- ID:
- ivo://CDS.VizieR/J/AJ/128/1233
- Title:
- LkH{alpha} 101 and the young cluster in NGC 1579
- Short Name:
- J/AJ/128/1233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central region of the dark cloud L1482 is illuminated by LkH{alpha} 101, a heavily reddened (A_V_~10mag) high-luminosity (>=8x10^3^L_Sun_) star having an unusual emission-line spectrum plus a featureless continuum. About 35 much fainter (mostly between R=16 and >21) H{alpha} emitters have been found in the cloud. Their color-magnitude distribution suggests a median age of about 0.5Myr, with considerable dispersion. There are also at least five bright B-type stars in the cloud, presumably of about the same age; none show the peculiarities expected of HAeBe stars. Dereddened, their apparent V magnitudes lead to a distance of about 700pc. Radio observations suggest that the optical object LkH{alpha} 101 is in fact a hot star surrounded by a small H II region, both inside an optically thick dust shell.
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Search Results
- ID:
- ivo://nasa.heasarc/lkha101cxo
- Title:
- LkH-alpha 101 Star Formation Region Chandra X-Ray Point Source Catalog
- Short Name:
- LKHA101CXO
- Date:
- 11 Oct 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from a multi-wavelength study of a partially embedded region of star formation centered on the Herbig Be star LkH-alpha 101. Using two 40 ks Chandra observations, The authors have detected 213 X-ray sources in the ~ 17' x 17' ACIS-I field. They combine the X-ray data with Two Micron All Sky Survey (2MASS) near-IR observations and Spitzer Space Telescope (SST) IRAC and MIPS 24-micron observations to obtain a complete picture of the cluster. A total of 158 of the X-ray sources have infrared counterparts. Of these, the authors find nine protostars, 48 Class II objects, five transition objects, and 72 Class III objects. From the Spitzer data, they identify an additional 10 protostars, 53 Class II objects, and four transition disk candidates which are not detected by Chandra. (These objects are not included in this HEASARC table which contains the multi-wavelength data for only the 213 detected X-ray sources). The authors 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, they obtain independent estimates of cluster distance and the total cluster size - excluding protostars. The authors obtain consistent distance estimates of 510 (+100,-40) pc and a total cluster size of 255 (+50,-25) stars. They 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 1 Myr. The field was observed by Chandra on 2005 March 6 starting at 17:16 UT for 40.2 ks of total time and 39.6 ks of the so-called good time (Chandra ObsID 5429). It was observed again on 2005 March 8 starting at 17:43 UT for essentially the same duration (Chandra ObsID 5428). The ACIS was used in the nominal imaging array (chips I0-I3) which provides a field of view of approximately 17' x 17'. The aimpoint was at RA, Dec = 04:30:14.4, +35:16:22.2 (J2000.0) with a roll angle of 281 degrees. In addition, the S2 and S3 chips were active; however, the analysis of these data is not presented here. For purposes of point-source detection, the data from the two observations were merged into a single event list following established CIAO procedures to create a merged event list. To identify point sources, photons with energies below 300 eV and above 8.0 keV were filtered out from this merged event list. This excluded energies which generally lack a stellar contribution. By filtering the data as described, contributions from hard, non-stellar sources such as X-ray binaries and active galactic nuclei (AGNs) are attenuated, as is noise. A monochromatic exposure map was generated in the standard way using an energy of 1.49 keV which is a reasonable match to the expected peak energy of the stellar sources and the Chandra mirror transmission. The CIAO tool WavDetect was then run on a series of flux-corrected images binned by 1, 2, and 4 pixels. The output source lists were combined and this resulted in the detection of 231 sources. The authors defined false detections as any sources with < 4 net counts or any sources more than 5' off-axis with < 7 net counts. By this definition, 18 of the 231 detections were rejected as false detections. A post facto check confirmed that none of these (spurious) sources had an infrared counterpart. This table was created by the HEASARC in July 2010 based on the versions of Tables 1, 2, 3, 7 and 9 from the paper which were obtained from the electronic ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+A/433/117
- Title:
- L- & M-band imaging of the Galactic Center
- Short Name:
- J/A+A/433/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric data of the sources detected in NAOS/CONICA H- and K-band (1.6 and 2.1{mu}m) and ISAAC L- and M-band (3.8 and 4.7{mu}m) images of the Galactic Center, obtained in May and August 2002, are presented. For each source, name (if relevant), position offset, H-, K-, L- and M-band magnitude (if available) and observed colors (H-K, K-L and L-M) are given. The position zero-point is RA = 17:45:40.26, DE = -29:00:29.91 (IRS 16NE) in the J2000 system, with an offset of 2.83" (RA) and -0.91" (DE) from Sgr A*. The total photometric accuracy is +/-0.25mag in H- and K-band, +/-0.15mag in L- and M-band, positional accuracy is +/-0.09".
