- ID:
- ivo://CDS.VizieR/J/A+A/439/265
- Title:
- Wolf-Rayet population in M83
- Short Name:
- J/A+A/439/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of non-nuclear regions containing Wolf-Rayet stars in the metal-rich spiral galaxy M 83 (NGC 5236). From a total of 283 candidate regions identified using He II {lambda}4686 imaging with VLT-FORS2, Multi Object Spectroscopy of 198 regions was carried out, confirming 132 WR sources. From this sub-sample, an exceptional content of ~1035+/-300 WR stars is inferred, with N(WC)/N(WN) ~ 1.2, continuing the trend to larger values at higher metallicity amongst Local Group galaxies, and greatly exceeding current evolutionary predictions at high metallicity.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/423/1029
- Title:
- XMM-Newton obs, in Cha I South
- Short Name:
- J/A+A/423/1029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a 30ks XMM-Newton observation of the central region of the Cha I star forming cloud. The field includes a substantial fraction of the known pre-main-sequence population of Cha I South, including all thirteen known very-low mass H{alpha} emitters. We detect two bona-fide brown dwarfs (spectral types M 7.5 and M 8) and seven H{alpha} emitting objects near the hydrogen burning mass limit, including six of seven earlier detections by ROSAT.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/21
- Title:
- XMM-Newton survey of local OVII absorbers
- Short Name:
- J/ApJS/217/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Highly ionized, z=0 metal absorption lines detected in the X-ray spectra of background active galactic nuclei (AGNs) provide an effective method to probe the hot (T~10^6^K) gas and its metal content in and around the Milky Way. We present an all-sky survey of the K_{alpha}_ transition of the local OVII absorption lines obtained by Voigt-profile fitting archival XMM-Newton observations. A total of 43 AGNs were selected, among which 12 are BL Lac-type AGNs, and the rest are Seyfert 1 galaxies. At above the 3{sigma} level the local OVII absorption lines were detected in 21 AGNs, among which 7 were newly discovered in this work. The sky covering fraction, defined as the ratio between the number of detections and the sample size, increases from about 40% for all targets to 100% for the brightest targets, suggesting a uniform distribution of the OVII absorbers. We correlate the line equivalent width with the Galactic coordinates and do not find any strong correlations between these quantities. Some AGNs have warm absorbers that may complicate the analysis of the local X-ray absorber since the recession velocity can be compensated by the outflow velocity, especially for nearby targets. We discuss the potential impact of warm absorbers on our analysis.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/L10
- Title:
- XO-2N and XO-2S equivalent widths
- Short Name:
- J/ApJ/801/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemical composition of exoplanet host stars is an important factor in understanding the formation and characteristics of their orbiting planets. The best example of this to date is the planet-metallicity correlation. Other proposed correlations are thus far less robust, in part due to uncertainty in the chemical history of stars pre- and post-planet formation. Binary host stars of similar type present an opportunity to isolate the effects of planets on host star abundances. Here we present a differential elemental abundance analysis of the XO-2 stellar binary, in which both G9 stars host giant planets, one of which is transiting. Building on our previous work, we report 16 elemental abundances and compare the {Delta}(XO-2N-XO-2S) values to elemental condensation temperatures. The {Delta}(N-S) values and slopes with condensation temperature resulting from four different pairs of stellar parameters are compared to explore the effects of changing the relative temperature and gravity of the stars. We find that most of the abundance differences between the stars depend on the chosen stellar parameters, but that Fe, Si, and potentially Ni are consistently enhanced in XO-2N regardless of the chosen stellar parameters. This study emphasizes the power of binary host star abundance analysis for probing the effects of giant planet formation, but also illustrates the potentially large uncertainties in abundance differences and slopes induced by changes in stellar temperature and gravity.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/13
- Title:
- XO-2S and XO-2N chemical composition
- Short Name:
- J/ApJ/808/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using high-quality spectra of the twin stars in the XO-2 binary system, we have detected significant differences in the chemical composition of their photospheres. The differences correlate strongly with the elements' dust condensation temperature. In XO-2N, volatiles are enhanced by about 0.015dex and refractories are overabundant by up to 0.090dex. On average, our error bar in relative abundance is 0.012dex. We present an early metal-depletion scenario in which the formation of the gas giant planets known to exist around these stars are responsible for a 0.015 dex offset in the abundances of all elements while 20M_{Earth}_ of non-detected rocky objects that formed around XO-2S explain the additional refractory-element difference. An alternative explanation involves the late accretion of at least 20M_{Earth}_of planet-like material by XO-2N, allegedly as a result of the migration of the hot Jupiter detected around that star. Dust cleansing by a nearby hot star as well as age or Galactic birthplace effects can be ruled out as valid explanations for this phenomenon.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/671
