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Gemini e-Newscast #90
December 15, 2016
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Unscrambling a Complex Young Stellar System
Nicole Arulanantham of Wesleyan University (Middletown CT, USA) led a team that targeted the binary T Tauri system known as V582 Mon (KH 15D) with the Gemini Near-InfraRed Spectrograph (GNIRS) on Gemini North. Arulanantham et al. obtained data at three different orientations of the system’s two young stars – allowing the team to study a number of key aspects of this complicated system. These included; characterising the photosphere and magnetosphere of the companion star (B), exploring a jet of material associated with a bipolar outflow, and probing the scattering properties of the circumbinary ring. This led to the quantifying of an observed excess in near-infrared radiation that is likely the signature of a self-luminous hidden 10-Jupiter-mass protoplanet. While this unresolved planet displays the expected excess in infrared radiation, as well as a 2 micron spectral feature that may be due to methane or ammonia, other anticipated signs of these two compounds went undetected in the observations.
The team’s spectroscopic observations also revealed spectral features indicating a mixture of water and methane ice grains within the circumbinary ring where the frozen methane exists close enough to the primary stars that it must be shielded by dust from direct radiation.
In addition to determining that star B is an early-K type subgiant, the research revealed evidence that star B’s magnetosphere experienced variable helium I emission due to ongoing mass accretion. The team’s paper is accepted for publication in The Astrophysical Journal. The preprint is available here.
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The top panel shows the spectrum of KH 15D during its "bright" phase, when the amount of direct starlight was greatest. The middle spectrum ("intermediate" phase) was taken when star B was just below the edge of the ring. Both spectra in the bottom panel were obtained during "faint" phases from two different cycles, when both stars were near periastron and the contribution from starlight was minimized. The spectrum from November has been offset by 1.5x10-15 W m-2 μm-1 for comparison to the data from December.
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Making the Most of Poor Weather Nights
Clouds and poor seeing can frustrate any astronomer on a classical observing night. One of the main strengths of Gemini's queue observing is that your program is observed in the conditions it requires. While the worry of bad weather nights may not be as much of an issue for Gemini users, thick cloud and poor seeing still strike from time-to-time on Maunakea and Cerro Pachón. There are times during these less-than-ideal conditions when there are simply no targets in the regular queue programs to observe. However, even in the worst conditions, Gemini makes the most of the night by observing Band 4 or Poor Weather proposals (if available). Band 4 programs can be submitted at any time during the semester and are most welcome during periods of bad weather (please read the following story in this e-Newscast!). If you have a science case with bright targets that can handle CC (Cloud Cover)=70%, 80% or "Any" and IQ (Image Quality)="Any" and WV (Water Vapor)="Any" (no restriction on SB (Sky Background)) or CC="Any" and WV="Any" (no restriction on IQ and SB) then consider submitting a Band 4/Poor Weather program today. More details on the proposal submission process can be found at this link.
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Thick clouds captured by Gemini North’s cloud cameras
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Winter Blasts Maunakea
The tilt of our planet’s axis has once again delivered an extended period of weather not conducive to astronomical observing on Maunakea. Starting in late November a series of fronts, troughs, and low-pressure systems have produced overcast skies, wind, and, most recently, significant snow (with drifting) at the Gemini North site. In the past month (since mid-November) 16 nights have been entirely lost to weather, and an additional four have been more than half lost. Overall, we have only managed to obtain science for about one-third of the available time.
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This image is a screenshot taken from footage from the UH88 camera pointed at the Gemini North telescope, dated Friday, December 9, 2016.
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Visit Gemini Staff at the 229th Meeting of the American Astronomical Society Meeting
Gemini staff look forward to connecting with you at the upcoming meeting of the American Astronomical Society meeting in Grapevine Texas from January 3rd - 7th. Please drop by our booth (which is part of the NSF “Pavilion”) where you can meet and chat with Gemini staff. If you have questions about preparing your 2017A program (phase II) come by and sign up to work with an expert. Also plan to join us for the Gemini Open House to learn more about the exciting ongoing work that makes Gemini the most flexible, innovative, and efficient facility for conducting your research. The Gemini Open House is scheduled for January 4th from 6:30-7:30pm in the Texas 4 Room at the Gaylord Resort in Grapevine, Texas.
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A Symbiotic (Stars) Workshop
In early December a three-day science workshop on the subject of Accretion Processes in Symbiotic Stars and Related Objects brought together several dozen researchers to La Serena Chile. Thanks to the collaboration of our Korean and Chilean partners, as well as the University of La Serena (who hosted the sessions), participants enjoyed many excellent presentations by leaders in the field. While the focus was on symbiotic stars, these star’s relation to cataclysmic variables, X-ray binaries, type Ia supernovae, and planetary nebulae made for diverse and compelling presentations. Ample attention to Gemini’s instrumentation that is relevant to the study of symbiotic stars also populated the agenda. Lively discussions, fresh insights, and new collaborations were born from the meeting which culliminated with a visit to Gemini South. Rodolfo Angeloni and the Local Organizing Committee deserve a special thanks for doing such a fantastic job in organizing the workshop.
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Participants of the Accretion Processes in Symbiotic Stars and Related Objects workshop during the group’s visit to the Gemini South telescope. Photo courtesy Seok-Jun Chang.
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