- ID:
- ivo://CDS.VizieR/J/AJ/158/59
- Title:
- Autoregressive planet search: irregular time series
- Short Name:
- J/AJ/158/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive signal processing methods are needed to detect transiting planets from ground-based photometric surveys. Caceres et al. (2019AJ....158...58C) show that the autoregressive planet search (ARPS) method - a combination of autoregressive integrated moving average (ARIMA) parametric modeling, a new transit comb filter (TCF) periodogram, and machine learning classification - is effective when applied to evenly spaced light curves from space-based missions. We investigate here whether ARIMA and TCF will be effective for ground-based survey light curves that are often sparsely sampled with high noise levels from atmospheric and instrumental conditions. The ARPS procedure is applied to selected light curves with strong planetary signals from the Kepler mission that have been altered to simulate the conditions of ground-based exoplanet surveys. Typical irregular cadence patterns are used from the Hungarian-made Automated Telescope Network-South (HATSouth) survey. We also evaluate recovery of known planets from HATSouth. Simulations test transit signal recovery as a function of cadence pattern and duration, stellar magnitude, planet orbital period, and transit depth. Detection rates improve for shorter periods and deeper transits. The study predicts that the ARPS methodology will detect planets with >~0.1% transit depth and periods ~<40 days in HATSouth stars brighter than ~15 mag. ARPS methodology is therefore promising for planet discovery from ground-based exoplanet surveys with sufficiently dense cadence patterns.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/444/305
- Title:
- A-values + oscillator strength of Ca XIII
- Short Name:
- J/A+A/444/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ca XIII. The configurations used are 2s2.2p4, 2s.2p5, 2p6, 2s2.2p3.3s, 2s2.2p3.3p and 2s2.2p3.3d giving rise to 86 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies (40, 80, 120, 160 and 200Ry) in the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10^8-10^14cm^-3 at an electron temperature of logTe(K)=6.5, corresponding to maximum abundance of Ca XIII. Relative and absolute spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.
- ID:
- ivo://CDS.VizieR/J/A+A/434/365
- Title:
- A-values & oscillator strength of O-like ions
- Short Name:
- J/A+A/434/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present work a complete set of radiative transition rates is calculated for all for the O-like ions with Z=11-30. Energy levels, oscillator strengths and A values are computed for all transitions within the n=2 complex and are compared with previous calculations, where available. Calculations are carried out using the Superstructure code. The present work provides for the first time a self-consistent, complete set of A values necessary for the calculation of line emissivities and synthetic spectra for all the ions considered, filling several gaps in the existing literature. The present data are especially suited for the analysis of spectral lines emitted by the less-abundant elements in the universe, for which few if any data were available in the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/142/114
- Title:
- A variable star census in a Perseus field
- Short Name:
- J/AJ/142/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Berlin Exoplanet Search Telescope is a small-aperture, wide-field telescope dedicated to time-series photometric observations. During an initial commissioning phase at the Thueringer Landessternwarte Tautenburg, Germany, and subsequent operations at the Observatoire de Haute-Provence, France, a 10{deg}^2^ circumpolar field close to the galactic plane centered at (RA, DE) = (02:39:23, +52:01:46) (J2000.0) was observed between 2001 August and 2006 December during 52 nights. From the 32129 stars observed, a subsample of 145 stars with clear stellar variability was detected out of which 125 are newly identified variable objects. For five bright objects, the system parameters were derived by modeling the light curve.
- ID:
- ivo://CDS.VizieR/VI/133
- Title:
- A variationally computed hot NH3 line list - BYTe
- Short Name:
- VI/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 'BYTe' a comprehensive 'hot' line list of ro-vibrational transitions of ammonia, ^14^NH_3_, in its ground electronic state. It comprises 1,138,323,351 transitions with frequencies up to 12,000cm^-1^, constructed from 1,373,897 energy levels below 18,000cm^-1^ having J values less than 37. The line list is sufficiently accurate and complete for high resolution spectroscopy and atmospheric modelling of astrophysical objects, including brown dwarfs and exoplanets at temperatures up to 1,500K. The data are in two parts. The first, nh3_0-41.dat contains a list of 4,167,360 rovibrational states, ordered by J (max= 41), symmetry block and energy (in cm^-1^). Only one third of the states (1,373,897) are within the parameters used for generating transitions (see above), but all the states are required for computing temperature-dependent partition functions. Each state is labelled with: seven normal mode vibrational quantum numbers; three rotational quantum numbers and the total symmetry quantum number, Gamma. In addition there are six local mode vibrational numbers and a local mode vibrational symmetry quantum numbers, which we include because the basis set used in our calculations is expressed in terms of these local mode quantum numbers. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm^-1^ frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm^-1^. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, sp_byte.f90 which may be used to generate synthetic spectra (see sp_byte.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Three sample input files for use with sp_byte.f90 are supplied: "stick300.in", "gauss300.in", and "sp08900.in" (generates a spectrum for 8900-9000cm^-1^).
