Stars, Interstellar Medium and the Galaxy Commons^™

Defining The Circumstellar Habitable Zone, Blake Cervetti, Joanna Mccall

DePaul Discoveries

The study of habitable exoplanets is a rapidly expanding field in astronomy. Exoplanets are planets that orbit stars other than our own sun. One of the keys to knowing whether or not an exoplanet is habitable is by studying the circumstellar habitable zone, or CHZ. Over the past several years, the defined limits of the CHZ have become susceptible to change as new parameters and factors are found to affect a planets habitability. There are many factors that affect its habitability, including the composition of the star, the mass of the planet, the planets atmosphere, etc. Our focus is divided …

Bayesian Analysis For Stellar Evolution With Nine Parameters (Base-9): User's Manual, Ted Von Hippel, Elliot Robinson, Elizabeth Jeffery, Rachel Wagner-Kaiser, Steven Degennaro, Nathan Stein, David Stenning, William H. Jefferys, David Van Dyk

Publications

BASE-9 is a Bayesian software suite that recovers star cluster and stellar parameters from photometry. BASE-9 is useful for analyzing single-age, single-metallicity star clusters, binaries, or single stars, and for simulating such systems. BASE-9 uses Markov chain Monte Carlo and brute-force numerical integration techniques to estimate the posterior probability distributions for the age, metallicity, helium abundance, distance modulus, and line-of-sight absorption for a cluster, and the mass, binary mass ratio, and cluster membership probability for every stellar object. BASE-9 is provided as open source code on a version-controlled web server. The executables are also available as Amazon Elastic Compute Cloud …

The Power Of Principled Bayesian Methods In The Study Of Stellar Evolution, Ted Von Hippel, David Van Dyk, David Stenning, Elliot Robinson, Elizabeth Jeffery, Nathan Stein, William Jefferys, Erin M. O'Malley

Publications

It takes years of effort employing the best telescopes and in- struments to obtain high-quality stellar photometry, astrometry, and spectroscopy. Stellar evolution models contain the experience of life- times of theoretical calculations and testing. Yet most astronomers fit these valuable models to these precious datasets by eye. We show that a principled Bayesian approach to fitting models to stellar data yields substantially more information over a range of stellar astrophysics. We highlight advances in determining the ages of star clusters, mass ratios of binary stars, limitations in the accuracy of stellar models, post-main-sequence mass loss, and the ages of individual …

The Optical Luminosity Function Of Gamma-Ray Bursts Deduced From Rotse-Iii Observations, X. H. Cui, X. F. Wu, J. J. Wei, F. Yuan, W. K. Zheng, E. W. Liang, C. W. Akerlof, M. C. B. Ashley, H A. Flewelling, E. Göǧüş, T. Güver, Ü. Kızıloǧlu, T. A. Mckay, S. B. Pandey, E. S. Rykoff, W. Rujopakarn, B. E. Schaefer, J. C. Wheeler, Sarah A. Yost

Physics Faculty Publications

We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs) and those with upper limits (40 GRBs). We derive R-band fluxes for these two sub-samples 100 s after the onset of the burst. The optical LFs at 100 s are fitted by assuming that the co-moving GRB rate traces the star formation rate. While fitting the optical LFs using Monte Carlo simulations, we take into account the …

Maximizing Precision Of Variable Star Photometry With Digital Cameras In Suburban Environments, David Hergesheimer

STAR Program Research Presentations

Photometry is the measure of the brightness of an object. When making such measurements on stars, it is done is units of magnitude, which is on a logarithmic scale with a base of ~2.512. Variable star photometry using a commercially available digital camera is not going to be as accurate and precise as equipment used by astronomers, and because of the logarithmic scale of magnitude used, determining how much of an effect different error reduction strategies have is not straightforward, and is best done experimentally.