8054. LMC A-F supergiants
- ID:
- ivo://CDS.VizieR/J/A+AS/24/35
- Title:
- LMC A-F supergiants
- Short Name:
- J/A+AS/24/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey for A-F type supergiants in the Large Magellanic Cloud has been carried out using UV objective prism plates. 890 objects were detected and their spectral types, luminosity classes, magnitudes, and precise positions determined. The survey is practically complete to m_pg_=12.5 and extends for certain types of stars to m_pg_=14. It is found that the spatial distribution of the A-F supergiants is not correlated with the distribution of the gas and OB stars of the cloud. This is evidence in support of the tentative identification by Stock and Wroblewski of early-type galactic supergiants well off the plane. Several other implications of this result are also discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/348/98
- Title:
- LMC AGB stars IRAS fluxes
- Short Name:
- J/ApJ/348/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for optically obscured asymptotic giant branch (AGB) stars in the Large Magellanic Cloud (LMC), combining data obtained using the IRAS satellite with near-infrared photographic plate material of a 15deg^2^ region in the northern LMC. Of the 156 IRAS sources that are detected either in separate cross-scans or in more than one passband, 63 have [12-25] colors consistent with their being either stellar photospheres or circumstellar dust shells. Seventeen of these we identify with bright (I_c_<9) foreground stars in our own Galaxy, while a further 17 are associated with red supergiants in the LMC. Of the remaining stars, no more than five are likely to be optically visible AGB stars, while the rest have no obvious optical counterpart. This immediately rules out the presence of sufficient high-luminosity "cocoon" stars to explain the observed deficit of several hundred luminous (M_bol_<-6) AGB stars between the predictions of standard models of AGB evolution and the observed luminosity function. It remains possible that most of the unidentified sources are dusty AGB stars, evolving through a phase of enhanced mass loss toward becoming planetary nebulae. We infer bolometric magnitudes as low as M_bol_~-5 for these sources and suggest that this phase can be triggered at low luminosities, truncating AGB evolution and leading to the observed scarcity of asymptotic giant branch stars with bolometric magnitudes brighter than -6.0mag.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/59
- Title:
- LMC and Cen A 1.3-10GHz polarization behavior
- Short Name:
- J/ApJ/825/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a broadband polarization analysis of 36 discrete polarized radio sources over a very broad, densely sampled frequency band. Our sample was selected on the basis of polarization behavior apparent in narrowband archival data at 1.4GHz: half the sample shows complicated frequency-dependent polarization behavior (i.e., Faraday complexity) at these frequencies, while half shows comparatively simple behavior (i.e., they appear Faraday simple). We re-observed the sample using the Australia Telescope Compact Array in full polarization, with 6GHz of densely sampled frequency coverage spanning 1.3-10GHz. We have devised a general polarization modeling technique that allows us to identify multiple polarized emission components in a source, and to characterize their properties. We detect Faraday complex behavior in almost every source in our sample. Several sources exhibit particularly remarkable polarization behavior. By comparing our new and archival data, we have identified temporal variability in the broadband integrated polarization spectra of some sources. In a number of cases, the characteristics of the polarized emission components, including the range of Faraday depths over which they emit, their temporal variability, spectral index, and the linear extent of the source, allow us to argue that the spectropolarimetric data encode information about the magneto-ionic environment of active galactic nuclei themselves. Furthermore, the data place direct constraints on the geometry and magneto-ionic structure of this material. We discuss the consequences of restricted frequency bands on the detection and interpretation of polarization structures, and the implications for upcoming spectropolarimetric surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/2307
- Title:
- LMC anomalous Cepheid Ks light curves
- Short Name:
- J/MNRAS/437/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA near-infrared YJKs survey of the Magellanic Clouds System (VMC, PI M.-R. L. Cioni) is collecting deep Ks-band time-series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper, we present for the first time Ks-band light curves for anomalous Cepheid (AC) variables. In particular, we have analysed a sample of 48 Large Magellanic Cloud ACs, for which identification and optical magnitudes were obtained from the OGLE III and IV catalogues. The VMC Ks-band light curves for ACs are well sampled, with the number of epochs ranging from 8 to 16, and allowing us to obtain very precise mean Ks magnitudes with errors on average of the order of 0.01mag. The <Ks> values were used to build the first period-luminosity and period-Wesenheit relations in the near-infrared for fundamental mode and first overtone ACs. At the same time we exploited the optical (V, I) OGLE data to build accurate period-luminosity, period-luminosity-colour and period-Wesenheit relations both for fundamental mode and first overtone ACs. For the first time, these relations were derived from a sample of pulsators which uniformly cover the whole AC instability strip. The application of the optical period-Wesenheit relation to a sample of dwarf galaxies hosting a significant population of ACs revealed that this relation is a valuable tool for deriving distances within the Local Group. Due to its lower dispersion, we expect the Ks period-Wesenheit relations first derived in this paper to represent a valuable tool for measuring accurate distances to galaxies hosting ACs when more data in near-infrared filters become available.
