- ID:
- ivo://CDS.VizieR/J/ApJ/903/73
- Title:
- MAVERIC survey: deep VLA imaging of 25 GCs
- Short Name:
- J/ApJ/903/73
- Date:
- 17 Feb 2022 13:24:49
- Publisher:
- CDS
- Description:
- The MAVERIC survey is the first deep radio continuum imaging survey of Milky Way globular clusters, with a central goal of finding and classifying accreting compact binaries, including stellar-mass black holes. Here we present radio source catalogs for 25 clusters with ultra-deep Karl G. Jansky Very Large Array observations. The median observing time was 10 hr per cluster, resulting in typical rms sensitivities of 2.3 and 2.1{mu}Jy per beam at central frequencies of 5.0 and 7.2GHz, respectively. We detect nearly 1300 sources in our survey at 5{sigma}, and while many of these are likely to be background sources, we also find strong evidence for an excess of radio sources in some clusters. The radio spectral index distribution of sources in the cluster cores differs from the background, and shows a bimodal distribution. We tentatively classify the steep-spectrum sources (those much brighter at 5.0GHz) as millisecond pulsars and the flat-spectrum sources as compact or other kinds of binaries. These provisional classifications will be solidified with the future addition of X-ray and optical data. The outer regions of our images represent a deep, relatively wide-field (~0.4deg^2^) and high-resolution C band background survey, and we present source counts calculated for this area. We also release radio continuum images for these 25 clusters to the community.
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Search Results
512. M 68 BVRI photometry
- ID:
- ivo://CDS.VizieR/J/AJ/99/1831
- Title:
- M 68 BVRI photometry
- Short Name:
- J/AJ/99/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) observed with a CCD camera and the 2.2m telescope at ESO/La Silla, and have compared our BV color-magnitude diagrams with the observational results of a previous research. At magnitudes V<22, our BV results, obtained using the INVENTORY code, are in very close agreement with those of the other authors who used DAOPHOT in their reductions. At fainter levels, selection effects appear to affect INVENTORY more than DAOPHOT. We find that V_TO-HB_=3.42+/-0.10, in accord with values found for other clusters. The comparison between our four-color observations and the theoretical isochrones consistently yield a cluster age of 13Gyr with a likely external uncertainty of 2 or 3Gyr. Our derived values for the interstellar reddening at longer wavelengths are generally in agreement (+/-0.02mag) with what would be expected assuming E(B-V)=0.07mag and (m-M)_V_=15.25.
513. M 4 CCD photometry
- ID:
- ivo://CDS.VizieR/J/AJ/114/189
- Title:
- M 4 CCD photometry
- Short Name:
- J/AJ/114/189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the ESO NTT, we have obtained accurate CCD UBVI photometry of 1649 stars in an extended field in the globular cluster M 4 = NGC 6121. The position of the main-sequence turnoff is found to be at V_TO_=17.0+/-0.1mag, (B-V)=0.863+/-0.007, (V-I)=1.224+/-0.010, (B-I)=2.084+/-0.010. Our turnoff point is redder and fainter than those found for M 4 in the majority of recent studies, probably because of our field being located in the western, most reddened part of the cluster. The spread of stars around the main-sequence locus has an unusual shape (broadening near the turnoff point and close to the photometric limit), earlier noticed by Richer et al. (1995ApJ...451L..17R) and attributed by them to photometric effects. We have analyzed the possible reasons for this effect and concluded that, at least in our case, it is most probably due to differential absorption. We confirm the deviation of theoretical isochrones from the fainter parts of the M 4 main-sequence locus found by Alcaino et al. (1988ApJ...330..569A). Several curious structural details (a depression and an excess of stars) have been revealed in the brighter parts of the main-sequence luminosity function of M 4.
