A new search for planet transits in NGC 6791

Montalto, M.; Piotto, G.; Desidera, S.; Marchi, Fabrizio De; Bruntt, H.; Stetson, P. B.; Ferro, A. Arellano; Momany, Y.; Gratton, R.; Poretti, E.; Aparicio, A.; Barbieri, M.; Claudi, R.; Grundahl, F.; Rosenberg, Alfred

doi:10.1051/0004-6361:20066199

Cited by 35 publications

(52 citation statements)

References 62 publications

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“…The superiority of ISIS-type algorithms over aperture photometry has been clearly demonstrated for example in Montalto et al (2007). The OIS requires not only much more computational time, but also significantly improves the scatter in all our lightcurves compared to aperture photometry by a factor ∼1.5 in rms see Appendix A.5.…”

Section: Data Reductionmentioning

confidence: 64%

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

Abe

Gonçalves

Agabi

et al. 2013

A&A

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Aims. The Antarctica Search for Transiting ExoPlanets (ASTEP) program was originally aimed at probing the quality of the Dome C, Antarctica for the discovery and characterization of exoplanets by photometry. In the first year of operation of the 40 cm ASTEP 400 telescope (austral winter 2010), we targeted the known transiting planet WASP-19b in order to try to detect its secondary transits in the visible. This is made possible by the excellent sub-millimagnitude precision of the binned data. Methods. The WASP-19 system was observed during 24 nights in May 2010. Once brought back from Antarctica, the data were processed using various methods, and the best results were with an implementation of the optimal image subtraction (OIS) algorithm. Results. The photometric variability level due to starspots is about 1.8% (peak-to-peak), in line with the SuperWASP data from 2007 (1.4%) and higher than in 2008 (0.07%). We find a rotation period of WASP-19 of 10.7 ± 0.5 days, in agreement with the SuperWASP determination of 10.5 ± 0.2 days. Theoretical models show that this can only be explained if tidal dissipation in the star is weak, i.e. the tidal dissipation factor Q > 3 × 10 7 . Separately, we find evidence of a secondary eclipse of depth 390 ± 190 ppm with a 2.0σ significance, a phase that is consistent with a circular orbit and a 3% false positive probability. Given the wavelength range of the observations (420 to 950 nm), the secondary transit depth translates into a day-side brightness temperature of 2690 +150 −220 K, in line with measurements in the z and K bands. The day-side emission observed in the visible could be due either to thermal emission of an extremely hot day side with very little redistribution of heat to the night side or to direct reflection of stellar light with a maximum geometrical albedo A g = 0.27 ± 0.13. We also report a low-frequency oscillation in phase at the planet orbital period, but with a lower limit amplitude that could not be attributed to the planet phase alone and that was possibly contaminated with residual lightcurve trends.Conclusions. This first evidence of a secondary eclipse in the visible from the ground demonstrates the high potential of Dome C, Antarctica, for continuous photometric observations of stars with exoplanets. These continuous observations are required to understand star-planet interactions and the dynamical properties of exoplanetary atmospheres.

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Section: Data Reductionmentioning

confidence: 64%

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

Abe

Gonçalves

Agabi

et al. 2013

A&A

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“…All the images were reduced using image subtraction and the DAOPHOT/ALLSTAR packages as described in Montalto et al (2007). In particular, the image-subtraction method models the kernel that convolves the PSF of a reference high S /N image to match the PSF of a target image.…”

Section: Photometric Data Reductionmentioning

confidence: 99%

“…We analyzed the lightcurves to search for planetary transit events following the procedure presented in Montalto et al (2007). A separate paper in preparation accounts for the technical details and for the expected planetary frequency in our field of view.…”

Section: Photometric Data Reductionmentioning

confidence: 99%

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VLT multi-epoch radial velocity survey toward NGC 6253