8058. LMC bar star clusters
- ID:
- ivo://CDS.VizieR/J/A+A/606/A21
- Title:
- LMC bar star clusters
- Short Name:
- J/A+A/606/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results on star clusters located in the South-Eastern half of the Large Magellanic (LMC) bar fromWashington CT1 photometry. Using appropriate kernel density estimators we detected 73 star cluster candidates, three of which do not show any detectable trace of star cluster sequences in their colour-magnitude diagrams (CMDs).We did not detect other 38 previously catalogued clusters, which could not be recognized when visually inspecting the C and T1 images either; the distribution of stars in their respective fields do not resemble that of an stellar aggregate. They represent ~33 per cent of all catalogued objects located within the analysed LMC bar field. From matching theoretical isochrones to the cluster CMDs cleaned from field star contamination, we derived ages in the range 7.2<log(t[yr^-1^])<10.1. As far as we are aware, this is the first time homogeneous age estimates based on resolved stellar photometry are obtained for most of the studied clusters. We built the cluster frequency (CF) for the surveyed area, and found that the major star cluster formation activity has taken place during the period log(t[yr^-1^])~8.0-9.0. Since ~100Myr ago, clusters have been formed during few bursting formation episodes. When comparing the observed CF to that recovered from the star formation rate we found noticeable differences, which suggests that field star and star cluster formation histories could have been significantly different.
- ID:
- ivo://CDS.VizieR/J/AJ/154/102
- Title:
- LMC blue supergiants spectroscopic observations
- Short Name:
- J/AJ/154/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-quality spectra of 90 blue supergiant stars in the Large Magellanic Cloud are analyzed with respect to effective temperature, gravity, metallicity, reddening, extinction, and extinction law. An average metallicity, based on Fe and Mg abundances, relative to the Sun of [Z]=-0.35+/-0.09 dex is obtained. The reddening distribution peaks at E(B-V)=0.08 mag, but significantly larger values are also encountered. A wide distribution of the ratio of extinction to reddening is found ranging from R_V_=2 to 6. The results are used to investigate the blue supergiant relationship between flux-weighted gravity, g_F_=g/T_eff_^4^, and absolute bolometric magnitude M_bol_. The existence of a tight relationship, the Flux-weighted Gravity-Luminosity Relationship (FGLR), is confirmed. However, in contrast to previous work, the observations reveal that the FGLR is divided into two parts with a different slope. For flux-weighted gravities larger than 1.30 dex, the slope is similar to that found in previous work, but the relationship becomes significantly steeper for smaller values of the flux-weighted gravity. A new calibration of the FGLR for extragalactic distance determinations is provided.
- ID:
- ivo://CDS.VizieR/J/AJ/124/2039
- Title:
- LMC Blue variable stars from MACHO
- Short Name:
- J/AJ/124/2039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric properties of 1280 blue variable stars within the Large Megallanic Cloud. Photometry is derived from the MACHO database. The light curves of the sample exhibit a variety of quasi-periodic and aperiodic outburst behavior. A characteristic feature of the photometric variation is that the objects are reddest when at maximum outburst. A subset of 102 objects were examined spectroscopically. Within this subset, 91% exhibited Balmer emission in at least one epoch, in some cases with spectacular spectral variability. The variability observed in the sample is consistent with the establishment and maintenance of the Be phenomenon.