Search

We present the flrst results of a wide fleld survey for planetary nebulae throughout M31 undertaken at the KPNO 0.9m telescope with the Mosaic camera. So far, images in [O III]‚5007 and its continuum fllter have been analyzed. Our survey appears to be at least 90% complete to about 2 mag below the peak of the planetary nebula luminosity function. Over 900 planetary nebulae candidates have been found within a 12 square degree area.

We report FUSE and new deep optical spectroscopic observations of PN G 135.9+55.9, the most oxygen-poor planetary nebula located in the Galactic halo. These observations allow us to estimate the gravity of the central star by fitting the profile of the observed H I absorption lines with NLTE model atmospheres. Our best fit implies that the central star is still in a pre-white dwarf stage. We also find large variability of the radial velocities of the absorption component of the Balmer lines on a timescale of hours. This is direct evidence that the nucleus of PN G 135.9+55.9 is a close binary. The large semi-amplitude of the radial velocity variations and the probably short period suggest a massive compact companion, likely a white dwarf. Although our orbital solutions are very preliminary, they indicate that the total mass of the system probably exceeds the Chandrasekhar limit. If confirmed, this would make this binary the potential progenitor of a type Ia supernova., Accepted for publication in Ap.J

The impact of the cluster environment on the evolution of dwarf galaxies is investigated by comparing the properties of a sample of dwarf irregulars (dIs) in the Virgo Cluster with a control sample of nearby ("field") dIs having oxygen abundances derived from [O III]4363 measurements and measured distances from resolved stellar constituents. Spectroscopic data are obtained for H II regions in 11 Virgo dIs distributed in the central and outer regions of the cluster. To ensure that oxygen abundances are derived in a homogeneous manner, oxygen abundances for field and Virgo dIs are computed using the bright-line method and compared with abundances directly obtained from [O III]4363, where available. They are found to agree to within about 0.2 dex with no systematic offset. At a given optical luminosity, there is no systematic difference in oxygen abundance between the sample of Virgo dIs and the sample of nearby dIs. However, five of the eleven Virgo dIs exhibit much lower baryonic gas fractions than field dIs at comparable oxygen abundances. Using field dIs as a reference, a gas-deficiency index for dIs is constructed, making it possible quantitatively to identify which galaxies have lost gas. For the Virgo sample, some of the dwarfs are gas-deficient by a factor of 30. The gas-deficiency correlates roughly with the X-ray surface brightness of the intracluster gas. Ram-pressure stripping can best explain the observed gas-poor dIs in the cluster sample. Together with the lack of significant fading and reddening of the gas-poor dIs compared to gas-normal dIs, these observations suggest that the gas-poor dIs in Virgo have recently encountered the intracluster medium for the first time. Faded remnants of gas-poor dIs in Virgo will resemble bright dwarf ellipticals presently seen in the cluster core., Comment: Accepted, A.J.; 22 pgs. (emulateapj AASTeX 5.02), 28 jpg figures. Full paper w. incl. figures at http://www.mpia.de/homes/lee/paper2.ps.gz

Thanks to recent advances in instrumentation, metal abundances now can be measured routinely for PNe situated in galaxies beyond the Magellanic Clouds. Consequently, PNe are becoming a valuable tool for studying the chemical evolution of external galaxies, especially those which are not forming stars. Here we review problems and progress in this exciting nascent field of interdisciplinary research.

We report on the first open-use based Atacama Large Millimeter/submm Array (ALMA) 345-GHz observation for the late afterglow phase of GRB131030A. The ALMA observation constrained a deep limit at 17.1 d for the afterglow and host galaxy. We also identified a faint submillimeter source (ALMAJ2300-0522) near the GRB131030A position. The deep limit at 345 GHz and multifrequency observations obtained using {\it Swift} and RATIR yielded forward shock modeling with a two-dimensional relativistic hydrodynamic jet simulation and described X-ray excess in the afterglow. The excess was inconsistent with the synchrotron self-inverse Compton radiation from the forward shock. The host galaxy of GRB131030A and optical counterpart of ALMAJ2300-0522 were also identified in the SUBARU image. Based on the deep ALMA limit for the host galaxy, the 3-$��$ upper limits of IR luminosity and the star formation rate (SFR) is estimated as $L_{IR}, 16 pages, 7 figures, 1 table, PASJ in press

We present the results of optical spectroscopy of a newly discovered H II region residing in the H I gas cloud located between the dwarf irregular galaxy UGC 7636 and the giant elliptical galaxy NGC 4472 in the Virgo Cluster. By comparing UGC 7636 with dwarf irregular galaxies in the field, we show that the H I cloud must have originated from UGC 7636 because (1) the oxygen abundance of the cloud agrees with that expected for a galaxy with the blue luminosity of UGC 7636, and (2) M_{H I}/L_B for UGC 7636 becomes consistent with the measured oxygen abundance of the cloud if the H I mass of the cloud is added back into UGC 7636. It is likely that tides from NGC 4472 first loosened the H I gas, after which ram-pressure stripping removed the gas from UGC 7636., 12 pages, 2 eps figures (AASTeX 5.0); accepted for publication in ApJ Letters

