- ID:
- ivo://CDS.VizieR/J/AJ/155/177
- Title:
- Obliquities of planetary & eclipsing binary systems
- Short Name:
- J/AJ/155/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity {Psi} of the eclipsed star. Here we present a method for detecting and analyzing these patterns, based on a statistical test for correlations between the anomalies observed in a sequence of eclipses. Compared to previous methods, ours makes fewer assumptions and is easier to automate. We apply it to a sample of 64 stars with transiting planets and 24 eclipsing binaries for which precise space-based data are available, and for which there was either some indication of flux anomalies or a previously reported obliquity measurement. We were able to determine obliquities for 10 stars with hot Jupiters. In particular we found {Psi}~<10{deg} for Kepler-45, which is only the second M dwarf with a measured obliquity. The other eight cases are G and K stars with low obliquities. Among the eclipsing binaries, we were able to determine obliquities in eight cases, all of which are consistent with zero. Our results also reveal some common patterns of stellar activity for magnetically active G and K stars, including persistently active longitudes.
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- ID:
- ivo://CDS.VizieR/J/AJ/161/164
- Title:
- Observation of 186 TESS stars with NESSI (WYIN)
- Short Name:
- J/AJ/161/164
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- We present high-resolution speckle interferometric imaging observations of TESS exoplanet host stars using the NN-EXPLORE Exoplanet and Stellar Speckle Imager instrument at the 3.5m WIYN telescope. Eight TESS objects of interest that were originally discovered by Kepler were previously observed using the Differential Speckle Survey Instrument. Speckle observations of 186 TESS stars were carried out, and 45 (24%) likely bound companions were detected. This is approximately the number of companions we would expect to observe given the established 46% binarity rate in exoplanet host stars. For the detected binaries, the distribution of stellar mass ratio is consistent with that of the standard Raghavan distribution and may show a decrease in high-q systems as the binary separation increases. The distribution of binary orbital periods, however, is not consistent with the standard Ragahavan model, and our observations support the premise that exoplanet-hosting stars with binary companions have, in general, wider orbital separations than field binaries. We find that exoplanet-hosting binary star systems show a distribution peaking near 100 au, higher than the 40-50au peak that is observed for field binaries. This fact led to earlier suggestions that planet formation is suppressed in close binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/157/235
- Title:
- Observations of the Kepler field with TESS
- Short Name:
- J/AJ/157/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the ability of the Transiting Exoplanet Survey Satellite (TESS) to detect and improve our understanding of planetary systems in the Kepler field. By modeling the expected transits of all confirmed and candidate planets detected by Kepler as expected to be observed by TESS, we provide a probabilistic forecast of the detection of each Kepler planet in TESS data. We find that TESS has a greater than 50% chance of detecting 260 of these planets at the 3{sigma} level in one sector of observations and an additional 120 planets in two sectors. Most of these are large planets in short orbits around their host stars, although a small number of rocky planets are expected to be recovered. Most of these systems have only one known transiting planet; in only ~5% of known multiply transiting systems do we anticipate more than one planet to be recovered. When these planets are recovered, we expect TESS to be a powerful tool to characterize transit timing variations. Using Kepler-88 (KOI-142) as an example, we show that TESS will improve measurements of planet-star mass ratios and orbital parameters, and significantly reduce the transit timing uncertainty in future years. Because TESS will be most sensitive to hot Jupiters, we research whether TESS will be able to detect tidal orbital decay in these systems. We find two confirmed planetary systems (Kepler-2 b and Kepler-13 b) and five candidate systems that will be good candidates to detect tidal decay.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A40
- Title:
- OB stars in N206 in the LMC
- Short Name:
- J/A+A/615/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. Clusters or associations of early-type stars are often associated with a "superbubble" of hot gas. The formation of such superbubbles is caused by the feedback from massive stars. The complex N 206 in the Large Magellanic Cloud (LMC) exhibits a superbubble and a rich massive star population. Aims. Our goal is to perform quantitative spectral analyses of all massive stars associated with the N 206 superbubble in order to determine their stellar and wind parameters. We compare the superbubble energy budget to the stellar energy input and discuss the star formation history of the region. Methods. We observed the massive stars in the N 206 complex using the multi-object spectrograph FLAMES at ESO's Very Large Telescope (VLT). Available ultra-violet (UV) spectra from archives are also used. The spectral analysis is performed with Potsdam Wolf-Rayet (PoWR) model atmospheres by reproducing the observations with the synthetic spectra. Results. We present the stellar and wind parameters of the OB stars and the two Wolf-Rayet (WR) binaries in the N 206 complex. Twelve percent of the sample show Oe/Be type emission lines, although most of them appear to rotate far below critical. We found eight runaway stars based on their radial velocity. The wind-momentum luminosity relation of our OB sample is consistent with the expectations. The Hertzsprung-Russell diagram (HRD) of the OB stars reveals a large age spread (1-30Myr), suggesting different episodes of star formation in the complex. The youngest stars are concentrated in the inner part of the complex, while the older OB stars are scattered over outer regions. We derived the present day mass function for the entire N 206 complex as well as for the cluster NGC 2018. The total ionizing photon flux produced by all massive stars in the N 206 complex is Q_0_~=5x10^50^s^-1^, and the mechanical luminosity of their stellar winds amounts to L_mec_=1.7x10^38^erg/s. Three very massive Of stars are found to dominate the feedback among 164 OB stars in the sample. The two WR winds alone release about as much mechanical luminosity as the whole OB star sample. The cumulative mechanical feedback from all massive stellar winds is comparable to the combined mechanical energy of the supernova explosions that likely occurred in the complex. Accounting also for the WR wind and supernovae, the mechanical input over the last five Myr is ~=2.3x10^52^erg. Conclusions. The N206 complex in the LMC has undergone star formation episodes since more than 30Myr ago. From the spectral analyses of its massive star population, we derive a current star formation rate of 2.2x10^-3^M_{sun}_/yr. From the combined input of mechanical energy from all stellar winds, only a minor fraction is emitted in the form of X-rays. The corresponding input accumulated over a long time also exceeds the current energy content of the complex by more than a factor of five. The morphology of the complex suggests a leakage of hot gas from the superbubble.
- ID:
- ivo://CDS.VizieR/J/AN/331/349
- Title:
- O, B-type & red supergiant masses and luminosities
- Short Name:
- J/AN/331/349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive stars are of interest as progenitors of supernovae, i.e. neutron stars and black holes, which can be sources of gravitational waves. Recent population synthesis models can predict neutron star and gravitational wave observations but deal with a fixed supernova rate or an assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernova progenitors, i.e. with O- and early B-type stars, and also all supergiants within 3kpc. We restrict our sample to those massive stars detected both in 2MASS and observed by Hipparcos, i.e. only those stars with parallax and precise photometry. To determine the luminosities we calculated the extinctions from published multi-colour photometry, spectral types, luminosity class, all corrected for multiplicity and recently revised Hipparcos distances. We use luminosities and temperatures to estimate the masses and ages of these stars using different models from different authors.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/3012
- Title:
- OGLE-III Parallax microlensing events
- Short Name:
- J/MNRAS/458/3012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most stellar remnants so far have been found in binary systems, where they interact with matter from their companions. Isolated neutron stars and black holes are difficult to find as they are dark, yet they are predicted to exist in our Galaxy in vast numbers. We explored the OGLE-III data base of 150 million objects observed in years 2001-2009 and found 59 microlensing events exhibiting a parallax effect due to the Earth's motion around the Sun. Combining parallax and brightness measurements from microlensing light curves with expected proper motions in the Milky Way, we identified 13 microlensing events which are consistent with having a white dwarf, neutron star or a black hole lens and we estimated their masses and distances. The most massive of our black hole candidates has 9.3M_{sun}_ and is at a distance of 2.4kpc. The distribution of masses of our candidates indicates a continuum in mass distribution with no mass gap between neutron stars and black holes. We also present predictions on how such events will be observed by the astrometric Gaia mission.
