Showing papers by "Michael E. Brown published in 2000"
TL;DR: This new component, Gl 570D, was initially identified from the Two Micron All-Sky Survey and shows the 1.6 and 2.2 µm CH4 absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship.
Abstract: We report the discovery of a widely separated (258$\farcs3\pm0\farcs$4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All Sky Survey (2MASS). Its near-infrared spectrum shows the 1.6 and 2.2 $\micron$ CH$_4$ absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (M$_J$ = 16.47$\pm$0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8$\pm$0.3)x10$^{-6}$ L$_{\sun}$ and T$_{eff}$ = 750$\pm$50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50$\pm$20 M$_{Jup}$ for this object.
239 citations
TL;DR: In this article, the authors reported the discovery of a widely separated (258".3 ± 0".4) T dwarf companion to the Gl 570ABC system from the Two Micron All-Sky Survey.
Abstract: We report the discovery of a widely separated (258".3 ± 0".4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All-Sky Survey. Its near-infrared spectrum shows the 1.6 and 2.2 μm CH_4 absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (M_J = 16.47 ± 0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8 ± 0.3) × 10^(-6) L_☉ and T_(eff) = 750 ± 50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50 ± 20 M_(Jup) for this object.
237 citations
TL;DR: Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers, found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite.
Abstract: Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon's spectrum suggests the presence of ammonia ices. Ammonia ice–water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite's past.
186 citations
01 Jan 2000
TL;DR: The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite, and absorption features in Charon's spectrum suggest the presence of ammonia ices.
Abstract: Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon’s spectrum suggests the presence of ammonia ices. Ammonia ice—water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite’s past. Pluto’s satellite Charon orbits Pluto so closely that, even though it is only five times fainter than Pluto, Charon’s existence was not discovered until 1978 (1). Even after discovery, the small separation between the two objects has made separate study of them difficult. Most of our current knowledge about the composition of Charon comes from observations of a series of mutual PlutoCharon eclipses between 1985 and 1990. In two such series of eclipses, Pluto and Charon were observed together, and then Pluto was observed separately as it completely occulted Charon. Subtraction of the two observations
160 citations
TL;DR: In this paper, the authors reported the discovery of a bright (J = 13.83 ± 0.03) methane brown dwarf, or T dwarf, by the Two Micron All Sky Survey (2MASSI J0559191-140448).
Abstract: We report the discovery of a bright (J = 13.83 ± 0.03) methane brown dwarf, or T dwarf, by the Two Micron All Sky Survey. This object, 2MASSI J0559191-140448, is the first brown dwarf identified by the newly commissioned CorMASS instrument mounted on the Palomar 60 inch (1.5 m) telescope. Near-infrared spectra from 0.9 to 2.35 μm show characteristic CH_4 bands at 1.1, 1.3, 1.6, and 2.2 μm, which are significantly shallower than those seen in other T dwarfs discovered to date. Coupled with the detection of an FeH band at 0.9896 μm and two sets of K I doublets at J band, we propose that 2MASS J0559-14 is a warm T dwarf, close to the transition between L and T spectral classes. The brightness of this object makes it a good candidate for detailed investigation over a broad wavelength regime and at higher resolution.
113 citations
TL;DR: In this article, the authors obtained near-infrared spectra of the four brightest known Centaurs and of five irregular satellites of giant planets, including 1997 CU_(26), Pholus, Phoebe (S9), and Nereid (N2).
Abstract: We have obtained near-infrared spectra of the four brightest known Centaurs and of five irregular satellites of giant planets. Many of these objects show 1.5 and 2.0 μm absorption bands indicative of water ice, including 1997 CU_(26), Pholus, Phoebe (S9), and Nereid (N2). The satellites of Jupiter—Elara, Himalia, and Pasaphae (J6, J7, J8)—appear spectrally featureless, consistent with asteroidal origins for these bodies. Phoebe's surface water ice indicates that it formed as an icy planetesimal rather than as an asteroid.
94 citations
TL;DR: The detection of Hα emission in the T dwarf 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph was reported in this article.
Abstract: We report the detection of Hα emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log (L_(Hα)/L_(bol)) = -4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs. We speculate on several mechanisms that may be responsible for emission, including a strong magnetic field, continuous flaring, acoustic heat generation, and a close [α ~ (4–20)R_J] interacting binary, with the cooler component overflowing its Roche lobe. We suggest that the M9.5 Ve PC 0025+0447 could be a warm analog to 2MASS J1237+65 and may be powered by the latter mechanism.
88 citations
TL;DR: In this paper, the authors reported the detection of H{$\alpha$} emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph.
Abstract: We report the detection of H{$\alpha$} emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log(L$_{H{\alpha}}$/L$_{bol}$) = $-$4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs. We speculate on several mechanisms that may be responsible for emission, including a strong magnetic field, continuous flaring, acoustic heat generation, and a close ($a$ $\sim$ 4 - 20 R$_{Jup}$) interacting binary, with the cooler component overflowing its Roche lobe. We suggest that the M9.5Ve PC 0025+0447 could be a warm analogue to 2MASS J1237+65, and may be powered by the latter mechanism.
