Search

Start Over Capability Type Simple Cone Search
2801. CH(G) index of SDSS evolved stars
ID:
ivo://CDS.VizieR/J/ApJ/765/156
Title:
CH(G) index of SDSS evolved stars
Short Name:
J/ApJ/765/156
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have measured the CH G band (CH(G)) index for evolved stars in the globular cluster M3 based on the Sloan Digital Sky Survey (SDSS) spectroscopic survey. It is found that there is a useful way to select red giant branch (RGB) stars from the contamination of other evolved stars such as asymptotic giant branch (AGB) and red horizontal branch (RHB) stars by using the CH(G) index versus (g-r)_0_ diagram if the metallicity is known from the spectra. When this diagram is applied to field giant stars with similar metallicity, we establish a calibration of CH(G)=1.625(g-r)_0_-1.174(g-r)^2^_0_-0.934. This method is confirmed by stars with [Fe/H]~-2.3 where spectra of member stars in globular clusters M15 and M92 are available in the SDSS database. We thus extend this kind of calibration to every individual metallicity bin ranging from [Fe/H]~-3.0 to [Fe/H]~0.0 by using field red giant stars with 0.4<=(g-r)_0_<=1.0. The metallicity-dependent calibrations give CH(G)=1.625(g-r)_0_-1.174(g-r)^2^_0_+0.060[Fe/H]-0.830 for -3.0<[Fe/H]<=-1.2 and CH(G)=0.953(g-r)_0_-0.655(g-r)^2^_0_+0.060[Fe/H]-0.650 for -1.2<[Fe/H]<0.0. The calibrations are valid for the SDSS spectroscopic data set, and they cannot be applied blindly to other data sets. With the two calibrations, a significant number of the contaminating stars (AGB and RHB stars) were excluded and thus a clear sample of red giant stars is obtained by selecting stars within +/-0.05mag of the calibration. The sample is published online and it is expected that this large and clean sample of RGB stars will provide new information on the formation and evolution of the Galaxy.
2802. ChIcAGO. I. Sample and initial results
ID:
ivo://CDS.VizieR/J/ApJS/212/13
Title:
ChIcAGO. I. Sample and initial results
Short Name:
J/ApJS/212/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the Chasing the Identification of ASCA Galactic Objects (ChIcAGO) survey, which is designed to identify the unknown X-ray sources discovered during the ASCA Galactic Plane Survey (AGPS). Little is known about most of the AGPS sources, especially those that emit primarily in hard X-rays (2-10keV) within the F_x_~10^-13^ to 10^-11^erg/cm2/s X-ray flux range. In ChIcAGO, the subarcsecond localization capabilities of Chandra have been combined with a detailed multiwavelength follow-up program, with the ultimate goal of classifying the >100 unidentified sources in the AGPS. Overall to date, 93 unidentified AGPS sources have been observed with Chandra as part of the ChIcAGO survey. A total of 253 X-ray point sources have been detected in these Chandra observations within 3' of the original ASCA positions. We have identified infrared and optical counterparts to the majority of these sources, using both new observations and catalogs from existing Galactic plane surveys. X-ray and infrared population statistics for the X-ray point sources detected in the Chandra observations reveal that the primary populations of Galactic plane X-ray sources that emit in the F_x_~10^-13^ to 10^-11^ erg/cm2/s flux range are active stellar coronae, massive stars with strong stellar winds that are possibly in colliding wind binaries, X-ray binaries, and magnetars. There is also another primary population that is still unidentified but, on the basis of its X-ray and infrared properties, likely comprises partly Galactic sources and partly active galactic nuclei.
2803. ChIcAGO Survey Chandra X-Ray Source Catalog
ID:
ivo://nasa.heasarc/chicagocxo
Title:
ChIcAGO Survey Chandra X-Ray Source Catalog
Short Name:
CHICAGOCXO
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from the &#39;Chasing the Identification of ASCA Galactic Objects&#39; (ChIcAGO) survey, which is designed to identify the unknown X-ray sources discovered during the ASCA Galactic Plane Survey (AGPS). Little is known about most of the AGPS sources, especially those that emit primarily in hard X-rays (2-10 keV) within the X-ray flux range from ~ 10&lt;sup&gt;-13&lt;/sup&gt; to 10&lt;sup&gt;-11&lt;/sup&gt; erg cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;. In ChIcAGO, the sub-arcsecond localization capabilities of Chandra have been combined with a detailed multi-wavelength follow-up program, with the ultimate goal of classifying the &gt; 100 unidentified sources in the AGPS. Overall to date, 93 unidentified