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Articles 31 - 60 of 113

Full-Text Articles in Physical Sciences and Mathematics

Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein Jan 2013

Conformal Gravity And The Alcubierre Warp Drive Metric, Gabriele U. Varieschi, Zily Burstein

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We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, that is, effective superluminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity …

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Self-Completeness And The Generalized Uncertainty Principle, Maximiliano Isi, Jonas Mureika, Piero Nicolini Jan 2013

Self-Completeness And The Generalized Uncertainty Principle, Maximiliano Isi, Jonas Mureika, Piero Nicolini

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The generalized uncertainty principle discloses a self-complete characteristic of gravity, namely the possibility of masking any curvature singularity behind an event horizon as a result of matter compression at the Planck scale. In this paper we extend the above reasoning in order to overcome some current limitations to the framework, including the absence of a consistent metric describing such Planck-scale black holes. We implement a minimum-size black hole in terms of the extremal configuration of a neutral non-rotating metric, which we derived by mimicking the effects of the generalized uncertainty principle via a short scale modified version of Einstein gravity. …

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Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika Sep 2012

Primordial Black Hole Evaporation And Spontaneous Dimensional Reduction, Jonas R. Mureika

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Several different approaches to quantum gravity suggest the effective dimension of spacetime reduces from four to two near the Planck scale. In light of such evidence, this Letter re-examines the thermodynamics of primordial black holes (PBHs) in specific lower-dimensional gravitational models. Unlike in four dimensions, (1 + 1)-D black holes radiate with power P ∼ M2BH, while it is known no (2+1)-D (BTZ) black holes can exist in a non-anti-de Sitter universe. This has important relevance to the PBH population size and distribution, and consequently on cosmological evolution scenarios. The number of PBHs that have evaporated to …

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A Proper Motion Study Of The Haro 6-10 Outflow: Evidence For A Subarcsecond Binary, Bruce Wilking, Kevin Marvel, Mark Claussen, Bradley Gerling, Alwyn Wootten, Erika Gibb Jul 2012

A Proper Motion Study Of The Haro 6-10 Outflow: Evidence For A Subarcsecond Binary, Bruce Wilking, Kevin Marvel, Mark Claussen, Bradley Gerling, Alwyn Wootten, Erika Gibb

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We present single-dish and very long baseline interferometry observations of an outburst of water maser emission from the young binary system Haro 6-10. Haro 6-10 lies in the Taurus molecular cloud and contains a visible T Tauri star with an infrared companion 1farcs3 north. Using the Very Long Baseline Array, we obtained five observations spanning three months and derived absolute positions for 20 distinct maser spots. Three of the masers can be traced over three or more epochs, enabling us to extract absolute proper motions and tangential velocities. We deduce that the masers represent one side of a bipolar outflow …

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The Gas/Dust Ratio Of Circumstellar Disks: Testing Models Of Planetesimal Formation, David Horne, Erika Gibb, Terrence Rettig, Sean Brittain, David Tilley, Dinshaw Balsara Jul 2012

The Gas/Dust Ratio Of Circumstellar Disks: Testing Models Of Planetesimal Formation, David Horne, Erika Gibb, Terrence Rettig, Sean Brittain, David Tilley, Dinshaw Balsara

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We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. 12CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig et al.

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Noncontact Ultrasound Imaging Applied To Cortical Bone Phantoms, John Bulman, K. S. Ganezer, P. W. Halcrow, Ian Neeson Jun 2012

Noncontact Ultrasound Imaging Applied To Cortical Bone Phantoms, John Bulman, K. S. Ganezer, P. W. Halcrow, Ian Neeson

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Purpose: The purpose of this paper was to take the first steps toward applying noncontact ultrasound (NCU) to the tasks of monitoring osteoporosis and quantitative ultrasound imaging (QUS) of cortical bone. The authors also focused on the advantages of NCU, such as its lack of reliance on a technologist to apply transducers and a layer of acoustical coupling gel, the ability of the transducers to operate autonomously as specified by preprogrammed software, and the likely reduction in statistical and systematic errors associated with the variability in the pressure applied by the clinician to the transmitting transducer that NCU might provide. …

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Simulating A Guitar With A Conventional Sonometer, Zily Burstein, Christina M. Gower, Gabriele U. Varieschi Jun 2012

Simulating A Guitar With A Conventional Sonometer, Zily Burstein, Christina M. Gower, Gabriele U. Varieschi

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In this paper we present a simple way to convert a conventional sonometer into a simulated fretted instrument, such as a guitar or similar, by adding a fingerboard to the sonometer. In particular, we use this modified apparatus in relation to the problem of the instrument intonation, i.e., how to obtain correctly tuned notes on these string instruments. The experimental procedures presented in this study can become a more structured laboratory activity to be used in general physics courses or acoustics classes.

