

Infrared and optical photometric and spectroscopic observations of the symbiotic nova RR Tel are used to study the effects and properties of dust in symbiotic binaries containing a cool Mira component, as well as showing "obscuration events" of increased absorption, which are typical for such Miras. A set of photometric observations of the symbiotic nova RR Tel in different wavelength bands - visual from 1949 to 2002 and near-infrared (JHKL) from 1975 to 2002 - are presented. The variability due to the normal Mira pulsation was removed from the JHKL data, which were then compared with the AAVSO visual light curve. The changes of the Fe II emission line fluxes during the 1996-2000 obscuration episode were studied in the optical spectra taken with the Anglo-Australian telescope. We discuss the three periods during which the Mira component was heavily obscured by dust as observed in the different wavelength bands. A change in the correlations of J with other infrared magnitudes was observed with the colour becoming redder after JD2446000. Generally, J-K was comparable, while K-L was larger than typical values for single Miras. A distance estimate of 2.5 kpc, based on the IR data, is given. A larger flux decrease for the permitted than for the forbidden Fe II lines, during the obscuration episode studied, has been found. There is no evidence for other correlations with line properties, in particular with wavelength, which suggests obscuration due to separate optically thick clouds in the outer layers.Comment: 19 pages, 11 figures, 3 table

Constraints on z~10 Galaxies from the Deepest HST NICMOS Fields

We use all available fields with deep NICMOS imaging to search for J dropouts (H<28) at z~10. Our primary data set for this search were the two J+H NICMOS parallel fields taken with the ACS HUDF. The 5 sigma limiting mags were 28.6 in J and 28.5 in H. Several shallower fields were also used: J+H NICMOS frames available over the HDF North, the HDF South NICMOS parallel, and the ACS HUDF. The primary selection criterion was (J-H)>1.8. 11 such sources were found in all search fields using this criterion. 8 of these were clearly ruled out as credible z~10 sources, either as a result of detections (>2 sigma) blueward of J or their colors redward of the break (H-K~1.5). The nature of the 3 remaining sources could not be determined from the data. The number appears consistent with the expected contamination from low-z interlopers. Analysis of the stacked images for the 3 candidates also suggests contamination. Regardless of their true redshifts, the actual number of z~10 sources must be <=3. To assess the significance of these results, two lower redshift samples (a z~3.8 B-dropout and z~6 i-dropout sample) were projected to z~8-12 using a (1+z)^{-1} size scaling. They were added to the image frames, and the selection repeated, giving 15.6 and 4.8 J-dropouts, respectively. This suggests that to the limit of this probe (0.3 L*) there has been evolution from z~3.8 and possibly from z~6. This is consistent with the strong evolution already noted at z~6 and z~7.5 relative to z~3-4. Even assuming that 3 sources from this probe are at z~10, the rest-frame continuum UV (~1500 A) luminosity density at z~10 (integrated down to 0.3 L*) is just 0.19_{-0.09}^{+0.13}x that at z~3.8 (or 0.19_{-0.10}^{+0.15}x including cosmic variance). However, if none of our sources is at z~10, this ratio has a 1 sigma upper limit of 0.07. (abridged)Comment: 13 pages, 3 figures, 2 tables, accepted for publication in the Astrophysical Journal Letter

The Distances of SNR W41 and overlapping HII regions

New HI images from the VLA Galactic Plane Survey show prominent absorption features associated with the supernovae remnant G23.3-0.3 (SNR W41). We highlight the HI absorption spectra and the $^{13}$CO emission spectra of eight small regions on the face of W41, including four HII regions, three non-thermal emission regions and one unclassified region. The maximum velocity of absorption for W41 is 78$\pm$2 km/s and the CO cloud at radial velocity 95$\pm$5 km/s is behind W41. Because an extended TeV source, a diffuse X-ray enhancement and a large molecular cloud at radial velocity 77$\pm$5 km/s are also projected at the center of W41, these yield the kinematic distance of 3.9 to 4.5 kpc for W41. For HII regions, our analyses reveal that both G23.42-0.21 and G23.07+0.25 are at the far kinematic distances ($\sim$9.9 kpc and $\sim$ 10.6 kpc respectively) of their recombination-line velocities (103$\pm$0.5 km/s and 89.6$\pm$2.1 km/s respectively), G23.07-0.37 is at the near kinematic distance (4.4$\pm$0.3 kpc) of its recombination-line velocity (82.7$\pm$2.0 km/s), and G23.27-0.27 is probably at the near kinematic distance (4.1$\pm$0.3 kpc) of its recombination-line velocity (76.1$\pm$0.6 km/s).Comment: 11 pages, 3 figs., 2 tables, accepted by A