- Title:
- X-ray and IR emission from YSOs
- Short Name:
- J/ApJ/715/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a multiwavelength study of a partially embedded region of star formation centered on the Herbig Be star LkH{alpha} 101. Using two 40ks Chandra observations, we detect 213 X-ray sources in the ~17'x17' ACIS-I field. We combine the X-ray data with Two Micron All Sky Survey near-IR observations and Spitzer IRAC and MIPS 24um observations to obtain a complete picture of the cluster. A total of 158 of the X-ray sources have infrared counterparts. Of these, we find nine protostars, 48 Class II objects, five transition objects, and 72 Class III objects. From the Spitzer data we identify an additional 10 protostars, 53 Class II objects, and four transition disk candidates which are not detected by Chandra. We obtained optical spectra of a sample of both X-ray-detected and non-X-ray-detected objects. Combining the X-ray, Spitzer, and spectral data, we obtain independent estimates of cluster distance and the total cluster size -excluding protostars. We obtain consistent distance estimates of 510^+100^_-40_pc and a total cluster size of 255^+50^_-25_ stars. We find the Class II:III ratio is about 5:7 with some evidence that the Class III sources are spatially more dispersed. The cluster appears very young with three sites of active star formation and a median age of about 1Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/747/10
- Title:
- X-ray and multiwavelength properties of 11 WLQs
- Short Name:
- J/ApJ/747/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z=0.4-2.5. Our sample was selected from the Plotkin et al. catalog (2010, Cat. J/AJ/139/390) of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of >~5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/450
- Title:
- X-ray emission in Orion Nebula young stars
- Short Name:
- J/ApJS/160/450
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial distribution of X-ray-emitting plasma in a sample of young Orion Nebula Cluster stars by modulation of their X-ray light curves due to stellar rotation. The study, part of the Chandra Orion Ultradeep Project (COUP, Cat. <J/ApJS/160/319>), is made possible by the exceptional length of the observation: 10 days of ACIS integration during a time span of 13 days, yielding a total of 1616 detected sources in the 17'x17' field of view. We here focus on a subsample of 233 X-ray-bright stars with known rotational periods. We search for X-ray modulation using the Lomb Normalized Periodogram method.
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/5556
- Title:
- X-ray properties of 26 high-luminosity quasars
- Short Name:
- J/MNRAS/504/5556
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an investigation of the interdependence of the optical-to-X-ray spectral slope (aox), the HeII equivalent-width (EW), and the monochromatic luminosity at 2500{AA} (L2500). The values of {alpha}_ox_ and HeII EW are indicators of the strength/shape of the quasar ionizing continuum, from the ultraviolet (UV; 1500-2500{AA}), through the extreme ultraviolet (EUV;300-50{AA}), to the X-ray (2keV) regime. For this investigation, we measure the HeII EW of 206 radio-quiet quasars devoid of broad absorption lines that have high-quality spectral observations of the UV and 2keV X-rays. The sample spans wide redshift (z~0.13-3.5) and luminosity (logL_2500_~29.2-32.5erg/s/Hz) ranges. We recover the well-known {alpha}_ox_-L_2500_ and HeII EW-L_2500_ anti-correlations, and we find a similarly strong correlation between {alpha}_ox_ and HeII EW, and thus the overall spectral shape from the UV, through the EUV, to the X-ray regime is largely set by luminosity. A significant {alpha}_ox_-HeII EW correlation remains after removing the contribution of L_2500_ from each quantity, and thus the emission in the EUV and the X-rays are also directly tied. This set of relations is surprising, since the UV, EUV, and X-ray emission are expected to be formed in three physically distinct regions. Our results indicate the presence of a redshift-independent physical mechanism that couples the continuum emission from these three different regions, and thus controls the overall continuum shape from the UV to the X-ray regime.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/L11
- Title:
- X-ray properties of Seyfert 1 galaxies
- Short Name:
- J/ApJ/713/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, {Gamma}_2-10keV_, and the iron K{alpha} emission lines of narrow- and broad-line Seyfert 1 (NLS1 and BLS1) galaxies. We compile a flux-limited (f_2-10keV_>=1x10^-12^erg/s/cm^2^) sample including 114 radio-quiet objects, with the 2-10keV luminosity ranging from 10^41^ to 10^45^erg/s. 86 out of these 114 AGNs are included in the CAIXA catalogue (Bianchi et al. 2009, Cat. J/A+A/495/421). The redshift range of the present sample is z<0.37, with only seven objects having z>0.2.