My research is conducting photometry on variable stars (changing brightness) with a digital camera, and …

Characterization Of Samples For Optimization Of Infrared Stray Light Coatings, Carey L. Baxter, Rebecca Salvemini, Zaheer A. Ali, Patrick Waddell, Greg Perryman, Bob Thompson

STAR Program Research Presentations

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted 747SP that houses a 2.5 m telescope that observes the sky through an opening in the side of the aircraft. Because it flies at altitudes up to 45,000 feet, SOFIA gets 99.99% transmission in the infrared. Multiple science instruments mount one at a time on the telescope to interpret infrared and visible light from target sources. Ball Infrared Black (BIRB) currently coats everything that the optics sees inside the telescope assembly (TA) cavity in order to eliminate noise from the glow of background sky, aircraft exhaust, and other sources. A …

Analyzing The Performance Of The Sofia Infrared Telescope, Sarah M. Bass, Jeffrey Van Cleve, Zaheer Ali

STAR Program Research Presentations

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne near-space observatory onboard a modified Boeing 747-SP aircraft, which flies at altitudes of 45,000 ft., above 99% of the Earth’s water vapor. SOFIA contains an effective 2.5 m infrared (IR) telescope that has a dichroic tertiary mirror, reflecting IR and visible wavelengths to the science instrument (SI) and focal plane imager (FPI), respectively. To date, seven different SIs have been designed to cover a wide range of wavelengths and spectral resolutions. Since the telescope operates in the infrared, different techniques, including chopping, nodding, and dithering, are used to reduce the …

Flitecam Data Process Validation, Jesse K. Tsai, Sachindev S. Shenoy, Brent Cedric Nicklas, Zaheer Ali, William T. Reach

STAR Program Research Presentations

FLITECAM Data Processing Validation

Many of the challenges that come from working with astronomical imaging arise from the reduction of raw data into scientifically meaningful data. First Light Infrared Test CAMera (FLITECAM) is an infrared camera operating in the 1.0–5.5 μm waveband on board SOFIA (Stratospheric Observatory For Infrared Astronomy). Due to the significant noise from the atmosphere and the camera itself, astronomers have developed many methods to reduce the effects of atmospheric and instrumental emission. The FLITECAM Data Reduction Program (FDRP) is a program, developed at SOFIA Science Center, subtracts darks, removes flats, and dithers images.

This project contains …

Counting Photons To Calibrate A Photometer For Stellar Intensity Interferometry, Jason Chew

Physics

We use a telescope and photometer to observe stellar photons and measure the rate of observed photons. Based on intensity spectra from the Spectrophotometric Catalogue of Stars, we also predict expected values for the photon rates, which we compare to our measurements. From this comparison, we measure the local optical depth to be τ = 0.60±0.25, a reasonable value. We find that our predictions are directly proportional to our measurements by a factor of 0.98 (+0.02, -0.27) . The similarity between our measurements and expectations shows that we are able to both predict and measure photon rates with accuracy.

Telescope Assembly Alignment Simulator Performance Optimization, Joshua G. Thompson, Brian Eney, Zaheer Ali, Bob Thompson

STAR Program Research Presentations

The Telescope Assembly Alignment Simulator (TAAS) calibrates scientific instruments (SI’s) that are installed on the Stratospheric Observatory For Infrared Astronomy (SOFIA). An SI’s accuracy is directly dependent on the consistent performance of the TAAS, which has never been fully characterized. After designing various thermal and optical experiments to identify the current unknowns of TAAS, we now have a far better grasp on how the equipment behaves.

Identifying A New Intermediate Polar Using Xmm-Newton And Integral, Matthew J. Middleton, Edward M. Cackett, Craig Shaw, Gavin Ramsay, Timothy P. Roberts, Peter J. Wheatley

Physics and Astronomy Faculty Research Publications

The bright X-ray source 2XMMi J180438.7-145647 is fortunate to have long baseline observations in INTEGRAL that complement observations taken by other missions. Optical spectroscopy of this object has suggested a distance of ˜7 kpc and an identification with a low-mass X-ray binary. We instead use the X-ray data from 0.3 to 40 keV to identify the source as a bright intermediate polar (IP) with an estimate for the white dwarf mass of ˜0.60 M_⊙. This identification is supported by the presence of an iron triplet, the component lines of which are some of the strongest seen in IPs, …

Arcade 2 Observations Of Galactic Radio Emission, A. Kogut, D. J. Fixsen, S. M. Levin, M. Limon, P. M. Lubin, P. Mirel, M. Seiffert, Jack Singal, T. Villela, E. Wollack, C. A. Wuensche

Physics Faculty Publications

We use absolutely calibrated data from the ARCADE 2 flight in 2006 July to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free–free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index βsynch = −2.5±0.1, with free–free emission contributing 0.10±0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc |b| dependence or a model …

A New Pulsar Instrumentation At The Allen Telescope Array And The Nancay Radio Telescope, G. Desvignes, William C. Barott, I. Cognard, P. Lespagnol, G. Theureau

Publications

In the prospect of the gravitational wave background detection with high precision pulsar timing, we recently installed a new coherent dedispersion backend at the Allen Telescope Array (ATA) and the Nançay Radio Telescope (NRT).

