- ID:
- ivo://CDS.VizieR/J/ApJS/253/11
- Title:
- TESS observations of Cepheid stars
- Short Name:
- J/ApJS/253/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first analysis of Cepheid stars observed by the TESS space mission in Sectors 1-5. Our sample consists of 25 pulsators: ten fundamental mode, three overtone and two double-mode classical Cepheids, plus three type II and seven anomalous Cepheids. The targets were chosen from fields with different stellar densities, both from the Galactic field and from the Magellanic System. Three targets have 2 minutes cadence light curves available by the TESS Science Processing Operations Center: for the rest, we prepared custom light curves from the full-frame images with our own differential photometric FITSH pipeline. Our main goal was to explore the potential and the limitations of TESS concerning the various subtypes of Cepheids. We detected many low-amplitude features: weak modulation, period jitter, and timing variations due to light-time effect. We also report signs of nonradial modes and the first discovery of such a mode in an anomalous Cepheid, the overtone star XZ Cet, which we then confirmed with ground-based multicolor photometric measurements. We prepared a custom photometric solution to minimize saturation effects in the bright fundamental-mode classical Cepheid, {beta} Dor with the lightkurve software, and we revealed strong evidence of cycle-to-cycle variations in the star. In several cases, however, fluctuations in the pulsation could not be distinguished from instrumental effects, such as contamination from nearby sources, which also varies between sectors.
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- ID:
- ivo://CDS.VizieR/J/ApJ/872/L9
- Title:
- TESS obs. of massive O and B stars
- Short Name:
- J/ApJ/872/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Uncertainties in stellar structure and evolution theory are largest for stars undergoing core convection on the main sequence. A powerful way to calibrate the free parameters used in the theory of stellar interiors is asteroseismology, which provides direct measurements of angular momentum and element transport. We report the detection and classification of new variable O and B stars using high-precision short-cadence (2 minutes) photometric observations assembled by the Transiting Exoplanet Survey Satellite (TESS). In our sample of 154 O and B stars, we detect a high percentage (90%) of variability. Among these we find 23 multiperiodic pulsators, 6 eclipsing binaries, 21 rotational variables, and 25 stars with stochastic low-frequency variability. Several additional variables overlap between these categories. Our study of O and B stars not only demonstrates the high data quality achieved by TESS for optimal studies of the variability of the most massive stars in the universe, but also represents the first step toward the selection and composition of a large sample of O and B pulsators with high potential for joint asteroseismic and spectroscopic modeling of their interior structure with unprecedented precision.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A71
- Title:
- TESS optical phase curve of KELT-1b
- Short Name:
- J/A+A/648/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection and analysis of the phase curve of KELT-1b at optical wavelengths, analyzing data taken by the Transiting Exoplanet Survey Satellite (TESS). The light curve shows variations due to ellipsoidal variations, Doppler beaming, transit and secondary eclipse of KELT-1, and phase curve variations of KELT-1b.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A53
- Title:
- TESS planet candidates classification
- Short Name:
- J/A+A/633/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurately and rapidly classifying exoplanet candidates from transit surveys is a goal of growing importance as the data rates from space-based survey missions increase. This is especially true for NASA's TESS mission which generates thousands of new candidates each month. Here we created the first deep learning model capable of classifying TESS planet candidates. We adapted the neural network model of Ansdell et al (2018) to TESS data. We then trained and tested this updated model on 4 sectors of high-fidelity, pixel-level simulations data created using the Lilith simulator & processed using the full TESS pipeline. With the caveat that direct transfer of the model to real data will not perform as accurately, we also applied this model to four sectors of TESS candidates. We find our model performs very well on our simulated data, with 97% average precision and 92% accuracy on planets in the 2-class model. This accuracy is also boosted by another ~4% if planets found at the wrong periods are included. We also performed 3- and 4-class classification of planets, blended & target eclipsing binaries, and non-astrophysical false positives, which have slightly lower average precision and planet accuracies, but are useful for follow-up decisions. When applied to real TESS data, 61% of Threshold Crossing Events (TCEs) coincident with currently published TOIs are recovered as planets, 4% more are suggested to be Eclipsing Binaries, and we propose a further 200 TCEs as planet candidates.
