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- ID:
- ivo://CDS.VizieR/J/ApJ/643/356
- Title:
- Transient X-ray sources in M31
- Short Name:
- J/ApJ/643/356
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From 1999 October to 2002 August, 45 transient X-ray sources were detected in M31 by Chandra and XMM-Newton. We have performed spectral analysis of all XMM-Newton and Chandra ACIS detections of these sources, as well as flux measurements of Chandra HRC detections. The result is absorption-corrected X-ray light curves for these sources covering this 2.8yr period, along with spectral parameters for several epochs of the outbursts of most of the transient sources. We supply a catalog of the locations, outburst dates, peak observed luminosities, decay time estimates, and spectral properties of the transient sources, and we discuss similarities with Galactic X-ray novae. Duty cycle estimates are possible for eight of the transients and range from 34% to 2%; upper limits to the duty cycles are estimated for an additional 15 transients and cover a similar range. We find five transients that have rapid decay times and may be ultracompact X-ray binaries. Spectra of three of the transients suggest that they may be faint Galactic foreground sources. If even one is a foreground source, this suggests a surface density of faint transient X-ray sources of >~1deg^2^.
- ID:
- ivo://CDS.VizieR/J/AJ/159/83
- Title:
- Transit analysis for the K2-25 system
- Short Name:
- J/AJ/159/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance of planets with orbital periods of a few to tens of days suggests that exoplanets experience complex dynamical histories. Planets in young stellar clusters or associations have well-constrained ages and therefore provide an opportunity to explore the dynamical evolution of exoplanets. K2-25b is a Neptune-sized planet in an eccentric, 3.48day orbit around an M4.5 dwarf star in the Hyades cluster (650Myr). In order to investigate its non-zero eccentricity and tight orbit, we analyze transit timing variations (TTVs) which could reveal clues to the migration processes that may have acted on the planet. We obtain 12 nonconsecutive transits using the MEarth observatories and long-term photometric monitoring, which we combine with 10 transits from the Spitzer Space Telescope and 20 transits from K2. Tables of MEarth photometry accompany this work. We fit each transit lightcurve independently. We first investigate whether inhomogeneities on the stellar surface (such as spots or plages) are differentially affecting our transit observations. The measured transit depth does not vary significantly between transits, though we see some deviations from the fiducial transit model. We then looked for TTVs as evidence of a nontransiting perturber in the system. We find no evidence for >1M_{Earth}_ mass companions within a 2:1 period ratio, or for >5M_{Earth}_ mass planets within a 7:2 period ratio.
- ID:
- ivo://CDS.VizieR/J/AJ/161/72
- Title:
- 180 Transit and occultation times for WASP-12b
- Short Name:
- J/AJ/161/72
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- Theory suggests that the orbits of some close-in giant planets should decay due to tidal interactions with their host stars. To date, WASP-12b is the only hot Jupiter reported to have a decaying orbit, at a rate of 29{+/-}2ms/yr. We analyzed data from NASA's Transiting Exoplanet Survey Satellite (TESS) to verify that WASP-12b's orbit is indeed changing. We find that the TESS transit and occultation data are consistent with a decaying orbit with an updated period of 1.091420090{+/-}0.000000041days and a decay rate of 32.53{+/-}1.62ms/yr. We find an orbital decay timescale of {tau}=P/|P|=2.90{+/-}0.14Myr. If the observed decay results from tidal dissipation, the modified tidal quality factor is Q_*_'=1.39{+/-}0.15x10^5^, which falls at the lower end of values derived for binary star systems and hot Jupiters. Our result highlights the power of space-based photometry for investigating the orbital evolution of short-period exoplanets.
- ID:
- ivo://CDS.VizieR/J/AJ/161/174
- Title:
- Transit depth biases & error bars for 31 planets
- Short Name:
- J/AJ/161/174
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- The occurrence of a planet transiting in front of its host star offers the opportunity to observe the planet's atmosphere filtering starlight. The fraction of occulted stellar flux is roughly proportional to the optically thick area of the planet, the extent of which depends on the opacity of the planet's gaseous envelope at the observed wavelengths. Chemical species, haze, and clouds are now routinely detected in exoplanet atmospheres through rather small features in transmission spectra, i.e., collections of planet-to-star area ratios across multiple spectral bins and/or photometric bands. Technological advances have led to a shrinking of the error bars down to a few tens of parts per million (ppm) per spectral point for the brightest targets. The upcoming James Webb Space Telescope (JWST) is anticipated to deliver transmission spectra with precision down to 10ppm. The increasing precision of measurements requires a reassessment of the approximations hitherto adopted in astrophysical models, including transit light-curve models. Recently, it has been shown that neglecting the planet's thermal emission can introduce significant biases in the transit depth measured with the JWST/Mid-InfraRed Instrument, integrated between 5 and 12{mu}m. In this paper, we take a step forward by analyzing the effects of the approximation on transmission spectra over the 0.6-12{mu}m wavelength range covered by various JWST instruments. We present open-source software to predict the spectral bias, showing that, if not corrected, it may affect the inferred molecular abundances and thermal structure of some exoplanet atmospheres.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A102
- Title:
- Transit events of 4 extrasolar planets
- Short Name:
- J/A+A/657/A102
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Meter-sized ground-based telescopes are frequently used today for the follow-up of extrasolar planet candidates. While the transit signal of a Jupiter-sized object can typically be detected to a high level of confidence with small telescope apertures as well, the shallow transit dips of planets with the size of Neptune and smaller are more challenging to reveal. We employ new observational data to illustrate the photometric follow-up capabilities of meter-sized telescopes for shallow exoplanet transits. We describe in detail the capability of distinguishing the photometric signal of an exoplanet transit from an underlying trend in the light curve. The transit depths of the six targets we observed, Kepler-94b, Kepler-63b, K2-100b, K2-138b, K2-138c, and K2-138e, range from 3.9ppt down to 0.3ppt. For five targets of this sample, we provide the first ground-based photometric follow-up. The timing of three targets is precisely known from previous observations, and the timing of the other three targets is uncertain and we aim to constrain it. We detect or rule out the transit features significantly in single observations for the targets that show transits of 1.3ppt or deeper. The shallower transit depths of two targets of 0.6 and 0.8ppt were detected tentatively in single light curves, and were detected significantly by repeated observations. Only for the target of the shallowest transit depth of 0.3ppt were we unable to draw a significant conclusion despite combining five individual light curves. An injection-recovery test on our real data shows that we detect transits of 1.3ppt depth significantly in single light curves if the transit is fully covered, including out-of-transit data toward both sides, in some cases down to 0.7ppt depth. For Kepler-94b, Kepler-63b, and K2-100b, we were able to verify the ephemeris. In the case of K2-138c with a 0.6ppt deep transit, we were able to refine it, and in the case of K2-138e, we ruled out the transit in the time interval of more than +/-1.5{sigma} of its current literature ephemeris.