On Relativistic Disk Spectroscopy In Compact Objects With X-Ray Ccd Cameras, J. M. Miller, A. D'Aì, M. W. Bautz, S. Bhattacharyya, D. N. Burrows, E. M. Cackett, A. C. Fabian, M. J. Freyberg, F. Haberl, J. Kennea, M. A. Nowak, R. C. Reis, T. E. Strohmayer, M. Tsujimoto

Physics and Astronomy Faculty Research Publications

X-ray charge-coupled devices (CCDs) are the workhorse detectors of modern X-ray astronomy. Typically covering the 0.3-10.0 keV energy range, CCDs are able to detect photoelectric absorption edges and K shell lines from most abundant metals. New CCDs also offer resolutions of 30-50 (E/ΔE), which is sufficient to detect lines in hot plasmas and to resolve many lines shaped by dynamical processes in accretion flows. The spectral capabilities of X-ray CCDs have been particularly important in detecting relativistic emission lines from the inner disks around accreting neutron stars and black holes. One drawback of X-ray CCDs is that spectra can be …

The Cosmic Ray Observatory Project: A Statewide Outreach And Education Ex-Periment In Nebraska, Daniel Claes, Gregory Snow

Gregory Snow Publications

Abstract: The Cosmic Ray Observatory Project (CROP) is a statewide education and research ex-periment involving Nebraska high school students, teachers and university undergraduates in the study of extensive cosmic-ray air showers. A network of high school teams construct, install, and op-erate school-based detectors in coordination with University of Nebraska physics professors and graduate students. The detector system at each school is an array of scintillation counters recycled from the Chicago Air Shower Array in weather-proof enclosures on the school roof, with a GPS re-ceiver providing a time stamp for cosmic-ray events. The detectors are connected to triggering elec-tronics and a …

Probing The Universe On Gigaparsec Scales With Remote Cosmic Microwave Background Quadrupole Measurements, Emory F. Bunn

Physics Faculty Publications

Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces a polarization signal proportional to the CMB quadrupole anisotropy at the cluster’s location and lookback time. A survey of such remote quadrupole measurements provides information about large-scale cosmological perturbations. This paper presents a formalism for calculating the correlation function of remote quadrupole measurements in spherical harmonic space. The number of independent modes probed by both single-redshift and volume-limited surveys is presented, along with the length scales probed by these modes. In a remote quadrupole survey sparsely covering a large area of sky, the largest-scale modes probe the same-length scales …

Stargazing: Observatories At Gettysburg College, 1874-Present, Andrew A. Carlson

Hidden in Plain Sight Projects

Astronomy has long been a subject which has attracted the interest of man. Examples of early astronomers can be found in many ancient civilizations, including but not limited to, the Egyptians, the Chinese and the Greeks. As time passed the methods for interpreting the stars and theories that surrounded them changed concordant with the technology available. One of the largest breakthroughs in the world of astronomy was the invention of the telescope in the early seventeenth century. Often mis-attributed to Galileo (who was responsible for building the first reflecting telescope in 1688), the telescope was actually first designed by a …

Redshift-Distance Survey Of Early-Type Galaxies: Circular-Aperture Photometry, M. V. Alonso, M. Bernardi, L. N. Da Costa, G. Wegner

Dartmouth Scholarship

We present R -band CCD photometry for 1332 early-type galaxies, observed as part of the ENEAR survey of peculiar motions using early-type galaxies in the nearby universe. Circular apertures are used to trace the surface brightness profiles, which are then fitted by a two-component bulge-disk model. From the fits, we obtain the structural parameters required to estimate galaxy distances using the Dn - and fundamental plane relations. We find that about 12% of the galaxies are well represented by a pure r1/4 law, while 87% are best fitted by a two-component model. There are 356 repeated observations of 257 galaxies …

