- ID:
- ivo://CDS.VizieR/J/AJ/154/4
- Title:
- Times of transits and occultations of WASP-12b
- Short Name:
- J/AJ/154/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: P.=-29+/-3ms/yr and P/P.=3.2Myr. However, it is difficult to tell whether we have observed orbital decay or a portion of a 14-year apsidal precession cycle. If interpreted as decay, the star's tidal quality parameter Q_star_ is about 2*10^5^. If interpreted as precession, the planet's Love number is 0.44+/-0.10. Orbital decay appears to be the more parsimonious model: it is favored by {Delta}_{chi}^2^_=5.5 despite having two fewer free parameters than the precession model. The decay model implies that WASP-12 was discovered within the final ~0.2% of its existence, which is an unlikely coincidence but harmonizes with independent evidence that the planet is nearing disruption. Precession does not invoke any temporal coincidence, but it does require some mechanism to maintain an eccentricity of {approx}0.002 in the face of rapid tidal circularization. To distinguish unequivocally between decay and precession will probably require a few more years of monitoring. Particularly helpful will be occultation timing in 2019 and thereafter.
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- ID:
- ivo://CDS.VizieR/J/ApJ/871/244
- Title:
- Times of X-ray minima & orbit numbers of Cyg X-3
- Short Name:
- J/ApJ/871/244
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using available archival X-ray data, we significantly extended the list of times of X-ray minima. The new list includes 65 data points obtained by critically reanalyzing RXTE ASM data, 88 data points based on observations by MAXI, and 2 data points based on observations by SUZAKU and AstroSat. Analyzing the data along with times of X-ray minima available from the literature, we provide the most accurate estimate of the rate of period change to date. We do not confirm the existence of a second derivative of the orbital period suggested by some authors earlier. Instead, we find that the changes in the period can be fit by a sum of quadratic and sinusoidal functions. The period of sinusoidal variations is 15.79yr. They can be related either to apsidal motion in the close binary with eccentricity e~0.03 or to the presence of a third body with a mass of about 0.7M_{sun}_ located at a distance ~16 au from the close binary.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A122
- Title:
- Time stability of the ICRF2 axes
- Short Name:
- J/A+A/553/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I assess the astrometric stability of the 295 defining sources of the current best realization of the International Celestial Reference System (ICRS): the second realization of the International Celestial Reference Frame (ICRF2), constructed and published in 2009 after the analysis of millions of VLBI observations at 2 and 8 GHz between 1979.6 and 2009.2. I also assess the time evolution of the ICRF2 axis stability. I derived coordinate time series of hundreds of quasars monitored by the regular geodetic VLBI program of the International VLBI Service for Geodesy and Astrometry (IVS). The axis stability was studied by constructing annual reference frames based on the ICRF2 defining sources. The time variable frame stability was obtained by computing the deformation parameters that lead from one frame to the next. I show that, although the astrometric stability of some of the ICRF2 defining sources has slightly degraded since 2009.2, the ensemble still constitutes a very stable reference frame. The current estimation of the axis stability over 1979.6-2013.1 remains at the same level as the one estimated over 1979.6-2009.2, i.e., on the order of 20uas for each axis.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/1
- Title:
- Timing data for the classical Cepheid l Car
- Short Name:
- J/ApJ/824/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M>=8M_{sun}_) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for {delta} Cephei. We find that the mass of l Car is about 8-10M_{sun}_. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for {delta} Cep and {beta} Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/128
- Title:
- Timing noise & astrometry of Fermi-LAT pulsars
- Short Name:
- J/ApJ/814/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have constructed timing solutions for 81 {gamma}-ray pulsars covering more than five years of Fermi data. The sample includes 37 radio-quiet or radio-faint pulsars which cannot be timed with other telescopes. These timing solutions and the corresponding pulse times of arrival are prerequisites for further study, e.g., phase-resolved spectroscopy or searches for mode switches. Many {gamma}-ray pulsars are strongly affected by timing noise (TN), and we present a new method for characterizing the noise process and mitigating its effects on other facets of the timing model. We present an analysis of TN over the population using a new metric for characterizing its strength and spectral shape, namely, its time-domain correlation. The dependence of the strength on {nu} and {dot}{nu} is in good agreement with previous studies. We find that noise process power spectra S(f) for unrecycled pulsars are steep, with strong correlations over our entire data set and spectral indices s(f){propto}f^-{alpha}^ of {alpha}~5-9. One possible explanation for these results is the occurrence of unmodeled, episodic "microglitches". Finally, we show that our treatment of TN results in robust parameter estimation, and in particular we measure a precise timing position for each pulsar. We extensively validate our results with multi-wavelength astrometry, and using our updated position, we firmly identify the X-ray counterpart of PSR J1418-6058.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A116
- Title:
- Titan middle atmosphere thermal field
- Short Name:
- J/A+A/641/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the seasonal evolution of Titan's thermal field and distributions of haze, C_2_H_2_, C_2_H_4_, C_2_H_6_, CH_3_C_2_H, C_3_H_8_, C_4_H_2_, C_6_H_6_, HCN, and HC_3_N from March 2015 (Ls=66{deg}) to September 2017 (Ls=93{deg}) (i.e., from the last third of northern spring to early summer). We analyzed thermal emission of Titan's atmosphere acquired by the Cassini Composite Infrared Spectrometer (CIRS) with limb and nadir geometry to retrieve the stratospheric and mesospheric temperature and mixing ratios pole-to-pole meridional cross sections from 5mbar to 50ubar (120-650km). The southern stratopause varied in a complex way and showed a global temperature increase from 2015 to 2017 at high-southern latitudes. Stratospheric southern polar temperatures, which were observed to be as low as 120K in early 2015 due to the polar night, showed a 30K increase (at 0.5mbar) from March 2015 to May 2017 due to adiabatic heating in the subsiding branch of the global overturning circulation. All photochemical compounds were enriched at the south pole by this subsidence. Polar cross sections of these enhanced species, which are good tracers of the global dynamics, highlighted changes in the structure of the southern polar vortex. These high enhancements combined with the unusually low temperatures (<120K) of the deep stratosphere resulted in condensation at the south pole between 0.1 and 0.03mbar (240-280km) of HCN, HC_3_N, C_6_H_6_ and possibly C4H2 in March 2015 (Ls=66{deg}). These molecules were observed to condense deeper with increasing distance from the south pole. At high-northern latitudes, stratospheric enrichments remaining from the winter were observed below 300km between 2015 and May 2017 (Ls=90{deg}) for all chemical compounds and up to September 2017 (Ls=93{deg}) for C_2_H_2_, C_2_H_4_, CH_3_C_2_H, C_3_H_8_, and C_4_H_2_. In September 2017, these local enhancements were less pronounced than earlier for C_2_H_2_, C_4_H_2_, CH_3_C_2_H, HC_3_N, and HCN, and were no longer observed for C_2_H_6_ and C_6_H_6_, which suggests a change in the northern polar dynamics near the summer solstice. These enhancements observed during the entire spring may be due to confinement of this enriched air by a small remaining winter circulation cell that persisted in the low stratosphere up to the northern summer solstice, according to predictions of the Institut Pierre Simon Laplace Titan Global Climate Model (IPSL Titan GCM). In the mesosphere we derived a depleted layer in C_2_H_2_, HCN, and C_2_H_6_ from the north pole to mid-southern latitudes, while C_4_H_2_, C_3_H_4_, C_2_H_4_, and HC_3_N seem to have been enriched in the same region. In the deep stratosphere, all molecules except C_2_H_4_ were depleted due to their condensation sink located deeper than 5mbar outside the southern polar vortex. HCN, C_4_H_2_, and CH_3_C_2_H volume mixing ratio (VMR) cross section contours showed steep slopes near the mid-latitudes or close to the equator, which can be explained by upwelling air in this region. Upwelling is also supported by the cross section of the C_2_H_4_ (the only molecule not condensing among those studied here) volume mixing ratio observed in the northern hemisphere. We derived the zonal wind velocity up to mesospheric levels from the retrieved thermal field. We show that zonal winds were faster and more confined around the south pole in 2015 (Ls=67-72{deg}) than later. In 2016, the polar zonal wind speed decreased while the fastest winds had migrated toward low-southern latitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A194
- Title:
- Titans metal-poor reference stars. I.