- ID:
- ivo://CDS.VizieR/J/AJ/141/62
- Title:
- M5 chemical abundances for evolved stars
- Short Name:
- J/AJ/141/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of high-resolution spectra of a sample of stars in the globular cluster M5 (NGC 5904). The sample includes stars from the red giant branch (RGB; seven stars), the red horizontal branch (two stars), and the asymptotic giant branch (AGB; eight stars), with effective temperatures ranging from 4000K to 6100K. Spectra were obtained with the HIRES spectrometer on the Keck I telescope, with a wavelength coverage from 3700{AA} to 7950{AA} for the HB and AGB sample, and 5300{AA} to 7600{AA} for the majority of the RGB sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/2621
- Title:
- M4 Core Project with HST. Radial velocities
- Short Name:
- J/MNRAS/454/2621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of the internal kinematics of the Galactic globular cluster M 4 (NGC 6121), by deriving the radial velocities from 7250 spectra for 2771 stars distributed from the upper part of the red giant branch down to the main sequence. We describe new approaches to determine the wavelength solution from day-time calibrations and to determine the radial velocity drifts that can occur between calibration and science observations when observing with the GIRAFFE spectrograph at Very Large Telescope. Two techniques to determine the radial velocity are compared, after a qualitative description of their advantages with respect to other commonly used algorithm, and a new approach to remove the sky contribution from the spectra obtained with fibre-fed spectrograph and further improve the radial velocity precision is presented. The average radial velocity of the cluster is <v>=71.08+/-0.08km/s with an average dispersion of {mu}_vc_=3.97km/s. Using the same data set and the same statistical approach of previous analyses, 20 additional binary candidates are found, for a total of 87 candidates. A new determination of the internal radial velocity dispersion as a function of cluster distance is presented, resulting in a dispersion of 4.5km/s within 2-arcmin from the centre of cluster and steadily decreasing outward. We statistically confirm the small amplitude of the cluster rotation, as suggested in the past by several authors. This new analysis represents a significant improvement with respect to previous results in literature and provides a fundamental observational input for the modelling of the cluster dynamics.
- ID:
- ivo://CDS.VizieR/J/AJ/132/2187
- Title:
- MCT1 photometry of NGC 5128 globular clusters
- Short Name:
- J/AJ/132/2187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results from an imaging program with the ACS on the Hubble Space Telescope designed to measure the structural characteristics of a wide range of globular clusters in NGC 5128, the nearest giant elliptical galaxy. From 12 ACS WFC fields we have measured a total of 62 previously known globular clusters and have discovered 69 new high-probability cluster candidates not found in any previous work. We present magnitudes and color indices for all of these, along with rough measurements of their effective diameters and ellipticities.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A161
- Title:
- Measured atmospheric parameters of NGC6397 stars
- Short Name:
- J/A+A/635/A161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent work has used spectra of ~5000 stars in NGC 6397 that were extracted from a MUSE mosaic to determine the atmospheric parameters for these stars by fitting the spectra against the Goettingen Spectral Library. A significant change in metallicity between the turn off and the red giant branch was found and was discussed as a possible manifestation of predicted effects of atomic diffusion. However, the small amplitude of the effect and inconsistency with earlier measurements call for more attention before this result is interpreted. Systematic effects due to the interpolation or to the synthetic spectra cannot be ruled out at this level of precision. We reanalyze the data with : the ELODIE and MILES reference libraries in order to assess the robustness of the result. These empirical libraries have a finer metallicity coverage down to approximately the cluster metallicity turn-off. Methods. We used the ULySS full-spectrum fitting package, together with the library interpolators to remeasure the three atmospheric parameters effective temperature, surface gravity, and [Fe/H] metallicity. We find a very low [Fe/H] dispersion along the isochrone (0.07dex), consistent with our error estimate (0.05dex). However, the [Fe/H] trend is not reproducible. This shows that the data have the potential to reveal patterns of the magnitude of the expected physical effects, but the analysis methods need to be refined to cull systematic effects that currently dominate the patterns.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/19
- Title:
- Megasecond Chandra XVP obs. of NGC3115. II.