The Recent High State Of The Bl Lacertae Object Ao 0235 And Cross-Correlations Between Optical And Radio Bands, M. Roy, I. E. Papadikis, E. Ramos-Colon, R. Sambruna, K. Tsinganos, J. Papamastorkis, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present new optical (B, V , R, I) and radio (at 14.5, 8.5, and 4.8 GHz) observations of the γ-ray- loud blazar AO 0235+164 obtained during the high state of 1997 December-1998 January. The data were combined with historical light curves from the literature to study correlated optical and radio variations over a time span of more than 20 years. Flux variability with large and energy-dependent amplitude is observed at both wave bands, with the source varying over all timescales sampled (years-months- days), in agreement with previous reports. We have performed a cross-correlation analysis of optical and radio light …

Contemporaneous Iue, Euve, And High-Energy Observations Of 3c 273, E. Ramos, Menas Kafatos, A. Fruscione, F. C. Bruhweiler, I. M. Mchardy, R. C. Hartman, L. G. Titarchuk, C. Von Montigny

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present the results of our 1994 January and 1995 January observations of the quasar 3C 273 obtained with the International Ultraviolet Explorer (IUE) and the Extreme-Ultraviolet Explorer (EUV E). These observations were part of a large multiwavelength campaign to observe 3C 273 from radio through γ-rays. Our 1995 January photometric observations with the EUV E Lexan/B Deep Survey (DS) instrument indicate strong evidence for variability, at a 99% confidence level, during the 12 day observing period. We have utilized ROSAT PSPC soft X-ray power-law models to correlate with EUV E count rates. Besides variations in the normalization level between …

Lateral Shock Of The R Aquarii Jet, J. M. Hollis, J. A. Pedelty, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The R Aqr jet was observed with the VLA B-configuration at two epochs separated by ~13.2 yr. Comparison of the resulting 6 cm continuum images show that the radio jet has undergone a lateral counterclockwise rotation of ~6-12 on the plane of the sky. The model of jet parcels on independent trajectories is difficult to reconcile with these observations and leads us to consider a path-oriented jet (i.e., younger parcels follow the same path as older parcels). Comparison of the most recent radio image with a nearly contemporaneous HST /FOC ultraviolet image at ~2330 A suggests that the ultraviolet emission …

Multiwavelength Blazar Studies, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The present report concerns the following projects 'High energy emission from hot accretion disks from active galactic nuclei'; 'OSSE spectral timing and monitoring observations of Cygnus X- 1'; 'OSSE observations of blazars'; and 'Search for correlated time variations of bright EGRET blazars'. The most favored model for the central engine inAGNs is the supermassive black hole hypothesis (Rees 1978). The observed luminosities range from approx. 10 logical and 44-45 erg /s for objects such as Mk 421 and Seyferts to as much as approx. 10logical and 47 for powerful QSOs such as 3C 273 and 3C 279, a large fraction …

Multifrequency Studies, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The present report concerns the following projects 'Multifrequency observations of the BL Lacertae object MK 421"; "EUVE and multifrequency observations of the quasars 3C 273 and 3C 279"; "EUVE observations of the symbiotic star RAquarii"; and "Morphology of the local HI void and ionization of He in the local ISM". The common theme of the above projects is UV observations and analysis of a wide range of astrophysical classes or objects, from the diffuse interstellar medium, to symbiotic stars (R Aqr), to active galactic nuclei (AGNs). Understanding the local (primarily neutral hydrogen or HI) interstellar medium is of great importance …

Osse Observations In Blazars, K. Mcnaron-Brown, W. N. Johnson, G. V. Jung, R. L. Kinzer, J. D. Kurfess, M. S. Strickman, C. D. Dermer, D. A. Grabelsky, W. R. Purcell, M. P. Ulmer, Menas Kafatos, P. A. Becker, R. Staubert, M. Maisack

Mathematics, Physics, and Computer Science Faculty Articles and Research

Results are reported on observations obtained with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO) of 17 active galactic nuclei (AGNs) known to exhibit blazar properties at other wavelengths. These observations span the period from 1991 June through 1994 May. Of the 33 high-confidence EGRET detections of blazars during CGRO observing phases 1 and 2 (1991 May 16-1993 September 7), OSSE has observed eight and detected five, namely 3C 273, 3C 279, PKS 0528+134, CTA 102, and 3C 454.3. Additionally, OSSE has detected the BL Lac sources H1517+65.6 and PKS 2155-304, which were not …

Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

This paper is a comprehensive study of all far-UV spectra obtained with the International Ultraviolet Explorer (IUE) satellite of the symbiotic star R Aquarii (R Aqr) covering a 13 yr period between 1979 and 1992. We have analyzed the ultraviolet emission for the compact H II region and the NE and SW extended "jetlike" filamentary structures. The results of our ultraviolet analysis indicate that the H II region and features A, B, and D of the NE jet are increasing in intensity, while the SW counterjet, feature A', has declined in intensity. We have found much stronger evidence that the …

A Far-Ultraviolet Atlas Of Symbiotic Stars Observed With Iue. I. The Swp Range, S. R. Meier, Menas Kafatos, R. P. Fahey, A. G. Michalitsianos

Mathematics, Physics, and Computer Science Faculty Articles and Research

This atlas contains sample spectra from the far-ultraviolet observations of32 symbiotic stars obtained with the lnternational Ultraviolet Explorer (IUE) satellite. In all, 394 low-resolution spectra from the short-wavelength pnmary (SWP) camera covering the range 1200-2000 A have been extracted from the IUE archive, calibrated, and measured. Absolute line fluxes and wavelengths for the prominent emission lines have been tabulated. Tables of both the general properties of these symbiotics and of features specific to the spectrum of each are included. The spectra shown are representative of the different classes of symbiotic stars that are currently in the IUE archive. These include …

Evidence Signalling The Start Of Enhanced Counterjet Flow In The Symbiotic System R Aquarii, A. G. Michalitsianos, M. Perez, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The velocity structure of strong far-UV emission lines observed in the symbiotic variable R Aqr suggests the start of new jet activity which will probably culminate in the appearance of a series of intense nebular emission knots within a decade. This is indicated by a systematic redward wavelength drift of emission lines, which we have followed with the International Ultraviolet Explorer (IV E) since the discovery of the brilliant northeast jet emission knots more than 10 years ago. The C IV λλ1548, 1550 resonance lines, which previously showed a prominent blue asymmetric wing that extended to velocities in excess -200 …

Extended Variability Of The Symbiotic Star Ag Draconis, Menas Kafatos, S. R. Meier

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have analyzed the complete set of available IUE (International Ultraviolet Explorer) spectra for the symbiotic star AG Draconis covering the period from 1979 to 1989. All absolute line fluxes and wavelengths have been obtained for the prominent emission lines in the λλ1200-3200 wavelength range. These spectra contain observations which were taken before, during and after the two extended outbursts which occurred on 1980 November to 1981 November and 1985 February to 1986 January. These two outburst events have two maxima that are separated by ~1600 days, a time scale not known to be associated with the star, but which …

Fe Ii Fluorescence And Anomalous C Iv Doublet Intensities In Symbiotic Novae, A. G. Michalitsianos, Menas Kafatos, S. R. Meier

Mathematics, Physics, and Computer Science Faculty Articles and Research

Symbiotic stars frequently exhibit anomalous C IV λλ1548.2, 1550.8 doublet flux ratios, in which the intensity ratio of the blue and red doublet members is below the optically thick limit of unity. Three symbiotic stars (RR Tel, RX Pup, and AG Peg) have been investigated in detail with high-resolution spectra obtained from the International Ultraviolet Explorer (IUE) archives. We have examined the deficit of C IV λ1548.2 emission relative to λ1550.8 in context with the fluorescent pumping of the Fe II multiplet (45.01) λ1548.204 by the C IV λ1548.2 line. In RR Tel the C IV λ1548.2 flux is correlated …

Ultraviolet And Optical Spectroscopy Of The R Aquarii Symmetrical Jet, J. M. Hollis, R. J. Oliverson, Menas Kafatos, A. G. Michalitsianos, R. M. Wagner

Mathematics, Physics, and Computer Science Faculty Articles and Research

The first ultraviolet spectrum of the southwest (SW) component of the symmetrical jet in the R Aquarii binary system has been obtained in the range 1200-2000 A with the International Ultraviolet Explorer (IUE). These results are compared to more encompassing spectra (1200-3200 A) of the central H II region taken at the same time and also similar spectra of the northeast (NE) jet component obtained 6 months earlier. Moreover, optical spectra of both the NE and SW jet components in the range 3400-9800 A were obtained within ~ 6 months and ~ 1 month, respectively, of the ultraviolet spectra. These …