AGPS sources have been observed with Chandra as part of the ChIcAGO survey. A total of 253 X-ray point sources have been detected in these Chandra observations within 3 arcminutes of the original ASCA positions. The authors have identified infrared and optical counterparts to the majority of these sources, using both new observations and catalogs from existing Galactic plane surveys. X-ray and infrared population statistics for the X-ray point sources detected in the Chandra observations reveal that the primary populations of Galactic plane X-ray sources that emit in the X-ray flux range from ~ 10&lt;sup&gt;-13&lt;/sup&gt; to 10&lt;sup&gt;-11&lt;/sup&gt; erg cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt; are active stellar coronae, massive stars with strong stellar winds that are possibly in colliding wind binaries, X-ray binaries, and magnetars. There is also another primary population that is still unidentified but, on the basis of its X-ray and infrared properties, likely comprises partly Galactic sources and partly active galactic nuclei. A total of 93 AGPS sources have been observed with Chandra as part of the ChIcAGO survey, of which 84 were imaged with ACIS-S and 9 were imaged with HRC-I. The ChIcAGO Chandra observations took place over a 3.5 yr period, from 2007 January to 2010 July. The Chandra exposure times ranged from ~ 1 to 10 ks. All the details of these Chandra observations are listed in Table 1 of the reference paper. The initial automated analysis of these Chandra observations was conducted using the ChIcAGO Multi-wavelength Analysis Pipeline (MAP), described in Section 2.2 of the reference paper. ChIcAGO MAP takes the ACIS-S or HRC-I Chandra observation of an AGPS source field and detects and analyzes all point sources within 3 arcminutes, equivalent to the largest likely position error, for the original AGPS source positions supplied by Sugizaki et al. (2001, ApJS, 134, 77). The authors then performed a more detailed X-ray analysis and counterpart study for those 74 sources with &gt; 20 X-ray counts, as such sources are approximately within the original AGPS sources X-ray flux range (see Sections 3.2 and 3.3 of the reference paper). Infrared and optical follow-up were primarily performed on those ChIcAGO sources having &gt; 20 X-ray counts. In order to determine which optical and infrared sources are counterparts to ChIcAGO sources, the authors used a technique similar to that described by Zhao et al. (2005, ApJS, 161, 429), using their Equation (11). If the separation between a ChIcAGO source&#39;s wavdetect position and its possible counterpart is less than the quadratic sum of their 3-sigma positional errors and the 3-sigma Chandra pointing error, then the X-ray and optical (or infrared) sources are likely to be associated. The 1-sigma positional errors for all sources in the 2MASS PSC and GLIMPSE catalogs are 0.1 arcseconds and 0.3 arcseconds, respectively. USNO B has an astrometric accuracy of &lt; 0.25 arcseconds. The authors have assumed that the error distributions of the Chandra observations, Chandra pointing, and USNO B Catalog are all Gaussian for the purposes of identifying possible counterparts to the ChIcAGO sources. This table was created by the HEASARC in June 2014 based on electronic versions of Tables 1, 2 and 12 from the reference paper which were obtained from the ApJS website. This is a service provided by NASA HEASARC .
2804. 3C293 high and low resolution maps
ID:
ivo://CDS.VizieR/J/A+A/658/A6
Title:
3C293 high and low resolution maps
Short Name:
J/A+A/658/A6
Date:
22 Feb 2022
Publisher:
CDS
Description:
Active galactic nuclei (AGNs) show episodic activity, which can be evident in galaxies that exhibit restarted radio jets. These restarted jets can interact with their environment, leaving signatures on the radio spectral energy distribution. Tracing these signatures is a powerful way to explore the life of radio galaxies. This requires resolved spectral index measurements over a broad frequency range including low frequencies. We present such a study for the radio galaxy 3C293, which has long been thought to be a restarted galaxy on the basis of its radio morphology. Using the International LOFAR telescope (ILT) we probed spatial scales as fine as ~0.2-arcsec at 144MHz, and to constrain the spectrum we combined these data with Multi-Element Radio Linked Interferometer Network (MERLIN) and Very Large Array (VLA) archival data at frequencies up to 8.4GHz that have a comparable resolution. In the inner lobes (~2kpc), we detect the presence of