Category Archives: Uncategorized

HUBBLE’S DISAPPEARING CEPHEID — THE STRANGE CASE OF M33 V19

In this post we summarize continuing efforts to monitor the strange behavior of M33 V19 in B and V using the RCT. With the ability of a robotic telescope to do time series observations, we hope to gain a better understanding of this ‘previously-a-Cepheid’ object’s unprecedented evolutionary behavior.

In 1926, Hubble determined the distance to M33 using 35 Cepheids he discovered, one of which was his Variable 19, with a period of 54.7 days, an amplitude in B of 1.1 mag, and a mean B magnitude of about 19.6. DIRECT project observations in 1996-7 with the 1.2m Whipple and 1.3m MDM telescopes and RCT observations, together with other data, clearly show that the star’s amplitude has diminished to less than 0.1 mag, while the star’s mean
brightness increased substantially.

Below is a another figure showing photometry of a fainter nearby Cepheid from both the RCT and the DIRECT project, showing that photometric quality is comparable.

MONITORING A SUPERNOVA IN M101

SN2011fe

RCT observations of SN2011fe in M101 show the power of queue scheduled observations. The SN is circled in the above image. Diagram from Strolger et al. (2014, in press). RCT observations are shown as solid circles with error bars, while AAVSO observations are shown for comparison.  Click for a sharper view of the figure below.

sn2011felarge

LIVING WITH A RED DWARF

PIA13994
Red dwarfs (dwarf M stars) are by far the most numerous stars in our Galaxy, comprising more than 75% of all stars. These diminutive low mass stars have very slow nuclear fusion rates and thus very long lifetimes.Because of their long stable lifetimes, it is possible that planets
hosted by older dM stars could harbor life.
But to assess this possibility on planets in the ‘Habitable Zone’ orbiting a red
dwarf, we need to characterize the radiative environments these planets would be
subject to as the host star evolves. This will tell us what the likelihood is that complex
molecules can form, and whether life can evolve and have reasonable chance of
survival.
RCT research in the LWARD program is focused on monitoring the brightness of
red dwarfs of known age, and determining their rotation periods. For this purpose
the queue scheduling and routine monitoring capabilities of the RCT are extremely
useful in building up time series that can help calibrate an age-rotation relation.