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Chemical Composition Of Comet C/2007 N3 (Lulin): Another ''Atypical'' Comet, Erika Gibb, Boncho Bonev, Geronimo Villanueva, Michael Disanti, Michael Mumma, Emily Sudholt, Yana Radeva May 2012

Chemical Composition Of Comet C/2007 N3 (Lulin): Another ''Atypical'' Comet, Erika Gibb, Boncho Bonev, Geronimo Villanueva, Michael Disanti, Michael Mumma, Emily Sudholt, Yana Radeva

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We measured the volatile chemical composition of comet C/2007 N3 (Lulin) on three dates from 2009 January 30 to February 1 using NIRSPEC, the high-resolution (λ/Δλ ≈ 25,000), long-slit echelle spectrograph at Keck 2. We sampled nine primary (parent) volatile species (H2O, C2H6, CH3OH, H2CO, CH4, HCN, C2H2, NH3, CO) and two product species (OH* and NH2). We also report upper limits for HDO and CH3D. C/2007 N3 (Lulin) displayed an unusual composition when compared to other comets. Based on comets measured to date, CH4 and C2H6 exhibited "normal" abundances relative to water, CO and HCN were only moderately depleted, …

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Could Any Black Holes Be Produced At The Lhc?, Jonas R. Mureika, Piero Nicolini, Euro Spallucci Apr 2012

Could Any Black Holes Be Produced At The Lhc?, Jonas R. Mureika, Piero Nicolini, Euro Spallucci

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We introduce analytical quantum gravity modifications of the production cross section for terascale black holes by employing an effective ultraviolet cut off l. We find the new cross sections approach the usual "black disk" form at high energy, while they differ significantly near the fundamental scale from the standard increase with respect to s. We show that the heretofore discontinuous step function used to represent the cross section threshold can realistically be modeled by two functions representing the incoming and final parton states in a high energy collision. The growth of the cross section with collision energy is …

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Conformal Cosmology And The Pioneer Anomaly, Gabriele U. Varieschi Jan 2012

Conformal Cosmology And The Pioneer Anomaly, Gabriele U. Varieschi

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No abstract provided.

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Constraints On Vector Unparticle Physics From Cosmic Censorship, Jonas R. Mureika Oct 2011

Constraints On Vector Unparticle Physics From Cosmic Censorship, Jonas R. Mureika

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Vector unparticle couplings to standard model fields produce repulsive corrections to gravity. From a general relativistic perspective, this leads to an effective Reissner-Nordstrom-like metric whose "charge" is a function of the unparticle coupling constant λ, and therefore can admit naked singularities. Requiring the system to respect cosmic censorship provides a new method of constraining the value of λ. These limits are extremely loose for stellar-mass black holes, but commensurate with existing bounds for primordial black holes. In the case of theoretical low-mass black holes, the bounds on λ are much stricter than those derived from astrophysical and accelerator …

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The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson Sep 2011

The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson

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We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 deg2 of the ρ Ophiuchi star-forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased toward particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function. We have obtained over 300 optical spectra to help identify 135 association members based on the presence of Hα in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or …

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(1+1)-Dimensional Entropic Gravity, R. B. Mann, Jonas R. Mureika Sep 2011

(1+1)-Dimensional Entropic Gravity, R. B. Mann, Jonas R. Mureika

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We consider the formulation of entropic gravity in two spacetime dimensions. The usual gravitational force law is derived even in the absence of area, as normally required by the holographic principle. A special feature of this perspective concerns the nature of temperature and entropy defined at a point. We argue that the constancy of the gravitational force in one spatial dimension implies the information contained at each point in space is an internal degree of freedom on the manifold, and furthermore is a universal constant, contrary to previous assertions that entropic gravity in one spatial dimension is ill-defined. We give …

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Aspects Of Noncommutative (1+1)-Dimensional Black Holes, Jonas R. Mureika, Piero Nicolini Aug 2011

Aspects Of Noncommutative (1+1)-Dimensional Black Holes, Jonas R. Mureika, Piero Nicolini

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We present a comprehensive analysis of the spacetime structure and thermodynamics of ( 1 + 1 )-dimensional black holes in a noncommutative framework. It is shown that a wider variety of solutions are possible than the commutative case considered previously in the literature. As expected, the introduction of a minimal length √ θ cures singularity pathologies that plague the standard two-dimensional general relativistic case, where the latter solution is recovered at large length scales. Depending on the choice of input parameters (black hole mass M, cosmological constant Λ , etc.), black hole solutions with zero, up to six, horizons …