a spectral turnover that peaks at ~225MHz and is most likely caused by free-free absorption from the rich surrounding medium. We confirm that these inner lobes are part of a jet-dominated young radio source (spectral age ~0.17Myr), which is strongly interacting with the rich int <0.27Myr. The outer lobes (extending up to ~100kpc) have a spectral index of ~0.6-0.8 from 144-4850MHz with a remarkably uniform spatial distribution and only mild spectral curvature. We propose that intermittent fuelling and jet flow disruptions are powering the mechanisms that keep the spectral index in the outer lobes from steepening and maintain the spatial uniformity of the spectral index. Overall, it appears that 3C293 has gone through multiple (two to three) epochs of activity. This study adds 3C293 to the new sub-group of restarted galaxies with short interruption time periods. This is the first time a spatially resolved study has been performed that simultaneously studies a young source as well as the older outer lobes at such low frequencies. This illustrates the potential of the International LOFAR telescope to expand such studies to a larger sample of radio galaxies.
2805. CHIME/Pulsar 400-800MHz obs. of ATNF pulsars
ID:
ivo://CDS.VizieR/J/ApJS/255/5
Title:
CHIME/Pulsar 400-800MHz obs. of ATNF pulsars
Short Name:
J/ApJS/255/5
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present the design, implementation, and performance of the digital pulsar observing system constructed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Using accelerated computing, this system processes independent, digitally steered beams formed by the CHIME correlator to simultaneously observe up to 10 radio pulsars and transient sources. Each of these independent streams is processed by the CHIME/Pulsar back-end system, which can coherently dedisperse, in real time, up to dispersion measure values of 2500pc/cm^3^. The tracking beams and real-time analysis system are autonomously controlled by a priority-based algorithm that schedules both known sources and positions of interest for observation with observing cadences as rapid as 1 day. Given the distribution of known pulsars and radio-transient sources and the dynamic scheduling, the CHIME/Pulsar system can monitor 400-500 positions once per sidereal day and observe most sources with declinations greater than -20{deg} once every ~4 weeks. We also discuss the extensive science program enabled through the current modes of data acquisition for CHIME/Pulsar that centers on timing and searching experiments.
2806. Chinese Small Telescope ARray (CSTAR)
ID:
ivo://CDS.VizieR/J/PASP/122/347
Title:
Chinese Small Telescope ARray (CSTAR)
Short Name:
J/PASP/122/347
Date:
21 Oct 2021
Publisher:
CDS
Description:
In 2008 January the twenty-fourth Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g,r,i, and open) and has a 4.5{deg}x4.5{deg} field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every ~30s throughout the year whenever it is dark. During 2008, CSTAR 1 performed almost flawlessly, acquiring more than 0.3 million -band images for a total integration time of 1728hr during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to magnitude could be detected. We performed aperture photometry on all the sources in the field to create the catalog described herein. Since CSTAR has a fixed pointing centered on the south celestial pole (Dec=-90{deg}), all the sources within the FOV of CSTAR were monitored continuously for several months. The photometric catalog can be used for studying any variability in these sources, and for the discovery of transient sources such as supernovae, gamma-ray bursts, and minor planets.
2807. CHIPS II. O stars in Trumpler 14 CHIPS-Tr14
ID:
ivo://CDS.VizieR/J/A+A/658/A198
Title:
CHIPS II. O stars in Trumpler 14 CHIPS-Tr14
Short Name:
J/A+A/658/A198
Date:
25 Feb 2022 07:07:49
Publisher:
CDS
Description:
Most massive stars belong to multiple systems, yet the formation process leading to such high multiplicity remain insufficiently understood. To help constrain the different formation scenarios that exist, insights on the low-mass end of the companion mass function of such stars is crucial. However, this is a challenging endeavour as (sub-)solar mass companions at angular separations {rho} below 1" (corresponding to 1000-3000au in nearby young open clusters and OB associations) are difficult to detect due to the large brightness contrast with the central star. With the Carina High-contrast Imaging Project of massive Stars (CHIPS), we aim to obtain statistically significant constraints on the presence and properties of low-mass companions around massive stars at a previously unreachable observing window ({Delta}mag>=10 at {rho}<= 1"). In this second paper in the series, we focus on the Trumpler 14 cluster, which harbours some of the youngest and most massive O-type stars in the Milky Way. We obtained VLT-SPHERE observations of seven O-type objects in Trumpler 14 using the IRDIFS_EXT mode. These allow us to search for companions at separations larger than 0.15" (~360au) and down to magnitude contrast >10 mag in the near-infrared. We used angular and spectral differential imaging along with PSF fitting to detect sources and measure their flux relative to that of the central object. We detected 211 sources with near-infrared magnitude contrast in the range of 2 to 12. The closest companion, at only 0.26", is characterised as a 1.4M_{sun}_ stars with an age of 0.6Myr, in excellent agreement with previous age estimates for Tr14. The mass function peaks at about 0.4M_{sun}_ and presents a dearth of stars in the 0.5 to 0.8M_{sun}_ mass range compared to previous estimates of the initial mass function in Tr14.
2808. Chiron occultations
ID:
ivo://CDS.VizieR/J/AJ/107/1814
Title:
Chiron occultations
Short Name:
J/AJ/107/1814
Date:
21 Oct 2021
Publisher:
CDS
Description:
A photographic search was conducted for stars that may be occulted by the unusual solar system object (2060) Chiron during the period from fall 1993 through summer 1996. 44 candidates were identified to a limiting V magnitude of 16, and for which the minimum appulse separation with Chiron is predicted to be less than 2.5arcsec. The successful observation of a stellar occultation by Chiron would give a direct measure of its diameter (currently estimated to be between 60 and 300km), and would help considerably in constraining Chiron's surface properties and volatile makeup. If at the time of the occultation, Chiron exhibits a significant coma, there is also the potential for measuring the optical-depth profile of the dust in its inner coma.
2809. CH_3_OH 7_0_-6_1_ A^+^ maser sources
ID:
ivo://CDS.VizieR/J/ApJS/155/149
Title:
CH_3_OH 7_0_-6_1_ A^+^ maser sources
Short Name:
J/ApJS/155/149
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a Very Large Array survey of 44 massive star-forming regions in the 44GHz 7_0_-6_1_ A^+^ methanol transition; 37 fields showed maser emission. Thirty-one sources were also observed in the 23GHz 9_2_-10_1_ A^+^ methanol line; two fields showed maser emission.
2810. CH_3_OH and H_2_O Galactic center masers
ID:
ivo://CDS.VizieR/J/A+A/563/A68
Title:
CH_3_OH and H_2_O Galactic center masers
Short Name:
J/A+A/563/A68
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of star formation in the central molecular zone (CMZ) of our Galaxy through the association of three star formation indicators: 6.7GHz CH_3_OH masers, 22GHz H_2_O masers, and enhanced 4.5{mu}m emission ('green') sources. We explore how star formation in the CMZ (|l|<1.3{deg}, |b|<10') compares with that of the Galactic disk (6{deg}>l>345{deg}, |b|<2{deg}). Using an automated algorithm, we search for green sources toward 6.7GHz CH_3_OH masers detected in the Parkes Methanol Multibeam Survey. We combine these results with lists of 22GHz H_2_O masers, including our Mopra survey of the CMZ. We find that the correlation of CH_3_OH masers with green sources is a function of Galactic latitude, with a minimum close to b=0 and increasing with |b| (toward the central part of the Galaxy, 6{deg}>l>345{deg}, |b|<2{deg}). We find no significant difference between the correlation rate of CH_3_OH masers with green sources in the CMZ and the disk. This suggests that although the physical conditions of the gas are different in the CMZ from that of the Galactic disk, once gravitational instability sets in at sufficiently high densities, signatures of star formation appear to be similar in both regions. Moreover, the detection of green sources, even at the distance of the Galactic center, shows that our technique can easily identify the early stages of star formation, especially in low-extinction regions of the Galaxy. Through the association of H_2_O and CH_3_OH masers, we identify 15 star-forming sites in the CMZ. We find a higher correlation rate of coincident H_2_O and CH_3_OH masers within the CMZ compared to the Galactic disk, indicating a difference in the maser evolutionary sequence for star-forming cores in these two regions.

Limit your search

more »

more »

more »

more »

  • 218,083
  • 111

more »

more »