Category Archives: Clio

Getting ready for MagAO 2014B — spare Clio solid nitrogen pump

We’ve had a few meetings lately to prepare for our upcoming 2014B run in Oct–Dec. This will be our second regular science run, and our operations are becoming more smooth and efficient, so we are going to have a more streamlined personnel plan. It will also be our longest run yet (37 nights!).

We are laying in for spares and planning improvements in our operations. One spare Phil has gotten for Clio is a spare pump for pumping on the liquid nitrogen chamber in the dewar to bring the temperature of the detector from 77 K (liquid nitrogen) down to 55 K (solid nitrogen) by lowering the pressure. This spare pump is coming to us from the LBT where it used to be a vacuum pump, and while it is no longer strong enough to deliver a true vacuum, it is strong enough to lower the pressure to solidify the nitrogen in the dewar. It is a Leybold Oerlikon EcoDry M 30 Dry Piston Vacuum Pump.

New Clio pump technical info, from Phil:

The current Clio pump is specified to reach an ultimate vacuum of 5 Torr (7 mbar). This allows the solid N2 vessel to be at 50-51 K. We typically regulate ~5 K above this or 55 K. The new EcoDry pump has an achieved lab pressure of 0.11 Torr. This will put the solid vessel at ~42 K. This suggest we could regulate as low as 47 K on the detector.

Therefore, on this next run, we will explore new setpoints and the effect on detector performance. Thanks Phil!

Here are Laird and Kim (CAAO Project Specialist) working on shipping the spare Clio pump to LCO. It weighs ~130 lbs and is 50 cm long x 30 high x 30 cm wide, and uses 120 V AC. It will be quite at home in the pump room.

Posted in Clio, Hardware | Comments Off on Getting ready for MagAO 2014B — spare Clio solid nitrogen pump

Directly Imaged L-T Transition Exoplanets in the Mid-Infrared

2M1207 b (pronounced two-mass-twelve-oh-seven-bee) is often considered the first directly imaged extrasolar planet. Though its primary star, 2M1207 A, is actually a brown dwarf, b shares many properties with the HR 8799 planets. Andy Skemer analyzed images taken with MagAO+Clio2 and compared the results with images of the HR 8799 planets taken with the LBT. The interesting thing about 2M1207 b is that it doesn’t seem to have methane in its atmosphere — otherwise we wouldn’t have been able to see it since methane should absorb all the light at the wavelength we used.

Imaging 2M1207 b is extremely challenging from a technical standpoint. 2M1207 A is a faint brown dwarf, which doesn’t emit enough visible photons for our wavefront sensor. Instead, we locked on an off-axis (and still faint) star 40″ away from the science target. The result demonstrates that MagAO can produce reasonable Strehl ratio images on targets that are too faint to serve as their own guide-star.

2M1207 A, and its planetary-mass companion, 2M1207 b, the first directly-imaged exoplanet (Chauvin et al. 2004). When 2M1207 b was first discovered, it was noted to have unusually red colors, and to be extremely faint compared to other red (L-type) brown dwarfs. This image, taken by MagAO/Clio at 3.3 micron, would show a dark planet if 2M1207 b had properties similar to “normal” objects. Instead, we find the 2M1207 b is bright at 3.3 microns, suggesting an almost complete lack of methane gas.

Abstract: Gas-giant planets emit a large fraction of their light in the mid-infrared (≳3μm), where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. Of particular importance are the L and M-band atmospheric windows (3-5μm), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT AO images of the HR 8799 planetary system in six narrow-band filters from 3-4μm, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3μm band. These systems encompass the five known exoplanets with luminosities consistent with L→T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature. For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the object’s appearance. For the HR 8799 planets, we find that the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.

You can download the pre-print at astro-ph.

Posted in Clio, Results | Comments Off on Directly Imaged L-T Transition Exoplanets in the Mid-Infrared

Comm2 Day 17: Calibrating Clio while clouded out

We were clouded out tonight:

Tonight

Tonight

A few nights ago, for comparison

A few nights ago, for comparison

Also, a truck on the highway had an accident, which closed the highway, so the new turno couldn’t get here so the day crew had to also be the TO’s at night. We’ve been away from home for ~3 weeks and everyone is tired, but we stayed up all night in the control room working.

So, instead, I’ve been working on reducing my data, which includes determining various necessary calibrations for Clio. One important correction needed for high-contrast photometry is calibrating the linearity of the detector. To do this calibration, I took a set of measurements of increasing integration time, and determined the counts per itime:

Raw data that are not linear.

Raw data that are not linear.

I then fit various functional forms to the data until I found the best calibration of the linearity is a third-order polynomial that must be applied to pixels with counts above ~27,000 DN in the raw images, giving the result here:

The result of applying the linearity correction to the raw data.

The result of applying the linearity correction to the raw data. The linearity calibration must be applied to pixels with values above ~27,000 DN, and is not valid for pixels with values above ~45,000 DN for high-contrast photometry (there is margin up to ~52,000 DN for low-dynamic-range photometry).

Note that the data cannot be well-corrected above ~45,000–52,000 DN (depending on your tolerance for photometric error), and these values should be considered saturated in the raw images. I apply the calibration through an IDL function I wrote called “linearize_clio2.pro”. This is going onto the Clio observer’s manual.

Jared and I are working on astrometry, comparing Clio and VisAO measurements and exploiting our capabilities for boot-strapping: Clio has a wider field (up to ~30”) and can get a longer lever-arm on astrometric measurements, but VisAO has a finer pixel scale (~8mas) and a tighter PSF and can get precision astrometry on close companions. We are starting by verifying that we both get the same measurements for the locations of stars in the Trapezium cluster. To do this, I look at our Trapezium images and identify which star is which, then I compare the positions I measure to the positions measured by an earlier author. Here’s an illustration:

Measuring astrometry using Trapezium stars.  (Left) Trapezium as imaged at the LBT/PISCES in the IR a year or so ago by Laird.  (Right) Trapezium as imaged with MagAO/Clio here at LCO by me.

Measuring astrometry using Trapezium stars. (Left) Trapezium as imaged at the LBT/PISCES in the IR a year or so ago. (Right) Trapezium as imaged with MagAO/Clio here at LCO. Can you identify the stars in the picture on the right? (Ignore the black splotches which are negative star images, from the sky subtraction.)

I’ve measured the plate scale in both cameras and various filters, as well as the rotation offset to orient the images with north-up, which I’ve written in the IDL function “derot_clio.pro”. We’re working on a code repository for these data-reduction utilities that we’re calibrating on these commissioning runs.

In fact, Clio has two cameras, a wide and a narrow camera. Here is a comparison of the fields of view, including an illustration of the overlap:

The narrow field is shown within the wide field.

The narrow field (16” x 8”) is shown within the wide field (28” x 14”).

VisAO’s field of view is similar to Clio’s narrow camera along the short direction (8” by 8”).

Finally, I’ve been having a bit of fun experimenting with the APP coronagraphs that I want to use for following up GPI planets:

Fun with APP

Fun with APP

Well, it’s been a long night, good morning!

Posted in Clio, General | Comments Off on Comm2 Day 17: Calibrating Clio while clouded out