Astrophysics and Astronomy Commons^™

Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars - Ii. The Epoch 2001 [Fe/H] Catalog, B. J. Taylor

Faculty Publications

This paper describes the derivation of an updated statistical catalog of metallicities. The stars for which those metallicities apply are of spectral types F, G, and K, and are on or near the main sequence. The input data for the catalog are values of [Fe/H] published before 2002 February and derived from lines of weak and moderate strength. The analyses used to derive the data have been based on one-dimensional LTE model atmospheres. Initial adjustments which are applied to the data include corrections to a uniform temperature scale which is given in a companion paper (see Taylor 2003). After correction, …

Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars, B. J. Taylor

Faculty Publications

This paper is one of a pair in which temperatures and metallicity catalogs for class IV-V stars are considered. The temperature catalog described here is derived from a calibration based on stellar angular diameters. If published calibrations of this kind are compared by using color-index transformations, temperature-dependent differences among the calibrations are commonly found. However, such differences are minimized if attention is restricted to calibrations based on Johnson V-K. A calibration of this sort from Di Benedetto (1998) is therefore tested and adopted. That calibration is then applied to spectroscopic and photometric data, with the latter predominating. Cousins R-I photometry …

Identification Of Cool White Dwarfs In The Noao Deep Wide-Field Survey, M. Kilic, Don E. Winget, T. Von Hippel, C.F. Claver

Publications

The chronology of star formation is recorded in the white dwarf luminosity function (WDLF). White dwarf (WD) structure implies a relatively simple connection between WD luminosity and age. First attempts to exploit WDs as chronometers [3,4,6] showed that the WDLF was a map of the history of star formation in the disk, and a significant shortfall of low-luminosity degenerates–the inevitable consequence of the finite age of the disk. The shortfall near log(L/L⊙)≈−4.5 implies a disk age of 6.5–9.5 Gyr [2]. The WDLF from wide common proper motion binaries [5] does not show the shortfall seen by Liebert et al. (1988). …

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 …

Comparison Of Stellar Angular Diameters From The Npoi, The Mark Iii Optical Interferometer, And The Infrared Flux Method, Tyler E. Nordgren, Jeffrey J. Sudol, D. Mozurkewich

Physics & Engineering Faculty Publications

No abstract provided.

The Cataclysmic Variable Cw 1045+525: A Secondary-Dominated Dwarf Nova?, C. Tappert, J. R. Thorstensen, W. H. Fenton, N. Bennert

Dartmouth Scholarship

We present spectroscopic and photometric observations of the cataclysmic variable CW 1045+525. Both the optical spectrum and the photometric lightcurve show a strong contribution of a K5V–M0V secondary. We derive an orbital period Porb = 0.271278(1) d by measuring the radial velocities of the absorption lines of the secondary. The period and spectral type of the secondary suggest a distance of 350–700 pc. There is evidence for additional sources of line- and continuum emission, but no direct evidence of an accretion disc. We discuss several scenarios for the nature of CW 1045+525 on the basis of our results, finding a …

Statistics And Supermetallicity: The Metallicity Of Mu Leonis, B. J. Taylor

Faculty Publications

For the often-studied "SMR" giant µ Leo, Smith & Ruck (2000) have recently found that [Fe/H] approximately + 0.3 dex. Their conclusion is tested here in a "statistical" paradigm, in which statistical principles are used to select published high-dispersion µ Leo data and assign error bars to them. When data from Smith & Ruck and from Takeda et al. (1998) are added to a data base compiled in 1999, it is found that conclusions from an earlier analysis (Taylor 1999c) are essentially unchanged: the mean value of [Fe/H] approximately + 0.23 ± 0.025 dex, and values ≤ + 0.2 dex …

Spectroscopy And Orbital Periods Of Four Cataclysmic Variable Stars, John R. Thorstensen, Cynthia J. Taylor

Dartmouth Scholarship

We present spectroscopy and orbital periods P_orb of four relatively little-studied cataclysmic variable stars. The stars and their periods are: AF Cam, P_orb = 0.324(1) d (the daily cycle count is slightly ambiguous); V2069 Cyg (= RX J2123.7+4217), 0.311683(2) d; PG 0935+075, 0.1868(3) d; and KUV 03580+0614, 0.1495(6) d. V2069 Cyg and KUV 03580+0614 both show He iiλ4686 emission comparable in strength to Hβ. V2069 Cyg appears to be a luminous nova-like variable, and the strong He ii suggests it may be an intermediate polar. The period of KUV 03580+0614 is similar to members …

