Here are brief descriptions of scientific results obtained with MagAO, Clio, and VisAO. At the end of each you will find links to the science paper, including freely downloadable preprints.
It is rare for MagAO to carry out extragalactic observations because suitable natural guide stars are hard to find.
But this time we have got some luck. A week ago (February 8), a bright supernova, SN 2016adj, appeared in the active galaxy NGC 5128 (Centaurus A). Classified as Type IIb, its progenitor is believed to be a very massive star in a binary system, undergoing a significant mass loss before explosion. However, direct identification of the progenitor remains challenging, even though astronomers have been constantly detecting supernovae in imaging surveys.
Since SN 2016adj is only 4″ from a bright foreground star, it is an ideal target for our visible AO camera. Prompted by Prof. Nathan Smith, we used MagAO to observe the supernova on February 13, and successfully took ~2 hr deep exposures at 0.9 micron. Comparing the new MagAO image to archival HST and VLT data, we and our collaborators were able to identify a possible progenitor star. Notably, this is the 5th Type IIb progenitor identified in pre-explosion images over the past 20 years.
We used MagAO to identify the progenitor star in this pre-explosion image taken by the Hubble Space Telescope.
MagAO’s revolutionary visible light capabilities have allowed us to directly image a planet residing inside a circumstellar disk gap for the first time. These images, of the forming protoplanet LkCa 15 b, provide the first incontrovertible evidence of accretion onto a forming planet.
In fact, the study joined two independent results from Arizona facilities – interferometric data from the Large Binocular Telescope on Mt. Graham in Arizona and direct images from our very own MagAO system at Las Campanas Observatory in Chile.
The MagAO data was obtained by myself (Kate Follette), Laird Close, Jared Males, and Katie Morzinski as part of the Giant Accreting Protoplanet Survey (GAPplanetS). The final product: images of the forming protoplanet LkCa15b glowing in the light of ultra hot hydrogen gas. This is an indication that the planet is still growing, because Hydrogen gas glows at this characteristic wavelength of light when it is in the process of falling onto a massive object – in this case a protoplanet! LkCa15 b is visible glowing in Hydrogen-alpha, but unlike our previous discovery of HD142527B, it is NOT glowing in ordinary visible light. This indicates that the underlying object is very low mass – the first true GAPplanet!
Read about the entire study, which combined our H-alpha data with near-infrared interferometric data from the Large Binocular Telescope collected by Steph Sallum and Josh Eisner, at the links below. Steph and Josh were able to isolate light from two more protoplanet candidates – LkCa15c and d, and saw LkCa15b in the same place as the MagAO direct images, providing independent confirmation of its identity as a forming protoplanet!
I am happy to announce the acceptance of Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. Paper II by the Astrophysical Journal. This paper presents the 0.9-5 micron spectral energy distribution (SED) of young giant exoplanet beta Pic b. We carefully calibrated Clio (see the Appendix), analyzed our photometry, combined it with other works’ photometry, and measured the total brightness of the planet at all wavelengths — the bolometric luminosity. Here are the images of the star and planet:
Images of the star beta Pic (Left: saturated; Center: Unsaturated) and its planet beta Pic b (Right) with MagAO. In this study we analyze the photometry in order to measure the total luminosity of the planet at all wavelengths (Figure 1 from the paper).
Here is the star’s SED and the planet’s SED: Top: SED of the star (Figure 2 from the paper). Bottom: SED of the planet (Figure 3 from the paper).
We measured the bolometric luminosity empirically by integrating the SED and extending with a best-fit blackbody: Empirical Bolometric Luminosity (Figure 8 from the paper).
This is the first time the luminosity has been measured empirically, and it is in agreement with the luminosity from models but about 20% brighter than brown dwarfs of a similar temperature (the bolometric correction, abbreviated B.C. in the table): Physical parameters of the planet according to different works (Table 15 from the paper).
Abstract: Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet beta Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star beta Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the first CCD detection of this planet with MagAO+VisAO. Here we present four MagAO+Clio images of beta Pic b at 3.1 um, 3.3 um, L’, and M’, including the first observation in the fundamental CH_4 band. To remove systematic errors from the spectral energy distribution (SED), we re-calibrate the literature photometry and combine it with our own data, for a total of 22 independent measurements at 16 passbands from 0.99-4.8 um. Atmosphere models demonstrate the planet is cloudy but are degenerate in effective temperature and radius. The measured SED now covers > 80% of the planet’s energy, so we approach the bolometric luminosity empirically. We calculate the luminosity by extending the measured SED with a blackbody and integrating to find log(L_{bol}/L_{Sun}) = -3.78 +- 0.03. From our bolometric luminosity and an age of 23 +- 3 Myr, hot-start evolutionary tracks give a mass of 12.7 +- 0.3 M_{Jup}, radius of 1.45 +- 0.02 R_{Jup}, and T_{eff} of 1708 +- 23 K (model-dependent errors not included). Our empirically-determined luminosity is in agreement with values from atmospheric models (typically -3.8 dex), but brighter than values from the field-dwarf bolometric correction (typically -3.9 dex), illustrating the limitations in comparing young exoplanets to old brown dwarfs.
K. Morzinski et al., “Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet”
ApJ 815, 108, 2015 ; ArXiv Preprint ; ApJ
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”
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, 2015arxiv preprint