- Short Name:
- J/A+A/650/A194
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Several large stellar spectroscopic surveys are producing overwhelming amounts of data that can be used for determining stellar atmospheric parameters and chemical abundances. Nonetheless, the accuracy achieved in the derived astrophysical parameters is still insufficient, mainly because of the paucity of adequate calibrators, particularly in the metal-poor regime ([Fe/H]<=-1.0). Our aim is to increase the number of metal-poor stellar calibrators that have accurate parameters. Here, we introduce the Titans metal-poor reference stars: a sample of 41 dwarf and subgiant stars with accurate, but model-dependent, parameters. Effective temperatures (Teff) were derived by fitting observed H{alpha} profiles with synthetic lines computed using three dimensional (3D) hydrodynamic model atmospheres that take into account departures from the local thermodynamic equilibrium (non-LTE effects). Surface gravities (logg) were computed using evolutionary tracks and parallaxes from Gaia early-data release 3. The same methods recover the Teff values of the Gaia benchmark stars, which are mostly based on interferometric measurements, with a 1{sigma} dispersion of 50K. We assume this to be the accuracy of the H{alpha} profiles computed from 3D non-LTE models for metal-poor dwarfs and subgiants, although this is likely an upper-bound estimate dominated by the uncertainty of the standard Teff values. We achieved an internal precision typically between 30-40K, these errors dominated by instrumental effects. The final total uncertainty for the Teff values of the Titans are thus estimated to be of the order of 1%. The typical error for logg is 0.04dex. In addition, we identified a few members of Gaia-Enceladus, of Sequoia, and of the Helmi stream in our sample. These stars can pave the way for the accurate chemical characterization of these Galactic substructures. Using the Titans as reference, large stellar surveys will be able to improve the internal calibration of their astrophysical parameters. Ultimately, this sample will help users of data from Gaia and large surveys in reaching their goal of redefining our understanding of stars, stellar systems, and the Milky Way.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/3608
- Title:
- Titius-Bode-based exoplanet predictions
- Short Name:
- J/MNRAS/448/3608
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse a sample of multiple-exoplanet systems which contain at least three transiting planets detected by the Kepler mission ('Kepler multiples'). We use a generalized Titius-Bode relation to predict the periods of 228 additional planets in 151 of these Kepler multiples. These Titius-Bode-based predictions suggest that there are, on average, 2+/-1 planets in the habitable zone of each star. We estimate the inclination of the invariable plane for each system and prioritize our planet predictions by their geometric probability to transit. We highlight a short list of 77 predicted planets in 40 systems with a high geometric probability to transit, resulting in an expected detection rate of ~15%, ~3 times higher than the detection rate of our previous Titius-Bode-based predictions.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3121
- Title:
- TKRS catalog of GOODS-North Field
- Short Name:
- J/AJ/127/3121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an extensive imaging and spectroscopic survey in the Great Observatories Origins Deep Survey (GOODS)-North field completed using DEIMOS on the Keck II telescope. Observations of 2018 targets in a magnitude-limited sample of 2911 objects to R_AB_=24.4 yield secure redshifts for a sample of 1440 galaxies and active galactic nuclei (AGNs) plus 96 stars. In addition to redshifts and associated quality assessments, our catalog also includes photometric and astrometric measurements for all targets detected in our R-band imaging survey of the GOODS-North region.
21210. TKRS/GOODS-N Field galaxies
- ID:
- ivo://CDS.VizieR/J/ApJ/653/1027
- Title:
- TKRS/GOODS-N Field galaxies
- Short Name:
- J/ApJ/653/1027
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present kinematic measurements of a large sample of galaxies from the Team Keck Redshift Survey in the GOODS-N field. We measure line-of-sight velocity dispersions from integrated emission for 1089 galaxies with median redshift 0.637 and spatially resolved kinematics for a subsample of 380 galaxies. This is the largest sample of galaxies to z~1 with kinematics to date and allows us to measure kinematic properties without morphological pre-selection. Emission-line widths provide a dynamical measurement for the bulk of blue galaxies. To fit the spatially resolved kinematics, we construct models that fit both line-of-sight rotation amplitude and velocity dispersion. Integrated line width correlates well with a combination of the velocity gradient and dispersion and is a robust measure of galaxy kinematics.
