Jacqueline Radigan

Publications (7)11.55 Total impact

• Article: Weather on Other Worlds. I. Detection of Periodic Variability in the L3 Dwarf DENIS-P J1058.7-1548 with Precise Multi-wavelength Photometry

  Aren N. Heinze, Stanimir Metchev, Daniel Apai, Davin Flateau, Radostin Kurtev, Mark Marley, Jacqueline Radigan, Adam J. Burgasser, Étienne Artigau, Peter Plavchan
  [show abstract] [hide abstract]
  ABSTRACT: Photometric monitoring from warm Spitzer reveals that the L3 dwarf DENIS-P J1058.7-1548 varies sinusoidally in brightness with a period of 4.25^{+0.26}_{-0.16} hr and an amplitude of 0.388% ± 0.043% (peak-to-valley) in the 3.6 μm band, confirming the reality of a 4.31 ± 0.31 hr periodicity detected in J-band photometry from the SOAR telescope. The J-band variations are a factor of 2.17 ± 0.35 larger in amplitude than those at 3.6 μm, while 4.5 μm Spitzer observations yield a 4.5 μm/3.6 μm amplitude ratio of only 0.23 ± 0.15, consistent with zero 4.5 μm variability. This wide range in amplitudes indicates rotationally modulated variability due to magnetic phenomena and/or inhomogeneous cloud cover. Weak Hα emission indicates some magnetic activity, but it is difficult to explain the observed amplitudes by magnetic phenomena unless they are combined with cloud inhomogeneities (which might have a magnetic cause). However, inhomogeneous cloud cover alone can explain all our observations, and our data align with theory in requiring that the regions with the thickest clouds also have the lowest effective temperature. Combined with published vsin (i) results, our rotation period yields a 95% confidence lower limit of R * >= 0.111 R sun, suggesting upper limits of 320 Myr and 0.055 M sun on the age and mass. These limits should be regarded cautiously because of ~3σ inconsistencies with other data; however, a lower limit of 45° on the inclination is more secure. DENIS-P J1058.7-1548 is only the first of nearly two dozen low-amplitude variables discovered and analyzed by the Weather on Other Worlds project.
  The Astrophysical Journal 04/2013; 767(2):173. · 6.02 Impact Factor
• Article: Discovery of Two Very Wide Binaries with Ultracool Companions and a New Brown Dwarf at the L/T Transition

  Koraljka Muzic, Jacqueline Radigan, Ray Jayawardhana, Valentin D. Ivanov, Jacqueline K. Faherty, Radostin G. Kurtev, Alejandro Nunez, Henri M. J. Boffin, Olivier Hainaut, Kelle Cruz, David Jones, Stanimir Metchev, Amy Tyndall, Jura Borissova
  [show abstract] [hide abstract]
  ABSTRACT: We present the discovery and spectroscopic follow-up of a nearby late-type L dwarf (2M0614+3950), and two extremely wide very-low-mass binary systems (2M0525-7425AB and 2M1348-1344AB), resulting from our search for common proper motion pairs containing ultracool components in the Two Micron All Sky Survey (2MASS) and the Wide-field Infrared Survey Explorer (WISE) catalogs. The near-infrared spectrum of 2M0614+3950 indicates a spectral type L$9 \pm 1$ object residing at a distance of $26.0 \pm 1.8$ pc. The optical spectrum of 2M0525-7425A reveals an M$3.0 \pm 0.5$ dwarf primary, accompanied by a secondary previously classified as L2. The system has an angular separation of $\sim 44"$, equivalent to $\sim 2000 $AU at distance of $46.0 \pm 3.0$ pc. Using optical and infrared spectra, respectively, we classify the components of 2M1348-1344AB as M$4.5 \pm 0.5$ and T$5.5 \pm 1$. The angular separation of $\sim 68"$ is equivalent to $\sim 1400 $AU at a distance of $20.7 \pm 1.4$ pc. 2M1348-1344AB is one of only six very wide (separation $>$ 1000 AU) systems containing late T dwarfs known to date.
  05/2012;
• Source

  Available from: ArXiv

  Article: Large Amplitude Variations of an L/T Transition Brown Dwarf: Multi-Wavelength Observations of Patchy, High-Contrast Cloud Features

  Jacqueline Radigan, Ray Jayawardhana, David Lafrenière, Etienne Artigau, Mark Marley, Didier Saumon
  [show abstract] [hide abstract]
  ABSTRACT: We present multiple-epoch photometric monitoring in the $J$, $H$, and $K_s$ bands of the T1.5 dwarf 2MASS J21392676+0220226 (2M2139), revealing persistent, periodic ($P=7.721\pm$0.005 hr) variability with a peak-to-peak amplitude as high as 26% in the $J$-band. The light curve shape varies on a timescale of days, suggesting that evolving atmospheric cloud features are responsible. Using interpolations between model atmospheres with differing cloud thicknesses to represent a heterogeneous surface, we find that the multi-wavelength variations and the near-infrared spectrum of 2M2139 can be reproduced by either (1)cool, thick cloud features sitting above a thinner cloud layer, or (2)warm regions of low condensate opacity in an otherwise cloudy atmosphere, possibly indicating the presence of holes or breaks in the cloud layer. We find that temperature contrasts between thick and thin cloud patches must be greater than 175 K and as high as 425 K. We also consider whether the observed variability could arise from an interacting binary system, but this scenario is ruled out. 2M2139 joins the T2.5 dwarf SIMP0136 discovered by Artigau and coworkers as the second L/T transition brown dwarf to display large-amplitude variability on rotational timescales, suggesting that the fragmentation of dust clouds at the L/T transition may contribute to the abrupt decline in condensate opacity and $J$-band brightening observed to occur over this regime.
  01/2012;
• Article: DENIS J081730.0–615520: An Overlooked Mid-T Dwarf in the Solar Neighborhood

