- ID:
- ivo://CDS.VizieR/J/ApJ/805/65
- Title:
- FLAMES observations of NGC 5128's globular clusters
- Short Name:
- J/ApJ/805/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the dynamical properties of 125 compact stellar systems (CSSs) in the nearby giant elliptical galaxy NGC 5128, using high-resolution spectra (R~26000) obtained with Very Large Telescope/FLAMES. Our results provide evidence for a new type of star cluster, based on the CSS dynamical mass scaling relations. All radial velocity (v_r_) and line-of-sight velocity dispersion ({sigma}_los_) measurements are performed with the penalized pixel fitting (ppxf) technique, which provided {sigma}_ppxf_ estimates for 115 targets. The {sigma}_ppxf_ estimates are corrected to the 2D projected half-light radii, {sigma}_1/2_, as well as the cluster cores, {sigma}_0_, accounting for observational/aperture effects and are combined with structural parameters, from high spatial resolution imaging, in order to derive total dynamical masses (M_dyn_) for 112 members of NGC5128's star cluster system. In total, 89 CSSs have dynamical masses measured for the first time along with the corresponding dynamical mass-to-light ratios ({sigma}_1/2_). We find two distinct sequences in the {gamma}^dyn^_V_-M_dyn_ plane, which are well approximated by power laws of the forms {gamma}^dyn^_V_{propto}M_dyn_^0.33+/-0.04^ and {gamma}^dyn^_V_{propto}M_dyn_^0.79+/-0.04^. The shallower sequence corresponds to the very bright tail of the globular cluster luminosity function (GCLF), while the steeper relation appears to be populated by a distinct group of objects that require significant dark gravitating components such as central massive black holes and/or exotically concentrated dark matter distributions. This result would suggest that the formation and evolution of these CSSs are markedly different from the "classical" globular clusters in NGC 5128 and the Local Group, despite the fact that these clusters have luminosities similar to the GCLF turnover magnitude. We include a thorough discussion of myriad factors potentially influencing our measurements.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/561/A87
- Title:
- FLAMES observations of Terzan 8
- Short Name:
- J/A+A/561/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive globular clusters (GCs) contain at least two generations of stars with slightly different ages and clearly distinct light elements abundances. The Na-O anticorrelation is the best studied chemical signature of multiple stellar generations. Low-mass clusters appear instead to be usually chemically homogeneous. We are investigating low-mass GCs to understand what is the lower mass limit where multiple populations can form, mainly using the Na and O abundance distribution. We used VLT/FLAMES spectra of giants in the low-mass, metal-poor GC Terzan 8, belonging to the Sagittarius dwarf galaxy, to determine abundances of Fe, O, Na, alpha-, Fe-peak, and neutron-capture elements in six stars observed with UVES and 14 observed with GIRAFFE. The average metallicity is [Fe/H]=-2.27+/-0.03 (rms=0.08), based on the six high-resolution UVES spectra. Only one star, observed with GIRAFFE, shows an enhanced abundance of Na and we tentatively assign it to the second generation. In this cluster, at variance with what happens in more massive GCs, the second generation seems to represent at most a small minority fraction. We discuss the implications of our findings, comparing Terzan 8 with the other Sgr dSph GCs, to GCs and field stars in the Large Magellanic Cloud, Fornax, and in other dwarfs galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/159/100
- Title:
- Flux & RVs of the dwarf G9-40 with K2 & HPF
- Short Name:
- J/AJ/159/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We validate the discovery of a 2-Earth-radii sub-Neptune-sized planet around the nearby high-proper-motion M2.5 dwarf G9-40 (EPIC212048748), using high-precision, near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrowband photometric filter, and adaptive optics imaging. At a distance of d=27.9pc, G9-40b is the second-closest transiting planet discovered by K2 to date. The planet's large transit depth (~3500ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J=10, K=9.2), makes G9-40b one of the most favorable sub-Neptune-sized planets orbiting an M dwarf for transmission spectroscopy with James Webb Space Telescope, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of ~29days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral-matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of Teff=3404{+/-}73K and metallicity of [Fe/H]=-0.08{+/-}0.13. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above 11.7M{Earth} with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of M=5.0_-1.9_^+3.8^M_{Earth}_ and an RV semiamplitude of K=4.1_-1.6_^+3.1^m/s, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future.
