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Wednesday, 24 October 2012

TFRM-PSES (TFRM-Preselected Super-Earths Survey):

Recently, Irwin et al. (2009) proposed an interesting alternative observational approach which has been executed by the MEarth project. In order to maximize the probability of detection of rocky super-Earths in the Habitable Zone (HZ), MEarth is photometrically monitoring a sample of ~2000 M-type stars, which have been pre-selected. MEarth operates 8 telescopes f/9 Ritchey-Chretien with a field of view (FOV) of 25'x25' each. Due to this limited FOV (0.17 square degrees), this project can only monitor a single star per telescope at a time. Despite this limitation on the efficiency of the survey, only in 2 years of full operation, it has been able to detect the first super-Earth (GJ1214b) with this new pre-selected strategy survey (Charbonneau et al. 2009).
 
As mentioned in Fors et al. (2010) , the 19.4 square degrees TFRM FOV is the most remarkable feature of this telescope. This, combined with the fact that a 30-second exposure typically contains ~20.000 stars with SNR> 5 (V <15.5mag) and a photometric precision better than 10 milimagnitudes (3-4 milimagmitudes typically for V down to 13-13.5mag), makes that the telescope has a great probability in detecting new exoplanets by transit technique.
 
Since December 2011, and in collaboration with the team of Dr.Ignasi Ribas (ICE-CSIC), the TFRM began to survey a pre-selected series of fields, with an input catalog similar to MEarth's, in search of super-Earths around Ms stars. The TFRM-PSES, with sufficient cadence, is able to monitor multiple fields observed every night, each one containing typically ~20 M-type catalogued stars, mainly in the range of 9.0mag < V < 15.5mag. Note that this magnitude limit V = 15.5mag could be increased, but then the cadence of the survey would be longer, which would penalize its efficiency when recording possible transits.
 
In particular,  the current (23 Apr 2014) coverage of the TFRM-PSES survey is that 48 of the 60 catalogued fields have been observed with a median number of epochs of 19.
 
Catalogued fields with M dwarfs to be observe
Catalogued fields with M dwarfs to be observed.
Fields with M dwarfs already observed at least once.
 Fields with M dwarfs already observed at least once.
 
On the other hand, the total number of covered fields observed at least once during TFRM-PSES survey is 935.
 
Typically, the cadence we are implementing is one field exposure every 35sec.
 

Another exoplanet transit lightcurve observed by TFRM:

 
Analysis shows a differential photometric precision of ~10mmag for HAT-P-19b (V~12.9mag) on a non-photometric conditions. On Dec 25th 2011, the Telescope Fabra ROA Montsec (TFRM) observed the HAT-P-19b exoplanet transit in a completely unsupervised robotic mode. The first transit-like signatures of HAT-P-19b were detected by the Hungarian-made Automated Telescope Network (HATNeT, Bakos et al. 2004). Recent studies have showed this is a low-density Saturn-mass planets transiting metal-rich K star (Hartman et al. 2011). HAT-P-19b is a specially relevant target because of its moderately faint magnitude (V~12.9mag) lies in the middle of magnitude range of the above explained Super-Earths survey which the TFRM is currently conducting.

HAT-P-19b light curve
 
Fig. caption: The following plot shows the HAT-P-19b transit lightcurve observed by TFRM on Dec 25th 2011. The left side baseline is affected by cirrus presence.
 
 
The transit lightcurve spaned about 4.7 hours. The inferior performance in photometric precision with respect to former transits (10mmag vs. 3mmag) are due to cirrus presence on that night. This TFRM observation were conducted by the members of Fabra-ROA collaboration and thanks to the data analysis effort performed by Dr.Holger Voss (Departament d'Astronomia i Meteorologia, UB).
 

First exoplanet transit lightcurve observed by Telescope Fabra ROA Montsec:

 
Analysis shows a differential photometric precision of 4.3mmag for WASP-37b (V~12.7), and 3mmag for similar magnitude stars. On Apr 8th 2011, the Telescope Fabra ROA Montsec (TFRM) observed the WASP-37b exoplanet transit in a completely unsupervised robotic mode. The first transit-like signatures of WASP-37b were detected by SuperWASP survey (La Palma) between March and June in 2008 and 2009, and by WASP-S survey (South Africa) during 2008 June to July and 2009 March to July. Recent follow-up photometric and spectroscopic observations (Simpson et al. 2011) have unveiled that WASP-37 is one of the lowest metallicity stars hosting a transiting hot Jupiter (*M*p = 1.80 ± 0.17 *M*J) planet. Other exoplanets transits have been previously and successfully attempted by TFRM, but WASP-37b is specially relevant target because of its moderately faint magnitude (V~12.7mag) among the main bulk of exoplanets discovered by transit technique with ground-based surveys. We aimed to show that with the huge 4.4degx4.4deg field of view and moderately large aperture of TFRM hosts stars in the range of 12.5mag<V<14mag can be surveyed with high probability of new exoplanets transits detections on the basis of a single-night real-time strategy.
 
 WASP37 curve light

Fig. caption: The following plot shows the WASP-37b transit lightcurve observed by TFRM on Apr 8th 2011. Note that the left and right baseline is not completely spanned because that corresponds to a single-night observation.
 
 
Effectively, this has been the first time in which TFRM delivered a complete transit lightcurve in that magnitude range, spanning about 4.5 hours. The performance shown by the TFRM has been surprisingly outstanding for a first-time attempt and for a preliminary analysis: a differential photometric precision of 4.3 mmag for WASP-37b transit was found, and 3 mmag precision for several dozens of similar magnitude stars in the whole field of view. Aside from the first-time transit observation, what is most relevant is that, if WASP-37b planet were unknown, TFRM would have detected it as an exoplanet candidate on the very first night of observation, i.e. like a real-time detection without the need of further phase-folded data points of posterior nights.
 
Finally, and not less importantly, as a by-product of the 4.5 hours of photometric measurements of all the objects in the 4.4degx4.4deg field of view, ten variable stars of different types and magnitudes were detected. This TFRM observation were conducted by the members of Fabra-ROA collaboration and thanks to the data analysis effort performed by Dr.Holger Voss (Departament d'Astronomia i Meteorologia, UB).
Last Updated ( Wednesday, 23 April 2014 )
 
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