First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward...
-
date post
22-Dec-2015 -
Category
Documents
-
view
213 -
download
1
Transcript of First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward...
![Page 1: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/1.jpg)
First Detection of a Starspot During Transits of an Extrasolar
Planet from the Ground
Steward Observatory
Undergraduate Symposium
Jason Dittmann
Undergraduate Advisor: Laird Close
Elizabeth Green, Mike Fenwick
Paper submitted to ApJ Letters
![Page 2: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/2.jpg)
What is a Transit?
![Page 3: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/3.jpg)
TrES-1b
• First extrasolar planet detected using the transit method Alonso et al. (2004)
![Page 4: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/4.jpg)
Photometric Anomalies
![Page 5: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/5.jpg)
![Page 6: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/6.jpg)
Photometric Anomalies• Many observers
have noticed brightening anomalies during transits of TrES-1b. (Price et al. 2004)
• Hubble ACS data has shown brightening anomalies during transit (Rabus et al. (2009)
![Page 7: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/7.jpg)
Photometric Anomalies
• Winn et. al (2007) observed 3 consecutive transits in the Z band with the 1.2 meter telescope at FLWO.
• No evidence for photometric anomalies
• However, if these anomalies are starspots, they would be less sensitive to them in the Z-band
![Page 8: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/8.jpg)
Photometric Anomalies• In 2007, ASTR 302 students also observed strange anomalies
in a TrES-1b transit
![Page 9: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/9.jpg)
Our Observations• Observations taken at
the 61” Kuiper Telescope on Mt Lemon with the Mont4k CCD.
• 2 consecutive transits (May 12 and May 15, 2008 UT)
• Images taken in the R-band
• Light clouds on May 12, photometric on May 15.
![Page 10: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/10.jpg)
Reductions
• 2σ clipping applied to reference stars
• Data points for TrES-1 were not clipped
• TrES-1 flux normalized to the weighted average of the reference stars
TrES-1
![Page 11: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/11.jpg)
Analysis
• Transits fit with the method described by Mandel and Agol (2002)– RMS noise varied between 2 and 3 mmag– Excluding the anomaly data points
• Therefore, the time of the anomaly in the transits can tell us the rotation period of TrES-1.
![Page 12: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/12.jpg)
![Page 13: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/13.jpg)
![Page 14: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/14.jpg)
Geometry
![Page 15: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/15.jpg)
![Page 16: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/16.jpg)
Relevent Formulas
The factor of R_p / R_* cos(lat) corrects for the fact that ingress is when the leading limb of the planet crosses the star while egress is when the trailing limb of the planet leaves the star.
![Page 17: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/17.jpg)
Rotational Period
• Prot = 40.2 +/- 0.1 days
• But, the subtended angle depends upon the angular tilt of the star– Yields P = 34.8+4.9
-9.5 days
– Consistent with previous measurement of 33+25-16
days
• If TrES-1 had made 2 full rotations between observations, the period would be 2.84 days– Unlikely for an old K0V star
![Page 18: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/18.jpg)
Size of Starspot
• Approximate spot as 100% black
• Peak Brightening ~5.4 mmag
• Depth of transit ~25 mmag
• The ratio of the brightening to the depth is equal to the ratio of the spot size to the size of the planet.
• Rspot >~ 6 Rearth
![Page 19: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/19.jpg)
Could this be random noise?
• Brightening anomaly detected at:– 3.2σ May 12 and 2.9σ May 15
• This is ~1σ above other noise bursts in our data set– It is not rare for TrES-1 to have a large
starspot or starspot group on its surface.
![Page 20: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/20.jpg)
Results
• The cause of the brightening anomaly during transits of TrES-1b is confirmed as large starspot(s).
• This is the first instance in which starspots during planetary transits have been observed from the ground.
• The period of TrES-1 is 34.8+4.9-9.5 days
![Page 21: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/21.jpg)
Final Comments• Starspots are a new source of noise for
planetary transit data– Understanding and modeling them will be
of use to the Kepler mission in finding extrasolar Earths.
• This result was encouraging enough to try to observe a transit whose depth is equal to the anomaly height itself!
![Page 22: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/22.jpg)
And it worked!
![Page 23: First Detection of a Starspot During Transits of an Extrasolar Planet from the Ground Steward Observatory Undergraduate Symposium Jason Dittmann Undergraduate.](https://reader030.fdocuments.us/reader030/viewer/2022032523/56649d7e5503460f94a61e9c/html5/thumbnails/23.jpg)
Thanks!
Questions?
We’d like to thank Trevor Olson and Louis Scuderi for helping to take data during May