76 citations
TL;DR: In this paper, the authors obtained a near-infrared spectrum of the bright Kuiper Belt object 2000 EB173, which appears featureless and has a sufficient signal-to-noise ratio to rule out the 1.5 and 2.0 μm absorption from water ice even at the low level seen in the Centaur Chariklo.
Abstract: We have obtained a near-infrared spectrum of the bright Kuiper Belt object 2000 EB173; the spectrum appears featureless. The spectrum has a sufficient signal-to-noise ratio to rule out the 1.5 and 2.0 μm absorption from water ice even at the low level seen in the Centaur Chariklo. In addition, we can rule out a 2.3 μm absorption at the level seen in the Centaur Pholus.
33 citations
TL;DR: The trailing hemispheres of Europa and Callisto were observed at 9-13 μm and a spectrum of Europa with better spectral resolution and a better signal-to-noise ratio than was previously possible has been derived.
Abstract: The trailing hemispheres of Europa and Callisto were observed at 9–13 μm, and a spectrum of Europa with better spectral resolution and a better signal-to-noise ratio than was previously possible has been derived. The ratio spectrum of the two satellites has a signal-to-noise ratio of approximately 30 for a spectral resolving power of approximately 50. The disk-integrated, effective color temperature ratio for the two satellites is consistent with broadband, thermal infrared photometry from previous ground-based studies and from the Galileo photopolarimeter radiometer. The ratio spectrum was combined with the average Voyager 1 spectrum of Callisto to obtain a 9–13 μm spectrum of Europa with a signal-to-noise ratio that is a factor of 10 better than that in the average Voyager spectrum of Europa. After convolving the measured spectrum to the expected width of water ice emissivity features, ∼1 μm, no spectral features that could be attributed to water ice on the surface of Europa are apparent at the 0.6–0.7% level. The absence of spectral features attributable to water ice is consistent with the proposal that the equatorial region of Europa that was observed may be composed primarily of a heavily hydrated mineral. The absence of water ice features may also be the result of a large fractional abundance of fine particles, such as that found on the surface of the Moon.
24 citations
TL;DR: In this paper, the authors compared the COBE DIRBE images to a model Mars wake based on the empirical model of Earth's wake as seen by the DIRTBE and place a 3-σ upper limit on the fractional overdensity of particles in the Mars wake of 18% of the fraction of overdensity trailing Earth.
TL;DR: Geissler et al. as mentioned in this paper concluded that Io's diffuse red emissions imaged by the Galileo Solid State Imager are due to impact or dissociative excitation of oxygen, while diffuse green emissions are caused by the impact of sodium.
Journal Article•
TL;DR: In this article, the detection of H alpha emission in the T dwarf (methane brown dwarf) 2MASSW J1237392 + 652615 over three days using the Keek Low esolution Imaging Spectrograph.
Abstract: We report the detection of H alpha emission in the T dwarf (methane brown dwarf) 2MASSW J1237392 + 652615 over three days using the Keek Low esolution Imaging Spectrograph. The measured line flux, log (L-H alpha/L-bol) = -4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs.
TL;DR: In this paper, the NICMOS coronagraph on the Hubble Space Telescope was used to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars.
Abstract: We observed Sirius, Altair, and Procyon with the NICMOS coronagraph on the Hubble Space Telescope to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars. We did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exozodiacal dust in these systems, but we did set strong upper limits on the presence of nearby late‐type and substellar companions.
TL;DR: In this article, the authors used the Keck telescope to image six nearby main-sequence stars at 11.6 microns, correcting for atmosphere-induced wavefront aberrations and deconvolving the point spread function via classical speckle analysis.
Abstract: We have begun an observational program to search nearby stars for dust disks that are analogous to the disk of zodiacal dust that fills the interior of our solar system. We imaged six nearby main-sequence stars with the Keck telescope at 11.6 microns, correcting for atmosphere-induced wavefront aberrations and deconvolving the point spread function via classical speckle analysis. We compare our data to a simple model of the zodiacal dust in our own system based on COBE/DIRBE observations and place upper limits on the density of exozodiacal dust in these systems.
TL;DR: The first year of shared-risk observations, the PALAO/PHARO adaptive optics system has been employed to obtain near-infrared R approximately 1000 spectra of solar system targets at spectroscopic slit widths of 0.5 and 0.1 arcsec, and corresponding spatial resolution along the slit as fine as 0.08 arcsec as discussed by the authors.
Abstract: During its first year of shared-risk observations, the PALAO/PHARO adaptive optics system has been employed to obtain near-infrared R approximately 1000 spectra of solar system targets at spectroscopic slit widths of 0.5 and 0.1 arcsec, and corresponding spatial resolution along the slit as fine as 0.08 arcsec. Phenomena undergoing initial investigation include condensate formation in the atmospheres of Neptune, and the Saturnian moon, Titan. We present the results of this AO spectroscopy campaign and discuss AO specific considerations in the reduction and interpretation of this data.
TL;DR: In this article, the NICMOS coronagraph was used to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars, but they did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exo-zodiacal Dust in these systems, but did set strong upper limits on the presence of nearby late-type and sub-stellar companions.
Abstract: We observed Sirius, Altair, and Procyon with the NICMOS Coronagraph on the Hubble Space Telescope to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars. We did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exo-zodiacal dust in these systems, but we did set strong upper limits on the presence of nearby late-type and sub-stellar companions.