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.

 

EXOPLANET TRANSIT — TRES-1B OBSERVED SHORTLY AFTER DISCOVERY

Shortly after the Transatlantic Exoplanet Survey discovered a hot Jupiter (TRES-1B) transiting the K0V dwarf GSC 02652-01324 in 2004, the RCT was used to observe a transit, as shown in the diagram shown here. Scatter increased markedly over the time of observation as the airmass became large — typical transit observations at normal airmass will resemble the left side of the diagram.

The RCT is capable of detecting such transits reliably at least to the millimag level.

The end of peak oil

a130605105crop

Oil (probably from the last days of the old compressor) was removed from the dewar window by Don Walter at the end of May. This has eliminated the curious-looking ‘coffee stain’ present on recent images.

The above unreduced image of Zw229-015 gives a fair idea of current image quality.

epsboo-3

Current resolution with 2×2 binning (0.58 arcsec/pixel) is shown in this image of Eps Boo taken through the U filter. Separation is 2.85 arcsec.

RCT maintenance update

The new mirror support cell air compressor is now fully installed and operational. It is set to provide 12 inches of water (0.43 psi), a little higher than the nominal 10 inches of water (0.36 psi), and appears to be holding well. There is a refrigeration desiccant system on the compressor (to keep moisture out of the lines) that is not currently installed. It should be installed in the next few weeks, as soon as the proper fitting can be installed.

The problem with the dome encoder does not appear to be with the encoder itself, rather with the encoder input channel to the pmac. The pmac has 2 cards with 16 possible channels, of which 10 (or so) are in use by the various encoders. One card has only two encoders, the focus and the dome azimuth, and it appears that the input channel for the dome azimuth (#6) is corrupted. Brevin was able to remap that channel to an open channel (#8), which appears to have fixed the problem. The dome is now making repeatable rotations to the same commanded azimuth positions, without significant failure.

However, it now appears that the dome is no longer synced with telescope. The telescope points correctly, but the dome azimuth is significantly off, by as much as 90 degrees depending on location. This is repeatable for the same telescope positions, indicating that it is not a loss in encoder counts. Further, its correctable by commanding the dome to the telescope azimuth. This, unfortunately, does not provide a fix as tracking forces the dome to update its position, immediately rotating back to its previously determined, incorrect position.

It is not clear how the dome receives its commands, from the telescope azimuths or from its own pointing model, but in either case something is not responding correctly. I’m in discussions with Treffers to see what can be done.

Telescope down for maintenance

Following some thorough testing, we’ve determined that the dome occulting issues were due to a failing encoder that will be replaced this week. The failing unit has been removed, and the dome is currently off.

Further, our mirror support compressor has finally ceased to function. Brevin will purchase a replacement this week.

RCT Supports Summer 2012 Astronomy Camps

For the second summer in a row, the RCT was used by students attending the astronomy camps  directed  by Dr. Don McCarthy .  Four camps held in June and July engaged a total  93 teenagers from the US and five  foreign countries .  The RCT was used for temporal monitoring of two comets, a flare star and Saturn’s moon Titan. The picture below shows the campers at the 12-meter telescope observing the transit of Venus.  The other image is a mosaic of several nights of observing Titan in orbit around Saturn, which was part of a project using Kepler’s Third Law to determine the mass of Saturn. Titan is shown as different colored dots which represent four different epochs of observations

Update on dome

After many tests, we now think either the dome encoder is failing or the dome power supply is incorrectly set, following the powerout for the UPS replacement. More updates soon.

The pointing was recentered (off after worm-gear lubrication work) and the focus was readjusted (for seasonal drift).

RCT update on blank images/guiding

Folks,
Several have noticed the following behavior in the last few nights with the RCT:

  • Several images are blank, likely with the dome completely in the way
  • The centering of the field seems to drift from night to night
  • At high hour angle, there is significant trailing in the images. There is still notable “coma” in images near zenith
  • I believe these are all symptoms of the encoder slippage and worm gear oscillation. I believe they needing cleaning/re-greasing. I’ve put in a service request with KPNO. I still think part of the PSF is mirror support related, but we wont know for sure until we eliminate the other sources of confusion.

    Tonight I was able to zero point the telescope, and test the guider. It appears that the pointing tolerance for accurate guiding is about 15″, or ~20 pix from the absolute center of the chip. Guiding works better now, but it does not improve the PSF substantially.