Physical Sciences and Mathematics Commons^™

Detection Of Infall Signatures Towards Serpens Smm4, Gopal Narayanan, G. Moriarty-Schieven, C.K. Walker, H.M. Butner

Gopal Narayanan

We present the detection of kinematic infall signatures toward the Class 0 protostellar system SMM4 in the Serpens cloud core. We have observed the dense molecular gas toward the embedded source using millimeter and submillimeter line transitions of density sensitive molecular tracers. High signal-to-noise ratio maps obtained in HCO+ J = 1 → 0, J = 3 → 2, and J = 4 → 3, and CS J = 2 → 1 show the blue-bulge infall signature. The blue-bulge infall signature can be observed in the centroid velocity maps of protostellar objects when infall dominates over rotation. The line profiles …

Classical Gluodynamics In Curved Space-Time And The Soft Pomeron, Dmitri Kharzeev, Eugene Levin, Kirill Tuchin

Kirill Tuchin

QCD at the classical level possesses scale invariance which is broken by quantum effects. This "dimensional transmutation" phenomenon can be mathematically described by formulating classical gluodynamics in a curved, conformally flat, space-time with non-vanishing cosmological constant. We study QCD high-energy scattering in this theory. We find that the properties of the scattering amplitude at small momentum transfer are determined by the energy density of vacuum fluctuations. The approach gives rise to the power growth of the total hadron-hadron cross section with energy, i.e., the pomeron. The intercept of the pomeron and the multiplicity of produced particles are evaluated. We also …

The Planetary Nebula Spectrograph: The Green Light For Galaxy Kinematics, N. G. Douglas, M. Arnaboldi, K. C. Freeman, K. Kuijken, M. R. Merrifield, Aaron J. Romanowsky, K. Taylor, M. Capaccioli, T. Axelrod, R. Gilmozzi, J. Hart, G. Bloxham, D. Jones

Faculty Publications

Planetary nebulae (PNe) are now well established as probes of galaxy dynamics and as standard candles in distance determinations. Motivated by the need to improve the efficiency of planetary nebulae searches and the speed with which their radial velocities are determined, a dedicated instrument—the Planetary Nebula Spectrograph, or PN.S—has been designed and commissioned at the 4.2 m William Herschel Telescope. The high optical efficiency of the spectrograph results in the detection of typically ∼150 PNe in galaxies at the distance of the Virgo Cluster in one night of observations. In the same observation, the radial velocities are obtained with an …

The Afterglow And Complex Environment Of The Optically Dim Burst Grb 980613, Jens Hjorth, Bjarne Thomsen, Svend R. Nielsen, Michael I. Andersen, Stephen T. Holland, Johan U. Fynbo, Holger Pederson, Andreas O. Jaunsen, Jules P. Halpern, Robert Fesen, Javier Gorosabel, Alberto Castro-Tirado, Richard G. Mcmahon, Michael D. Hoenig, Gunnlaugur Bjornsson, Lorenzo Amati, Nial R. Tanvir, Priyamvada Natarajan

Dartmouth Scholarship

We report the identification of the optical afterglow of GRB 980613 in R- and I-band images obtained between 16 and 48 hr after the gamma-ray burst. Early near-infrared (NIR) H and K' observations are also reported. The afterglow was optically faint (R ≈ 23) at discovery but did not exhibit an unusually rapid decay (power-law decay slope α < 1.8 at 2 σ). The optical/NIR spectral index (β_RH < 1.1) was consistent with the optical-to-X-ray spectral index (β_RX ≈ 0.6), indicating a maximal reddening of the afterglow of ≈0.45 mag in R. Hence, the dimness of the optical afterglow was mainly due to the fairly flat spectral shape rather than internal reddening …