Statistics And Supermetallicity: The Metallicity Of Ngc 6791, B. J. Taylor

Faculty Publications

For the old galactic cluster NGC 6791, Peterson & Green (1998a) and Chaboyer et al. (1999) have found that [Fe/H] approximately + 0.4 dex. A second look at that conclusion is taken in this paper. Zero-point problems are reviewed for a high-dispersion analysis done by Peterson & Green, and it is found that accidental errors have not been determined rigorously for the results of that analysis. It is also noted that in a color-magnitude analysis performed by Chaboyer et al., the important metallicity range between 0.0 and + 0.3 dex is not explored and hence is not ruled out. Moreover, …

Heavy‐Element Diffusion In Metal‐Poor Stars, Brian Chaboyer, W. H. Fenton, Jenica E. Nelan, D. J. Patnaude, Francesca E. Simon

Dartmouth Scholarship

Stellar evolution models that include the effect of helium and heavy-element diffusion have been calculated for initial iron abundances of [Fe/H] = -2.3, -2.1, -1.9, and -1.7. These models were calculated for a large variety of masses and three separate mixing lengths, α = 1.50, 1.75, and 2.00 (with α = 1.75 being the solar calibrated mixing length). The change in the surface iron abundance for stars of different masses was determined for the ages of 11, 13, and 15 Gyr. Iron settles out of the surface convection zone on the main sequence ; this iron is dredged back up …

A Search For Previously Unrecognized Metal-Poor Subdwarfs In The Hipparcos Astrometric Catalogue, I. N. Reid, F. Van Wyk, F. Marang, G. Roberts, D. Kilkenny, S. Mahoney

Dartmouth Scholarship

We have identified 317 stars included in the Hipparcos astrometric catalogue that have parallaxes measured to a precision of better than 15 per cent, and the location of which in the (M_V,(B−V)_T) diagram implies a metallicity comparable to or less than that of the intermediate‐abundance globular cluster M5. We have undertaken an extensive literature search to locate Strömgren, Johnson/Cousins and Walraven photometry for over 120 stars. In addition, we present new UBV(RI)_C photometry of 201 of these candidate halo stars, together with similar data for a further 14 known metal‐poor subdwarfs. These …

0920+3517_Nir_Spex, Maria Teresa Ruiz

Publications and Research

No abstract provided.

The Long-Period Orbit Of The Dwarf Nova V630 Cassiopeiae, J. A. Orosz, J. R. Thorstensen, R. K. Honeycutt

Dartmouth Scholarship

We present extensive spectroscopy and photometry of the dwarf nova V630 Cassiopeiae. A late-type (K4-5) absorption spectrum is easily detectable, from which we derive the orbital parameters. We find a spectroscopic period of P=2.56387 +/- (4 times 10^{-5}) days and a semiamplitude of K_2=132.9 +/- 4.0 km/s. The resulting mass function, which is a firm lower limit on the mass of the white dwarf, is then f(M)=0.624 +/- 0.056 solar masses. The secondary star is a ``stripped giant'', and using relations between the core mass and the luminosity and the core mass and the radius we derive a lower limit …

Astrophysical Quantities Of Cepheid Variables Measured With The Navy Prototype Optical Interferometer, Tyler E. Nordgren, J. T. Armstrong, M. E. Germain, R. B. Hindsley, Arsen R. Hajian, Jeffrey J. Sudol, C. A. Hummel

Physics & Engineering Faculty Publications

No abstract provided.

Low-Mass Spectroscopic Binaries In The Hyades: A Candidate Brown Dwarf Companion, I. Neill Reid, S. Mahoney

Dartmouth Scholarship

We have used the HIRES echelle spectrograph on the Keck I telescope to obtain high-resolution spectroscopy of 51 late-type M dwarfs in the Hyades cluster. Cross-correlating the calibrated data against spectra of white dwarfs allows us to determine heliocentric velocities with an accuracy of ±0.3 km s⁻¹. 27 stars were observed at two epochs in 1997; two stars, RHy 42 and RHy 403, are confirmed spectroscopic binaries. RHy 42 is a double-lined, equal-mass system; RHy 403 is a single-lined, short-period binary, P∼1.275 d. RHy 403A has an absolute magnitude of M_I=10.85, consistent with a mass …

1237+6526_Opt_Lris, Adam J. Burgasser

Publications and Research

No abstract provided.

