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Title: THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK

Abstract

Photometry of the unique pre-main-sequence binary system KH 15D is presented, spanning the years 2005-2010. This system has exhibited photometric variations and eclipses over the last {approx}50 years that are attributed to the effect of a precessing circumbinary disk. Advancement of the occulting edge across the projection on the sky of the binary orbit has continued and the photospheres of both stars are now completely obscured at all times. The system has thus transitioned to a state in which it should be visible only by scattered light, and yet it continues to show a periodic variation on the orbital cycle with an amplitude exceeding 2 mag. This variation, which depends only on the binary phase and not on the height of either star above or below the occulting edge, has likely been present in the data since at least 1995. It can, by itself, account for the 'shoulders' on the light curve prior to ingress and following egress, obviating to some degree the need for components of extant models such as a scattering halo around star A or forward scattering from a fuzzy disk edge. However, the spectroscopic evidence for some direct or forward scattered light from star A evenmore » when it was several stellar radii below the occulting edge shows that these components can probably not be fully removed, and raises the possibility that the occulting edge is currently more opaque than it was a decade ago, when the spectra were obtained. A plausible source for the variable scattering component is reflected light from the far side of a warped occulting disk. We have detected color changes in V - I of several tenths of a magnitude to both the blue and red that occur during times of minima. These may indicate the presence of a third source of light (faint star) within the system or a change in the reflectance properties of the disk as the portion being illuminated varies with the orbital motion of the stars. The data support a picture of the circumbinary disk as a geometrically thin, optically thick layer of perhaps millimeter- or centimeter-sized particles that has been sculpted by the binary stars and possibly other components into a decidedly nonplanar configuration. A simple (infinitely sharp) knife-edge model does a good job of accounting for all of the recent (2005-2010) occultation data when one allows for the scattered light component, the spottedness of star A, and variations from cycle to cycle in the location of the edge at the level of 0.1-0.2 stellar diameters.« less

Authors:
;  [1];  [2];  [3];  [4];  [5]
  1. Astronomy Department, Wesleyan University, Middletown, CT 06459 (United States)
  2. Physics and Astronomy Department, Dickinson College, Carlisle, PA 17013 (United States)
  3. Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
  4. Ulugh Bek Astronomical Institute of the Uzbek Academy of Sciences, Astronomicheskaya 33, Tashkent 700052 (Uzbekistan)
  5. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany)
Publication Date:
OSTI Identifier:
21443135
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 140; Journal Issue: 6; Other Information: DOI: 10.1088/0004-6256/140/6/2025; Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; COLOR; ECLIPSE; FUZZY LOGIC; ORBITS; PERIODICITY; PHOTOMETRY; PHOTOSPHERE; PROTOPLANETS; SCATTERING; ATMOSPHERES; MATHEMATICAL LOGIC; OPTICAL PROPERTIES; ORGANOLEPTIC PROPERTIES; PHYSICAL PROPERTIES; SOLAR ATMOSPHERE; STARS; STELLAR ATMOSPHERES; VARIATIONS

Citation Formats

Herbst, William, LeDuc, Katherine, Hamilton, Catrina M, Winn, Joshua N, Ibrahimov, Mansur, Mundt, Reinhard, and Johns-Krull, Christopher M., E-mail: wherbst@wesleyan.ed. THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK. United States: N. p., 2010. Web. doi:10.1088/0004-6256/140/6/2025.
Herbst, William, LeDuc, Katherine, Hamilton, Catrina M, Winn, Joshua N, Ibrahimov, Mansur, Mundt, Reinhard, & Johns-Krull, Christopher M., E-mail: wherbst@wesleyan.ed. THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK. United States. https://doi.org/10.1088/0004-6256/140/6/2025
Herbst, William, LeDuc, Katherine, Hamilton, Catrina M, Winn, Joshua N, Ibrahimov, Mansur, Mundt, Reinhard, and Johns-Krull, Christopher M., E-mail: wherbst@wesleyan.ed. 2010. "THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK". United States. https://doi.org/10.1088/0004-6256/140/6/2025.
@article{osti_21443135,
title = {THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK},
author = {Herbst, William and LeDuc, Katherine and Hamilton, Catrina M and Winn, Joshua N and Ibrahimov, Mansur and Mundt, Reinhard and Johns-Krull, Christopher M., E-mail: wherbst@wesleyan.ed},
abstractNote = {Photometry of the unique pre-main-sequence binary system KH 15D is presented, spanning the years 2005-2010. This system has exhibited photometric variations and eclipses over the last {approx}50 years that are attributed to the effect of a precessing circumbinary disk. Advancement of the occulting edge across the projection on the sky of the binary orbit has continued and the photospheres of both stars are now completely obscured at all times. The system has thus transitioned to a state in which it should be visible only by scattered light, and yet it continues to show a periodic variation on the orbital cycle with an amplitude exceeding 2 mag. This variation, which depends only on the binary phase and not on the height of either star above or below the occulting edge, has likely been present in the data since at least 1995. It can, by itself, account for the 'shoulders' on the light curve prior to ingress and following egress, obviating to some degree the need for components of extant models such as a scattering halo around star A or forward scattering from a fuzzy disk edge. However, the spectroscopic evidence for some direct or forward scattered light from star A even when it was several stellar radii below the occulting edge shows that these components can probably not be fully removed, and raises the possibility that the occulting edge is currently more opaque than it was a decade ago, when the spectra were obtained. A plausible source for the variable scattering component is reflected light from the far side of a warped occulting disk. We have detected color changes in V - I of several tenths of a magnitude to both the blue and red that occur during times of minima. These may indicate the presence of a third source of light (faint star) within the system or a change in the reflectance properties of the disk as the portion being illuminated varies with the orbital motion of the stars. The data support a picture of the circumbinary disk as a geometrically thin, optically thick layer of perhaps millimeter- or centimeter-sized particles that has been sculpted by the binary stars and possibly other components into a decidedly nonplanar configuration. A simple (infinitely sharp) knife-edge model does a good job of accounting for all of the recent (2005-2010) occultation data when one allows for the scattered light component, the spottedness of star A, and variations from cycle to cycle in the location of the edge at the level of 0.1-0.2 stellar diameters.},
doi = {10.1088/0004-6256/140/6/2025},
url = {https://www.osti.gov/biblio/21443135}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 6,
volume = 140,
place = {United States},
year = {Wed Dec 15 00:00:00 EST 2010},
month = {Wed Dec 15 00:00:00 EST 2010}
}