Multicolor Microvariability Observations of BL Lac Object: 1ES Whitney Wills Advisor: Michael Carini Western Kentucky University
Bell Astrophysical Observatory Manufacturer: Group 128 Primary Diameter: 0.6m f-ratio: 11 Design: True Cassegrain Started building process in 1975
Bell Astrophysical Observatory Refurbishment Apogee Ap2p CCD camera Image scale: 0.59arc/pixel, binned 2x2
Major Projects at Bell AGN Monitoring – Dr. Michael Carini Transiting Extra Solar Planets – Dr. Charles McGruder Monitoring of Wolf-Rayet Stars – Dr. Sergey Marchenko HOU – Dr. Barnaby –Jupiter and Saturn Week
Observations Student run sessions from WKU’s campus or onsite Exposures of 180sec in V and I filters Continuous monitoring for approximately 8 hrs
What are Active Galactic Nuclei? 1 Normal Galaxy
Normal Galaxies Spiral: M31 Elliptical: M87 Irregular: LMC
What are Active Galactic Nuclei? 1 Normal Galaxy + 1 Super Massive Black Hole at Center
Super Massive Black Hole
What are Active Galactic Nuclei? 1 Normal Galaxy + 1 Super Massive Black Hole at Center + 1 Accretion Disk
Accretion Disk
What are Active Galactic Nuclei? 1 Normal Galaxy + 1 Super Massive Black Hole at Center + 1 Accretion Disk + 2 Relativistic Jets of Material
Relativistic Jets
What are Active Galactic Nuclei? 1 Normal Galaxy + 1 Super Massive Black Hole at Center + 1 Accretion Disk + 2 Relativistic Jets of Material =AGN
Active Galactic Nuclei
What are BL Lacertae Objects? The most extreme example of an AGN Highly variable polarization Featureless optical spectra Highly variable continuum emission at all wavelengths
LBL vs. HBL Urry, C.M., Advances in Space Research, Vol. 21, Issue 1-2, p. 89, 1998
Why Study Them? Featureless continuum means continuum radiation is the only diagnostic Models of AGNs need data External Compton scattering model Radio and optical radiation up-scattered to gamma-ray radiation Predicts wavelength dependent lag Short timescales--microvariability
Microvariability Variations with timescales of hours Provide the tightest constraints on the size of the emission region
Reductions Image Reduction and Analysis Facility (IRAF) Removed background and thermal noise from the pictures (Bias and Dark levels) and removed non-linearity (flat field) Measured the brightness inside a circular aperture centered on the star
Before Reduction
After Reduction
Finding the Aperture Used an image examiner tool in IRAF Found the full width, half max of the point spread function of the object and each of the comparison stars Took the average of the fwhm and used it as the aperture radius in a parameter in IRAF
Calculating Differential Magnitudes & Errors Using the Phot tool in IRAF, magnitudes were found Using these magnitudes, the difference between the object and comp stars were found This new differential magnitude was then plotted against the UT time The standard deviation between each of the images was used for the error
OJ 287 (LBL)
1ES (HBL)
Light Curve – 1 ES I Filter
Light Curve – 1ES V Filter
Light Curves – BL Lac (LBL) Tosti, G. et al., BL Lac Phenomenon, ASP Conference Series volume 159 (1999)
Light Curves – MRK 501 (HBL) Miller, H. R. et al., BL Lac Phenomenon, ASP Conference Series, volume 159, 75 (1999)
Conclusions Need more data! Need to increase the exposure time to 240 seconds
Opportunities Work with 0.6m telescope that included gathering data and troubleshooting Actual experience with software professional astronomers use (IRAF) Experience presenting research at conferences at and away from WKU: Argonne Undergraduate Symposium (2002 & 2003) AAS: 2003 Summer & 2004 Winter Meetings Sigma Xi – Honorable Mention Posters at the Capital (2002 & 2003) WKU Student Colloquia Invited Speaker at NSSTC
Acknowledgements Telescope Operators: Dr. Michael Carini Dr. David Barnaby Whitney Wills Data Analysts: Dr. Michael Carini Whitney Wills This project has been supported by NASA, the Kentucky Space Grant Consortium and the Applied Research and Technology Program at WKU
Questions?