El proyecto nefreduca : una plataforma educativa virtual para alumnos de secundaria hospitalizados por enfermedades crónicas de riñón

A pesar de avances médicos los jóvenes con enfermedades crónicas a menudo son hospitalizados durante largos períodos, y por consiguiente, no pueden mantener un ritmo de asistencia escolar normal. Esto puede traducirse a menudo en un menor nivel de alfabetización científica. A pesar de que muchos hospitales disponen de Aula hospitalaria; el acceso de estos jóvenes al currículum de ciencias es reducido, por falta de docentes especialistas y de los recursos específicos a estas y el contexto hospitalario. Con la finalidad de tratar estos problemas, se diseñó el proyecto Nefreduca. Esta comunicación presenta una tipología preliminar de las modificaciones de diseño basadas en evidencias a partir de los datos fase cíclica del proyecto. Los resultados muestran dos limitaciones principales a tener en cuenta en la enseñanza de las ciencias en el contexto educativo hospitalario

The Galactic Kinematics of Mira Variables

The galactic kinematics of Mira variables derived from radial velocities, Hipparcos proper motions and an infrared period-luminosity relation are reviewed. Local Miras in the 145-200day period range show a large asymmetric drift and a high net outward motion in the Galaxy. Interpretations of this phenomenon are considered and (following Feast and Whitelock 2000) it is suggested that they are outlying members of the bulge-bar population and indicate that this bar extends beyond the solar circle.Comment: 7 pages, 2 figure, to be published in Mass-Losing Pulsating Stars and their Circumstellar Matter, Y. Nakada & M. Honma (eds) Kluwer ASSL serie

Possible Recovery of SN 1961V In Hubble Space Telescope Archival Images

SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type V'' supernova. However, it has been argued that SN 1961V was not a genuine supernova, but instead the superoutburst of an eta Carinae-like luminous blue variable star. In particular, Filippenko et al. (1995, AJ, 110, 2261) used pre-refurbishment HST WFPC images and the known radio position of SN 1961V to conclude that the star survived the eruption and is likely coincident with a V \~ 25.6 mag, V-I ~ 1.9 mag object. Recently, Stockdale et al. (2001, AJ, 122, 283) recovered the fading SN 1961V at radio wavelengths and argue that its behavior is similar that of some Type II supernovae. We have analyzed post-refurbishment archival HST WFPC2 data and find that the new radio position is still consistent with the Filippenko et al. object, which has not changed in brightness or color, but is also consistent with an adjacent, fainter (I ~ 24.3 mag) and very red (V-I > 1.0 mag) object. We suggest that this fainter object could be the survivor of SN 1961V. Forthcoming HST observations may settle this issue.Comment: 8 pages, 6 figures, to appear in the PASP (2002 July issue

Using student experience to inform the design of an automated feedback system for essay answers

The SAFeSEA project (Supportive Automated Feedback for Short Essay Answers) aims to develop an automated feedback system to support university students as they write summative essays. Empirical studies carried out in the initial phase of the system’s development illuminated students’ approaches to and understandings of the essay-writing process. Findings from these studies suggested that, regardless of their experience of higher education, students consider essay writing as: 1) a sequential set of activities, 2) a process that is enhanced through particular sources of support and 3) a skill that requires the development of personal strategies. Further data collected from tutors offered insight into the feedback and reflection stages of essay writing. These perspectives offer important considerations for the ongoing, iterative development of this automated feedback system and indeed, for any institution developing tools to support students’ writing

On the difference between type E and A OH/IR stars

The observed SEDs of a sample of 60 OH/IR stars are fitted using a radiative transfer model of a dusty envelope. Among the whole sample, 21 stars have reliable phase-lag distances while the others have less accurate distances. L*-P,Mlr-P and Mlr-L* relations have been plotted for these stars. It is found that type E (with emission feature at 10um and type A (with absorption feature at 10um) OH/IR stars have different L*-P and Mlr-L* relations while both of them follow a single Mlr-P relation. The type E stars are proven to be located in the area without large scale dense interstellar medium while the type A stars are located probably in dense interstellar medium. It is argued here that this may indicate the two types of OH/IR stars have different chemical composition or zero age main sequence mass and so evolve in different ways. This conclusion has reinforced the argument by Chen et al.(2001) who reached a similar conclusion from the galactic distribution of about 1000 OH/IR stars with the IRAS low-resolution spectra (LRS).Comment: 6 pages, 9 figures, 2 table