- Short Name:
- J/ApJ/808/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out an in-depth study of low-mass X-ray binaries (LMXBs) detected in the nearby lenticular galaxy NGC 3115 using the Megasecond Chandra X-ray Visionary Project observation (total exposure time 1.1Ms). In total we found 136 candidate LMXBs in the field and 49 in globular clusters (GCs) above 2{sigma} detection, with 0.3-8keV luminosity L_X_~10^36^-10^39^erg/s. Other than 13 transient candidates, the sources overall have less long-term variability at higher luminosity, at least at L_X_>~2x10^37^erg/s. In order to identify the nature and spectral state of our sources, we compared their collective spectral properties based on single-component models (a simple power law or a multicolor disk) with the spectral evolution seen in representative Galactic LMXBs. We found that in the L_X_ versus photon index {Gamma}_PL_ and L_X_versus disk temperature kT_MCD_ plots, most of our sources fall on a narrow track in which the spectral shape hardens with increasing luminosity below L_X_~7x10^37^erg/s, but is relatively constant ({Gamma}_PL_~1.5 or kT_MCD_~1.5keV) above this luminosity, which is similar to the spectral evolution of Galactic neutron star (NS) LMXBs in the soft state in the Chandra bandpass. Therefore, we identified the track as the NS LMXB soft-state track and suggested sources with L_X_<~7x10^37^erg/s as atolls in the soft state and those with L_X_>~7x10^37^erg/s as Z sources. Ten other sources (five are transients) displayed significantly softer spectra and are probably black hole X-ray binaries in the thermal state. One of them (persistent) is in a metal-poor GC.
- ID:
- ivo://CDS.VizieR/J/other/RAA/18.126
- Title:
- Membership catalog for M12 (NGC6218) stars
- Short Name:
- J/other/RAA/18.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using astrometric techniques developed by Anderson et al., we determine proper motions (PMs) in the ~14.60x16.53arcmin^2^ area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of ~11.1-years were observed with the wide-field imager (WFI) mosaic camera mounted on the ESO 2.2m telescope. The median value of PM error in both components is ~0.7mas/yr for the stars having V<=20mag. PMs are used to determine membership probabilities and to separate field stars from the cluster sample. In electronic form, a membership catalog of 3725 stars with precise coordinates, PMs and BV RI photometry is being provided. One of the possible applications of the catalog is demonstrated by gathering the membership information of the variable stars, blue stragglers and X-ray sources reported earlier in the cluster's region.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A13
- Title:
- Metal abundances in 6 globular cluster
- Short Name:
- J/A+A/573/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed almost one third of the globular clusters in the Milky Way, targeting distant and/or highly reddened objects, as well as a few reference clusters. A large sample of red giant stars was observed with FORS2 at VLT/ESO at R~2000. The method for deriving stellar parameters is presented with application to six reference clusters. We aim at deriving the stellar parameters effective temperature, gravity, metallicity, and {alpha}-element enhancement as well as the radial velocity to confirm the membership of individual stars in each cluster. We analyse the spectra collected for the reference globular clusters NGC 6528 ([Fe/H]~-0.1), NGC 6553 ([Fe/H]~-0.2), M 71 ([Fe/H]~-0.8), NGC 6558 ([Fe/H]~-1.0), NGC 6426 ([Fe/H]~-2.1), and Terzan 8 ([Fe/H]~-2.2). They cover the full range of globular cluster metallicities, and are located in the bulge, disc, and halo. Full spectrum-fitting techniques were applied by comparing each target spectrum with a stellar library in the optical region at 4560-5860{AA}. We employed the library of observed spectra MILES, and the Coelho synthetic library. We validated the method by recovering the known atmospheric parameters for 49 well-studied stars that cover a wide range in the parameter space. We adopted as final stellar parameters (effective temperatures, gravities, metallicities) the average of results using the observed and synthetic spectral libraries.