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Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer Jun 2011

Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer

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We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet 103P/Hartley 2 using high-dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, …

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Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy, Jonas R. Mureika, Dejan Stojkovic Mar 2011

Detecting Vanishing Dimensions Via Primordial Gravitational Wave Astronomy, Jonas R. Mureika, Dejan Stojkovic

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Lower dimensionality at higher energies has manifold theoretical advantages as recently pointed out by Anchordoqui et al. [arXiv:1003.5914]. Moreover, it appears that experimental evidence may already exist for it: A statistically significant planar alignment of events with energies higher than TeV has been observed in some earlier cosmic ray experiments. We propose a robust and independent test for this new paradigm. Since ( 2 + 1 )-dimensional spacetimes have no gravitational degrees of freedom, gravity waves cannot be produced in that epoch. This places a universal maximum frequency at which primordial waves can propagate, marked by the transition between dimensions. …

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Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu Jan 2011

Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu

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Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope …

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Kinematical Conformal Cosmology: Fundamental Parameters From Astrophysical Observations, Gabriele U. Varieschi Jan 2011

Kinematical Conformal Cosmology: Fundamental Parameters From Astrophysical Observations, Gabriele U. Varieschi

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No abstract provided.

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Does Entropic Gravity Bound The Masses Of The Photon And Graviton?, Jonas R. Mureika, R. B. Mann Dec 2010

Does Entropic Gravity Bound The Masses Of The Photon And Graviton?, Jonas R. Mureika, R. B. Mann

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If the information transfer between test particle and holographic screen in entropic gravity respects both the uncertainty principle and causality, a lower limit on the number of bits in the universe relative to its mass may be derived. Furthermore, these limits indicate particles that putatively travel at the speed of light -- the photon and/or graviton -- have a non-zero mass m≥10−68 kg. This result is found to be in excellent agreement with current experimental mass bounds on the graviton and photon, suggesting that entropic gravity may be the result of a (recent) softly-broken local symmetry. Stronger bounds emerge …

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Vector Unparticle Enhanced Black Holes: Exact Solutions And Thermodynamics, Jonas R. Mureika, Euro Spallucci Sep 2010

Vector Unparticle Enhanced Black Holes: Exact Solutions And Thermodynamics, Jonas R. Mureika, Euro Spallucci

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Tensor and scalar unparticle couplings to matter have been shown to enhance gravitational interactions and provide corrections to the Schwarzschild metric and associated black hole structure. We derive an exact solution to the Einstein equations for vector unparticles, and conclusively demonstrate that these induce Riessner–Nordström (RN)-like solutions where the role of the “charge” is defined by a composite of unparticle phase space parameters. These black holes admit double-horizon structure, although unlike the RN metric these solutions have a minimum inner horizon value. In the extremal limit, the Hawking temperature is shown to vanish. As with the scalar/tensor case, the (outer) …

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Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar Aug 2010

Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar

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The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result …

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Co And H3 + Toward Mwc 1080, Mwc 349, And Lkhα 101, Erika Gibb, S. Brittain, T Rettig, M Troutman, Theodore Simon, C Kulesa May 2010

Co And H3 + Toward Mwc 1080, Mwc 349, And Lkhα 101, Erika Gibb, S. Brittain, T Rettig, M Troutman, Theodore Simon, C Kulesa

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We present high-resolution, near-infrared NIRSPEC observations of the fundamental rovibrational CO and H+ 3 R(1,0), R(1,1) u , and Q(1,0) transitions toward three early-type young stars: MWC 1080, MWC 349, and LkHα 101. These observations were performed for the purpose of constraining the physical characteristics of the interstellar material along each line of sight. Toward MWC 1080, we detected strong CO absorption and determined a column density upper limit of 1.4 × 1014 cm–2 for H+ 3. We infer that there is very little diffuse material along the line of sight toward MWC 1080 and that the CO absorption is …

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A Kinematical Approach To Conformal Cosmology, Gabriele U. Varieschi Apr 2010

A Kinematical Approach To Conformal Cosmology, Gabriele U. Varieschi

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We present an alternative cosmology based on conformal gravity, as originally introduced by H. Weyl and recently revisited by P. Mannheim and D. Kazanas. Unlike past similar attempts our approach is a purely kinematical application of the conformal symmetry to the Universe, through a critical reanalysis of fundamental astrophysical observations, such as the cosmological redshift and others. As a result of this novel approach we obtain a closed-form expression for the cosmic scale factor R(t) and a revised interpretation of the space-time coordinates usually employed in cosmology. New fundamental cosmological parameters are introduced and evaluated. This emerging new cosmology does …

