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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1989

Which stars have planets?

The question of predicting which stars have planetary systems is discussed, with special attention given to the work of Nakano (1988), who combined scaling arguments with his theory (Nakano, 1987) of formation of planets in the solar system to estimate planetary growth rates around stars of various masses. It is argued that, in addition to stellar mass, the process of planet formation depends on other parameters, such as angular momentum and collisions. The existence of binary and multiple star systems of varying type demonstrates that angular momentum variations can play a crucial role, while the fact that the solar system has four giant planets and four terrestrial planets is considered to be due to the effects of random impacts and scatterings. It is concluded that, at present, the concept of determining what types of planetary systems are to be expected about stars of varying masses cannot be resolved.

Lissauer, J. J.↗

NASA NTRS1988

The formation of interstellar jets by the convergence of supersonic conical flows

The interaction of a stellar wind with a nonuniform environment leads, under the assumption of steady state, to the formation of an ovoidal cavity with acute ending tips. The stellar wind recollected by the walls of the cavity ends up being deposited at the tips. Here, it is shown that this focusing effect leads to the formation of a narrow cylindrical stream or 'jet' of reshocked stellar wind matter moving directly away from the star with a large velocity. A 'typical' T Tauri star may produce jets with densities of 1000-10,000/cu cm, velocities about 100 km/s, widths about 0.00001-0.001 pc over a length of 0.001-0.01 pc. The opening angles are 7 deg or less.

Canto, J.↗

NASA NTRS2011

Stellar Populations of Highly Magnified Lensed Galaxies Young Starburst at Z to Approximately 2

We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z = 170, MS1512-cB58 at z = 2.73, SGAS J152745.1+065219 at z = 2.76 and SGAS J12265L3+215220 at z = 2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions. We compare star formation rates as measured from the SED fit, the Ha and [O II] .(lambda)3727 emission lines, and the UV+IR bolometric luminosity where 24micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z approx. 2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses 3 - 7 x 10(exp 9) Stellar mass, young ages approx. 100 Myr, little dust content E(B - V)=0.10-0.25, and star formation rates around 20- 100 Stellar mass/y. Compared to typical values for the galaxy population at z approx. 2, this suggests we are looking at newly formed, starbursting systems that have only recently started the build-up of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z approx. 2. Subject headings: galaxies: high-redshift, strong gravitational lensing, infrared: galaxies

Wuyts, Eva↗

NASA NTRS1998

Searching for Planets Around other Stars

In this colloquim presentation, Professor of Astronomy, Geoffrey Marcy discusses the discovery of planets orbiting other stars. Using the Doppler shift caused by stellar wobble that is caused by nearby planetary mass, astronomers have been able to infer the existence of Jupiter-sized planets around other stars. Using a special spectrometer at Lick Observatory, the wobble of several stars have been traced over the years required to generate an accurate pattern required to infer the stellar wobble. Professor Marcy, discusses the findings of planets around 47 Ursae Majoris, 16 Cygni B, 51 Pegasus, and 56 Rho 1 Cne. In the case of 56 Rho 1 Cne the planet appears to be close to the star, within 1.5 astronomical units. The observations from the smaller Lick Observatory will be augmented by new observations from the larger telescope at the Kek observatory. This move will allow observations of smaller planets, as opposed to the massive planets thus far discovered. The astronomers also hope to observe smaller stars with the Kek data. Future spaceborne observations will allow the discovery of even smaller planets. A spaceborne interferometer is in the planning stages, and an even larger observatory, called the Terrestrial Planet Finder, is hoped for. Professor Marcy shows artists' renderings of two of the planets thus far discovered. He also briefly discusses planetary formation and shows slides of both observations from the Orion Nebula and models of stellar system formation.

Source record↗

NASA NTRS1982

Some key issues in isotopic anomalies - Astrophysical history and aggregation

Astrophysical history, particularly that period extending from stellar nucleosynthesis events to the formation of meteorites, is discussed as the key element for the understanding of isotopic anomalies in meteorites. The bulk homogeneity of the interstellar medium is considered, and it is argued that, despite the presence of spatial inhomogeneities due to different nucleosynthesis rates in different parts of the galaxy and supernova ejecta, a cosmic chemical memory of nucleosynthesis patterns, rather than an inhomogeneous injection, is the source of isotopic anomalies. According to this view, volatility patterns and some isotopic patterns are mapped onto a grain-size spectrum, and the FUN systematics may be explained by interstellar sputtering. Furthermore, meteoritic He and Ne abundances are inferred to be presolar, and the ubiquitous titanium isotopic anomalies are explained by processes of chemical fixation and condensation in varying environments.