  Étienne Artigau, Jacqueline Radigan, Stuart Folkes, Ray Jayawardhana, Radostin Kurtev, David Lafrenière, René Doyon, and Jura Borissova
  [show abstract] [hide abstract]
  ABSTRACT: Recent wide-field near-infrared surveys have uncovered a large number of cool brown dwarfs (BDs), extending the temperature sequence down to less than 500 K and constraining the faint end of the luminosity function (LF). One interesting implication of the derived LF is that the BD census in the immediate (<10 pc) solar neighborhood is still largely incomplete, and some bright (J < 16) BDs remain to be identified in existing surveys. These objects are especially interesting as they are the ones that can be studied in most detail, especially with techniques that require large fluxes (e.g., time-variability, polarimetry, and high-resolution spectroscopy) that cannot realistically be applied to objects uncovered by deep surveys. By cross-matching the DEep Near-Infrared Survey of the Southern sky (DENIS) and the Two Micron All Sky Survey point-source catalogs, we have identified an overlooked BD—DENIS J081730.0–615520—that is the brightest field mid-T dwarf in the sky (J = 13.6). We present astrometry and spectroscopy follow-up observations of this BD. Our data indicate a spectral type T6 and a distance—from parallax measurement—of 4.9 ± 0.3 pc, placing this mid-T dwarf among the three closest isolated BDs to the Sun.
  The Astrophysical Journal Letters 06/2010; 718(1):L38. · 5.53 Impact Factor
• Source

  Available from: Radostin Georgiev Kurtev

  Article: DENIS J081730.0-615520: An overlooked mid-T dwarf in the solar neighborhood

  Étienne Artigau, Jacqueline Radigan, Stuart Folkes, Ray Jayawardhana, Radostin Kurtev, David Lafrenière, René Doyon, Jura Borissova
  [show abstract] [hide abstract]
  ABSTRACT: Recent wide-field near-infrared surveys have uncovered a large number of cool brown dwarfs, extending the temperature sequence down to less than 500 K and constraining the faint end of the luminosity function. One interesting implication of the derived luminosity function is that the brown dwarf census in the immediate (<10 pc) solar neighborhood is still largely incomplete, and some bright (J<16) brown dwarfs remain to be identified in existing surveys. These objects are especially interesting as they are the ones that can be studied in most detail, especially with techniques that require large fluxes (e.g. time-variability, polarimetry, high-resolution spectroscopy) that cannot realistically be applied to objects uncovered by deep surveys. By cross-matching the DENIS and the 2MASS point-source catalogs, we have identified an overlooked brown dwarf -DENIS J081730.0-615520- that is the brightest field mid-T dwarf in the sky (J = 13.6). We present astrometry and spectroscopy follow-up observations of this brown dwarf. Our data indicate a spectral type T6 and a distance -from parallax measurement- of 4.9\pm0.3 pc, placing this mid-T dwarf among the 3 closest isolated brown dwarfs to the Sun. Comment: accepted for publication in ApJL, 3 figures
  06/2010;
• Source

  Available from: ArXiv

  Article: Discovery of the Widest Very Low Mass Field Binary

  Jacqueline Radigan, David Lafrenière, Ray Jayawardhana, René Doyon
  [show abstract] [hide abstract]
  ABSTRACT: We present the discovery of the widest (~6700 AU) very low mass field binary to date, found in a proper motion cross-match of the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Our follow-up J-band imaging provides a 10-year baseline for measuring proper motions. Consequently, we are able to confirm the common proper motion of the pair to within 10 mas, implying a 99.5% probability of their physical association. Near infrared spectra of the components indicate spectral types of M6+/-1 and M7+/-1. The system resides at a spectroscopic distance of 105+/-13 pc and has an angular separation of 63.38+/-0.05 arcsec. We have used evolutionary models to infer component masses of 0.105^{+0.029}_{-0.017} M_sun and 0.091^{+0.010}_{-0.007} Msun. The large separation and low binding energy of this system can provide constraints for formation models of very low mass stars.
  03/2009;
• Source

  Available from: ArXiv

  Article: Discovery of a Wide Substellar Companion to a Nearby Low-Mass Star

  Jacqueline Radigan, David Lafrenière, Ray Jayawardhana, René Doyon
  [show abstract] [hide abstract]
  ABSTRACT: We report the discovery of a wide (135+/-25 AU), unusually blue L5 companion 2MASS J17114559+4028578 to the nearby M4.5 dwarf G 203-50 as a result of a targeted search for common proper motion pairs in the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Adaptive Optics imaging with Subaru indicates that neither component is a nearly equal mass binary with separation > 0.18", and places limits on the existence of additional faint companions. An examination of TiO and CaH features in the primary's spectrum is consistent with solar metallicity and provides no evidence that G 203-50 is metal poor. We estimate an age for the primary of 1-5 Gyr based on activity. Assuming coevality of the companion, its age, gravity and metallicity can be constrained from properties of the primary, making it a suitable benchmark object for the calibration of evolutionary models and for determining the atmospheric properties of peculiar blue L dwarfs. The low total mass (M_tot=0.21+/-0.03 M_sun), intermediate mass ratio (q=0.45+/-0.14), and wide separation of this system demonstrate that the star formation process is capable of forming wide, weakly bound binary systems with low mass and BD components. Based on the sensitivity of our search we find that no more than 2.2% of early-to-mid M dwarfs (9.0 < M_V < 13.0) have wide substellar companions with m > 0.06 M_sun. Comment: 24 pages, 5 figures, accepted for publication in ApJ
  08/2008;