- ID:
- ivo://CDS.VizieR/J/ApJ/417/209
- Title:
- Faint planetary nebulae in Magellanic Clouds
- Short Name:
- J/ApJ/417/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accuracy of spectrophotometry for Magellanic Cloud planetary nebulae is limited by a number of physical effects and operational difficulties: atmospheric dispersion, wavelength-dependent seeing, pointing and guiding errors, and a background of numerous stars and diffuse emission. We describe procedures to minimize the impact of some of these. We then compare our results for both bright and faint objects with published values. There are a few exceptional cases (e.g., LMC 89), but generally we find that bright planetary nebulae in the Clouds have been observed with high accuracy. On the other hand, observations of the faint sample from Jacoby (1980ApJS...42....1J) suffer seriously from many of these effects. We also compare published {lambda}5007 photometry with new CCD photometry for nine faint planetary nebulae. We find the photographic photometry presented by Jacoby (1980ApJS...42....1J) to be accurate to 0.26mag. Fluxes for the fainter objects that are derived from spectrophotometry (Boroson & Liebert, 1989ApJ...339..844B) are found to be less reliable. In comparison, spectrophotometry using the observational techniques presented in this paper provides reliable absolute fluxes. With these improved observations, we review the correlations presented by Kaler & Jacoby (1990ApJ...362..491K, 1991ApJ...382..134K) between abundance ratios and central star mass. The new results fit our earlier correlation for N/O, strengthen that for He/H, and change little about those for C/O and O/H.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1265
- Title:
- Faint red galaxies in Coma cluster spectroscopy
- Short Name:
- J/MNRAS/392/1265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the stellar populations in a sample of 89 faint red galaxies in the Coma cluster, using high signal-to-noise ratio (S/N) spectroscopy from the 6.5-m MMT. Our sample is drawn from two 1{deg} fields, one centred on the cluster core and the other located 1{deg} to the south-west of the cluster centre. The target galaxies are mostly 2-4mag fainter than M*; galaxies with these luminosities have been previously studied only using small samples, or at low S/N. For a comparison sample we use published high-S/N data for red-sequence galaxies in the Shapley supercluster. We use state-of-the-art stellar population models (by R. Schiavon, Cat. <J/ApJS/171/146>) to interpret the absorption-line indices and infer the single-burst-equivalent age and metallicity (Fe/H) for each galaxy, as well as the abundances of the light elements Mg, Ca, C and N.
- ID:
- ivo://CDS.VizieR/J/AJ/158/157
- Title:
- Fairly bright slow rotators chemical compositions
- Short Name:
- J/AJ/158/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a detailed abundance study of the fairly bright slow rotators HD 30085 (A0 IV), HD 30963 (B9 III), and HD 174567 (A0 V), hitherto reported as normal stars and the sharp-lined {chi} Lupi A (B9 IV HgMn). In the spectra of HD 30085 and HD 30963, the Hg II line at 3984 {AA} is conspicuous and numerous lines of silicon, manganese, chromium, titanium, iron, strontium, yttrium, and zirconium appear to be strong absorbers. A comparison of the mean spectra of HD 30085 and HD 30963 with a grid of synthetic spectra for selected unblended lines having reliable updated atomic data reveals large overabundances of phosphorus, titanium, chromium, manganese, strontium, yttrium, zirconium, barium, platinum, and mercury, and underabundances of helium, magnesium, scandium, and nickel. The surface abundances of {chi} Lupi A have been rederived on the same effective temperature scale and using the same atomic data for consistency and comparison for HD 30085 and HD 30963. For HD 174567, milder deficiencies and excesses are found. The abundances of sodium, magnesium, and calcium have been corrected for non-LTE (NLTE) effects. The effective temperatures, surface gravities, low projected rotational velocities, and the peculiar abundance patterns of HD 30085 and HD 30963 show that these stars are two new HgMn stars and should be reclassified as such. HD 174567 is most likely a new marginally chemically peculiar star. A list of the identifications of lines absorbing more than 2% in the spectrum of HD 30085 is also provided.
