- ID:
- ivo://CDS.VizieR/J/ApJ/767/51
- Title:
- Clusters of starburst galaxy NGC4214
- Short Name:
- J/ApJ/767/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The production rate of ionizing photons in young (<=8Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses {<~}10^3^M_{sun}_. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in H{alpha} luminosities, which needs to be taken into account when conducting this type of analysis.
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812. CMD for And III
- ID:
- ivo://CDS.VizieR/J/AJ/106/986
- Title:
- CMD for And III
- Short Name:
- J/AJ/106/986
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prime focus CCD camera of the KPNO 4 m telescope has been used to image Andromeda III, a dwarf spheroidal galaxy companion to M31, in the V and I bands. The resulting color-magnitude diagram shows a well defined giant branch whose tip luminosity corresponds to that expected for an old metal-poor population at the distance of M31. By comparing these data with the giant branches of metal-poor population at the distance of M31. By comparing these data with the giant branches of Galactic globular clusters, we determine that the abundance of And III is [Fe/H]=-2.0+/-0.15; with this abundance And III lies on the luminosity-abundance relation defined by the Galactic dwarf spheroidal galaxies. There is some evidence for a small (0.16<{sigma}([Fe/H])<0.24) intrinsic abundance dispersion within And III, but we are unable to unambiguously establish its presence. A study of the And III I-band luminosity function yields a distance modulus (m-M)_0_ of 24.4+/-0.2 for this galaxy, and indicates that the fraction of intermediate-age (3 to 10Gyr) population in And III is approximately 10+/-10 percent. In all these aspects And III, like And I, is similar to the Galactic dwarf spheroidal systems, indicating that M31 and the Galaxy provided similar conditions for the evolution of such galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/125/197
- Title:
- CN abundances of the 47 Tuc main sequence
- Short Name:
- J/AJ/125/197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a deep spectroscopic survey for star-to-star CN variations along the main sequence (MS) of the globular cluster 47 Tuc with ESO's Very Large Telescope. We find a significant bimodal distribution in the S(3839) index for main-sequence stars in the mass range ~0.85 to 0.65M_{sun}_, or from the main-sequence turnoff down to ~2.5 mag below the main-sequence turnoff. An anticorrelation of CN and CH is evident on the MS. The result is discussed in the context of the ability of faint MS stars to alter their surface composition through internal evolutionary effects. We argue against internal stellar evolution as the only origin for the abundance spread in 47 Tuc; an external origin such as pollution seems to be more likely.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/110
- Title:
- CN and CH indexes in stars of NGC 6791
- Short Name:
- J/ApJ/758/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-resolution SDSS/SEGUE spectra have been used to study the behavior of the strengths of the CN and CH molecular bands in stars at different evolutionary stages of the open cluster NGC 6791. We find a significant spread in the strengths of the CN bands, more than twice that expected from the uncertainties, although the bimodalities observed in globular clusters are not clearly observed here. This behavior is observed not only among red clump objects but also in unevolved stars such as those in the main sequence and lower red giant branch. In contrast, not all of the stars studied show significant scatter in their CH strengths.
- ID:
- ivo://CDS.VizieR/J/AJ/142/126
- Title:
- CN and CH in SDSS Galactic globular clusters
- Short Name:
- J/AJ/142/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous survey of the CN and CH band strengths in eight Galactic globular clusters observed during the course of the Sloan Extension for Galactic Understanding and Exploration sub-survey (SEGUE) of the Sloan Digital Sky Survey. We confirm the existence of a bimodal CN distribution among red giant branch (RGB) stars in all of the clusters with metallicity greater than [Fe/H]=-1.7; the lowest metallicity cluster with an observed CN bimodality is M53, with [Fe/H]~=-2.1. There is also some evidence for individual CN groups on the subgiant branches of M92, M2, and M13, and on the RGBs of M92 and NGC 5053. Finally, we quantify the correlation between overall cluster metallicity and the slope of the CN band strength-luminosity plot as a means of further demonstrating the level of CN enrichment in cluster giants. Our results agree well with previous studies reported in the literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/408/181
- Title:
- CN2002ch UBVRI and ugriz light curves
- Short Name:
- J/MNRAS/408/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometric and spectroscopic observations of an unusual luminous blue variable (LBV) in NGC 3432, covering three major outbursts in 2008 October, 2009 April and 2009 November. Previously, this star experienced an outburst also in 2000 (known as SN 2000ch). During outbursts the star reached an absolute magnitude between -12.1 and -12.8. Its spectrum showed H, HeI and FeII lines with P-Cygni profiles during and soon after the eruptive phases, while only intermediate-width lines in pure emission (including HeII {lambda}4686) were visible during quiescence. The fast-evolving light curve soon after the outbursts, the quasi-modulated light curve, the peak magnitude and the overall spectral properties are consistent with multiple episodes of variability of an extremely active LBV. However, the widths of the spectral lines indicate unusually high wind velocities (1500-2800km/s), similar to those observed in Wolf-Rayet stars. Although modulated light curves are typical of LBVs during the S-Dor variability phase, the luminous maxima and the high frequency of outbursts are unexpected in S-Dor variables.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3816
- Title:
- Cobalt emission in nebular phase spectra
- Short Name:
- J/MNRAS/454/3816
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of ^56^Ni to ^56^Co at early times, and the decay of ^56^Co to ^56^Fe from ~60 d after explosion. We examine the evolution of the [CoIII] {lambda}5893 emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of ^56^Co as a function of time. This result indicates both efficient local energy deposition from positrons produced in ^56^Co decay and long-term stability of the ionization state of the nebula. We compile SN Ia nebular spectra from the literature and present 21 new late-phase spectra of 7 SNe Ia, including SN 2014J. From these we measure the flux in the [CoIII] {lambda}5893 line and remove its well-behaved time dependence to infer the initial mass of ^56^Ni (M_Ni_) produced in the explosion. We then examine ^56^Ni yields for different SN Ia ejected masses (M_ej_ - calculated using the relation between light-curve width and ejected mass) and find that the ^56^Ni masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s~0.7-0.9), M_Ni_ is clustered near M_Ni_~0.4M_{sun}_ and shows a shallow increase as M_ej_ increases from ~1 to 1.4M_{sun}_; at high stretch, M_ej_ clusters at the Chandrasekhar mass (1.4M_{sun}_) while M_Ni_ spans a broad range from 0.6 to 1.2M_{sun}_. This could constitute evidence for two distinct SN Ia explosion mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJ/891/171
- Title:
- COCONUTS. I. Spectra of a WD and T4 comoving syst.