Montalto¹,

Villanova²,

Koppenhoefer³

et al. 2011

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Context. One of the most metal-rich open cluster of the Galaxy, NGC 6253 is a target of special interest in the search for extrasolar planets, the study of stellar populations, and the chemical/dynamical evolution of the Galactic disk. Aims. We present the results of two photometric campaigns and a VLT multi-epoch radial velocity survey toward the open cluster NGC 6253. We complement our analysis with photometric, proper motion, and radial velocity data available from previous studies of this cluster, and analyze three planetary candidates found in the field of NGC 6253. Methods. We derived homogeneous radial velocity measurements for stars located at the turn-off, sub-giant, red-giant branch, redclump, and blue straggler regions of the cluster. We also analyzed a comparison sample of surrounding field stars. Spectra were obtained with the UVES and GIRAFFE spectrographs at the VLT during three epochs in August 2008. Results. The three UVES measurements acquired for our brightest transiting candidate (V = 15.26) are all consistent within their errors (200 m/s), but were acquired at very similar orbital phases. The mean radial velocity of this object is not consistent with the cluster recession velocity, which rules out cluster membership except in the case of a binary system. This star is worth further analysis with high-precision spectroscopy. For our faintest candidate (V = 18.247), we were able to exclude the observed transits being caused by a close-by stellar companion, but more precise measurements will be needed to derive an orbital fit and to study other possible scenarios. For the remaining candidate, no measurements were acquired probably because of bad fiber positioning. The mean radial velocity of the cluster is (RV cl ± σ cl ) = (−29.11 ± 0.85) km s −1 . Using both radial velocities and proper motions, we identified 35 cluster members. Our results are in good agreement with past radial velocity and photometric measurements. Furthermore, using our photometry, astrometry, and spectroscopy we identified a new eclipsing binary system member of the cluster. Conclusions. We discussed the possibility of detecting substellar companions (brown dwarfs and planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS) around turn-off stars of old open cluster. We isolated 5 stars that are optimal targets for searching for planetary mass companions with HARPS. Our optimized strategy minimizes the observing time requested to isolate and followup on the best planetary candidates in cluster with high-precision spectrographs, an important aspect given the faint target stars.

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“…They are also comprised of stars that share (in most cases) the same age and chemistry, and whose radii R and masses M are reliably known on their main sequence (MS). Open clusters (OC) have been targeted for extensive transit searches (Mochejska et al 2005;Montalto et al 2007Montalto et al , 2011Hartman et al 2009, most notably) but only a handful of weak, unconfirmed candidates have so far been detected (Mochejska et al 2006;Montalto et al 2011). A global reanalysis suggests that the overall statistical significance of these campaigns is so low that it could be compatible with the planet host incidence observed in the field (van Saders & Gaudi 2011).…”

Section: Introductionmentioning

confidence: 99%

An HST search for planets in the lower main sequence of the globular cluster NGC 6397

Nascimbeni

Bedin

Piotto

et al. 2012

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Searches for planetary transits carried out in open and globular clusters have to date yielded only a handful of weak, unconfirmed candidates. These results have been interpreted as either being insignificant, or evidence that the cluster chemical or dynamical environment inhibits planetary formation or survival. Most campaigns have been limited by small sample statistics or systematics from ground-based photometry. We performed a search for transiting planets and variables in a deep stellar field of NGC 6397 imaged by HST-ACS over 126 orbits. We analyzed 5078 light curves, including a careful selection of 2215 cluster-member M0-M9 dwarfs. The light curves were corrected for systematic trends and inspected using several tools. No high-significance planetary candidate is detected. We compared this null detection with the most recent results from Kepler, showing that no conclusive evidence of lower planet incidence can be drawn. However, a very small photometric jitter is measured for early-M cluster members ( 2 mmag on 98% of them), which may be worth targeting in the near future with more optimized campaigns. Twelve variable stars are reported for the first time.

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A new search for planet transits in NGC 6791

Cited by 35 publications

References 62 publications

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

VLT multi-epoch radial velocity survey toward NGC 6253

An HST search for planets in the lower main sequence of the globular cluster NGC 6397

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