- ID:
- ivo://CDS.VizieR/J/ApJ/405/94
- Title:
- Far-infrared emission from 5 galaxy clusters
- Short Name:
- J/ApJ/405/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed IRAS image data using a random position, multiple-aperture photometry method to study diffuse far-infrared emission for a sample of 56 clusters of galaxies at 60 and 100um. Five of the clusters in the sample exhibit excess far-infrared emission, but at low levels of significance. For A496 (Perseus) and MKW 1, this emission appears to be associated with a strong point source: in A2344, the observed excess is probably due to a foreground cirrus cloud. Two clusters, A262 and A2670, show evidence for extended diffuse emission. This emission is unlikely to be due to point sources associated with the clusters. In these two clusters, the diffuse emission shows evidence of being extended along the cluster's major axis. Far-infrared maps at 60 and 100um are presented for these five clusters. We find that contamination due to diffuse Galactic cirrus represents the major source of uncertainty in the measurement of far-infrared emission. The mean cluster fluxes for the sample as a whole are 44 and 107mJy for a 4' diameter aperture at 60 and 100um, respectively. The corresponding fluxes for a 10' diameter aperture are 138 and 253mJy at 60 and 100um. Photometry for the entire sample shows statistical evidence for excess emission at 60um associated with clusters in apertures 4' and 10' in diameter. This result is unlikely to be caused by random sampling errors. The flux distributions are analyzed for evidence that excess far-infrared radiation correlates with cluster environmental characteristics. Although we find evidence that poorer X-ray clusters are stronger far-infrared emitters, this result is tentative owing to the small sample sizes involved. The far-infrared luminosities, dust temperatures, and dust masses which these results imply are also presented. Finally, the origin and possible heating mechanism for dust in the intracluster medium is discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/18
- Title:
- Far-IR spectrum of ethylene oxide (CH_2_-O-CH_2_)
- Short Name:
- J/ApJ/753/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution Fourier Transform Infrared spectroscopy (FTIR) spectra of ethylene oxide (CH_2_-O-CH_2_) have been measured in the far-infrared region using synchrotron radiation. A total of 1182 lines between 15/cm (450GHz) and 73/cm (2.2THz) were assigned, with J_max_=64, expanding upon previous studies that had recorded spectra up to 12/cm, J_max_=49. All available data were co-fitted to provide greatly improved rotational constants for the ground vibrational state that are capable of predicting transitions up to 73/cm.
- ID:
- ivo://CDS.VizieR/J/A+A/250/370
- Title:
- Far-UV excess object survey
- Short Name:
- J/A+A/250/370
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical spectra have been obtained for a selection of objects included in a catalog of far ultraviolet bright, high galactic latitude objects detected with a balloon-borne survey telescope. The observed objects provide a sample of subdwarf O and B stars, white dwarfs, and binary systems including a hot sub-luminous member. Model atmospheres analysis of the sub-dwarf sample is used to determine the temperature, gravity, and helium to hydrogen ratio of the individual objects. A smooth distribution of objects is found on the gravity versus temperature diagram near the theoretical location of the extended horizontal branch. A break between the helium rich and helium poor objects occurs at 40000K. Suspected binary objects were found and analyzed to determine the temperature and gravity of the hot subluminous member in each system. The number of subdwarf stars contained in binaries is determined to be from 65% to 100%. The number versus ultraviolet magnitude distribution of the subdwarf B sample is modeled to obtain a midplane density of 3.3x10^-6^pc^-3^ and a population scale height of 240pc. The proportion of white dwarfs that experience the subdwarf phase of evolution is found to be 0.94%.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/17
- Title:
- Far-UV spectral atlas of O-type stars
- Short Name:
