Engineering topics

Subasavage, John P.

Publications and source records attributed to Subasavage, John P..

10 records

DOE OSTI2021

The Coronal Line Spectrum of the Iron Nova V3666 Ophiuchi

Optical and infrared spectroscopy are presented for the classical nova V3666 Ophiuchi (Nova Ophiuchi 2018 No.3) from 11 months after its outburst. At that epoch, V3666 Oph displayed an [Fe x] λ0.6375 emission line stronger than Hα and nearly a factor of 3 larger, relative to Hα, than in any nova observed previously. The [Fe x] feature, with an equivalent width exceeding 1300 Å, was enormously strong relative to the continuum emission as well. V3666 Oph also reached a state of high excitation for an Fe ii type nova, displaying coronal lines of [Fe xi], [S ix], and [Ar x], and permitted features that can be identified with the C vi (8–7), (9–8), and (10–9) transitions. In addition to [Fe x] and [Fe xi], V3666 Oph also displayed bright lines of [Fe vii], indicating that the prominent iron features were not confined to a single or narrow range of ionization states. Modeling the emission line spectrum of V3666 Oph with the photoionization code Cloudy indicated that the bulk of the emission line gas was matter-bounded, severely reducing the amount of low ionization gas and resulting in coronal lines that were very strong in comparison to lines such as H i and He i, and the familiar low excitation forbidden lines of nitrogen and oxygen. Such matter-bounded regions are observationally rare in novae since they are both faint and short-lived, offering a plausible explanation for why [Fe x] λ0.6375 had not be seen at this strength previously.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2018

Speckle Interferometry of Red Dwarf Stars

We report high-resolution optical speckle observations of 336 M dwarfs, which results in 113 measurements of the relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the systems. We also present the earliest measurements of relative position for 17 others. We include orbits for six of the systems, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.156 ± 0.011 and 0.1175±0.0079 M{sub ⊙} for the A and B components, respectively. All six of these new calculated orbits have short periods (between five and 38 years) and hold the promise of deriving accurate masses in the near future. For many other pairs we can establish their nature as physical or chance alignment, depending on their relative motion. Of the 80 systems, 32 have calculated orbits, 25 others are physical pairs, four are optical pairs, and 19 are currently unknown.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

CCD Parallaxes for 309 Late-type Dwarfs and Subdwarfs

New, updated, and/or revised CCD parallaxes determined with the Strand Astrometric Reflector at the Naval Observatory Flagstaff Station are presented. Included are results for 309 late-type dwarf and subdwarf stars observed over the 30+ years that the program operated. For 124 of the stars, parallax determinations from other investigators have already appeared in the literature and we compare the different results. Also included here are new or updated VI photometry on the Johnson–Kron-Cousins system for all but a few of the faintest targets. Together with 2MASS JHK{sub s} near-infrared photometry, a sample of absolute magnitude versus color and color versus color diagrams are constructed. Because large proper motion was a prime criterion for targeting the stars, the majority turn out to be either M-type subdwarfs or late M-type dwarfs. The sample also includes 50 dwarf or subdwarf L-type stars, and four T dwarfs. Possible halo subdwarfs are identified in the sample based on tangential velocity, subluminosity, and spectral type. Residuals from the solutions for parallax and proper motion for several stars show evidence of astrometric perturbations.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

The Solar Neighborhood. XXXIX. Parallax Results from the CTIOPI and NOFS Programs: 50 New Members of the 25 parsec White Dwarf Sample

We present 114 trigonometric parallaxes for 107 nearby white dwarf (WD) systems from both the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI) and the U. S. Naval Observatory Flagstaff Station (NOFS) parallax programs. Of these, 76 parallaxes for 69 systems were measured by the CTIOPI program and 38 parallaxes for as many systems were measured by the NOFS program. A total of 50 systems are confirmed to be within the 25-pc horizon of interest. Coupled with a spectroscopic confirmation of a common proper-motion companion to a Hipparcos star within 25 pc as well as confirmation parallax determinations for two WD systems included in the recently released Tycho Gaia Astrometric Solution catalog, we add 53 new systems to the 25-pc WD sample—a 42% increase. Our sample presented here includes four strong candidate halo systems, a new metal-rich DAZ WD, a confirmation of a recently discovered nearby short-period ( P = 2.85 hr) double degenerate, a WD with a new astrometric perturbation (long period, unconstrained with our data), and a new triple system where the WD companion main-sequence star has an astrometric perturbation ( P ∼ 1.6 year).