We have selected a group of 100 evolved planetary nebulae (PNe) and study their kinematics based upon spatially-resolved, long-slit, echelle spectroscopy. The data have been drawn from the San Pedro M\'artir Kinematic Catalogue of PNe (L\'opez et al. 2012). The aim is to characterize in detail the global kinematics of PNe at advanced stages of evolution with the largest sample of homogenous data used to date for this purpose. The results reveal two groups that share kinematics, morphology, and photo-ionization characteristics of the nebular shell and central star luminosities at the different late stages under study.The typical flow velocities we measure are usually larger than seen in earlier evolutionary stages, with the largest velocities occurring in objects with very weak or absent [N II] \lambda 6584 line emission, by all indications the least evolved objects in our sample. The most evolved objects expand more slowly. This apparent deceleration during the final stage of PNe evolution is predicted by hydrodynamical models, but other explanations are also possible. These results provide a template for comparison with the predictions of theoretical models., Comment: Accepted for publication in ApJ. It is tentatively scheduled for the July 1, 2013, V771 - 1 issue

The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project., La lista completa de autores puede consultarse en el documento o en la página web de la revista., Facultad de Ingeniería

In this contribution we present the results of measuring the bulk outflow, or global expansion velocities for a large number of planetary nebulae (PNe) that span a wide range of evolutionary stages and different stellar populations. The sample comprises 133 PNe from the galactic bulge, 100 mature and highly evolved PNe from the disk, 11 PNe from the galactic halo and 15 PNe with very low central star masses and low metallicities, for a total of 259 PNe. The long-slit, echelle data are drawn from the SPM Kinematic Catalogue of Galactic Planetary Nebulae. These results reveal from a statistical perspective the kinematic evolution of the expansion velocities of PNe in relation with the changing characteristics of the central star's wind and ionizing luminosity and as a function of the evolutionary rate determined by the central star (CS) mass. The large number of PNe utilized in this work for each group of PNe under study and the homogeneity of the data provide for the first time a solid benchmark from observations for models predictions. This project is still in progress and aims at measuring expansion velocities for about 300 more galactic PNe with the aim of providing a reliable parametric description of their expansion velocity in terms of different populations, morphologies, evolutionary stages and CS masses.

We analyze the internal kinematics of 26 Planetary Nebulae (PNe) with low metallicity that appear to derive from progenitor stars of the lowest masses, including the halo PN population. Based upon spatially-resolved, long-slit, echelle spectroscopy drawn from the San Pedro M\'artir Kinematic Catalogue of PNe (L\'opez et al. 2012), we characterize the kinematics of these PNe measuring their global expansion velocities based upon the largest sample used to date for this purpose. We find kinematics that follow the trends observed and predicted in other studies, but also find that most of the PNe studied here tend to have expansion velocities less than 20 km/s in all of the emission lines considered. The low expansion velocities that we observe in this sample of low metallicity planetary nebulae with low mass progenitors are most likely a consequence of a weak central star wind driving the kinematics of the nebular shell. This study complements previous results (Pereyra et al. 2013, and references therein) that link the expansion velocities of the PN shells with the characteristics of the central star., Comment: 26 Pages, 5 Figures, 3 Tables. Accepted for publication in The Astronomical Journal on 14 Dec 2015

The Reionization And Transient Infra,.Red (RATIR) camera has been built for rapid Gamma,.Ray Burst (GRE) followup and will provide simultaneous optical and infrared photometric capabilities. The infrared portion of this camera incorporates two Teledyne HgCdTe HAWAII-2RG detectors, controlled by Teledyne's SIDECAR ASICs. While other ground-based systems have used the SIDECAR before, this system also utilizes Teledyne's JADE2 interface card and IDE development environment. Together, this setup comprises Teledyne's Development Kit, which is a bundled solution that can be efficiently integrated into future ground-based systems. In this presentation, we characterize the system's read noise, dark current, and conversion gain.

The Reionization And Transients InfraRed (RATIR) camera has been built for rapid Gamma-Ray Burst (GRB) followup and will provide quasi-simultaneous imaging in ugri ZY JH . The optical component uses two 2048 × 2048 pixel Finger Lakes Imaging ProLine detectors, one optimized for the SDSS u, g , and r bands and one optimized for the SDSS i band. The infrared portion incorporates two 2048 × 2048 pixel Teledyne HgCdTe HAWAII-2RG detectors, one with a 1.7-micron cutoff and one with a 2.5-micron cutoff. The infrared detectors are controlled by Teledyne's SIDECAR (System for Image Digitization Enhancement Control And Retrieval) ASICs (Application Specific Integrated Circuits). While other ground-based systems have used the SIDECAR before, this system also utilizes Teledyne's JADE2 (JWST ASIC Drive Electronics) interface card and IDE (Integrated Development Environment). Here we present a summary of the software developed to interface the RATIR detectors with Remote Telescope System, 2nd Version (RTS2) software. RTS2 is an integrated open source package for remote observatory control under the Linux operating system and will autonomously coordinate observatory dome, telescope pointing, detector, filter wheel, focus stage, and dewar vacuum compressor operations. Where necessary we have developed custom interfaces between RTS2 and RATIR hardware, most notably for cryogenic focus stage motor drivers and temperature controllers. All detector and hardware interface software developed for RATIR is freely available and open source as part of the RTS2 distribution.