- ID:
- ivo://CDS.VizieR/V/88
- Title:
- Averaged [Fe/H] for Cool Dwarfs
- Short Name:
- V/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This file contains mean values of [Fe/H] (with rms errors) for 495 F-K stars which are on or near the main sequence. Literature references are given for the contributing values of [Fe/H].
- ID:
- ivo://CDS.VizieR/III/161
- Title:
- Averaged Stellar Radial Velocities
- Short Name:
- III/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains means of measurements of radial velocities of galactic stars. The data supplement the catalogs of Wilson (1953) <III/21> and Evans (1978) <III/47> with observations published through December 1980. There are new mean velocities for 6023 stars with new radial velocity data; more than 4500 of these stars are not in the earlier catalogs. A weighting scheme was used to form the mean velocities with data from cross-correlation spectrometers given highest weight and low dispersion (less than 100 A/mm) spectra given lowest weight. No systematic zero-point corrections were made but observations were taken from the literature only if they were standardized to the IAU or Wilson (1953) systems.
- ID:
- ivo://CDS.VizieR/J/A+A/497/41
- Title:
- Average Early-type galaxies NIR spectrum
- Short Name:
- J/A+A/497/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared (hereafter NIR) data may provide complementary information to the traditional optical population synthesis analysis of unresolved stellar populations because the spectral energy distribution of the galaxies in the 1-2.5um range is dominated by different types of stars than at optical wavelengths. Furthermore, NIR data are less affected by dust absorption and hence could constrain the stellar populations in dust-obscured galaxies. We attempt to develop observational constraints on the stellar populations of unresolved stellar systems in the NIR.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A42
- Title:
- Average spectrum of HD 140283 (370-1040nm)
- Short Name:
- J/A+A/548/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 140283 is a nearby (V=7.7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. The detection of europium proves that the neutron-capture elements in this star are originate in the r-process, and not in the s-process, as recently claimed in the literature. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines 4129{AA} and 4205{AA}, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81000 and a S/N ratio of 800 at 4100{AA}. We were able to determine the abundance A(Eu)=-2.35dex, compatible with the value predicted for the europium from the r-process. The abundance ratio [Eu/Ba]=+0.58dex agrees with the trend observed in metal-poor stars and is also compatible with a strong r-process contribution to the origin of the neutron-capture elements in HD 140283.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A94
- Title:
- Avg pitch angles & spiral amplitudes in S4G
- Short Name:
- J/A+A/631/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spiral galaxies are very common in the local Universe, but their formation, evolution, and interplay with bars remain poorly understood after more than a century of astronomical research on the topic. We use a sample of 391 nearby galaxies from the S4G survey to characterise the winding angle and amplitude of spiral arms as a function of disc properties, such as bar strength, in all kinds of spirals (grand-design, multi-armed, and flocculent). We derived global pitch angles in 3.6um de-projected images from i) average measurements of individual logarithmic spiral segments, and ii) for a subsample of 32 galaxies, from 2-D Fourier analyses. The strength of spirals was quantified from the tangential-to-radial force ratio and from the normalised m=2 Fourier density amplitudes. In galaxies with more than one measured logarithmic segment, the spiral pitch angle varies on average by ~10{deg} between segments, but by up to >=15-20{deg}. The distribution of the global pitch angle versus Hubble type (T) is very similar for barred and non-barred galaxies when 1<=T<=5. Most spiral galaxies (>90%) are barred for T>5. The pitch angle is not correlated with bar strength, and only weakly with spiral strength. The amplitude of spirals is correlated with bar strength (and less tightly, with bar length) for all types of spirals. The mean pitch angle is hardly correlated with the mass of the supermassive black hole (estimated from central stellar velocity dispersion), with central stellar mass concentration, or with shear, questioning previous results in the literature using smaller samples. We do not find observational evidence that spiral arms are driven by stellar bars or by invariant manifolds. Most likely, discs that are prone to the development of strong bars are also reactive to the formation of prominent spirals, explaining the observed coupling between bar and spiral amplitudes.