Five New Δ Scuti Stars, Gregory W. Henry, Francis C. Fekel

Information Systems and Engineering Management Research Publications

We present high‐resolution spectroscopy and precision photometry of five new, relatively bright δ Scuti stars. They were originally chosen as photometric comparison stars in our program of automated, high‐precision photometry of solar‐type stars and subsequently recognized as new variable stars. We conducted follow‐up spectroscopic and photometric observations to determine the properties of the stars and their types of variability. All five of the stars presented here belong to the most common subgroup of low‐amplitude, Population I δ Scuti variables. One of the stars, HD 10502, is the third example of a δ Scuti variable with composite broad and narrow spectroscopic …

A Prototype Asic For Apd Array Readout Of Scintillating Plastic Fibers, John R. Macri, A L. Wintenerg, Mark Widholm, U Jagadish, J Ledoux, Mark L. Mcconnell, S Shane Frank, Hansford H. Cutlip

Space Science Center

We report on the development of custom front-end electronics for use with avalanche photodiode (APD) arrays as part of a NASA technology study for the readout of scintillating plastic fibers. APD arrays featuring 64 1 mm square pixels are used. We demonstrate that a pixel of these APD arrays coupled to relatively thin (0.25 mm) and short (15 cm) scintillating plastic fibers can be used to detect and measure the tracks of even minimum ionizing particles (MIPs). An applicationspecific integrated circuit (ASIC) implementation of the electronics is required to produce a detector sufficiently compact for practical use in a flight …

Readout And Performance Of Thick Czt Strip Detectors With Orthogonal Coplanar Anodes, John R. Macri, B Donmez, L A. Hamel, Manuel Julien, M Mcclish, Mark L. Mcconnell, R S. Miller, James M. Ryan, Mark Widholm

Space Science Center

We report progress in the study of CZT strip detectors featuring orthogonal coplanar anode contacts. The work includes laboratory and simulation studies aimed at optimizing and developing compact, efficient, high performance detector modules for 0.05 to 1 MeV gamma radiation measurements. The novel coplanar anode strip configuration retains many of the performance advantages of pixel detectors yet requires far fewer electronic channels to perform both 3-d imaging and spectroscopy. We report on studies aimed at determining an optimum configuration of the analog signal processing electronics to employ with these detectors. We report measurements of energy and spatial resolution in three …

The Temporal Spectrum Of The Sdb Pulsating Star Hs 2201+2610 At 2 Ms Resolution, R Silvotti, T D. Oswalt, Nicole M. Silvestri, Glenn Carlson

Aerospace, Physics, and Space Science Faculty Publications

In this article we present the results of more than 180 hours of time-series photometry on the low gravity (log g = 5.4, Teff = 29 300 K, log He/H = -3.0 by number) sdB pulsating star HS 2201+2610, obtained between September 2000 and August 2001. The temporal spectrum is resolved and shows 5 close frequencies: three main signals at 2860.94, 2824.10 and 2880.69 μHz, with amplitudes of about 1%, 0.5% and 0.1% respectively, are detected from single run observations; two further peaks with very low amplitude (<0.07%) at 2738.01 and 2921.82 μHz are confirmed by phase analysis on several independent runs. Due to the small number of detected frequencies, it is not possible to obtain a univocal identification of the excited modes and perform a detailed seismological analysis of the star. No clear signatures of rotational splitting are seen. Nevertheless, the observed period spectrum is well inside the excited period window obtained from pulsation calculations with nonadiabatic models having effective temperature and surface gravity close to the spectroscopic estimates. Due to its relatively simple temporal spectrum, HS 2201+2610 is a very good candidate for trying to measure the secular variation of the pulsation periods in time. With this purpose a long-term monitoring of the star was started. The results of the first 11 months show amplitude variations up to ∼20% on time-scales of months, which are probably real, and allow us to measure the pulsation frequencies with an unprecedented 0.02 μHz resolution.