The Reionization and Transients InfraRed camera (RATIR) is a simultaneous optical/NIR multi-band imaging camera which is 100% time-dedicated to the followup of Gamma-ray Bursts. The camera is mounted on the 1.5-meter Johnson telescope of the Mexican Observatorio Astron

In this article we present the mechanical design and the manufacturing of the support structure for the Reionization And Transients InfraRed (RATIR) camera. The instrument is mounted at the f/13 Cassegrain focus of the 1.5-meter Harold Johnson telescope of the Observatorio Astronomico Nacional at San Pedro Martir (OAN/SPM) in Mexico. We describe the high-level requirements and explain their translation to the mechanical specifications and requirements. We describe the structural finite-element analysis and the boundary conditions, loads, and general assumptions included in the simulations. We summarize the expected displacements, rotations and stresses. We present the optomechanical components and the elements used to attach the instrument to the telescope. Finally, we show the instrument installed on the telescope.

The Reionization And Transients Infra-Red (RATIR) camera is intended for robotic operation on the 1.5-meter Harold Johnson telescope of the Observatorio Astronomico Nacional on the Sierra de San Pedro Martir, Baja California, Mexico. This paper describes the work we have carried out to successfully automate the telescope and prepare it for RATIR. One novelty is our use of real-time absolute astrometry from the finder telescopes to point and guide the main telescope.

The Transneptunian Automated Occultation Survey (TAOS II) will aim to detect occultations of stars by small ( 1 km diameter) objects in the Solar System and beyond. Such events are very rare (< 10−3 events per star per year) and short in duration ( 200 ms), so many stars must be monitored at a high readout cadence. TAOS II will operate three 1.3 meter telescopes at the Observatorio Astron´omico Nacional at San Pedro Martir in Baja California, Mexico. With a 2.3 square degree field of view and a high speed camera comprising CMOS imagers, the survey will monitor 10,000 stars simultaneously with all three telescopes at a readout cadence of 20 Hz.

The brightest planetary nebulae achieve similar maximum luminosities, have similar ratios of chemcial abundances, and apparently share similar kinematics in all galaxies. These similarities, however, are not necessarily expected theoretically and appear to hide important evolutionary differences. As predicted theoretically, metallicity appears to affect nebular kinematics, if subtly, and there is a clear variation with evolutionary stage. To the extent that it can be investigated, the internal kinematics for galactic and extragalactic planetary nebulae are similar. The extragalactic planetary nebulae for which kinematic data exist, though, probably pertain to a small range of progenitor masses, so there may still be much left to learn, particularly concerning the kinematics of planetary nebulae that descend from the more massive progenitors., Comment: Invited Review, IAU Symp. 283, Planetary Nebulae: An Eye to the Future

We present an extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN), NGC 7026. We acquired ten spectra using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the 3-dimensional visualization and kinematic program, SHAPE, and using HST images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. NGC 7026 exhibits remarkable symmetry consisting of three lobe-pairs and four sets of knots, all symmetrical about the nucleus and displaying a conical outflow. Comparing the 3-D structure of this nebula to recent, XMM-Newton X-ray observations, we investigate the extended X-ray emission in relation to the nebular structure. We find that the X-ray emission, while confined to the closed, northern lobes of this PN, shows an abrupt termination in the middle of the SE lobe, which our long slit data shows to be open. This is where the shocked, fast wind seems to be escaping the interior of the nebula and the X-ray emission rapidly cools in this region., Comment: 7 pages, 5 figures, accepted for publication in the Astronomical Journal

SUPERNOVA 1993J is one of the closest supernovae discovered this century, allowing observations with very high linear resolution. Radio emission from the supernova became visible within days of the first optical peak, and has remained strong, making this an ideal source for very-long-baseline interferometry (VLBI) investigations1–7. Here we report the results of a series of VLBI observations, made from one to three months after the supernova explosion. We find that the supernova is circularly symmetric, which is somewhat surprising in view of suggestions that the progenitor was a member of a binary system8,9, and the asymmetry implied by optical observations10. The supernova shows no sign of deceleration, and the expansion velocities that we estimate from the VLBI measurements are consistent with the maximum optical line velocities11, suggesting that the radio emission indeed arises from the shock front, where the ejecta are hitting the gas that surrounded the progenitor star. We combine the angular expansion rate determined by the VLBI data with the optically derived expansion speed to estimate a distance to M81 of 4.0 ± 0.6 Mpc, consistent with the value obtained from measurements of Cepheid variables in M81, 3.63 ±0.34 Mpc (ref. 12).

RATIR (The Reionization and Transients Infrared Camera/Telescope) is an optical infrared camera in the 1.5 m telescope in the Mexican National Astronomical Observatory, OAN, in San Pedro Martir, Baja California. The primary goal of RATIR is to remotely observe Gamma Ray Bursts as detected by the SWIFT satellite. This document describes the problem definition, the mechanical calculations, the conceptual design, the finite element analysis, the different configurations proposed and the mechanical performance of the main Support Structure and Dichroic Mounts for RATIR.

