- ID:
- ivo://CDS.VizieR/J/AJ/151/26
- Title:
- Spectroscopy of five {gamma} Dor variables
- Short Name:
- J/AJ/151/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined the spectroscopic orbits of five {gamma} Dor variables, HD776, HD6568, HD17310, HD19684, and HD62196. Their orbital periods range from 27.8 to 1163days and their eccentricities from 0.01 to 0.65. Of the five systems, only HD19684 shows lines of its binary companion, but those lines are always so weak and blended with the lines of the primary that we were unable to measure them satisfactorily. The velocity residuals of the orbital fits were searched for periodicities associated with pulsation. No clear, convincing case for velocity periodicities in the residuals was found in four of the five stars. However, for HD17310 we identified a period of 2.13434days, a value in agreement with the largest amplitude period previously found photometrically for that star. The velocity residuals of HD62196 have a long-term trend suggesting that it is a triple system.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/144/8
- Title:
- Spectroscopy of ~100 G/K/M-type Sco-Cen complex members
- Short Name:
- J/AJ/144/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have spectroscopically identified ~100 G-, K-, and M-type members of the Scorpius-Centaurus complex. To deduce the age of these young stars we compare their Li {lambda}6708 absorption line strengths against those of stars in the TW Hydrae association and {beta} Pictoris moving group. These line strengths indicate that Sco-Cen stars are younger than {beta} Pic stars whose ages of ~12Myr have previously been derived from a kinematic traceback analysis. Our derived age, ~10Myr, for stars in the Lower Centaurus Crux and Upper Centaurus Lupus subgroups of ScoCen is younger than previously published ages based on the moving cluster method and upper main-sequence fitting. The discrepant ages are likely due to an incorrect (or lack of) cross-calibration between model-dependent and model-independent age-dating methods.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/1335
- Title:
- Spectroscopy of globulars in NGC 5128
- Short Name:
- J/ApJ/708/1335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new integrated light spectroscopy of globular clusters (GCs) in NGC 5128, a nearby giant elliptical galaxy less than 4Mpc away, in order to measure radial velocities and derive ages, metallicities, and alpha-element abundance ratios. Using the Gemini South 8 meter telescope with the instrument Gemini Multi-Object Spectrograph, we obtained spectroscopy in the range of ~3400-5700{AA} for 72 GCs with a signal-to-noise ratio greater than 30{AA}^-1^; and we have also discovered 35 new GCs within NGC 5128 from our radial velocity measurements. We measured and compared the Lick indices from H{delta}_A_ through Fe5406 with the single stellar population models of Thomas et al. (2003MNRAS.339..897T, 2004MNRAS.351L..19T) in order to derive age, metallicity, and [{alpha}/Fe] values.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/137
- Title:
- Spectroscopy of Grus II, Tuc IV and Tuc V
- Short Name:
- J/ApJ/892/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/IMACS spectroscopy of three recently discovered ultra-faint Milky Way satellites, Grus II, Tucana IV, and Tucana V. We measure systemic velocities of v_hel_=-110.0+/-0.5km/s, v_hel_=15.9_-1.7_^+1.8^km/s, and v_hel_=-36.2_-2.2_^+2.5^km/s for the three objects, respectively. Their large relative velocities demonstrate that the satellites are unrelated despite their close physical proximity. We determine a velocity dispersion for Tuc IV of {sigma}=4.3_-1.0_^+1.7^km/s, but we cannot resolve the velocity dispersions of the other two systems. For Gru II, we place an upper limit (90% confidence) on the dispersion of {sigma}<1.9km/s, and for Tuc V, we do not obtain any useful limits. All three satellites have metallicities below [Fe/H]=-2.1, but none has a detectable metallicity spread. We determine proper motions for each satellite based on Gaia astrometry and compute their orbits around the Milky Way. Gru II is on a tightly bound orbit with a pericenter of 25_-7_^+6^kpc and orbital eccentricity of 0.45_-0.05_^+0.08^. Tuc V likely has an apocenter beyond 100kpc and could be approaching the Milky Way for the first time. The current orbit of Tuc IV is similar to that of Gru II, with a pericenter of 25_-8_^+11^kpc and an eccentricity of 0.36_-0.06_^+0.13^. However, a backward integration of the position of Tuc IV demonstrates that it collided with the Large Magellanic Cloud at an impact parameter of 4kpc ~120Myr ago, deflecting its trajectory and possibly altering its internal kinematics. Based on their sizes, masses, and metallicities, we classify Gru II and Tuc IV as likely dwarf galaxies, but the nature of Tuc V remains uncertain.
