scholarly journals The GTC exoplanet transit spectroscopy survey

2017 ◽  
Vol 605 ◽  
pp. A114 ◽  
Author(s):  
F. Murgas ◽  
E. Pallé ◽  
H. Parviainen ◽  
G. Chen ◽  
L. Nortmann ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Theoretical Models ◽  
Light Curves ◽  
Transmission Spectra ◽  
Atmospheric Species ◽  
Transiting Planets ◽  
Systematic Effects ◽  
Transit Model ◽  
In Transit ◽  
Molecular Compounds

Context. Transiting planets offer an excellent opportunity for characterizing the atmospheres of extrasolar planets under very different conditions from those found in our solar system. Aims. We are currently carrying out a ground-based survey to obtain the transmission spectra of several extrasolar planets using the 10 m Gran Telescopio Canarias. In this paper we investigate the extrasolar planet WASP-48b, a hot Jupiter orbiting around an F-type star with a period of 2.14 days. Methods. We obtained long-slit optical spectroscopy of one transit of WASP-48b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) spectrograph. We integrated the spectrum of WASP-48 and one reference star in several channels with different wavelength ranges, creating numerous color light curves of the transit. We fit analytic transit curves to the data taking into account the systematic effects present in the time series in an effort to measure the change of the planet-to-star radius ratio (Rp/Rs) across wavelength. The change in transit depth can be compared with atmosphere models to infer the presence of particular atomic or molecular compounds in the atmosphere of WASP-48b. Results. After removing the transit model and systematic trends to the curves we reached precisions between 261 ppm and 455–755 ppm for the white and spectroscopic light curves, respectively. We obtained Rp/Rs uncertainty values between 0.8 × 10-3 and 1.5 × 10-3 for all the curves analyzed in this work. The measured transit depth for the curves made by integrating the wavelength range between 530 nm and 905 nm is in agreement with previous studies. We report a relatively flat transmission spectrum for WASP-48b with no statistical significant detection of atmospheric species, although the theoretical models that fit the data more closely include TiO and VO.

scholarly journals The GTC exoplanet transit spectroscopy survey

2019 ◽  
Vol 622 ◽  
pp. A172 ◽  
Author(s):  
F. Murgas ◽  
G. Chen ◽  
E. Pallé ◽  
L. Nortmann ◽  
G. Nowak
Keyword(s):  
Transmission Spectrum ◽  
Rayleigh Scattering ◽  
Extrasolar Planets ◽  
Light Curves ◽  
Data Sets ◽  
Transmission Spectra ◽  
Data Set ◽  
Systematic Effects ◽  
The Individual ◽  
Spectrum Slope

Context. Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground- or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. Aims. We use the ten-meter Gran Telescopio Canarias (GTC) telescope to carry out a ground-based transmission spectra survey of extrasolar planets to characterize their atmospheres. In this paper we investigate the exoplanet HAT-P-11b, a Neptune-sized planet orbiting an active K-type star. Methods. We obtained long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. We integrated the spectrum of HAT-P-11 and one reference star in several spectroscopic channels across the λ ~ 400–785 nm region, creating numerous light curves of the transits. We fit analytic transit curves to the data taking into account the systematic effects and red noise present in the time series in an effort to measure the change of the planet-to-star radius ratio (Rp∕Rs) across wavelength. Results. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of δ = 0.62−0.17+0.20 and a spot-to-photosphere temperature difference of ΔT = 429−299+184 K.

scholarly journals Exomoon indicators in high-precision transit light curves

2020 ◽  
Vol 638 ◽  
pp. A43
Author(s):  
Kai Rodenbeck ◽  
René Heller ◽  
Laurent Gizon
Keyword(s):  
Extrasolar Planets ◽  
Light Curves ◽  
Low Density ◽  
Instrumental Effects ◽  
The Moon ◽  
Hill Stability ◽  
Follow Up Studies ◽  
Transit Model ◽  
Limb Darkening