- ID:
- ivo://CDS.VizieR/J/ApJ/748/14
- Title:
- ONC population data from WFI observations
- Short Name:
- J/ApJ/748/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new census of the Orion Nebula Cluster over a large field of view (>~30'x30'), significantly increasing the known population of stellar and substellar cluster members with precisely determined properties. We develop and exploit a technique to determine stellar effective temperatures from optical colors, nearly doubling the previously available number of objects with effective temperature determinations in this benchmark cluster. Our technique utilizes colors from deep photometry in the I band and in two medium-band filters at {lambda}~753 and 770nm, which accurately measure the depth of a molecular feature present in the spectra of cool stars. From these colors we can derive effective temperatures with a precision corresponding to better than one-half spectral subtype, and importantly this precision is independent of the extinction to the individual stars. Also, because this technique utilizes only photometry redward of 750nm, the results are only mildly sensitive to optical veiling produced by accretion. Completing our census with previously available data, we place some 1750 sources in the Hertzsprung-Russell diagram and assign masses and ages down to 0.02M_{sun}_. At faint luminosities, we detect a large population of background sources which is easily separated in our photometry from the bona fide cluster members. The resulting initial mass function of the cluster has good completeness well into the substellar mass range, and we find that it declines steeply with decreasing mass. This suggests a deficiency of newly formed brown dwarfs in the cluster compared to the Galactic disk population.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A79
- Title:
- ONC stars masses from literature
- Short Name:
- J/A+A/626/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ALMA observations of the Serpens South star-forming region suggest that stellar protoclusters may be completely mass segregated at birth. Independent observations also suggest that embedded clusters form segregated by mass. As the primordial mass segregation seems to be lost over time, we aim to study on which timescale an initially perfectly mass-segregated star cluster becomes indistinguishable from an initially not mass-segregated cluster. As an example, the Orion Nebula Cluster (ONC) is also discussed. We used N-body simulations of star clusters with various masses and two different degrees of primordial mass segregation. We analysed their energy redistribution through two-body relaxation to quantify the time when the models agree in terms of mass segregation, which sets in only dynamically in the models that are primordially not mass segregated. A comprehensive cross-matched catalogue combining optical, infrared, and X-ray surveys of ONC members was also compiled and made available. The models evolve to a similar radial distribution of high-mass stars after the core collapse (about half a median two-body relaxation time, t_rh_) and become observationally indistinguishable from the point of view of mass segregation at time tau_v_~3.3t_rh_. In the case of the ONC, using the distribution of high-mass stars, we may not rule out either evolutionary scenario (regardless of whether they are initially mass segregated). When we account for extinction and elongation of the ONC, as reported elsewhere, an initially perfectly mass-segregated state seems to be more consistent with the observed cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/1092
- Title:
- Optical photometry of the ONC. II.
- Short Name:
- J/ApJ/722/1092
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new analysis of the stellar population of the Orion Nebula Cluster (ONC) based on multi-band optical photometry and spectroscopy. We study the color-color diagrams in BVI, plus a narrowband filter centered at 6200{AA}, finding evidence that intrinsic color scales valid for main-sequence dwarfs are incompatible with the ONC in the M spectral-type range, while a better agreement is found employing intrinsic colors derived from synthetic photometry, constraining the surface gravity value as predicted by a pre-main-sequence isochrone. We refine these model colors even further, empirically, by comparison with a selected sample of ONC stars with no accretion and no extinction. We consider the stars with known spectral types from the literature, and extend this sample with the addition of 65 newly classified stars from slit spectroscopy and 182 M-type from narrowband photometry; in this way, we isolate a sample of about 1000 stars with known spectral type. We introduce a new method to self-consistently derive the stellar reddening and the optical excess due to accretion from the location of each star in the BVI color-color diagram. This enables us to accurately determine the extinction of the ONC members, together with an estimate of their accretion luminosities. We adopt a lower distance for the Orion Nebula than previously assumed, based on recent parallax measurements. With a careful choice of also the spectral-type-temperature transformation, we produce the new Hertzsprung-Russell diagram of the ONC population, more populated than previous works.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/46
- Title:
- Opt. photometry of SMUDGes ultra-diffuse galaxies
- Short Name:
- J/ApJS/247/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first systematic study of the stellar populations of ultra-diffuse galaxies (UDGs) in the field, integrating the large area search and characterization of UDGs by the SMUDGes survey with the twelve-band optical photometry of the S-PLUS survey. Based on Bayesian modeling of the optical colors of UDGs, we determine the ages, metallicities, and stellar masses of 100 UDGs distributed in an area of ~330deg^2^ in the Stripe 82 region. We find that the stellar masses and metallicities of field UDGs are similar to those observed in clusters and follow the trends previously defined in studies of dwarf and giant galaxies. However, field UDGs have younger luminosity- weighted ages than do UDGs in clusters. We interpret this result to mean that field UDGs have more extended star formation histories, including some that continue to form stars at low levels to the present time. Finally, we examine stellar population scaling relations that show that UDGs are, as a population, similar to other low surface brightness galaxies.