1875. Spectroscopy of HD 5980
- ID:
- ivo://CDS.VizieR/J/AJ/148/62
- Title:
- Spectroscopy of HD 5980
- Short Name:
- J/AJ/148/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New spectroscopic observations of the LBV/WR multiple system HD 5980 in the Small Magellanic Cloud are used to address the question of the masses and evolutionary status of the two very luminous stars in the 19.3 day eclipsing binary system. Two distinct components of the NV4944{AA} line are detected in emission and their radial velocity variations are used to derive masses of 61 and 66M_{sun}_, under the assumption that binary interaction effects on this atomic transition are negligible. We propose that this binary system is the product of quasi-chemically homogeneous evolution with little or no mass transfer. Thus, both of these binary stars may be candidates for gamma-ray burst progenitors or even pair instability supernovae. Analysis of the photospheric absorption lines belonging to the third-light object in the system confirm that it consists of an O-type star in a 96.56day eccentric orbit (e=0.82) around an unseen companion. The 5:1 period ratio and high eccentricities of the two binaries suggest that they may constitute a hierarchical quadruple system.
1876. Spectroscopy of HD 45166
- ID:
- ivo://CDS.VizieR/J/A+A/444/895
- Title:
- Spectroscopy of HD 45166
- Short Name:
- J/A+A/444/895
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The binary star HD 45166 has been observed since 1922 but its orbital period has not yet been found. It is considered a peculiar Wolf-Rayet star, and its assigned classification has varied. For this reason we included the object as a candidate V Sge star and performed spectroscopy in order to search for its putative orbital period. High-resolution spectroscopic observations show that the spectrum, in emission and in absorption, is quite rich. The emission lines have great diversity of widths and profiles. The full widths at half maximum vary from 70km/s for the weakest lines up to 370km/s for the most intense ones. The Hydrogen and Helium lines are systematically broader than the CNO lines. Assuming that HD 45166 is a double-line spectroscopic binary, it present s an orbital period of P=1.596+/-0.003-day, with an eccentricity of e=0.18+/-0.08. In addition, a search for periodicity using standard techniques reveals that the emission lines present at least two other periods, of 5 and 5 hour. The secondary star has a spectral type of B7 V and, therefore, should have a mass of about M=4.8M_{sun}_. Given the radial velocity amplitudes, we determined the mass of the hot (primary) star as M=4.2+/-0.7M_{sun}_ and the inclination angle of the system, i=0.77+/-0.09deg. As the eccentricity of the orbit is non zero, the Roche lobes increase and decrease as a function of the orbital phase. At periastron, the secondary star fills its Roche lobe. The distance to the star has been re-determined as d=1.3+/-0.2kpc and a color excess of E(B-V)=0.155+/-0.007 has been derived. This implies an absolute B magnitude of -0.6 for the primary star and -0.7 for the B7 star. We suggest that the discrete absorption components (DACs) observed in the ultraviolet with a periodicity similar to the orbital period may be induced by periastron events.
- ID:
- ivo://CDS.VizieR/J/ApJ/735/L46
- Title:
- Spectroscopy of 64 K red giants
- Short Name:
- J/ApJ/735/L46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in the outer Galactic disk, located at Galactocentric distances between 9 and 13kpc. The outer disk sample is complemented with samples of red giants from the inner Galactic disk and the solar neighborhood, analyzed using identical methods. For Galactocentric distances beyond 10kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighborhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. We make a first estimate of the thick disk scale length of L_thick_=2.0kpc, assuming L_thin_=3.8kpc for the thin disk. We suggest that radial migration may explain the lack of radial age, metallicity, and abundance gradients in the thick disk, possibly also explaining the link between the thick disk and the metal-poor bulge.