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

UCAC4 nearby star survey: A search for our stellar neighbors

We use data from the U.S. Naval Observatory fourth CCD Astrograph Catalog (UCAC4) in combination with photometry from the AAVSO Photometric All-Sky Survey and Two Micron All-Sky Survey to identify stars within 25 pc of the Sun. A sample of nearby stars with accurate trigonometric parallaxes from the Research Consortium On Nearby Stars is used to generate a set of 16 new photometric color–M{sub K{sub s}} relations that provide distance estimates with uncertainties of 15%. This work expands the available suites of well-calibrated photometric distance relations that can be used to identify nearby stellar systems. The distance relations are used with quality cuts to extract an initial sample of stars from the UCAC4 estimated to be within 25 pc. Color, proper motion, and existing literature sources are then used to obtain a clean sample of red dwarfs, while limiting the amount of contamination from background giants, resulting in a sample of 1761 candidate nearby stars within 25 pc. Of these, 339 are new discoveries with no previously known published parallax or distance estimate, primarily with proper motions less than 0.2 arcsec yr{sup −1}. Five stars are estimated to be within 10 pc, with the nearest, TYC 3980 1081 1, with V=10.50 estimated to be at 5.9 pc. That several hundred new stars have been revealed so close to the Sun illustrates once again that there is considerable work yet to be done to map the solar neighborhood and that additional nearby stars are likely still to be discovered.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

The solar neighborhood. XXXIII. Parallax results from the CTIOPI 0.9 m program: trigonometric parallaxes of Nearby low-mass active and young systems

We present basic observational data and association membership analysis for 45 young and active low-mass stellar systems from the ongoing Research Consortium On Nearby Stars photometry and astrometry program at the Cerro Tololo Inter-American Observatory. Most of these systems have saturated X-ray emission (log (L{sub X} /L {sub bol}) > –3.5) based on X-ray fluxes from the ROSAT All-Sky Survey, and many are significantly more luminous than main-sequence stars of comparable color. We present parallaxes and proper motions, Johnson-Kron-Cousins VRI photometry, and multiplicity observations from the CTIOPI program on the CTIO 0.9 m telescope. To this we add low-resolution optical spectroscopy and line measurements from the CTIO 1.5 m telescope, and interferometric binary measurements from the Hubble Space Telescope Fine Guidance Sensors. We also incorporate data from published sources: JHK{sub S} photometry from the Two Micron All Sky Survey point source catalog, X-ray data from the ROSAT All-Sky Survey, and radial velocities from literature sources. Within the sample of 45 systems, we identify 21 candidate low-mass pre-main-sequence members of nearby associations, including members of β Pictoris, TW Hydrae, Argus, AB Doradus, two ambiguous ≈30 Myr old systems, and one object that may be a member of the Ursa Major moving group. Of the 21 candidate young systems, 14 are newly identified as a result of this work, and six of those are within 25 pc of the Sun.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

The solar neighborhood. XXXI. Discovery of an unusual red+white dwarf binary at ∼25 pc via astrometry and UV imaging

We report the discovery of a nearby M5.0V dwarf at 24.6 pc, SCR 1848–6855, that is orbited by an unusual companion causing an astrometric perturbation of more than 200 mas. This is by far the largest perturbation found to date among more than 700 targets observed during our long-term astrometry/photometry program at the CTIO 0.9 m telescope. We present here a suite of astrometric, photometric, and spectroscopic observations of this high proper motion (∼1.''3 yr{sup –1}) system in an effort to reveal the nature of this unusual binary. The measured near-UV and optical U band fluxes exceed those expected for comparable M5.0V stars, and excess flux is also detected in the spectral range 4000-7000 Å. The elusive companion has been detected in HST-STIS+MAMA images at 1820 Å and 2700 Å, and our analysis shows that it is probably a rare, cool, white dwarf with T = 4600-5500 K. Given the long-term astrometric coverage, the prospects for an accurate mass determination are excellent, although as yet we can only provide limits on the unusual companion's mass.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