Context. While the Solar System contains about 20 times more moons than planets, no moon has been confirmed around any of the thousands of extrasolar planets discovered so far. Considering the large computational load required for the statistical vetting of exomoon candidates in a star–planet–moon framework, tools for an uncomplicated identification of the most promising exomoon candidates could be beneficial to streamline follow-up studies. Aims. Here we study three exomoon indicators that emerge if well-established planet-only models are fitted to a planet–moon transit light curve: transit timing variations (TTVs), transit duration variations (TDVs), and apparent planetary transit radius variations (TRVs). We re-evaluate under realistic conditions the previously proposed exomoon signatures in the TTV and TDV series. Methods. We simulated light curves of a transiting exoplanet with a single moon, taking into account stellar limb darkening, orbital inclinations, planet–moon occultations, and noise from both stellar granulation and instrumental effects. These model light curves were then fitted with a planet-only transit model whilst pretending there were no moon, and we explored the resulting TTV, TDV, and TRV series for evidence of the moon. Results. The previously described ellipse in the TTV-TDV diagram of an exoplanet with a moon emerges only for high-density moons. However, low-density moons distort the sinusoidal shapes of the TTV and the TDV series due to their photometric contribution to the combined planet–moon transit. Sufficiently large moons can nevertheless produce periodic apparent TRVs of their host planets that could be observable. We find that Kepler and PLATO have similar performances in detecting the exomoon-induced TRV effect around simulated bright (mV = 8) stars. Although these stars are rare in the Kepler sample, they will be abundant in the PLATO sample. Moreover, PLATO’s higher cadence yields a stronger TTV signal. We detect substantial TRVs of the Saturn-sized planet Kepler-856 b although an exomoon could only ensure Hill stability in a very narrow orbital range. Conclusions. The periodogram of the sequence of transit radius measurements can indicate the presence of a moon. The TTV and TDV series of exoplanets with moons could be more complex than previously assumed. We propose that TRVs could be a more promising means to identify exomoons in large exoplanet surveys.

scholarly journals Identifying Transiting Circumbinary Planets

2008 ◽  
Vol 4 (S253) ◽  
pp. 378-381
Author(s):  
Aviv Ofir
Keyword(s):  
Detection Method ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Noise Levels ◽  
Fixed Amount ◽  
Transiting Planets ◽  
Wide Range ◽  
Error Bars ◽  
In Transit ◽  
Very High

AbstractTransiting planets manifest themselves by a periodic dimming of their host star by a fixed amount. On the other hand, light curves of transiting circumbinary (CB) planets are expected to be neither periodic nor to have a single depth while in transit, making the Box-Least-Squares (BLS) transit detection method almost ineffective. Therefore, a modified version for the identification of CB planets was developed - CB-BLS. We show that using CB-BLS it is possible to find CB planets in the residuals of light curves of eclipsing binaries (EBs) that have noise levels of 1% or more. Using CB-BLS will allow us to use the massive ground- and space-based photometric surveys to look for these objects. Detecting transiting CB planets is expected to have a wide range of implications. For instance, the frequency of CB planets depends on the planetary formation mechanism - and planets in close pairs of stars provide a most restrictive constraint on planet formation models. Furthermore, understanding very high precision light curves is limited by stellar parameters - and since for EBs the stellar parameters are much better determined, the resultant planetary structure models will have significantly smaller error bars, maybe even small enough to challenge theory.

 V1298 Tau: The story of warm gas giants orbiting an adolescent star

2021 ◽  
Author(s):  
Saugata Barat ◽  
Jean-Michel Desert ◽  
Bob Jacobs ◽  
Vatsal Panwar
Keyword(s):  
Internal Heat ◽  
Theoretical Models ◽  
Heat Of Formation ◽  
Scale Height ◽  
Transmission Spectra ◽  
Transiting Planets ◽  
T Tauri ◽  
Bright Spots ◽  
Absorption Features

<div>We are presenting the first atmospheric study of a young transiting exoplanet. We focus on the <span data-ogac="" data-ogab="" data-ogsc="" data-ogsb="">V1298</span> Tau system, which contains 4 giant transiting planets that orbit the young (23Myr) T Tauri star <span data-ogac="" data-ogab="" data-ogsc="" data-ogsb="">V1298</span> Tau. We have observed one primary transit of planet <span data-ogac="" data-ogab="" data-ogsc="" data-ogsb="">V1298</span> Tau b with HST to learn about its atmospheric properties.  This planet is ideally suited for atmospheric studies using transmission spectroscopy since it is a warm gas giant (Teq=677 K) with a very large atmospheric scale height (~250 km).</div><div>From theoretical models we expect strong water absorption features in its transmission spectra. However, this planet is particularly interesting since it is expected to be undergoing atmospheric 'erosion' due to high XUV flux from its host star and its internal heat of formation, and show how our observations can constrained the escape rate.  The <span data-ogac="" data-ogab="" data-ogsc="" data-ogsb="">V1298</span> Tau system is also interesting for the study of comparative exoplanetology between four freshly formed planets as their atmospheres are expected to carry fossil signatures of the planetary disk from which they formed. As a follow-up of the HST observations, we are scheduling observations planets b and c with JWST+NIRSpec in transmission as part of a GO-1 accepted proposal. <span data-ogac="" data-ogab="" data-ogsc="" data-ogsb="">V1298</span> Tau is an active star and we find signatures of bright spots and flares on the stellar surface with the HST+WFC3 observations, and emphasise the challenges that the stellar activity poses for such system. In this poster, we present results from the current programs and highlight the scientific interests of this system.</div>

scholarly journals TRAPPIST-1: Global results of the Spitzer Exploration Science Program Red Worlds