We study the line widths in the [\ion{O}{3}]$\lambda$5007 and H$\alpha$ lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astron\'omico Nacional in the Sierra San Pedro M\'artir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high H$\beta$ luminosities, but [\ion{O}{3}]$\lambda 5007/\mathrm H\beta < 3$. The second sample comprises objects late in their evolution, with \ion{He}{2} $\lambda 4686/\mathrm H\beta > 0.5$. These planetary nebulae represent evolutionary phases preceeding and following those of the objects studied by Richer et al. (2008). Our sample of planetary nebulae with weak [\ion{O}{3}]$\lambda$5007 has a line width distribution similar to that of the expansion velocities of the envelopes of AGB stars, and shifted to systematically lower values as compared to the less evolved objects studied by Richer et al. (2008). The sample with strong \ion{He}{2} $\lambda 4686$ has a line width distribution indistinguishable from that of the more evolved objects from Richer et al. (2008), but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of Richer et al. (2008) form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star., Comment: accepted for publication in the Astrophysical Journal

We present a detailed investigation of SBS1150+599A, a close binary star hosted by the planetary nebula PN G135.9+55.9 (TS01, Stasinska et al, 2009). The nebula, located in the Galactic halo, is the most oxygen-poor one known to date and is the only one known to harbor a double degenerate core. We present XMM-Newton observations of this object, which allowed the detection of the previously invisible component of the binary core, whose existence was inferred so far only from radial velocity and photometric variations. The parameters of the binary system were deduced from a wealth of information via three independent routes using the spectral energy distribution (from the infrared to X-rays), the light and radial velocity curves, and a detailed model atmosphere fitting of the stellar absorption features of the optical/UV component. We find that the cool component must have a mass of 0.54+/-0.2 Msun, an average effective temperature, Teff, of 58000+/-3000 K, a mean radius of 0.43+/-0.3 Rsun, a gravity log g=5.0+/-0.3, and that it nearly fills its Roche lobe. Its surface elemental abundances are found to be: 12 + log He/H = 10.95+/-0.04 dex, 12 + log C/H = 7.20+/-0.3 dex, 12 + log N/H < 6.92 and 12 + log O/H < 6.80, in overall agreement with the chemical composition of the planetary nebula. The hot component has Teff = 160-180 kK, a luminosity of about ~10e4 Lsun and a radius slightly larger than that of a white dwarf. It is probably bloated and heated as a result of intense accretion and nuclear burning on its surface in the past. The total mass of the binary system is very close to Chandrasekhar limit. This makes TS01 one of the best type Ia supernova progenitor candidates. We propose two possible scenarios for the evolution of the system up to its present stage., Accepted for publication in Ap.J., 25 pages, 17 figures

NGC 6337 is a member of the rare group of planetary nebulae where a close binary nucleus has been identified. The nebula's morphology and emission line profiles are both unusual, particularly the latter. We present a thorough mapping of spatially resolved, long-slit echelle spectra obtained over the nebula that allows a detailed characterization of its complex kinematics. This information, together with narrowband imagery, is used to produce a three-dimensional (3D) model of the nebula using the code SHAPE. The D model yields a slowly expanding toroid with large density fluctuations in its periphery that are observed as cometary knots. A system of bipolar expanding caps of low ionization is located outside the toroid. In addition, an extended high velocity and tenuous bipolar collimated outflow is found emerging from the core and sharply bending in opposite directions, a behavior that cannot be accounted for by pure magnetic launching and collimation unless the source of the outflow is precessing or rotating, as could be expected from a close binary nucleus.

We present a systematic study of line widths in the [\ion{O}{3}]$\lambda$5007 and H$\alpha$ lines for a sample of 86 planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the \facility{Observatorio Astron\'omico Nacional in the Sierra San Pedro M\'artir (OAN-SPM)} using the Manchester Echelle Spectrograph. The planetary nebulae were selected with the intention of simulating samples of bright extragalactic planetary nebulae. We separate the planetary nebulae into two samples containing cooler and hotter central stars, defined by the absence or presence, respectively, of the \ion{He}{2} $\lambda$6560 line in the H$\alpha$ spectra. This division separates samples of younger and more evolved planetary nebulae. The sample of planetary nebulae with hotter central stars has systematically larger line widths, larger radii, lower electron densities, and lower H$\beta$ luminosities. The distributions of these parameters in the two samples all differ at significance levels exceeding 99%. These differences are all in agreement with the expectations from hydrodynamical models, but for the first time confirmed for a homogeneous and statistically significant sample of galactic planetary nebulae. We interpret these differences as evidence for the acceleration of the nebular shells during the early evolution of these intrinsically bright planetary nebulae. As is the case for planetary nebulae in the Magellanic Clouds, the acceleration of the nebular shells appears to be the direct result of the evolution of the central stars., Comment: accepted for publication in Astrophysical Journal

The central star of this nebula has an observed intense magnetic field and the fast wind is no longer present, indicating that a back flow process has probably developed. Long-slit, spatially resolved echelle spectra have been obtained across the main body of NGC 1360 and over its system of bipolar jets. Deep images of the knotty structures of the jets have also been obtained. The data allow a detailed study of the structure and kinematics of this object and the results are modeled considering the effects of a magnetic collimation process in the development of the nebula and then switching off the fast stellar wind to follow its evolution to its current state. The model is able to successfully reproduce many of the key features of NGC 1360 under these premises., Comment: 16 pages, 7 figures. ApJ in press