- ID:
- ivo://CDS.VizieR/J/AJ/152/136
- Title:
- Follow-up photometry and spectroscopy of KELT-17
- Short Name:
- J/AJ/152/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of a hot Jupiter transiting the V=9.23mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a 1.31_-0.29_^+0.28^M_J_, 1.525_-0.060_^+0.065^R_J_ hot-Jupiter in a 3.08-day period orbit misaligned at -115.9{deg}+/-4.1{deg} to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet during two transits. The nature of the spin-orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates ({alpha}<0.30 at 2{sigma} significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of 1.635_-0.061_^+0.066^M_{Sun}_, an effective temperature of 7454+/-49K, and a projected rotational velocity of vsinI_*_=44.2_-1.3_^+1.5^km/s; it is among the most massive, hottest, and most rapidly rotating of known planet hosts.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/84
- Title:
- Follow-up photometry and velocity of Qatar 2
- Short Name:
- J/ApJ/750/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery and initial characterization of Qatar-2b, a hot Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short period, P_b_= 1.34 days. The mass and radius of Qatar-2b are M_P_ = 2.49 M_J_ and R_P_= 1.14 R_J_, respectively. Radial-velocity monitoring of Qatar-2 over a span of 153 days revealed the presence of a second companion in an outer orbit. The Systemic Console yielded plausible orbits for the outer companion, with periods on the order of a year and a companion mass of at least several M_J_. Thus, Qatar-2 joins the short but growing list of systems with a transiting hot Jupiter and an outer companion with a much longer period. This system architecture is in sharp contrast to that found by Kepler for multi-transiting systems, which are dominated by objects smaller than Neptune, usually with tightly spaced orbits that must be nearly coplanar.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/1724
- Title:
- Follow-up photometry for HAT-P-11
- Short Name:
- J/ApJ/710/1724
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery of HAT-P-11b, the smallest radius transiting extrasolar planet (TEP) discovered from the ground, and the first hot Neptune discovered to date by transit searches. HAT-P-11b orbits the bright (V=9.587) and metal rich ([Fe/H]=+0.31+/-0.05) K4 dwarf star GSC 03561-02092 with P=4.8878162+/-0.0000071 days and produces a transit signal with depth of 4.2mmag, the shallowest found by transit searches that is due to a confirmed planet. We present a global analysis of the available photometric and radial velocity (RV) data that result in stellar and planetary parameters, with simultaneous treatment of systematic variations. HAT-P-11b orbits in an eccentric orbit with e=0.198+/-0.046 and {omega}=355.2{deg}+/-17.3{deg}, causing a reflex motion of its parent star with amplitude 11.6+/-1.2m/s, a challenging detection due to the high level of chromospheric activity of the parent star. Our ephemeris for the transit events is T_c_=2454605.89132+/-0.00032 (BJD), with duration 0.0957+/-0.0012 days, and secondary eclipse epoch of 2454608.96+/-0.15 days (BJD).
- ID:
- ivo://CDS.VizieR/J/AJ/144/19
- Title:
- Follow-up photometry for HAT-P-34 through HAT-P-37
- Short Name:
- J/AJ/144/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of four transiting extrasolar planets (HAT-P-34b-HAT-P-37b) with masses ranging from 1.05 to 3.33M_J_ and periods from 1.33 to 5.45days. These planets orbit relatively bright F and G dwarf stars (from V=10.16 to V=13.2). Of particular interest is HAT-P-34b which is moderately massive (3.33M_J_), has a high eccentricity of e=0.441+/-0.032 at a period of P=5.452654+/-0.000016days, and shows hints of an outer component. The other three planets have properties that are typical of hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/AJ/145/5
- Title:
- Follow-up photometry of HATS-1
- Short Name:
- J/AJ/145/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of HATS-1b, a transiting extrasolar planet orbiting the moderately bright V=12.05 G dwarf star GSC 6652-00186, and the first planet discovered by HATSouth, a global network of autonomous wide-field telescopes. HATS-1b has a period of P{approx}3.4465days, mass of M_p_{approx}1.86M_J_, and radius of R_p_{approx}1.30R_J_. The host star has a mass of 0.99M_{sun}_ and radius of 1.04R_{sun}_. The discovery light curve of HATS-1b has near-continuous coverage over several multi-day timespans, demonstrating the power of using a global network of telescopes to discover transiting planets.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A12
- Title:
- Foreground Galactic stars properties
- Short Name:
- J/A+A/555/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the chemical and kinematic properties of roughly a thousand FLAMES-GIRAFFE LR8 spectra of faint magnitude foreground Galactic stars observed serendipitously during extra-galactic surveys in four lines-of-sight: three in the southern Galactic hemisphere (surveys of the Carina, Fornax and Sculptor dwarf spheroidal galaxies) and one in the northern Galactic hemisphere (a survey of the Sextans dwarf spheroidal galaxy). The foreground stars span distances up to ~3kpc from the Galactic plane and Galactocentric radii up to 11kpc. The stellar atmospheric parameters (effective temperature, surface gravity, metallicity) are obtained by an automated parameterisation pipeline and the distances of the stars are then derived by a projection of the atmospheric parameters on a set of theoretical isochrones using a Bayesian approach. The metallicity gradients are estimated for each line-of-sight and compared with predictions from the Besancon model of the Galaxy, in order to test the chemical structure of the thick disc. Finally, we use the radial velocities in each line-of-sight to derive a proxy for either the azimuthal or the vertical component of the orbital velocity of the stars. Only three lines-of-sight have a sufficient number of foreground stars for a robust analysis. Towards Sextans in the Northern Galactic hemisphere and Sculptor in the South, we measure a consistent decrease in mean metallicity with height from the Galactic plane, suggesting a chemically symmetric thick disc. This decrease can either be due to an intrinsic thick disc metallicity gradient, or simply due to a change in the thin disc/thick disc population ratio and no intrinsic metallicity gradients for the thick disc. We favour the latter explanation. In contrast, we find evidence of an unpredicted metal-poor population in the direction of Carina. This population was earlier detected by Wyse et al. (2006ApJ...639L..13W), but our more detailed analysis provides robust estimates of its location (|Z|<1kpc), metallicity (-2<[M/H]<-1dex) and azimuthal orbital velocity (V_phi_~120km/s).
- ID:
- ivo://CDS.VizieR/J/A+A/296/319
- Title:
- Fornax cluster early-type galaxies
- Short Name:
- J/A+A/296/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)