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Intonation And Compensation Of Fretted String Instruments, Gabriele U. Varieschi, Christina M. Gower Jan 2010

Intonation And Compensation Of Fretted String Instruments, Gabriele U. Varieschi, Christina M. Gower

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We discuss theoretical and physical models that are useful for analyzing the intonation of musical instruments such as guitars and mandolins and can be used to improve the tuning on these instruments. The placement of frets on the fingerboard is designed according to mathematical rules and the assumption of an ideal string. The analysis becomes more complicated when we include the effects of deformation of the string and inharmonicity due to other string characteristics. As a consequence, perfect intonation of all the notes on the instrument cannot be achieved, but complex compensation procedures can be introduced to minimize the problem. …

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Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis Jul 2009

Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis

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High-dispersion (λ/δλ ≈ 25,000) infrared spectra of Comet C/2004 Q2 (Machholz) were acquired on 2004 November 28-29, and 2005 January 19 (UT dates) with the Near InfraRed echelle SPECtrograph (NIRSPEC) at the Keck-2 telescope on Mauna Kea. We detected H2O, CH4, C2H2, C2H6, CO, H2CO, CH3OH, HCN, and NH3 and we conducted a sensitive search for CH3D. We report rotational temperatures, production rates, and mixing ratios (with respect to H2O) at heliocentric distances of 1.49 AU (2004 November) and 1.21 AU (2005 January). We highlight three principal results. (1) The mixing ratios of parent volatiles measured at 1.49 AU and …

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Differentiating Unparticles From Extra Dimensions Via Mini Black Hole Thermodynamics, Jonas R. Mureika Mar 2009

Differentiating Unparticles From Extra Dimensions Via Mini Black Hole Thermodynamics, Jonas R. Mureika

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A thermodynamics-based method is presented for differentiating mini black hole creation mechanisms in high energy parton collisions, including scenarios with large compactified extra dimensions and unparticle-enhanced gravity with real scaling dimension dU. Tensor unparticle interactions are shown to mimic the physics of (2dU−2) noninteger extra spatial dimensions. This yields unique model-dependent production rates, Hawking temperature profiles, and decay multiplicities for black holes of mass MBH∼1–15  TeV that may be created at the LHC and other future colliders.

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Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten Sep 2008

Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten

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We present results of VLBI observations of the water masers associated with IRAS 4A and IRAS 4B in the NGC 1333 star-forming region taken in four epochs over a two month period. Both objects have been classified as extremely young sources, and each source is known to be a multiple system. Using the Very Long Baseline Array, we detected 35 masers in epoch I, 40 masers in epoch II, 35 in epoch III, and 24 in epoch IV. Only one identified source in each system is associated with these masers. These data are used to calculate proper motions for the …

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The Occurrence Of Ionospheric Signatures Of Plasmaspheric Plumes Over Different Longitudinal Sectors, E. Yizengaw, J. Dewar, J. Macneil, D. Galvan, Jeff Sanny, David Berube, B. Sandel Aug 2008

The Occurrence Of Ionospheric Signatures Of Plasmaspheric Plumes Over Different Longitudinal Sectors, E. Yizengaw, J. Dewar, J. Macneil, D. Galvan, Jeff Sanny, David Berube, B. Sandel

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Plasmaspheric plumes have ionospheric signatures and are observed as storm-enhanced density (SED) in global positioning system (GPS) total electron content (TEC). These ionospheric signatures have been primarily observed over the American sector and in a few limited examples over the European sector. This study examines the longitudinal occurrence frequency of plasmaspheric plumes. We analyzed all images from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Extreme Ultraviolet Imager (EUV) databases for the first half of 2001 and identified a total of 31 distinct plume intervals observed during different storm events. Out of the total IMAGE EUV plumes that we identified, 12 …

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A Simplex Model For Layered Niche Networks, Philip Fraundorf Jul 2008

A Simplex Model For Layered Niche Networks, Philip Fraundorf

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No abstract provided.

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The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva Jun 2008

The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva

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We report measurements of eight native (i.e., released directly from the comet nucleus) volatiles (H2O, HCN, CH4, C2H2, C2H6, CO, H2CO, and CH3OH) in comet 8P/Tuttle using NIRSPEC at Keck 2. Comet Tuttle reveals a truly unusual composition, distinct from that of any comet observed to date at infrared wavelengths. The prominent enrichment of methanol relative to water contrasts with the depletions of other molecules, especially C2H2, HCN, and H2CO. We suggest that the nucleus of 8P/Tuttle may contain two cometesimals characterized by distinct volatile composition. The relative abundances C2/CN, C2/OH, and CN/OH in 8P/Tuttle (measured at optical/near-UV wavelengths) differ …

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