Recent studies of the near-infrared (NIR) properties of dwarf irregular galaxies (dIs) and blue compact dwarfs (BCDs) have provided improved estimates for the NIR luminosity of old stellar populations in these galaxies. These can be used to derive gas fractions, and thereby to evaluate how BCDs have evolved with respect to dIs. Oxygen abundances have been derived for four BCDs in the Virgo Cluster from a run at Gemini-North in 2003. Combining these new abundances with published values, we study the correlations among the metallicity, Ks luminosity, gas mass, baryonic mass, and gas fraction. Within errors, the two types of dwarfs appear to share a common relation between the oxygen abundance and the luminosity in Ks. The correlation between metallicity and the gas fraction is the same for BCDs as for dIs, indicating that BCD evolution has been similar to dIs. Since dIs appear to have evolved as isolated systems, the BCD bursts are unlikely to be a consequence of gas infall or merging., Accepted in AJ (Aug 2007)

Based upon the capabilities that are likely to be available from space and terrestrial observatories around 2015-2020 and the traditional interests of the Mexican astronomical community, I propose that the narrow- field telescope (NFT) be dedicated to high resolution spectroscopy covering wavelengths from the optical to the mid-infrared and adaptive optics imaging and spectroscopy (medium to high spectral resolution) in the near-infrared. These capabilities would permit studying the processes responsible for galaxy evolution after the epoch of mass assembly: the development of galactic structure, star formation, stellar structure and mass distributions, the kinematics and chemical composition of stars and the interstellar medium (ISM)

CK Vul is classified as, amongst others, the slowest known nova, a hibernating nova, or a very late thermal pulse object. Following its eruption in AD 1670, the star remained visible for 2 years. A 15-arcsec nebula was discovered in the 1980's, but the star itself has not been detected since the eruption. We here present radio images which reveal an 0.1-arcsec radio source with a flux of 1.5 mJy at 5 GHz. Deep Halpha images show a bipolar nebula with a longest extension of 70 arcsec, with the previously known compact nebula at its waist. The emission-line ratios show that the gas is shock-ionized, at velocities >100 km/s. Dust emission yields an envelope mass of ~0.05 Msun. Echelle spectra indicate outflow velocities up to 360 km/s. From a comparison of images obtained in 1991 and 2004 we find evidence for expansion of the nebula, consistent with an origin in the 1670 explosion; the measured expansion is centred on the radio source. No optical or infrared counterpart is found at the position of the radio source. The radio emission is interpreted as thermal free-free emission from gas with Tel ~ 10000 K. The radio source may be due to a remnant circumbinary disk, similar to those seen in some binary post-AGB stars. We discuss possible classifications of this unique outburst, including that of a sub-Chandrasekhar mass supernova, a nova eruption on a cool, low-mass white dwarf, or a thermal pulse induced by accretion from a circumbinary disk., 11 pages, 8 figures, published in MNRAS

Images obtained with the ESO VLT and FORS1 in [O III] 5007 on- and off-band as well as r_Gunn filters are analyzed to search for Planetary Nebula (PN) candidates in the dwarf irregular NGC 3109. In the continuum-subtracted [O III] 5007 on-band images, a large number of emission-line regions were detected. We describe the criteria employed in order to distinguish PN candidates from compact HII regions, finding that the sizes and the properties of the ionizing stars are the most unambiguous discriminators for separating the two classes. Based upon these criteria, we have found 20 PN candidates for which we present coordinates, nebular [O III] fluxes, and stellar magnitudes. The cumulative luminosity function for these PNe is discussed. A catalog of HII regions listing coordinates, nebular [O III] fluxes, stellar magnitudes and other characteristics is also presented. We find that HII regions are rather concentrated towards the disk of the galaxy, while PNe are found also above and below this structure, consistent with their belonging to an older stellar population., Comment: 8 pages, including 4 figures and 3 tables. Accepted in A&A. Replaced with the final version

We have searched for the emission from \fex and \fexiv that is expected from the gas emitting in diffuse X-rays in \bd, NGC 6543, NGC 7009, and NGC 7027. Neither line was detected in any object. Models that fit the X-ray spectra of these objects indicate that the \fex emission should be below our detection thresholds, but the predicted \fexiv emission exceeds our observed upper limits (one sigma) by factors of at least 3.5 to 12. The best explanation for the absence of \fexiv is that the X-ray plasma is depleted in iron. In principle, this result provides a clear chemical signature that may be used to determine the origin of the X-ray gas in either the nebular gas or the stellar wind. At present, though various lines of evidence appear to favour a nebular origin, the lack of atmospheric and nebular iron abundances in the objects studied here precludes a definitive conclusion., 23 pages, 4 figures

A sample of 34 dwarf irregular galaxies in the Local Volume, most nearer than 5 Mpc, has been imaged in the near-infrared (NIR) in J and K_s at CFHT in Hawaii and OAN-SPM in Mexico. In CFHT images, stars brighter than M_Ks=-7.5 were resolved. In most cases, the resolved population represents less than 5% of the total NIR flux in K_s. Although exponential at large radii, surface brightness profiles for the unresolved component flatten in the centres. They can be fitted across the whole range of radii with a hyperbolic secant (sech) defined as a function of two parameters: the central surface brightness and the scale length of the exponential. Isophotal, total, and fitted sech magnitudes have been calculated for all galaxies for which the unresolved component was detected, along with semimajor axes. The scale length and the semimajor axes correlate linearly with absolute isophotal magnitude. The same is true for colors and the central brightness. More luminous dIs tend to be larger, redder and brighter in the centre. The Tully-Fisher relation shows considerable scatter, but residuals are tied to surface brightness. The galaxies appear to lie in a ``fundamental plane'' defined by the sech absolute magnitude, the sech central surface brightness, and the HI line-width. The rms of residuals in M_K is only 0.4 mag, which implies that the plane can be used to evaluate the distances of star-forming dwarfs. Color-magnitude diagrams are presented for 29 galaxies in which stars were resolved. Most show a finger centered around J-K_s=1 mag. In some cases, there is a red tail extending to J-K_s=2.5 mag. (Abstract slightly shortened)., Accepted for publication in AJ. Full version including figures available at http://aries.phys.yorku.ca/~ovidiuv/Paper2.ps.gz

