- ID:
- ivo://CDS.VizieR/J/ApJS/99/173
- Title:
- Synthetic UV spectra of massive stars
- Short Name:
- J/ApJS/99/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An atlas of synthetic ultraviolet spectra of a population of massive stars is presented. The spectra are based on a stellar library of IUE high-dispersion spectra of O and Wolf-Rayet stars, coupled to an evolutionary synthesis code. Later spectral types are included via low-dispersion spectra. Line profiles of N V lambda 1240, Si IV lambda 1400, C IV lambda 1550, He II lambda 1640, and N IV lambda 1720 have been computed for star-formation histories and initial mass functions typically found in starburst regions. It is found that the lines are sensitive indicators for the presence or absence of massive stars. C IV lambda 1550 is the strongest stellar line in the ultraviolet spectrum of a typical starburst. If O stars with zero-age main-sequence masses above 50M_{sun}_ are present, C IV always shows a P Cygni profile. In the absence of such stars, only a blue-shifted absorption is present. During later epochs of the starburst, when late-O/early-B stars dominate, an unshifted photospheric absorption appears. Si IV lambda 1400 shows a conspicuous wind profile when luminous O supergiants are present. A strong P Cygni profile is found only for an instantaneous burst observed at 3 to 5Myr, which has a top-heavy IMF. The velocity of the blueshifted absorption is strongly correlated with the age and the upper cutoff mass (or slope) of the IMF. N V lambda 1240 traces the most massive stars and behaves rather similar to Si IV lambda 1400. Its usefulness as an indicator of very massive stars is limited due to the strong blending effect of the nearby Ly-alpha line. Nevertheless, strong N V lambda 1240 emission in a starburst suggests the presence of stars with masses in excess of 60M_{sun}_. He II lambda 1640 and N IV lambda 1720 are produced by very hot and luminous O and Wolf-Rayet stars. Both lines can have weak absorption or emission in a typical starburst but are predicted to be observable only under rare circumstances, such as in an instantaneous burst at t{approx.}3Myr. The profiles presented in the atlas can be compared to high-quality ultraviolet observations of galaxies with active star formation in order to constrain the massive star population. The atlas is published in its entirety in computer-readable form in the AAS CD-ROM series, Vol. 5.
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- ID:
- ivo://CDS.VizieR/J/A+A/650/A73
- Title:
- Synthetic XUV spectra of GJ 3470
- Short Name:
- J/A+A/650/A73
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Neptune-size exoplanets seem particularly sensitive to atmospheric evaporation, making it essential to characterize the stellar high-energy radiation that drives this mechanism. This is particularly important with M dwarfs, which emit a large and variable fraction of their luminosity in the ultraviolet and can display strong flaring behavior. The warm Neptune GJ 3470b, hosted by an M2 dwarf, was found to harbor a giant exosphere of neutral hydrogen thanks to three transits observed with the Hubble Space Telescope Imaging Spectrograph (HST/STIS). Here we report on three additional transit observations from the Panchromatic Comparative Exoplanet Treasury program, obtained with the HST Cosmic Origin Spectrograph. These data confirm the absorption signature from GJ 3470b's exosphere in the stellar Lyman-{alpha} line and demonstrate its stability over time. No planetary signatures are detected in other stellar lines, setting a 3{sigma} limit on GJ 3470b's far-ultraviolet (FUV) radius at 1.3 times its Roche lobe radius. We detect three flares from GJ 3470. They show different spectral energy distributions but peak consistently in the SiIII line, which traces intermediate-temperature layers in the transition region. These layers appear to play a particular role in GJ 3470's activity as emission lines that form at lower or higher temperatures than SiIII evolved differently over the long term. Based on the measured emission lines, we derive synthetic X-ray and extreme-ultraviolet (X+EUV, or XUV) spectra for the six observed quiescent phases, covering one year, as well as for the three flaring episodes. Our results suggest that most of GJ 3470's quiescent high-energy emission comes from the EUV domain, with flares amplifying the FUV emission more strongly. The neutral hydrogen photoionization lifetimes and mass loss derived for GJ 3470b show little variation over the epochs, in agreement with the stability of the exosphere. Simulations informed by our XUV spectra are required to understand the atmospheric structure and evolution of GJ 3470b and the role played by evaporation in the formation of the hot-Neptune desert.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A111
- Title:
- Systematic diff. in spectroscopic analysis
- Short Name:
- J/A+A/622/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectroscopic analysis of stellar spectra can be carried out using multiple approaches such as different methods, line lists, atmospheric models, atomic parameters, and solar abundances. The resulting atmospheric parameters from these choices can vary beyond the quoted uncertainties in the literature. We characterize these differences by systematically comparing some of the commonly adopted ingredients such as line lists, equivalent width measurements, and atomic parameters. High-resolution and high signal-to-noise (S/N) spectroscopic data of one helium-core-burning red giant star in each of the three open clusters, NGC 6819, M67, and NGC 188 were obtained with the FIES spectrograph at the Nordic Optical Telescope. The M67 target was used to benchmark the analysis, as it is a well-studied cluster with asteroseismic data from the K2 mission. For the other two clusters we obtained higher quality data than had been analyzed before, which allows us to establish their chemical composition more securely. Using a line by line analysis, we tested several different combinations of line lists and programs to measure equivalent widths of stellar absorption lines to characterize systematic differences within the same spectroscopic method. The obtained parameters for the benchmark star in M67 vary up to ~170K in effective temperature, ~0.4dex in logg and ~0.25dex in [Fe/H] between the tested setups. Using the combination of an equivalent width measurement program and line list that best reproduce the inferred surface gravity from asteroseismology, we determined the atmospheric parameters for the three stars and securely established the chemical composition of NGC 6819 to be close to solar, [Fe/H]=-0.02+/-0.01dex. We highlighted the significantly different results obtained with different combinations of line lists, programs, and atomic parameters. The results emphasize the importance of benchmark stars studied with several methods to anchor spectroscopic analyses.
