IRTF Observation Lab Report

IRTF Observation Lab Report
Joe Regan
September 03, 2015

Abstract

On the night of September 3, 2015, the weather was perfect to take observations using the Infrared Telescope Facility at the peak of Mauna Kea in Hawaii. Observations were taken through the night, from 5:46 to 10:08 a.m. Universal Time on several stars, including Vega, GJ 3942, GJ 740, GJ 725 A, and EV Lac. Flat images were taken between each star, and dark images were taken at the end of the night for use in error correction.

Introduction

When observations were taken, the radial velocity method was used on this handful of stars for the purpose of potentially detecting and confirming exoplanets orbiting M Dwarf stars. The star's spectrum is taken many times, and the absorption lines in the spectra are analyzed to attempt to detect a redshift or blueshift corresponding with the star's movement away from and towards us, respectively. This wavelength shift gives us the ability to measure the radial velocity of the potential planet surrounding the star and the lower limit of the planet's mass.

Procedure

The observing procedure is as follows:

1. Before we can make any observations, we must first make sure the weather is optimal for viewing. The weather of nearby observing nights has been less than ideal for observing due to El Nino. This night's weather was fine, and the humidity stuck around about 65% on average. If the humidity is above 95% on average, observations are potentially impossible for that night.
2. Second, the gas cell must be turned on, the wavelength must be input into CSHELL, and the IRTF operator on location must help to focus the telescope.
3. The telescope must then be aligned with the standard A star, in this case Vega, and images are taken in order to calibrate the telescope, align the star on the closed slit, and make sure the spectrum of the star is clear.
4. After making sure the spectrum is clear, we observe the science target. Doing this, we record the wavelength observed, the imaging mode, the number of cycles with the exposure time, the UT time of the observation, and the Signal-to-Noise Ratio (SNR). 
5. After observations are taken of the science targets, flats are taken. Flatfield images are normally taken of a continuum lamp or a bright light source of some sort in order to evenly distribute the light across the image.
6. Repeat steps 4 and 5 for all target stars.
7. At the end of the night, dark images are taken in order to determine the electric current through the detector when no natural light is let in.

Results and Conclusion

A handful of observations were taken of GJ 3942, GJ 725 A, and EV Lac over the course of the night, at a wavelength of 2.31292 microns and a slit width of 0.5 arcseconds. . Humidity hung right around 65% for the majority of the night, and the weather was clear of any clouds. Two spectral images were taken of GJ 3942, at 300 second exposures. Fifteen spectral images were taken of GJ 740 with 300 second exposure time. Twelve spectral images of GJ 725 A were taken at 200 second exposure time. Eleven spectral images of EV Lac were taken with 300 second exposure time. The total signal to noise ratio over the night was around 172. Between each star, 15 flats were taken between each star, with exposure time of 15 seconds. At the end of the night, 15 dark images were taken at 15 second esposure time. 

This particular data set should be useful, considering the great condition of the weather and humidity, and the SNR, while not quite the desired value, was fairly close to 200.