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The nature of Galactic interstellar extinction is tested using reddening line parameters for several fields in conjunction with equivalent widths $W(\lambda4430)$ for the diffuse interstellar band at $4430$ \AA. The Cardelli et al.$\;$relations [29] at infrared, optical, and ultraviolet wavelengths are inconsistent with the newly-derived quadratic variation of $R_V({\rm observed})$ on reddening slope $X$. A minimum of $R_V=2.82\pm0.06$ exists for $X=0.83\pm0.10$, and is argued to represent true Galactic extinction described by $A(\lambda)\propto \lambda^{-1.375}$. It matches expectations for a new description of extinction in the infrared, optical, and ultraviolet by Zagury [32]. Additional consequences, reddened stars with no 2175 \AA$\;$feature and a correlation of normalized $\lambda4430$ absorption with $X$, are not predicted by the Cardelli et al.$\;$relation [29]. Known variations in $X$ from 0.62 to 0.83, and corresponding variations in $R_V({\rm observed})$ from 4.0 to 2.8, presumably result from forward-scattered starlight in the ultraviolet contaminating optical light of stars affected by dust extinction. A new understanding of the true nature of interstellar extinction is important for establishing an accurate picture of the extragalactic distance scale, which in turn is related to our understanding of the nature of the Universe., Comment: To appear in the CJP

We present Hubble Space Telescope (HST) and ground-based optical and near-infrared observations of SN 2005hk and SN 2008A, typical members of the Type Iax class of supernovae (SNe). Here we focus on late-time observations, where these objects deviate most dramatically from all other SN types. Instead of the dominant nebular emission lines that are observed in other SNe at late phases, spectra of SNe 2005hk and 2008A show lines of Fe II, Ca II, and Fe I more than a year past maximum light, along with narrow [Fe II] and [Ca II] emission. We use spectral features to constrain the temperature and density of the ejecta, and find high densities at late times, with n_e >~ 10^9 cm^-3. Such high densities should yield enhanced cooling of the ejecta, making these objects good candidates to observe the expected "infrared catastrophe," a generic feature of SN Ia models. However, our HST photometry of SN 2008A does not match the predictions of an infrared catastrophe. Moreover, our HST observations rule out a "complete deflagration" that fully disrupts the white dwarf for these peculiar SNe, showing no evidence for unburned material at late times. Deflagration explosion models that leave behind a bound remnant can match some of the observed properties of SNe Iax, but no published model is consistent with all of our observations of SNe 2005hk and 2008A., Comment: 20 pages, 15 figures

New X-ray (XMM-Newton) and JHKs (OMM) observations for members of the star cluster Alessi 95, which Turner et al.(2012) discovered hosts the classical Cepheid SU Cas, were used in tandem with UCAC3 (proper motion) and 2MASS observations to determine precise cluster parameters: E(J-H)=0.08+-0.02 and d=405+-15 pc. The ensuing consensus among cluster, pulsation, IUE, and trigonometric distances (d=414+-5(se)+-10(sd) pc) places SU Cas in a select group of nearby fundamental Cepheid calibrators (Delta Cep, Zeta Gem). High-resolution X-ray observations may be employed to expand that sample as the data proved pertinent for identifying numerous stars associated with SU Cas. Acquiring X-ray observations of additional fields may foster efforts to refine Cepheid calibrations used to constrain H_0., Comment: To appear in ApJ

The parameters for the newly-discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically-observed B and A-type stars near SU Cas follow a reddening relation described by E(U-B)/E(B-V)=0.83+0.02*E(B-V), implying a value of R=Av/E(B-V)~2.8 for the associated dust. Alessi 95 has a mean reddening of E(B-V)_(B0)=0.35+-0.02 s.e., an intrinsic distance modulus of Vo-Mv=8.16+-0.04 s.e. (+-0.21 s.d.), d=429+-8 pc, and an estimated age of 10^8.2 yr from ZAMS fitting of available UBV, CCD BV, NOMAD, and 2MASS JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B-V)=0.33+-0.02 and a luminosity of =-3.15+-0.07 s.e., consistent with overtone pulsation (P_FM=2.75 d), as also implied by the Cepheid's light curve parameters, rate of period increase, and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, its pulsation parallax derived from the infrared surface brightness technique, and Hipparcos parallaxes, which all agree to within a few percent., Comment: Accepted for Publication (MNRAS)