- J/ApJS/202/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present a spectral atlas covering the wavelength interval 930-1188{AA} for O2-O9.5 stars using Far-Ultraviolet Spectroscopic Explorer archival data. The stars selected for the atlas were drawn from three populations: Galactic main-sequence (classes III-V) stars, supergiants, and main-sequence stars in the Magellanic Clouds, which have low metallicities. For several of these stars, we have prepared FITS files comprised of pairs of merged spectra for user access via the Multimission Archive at Space Telescope (MAST). We chose spectra from the first population with spectral types O4, O5, O6, O7, O8, and O9.5 and used them to compile tables and figures with identifications of all possible atmospheric and interstellar medium lines in the region 949-1188{AA}. Our identified line totals for these six representative spectra are 821 (500), 992 (663), 1077 (749), 1178 (847), 1359 (1001), and 1798 (1392) lines, respectively, where the numbers in parentheses are the totals of lines formed in the atmospheres, according to spectral synthesis models. The total number of unique atmospheric identifications for the six main-sequence O-star template spectra is 1792, whereas the number of atmospheric lines in common to these spectra is 300. The number of identified lines decreases toward earlier types (increasing effective temperature), while the percentages of "missed" features (unknown lines not predicted from our spectral syntheses) drop from a high of 8% at type B0.2, from our recently published B-star far-UV atlas (Cat. J/ApJS/186/175), to 1%-3% for type O spectra. The percentages of overpredicted lines are similar, despite their being much higher for B-star spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/749/157
- Title:
- Far-UV spectra of Galactic corona sight lines
- Short Name:
- J/ApJ/749/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the properties of the transition temperature (T~10^5^K) gas in the Milky Way corona, based on the measurements of OVI, NV, CIV, SiIV, and FeIII absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60km/s. On average the integrated column densities are logN(OVI)=14.3, logN(NV)=13.5, logN(CIV)=14.2, logN(SiIV)=13.6, and logN(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor ~2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A126
- Title:
- Far-UV spectra of PN central stars
- Short Name:
- J/A+A/553/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The occurrence of stellar wind in the central star of a planetary nebula (CSPN) can be revealed by the presence of P Cygni profiles of high-excitation lines overimposed on its stellar continuum. We have examined the entire Far-Ultraviolet Spectroscopic Explorer FUSE archive and merged all useful spectroscopic observations of CSPNe to produce the highest quality spectra that can be used to assess the occurrence of stellar winds. Furthermore, the individual spectra of each CSPN have been compared to search for variability in the P Cygni profile. P Cygni profiles of high-excitation lines have been found in 44 CSPNe, with a clear correlation between the ionization potential of the lines and the effective temperature of the star.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/175
- Title:
- Far-UV spectroscopic atlas of B stars
- Short Name:
- J/ApJS/186/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed a detailed spectral atlas covering the wavelength region 930-1225{AA} for 10 sharp-lined B0-B9 stars near the main sequence. Most of the spectra we assembled are from the archives of the Far Ultraviolet Spectroscopic Explorer satellite, but for nine stars, wavelength coverage above 1188{AA} was taken from high-resolution International Ultraviolet Explorer or echelle Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra. To represent the tenth star at type B0.2V, we used the Copernicus atlas of tau Sco. We made extensive line identifications in the region 949-1225{AA} of all atomic features having published oscillator strengths at types B0, B2, and B8. These are provided as a supplementary data product-hence the term detailed atlas. Our list of found features totals 2288, 1612, and 2469 lines, respectively. We were able to identify 92%, 98%, and 98% of these features with known atomic transitions with varying degrees of certainty in these spectra. The remaining lines do not have published oscillator strengths. Photospheric lines account for 94%, 87%, and 91%, respectively, of all our identifications, with the remainder being due to interstellar (usually molecular H2) lines. We also discuss the numbers of lines with respect to the distributions of various ions for these three most studied spectral subtypes. A table is also given of 162 least blended lines that can be used as possible diagnostics of physical conditions in B star atmospheres.