- ID:
- ivo://CDS.VizieR/J/AJ/154/49
- Title:
- Transiting Exoplanet Monitoring Project. II. HAT-P-33
- Short Name:
- J/AJ/154/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 10 R-band photometric observations of eight different transits of the hot Jupiter HAT-P-33b, which has been targeted by our Transiting Exoplanet Monitoring Project. The data were obtained by two telescopes at the Xinglong Station of National Astronomical Observatories of China (NAOC) from 2013 December through 2016 January, and exhibit photometric scatter of 1.6-3.0mmag. After jointly analyzing the previously published photometric data, radial-velocity (RV) measurements, and our new light curves, we revisit the system parameters and orbital ephemeris for the HAT-P-33b system. Our results are consistent with the published values except for the planet to star radius ratio (R_P_/R_*_), the ingress/egress duration ({tau}) and the total duration (T_14_), which together indicate a slightly shallower and shorter transit shape. Our results are based on more complete light curves, whereas the previously published work had only one complete transit light curve. No significant anomalies in Transit Timing Variations (TTVs) are found, and we place upper mass limits on potential perturbers, largely supplanting the loose constraints provided by the extant RV data. The TTV limits are stronger near mean-motion resonances, especially for the low-order commensurabilities. We can exclude the existence of a perturber with mass larger than 0.6, 0.3, 0.5, 0.5, and 0.3M_{Earth}_ near the 1:3, 1:2, 2:3, 3:2, and 2:1 resonances, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/424/L31
- Title:
- Transiting exoplanet OGLE-TR-132b
- Short Name:
- J/A+A/424/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This data is the lightcurve of the transiting planetary system OGLE-TR-132. Very high photometric precision has been obtained using FORS2 on the VLT (ESO). The transit occuring on May 16th, 2004 has been observed in very good atmospheric conditions. Image subtraction and aperture photometry was performed. The flux is normalized to unity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/506/3810
- Title:
- 7 transiting exoplanets CHEOPS light curves
- Short Name:
- J/MNRAS/506/3810
- Date:
- 03 Dec 2021 00:34:45
- Publisher:
- CDS
- Description:
- We present 17 transit light curves of seven known warm-Jupiters observed with the CHaracterising ExOPlanet Satellite (CHEOPS). The light curves have been collected as part of the CHEOPS Guaranteed Time Observation (GTO) program that searches for transit-timing variation (TTV) of warm-Jupiters induced by a possible external perturber to shed light on the evolution path of such planetary systems. We describe the CHEOPS observation process, from the planning to the data analysis. In this work we focused on the timing performance of CHEOPS, the impact of the sampling of the transit phases, and the improvement we can obtain combining multiple transits together. We reached the highest precision on the transit time of about 13-16s for the brightest target (WASP-38, G=9.2) in our sample. From the combined analysis of multiple transits of fainter targets with G>=11 we obtained a timing precision of ~2min. Additional observations with CHEOPS, covering a longer temporal baseline, will further improve the precision on the transit times and will allow us to detect possible TTV signals induced by an external perturber.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/77
- Title:
- Transiting Exoplanet Survey Satellite (TESS)
- Short Name:
- J/ApJ/809/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) is a NASA-sponsored Explorer mission that will perform a wide-field survey for planets that transit bright host stars. Here, we predict the properties of the transiting planets that TESS will detect along with the EB stars that produce false-positive photometric signals. The predictions are based on Monte Carlo simulations of the nearby population of stars, occurrence rates of planets derived from Kepler, and models for the photometric performance and sky coverage of the TESS cameras. We expect that TESS will find approximately 1700 transiting planets from 2x10^5^ pre-selected target stars. This includes 556 planets smaller than twice the size of Earth, of which 419 are hosted by M dwarf stars and 137 are hosted by FGK dwarfs. Approximately 130 of the R<2R_{Earth}_ planets will have host stars brighter than Ks=9. Approximately 48 of the planets with R<2R_{Earth}_ lie within or near the habitable zone (0.2<S/S_{Earth}_<2); between 2 and 7 such planets have host stars brighter than Ks=9. We also expect approximately 1100 detections of planets with radii 2-4R_{Earth}_, and 67 planets larger than 4R_{Earth}_. Additional planets larger than 2R_{Earth}_ can be detected around stars that are not among the pre-selected target stars, because TESS will also deliver full-frame images at a 30-minute cadence. The planet detections are accompanied by over 1000 astrophysical false positives. We discuss how TESS data and ground-based observations can be used to distinguish the false positives from genuine planets. We also discuss the prospects for follow-up observations to measure the masses and atmospheres of the TESS planets.