- Short Name:
- J/ApJ/891/171
- Date:
- 17 Jan 2022 13:06:37
- Publisher:
- CDS
- Description:
- We present the first discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, a large-scale survey for wide-orbit planetary and substellar companions. We have discovered a comoving system COCONUTS-1, composed of a hydrogen-dominated white dwarf (PSOJ058.9855+45.4184; d=31.5pc) and a T4 companion (PSOJ058.9869+45.4296) at a 40.6" (1280au) projected separation. We derive physical properties for COCONUTS-1B from (1) its near-infrared spectrum using cloudless Sonora atmospheric models, and (2) its luminosity and the white dwarf's age (7.3_-1.6_^+2.8^Gyr) using Sonora evolutionary models. The two methods give consistent temperatures and radii, but atmospheric models infer a lower surface gravity and therefore an unphysically young age. Assuming evolutionary model parameters (T_eff_=1255_-8_^+6^K, logg=5.44_-0.03_^+0.02^dex, R=0.789_-0.005_^+0.011^R_Jup_), we find that cloudless model atmospheres have brighter Y- and J-band fluxes than the data, suggesting that condensate clouds have not fully dispersed around 1300K. The W2 flux (4.6{mu}m) of COCONUTS-1B is fainter than models, suggesting non-equilibrium mixing of CO. To investigate the gravity dependence of the L/T transition, we compile all 60 known L6-T6 benchmarks and derive a homogeneous set of temperatures, surface gravities, and masses. As is well known, young, low-gravity late-L dwarfs have significantly fainter, redder near-infrared photometry and ~200-300K cooler temperatures than old, high-gravity objects. Our sample now reveals such gravity dependence becomes weaker for T dwarfs, with young objects having comparable near-infrared photometry and ~100K cooler temperatures compared to old objects. Finally, we find that young objects have a larger amplitude J-band brightening than old objects, and also brighten at H band as they cross the L/T transition.
- ID:
- ivo://CDS.VizieR/J/AJ/157/228
- Title:
- Cold Classical TNOs: LCs & rotational properties
- Short Name:
- J/AJ/157/228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey of the rotational and physical properties of the dynamically low inclination Cold Classical (CC) trans-Neptunian objects (TNOs). The CCs are primordial planetesimals and contain information about our solar system and planet formation over the first 100 million years after the Sun's formation. We obtained partial/complete light curves for 42 CCs. We use statistical tests to derive general properties about the shape and rotational frequency distributions of the CCs and infer that they have slower rotations and are more elongated/deformed than the other TNOs. On the basis of the full light curves, the mean rotational period of the CCs is 9.48+/-1.53 hr compared to 8.45+/-0.58 hr for the rest of the TNOs. About 65% of the TNOs have a light-curve amplitude below 0.2 mag compared to the 36% of CCs with small amplitude. We present the full light curve of one likely contact binary, 2004 VC_131_, with a potential density of 1 g/cm^3^ for a mass ratio of 0.4. We have hints that 2004 MU_8_ and 2004 VU_75_ are perhaps potential contact binaries, on the basis of their sparse light curves, but more data are needed to confirm this finding. Assuming equal-sized binaries, we find that ~10%-25% of the CCs could be contact binaries, suggesting a deficit of contact binaries in this population compared to previous estimates and to the (~40%-50%) possible contact binaries in the Plutino population. These estimates are lower limits and may increase if nonequal-sized contact binaries are considered. Finally, we put in context the results of the New Horizons flyby of 2014 MU_69_.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/130
- Title:
- Collinder 261 Chandra sources & optical counterparts
- Short Name:
- J/ApJ/837/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.
