星網計劃The NETS Project:

The NEtwork of Transit Survey 江瑛貴

Ing-Guey Jiang

National Tsing-Hua Univ., Taiwan

Outline

1. Introduction

2. Why transit ?

3. Why another transit survey ?

4. Tsing-Hua Station

5. The Previous Progress

6. The Next Step

Why Transit ?

• It is simple & fast

• can scan more stars

• It can determine the planetary orbital plane

• And also size & mass of planets

• It could be done by smaller telescopes

• So, the cost is low

• The timing of transit might be useful

TrES Network

• The Trans-atlantic Exoplanet Survey (TrES) • Wide-field photometric surveys by small telescope

s• Maximizing the monitered stars • Minimizing the time required of large telescopes• 3 small telescopes (10 cm) at (1) Tenerife, Spain;

(2) Lowell Observatory, Arizona; (3) Mount Palomar, California

• field of view: 6 degree• Spatial resolution: 11 arcsec/pixel

TrES-2

HAT-P-9b

• HAT: Hungarian-made Automated Telescope

• NATnet: 6 small (11 cm), wide field (8 by 8 deg) telescpes

• Data was taken in 2004 and 2005

• Transit was found from data

• Then, do following up

Why Another Transit Survey ?

• The current on-going projects can only monitor up to a few tens thousand stars

• To do a better job, we hope to monitor 10,000,000 (for 7 cm telescope) or 160,000,000 (for 12 cm telescope) stars

• This will improve the statistics in the field of exoplanets

• We hope to constrain long period exoplanets, too• We need a lot of time but small telescopes

Another Way of Sky Survey ?

• Permanent non-tracking fixed telescopes• Drift Scan• Scan stars while the Earth Rotating• Can monitor much more stars automatically• Use an array of telescopes to continue the

monitoring• It only suitable for certain events if the time

scales are right• Data analysis is slightly more complicated

Would we miss any planets ?

• Yes, but … (comparing with other projects)• For short period planets, the transit event

would repeat. We will detect them finally. • For long period planets, the transit

probability is much lower, so need to scan much more stars.

• We get some constraints on the number of possible planets with longer periods

Tsing-Hua Station

Image Taken at Tsing-Hua

Preliminary Analysis

• Sky Backgroud 3000 ADU

• Many stars have 40000 to 50000 ADU

• So, S/N is more than 10

• It is possible to do observations at Tsing-Hua Station

• Flux variation is about several percent

• The same order as O’Donovan et al. (2006)

a light curve

The Previous Progress

• Oct. 2006: A prototype CCD-lens system is constructed

• Jan. 2007: It took some testing data at Lulin• Feb. 2007: Starting the code development for data

analysis (on going)• March 2007: Starting to plan the enclosure• April 2007: Observe with other telescopes• Oct. 2007: Theoretical Modeling of light curve

The More Previous Progress

• July 2007: Weather Station arrived

• Aug. 2007: WebCam (USB and PCI)

• Nov. 2007: New Computer

• Dec. 2007: Constructing the Enclosure

• March 2008: Code for Enclosure Control

• June 2008: CCD Install

• Nov. 2008: Tsing-Hua Station Working

The Automatic Observation

• Setting the time interval of observation

• Open the enclosure on time

• Only open when weather & UPS are o.k.

• Start CCD whenever the enclosure is open

• Stop CCD, stop taking images

• Close due to weather condition, UPS

• Close and stop observation when time is up

The Weather: Humidity

The Weather: Temperature

Enclosure Testing

The Next Step

• Developing the data pipeline• Developing the codes• With the HAT results and our testing data, it is

feasible. • We shall prepare to construct an oversea station,

which will lead to scientific data• We shall think/talk about following up facilities