Asteroseismology Of Rxj 2117+3412, The Hottest Pulsating Pg 1159 Star, G Vauclair, Matt A. Wood

Aerospace, Physics, and Space Science Faculty Publications

The pulsating PG 1159 planetary nebula central star RXJ 2117+3412 has been observed over three successive seasons of a multisite photometric campaign. The asteroseismological analysis of the data, based on the 37 identified ℓ = 1 modes among the 48 independent pulsation frequencies detected in the power spectrum, leads to the derivation of the rotational splitting, the period spacing and the mode trapping cycle and amplitude, from which a number of fundamental parameters can be deduced. The average rotation period is 1.16 ± 0.05 days. The trend for the rotational splitting to decrease with increasing periods is incompatible with a …

Mutual Constraints Between Reionization Models And Parameter Extraction From Cosmic Microwave Background Data, Aparna Venkatesan

Physics and Astronomy

Spectroscopic studies of high-redshift objects and increasingly precise data on the cosmic microwave background (CMB) are beginning to independently place strong complementary bounds on the epoch of hydrogen reionization. Parameter estimation from current CMB data continues, however, to be subject to several degeneracies. Here, we focus on those degeneracies in CMB parameter forecasts related to the optical depth to reionization. We extend earlier work on the mutual constraints that such analyses of CMB data and a reionization model may place on each other to a more general parameter set and to the case of data anticipated from the MAP satellite. …

Book Review: The Observing Guide To The Messier Marathon: A Handbook And Atlas, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Observing Guide to the Messier Marathon : a Handbook and Atlas by Don Machholz. Cambridge, 2002 157p, 0-521-80386-1 $25.00.

Mass-Loss And Magnetospheres: X-Rays From Hot Stars And Young Stellar Objects, M. Gagné, David H. Cohen, S. P. Owocki, A. Ud-Doula

Physics & Astronomy Faculty Works

High-resolution X-ray spectra of high-mass stars and low-mass T-Tauri stars obtained during the first year of the Chandra mission are providing important clues about the mechanisms which produce X-rays on very young stars. For zeta Puppis (O4 If) and zeta Ori (O9.5 I), the broad, blue-shifted line profiles, line ratios, and derived temperature distribution suggest that the X-rays are produced throughout the wind via instability-driven wind shocks. For some less luminous OB stars, like theta^1 Ori C (O7 V) and tau Sco (B0 V), the line profiles are symmetric and narrower. The presence of time-variable emission and very high-temperature lines …

An Upper Limit To The Age Of The Galactic Bar, Aa Cole, Md Weinberg

Astronomy Department Faculty Publication Series

Using data from the Two Micron All Sky Survey, we identify a population of infrared carbon stars with J-KS ≥ 2 in the Milky Way. These stars are shown to trace the stellar bar previously identified in IR and optical surveys. The properties of C stars strongly suggest that they are of intermediate age. We conclude that the bar is likely to have formed more recently than 3 Gyr ago and must be younger than 6 Gyr. Implications and further tests of this conclusion are briefly discussed.

Sensitive Limits On The Water Abundance In Cold Low-Mass Molecular Cores, Ea Bergin, Ronald L. Snell

Astronomy Department Faculty Publication Series

We present Submillimeter Wave Astronomy Satellite observations of water vapor in two cold starless clouds, B68 and core D in ρ Ophiuchi. Sensitive nondetections of the 1₁₀-1₀₁ transition of o-H₂O are reported for each source. Both molecular cores have been previously examined by detailed observations that have characterized the physical structure. Using these rather well-defined physical properties and a Monte Carlo radiation transfer model, we have removed one of the largest uncertainties from the abundance calculation and set the lowest water abundance limit to date in cold low-mass molecular cores. These limits are x(o-H …

The Growth Of Galaxies In Cosmological Simulations, Jh Choi, N Katz, C Murali, D Weinberg, R Dave, L Hernquist

Astronomy Department Faculty Publication Series

We use hydrodynamic simulations to examine how the baryonic components of galaxies are assembled, focusing on the relative importance of mergers and smooth accretion in the formation of ~L_* systems. In our primary simulation, which models a (50 h^-1 Mpc)³ comoving volume of a Λ-dominated cold dark matter universe, the space density of objects at our (64 particle) baryon mass resolution threshold M_c = 5.4 × 10¹⁰ M corresponds to that of observed galaxies with L ~ L_*/4. Galaxies above this threshold gain most of their mass by accretion rather than by …

