Agile: A Time-Series CCD Photometer to Study Variables Anjum Mukadam, Russell Owen, Ed Mannery University of Washington, Seattle

Talk dedicated to Dr. R. E. Nather The concept of Agile is based on Argos, a time- series photometer at the 2.1m telescope at McDonald Observatory. Nather & Mukadam 2004, ApJ, 605, 846

Plan of Talk Difference between imaging and time- series photometry Why build a time-series photometer? Requirements of a good time-series photometer Instrument Design Just commissioned on March 19 at the Apache Point Observatory 3.5m telescope

Photometry vs. Time-series photometry Good CCD photometer High quantum efficiency Suitable resolution for well sampled PSFs Sufficiently large Field-Of-View for several comparison stars Good time-series CCD photometer (in addition to above) Good Timing Accurate start time Precise exposure duration No mechanical shutters, no time-shared data computer! Good time Short exposures & negligible dead time ResolutionSmall read time & Low read noise

Time-Series Photometer on the McDonald 2.1m VS. Low resolution spectrograph on HET in imaging mode (9.2 m)

S/N higher for Time-Series Photometer on the 2.1m by a factor of 1.5!

Agile: Field of View & Platescale 1024 x 1024 active pixels (pixel size 13μ x 13μ) Nasmyth focus of the 3.5m telescope at Apache Point Observatory Present Field of view 1.3 arcmin x 1.3 arcmin & Platescale arcsec/pixel Two-element Focal Reducer planned for May FOV 2.6 arcmin x 2.6 arcmin Platescale 0.15 arcsec/pixel

Instrument Timing Frame transfer initiated by using GPS synchronized pulses (1 microsecond uncertainty in hardware; expect ≤1 millisecond uncertainty in software) A new exposure starts and the previous one ends with the arrival of a new pulse. Pulses control exposure start time and duration.

GPS synchronized pulses to trigger frame transfer Analog pixel values from the CCD camera Digitized pixel stream leaving the electronics controller for the computer

Agile: Read Noise & Read Rate (16 bit digitization) Readout time 1.1s (unbinned full frame) Read Noise ~8 e - 1 MHz Readout time 11s (unbinned full frame) Read Noise ~5 e KHz Thermoelectric cooling, T CCD ~ -45C Dark count 1-2 counts/s

Wavelength Response: As Blue As Possible

Mounting Agile at the 3.5m in 10 minutes

Noise in light curves as a function of magnitude Log RMS Scatter 2015 Agile Nasmyth APO 3.5m (expected) Argos PFC McD 2.1m

First Light for Agile on March 19 G117-B15A, APO 3.5m, 10s exp, BG40 filter

Motivating science for a time-series photometer Pulsating stars, Asteroseismology (Only systematic way to study the stellar interior) Cataclysmic Variables Planetary transits Stellar flares

Indian Astronomical Observatory: World’s highest optical telescope at ft

Data through some clouds: G232-38

Short is relative!