2020 ◽  
Vol 640 ◽  
pp. A112 ◽  
Author(s):  
E. Ducrot ◽  
M. Gillon ◽  
L. Delrez ◽  
E. Agol ◽  
P. Rimmer ◽  
...  
Keyword(s):  
High Energy ◽  
Light Curves ◽  
Transmission Spectra ◽  
Habitable Zone ◽  
Transiting Planets ◽  
Brightness Temperatures ◽  
Upper Limits ◽  
Instrumental Precision ◽  
Comprehensive Study

Context. With more than 1000 h of observation from Feb. 2016 to Oct. 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12 pc) ultracool dwarf star, finding that it is orbited by seven transiting Earth-sized planets. At least three of these planets orbit within the classical habitable zone of the star, and all of them are well-suited for a detailed atmospheric characterization with the upcoming JWST. Aims. The main goals of the Spitzer Red Worlds program were (1) to explore the system for new transiting planets, (2) to intensively monitor the planets’ transits to yield the strongest possible constraints on their masses, sizes, compositions, and dynamics, and (3) to assess the infrared variability of the host star. In this paper, we present the global results of the project. Methods. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 μm. For a comprehensive study, we analyzed all light curves both individually and globally. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 μm to constrain the brightness temperatures of their daysides. Results. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We do not detect any significant variation of the transit depths of the planets throughout the different campaigns. Comparing our individual and global analyses of the transits, we estimate for TRAPPIST-1 transit depth measurements mean noise floors of ~35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. We estimate that most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10 ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. Our analysis reveals a few outlier transits, but we cannot conclude whether or not they correspond to spot or faculae crossing events. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. Although we are limited by instrumental precision, the combined transmission spectrum of planet b to g tells us that their atmospheres seem unlikely to be CH4-dominated. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 μm, and can only set 3-σ upper limits on their dayside brightness temperatures (611 K for b 586 K for c).

scholarly journals A multi-wavelength analysis of the WASP-12 planetary system

2010 ◽  
Vol 6 (S276) ◽  
pp. 163-166 ◽  
Author(s):  
Luca Fossati ◽  
Carole A. Haswell ◽  
Cynthia S. Froning
Keyword(s):  
Magnetic Field ◽  
Atmospheric Pollution ◽  
Planetary System ◽  
Light Curves ◽  
Absorption Lines ◽  
Transiting Planets ◽  
Multi Wavelength ◽  
Global Magnetic Field ◽  
Solar Type ◽  
Solar Type Star

AbstractWASP-12 is a 2 Gyr old solar type star, hosting WASP-12b, one of the most irradiated transiting planets currently known. We observed WASP-12 in the UV with the Cosmic Origins Spectrograph (COS) on HST. The light curves we obtained in the three covered UV wavelength ranges, all of which contain many photospheric absorption lines, imply effective radii of 2.69±0.24 RJ, 2.18±0.18 RJ, and 2.66±0.22 RJ, suggesting that the planet is surrounded by an absorbing cloud which overfills the Roche lobe. We clearly detected enhanced transit depths at the wavelengths of the MgII h&k resonance lines. Spectropolarimetric analysis of the host star was also performed. We found no global magnetic field, but there were hints of atmospheric pollution, which might be connected to the very unusual activity of the host star.

scholarly journals Supernova Abundance Generation

1991 ◽  
Vol 145 ◽  
pp. 21-38
Author(s):  
K. Nomoto ◽  
T. Shigeyama ◽  
T. Tsujimoto
Keyword(s):  
Heavy Element ◽  
Massive Stars ◽  
Theoretical Models ◽  
Light Curves ◽  
Maximum Brightness ◽  
Sn 1987A ◽  
New Models ◽  
Decline Rate ◽  
Type Ia ◽  
Supernova Explosions

Theoretical models of supernova explosions of various types are reviewed to obtain heavy element yields from supernovae. We focus on new models for SN 1987A, and Type Ia, Ib, and Ic supernovae. Maximum brightness and decline rate of their light curves suggest that 12–18 M⊙ stars produce larger amount of 56Ni than more massive stars. We discuss relative roles of various types of supernovae in the chemical evolution of galaxies.

scholarly journals Observations of the transiting planet TrES-2 with the AIU Jena telescope in Großschwabhausen

2008 ◽  
Vol 4 (S253) ◽  
pp. 436-439 ◽  
Author(s):  
S. Raetz ◽  
M. Mugrauer ◽  
T. O. B. Schmidt ◽  
T. Roell ◽  
T. Eisenbeiss ◽  
...  
Keyword(s):  
High Precision ◽  
Orbital Period ◽  
Ccd Camera ◽  
Light Curves ◽  
Orbital Parameters ◽  
Transiting Planets ◽  
Photometric Monitoring ◽  
Cassegrain Telescope ◽  
Parent Star ◽  
Planetary Transits