High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz

Astronomy Department Faculty Publication Series

We use hydrodynamic cosmological simulations to predict the star formation properties of high-redshift galaxies (z = 2-6) in five variants of the inflationary cold dark matter scenario, paying particular attention to z = 3, the redshift of the largest "Lyman break galaxy" (LBG) samples. Because we link the star formation timescale to the local gas density, the rate at which a galaxy forms stars is governed mainly by the rate at which it accretes cooled gas from the surrounding medium. At z = 3, star formation in most of the simulated galaxies is steady on ~200 Myr timescales, and …

X-Ray Scaling Relations Of Galaxy Groups In A Hydrodynamic Cosmological Simulation, R Dave, N Katz, Dh Weinberg

Astronomy Department Faculty Publication Series

We examine the scalings of X-ray luminosity, temperature, and dark matter or galaxy velocity dispersion for galaxy groups in a ΛCDM cosmological simulation, which incorporates gravity, gas dynamics, radiative cooling, and star formation, but no substantial nongravitational heating. In agreement with observations, the simulated L_X-σ and L_X-T_X relations are steeper than those predicted by adiabatic simulations or self-similar models, with L_X σ^4.4 and L_X T for massive groups and significantly steeper relations below a break at σ 180 km s^-1 (T_X 0.7 keV). The T_X-σ relation …

Title: Chandra Observations Of The Galactic Center And Nearby Edge-On Galaxies, Qd Wang

Astronomy Department Faculty Publication Series

I review our recent Chandra surveys of the center region of the Milky Way and other nearby edge-on galaxies. Our Galactic center survey provides an unprecedented high-resolution, broad-band X-ray panorama of a 0.8x2 square degree swath along the Galactic plane. Our preliminary analysis has led a detection of about 1000 discrete sources. We find that the diffuse X-ray emission dominates over the contribution from faint discrete sources and is globally associated with distinct interstellar structures observed at radio and mid-infrared wavelengths. We study how high-energy activities in the center region affect the immediate vicinity and may influence other aspects of …

The Nature Of The Faint Far-Infrared Extragalactic Source Population: Optical/Nir And Radio Follow-Up Observationts Of Isophot Deep-Field Sources Using The Keck, Subaru, And Vla Telescopes., Y Kakazu, Db Sanders, Rd Joseph, Ll Cowie, T Murayama, Y Taniguchi, S Veilleux, Min Yun, K Kawara, Y Sofue, Y Sato, H Okuda, K Wakamatsu, T Matsumoto, H Matsuhara

Astronomy Department Faculty Publication Series

In order to search for obscured objects at high redshifts, we have made deep far-infrared (FIR) deep survey in the Lockman Hole using ISOPHOT onboard ISO (Kawara et al. 1998, A&A, 336, L9). In this survey several tens of FIR sources have been found at 95micron and 175micron. Here we present results of optical and NIR spectroscopic followup observations performed at the W. M.Keck Observatory.

High-Resolution Imaging Of Molecular Line Emission From High-Redshift Qsos, Cl Carilli, K Kohno, R Kawabe, K Ohta, C Henkel, Km Menten, Min Yun, A Petric, Y Tutui

Astronomy Department Faculty Publication Series

We present moderate- (1'') and high-resolution (02) observations of the CO (2–1) emission at 43 GHz and radio continuum emission at 1.47 GHz from the z = 4.7 QSO BRI 1202-0725 and the z = 4.4 QSO BRI 1335-0417 using the Very Large Array. The moderate-resolution observations show that in both cases the CO emission is spatially resolved into two components separated by 1'' for BRI 1335-0417 and 4'' for BRI 1202-0725. The high-resolution observations show that each component has substructure on scales ~02–05, with intrinsic brightness temperatures ≥20 K. The CO ladder from (2–1) up to (7–6) suggests a …