- ID:
- ivo://CDS.VizieR/J/PASP/131/C4401
- Title:
- TESS predicted yield of transits
- Short Name:
- J/PASP/131/C4401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocity (RV) surveys have detected hundreds of exoplanets through their gravitational interactions with their host stars. Some will be transiting, but most lack sufficient follow-up observations to confidently detect (or rule out) transits. We use published stellar, orbital, and planetary parameters to estimate the transit probabilities for nearly all exoplanets that have been discovered via the RV method. From these probabilities, we predict that 25.5_-0.7_^+0.7^ of the known RV exoplanets should transit their host stars. This prediction is more than double the amount of RV exoplanets that are currently known to transit. The Transiting Exoplanet Survey Satellite (TESS) presents a valuable opportunity to explore the transiting nature of many of the known RV exoplanet systems. Based on the anticipated pointing of TESS during its two-year primary mission, we identify the known RV exoplanets that it will observe and predict that 11.7_-0.3_^+0.3^ of them will have transits detected by TESS. However, we only expect the discovery of transits for ~3 of these exoplanets to be novel (i.e., not previously known). We predict that the TESS photometry will yield dispositive null results for the transits of ~125 RV exoplanets. This will represent a substantial increase in the effort to refine ephemerides of known RV exoplanets. We demonstrate that these results are robust to changes in the ecliptic longitudes of future TESS observing sectors. Finally, we consider how several potential TESS extended mission scenarios affect the number of transiting RV exoplanets we expect TESS to observe.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A64
- Title:
- TESS time of eclipse of 15 eclipsing binaries
- Short Name:
- J/A+A/649/A64
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The change in the argument of periastron of eclipsing binaries, that is, the apsidal motion caused by classical and relativistic effects, can be measured from variations in the difference between the time of minimum light of the primary and secondary eclipses. Poor apsidal motion rate determinations and large uncertainties in the classical term have hampered previous attempts to determine the general relativistic term with sufficient precision to test general relativity predictions. As a product of the TESS mission, thousands of high-precision light curves from eclipsing binaries are now available. Using a selection of suitable well-studied eccentric eclipsing binary systems, we aim to determine their apsidal motion rates and place constraints on key gravitational parameters. We compute the time of minimum light from the TESS light curves of 15 eclipsing binaries with precise absolute parameters and with an expected general relativistic contribution to the total apsidal motion rate of greater than 60%. We use the changing primary and secondary eclipse timing differences over time to compute the apsidal motion rate, when possible, or the difference between the linear periods as computed from primary and secondary eclipses. For a greater time baseline we carefully combine the high-precision TESS timings with archival reliable timings. We determine the apsidal motion rate of 9 eclipsing binaries, 5 of which are reported for the first time. From these, we are able to measure the general relativistic apsidal motion rate of 6 systems with sufficient precision to test general relativity for the first time using this method. This test explores a regime of gravitational forces and potentials that had not been probed before. We find perfect agreement with theoretical predictions, and we are able to set stringent constraints on two parameters of the parametrised post-Newtonian formalism.
- ID:
- ivo://CDS.VizieR/J/ApJ/704/1405
- Title:
- Testing the E_peak_-E_iso_ relation for GRBs
- Short Name:
- J/ApJ/704/1405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the most prominent, yet controversial associations derived from the ensemble of prompt-phase observations of gamma-ray bursts (GRBs) is the apparent correlation in the source frame between the peak energy (E_peak_) of the {nu}F({nu}) spectrum and the isotropic radiated energy, E_iso_. Since most GRBs have E_peak_ above the energy range (15-150keV) of the Burst Alert Telescope (BAT) on Swift, determining accurate E_peak_ values for large numbers of Swift bursts has been difficult. However, by combining data from Swift/BAT and the Suzaku Wide-band All-Sky Monitor (WAM), which covers the energy range from 50 to 5000keV, for bursts which are simultaneously detected, one can accurately fit E_peak_ and E_iso_ and test the relationship between them for the Swift sample. Between the launch of Suzaku in 2005 July and the end of 2009 April, there were 48 GRBs that triggered both Swift/BAT and WAM, and an additional 48 bursts that triggered Swift and were detected by WAM, but did not trigger. A BAT-WAM team has cross-calibrated the two instruments using GRBs, and we are now able to perform joint fits on these bursts to determine their spectral parameters. For those bursts with spectroscopic redshifts, we can also calculate the isotropic energy. Here, we present the results of joint Swift/BAT-Suzaku/WAM spectral fits for 91 of the bursts detected by the two instruments.