AbstractWe have started high precision photometric monitoring observations at the AIU Jena observatory in Großschwabhausen near Jena in fall 2006. We used a 25.4cm Cassegrain telescope equipped with a CCD-camera mounted piggyback on a 90cm telescope. To test the attainable photometric precision, we observed stars with known transiting planets. We could recover all planetary transits observed by us.We observed the parent star of the transiting planet TrES-2 over a longer period in Großschwabhausen. Between March and November 2007 seven different transits and almost a complete orbital period were analyzed. Overall, in 31 nights of observation 3423 exposures (in total 57.05h of observation) of the TrES-2 parent star were taken. Here, we present our methods and the resulting light curves. Using our observations we could improve the orbital parameters of the system.

scholarly journals A search for transiting planets around FGKM dwarfs and subgiants in the TESS full frame images of the Southern ecliptic hemisphere

2020 ◽  
Vol 498 (2) ◽  
pp. 1726-1749 ◽  
Author(s):  
M Montalto ◽  
L Borsato ◽  
V Granata ◽  
G Lacedelli ◽  
L Malavolta ◽  
...  
Keyword(s):  
Random Forest ◽  
Light Curves ◽  
Correct Identification ◽  
Transiting Planets ◽  
Long Period ◽  
Period Distribution ◽  
Distribution Ranges ◽  
Show Evidence ◽  
Dynamical Constraints ◽  
Subgiant Stars

ABSTRACT In this work, we present the analysis of 976 814 FGKM dwarf and subgiant stars in the Transiting Exoplanet Survey Telescope (TESS) full frame images (FFIs) of the Southern ecliptic hemisphere. We present a new pipeline, DIAmante, developed to extract optimized, multisector photometry from TESS FFIs and a classifier, based on the Random Forest technique, trained to discriminate plausible transiting planetary candidates from common false positives. A new statistical model was developed to provide the probability of correct identification of the source of variability. We restricted the planet search to the stars located in the least crowded regions of the sky and identified 396 transiting planetary candidates among which 252 are new detections. The candidates’ radius distribution ranges between 1 R⊕ and 2.6 RJ with median value of 1 RJ and the period distribution ranges between 0.25 and 105 d with median value of 3.8 d. The sample contains four long period candidates (P > 50 d), one of which is new, and 64 candidates with periods between 10 and 50 d (42 new ones). In the small planet radius domain (4R < R⊕), we found 39 candidates among which 15 are new detections. Additionally, we present 15 single transit events (14 new ones), a new candidate multiplanetary system, and a novel candidate around a known TOI. By using Gaia dynamical constraints, we found that 70 objects show evidence of binarity. We release a catalogue of the objects we analysed and the corresponding light curves and diagnostic figures through the MAST and ExoFOP portals.

scholarly journals Transit least-squares survey

2019 ◽  
Vol 627 ◽  
pp. A66 ◽  
Author(s):  
René Heller ◽  
Michael Hippke ◽  
Kai Rodenbeck
Keyword(s):  
Signal Detection ◽  
Least Squares ◽  
Visual Inspection ◽  
Detection Efficiency ◽  
Light Curves ◽  
Direct Result ◽  
Transiting Planets ◽  
Least Squares Algorithm ◽  
Orbital Periods ◽  
Primary Mission

The extended Kepler mission (K2) has revealed more than 500 transiting planets in roughly 500 000 stellar light curves. All of these were found either with the box least-squares algorithm or by visual inspection. Here we use our new transit least-squares (TLS) algorithm to search for additional planets around all K2 stars that are currently known to host at least one planet. We discover and statistically validate 17 new planets with radii ranging from about 0.7 Earth radii (R⊕) to roughly 2.2 R⊕ and a median radius of 1.18 R⊕. EPIC 201497682.03, with a radius of 0.692+0.059−0.048, is the second smallest planet ever discovered with K2. The transit signatures of these 17 planets are typically 200 ppm deep (ranging from 100 ppm to 2000 ppm), and their orbital periods extend from about 0.7 d to 34 d with a median value of about 4 d. Fourteen of these 17 systems only had one known planet before, and they now join the growing number of multi-planet systems. Most stars in our sample have subsolar masses and radii. The small planetary radii in our sample are a direct result of the higher signal detection efficiency that TLS has compared to box-fitting algorithms in the shallow-transit regime. Our findings help in populating the period-radius diagram with small planets. Our discovery rate of about 3.7% within the group of previously known K2 systems suggests that TLS can find over 100 additional Earth-sized planets in the data of the Kepler primary mission.

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