Blog – Page 131 – Extreme Wavefront Control Lab

New Coronagraphs for 2015B (and 2015A)

We have just finished designing, and are fabricating, new vector apodizing phase plate (APP) coronagraphs for Clio2. We plan to install these during the last week of April, 2015, prior to the 2015A run. We will be commissioning and characterizing them at the beginning of the run. They will be available for observations on a shared-risk basis during 2015A and 2015B. In addition to the usual authorship procedures for MagAO, during 2015A and 2015B any observations with the APPs will include our collaborators at Leiden Observatory (6 additional authors) who have led the development this new type of APP.

The major improvment over previous generations of APPs is the use of liquid crystal technology, and the exploitation of polarization to allow 360 degree observations. We are procuring two new optics.

vAPP A: the first of the new vAPPs is designed to work at 2 lambda/D, with raw contrasts of 1e-5 or better out to roughly 1 arcsecond. This device will work from Ks to M’. We expect best performance in narrow filters. By splitting the beam with a half waveplate integral to the APP, two opposite dark holes are created. Here we show predicted raw PSF contrast including contamination from the other PSF. The simulated image shows the notional layout of the 2 vAPP PSFs on the Clio2 detector, at two different nod positions. All calculations shown here are by Gilles Otten at Leiden. NOTE: these calculations do not model effects such as non-common-path aberrations, residual wavefront errors, and various pupil features. On-sky performance will be worse than shown here.

Contrast at 90 degrees (middle of dark hole)

vAPP B: the second device is primarily a technology demonstrator. It actually has two masks on one substrate. One mask will test a new fully 360 dark hole. The other mask will test using an APP for focal plane wavefront sensing.

Multiwavelength Observations of NaSt1 (WR 122): Equatorial Mass Loss and X-rays from an Interacting Wolf-Rayet Binary

Fig 6 — Upper panels: MagAO Ks , L’ , and M’ images of NaSt1 in false color. The images are 2.7 arcsec square in angular size and oriented in detector coordinates. Lower panels: the Ks-band image of NaSt1 with logarithmic intensity contours (left) and the HST [N II] narrowband image with the Ks contours overlaid (right). An ellipsoid of extended Ks emission is clearly resolved, and is approximately aligned with the major axis of the optical nebula. The lower images are oriented with north up and east toward the left.

Abstract: NaSt1 is a peculiar emission-line star embedded in an extended nebula of optical [N II] emission with a compact dusty core. This object has been characterized as a Wolf-Rayet (WR) star cloaked in an opaque nebula of material that shows signs of advanced nuclear processing in the core of a massive star. To discern the morphology of the [N II] nebula we performed narrowband imaging using the Hubble Space Telescope. The images reveal that the nebula has a disk-like geometry, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Near-infrared imaging with Magellan AO resolved a compact ellipsoid of Ks-band emission aligned with the larger [N II] nebula. The source is more compact at L’ and M’, so we suspect the Ks-band emission result of neutral helium emission from the inner stellar wind scattered outward by reflection off of cool dust in the nebula. Observations with the Chandra X-ray Observatory have revealed a hard X-ray point source at the core of the nebula that is consistent with WR stars and massive binaries where powerful stellar winds collide and make X-rays. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer (the transfer is not completely efficient, and some material is lost from the binary system through the outer Lagrange points). NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction.

Mauerhan, J., et al. “Multiwavelength Observations of NaSt1 (WR 122): Equatorial Mass Loss and X-rays from an Interacting Wolf-Rayet Binary”

MNRAS 450, 3, 2551; arxiv preprint

New Results In The Chamaeleon

Now that the MagAO team has (mostly) recovered from our epic 6 week stay at LCO, we are turning our attention to processing all of the great data we’ve been taking. We’re also happy to announce two new publications based on MagAO data which have been accepted to the Astrophysical Journal, both of which looked at stars in the constellation Chamaeleon.

Ya-Lin Wu has been studying the young star CT Cha with VisAO. You can read about his results here.

Steph Sallum used Clio2, in combination with some other instruments, and used a resolution-boosting technique called non-redundant masking to take a look at T Cha. You can find out about her results here.

We have a bunch of other papers in the works, and we’re already starting to plan for our next run, which starts May 3rd. Stay tuned!

New Spatially Resolved Observations of the T Cha Transition Disk and Constraints on the Previously Claimed Substellar Companion

orbital — χ2 slices at the fixed contrast ratio for all L observations as well as 2013 NaCo Ks observations, with filled contours at 1 to > 4σ confidence limits. The line indicates a circular orbit in the plane of the outer disk. The ×s show the initial position of the putative companion from our re-reduction of the 2010 NaCo L data, while the circles show the predicted position(s) of a planet on the orbit. We plot two since the planet could be orbiting in either direction.

Abstract: We present multi-epoch non-redundant masking observations of the T Cha transition disk, taken at the VLT and Magellan in H, Ks, and L’ bands. T Cha is one of a small number of transition disks that host companion candidates discovered by high-resolution imaging techniques, with a putative companion at a position angle of 78 degrees, separation of 62 mas, and contrast at L’ of 5.1 mag. We find comparable binary parameters in our re-reduction of the initial detection images, and similar parameters in the 2011 L’, 2013 NaCo L’, and 2013 NaCo Ks data sets. We find a close-in companion signal in the 2012 NaCo L’ dataset that cannot be explained by orbital motion, and a non-detection in the 2013 MagAO/Clio2 L’ data. However, Monte-carlo simulations show that the best fits to the 2012 NaCo and 2013 MagAO/Clio2 followup data may be consistent with noise. There is also a significant probability of false non-detections in both of these data sets. We discuss physical scenarios that could cause the best fits, and argue that previous companion and scattering explanations are inconsistent with the results of the much larger dataset presented here.

Sallum, S., et al. “New Spatially Resolved Observations of the T Cha Transition Disk and Constraints on the Previously Claimed Substellar Companion”
ApJ, 801, 85, 2015 arxiv preprint

New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System

Hard work. — CT Cha in MagAO filters. Image contrasts are adjusted to bring out the objects.
Top row: unsaturated dataset showing the PSF. Middle row: reduced, saturated dataset
before any halo subtraction. Bottom row: primary’s halo removed by subtracting a rota-
tionally symmetric PSF.

Abstract:
We used the Magellan adaptive optics (MagAO) system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r’, i’, z’, and Ys. With our new photometry and Teff~2500 K derived from the shape of its K-band spectrum, we find that CT Cha B has Av = 3.4+/-1.1 mag, and a mass of 14-24 Mj according to the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r’ detection indicates that the companion has significant Halpha emission and a mass accretion rate ~6*10^-10 Msun/yr, similar to some substellar companions. Proper motion analysis shows that another point source within 2″ of CT Cha A is not physical. This paper demonstrates how visible wavelength AO photometry (r’, i’, z’, Ys) allows for a better estimate of extinction, luminosity, and mass accretion rate of young substellar companions.

Wu, Y.-L., et al. “New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System”
ApJ, 801, 4, 2015 arxiv preprint