Detection Of Infall Signatures Toward Serpens Smm4, Gopal Narayanan, G Moriarty-Schieven, Ck Walker, Hm Butner

Astronomy Department Faculty Publication Series

We present the detection of kinematic infall signatures toward the Class 0 protostellar system SMM4 in the Serpens cloud core. We have observed the dense molecular gas toward the embedded source using millimeter and submillimeter line transitions of density sensitive molecular tracers. High signal-to-noise ratio maps obtained in HCO⁺ J = 1 → 0, J = 3 → 2, and J = 4 → 3, and CS J = 2 → 1 show the blue-bulge infall signature. The blue-bulge infall signature can be observed in the centroid velocity maps of protostellar objects when infall dominates over rotation. The line …

Physical Parameter Eclipse Mapping Of The Quiescent Disc In V2051 Ophiuchi, S Vrielmann, R Stiening, W Offutt

Astronomy Department Faculty Publication Series

We analyse simultaneous UBVR quiescent light curves of the cataclysmic variable V2051 Oph using the Physical Parameter Eclipse Mapping (PPEM) method in order to map the gas temperature and surface density of the disc for the first time. The disc appears optically thick in the central regions, and gradually becomes optically thin towards the disc edge or shows a more and more dominating temperature inversion in the disc chromosphere. The gas temperatures in the disc range from about 13 500 K near the white dwarf to about 6000 K at the disc edge. The intermediate part of the disc has …

Discovery Of A 136 Millisecond Radio And X-Ray Pulsar In Supernova Remnant G54.1+0.3, F Camilo, Dr Lorimer, Ndr Bhat, Ev Gotthelf, Jp Halpern, Qd Wang, Fj Lu, N Mirabal

Astronomy Department Faculty Publication Series

We report the discovery of a pulsar with period P = 136 ms and dispersion measure 308 cm^-3 pc in a deep observation of the supernova remnant (SNR) G54.1+0.3 with the Arecibo radio telescope. Timing measurements of the new pulsar, J1930+1852, reveal a characteristic age of P/2 = 2900 yr and a spin-down luminosity of = 1.2 × 10³⁷ ergs s^-1. We have subsequently searched archival ASCA X-ray data of this SNR and detect pulsations with a consistent period. These findings ensure that PSR J1930+1852 is the pulsar that powers the "Crab-like" SNR G54.1+0.3. Together …

Chandra Observations Of The Bursting X-Ray Transient Sax J1747.0–2853 During Low-Level Accretion Activity, R Wijnands, Jm Miller, Qd Wang

Astronomy Department Faculty Publication Series

We present Chandra/ACIS observations of the bursting X-ray transient SAX J1747.0-2853 performed on 2001 July 18. We detected a bright source at the position of R.A. = 17^h47^m02.s60 and decl. = -28°52'589 (J2000.0, with a 1 σ error of ~07), consistent with the BeppoSAX and ASCA positions of SAX J1747.0-2853 and with the Ariel V position of the transient GX +0.2-0.2, which was active during the 1970s. The 0.5-10 keV luminosity of the source during our observations was ~ 3 × 10³⁵ ergs s^-1 (assuming a distance of 9 kpc), demonstrating that the …

X-Ray Thread G0.13–0.11: A Pulsar Wind Nebula?, Qd Wang, F Lu, Cc Lang

Astronomy Department Faculty Publication Series

We have examined Chandra observations of the recently discovered X-ray thread G0.13-0.11 in the Galactic center Radio Arc region. Part of the Chandra data was studied by Yusef-Zadeh, Law, & Wardle, who reported the detection of 6.4 keV line emission in this region. We find, however, that this line emission is not associated with G0.13-0.11. The X-ray spectrum of G0.13-0.11 is well-characterized by a simple power law with an energy slope of 1.8 (90% confidence uncertainties). Similarly, the X-ray spectrum of the pointlike source embedded in G0.13-0.11 has a power-law energy slope of 0.9. The 2-10 keV band luminosities of …