- ID:
- ivo://CDS.VizieR/VI/56
- Title:
- Tests of shock chemistry in IC 443G
- Short Name:
- VI/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present study improves the computations of the collisional excitation rates by Green & Chapman (1978) for CS-H2; and by Bieniek & Green (1981) for SiO-H2. Part of the results are presented in the Appendix of the publication.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/56
- Title:
- TeV gamma-ray blazar X-ray spectral studies
- Short Name:
- J/MNRAS/458/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work is a summary of the X-ray spectral studies of 29TeV (10^12^eV, tera-electron-volt) {gamma}-ray emitting blazars observed with Swift/XRT, especially focusing on sources for which the X-ray regime allows us to study the low- and the high-energy ends of the particle distribution function. Variability studies require simultaneous coverage, ideally sampling different flux states of each source. This is achieved using X-ray observations by disentangling the high-energy end of the synchrotron emission and the low-energy end of the Compton emission, which are produced by the same electron population. We focused on a sample of 29 TeV {gamma}-ray emitting blazars with the best signal-to-noise X-ray observations collected with Swift/XRT in the energy range 0.3-10keV during 10yr of Swift/XRT operations. We investigate the X-ray spectral shapes and the effects of different corrections for neutral hydrogen absorption and decompose the synchrotron and inverse Compton components. For five sources (3C 66A, S5 0716+714, W Comae, 4C +21.35 and BL Lacertae) a superposition of both components is observed in the X-ray band, permitting simultaneous, time-resolved studies of both ends of the electron distribution. The analysis of multi-epoch observations revealed that the break energy of the X-ray spectrum varies only by a small factor with flux changes. Flux variability is more pronounced in the synchrotron domain (high-energy end of the electron distribution) than in the Compton domain (low-energy end of the electron distribution). The spectral shape of the Compton domain is stable, while the flux of the synchrotron domain is variable. These changes cannot be described by simple variations of the cut-off energy, suggesting that the high-energy end of the electron distribution is not generally well described by cooling only.
- ID:
- ivo://CDS.VizieR/J/A+A/406/L9
- Title:
- TeV Gamma-Rays from 1ES1959+650
- Short Name:
- J/A+A/406/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- TeV gamma-rays from the BL Lac object 1ES1959+650 have been measured during the years 2000 and 2001 with a significance of 5.2{sigma} at a value of 5.3% of the Crab flux and in May 2002 during strong outbursts with >23{sigma} at a flux level of up to 2.2Crab, making 1ES1959+650 the TeV Blazar with the third best event statistics. The deep observation of 197.4h has been performed with the HEGRA stereoscopic system of 5 imaging atmospheric Cherenkov telescopes (IACT system). 1ES1959+650 is located at a redshift of z=0.047, providing an intermediate distance between the nearby Blazars Mkn 421 and Mkn 501, and the much more distant object H1426+428. This makes 1ES1959+650 an important candidate of the class of TeV Blazars in view of the absorption of TeV photons by the diffuse extragalactic background radiation (DEBRA). The differential energy spectrum of 1ES1959+650 during the flares can be well described by a power law with an exponential cut-off at (4.2(+0.8-0.6)_stat_+/-0.9_sys_) TeV and a spectral index of 1.83+/-0.15_stat_+/-0.08_sys_, while the low state spectrum can be fitted by a pure power law with a spectral index of 3.18+/-0.17_stat_+/-0.08_sys_.