- ID:
- ivo://CDS.VizieR/J/AJ/162/163
- Title:
- Systematic KMTNet Planetary Anomaly Search. I.
- Short Name:
- J/AJ/162/163
- Date:
- 14 Mar 2022 06:36:47
- Publisher:
- CDS
- Description:
- In order to exhume the buried signatures of "missing planetary caustics" in Korea Microlensing Telescope Network (KMTNet) data, we conducted a systematic anomaly search of the residuals from point-source point-lens fits, based on a modified version of the KMTNet EventFinder algorithm. This search revealed the lowest-mass-ratio planetary caustic to date in the microlensing event OGLE-2019-BLG-1053, for which the planetary signal had not been noticed before. The planetary system has a planet-host mass ratio of q=(1.25{+/-}0.13)x10^-5^. A Bayesian analysis yielded estimates of the mass of the host star, M_host_=0.61_-0.24_^+0.29^M{sun}, the mass of its planet, M_planet_=2.48_-0.98_^+1.19^M{Earth}, the projected planet-host separation, a_perp_=3.4_-0.5_^+0.5^au, and the lens distance, D_L_=6.8_-0.9_^+0.6^kpc. The discovery of this very-low-mass-ratio planet illustrates the utility of our method and opens a new window for a large and homogeneous sample to study the microlensing planet-host mass ratio function down to q~10^-5^.
- ID:
- ivo://CDS.VizieR/J/A+A/477/67
- Title:
- Systematic search for M31 novae from Schmidt plates
- Short Name:
- J/A+A/477/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the detection of optical novae in our neighbour galaxy M 31 based on digitized historical Tautenburg Schmidt plates. The accurate positions of the detected novae lead to a much larger database when searching for recurrent novae in M 31. We conducted a systematic search for novae on 306 digitized Tautenburg Schmidt plates covering a time span of 36 years from 1960 to 1996. From the database of both ~3x10^5^ light curves and >~10^6^ detections on only one plate per colour band, nova candidates were efficiently selected by automated algorithms and subsequently individually inspected by eye. We report the detection of 84 nova candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A118
- Title:
- Systematic survey of wind mass loss
- Short Name:
- J/A+A/603/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mass loss processes are a key uncertainty in the evolution of massive stars. They determine the amount of mass and angular momentum retained by the star, thus influencing its evolution and presupernova structure. Because of the high complexity of the physical processes driving mass loss, stellar evolution calculations must employ parametric algorithms, and usually only include wind mass loss. We carried out an extensive parameter study of wind mass loss and its effects on massive star evolution using the open-source stellar evolution code MESA. We provide a systematic comparison of wind mass loss algorithms for solar-metallicity, nonrotating, single stars in the initial mass range of 15M_{sun}_ to 35M_{sun}_. We consider combinations drawn from two hot phase (i.e., roughly the main sequence) algorithms, three cool phase (i.e., post-main-sequence) algorithms, and two Wolf-Rayet mass loss algorithms. We discuss separately the effects of mass loss in each of these phases. In addition, we consider linear wind efficiency scale factors of 1, 0.33, and 0.1 to account for suggested reductions in mass loss rates due to wind inhomogeneities. We find that the initial to final mass mapping for each zero-age main-sequence (ZAMS) mass has a ~50% uncertainty if all algorithm combinations and wind efficiencies are considered. The ad-hoc efficiency scale factor dominates this uncertainty. While the final total mass and internal structure of our models vary tremendously with mass loss treatment, final luminosity and effective temperature are much less sensitive for stars with ZAMS mass <=30M_{sun}_. This indicates that uncertainty in wind mass loss does not negatively affect estimates of the ZAMS mass of most single-star supernova progenitors from pre-explosion observations. Our results furthermore show that the internal structure of presupernova stars is sensitive to variations in both main sequence and post main-sequence mass loss. The compactness parameter {xi}{prop.to}M/R(M) has been identified as a proxy for the "explodability" of a given presupernova model. We find that {xi} varies by as much as 30% for models of the same ZAMS mass evolved with different wind efficiencies and mass loss algorithm combinations. This suggests that the details of the mass loss treatment might bias the outcome of detailed core-collapse supernova calculations and the predictions for neutron star and black hole formation.
