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- ID:
- ivo://CDS.VizieR/J/A+AS/136/445
- Title:
- CCD observations of Nereid
- Short Name:
- J/A+AS/136/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 229 CCD positions of Nereid taken between 1993 and 1998 are presented. Many of the observations were taken near the periapsis. Considering also the other published positions we have a good distribution of the observations on the eccentric orbit of the satellite. Using a numeric integration method we fitted all these observations in order to determine one state vector for the orbit. The observed minus calculated standard deviation for all observations is 0.23", and for our observations it is 0.16".
- ID:
- ivo://CDS.VizieR/J/A+A/391/767
- Title:
- CCD observations of Phoebe in 1998-1999
- Short Name:
- J/A+A/391/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 1998 and 1999, we started observations of the 9th satellite of Saturn. We made 163 observations using the 120cm-telescope of Observatoire de Haute-Provence, France. We used the USNO A2 catalogue (Cat. <I/252>) of stars for the astrometric reduction. With the help of observations of optical counterparts of ICRF sources, a zonal correction to the USNO A2.0 catalogue was computed and applied to the Phoebe positions. A comparison to the most recent theories was made.
- ID:
- ivo://CDS.VizieR/J/other/SoSyR/45.523
- Title:
- CCD observations of saturnian satellites
- Short Name:
- J/other/SoSyR/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The astrometric positions of seven saturnian satellites are presented. Positions were derived from more then 5000 CCD frames taken with 26-inch Zeiss refractor at Pulkovo from Jan 2008 to may 2009. Astrometric reduction algorithm is based on Turner's method with using UCAC2 catalog as reference one. Observed positions were compared with theoretical ones from TASS 1.7 (Viennel & Duriez, 1995A&A...297..588V). The accuracy is about 0.05 arcsec. Also positions of Saturn were obtained from observations of satellites 2-6.
- ID:
- ivo://CDS.VizieR/J/A+AS/120/107
- Title:
- 1989-1994 CCD observations of Triton
- Short Name:
- J/A+AS/120/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astrometric positions of the Neptunian Satellite Triton are given for the opposition of Neptune for the years 1989 to 1994. These positions where measured on 433 CCD frames obtained at the Cassegrain focus of a 1.6 m reflector. They are compared with theoretical positions calculated from Jacobson et al. (1991A&A...247..565J). The observed minus calculated residuals referred to Neptune have standard deviations of the order of 0.11".
- ID:
- ivo://CDS.VizieR/J/A+A/453/349
- Title:
- CCD positions for eight Jovian irregular satellites
- Short Name:
- J/A+A/453/349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The astrometric positions of eight irregular Jovian satellites are given for the oppositions of the planet from 1995 to 1999. These positions were measured on 204 CCD frames obtained at the Cassegrain focus of a 1.6m reflector. They are compared with the theoretically calculated positions from JPL Development Ephemeris. The observed minus-calculated standard deviation for all observations of the eight satellites are {sigma}_RA_=0.071" and {sigma}_DE_=0.052". The USNO-A2.0 (<I/252>) catalog was used for the astrometric calibration.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/291
- Title:
- 1995-1997 CCD positions of Triton
- Short Name:
- J/A+AS/131/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astrometric observations of Triton are given for the oppositions of Neptune on 1995, 1996 and two nights of 1997. In this period, 759 frames were obtained during 35 nights at the Cassegrain focus of the 1.6m and the 0.6m reflectors of the LNA-Brazil. The comparison with calculated positions gives residuals with standard deviation of the order of 0.09".