Spectroscopy And Orbital Periods Of The Old Novae V533 Herculis, V446 Herculis And X Serpentis, J. R. Thorstensen, C. J. Taylor

Dartmouth Scholarship

We report spectroscopic orbital periods of 0.147 d (= 3.53 h) for V533 Her, 0.207 d (= 4.97 h) for V446 Her and 1.478 d for X Ser. V533 Her (Nova Herculis 1963) shows absorption features in its He i and Balmer lines which appear only in a limited range of orbital phase, suggesting that it is a low-inclination SW Sextantis star. V446 Her is unusual in that it has started normal dwarf nova eruptions after a nova outburst, but we find nothing else unusual about it — in particular, a distance estimate based on its dwarf nova outbursts agrees …

A Newly-Discovered Cataclysmic Binary Near The Rosat Galactic Plane Source Rx J1910.8+2856, J R. Thorstensen, F Haberl

Dartmouth Scholarship

We report the discovery of a new cataclysmic binary star from the ROSAT Galactic Plane Survey. The star has V >∼ 18.5atminimumlightandwehavemeasureditasbrightasV = 15.7. Spectroscopy shows broad hydrogen and helium emission lines; HeII λ4686 is not detected. Hα radial velocities yield an orbital period of 0.1429 ± 0.0004 d (3.430 ± 0.010 h). Time- series photometry covering one orbital cycle near maximum light shows irregular variability, but no evidence of an eclipse. ThesystemappearstobeanewdwarfnovaoftheUGemorZ Cam type, and is unlikely to be a magnetic system. Its period is unusually short for a U Gem star.

Curiously, the new cataclysmic binary is 83′′ …

Stellar Angular Diameters Of Late-Type Giants And Supergiants Measured With The Navy Prototype Optical Interferometer, Tyler E. Nordgren, M. E. Germain, J. A. Benson, D. Mozurkewich, Jeffrey J. Sudol, N. M. Elias Ii, Arsen R. Hajian, N. M. White, D. J. Hutter, K. J. Johnston, F. S. Gauss, J. T. Armstrong, T. A. Pauls, L. J. Rickard

Physics & Engineering Faculty Publications

No abstract provided.

Metallicity Calibration Of A Ddo Cn Index And Other Low-Resolution Indices For G And K Stars, B. J. Taylor

Faculty Publications

Metallicity calibrations of low-resolution parameters are potentially useful for (at least) two problems: the properties of moving groups, and the supermetallicity problem in K giants. In this paper, metallicity calibrations are derived for six sets of parameters. One of these parameters is the DDO CN index deltaCN. This parameter and three others are calibrated for use with evolved G and K stars. Two additional sets of low-resolution parameters are calibrated for use with G and K dwarfs. The calibrations are derived by comparing the input data with two catalogs of homogenized high-dispersion results from diverse authors (see Taylor 1995, 1999a). …

Mid-Infrared Visibility Measurements Of Evolved Stars, Jeffrey J. Sudol, H. M. Dyck, R. E. Stencel, D. I. Klebe, M. J. Creech-Eakman

Physics & Engineering Faculty Publications

No abstract provided.

A Zero Point And Accidental Errors For Published Values Of [Fe/H] For Cool Giants, B. J. Taylor

Faculty Publications

This paper is one of a series based on published values of [Fe/H] for late-type evolved stars. Only values of [Fe/H] from high-dispersion spectroscopy or related techniques are used. The narrative in this paper begins at a point where mean values of [Fe/H] have been derived for xiVir, alphaBoo, betaGem, and the Hyades giants. By using these stars as standard stars when necessary, a zero-point data base is assembled. This data base is then expanded into its final version by correcting and adding additional data in a step-by-step process. As that process proceeds, data comparisons are used to establish rms …

Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor

Faculty Publications

A catalog of mean values of [Fe/H] for evolved G and K stars is described. The zero point for the catalog entries has been established by using differential analyses. Literature sources for those entries are included in the catalog. The mean values are given with rms errors and numbers of degrees of freedom, and a simple example of the use of these statistical data is given. For a number of the stars with entries in the catalog, temperatures have been determined. A separate catalog containing those data is briefly described.