PN G135.9+55.9 is the most metal-poor PN known in our Galaxy. The central star resides in a short-period binary system with a compact component, probably a white dwarf. We describe new observations, which allowed us to determine the orbital period. The lower limit for the combined mass of both stars is close to the Chandrasekhar limit for white dwarfs, making this binary a possible progenitor of a supernova type Ia. The binary system must have recently emerged from a common envelope phase., Proceedings of the conference "Planetary Nebulae as Astronomical Tools", Gdansk, June/July 2005. To appear in AIP conference series

PN G135.9+55.9 is a compact, high excitation nebula that has been identified recently as the most oxygen-poor halo planetary nebula. Given its very peculiar characteristics and potential implications in the realms of stellar and Galactic evolution, additional data are needed to firmly establish its true nature and evolutionary history. Here we present the first long-slit, high spectral resolution observations of this object in the lines of H$\alpha$ and He II 4686. The position-velocity data are shown to be compatible with the interpretation of PN G135.9+55.9 being a halo planetary nebula. In both emission lines, we find the same two velocity components that characterize the kinematics as that of an expanding elliptical envelope. The kinematics is consistent with a prolate ellipsoidal model with axis ratio about 2:1, a radially decreasing emissivity distribution, a velocity distribution that is radial, and an expansion velocity of 30 km/s for the bulk of the material. To fit the observed line profiles, this model requires an asymmetric matter distribution, with the blue-shifted emission considerably stronger than the red-shifted emission. We find that the widths of the two velocity components are substantially wider than those expected due to thermal motions, but kinematic structure in the projected area covered by the slit appears to be sufficient to explain the line widths. The present data also rule out the possible presence of an accretion disk in the system that could have been responsible for a fraction of the H$\alpha$ flux, further supporting the planetary nebula nature of PN G135.9+55.9., Comment: accepted by Astronomy & Astrophysics

We present extensive new spectroscopy and imaging of PN G 135.9+55.9. We use these data as constraints to photoionization models to derive limits on the oxygen abundance. We find that PN G 135.9+55.9 has an oxygen abundance less than 1/50 of the solar value. Our models favour a value of 12 + \log O/H between 5.8 and 6.5 dex, confirming that PN G 135.9+55.9 is the most oxygen-poor planetary nebula known (Tovmassian et al. 2001). We also derive Ne/O = 0.5 +/- 0.3, S/O < 0.094, and Ar/O < 0.23. Although the value of Ne/O is nominally high, it need not imply that the progenitor of PN G 135.9+55.9 converted any of its initial oxygen abundance to neon. The helium abundance appears to be very low, He/H ~ 0.08, but a precise determination will require a much more detailed study. We find that Ha/Hb is lower than expected and perhaps variable, a finding for which we have no clear explanation., 14 pages, 7 figures, accepted for publication in Astronomy and Astrophysics

We present Fabry-Perot and multi-object spectroscopy of the galaxies in Hickson compact group 31 (HCG31). Based upon our H$\alpha$ data cubes, galaxies A and C are a single entity, showing no discontinuity in their kinematics. Kinematically, galaxy E is probably a component of the A+C complex; otherwise it is a recently detached fragment. Galaxy F appears, both kinematically and chemically, to have formed from material tidally removed from the A+C complex. Galaxies B and G are kinematically distinct from this complex. Galaxy Q also has a radial velocity compatible with group membership. Galaxies A, B, C, and F have nearly identical oxygen abundances, despite spanning a luminosity range of 5$ $mag. Galaxy B's oxygen abundance is normal for its luminosity, while galaxy F's abundance is that expected given its origin as a tidal fragment of the A+C complex. The oxygen abundances in galaxies A and C are also understandable if the A+C complex is a late-type spiral suffering strong gas inflow and star formation as a result of a tidal interaction. Given the kinematics of both the galaxies and the \ion{H}{i} gas, the oxygen abundances, and the position of galaxy G, we propose that an interaction of galaxy G with the A+C complex, rather than a merger of galaxies A and C, is a more complete explanation for the tidal features and other properties of HCG31. In this case, the A+C complex need not be a merger in progress, though this is not ruled out., Comment: accepted for publication by Astronomy & Astrophysics

We have observed WZ Sge with high resolution echelle spectroscopy during the 2001 superoutburst. The hot‐spot arising near the secondary star is again visible 15 days after its first detection. We have been able to measure its position as a function of orbital phase directly from individual spectra. We derive a a semiamplitude of Khs = 457 ± 16km s−1 and a systemic velocity of γ = 0 ± 14km s−1. We also show that the accretion disc has an ellipsoidal shape with a value around e = 0.75. Based on these facts we derive a phase shift of ΔΦ = −0.12 between the eclipse and the inferior conjuntion ephemeris. If this is the case, then the hot‐spot appears located at the trailing side of the red dwarf and must be the result of in‐falling material back to the donor star.

