Exhaustive Monitoring of Polaris in Night Sky Live CONCAM Data R. J. Nemiroff, L. Shamir, V. Muzzin, M. Merlo, S. V. Tilvi, & The Night Sky Live Collaboration

Web address: People: Faculty: Robert J. Nemiroff (PI: Michigan Tech), Noah Bosch (Tel Aviv U.), Wellesley Pereira (Michigan Tech), J. Bruce Rafert (Clemson), John Oliver (Florida), Chris Impey (Arizona) Graduate students: Lior Shamir (MTU), Shet Tilvi (MTU) Undergraduate students (MTU): Dan Cordell, Vic Muzzin, Matt Merlo The Night Sky Live Project

Abstract Polaris is automatically monitored every clear night throughout the year by every northern CONtinuous CAMera (CONCAM) in the Night Sky Live global network. The coverage of Polaris is unprecedented, typically returning over 100 observations per station per night for every clear night. Of the seven northern CONCAM stations, the Kitt Peak (KP) CONCAM created the most frequent and reliable automated photometry measurements for Polaris in Individual photometric measurement had a statistical accuracy of about 0.03 magnitude (broadband), while measurements combined over a night typically yielded a statistical standard error of about magnitudes. Still, data suffered from a nightly systematic error of about 0.02 magnitudes likely caused local fluctuations in atmospheric opacity. Nevertheless, we find that Polaris varied significantly more than constant comparison star Alpha Cas. Preliminary analysis of the data indicate that Polaris showed an intrinsic variation of about / magnitudes between September 2004 and December 2004 with a period consistent with 4 days. This variability is in contrast with some extrapolations from earlier variability that indicated that the variability of Polaris would be well below this level by 2004.

The Night Sky Live Project This plot shows the frequency that an averaged night of photometry for Polaris and Alpha Cas were within a given standard error of the average photometry for the previous night. The plot shows that Alpha Cas is significantly less variable than Polaris in 2004 data from the Kitt Peak CONCAM.

Three General Objectives Primary Science Temporal monitoring and archiving of entire visible sky down to visual magnitude 6. Search for meteors, unusual stellar variability, GRB OTs, comet variability, novae, supernovae, etc. Support Science Instantaneous cloud monitors, archival cloud monitors, generate real-time all-sky opacity and skyglow maps Education / Outreach Show your class last night ’ s (real) sky, archival skies, monitor meteor showers in real time, show educational sky movies, run educational modules The Night Sky Live Project

If you need us to point out Polaris, you’re at the wrong conference.

CONCAM Locations The Night Sky Live Project Ten NSL nodes are currently deployed -- more are being built

Four of the Ten CONCAM locations Kitt PeakMt. Wilson Mauna KeaWise Obs. The Night Sky Live Project

Alpha Cassiopiae (also known as Shedir) is our comparison star and assumed to be constant beyond the accuracy we could measure.

The Night Sky Live Project A ratio of photometric measurements of Polaris (Alp UMi) to Alp Cas for the Haleakala CONCAM.

The Night Sky Live Project Each data point represents an average over an entire night. Each exposure runs 3m56s: some nights top 100 exposures.

Polaris: Historical Background Polaris, arguably the most famous star in the sky, is still mysterious in many ways. Polaris, also known as Alpha Ursae Minoris, is the brightest Cepheid. As such, understanding Polaris has importance in calibrating the entire cosmological distance ladder. Oddly, Polaris does not vary like most other Cepheids, but rather in a “ first overtone ” mode (Feast 1997). Polaris is actually a multiple star system, but the brightest F star is the Cepheid. It has been suggested (Davis et al. 2002, Engle et al. 2004, Evans et al. 2002) that Polaris is changing both its amplitude (currently about 0.03 magnitudes), period (currently about 4 days), and even average brightness (currently V=2.0) over the past 100 years. Polaris is too bright for large telescopes to make reliable photometric measurements. The Night Sky Live Project

Polaris: Future Prospects with CONCAMs The Night Sky Live CONCAMs will likely continue to offer the most complete time coverage of Polaris into the indefinite future, monitoring the enigmatic star 24/7 when weather permits. Our main inhibitor is systematic error due to atmospheric opacity changes. We see at least two ways of reducing this systematic error in the future. First, instead of using just a single comparison star, CONCAM data across the whole sky could be utilized to create a more accurate whole-sky photometric solution. An effort along these lines is already ongoing with the automatic creation of our all-sky opacity maps as part of our support observations mode, but is not yet reliable enough for 0.02 mag corrections. Second, since Polaris is typically seen by more than one CONCAM simultaneously, there exists the possibility of correlating parallel photometric measurements. The Night Sky Live Project

References Davis, J. J., Tracey, J. C., Engle, S. G., Guinan, E. F. 2002, AAS 201, # Engle, S. G., Guinan, E. F., Koch, R. H. 2004, AAS 204, # Evans, N. R., Sasselov, D. D., and Short, C. I. 2002, ApJ 567, Feast, M. W., Catchpole, R. M. 1997, MNRAS 286, L1. The Night Sky Live Project

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