Aquila X-1: A Low-Inclination Soft X-Ray Transient, T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman

Dartmouth Scholarship

We have obtained I-band photometry of the neutron star X-ray transient Aql X-1 during quiescence. We find a periodicity at 2.487 cycles d⁻¹, which we interpret as twice the orbital frequency (19.30±0.05 h). Folding the data on the orbital period, we model the light-curve variations as the ellipsoidal modulation of the secondary star. We determine the binary inclination to be 20°–30° (90 per cent confidence) and also determine the 95 per cent upper limits to the radial velocity semi-amplitude and rotational broadening of the secondary star to be 117 and 50 km s⁻¹, respectively.

A Photometric And Spectroscopic Study Of The Cataclysmic Variable Sx Leonis Minoris In Quiescence And Superoutburst, R. Mark Wagner, John R. Thorstensen, R. K. Honeycutt, S. B. Howell

Dartmouth Scholarship

We present CCD imaging, CCD photometry on long and short timescales, and time-resolved spectroscopy of SX LMi, a new SU Ursae Majoris type dwarf nova. The quiescent optical spectrum shows broad double-peaked Balmer, He I, and He II emission lines, similar to other quiescent dwarf novae. Absorption lines from a late-type secondary are not detected. Time-resolved spectra obtained in quiescence reveal radial velocity variations of the Balmer emission lines on a period of 0.06717 ± 0.00011 days, or 96.72 ± 0.16 minutes, with only a slight possibility of a daily cycle-count error. Optical photometry obtained between 1987 and 1991 shows …

Pulsations And Accretion Geometry In Yy Draconis: A Study Based On Hubble Space Telescope Observations, Carole A. Haswell, Joseph Patterson, John R. Thorstensen, Coel Hellier

Dartmouth Scholarship

We present 1 Å resolution fast ultraviolet spectroscopy of YY Dra, coordinated U, B, V, R, and I photometry, and Hα spectroscopy. The UV continuum is strongly pulsed: we found 16% semiamplitude pulses with period 264.7(1) s; there was no evidence for power at twice this period. The UBV pulses are in phase with the UV continuum pulsation. A color temperature of 10⁵ K was found for the pulse spectrum, with a corresponding area 0.5% of the white dwarf surface. We refine the white dwarf spin period, obtaining P_spin = 529.31 ± 0.02 s. Optical pulses at …

Gamma-Ray Observations Of Gro J1655-40, R Kroeger, Mark Strickman, J E. Grove, Philip Kaaret, E. Ford, B A. Harmon, Mark L. Mcconnell

Physics & Astronomy

The bright transient X-ray source GRO J1655-40 = XN Sco 1994 was observed by the OSSE instrument on the Compton Gamma Ray Observatory (GRO). Preliminary results are reported here. The initial outburst from GRO J1655-40 was detected by BATSE on 27 Jul 1994. OSSE observations were made in five separate viewing periods starting between 4 Aug 1994 and 4 Apr 1995. The first, third, and fifth observations are near the peak luminosity. In the second observation, the source flux had dropped by several orders of magnitude and we can only set an upper limit. The fourth observation is a weak …

The Orbital Period Of Bk Lyncis (Pg 0917 + 342), F. A. Ringwald, J. R. Thorstensen, R. K. Honeycutt, J. W. Robertson

Dartmouth Scholarship

Long-term light curves of the cataclysmic variable BK Lyn = PG 0917 + 342 from the Indiana Automated CCD photometric telescope (‘RoboScope’) and the Harvard College Observatory plate archive reveal no dwarf nova outbursts. Two radial velocity studies show its orbital period to be 107.97 ;1 0.07 min, confirming that it does have an orbital period shorter than the period gap for cataclysmic variables. Whether this is the first nova-like variable below the period gap or a dwarf nova with rare outbursts resembling WZ Sge is still unclear, however.

The Orbital Period Of The Pre-Cataclysmic Binary Re 2013+400 And A Study Of The Atmosphere Of The Dao White Dwarf Primary, M. A. Barstow, M. R. Burleigh, T. A. Fleming, J. B. Holberg, D. Koester, M. C. Marsh, S. R. Rosen, R. G.M. Rutten, S. Sakai, R. W. Tweedy, G. Wegner

Dartmouth Scholarship

Several pre-cataclysmic binaries, comprising a hot white dwarf with a red dwarf companion, have been discovered as a result of the optical identification of EUV sources from the ROSAT all-sky survey. The optical spectra have the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of H I (and sometimes He I and Ca II) superimposed. An intense campaign of follow-up observations has been devoted to these binary systems. So far, only RE 2013+400 has exhibited any measurable changes in the radial velocities of the emission components, from which it …

Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.