21357. System IMF of 25 Ori
- ID:
- ivo://CDS.VizieR/J/MNRAS/486/1718
- Title:
- System IMF of 25 Ori
- Short Name:
- J/MNRAS/486/1718
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar initial mass function (IMF) is an essential input for many astrophysical studies but only in a few cases has it been determined over the whole cluster mass range, limiting the conclusions about its nature. The 25 Orionis group (25 Ori) is an excellent laboratory for investigating the IMF across the entire mass range of the population, from planetary-mass objects to intermediate/high-mass stars. We combine new deep optical photometry with optical and near-infrared data from the literature to select 1687 member candidates covering a 1.1{deg} radius area in 25 Ori. With this sample we derived the 25 Ori system IMF from 0.012 to 13.1M_{sun}_. This system IMF is well described by a two-segment power law with {GAMMA}=-0.74+/-0.04 for m<0.4M_{sun}_ and {GAMMA}=1.50+/-0.11 for m>=0.4M_{sun}_. It is also well described over the whole mass range by a tapered power-law function with {GAMMA}=1.10+/-0.09, mp=0.31+/-0.03 and {beta}=2.11+/-0.09. The best lognormal representation of the system IMF has mc=0.31+/-0.04 and {sigma}=0.46+/-0.05 for m<1M_{sun}_. This system IMF does not present significant variations with the radii. We compared the resultant system IMF as well as the brown dwarf/star ratio of 0.16+/-0.03 that we estimated for 25 Ori with that of other stellar regions with diverse conditions and found no significant discrepancies. These results support the idea that general star-formation mechanisms are probably not strongly dependent on environmental conditions. We found that the substellar and stellar objects in 25 Ori do not have any preferential spatial distributions and confirmed that 25 Ori is a gravitationally unbound stellar association.
- ID:
- ivo://CDS.VizieR/J/A+A/445/819
- Title:
- Systems of galaxies in Shapley supercluster
- Short Name:
- J/A+A/445/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the largest compilation of galaxies with redshift in the region of the Shapley Supercluster (Proust et al., 2004 in prep., 2006A&A...447..133P), we identified 122 galaxy systems, 60 of which are new systems. Using the SuperCOSMOS catalogue, we have assigned b_j_ magnitudes to each galaxy in our compilation. The sample of galaxy systems was used to estimate the mass function of systems in the range 10^13^ to 10^15^M_{sun}/h^-1^. We computed a lower value to the total mass in the region of the Shapley Supercluster with this mass function. Using 15 mock catalogues we derived the mean mass that these kinds of systems have before comparing it with that obtained from the real data.
21359. SZCLUSTER-DB IDOC
- ID:
- ivo://idoc.ginco/szcluster-db
- Title:
- SZCLUSTER-DB IDOC
- Short Name:
- SZCLUSTER-DB
- Date:
- 10 Jan 2015 20:00:00
- Publisher:
- IDOC GINCO
- Description:
- This database provides access to IDOC catalogues and complementary information on clusters of galaxies observed through the Sunyaev-Zeldovich (SZ) effect.
21360. SZ Her BVRI light curves
- ID:
- ivo://CDS.VizieR/J/AJ/143/34
- Title:
- SZ Her BVRI light curves
- Short Name:
- J/AJ/143/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis presented in this paper indicates that the eclipsing binary is a classical Algol-type system with parameters of q=0.472, i=87.57{deg}, and {Delta}(T_1_-T_2_)=2381K; the primary component fills approximately 77% of its limiting lobe and is slightly larger than the lobe-filling secondary component. More than 1100 times of minimum light spanning more than a century were used to study an orbital behavior of the binary system. It was found that the orbital period of SZ Her varied due to a combination of two periodic variations with cycle lengths of P_3_=85.8yr and P_4_=42.5yr and semi-amplitudes of K_3_=0.013days and K_4_=0.007days, respectively. The most reasonable explanation for these variations is a pair of light-time effects driven by the possible existence of two M-type companions with minimum masses of M_3_=0.22M_{sun}_ and M_4_=0.19M_{sun}_ that are located close to the 2:1 mean motion resonance. If two additional bodies exist, then the overall dynamics of the multiple system may provide a significant clue to the formation and evolution of the eclipsing pair.