- ID:
- ivo://CDS.VizieR/J/ApJ/657/241
- Title:
- Spectroscopy of Leo I red giants
- Short Name:
- J/ApJ/657/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present low-resolution spectroscopy of 120 red giants in the Galactic satellite dwarf spheroidal (dSph) Leo I, obtained with GeminiN GMOS and Keck DEIMOS. We find stars with velocities consistent with membership of Leo I out to 1.3 King tidal radii. By measuring accurate radial velocities with a median measurement error of 4.6km/s, we find a mean systemic velocity of 284.2km/s with a global velocity dispersion of 9.9km/s. The dispersion profile is consistent with being flat out to the last data point.
- ID:
- ivo://CDS.VizieR/J/AJ/144/88
- Title:
- Spectroscopy of 6 LMC RR Lyrae and 3 SMC RR Lyrae
- Short Name:
- J/AJ/144/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present for the first time a detailed spectroscopic study of chemical element abundances of metal-poor RR Lyrae stars in the Large and Small Magellanic Cloud (LMC and SMC). Using the MagE echelle spectrograph at the 6.5m Magellan telescopes, we obtain medium resolution (R~2000-6000) spectra of six RR Lyrae stars in the LMC and three RR Lyrae stars in the SMC. These stars were chosen because their previously determined photometric metallicities were among the lowest metallicities found for stars belonging to the old populations in the Magellanic Clouds. We find the spectroscopic metallicities of these stars to be as low as [Fe/H]_spec_=-2.7dex, the lowest metallicity yet measured for any star in the Magellanic Clouds. We confirm that for metal-poor stars, the photometric metallicities from the Fourier decomposition of the light curves are systematically too high compared to their spectroscopic counterparts. However, for even more metal-poor stars below [Fe/H]_phot_<-2.8dex this trend is reversed and the spectroscopic metallicities are systematically higher than the photometric estimates. We are able to determine abundance ratios for 10 chemical elements (Fe, Na, Mg, Al, Ca, Sc, Ti, Cr, Sr, and Ba), which extend the abundance measurements of chemical elements for RR Lyrae stars in the Clouds beyond [Fe/H] for the first time. For the overall [{alpha}/Fe] ratio, we obtain an overabundance of 0.36dex, which is in very good agreement with results from metal-poor stars in the Milky Way halo as well as from the metal-poor tail in dwarf spheroidal galaxies. Comparing the abundances with those of the stars in the Milky Way halo we find that the abundance ratios of stars of both populations are consistent with another. Therefore, we conclude that from a chemical point of view early contributions from Magellanic-type galaxies to the formation of the Galactic halo as claimed in cosmological models are plausible.
- ID:
- ivo://CDS.VizieR/J/ApJ/748/29
- Title:
- Spectroscopy of M87 globular clusters
- Short Name:
- J/ApJ/748/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The halos of galaxies preserve unique records of their formation histories. We carry out the first combined observational and theoretical study of phase-space halo substructure in an early-type galaxy: M87, the central galaxy in the Virgo cluster. We analyze an unprecedented wide-field, high-precision photometric and spectroscopic data set for 488 globular clusters (GCs), which includes new, large-radius Subaru/Suprime-Cam and Keck/DEIMOS observations. We find signatures of two substructures in position-velocity phase space. One is a small, cold stream associated with a known stellar filament in the outer halo; the other is a large shell-like pattern in the inner halo that implies a massive, hitherto unrecognized accretion event. We perform extensive statistical tests and independent metallicity analyses to verify the presence and characterize the properties of these features, and to provide more general methodologies for future extragalactic studies of phase-space substructure. The cold outer stream is consistent with a dwarf galaxy accretion event, while for the inner shell there is tension between a low progenitor mass implied by the cold velocity dispersion, and a high mass from the large number of GCs, which might be resolved by a ~0.5 L* E/S0 progenitor.