New and existing CORAVEL, UBVJHKs, HST, HIP/Tycho, ARO, KPNO, and DAO observations imply that the fundamental Cepheid calibrator Zeta Gem is a cluster member. The following parameters were inferred for Zeta Gem from cluster membership and are tied to new spectral classifications (DAO) established for 26 nearby stars (e.g., HD53588/B7.5IV, HD54692/B9.5IV): E(B-V)=0.02+-0.02, log t=7.85+-0.15, and d=355+-15 pc. The mean distance to Zeta Gem from cluster membership and six recent estimates (e.g., IRSB) is d=363+-9(se)+-26(sd) pc. The results presented here support the color-excess and HST parallax derived for the Cepheid by Benedict et al. (2007). Forthcoming precise proper motions (DASCH) and Chandra/XMM-Newton observations of the broader field may be employed to identify cluster members, bolster the cluster's existence, and provide stronger constraints on the Cepheid's fundamental parameters., Comment: To appear in ApJ Letters

The likely membership of the planetary nebula Abell 8 (PN G167.0--00.9) in the open cluster Bica 6 is confirmed by CCD spectra, UBV(RI)c photometry, and radial velocities for luminous cluster stars. The reddening, estimated distance, and radial velocity of the planetary nebula agree with parameters derived for Bica 6 of E(B-V)=0.42, d=1.60+-0.11 kpc, and Vr=57+-1 km/s, with a cluster age of 1 Gyr, a diagnostic blue hook, and a few blue stragglers, including a peculiar B1 Vnn star (HDE 277593) that may be a post-AGB star. The results identify Bica 6 as a potential calibrator of the planetary nebula distance scale. The central star of the planetary nebula has a reddening of E(B-V)=0.49+-0.02, with a possible circumnebular excess, and an estimated luminosity of Mv=+7.44+-0.16. It is also an optical double in 2MASS images, with a likely progenitor according to evolutionary considerations being a late B-type dwarf of ~2.3 Msun., Comment: Accepted for Publication (PASP)

SRC variables are M supergiants, precursors to Type II supernovae, that vary in brightness with moderately regular periods of order 100-1000 days. Although identified as pulsating stars that obey their own period-luminosity relation, few have been examined in enough detail to follow the temperature and spectral changes that they undergo during their long cycles. The present study examines such changes for several SRC variables revealed by CCD spectra obtained at the Dominion Astrophysical Observatory (DAO) during 2005-2009, as well as by archival spectra from the DAO (and elsewhere) for some stars from the 1960s to 1980s, and Cambridge radial velocity spectrometer measures for Betelgeuse. Described here is our classification procedure and information on the spectral type and radial velocity changes in three of the stars. The results provide insights into the pulsation mechanism in M supergiants., Comment: To appear in the Odessa Variable Stars 2010 conference proceedings (see http://uavso.org.ua/?page=vs2010), edited by I. Andronov and V. Kovtyukh

The Galactic calibration of the period-luminosity (PL) relation for classical Cepheids is examined using trigonometric, open cluster, and pulsation parallaxes, which help establish independent versions of the relationship. The calibration is important for the continued use of classical Cepheids in constraining cosmological models (by refining estimates for H_0), for defining zero-points for the SNe Ia and population II (Type II Cepheids/RR Lyrae variables) distance scales, for clarifying properties of the Milky Way's spiral structure, and for characterizing dust extinction affecting Cepheids in the Milky Way and other galaxies. Described is a program to extend and refine the Galactic Cepheid PL relation by obtaining UBVRIJHKs photometry and spectra for stars in open clusters suspected of hosting classical Cepheids, using the the facilities of the OAMM, DAO, AAVSO, and ARO., Comment: To appear in the Odessa variable stars 2010 conference proceedings (see http://uavso.org.ua/?page=vs2010), edited by I. Andronov and V. Kovtyukh