We present the most extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN), NGC 7026. Ten spectra were acquired using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the 3-dimensional visualization and kinematic program, Shape, and using HST images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. Knowledge of the 3-D structure of this nebula is relevant to understand the physics behind the extended X-ray emission in this object.

We present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, GRB 130215A/SN 2013ez, and GRB 130831A/SN 2013fu. For GRB 130215A/SN 2013ez, we also present optical spectroscopy at t − t0 = 16.1 d, which covers rest-frame 3000-6250 Å. Based on Fe ii λ5169 and Si ii λ6355, our spectrum indicates an unusually low expansion velocity of ~4000-6350 km s-1, the lowest ever measured for a GRB-SN. Additionally, we determined the brightness and shape of each accompanying SN relative to a template supernova (SN 1998bw), which were used to estimate the amount of nickel produced via nucleosynthesis during each explosion. We find that our derived nickel masses are typical of other GRB-SNe, and greater than those of SNe Ibc that are not associated with GRBs. For GRB 130831A/SN 2013fu, we used our well-sampled R-band light curve (LC) to estimate the amount of ejecta mass and the kinetic energy of the SN, finding that these too are similar to other GRB-SNe. For GRB 130215A, we took advantage of contemporaneous optical/NIR observations to construct an optical/NIR bolometric LC of the afterglow. We fit the bolometric LC with the millisecond magnetar model of Zhang & Mészáros (2001, ApJ, 552, L35), which considers dipole radiation as a source of energy injection to the forward shock powering the optical/NIR afterglow. Using this model we derive an initial spin period of P = 12 ms and a magnetic field of B = 1.1 × 1015 G, which are commensurate with those found for proposed magnetar central engines of other long-duration GRBs.

We present optical spectroscopy of H {\sc ii} regions in the Local Group galaxy IC 10 and $UBVR$ photometry of foreground stars in three fields towards this galaxy. From these data, we find that the foreground reddening due to the Milky Way is $E(B-V)=0.77\pm 0.07 \mathrm{mag}$. We find that IC 10 contains considerable internal dust, which qualitatively explains the variety of reddening values found by studies of its different stellar populations. Based upon our foreground reddening, IC 10 has intrinsic photometric properties like those of a blue compact dwarf galaxy, and not those of a dwarf irregular. This result is consistent with much evidence that IC 10 is in the throes of a starburst that began at least $10 \mathrm{Myr}$ ago. We also report the discovery of a new WR star in the H {\sc ii} region HL111c.

We present spectroscopy of planetary nebulae in M32 and in the bulge of M31 that we obtained with the MOS spectrograph at the Canada-France-Hawaii Telescope. Our sample includes 30 planetary nebulae in M31 and 9 planetary nebulae in M32. We also observed one H II region in the disk of M31. We detected [O III]$\lambda$4363 in 18 of the planetary nebulae, 4 in M32 and 14 in the bulge of M31. We use our line intensities to derive electron temperatures and oxygen abundances for the planetary nebulae., Comment: 17 pages, 12 figures, accepted by Astronomy & Astrophysics Supplement Series

We consider the possibility of using bright planetary nebulae to study the chemical evolution of their parent galaxies. In particular, we would like to use planetary nebulae as abundance probes in galaxies where star formation ended long ago, such as ellipticals or the bulges of spirals, and in which no other direct probes exist. However, if we are to use planetary nebulae to study the chemical evolution of their parent galaxies, we must relate the oxygen abundance in bright planetary nebulae to the oxygen abundance in the interstellar medium when star formation stopped. Obviously, only theoretical modelling can provide this information once star formation has stopped.

A flexible and extensible software package for analyzing two-dimensional and multi-object spectra of nebulae has been implemented within Microsoft Excel (version 5). From lists of calibrated fluxes (and errors) for lines in a series of spectra, the program first identifies transitions by referring to wavelengths generated from atomic data. Colour excesses can be computed from a reddening law and ratio of total to selective extinction of the user’s choice. Line fluxes can be corrected for stellar absorption and reddening and reported in a format suitable for publication. Temperatures, densities, ionic abundances, ionization correction factors, and total abundances can be computed. (The interface for the temperture/density calculation is shown below.) Emission coefficients for forbidden transitions are calculated using an adaptation of the FIVEL five-level atom routine (DeRobertis, 1987). As well, emission coefficients are supplied for an extensive set of recombination lines. The user has complete control over which spectral lines are used in an analysis — there are no pre-ordained methods. Abundance analyses can be performed using the physical conditions either measured or specified for each spectrum. Uncertainties are propagated throughout. The atomic data used in all of the calculations are easily updated or augmented by the user. Since the software is embedded in Microsoft Excel, graphical representations of the data are easily created, and extended analyses using the full functionality of the spreadsheet are easily implemented.

