Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/879/49
- Title:
- Rotation periods for 171 Gaia members of NGC 6811
- Short Name:
- J/ApJ/879/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation was proposed as a potential age diagnostic that is precise, simple, and applicable to a broad range of low-mass stars (<=1M_{sun}_). Unfortunately, rotation period (P_rot_) measurements of low-mass members of open clusters have undermined the idea that stars spin down with a common age dependence (i.e., P_rot{propto}age^0.5^): K dwarfs appear to spin down more slowly than F and G dwarfs. Agueros+ (2018, J/ApJ/862/33) interpreted data for the ~1.4Gyr-old cluster NGC 752 differently, proposing that after having converged onto a slow-rotating sequence in their first 600-700Myr (by the age of Praesepe), K dwarf P_rot_ stall on that sequence for an extended period of time. We use data from Gaia DR2 to identify likely single-star members of the ~1Gyr-old cluster NGC 6811 with Kepler light curves. We measure P_rot_ for 171 members, more than doubling the sample relative to the existing catalog and extending the mass limit from ~0.8 to ~0.6M_{sun}_. We then apply a gyrochronology formula calibrated with Praesepe and the Sun to 27 single G dwarfs in NGC 6811 to derive a precise gyrochronological age for the cluster of 1.04+/-0.07Gyr. However, when our new low-mass rotators are included, NGC 6811's color-P_rot_ sequence deviates away from the naive 1Gyr projection down to T_eff_~4295K (K5V, 0.7M_{sun}), where it clearly overlaps with Praesepe's. Combining these data with P_rot_ for other clusters, we conclude that the assumption that mass and age are separable dependencies is invalid. Furthermore, the cluster data show definitively that stars experience a temporary epoch of reduced braking efficiency where P_rot_ stall, and that the duration of this epoch lasts longer for lower-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/20
- Title:
- Rotation periods of asteroids using iPTF
- Short Name:
- J/ApJS/227/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to look for large super-fast rotators, in late 2014 and early 2015, five dedicated surveys covering ~188deg^2^ in the ecliptic plane have been carried out in the R-band, with ~10min cadence using the intermediate Palomar Transient Factory. Among 1029 reliable rotation periods obtained from the surveys, we discovered 1 new large super-fast rotator, (40511) 1999 RE88, and 18 other candidates. (40511) 1999 RE88 is an S-type inner main-belt asteroid with a diameter of D=1.9+/-0.3km, a rotation period of P=1.96+/-0.01hr, and a light curve amplitude of {Delta}m~1.0mag. To maintain such fast rotation, an internal cohesive strength of ~780Pa is required. Combining all known large super-fast rotators, their cohesive strengths all fall in the range of 100-1000Pa of lunar regolith. However, the number of large super-fast rotators seems to be far less than the whole asteroid population. This might indicate a peculiar asteroid group for them. Although the detection efficiency for a long rotation period is greatly reduced due to our two-day observation time span, the spin-rate distributions of this work show consistent results with Chang+ (2015, J/ApJS/219/27), after considering the possible observational bias in our surveys. It shows a number decrease with an increase of spin rate for asteroids with a diameter of 3<=D<=15km, and a number drop at a spin rate of f=5rev/day for asteroids with D<=3km.
- ID:
- ivo://CDS.VizieR/J/A+A/634/L9
- Title:
- Rotation periods of 97 solar-like stars
- Short Name:
- J/A+A/634/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accurate determination of stellar rotation periods is important for estimating stellar ages and for understanding stellar activity and evolution. While rotation periods can be determined for about thirty thousand stars in the Kepler field, there are over one hundred thousand stars, especially with low photometric variability and irregular pattern of variations, for which rotational periods are unknown. Here we investigate the effect of metallicity on the detectability of rotation periods. This is done by synthesising light curves of hypothetical stars that are identical to our Sun with the exception of the metallicity. These light curves are then used as an input to the period determination algorithms. We find that the success rate for recovering the rotation signal has a minimum close to the solar metallicity value. This can be explained by the compensation effect of facular and spot contributions. In addition, selecting solar-like stars with near-solar effective temperature and photometric variability, and with metallicity between M/H=-0.35 and M/H=0.35 from the Kepler sample, we analyse the fraction of stars for which rotational periods have been detected as a function of metallicity. In agreement with our theoretical estimate we find a local minimum for the detection fraction close to the solar metallicity. We further report rotation periods of 87 solar-like Kepler stars for the first time.