The binary white dwarf LHS 3236

The white dwarf LHS 3236 (WD1639+153) is shown to be a double-degenerate binary, with each component having a high mass. Astrometry at the U.S. Naval Observatory gives a parallax and distance of 30.86 ± 0.25 pc and a tangential velocity of 98 km s{sup –1}, and reveals binary orbital motion. The orbital parameters are determined from astrometry of the photocenter over more than three orbits of the 4.0 yr period. High-resolution imaging at the Keck Observatory resolves the pair with a separation of 31 and 124 mas at two epochs. Optical and near-IR photometry give a set of possible binary components. Consistency of all data indicates that the binary is a pair of DA stars with temperatures near 8000 and 7400 K and with masses of 0.93 and 0.91 M {sub ☉}; also possible is a DA primary and a helium DC secondary with temperatures near 8800 and 6000 K and with masses of 0.98 and 0.69 M {sub ☉}. In either case, the cooling ages of the stars are ∼3 Gyr and the total ages are <4 Gyr. The combined mass of the binary (1.66-1.84 M {sub ☉}) is well above the Chandrasekhar limit; however, the timescale for coalescence is long.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

The solar neighborhood. XXX. Fomalhaut C

LP 876-10 is a nearby active M4 dwarf in Aquarius at a distance of 7.6 pc. The star is a new addition to the 10 pc census, with a parallax measured via the REsearch Consortium On Nearby Stars (RECONS) astrometric survey on the Small and Moderate Aperture Research Telescope System's 0.9 m telescope. We demonstrate that the astrometry, radial velocity, and photometric data for LP 876-10 are consistent with the star being a third bound stellar component to the Fomalhaut multiple system, despite the star lying nearly 6° away from Fomalhaut A in the sky. The three-dimensional separation of LP 876-10 from Fomalhaut is only 0.77 ± 0.01 pc, and 0.987 ± 0.006 pc from TW PsA (Fomalhaut B), well within the estimated tidal radius of the Fomalhaut system (1.9 pc). LP 876-10 shares the motion of Fomalhaut within ∼1 km s{sup –1}, and we estimate an interloper probability of ∼10{sup –5}. Neither our echelle spectroscopy nor astrometry are able to confirm the close companion to LP 876-10 reported in the Washington Double Star Catalog (WSI 138). We argue that the Castor Moving Group to which the Fomalhaut system purportedly belongs, is likely to be a dynamical stream, and hence membership to the group does not provide useful age constraints for group members. LP 876-10 (Fomalhaut C) has now risen from obscurity to become a rare example of a field M dwarf with well-constrained age (440 ± 40 Myr) and metallicity. Besides harboring a debris disk system and candidate planet, Fomalhaut now has two of the widest known stellar companions.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2011

The Solar Neighborhood. XXV. Discovery of New Proper Motion Stars with 0.40 sec/yr > mu > or = 0.18 sec/yr Between Declinations -47 deg and 00 deg

We present 2817 new southern proper motion systems with 0.40 sec/yr > mu > or = 0.18 sec/yr and declination between 47 deg and 00 deg. This is a continuation of the SuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky. We use the same photometric relations as previous searches to provide distance estimates based on the assumption that the objects are single main-sequence stars. We find 79 new red dwarf systems predicted to be within 25 pc, including a few new components of previously known systems. Two systems--SCR 1731-2452 at 9.5 pc and SCR 1746-3214 at 9.9 pc--are anticipated to be within 10 pc. We also find 23 new white dwarf (WD) candidates with distance estimates of 15-66 pc, as well as 360 new red subdwarf candidates. With this search, we complete the SCR sweep of the southern sky for stars with mu > or = 0.18 sec/yr and R(sub 59F) < or = 16.5, resulting in a total of 5042 objects in 4724 previously unreported proper motion systems. Here we provide selected comprehensive lists from our SCR proper motion search to date, including 152 red dwarf systems estimated to be within 25 pc (9 within 10 pc), 46 WDs (10 within 25 pc), and 598 subdwarf candidates. The results of this search suggest that there are more nearby systems to be found at fainter magnitudes and lower proper motion limits than those probed so far.

LOW MASS STARS↗