We present spatially- and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the European Southern Observatory's Very Large Telescope. Our objective is to analyze the kinematics of emission lines excited by recombination and collisions with electrons to determine whether similarities or differences could be useful in elucidating the well-known abundance discrepancy derived from them. We construct position-velocity maps for recombination, fluorescence, charge transfer, and collisionally-excited lines. We find a plasma component emitting in the C II, N II, O II, and Ne II recombination lines whose kinematics are discrepant: They are incompatible with the ionization structure derived from all other evidence and the kinematics derived from all of these lines are unexpectedly very similar. We find direct evidence for a recombination contribution to [N II] 5755. Once taken into account, the electron temperatures from [N II], [O III], and [Ne III] agree at a given position and velocity. The electron densities derived from [O II] and [Ar IV] are consistent with direct imaging and the distribution of hydrogen emission. The kinematics of the C II, N II, O II, and Ne II lines does not coincide with the kinematics of the [O III] and [Ne III] forbidden emission, indicating that there is an additional plasma component to the recombination emission that arises from a different volume from that giving rise to the forbidden emission from the parent ions within NGC 7009. Thus, the chemical abundances derived from either type of line are correct only for the plasma component from which they arise. Apart from [N II] 5755, we find no anomaly with the forbidden lines usually used to determine chemical abundances in ionized nebulae, so the abundances derived from them should be reliable for the medium from which they arise., accepted for publication in The Astrophysical Journal

Using theoretical models of the planetary nebula populations in galaxies, we investigate whether the current oxygen abundances in bright planetary nebulae can be used to predict the oxygen abundance that persisted in the interstellar medium when star formation stopped. In all galaxies, these models predict that a gap develops between the abundances observed in bright planetary nebulae and those that persisted in the interstellar medium when star formation stopped. This abundance gap depends primarily upon the oxygen abundance achieved in the interstellar medium when star formation stopped, though it also has some sensitivity to the history of star formation. The gap is always less than 0.5dex in these models. For the Milky Way, the predicted abundance gap, 0.14dex, is identical to that observed. The abundance gap magnifies the abundance-related differences between diffuse ellipticals and dwarf irregulars found by Richer & McCall (1995, ApJ, 445, 642). Diffuse ellipticals are confirmed to have larger oxygen abundances than similarly luminous dwarf irregulars, and to have larger [O/Fe] ratios than dwarf irregulars with the same oxygen abundance. The simplest explanation for both of these observations is that diffuse ellipticals formed on shorter time scales than dwarf irregulars. Given this difference in the history of star formation, diffuse ellipticals cannot be the faded remnants of dwarf irregulars.

PNG135.9+55.9 is a halo planetary nebula recently discovered among the objects from the Second Byurakan Survey. Based upon our first observations, a photoionization model analysis shows that the oxygen abundance in the nebula must be extremely low, probably 10-2–10-3 of the solar value. This finding has strong implications on our understanding of the formation of planetary nebulae, of mixing processes in the stellar progenitors and of the evolution of the Galactic halo.

The kinematics of the bipolar planetary nebulae Hb~5 and K 3-17 are investigated in detail by means of a comprehensive set of spatially resolved high spectral resolution, long-slit spectra. Both objects share particularly interesting characteristics, such as a complex filamentary, rosette-type nucleus, axial point-symmetry and very fast bipolar outflows. The kinematic information of Hb~5 is combined with {\it HST} imagery to construct a detailed 3D model of the nebula using the code SHAPE. The model shows that the large scale lobes are growing in a non-homologous way. The filamentary loops in the core are proven to actually be secondary lobes emerging from what appears to be a randomly punctured, dense, gaseous core and the material that forms the point symmetric structure flows within the lobes with a distinct kinematic pattern and its interaction with the lobes has had a shaping effect on them. Hb~5 and K~3-17 may represent a class of fast evolving planetary nebulae that will develop poly-polar characteristics once the nebular core evolves and expands., Comment: 19 pages, 8 figures. To appear in The Astrophysical Journal

The planetary nebula TS 01 (also called PN G 135.9+55.9 or SBS 1150+599A), with its record-holding low oxygen abundance and its double degenerate close binary core (period 3.9 h), is an exceptional object located in the Galactic halo. We have secured observational data in a complete wavelength range in order to pin down the abundances of half a dozen elements in the nebula. The abundances are obtained via detailed photoionization modelling taking into account all the observational constraints (including geometry and aperture effects) using the pseudo-3D photoionization code Cloudy_3D. The spectral energy distribution of the ionizing radiation is taken from appropriate model atmospheres. Both stellar components contribute to the ionization: the ``cool'' one provides the bulk of hydrogen ionization, and the ``hot'' one is responsible for the presence of the most highly charged ions, which explains why previous attempts to model the nebula experienced difficulties. The nebular abundances of C, N, O, and Ne are found to be respectively, 1/3.5, 1/4.2, 1/70, and 1/11 of the Solar value, with uncertainties of a factor 2. Thus the extreme O deficiency of this object is confirmed. The abundances of S and Ar are less than 1/30 of Solar. Standard models of stellar evolution and nucleosynthesis cannot explain the abundance pattern observed in the nebula. To obtain an extreme oxygen deficiency in a star whose progenitor has an initial mass of about 1 msun requires an additional mixing process, which can be induced by stellar rotation and/or by the presence of the close companion. We have computed a stellar model with initial mass of 1 msun, appropriate metallicity, and initial rotation of 100 kms, and find that rotation greatly improves the agreement between the predicted and observed abundances., to appear in Astronomy and Astrophysics