Fluorescence And Chromospheric Activity Of V471 Tau, Todd R. Vaccaro, Robert E. Wilson

Physics and Astronomy Faculty Publications

The red dwarf + white dwarf eclipsing binary V471 Tau shows a variable Hα feature that varies from absorption during eclipse to maximum emission during white dwarf transit. In 1998 we obtained simultaneous BVRI photometry and Hα spectroscopy, with thorough phase coverage of the 12.5 hour orbital period. A binary star model was used with our light curve, radial velocity, and Hα data to refine stellar and orbital parameters. Combined absorption-emission profiles were generated by the model and fit to the observations, yielding a red star radius of 0.94⊙. Orbital inclination 78° is required with this size and other known …

Detection Of X-Ray Emission From The Arches Cluster Near The Galactic Center, F Yusef-Zadeh, C Claw, M Wardle, Qd Wang, A Fruscione, Cc Lang, A Cortera

Astronomy Department Faculty Publication Series

The Arches cluster is an extraordinarily compact massive star cluster with a core radius of about 10'' (~0.4 pc) and consisting of more than 150 O star candidates with initial stellar masses greater than 20 M near G0.12-0.02. X-ray observations of the radio Arc near the Galactic center at l ~ 02, which contains the Arches cluster, have been carried out with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-Ray Observatory. We report the detection of two X-ray sources from the Arches cluster embedded within a bath of diffuse X-ray emission extending beyond the edge of the …

Chandra Observation Of Supernova Remnant G54.1+0.3: A Close Cousin Of The Crab Nebula, Fj Lu, Qd Wang, B Aschenbach, P Durouchoux, Lm Song

Astronomy Department Faculty Publication Series

We present a Chandra Advanced CCD Imaging Spectrometer observation of supernova remnant G54.1+0.3. This supernova remnant is resolved into several distinct X-ray-emitting components: a central bright pointlike source (CXOU J193030.13+185214.1), a surrounding ring, bipolar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-law models; the spectral index steepens with increasing distance from the pointlike source. We find no evidence for any thermal plasma emission that would correspond to shocked interstellar medium or ejecta. The observed morphological and spectral characteristics suggest that G54.1+0.3 is the closest "cousin" of the Crab Nebula—a pulsar …

Negative-Parity Baryon Masses Using An O(A)-Improved Fermion Action, M. Göckeler, R. Horsley, D. Pleiter, P. E. L. Rakow, G. Schierholz, C. M. Maynard, D. G. Richards

Physics Faculty Publications

We present a calculation of the mass of the lowest-lying negative-parity J=1/2− state in quenched QCD. Results are obtained using a non-perturbatively O(a)-improved clover fermion action, and a splitting is found between the mass of the nucleon, and its parity partner. The calculation is performed on two lattice volumes and at three lattice spacings, enabling a study of both finite-volume and finite lattice-spacing uncertainties. A comparison is made with results obtained using the unimproved Wilson fermion action.

Hiccups In The Night: X-Ray Monitoring Of The Two Crab-Like Lmc Pulsars, Ev Gotthelf, W Zhang, Fe Marshall, J Middleditch, Qd Wang

Astronomy Department Faculty Publication Series

We are undertaking an extensive X-ray monitoring campaign of the two Crab-like pulsars in the Large Magellanic Clouds, PSR B0540-69 and PSR J0537-6910. We present our current phase-connected timing analysis derived from a set of 50 pointed X-ray observations spanning several years. From our initial 1.2 yr monitoring program of the young 50 ms pulsar PSR B0540-69, we find the first compelling evidence for a glitch in its rotation. This glitch is characterized by Delta nu / nu = (1.90+-0.05) x 10^-9 and Delta nu_dot / nu_dot = (8.5+-0.5) x 10^-5. Taking into account the …