We describe a variability study of the moderately old open cluster NGC 6819. We have detected 4 new detached eclipsing binaries near the cluster turnoff (one of which may be in a triple system). Several of these systems should be able to provide mass and radius information, and can therefore constrain the age of the cluster. We have also newly detected one possible detached binary member about 3.5 magnitudes below the turnoff. One EW-type binary (probably not a cluster member) shows unusually strong night-to-night light curve variations in sets of observations separated by 8 years. According to the best current information, the three brightest variables we detected (2 of them new) are cluster members, making them blue stragglers. One is a delta Scu pulsating variable, one is a close but detached binary, and the third contains a detached short period binary that shows total eclipses. In each case, however, there is evidence hinting that the system may have been produced through the interaction of more than two stars., Comment: 33 pages, 15 figures, accepted to AJ

The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61 235 (V831 Cas), is an intriguing system on the outskirts of the open cluster NGC 663. It contains the slowest X-ray pulsar known with a pulse period of around 1400s and, primarily from the study of variation in the emission line profile of H alpha, it is known to have a Be decretion disk with a one-armed density wave period of approximately 1240d. Here we present the results of an extensive photometric campaign, supplemented with optical spectroscopy, aimed at measuring short time-scale periodicities. We find three significant periodicities in the photometric data at, in order of statistical significance, 0.34d, 0.67d and 0.10d. We give arguments to support the interpretation that the 0.34d and 0.10d periods could be due to stellar oscillations of the B type primary star and that the 0.67d period is the spin period of the Be star with a spin axis inclination of 23 +10 -8 degrees. We measured a systemic velocity of -37.0 +- 4.3 km/s confirming that LS I+61 235 has a high probability of membership in the young cluster NGC 663 from which the system's age can be estimated as 20-25 Myr. From archival RXTE ASM data we further find "super" X-ray outbursts roughly every 450d. If these super outbursts are caused by the alignment of the compact star with the one-armed decretion disk enhancement, then the orbital period is approximately 330d., Comment: Accepted 2008 October 24 MNRAS

We present the results of a project to detect small (~1 km) main-belt asteroids with the 3.6 meter Canada-France-Hawaii Telescope (CFHT). We observed in 2 filters (MegaPrime g' and r') in order to compare the results in each band. Owing to the observational cadence we did not observe the same asteroids through each filter and thus do not have true colour information. However strong differences in the size distributions as seen in the two filters point to a colour-dependence at these sizes, perhaps to be expected in this regime where asteroid cohesiveness begins to be dominated by physical strength and composition rather than by gravity. The best fit slopes of the cumulative size distributions (CSDs) in both filters tend towards lower values for smaller asteroids, consistent with the results of previous studies. In addition to this trend, the size distributions seen in the two filters are distinctly different, with steeper slopes in r' than in g'. Breaking our sample up according to semimajor axis, the difference between the filters in the inner belt is found to be somewhat less pronounced than in the middle and outer belt, but the CSD of those asteroids seen in the r' filter is consistently and significantly steeper than in g' throughout. The CSD slopes also show variations with semimajor axis within a given filter, particularly in r'. We conclude that the size distribution of main belt asteroids is likely to be colour dependent at kilometer sizes and that this dependence may vary across the belt., Comment: 28 pages, 5 figures, submitted to the Astronomical Journal

The acceleration of the expansion of the universe, and the need for Dark Energy, were inferred from the observations of Type Ia supernovae (SNe Ia). There is consensus that SNe Ia are thermonuclear explosions that destroy carbon-oxygen white dwarf stars that accrete matter from a companion star, although the nature of this companion remains uncertain. SNe Ia are thought to be reliable distance indicators because they have a standard amount of fuel and a uniform trigger -- they are predicted to explode when the mass of the white dwarf nears the Chandrasekhar mass -- 1.4 solar masses. Here we show that the high redshift supernova SNLS-03D3bb has an exceptionally high luminosity and low kinetic energy that both imply a super-Chandrasekhar mass progenitor. Super-Chandrasekhar mass SNe Ia should preferentially occur in a young stellar population, so this may provide an explanation for the observed trend that overluminous SNe Ia only occur in young environments. Since this supernova does not obey the relations that allow them to be calibrated as standard candles, and since no counterparts have been found at low redshift, future cosmology studies will have to consider contamination from such events., Comment: 9 pages, 4 figures. To appear in Nature Sept. 21. Accompanying News & Views in same issue. Supplementary information available at www.nature.com/nature