- ID:
- ivo://CDS.VizieR/J/A+A/636/A45
- Title:
- CEGM03 model and related gravity anomaly data
- Short Name:
- J/A+A/636/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chinese lunar missions have grown in number over the last ten years, with an increasing focus on radio science investigations. In previous work, we estimated two lunar gravity field models, CEGM01 and CEGM02. The recently lunar mission, Chang'e 5T1, which had an orbital inclination between 18 and 68 degree, and collected orbital tracking data continually for two years, made an improved gravity field model possible. We aimed to estimate a new lunar gravity field model up to degree and order 100, CEGM03, and a new tidal Love number based on the Chang'e 5T1 tracking data combined with the historical tracking data ever used in the solution of CEGM02. The new model makes use of tracking data with this particular inclination, which has not been used in previous gravity field modeling. The solution for this new model was based on our in-house software, LUGREAS. The gravity spectrum power, postfit residuals after precision orbit determination (POD), lunar surface gravity anomalies, correlations between parameters, admittance/coherence with topography model, and accuracy of POD were analyzed to validate the new CEGM03 model. We analyzed the tracking data of the Chang'e 5T1 mission and estimated the CEGM03 lunar gravity field model. We found that the two-way Doppler measurement accuracy reached the 0.2 mm/s with 10 s integration time. The error spectrum shows that the formal error for CEGM03 was at least reduced by about 2 times below the harmonic degree of 20, when compared to the CEGM02 model. The gravity and topography admittance/correlation was also improved when compared to the correlations for the CEGM02 model. The lunar potential Love number k2 was estimated to be 0.02430+/-0.0001 (ten times the formal error). From the model analysis and comparison of the various models, we identified improvements in the CEGM03 model after introducing Chang'e 5T1 tracking data. Moreover, this study illustrates how the low and middle inclination orbits could contribute better accuracy for a low degree of lunar gravity field.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/163
- Title:
- Chandra observations of solar analogs
- Short Name:
- J/ApJ/799/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate whether magnetic interaction between close-in giant planets and their host stars produce observable statistical enhancements in stellar coronal or chromospheric activity. New Chandra observations of 12 nearby (d<60pc) planet-hosting solar analogs are combined with archival Chandra, XMM-Newton, and ROSAT coverage of 11 similar stars to construct a sample inoculated against inherent stellar class and planet-detection biases. Survival analysis and Bayesian regression methods (incorporating both measurements errors and X-ray upper limits; 13/23 stars have secure detections) are used to test whether "hot Jupiter" hosts are systematically more X-ray luminous than comparable stars with more distant or smaller planets. No significant correlations are present between common proxies for interaction strength (M_P_/a^2^ or 1/a) versus coronal activity (L_X_ or L_X_/L_bol_). In contrast, a sample of 198 FGK main-sequence stars does show a significant (~99% confidence) increase in X-ray luminosity with M_P_/a^2^. While selection biases are incontrovertibly present within the main-sequence sample, we demonstrate that the effect is primarily driven by a handful of extreme hot-Jupiter systems with M_P_/a^2^>450M_Jup_AU^-2^, which here are all X-ray luminous but to a degree commensurate with their Ca II H and K activity, in contrast to presented magnetic star-planet interaction scenarios that predict enhancements relatively larger in L_X_. We discuss these results in the context of cumulative tidal spin-up of stars hosting close-in gas giants (potentially followed by planetary infall and destruction). We also test our main-sequence sample for correlations between planetary properties and UV luminosity or Ca II H and K emission, and find no significant dependence.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/L84
- Title:
- Changes in Titan's atmosphere from Cassini
- Short Name:
- J/ApJ/724/L84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a six-year data set (2004-2010) of mid-infrared spectra measured by Cassini's Composite InfraRed Spectrometer to search for seasonal variations in Titan's atmospheric temperature and composition. During most of Cassini's mission Titan's northern hemisphere has been in winter, with an intense stratospheric polar vortex highly enriched in trace gases, and a single south-to-north circulation cell. Following northern spring equinox in mid-2009, dramatic changes in atmospheric temperature and composition were expected, but until now the temporal coverage of polar latitudes has been too sparse to discern trends. Here, we show that during equinox and post-equinox periods, abundances of trace gases at both poles have begun to increase. We propose that increases in north polar trace gases are due to a seasonal reduction in gas depletion by horizontal mixing across the vortex boundary. A simultaneous south polar abundance increase suggests that Titan is now entering, or is about to enter, a transitional circulation regime with two branches, rather than the single branch circulation pattern previously observed.