- ID:
- ivo://CDS.VizieR/J/AJ/162/147
- Title:
- Rotation periods of 43 TOIs with Evryscope and TESS
- Short Name:
- J/AJ/162/147
- Date:
- 14 Mar 2022 06:47:58
- Publisher:
- CDS
- Description:
- Stellar radial-velocity (RV) jitter due to surface activity may bias the RV semiamplitude and mass of rocky planets. The amplitude of the jitter may be estimated from the uncertainty in the rotation period, allowing the mass to be more accurately obtained. We find candidate rotation periods for 17 out of 35 TESS Objects of Interest (TOI) hosting <3R{Earth} planets as part of the Magellan-TESS survey, which is the first-ever statistically robust study of exoplanet masses and radii across the photoevaporation gap. Seven periods are >~3{sigma} detections, two are >~1.5{sigma}, and eight show plausible variability, but the periods remain unconfirmed. The other 18 TOIs are nondetections. Candidate rotators include the host stars of the confirmed planets L168-9b, the HD21749 system, LTT1445Ab, TOI1062b, and the L98-59 system. Thirteen candidates have no counterpart in the 1000 TOI rotation catalog of Canto Martins et al. We find periods for G3-M3 dwarfs using combined light curves from TESS and the Evryscope all-sky array of small telescopes, sometimes with longer periods than would be possible with TESS alone. Secure periods range from 1.4 to 26 days with Evryscope-measured photometric amplitudes as small as 2.1mmag in g' . We also apply Monte Carlo sampling and a Gaussian process stellar activity model from exoplanet to the TESS light curves of six TOIs to confirm the Evryscope periods.
- ID:
- ivo://CDS.VizieR/J/A+A/397/421
- Title:
- r' photometry of Abell 1367 and Coma
- Short Name:
- J/A+A/397/421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide the total r'-band galaxy counts corresponding to our observed fields of the clusters of galaxies Abell 1367 and Coma, as well as the r'-band background counts from Yasuda et al. (2001AJ....122.1104Y). We also provide some basic properties of the galaxies detected in our r'-band survey of the clusters of galaxies Abell 1367 and Coma: coordinates, r'-band magnitudes and surface brightness, position angles, recession velocities and ellipticities are provided. The observations were carried out with the Wide Field Camera (WFC) attached to the Prime Focus of the INT 2.5m located at Observatorio de El Roque de los Muchachos, on 26 and 28 April 2000, under photometric conditions, excepting the last half of the second night.
- ID:
- ivo://CDS.VizieR/J/AJ/151/117
- Title:
- R photometry of (225088) 2007 OR_10_
- Short Name:
- J/AJ/151/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first comprehensive thermal and rotational analysis of the second most distant trans-Neptunian object (TNOs) (225088)2007OR_10_. We combined optical light curves provided by the Kepler Space Telescope-K2 extended mission and thermal infrared data provided by the Herschel Space Observatory. We found that (225088)2007OR_10_ is likely to be larger and darker than derived by earlier studies: we obtained a diameter of d=1535_-225_^+75^km which places (225088) 2007OR_10_ in the biggest top three TNOs. The corresponding visual geometric albedo is p_V_=0.089_-0.009_^+0.031^. The light-curve analysis revealed a slow rotation rate of P_rot_=44.81+/-0.37hr, superseded by very few objects. The most likely light-curve solution is double-peaked with a slight asymmetry; however, we cannot safely rule out the possibility of having a rotation period of P_rot_=22.40+/-0.18hr, which corresponds to a single-peaked solution. Due to the size and slow rotation, the shape of the object should be a MacLaurin ellipsoid, so the light variation should be caused by surface inhomogeneities. Its newly derived larger diameter also implies larger surface gravity and a more likely retention of volatiles--CH_4_, CO, and N_2_--on the surface.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/30
- Title:
- R-Process Alliance: metal-poor star spectroscopy
- Short Name:
- J/ApJS/249/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This compilation is the fourth data release from the R-Process Alliance (RPA) search for r-process-enhanced stars and the second release based on "snapshot" high-resolution (R~30000) spectra collected with the du Pont 2.5m Telescope. In this data release, we propose a new delineation between the r-I and r-II stellar classes at [Eu/Fe]=+0.7, instead of the empirically chosen [Eu/Fe]=+1.0 level previously in use, based on statistical tests of the complete set of RPA data released to date. We also statistically justify the minimum level of [Eu/Fe] for definition of the r-I stars, [Eu/Fe]>+0.3. Redefining the separation between r-I and r-II stars will aid in the analysis of the possible progenitors of these two classes of stars and determine whether these signatures arise from separate astrophysical sources at all. Applying this redefinition to previous RPA data, the number of identified r-II and r-I stars changes to 51 and 121, respectively, from the initial set of data releases published thus far. In this data release, we identify 21 new r-II, 111 new r-I (plus 3 re-identified), and 7 new (plus 1 re-identified) limited-r stars out of a total of 232 target stars, resulting in a total sample of 72 new r-II stars, 232 new r-I stars, and 42 new limited-r stars identified by the RPA to date.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/110
- Title:
- R-Process Alliance: 1st release in Galactic halo
- Short Name:
- J/ApJ/868/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the detailed abundances and r-process classifications of 125 newly identified metal-poor stars as part of an ongoing collaboration, the R-Process Alliance. The stars were identified as metal-poor candidates from the RAdial Velocity Experiment (RAVE) and were followed up at high spectral resolution (R~31500) with the 3.5m telescope at Apache Point Observatory. The atmospheric parameters were determined spectroscopically from FeI lines, taking into account <3D> non-LTE corrections and using differential abundances with respect to a set of standards. Of the 125 new stars, 124 have [Fe/H]{<}-1.5, 105 have [Fe/H]{<}-2.0, and 4 have [Fe/H]{<}-3.0. Nine new carbon-enhanced metal-poor stars have been discovered, three of which are enhanced in r-process elements. Abundances of neutron-capture elements reveal 60 new r-I stars (with +0.3<=[Eu/Fe]<=+1.0 and [Ba/Eu]<0) and 4 new r-II stars (with [Eu/Fe]>+1.0). Nineteen stars are found to exhibit a "limited-r" signature ([Sr/Ba]>+0.5, [Ba/Eu]<0). For the r-II stars, the second- and third-peak main r-process patterns are consistent with the r-process signature in other metal-poor stars and the Sun. The abundances of the light, {alpha}, and Fe-peak elements match those of typical Milky Way (MW) halo stars, except for one r-I star that has high Na and low Mg, characteristic of globular cluster stars. Parallaxes and proper motions from the second Gaia data release yield UVW space velocities for these stars that are consistent with membership in the MW halo. Intriguingly, all r-II and the majority of r-I stars have retrograde orbits, which may indicate an accretion origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/47
- Title:
- RRab stars of Monoceros Ring & A13 overdensities
- Short Name:
- J/ApJ/854/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Monoceros Ring (also known as the Galactic Anticenter Stellar Structure) and A13 are stellar overdensities at estimated heliocentric distances of d~11kpc and 15kpc observed at low Galactic latitudes toward the anticenter of our Galaxy. While these overdensities were initially thought to be remnants of a tidally disrupted satellite galaxy, an alternate scenario is that they are composed of stars from the Milky Way (MW) disk kicked out to their current location due to interactions between a satellite galaxy and the disk. To test this scenario, we study the stellar populations of the Monoceros Ring and A13 by measuring the number of RR Lyrae and M giant stars associated with these overdensities. We obtain low-resolution spectroscopy for RR Lyrae stars in the two structures and measure radial velocities to compare with previously measured velocities for M giant stars in the regions of the Monoceros Ring and A13, to assess the fraction of RR Lyrae to M giant stars (f_RR:MG_) in A13 and Mon/GASS. We perform velocity modeling on 153 RR Lyrae stars (116 in the Monoceros Ring and 37 in A13) and find that both structures have very low f_RR:MG_. The results support a scenario in which stars in A13 and Mon/GASS formed in the MW disk. We discuss a possible association between Mon/GASS, A13, and the Triangulum-Andromeda overdensity based on their similar velocity distributions and f_RR:MG_.