Clayton, D. D.↗

NASA NTRS1987

The relation between star formation and active nuclei

Three questions relevant to the relation between an active nucleus and surrounding star formation are discussed. The infrared stellar CO absorption bands can be used to identify galaxies with large populations of young, massive stars and thus can identify strong starburst unambiguously, such as in NGC 6240, and can help identify composite active/starburst systems such as Arp 220. An active nucleus is probably not required for LINER spectral characteristics; dusty starburst galaxies, particularly if they are nearly edge-on, can produce LINER spectra through the shock heating of their interstellar media by supernovae combined with the obscuration of their nuclei in the optical. The Galactic Center would be an ideal laboratory for studying the interaction of starbursts and active nuclei, if both could be demonstrated to occur there. Failure to detect a cusp in the stellar distribution raises questions about the presence of an active nucleus, which should be answered by additional observations in the near future.

Rieke, G. H.↗

NASA NTRS1991

Radial velocity detection of extra-solar planetary systems

The goal of this program was to detect planetary systems in orbit around other stars through the ultra high precision measurement of the orbital motion of the star around the star-planet barycenter. The survey of 33 nearby solar-type stars is the essential first step in understanding the overall problem of planet formation. The program will accumulate the necessary statistics to determine the frequency of planet formation as a function of stellar mass, age, and composition.

Cochran, William D.↗

NASA NTRS1993

Low surface brightness galaxies

A program to investigate the properties of low surface brightness (LSB) galaxies involving surface photometry in U, B, V, R, I, and H-alpha, HI imaging with the Westerbork Synthesis Radio Telescope (WSRT) and the very large array (VLA) and spectrophotometry of H2 regions in LSB galaxies is underway. The goal is to verify the idea that LSB galaxies have low star formation rates because the local gas density falls below the critical density for star formation, and to study the stellar population and abundances in LSB galaxies. Such information should help understanding the evolutionary history of LSB galaxies. Some preliminary results are reported.

Vanderhulst, J. M.↗

NASA NTRS1994

ROSAT observations of quiescent low mass disk galaxies: No evidence of baryonic blow out

To test the hypothesis that galactic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT Position Sensitive Proportional Counter (PSPC) observations of three such galaxies. The sensitivity of the PSPC to the presence of an extended, approximately 0.15 KEV halo of 10(exp 9) solar mass of gas, is quite high for the exposure times we used. We failed to detect this halo in all three cases and the observed x-ray luminosity of the galaxy is two orders of magnitude less than the hypothetical case in which the mass of gas that has been expelled by previous generations of star formation is equal to the stellar mass of the galaxy itself. This limit is much less than the actual mass of cold gas in these galaxies. Thus, we were unable to verify directly the presence of significant galactic winds in these three galaxies either because they are not operative, because their halos are not sufficiently massive to aid in the retention of this gas, or because the amount of injected gas is just a small percentage of the cold disk gas. If the latter reason is emblematic of low mass galaxies then we would not expect the detection of halos. We also report here the serendipitous detection of Abell 1560, a distance class 7 cluster of unknown redshift.

Bothun, Gregory D.↗

NASA NTRS2001

Clump Giants in the Hyades

This report covers the NASA grant NAG5-9986 for the cycle 1 XMM Guest Observer Program. The project is entitled "Clump Giants in the Hyades." This observation of one of the late-type Hyades giants has implications for understanding the formation of late-type stellar coronae as a function of the evolutionary state of the star. As of the call for this report, the data had been obtained by the satellite, but not delivered to the PI until 2001 August 7. Thus the progress can only be described as preparation for the data to arrive. To this end the PI and Co-Is are working on spectral analysis tools for the X-ray band. The PI has attended two workshops this summer in which results on late-type stellar coronae were presented, including XMM results from GTO team members, one entitled "Stellar Coronae in the Era of Chandra and XMM-Newton" at ESTEC in Noordwijk, and the "Cool Stars Workshop" in Boulder, Colorado.

Brickhouse, N.↗

NASA NTRS2003

Clump Giants in the Hyades

The project is entitled 'Clump Giants in the Hyades.' This observation of one of the late-type Hyades giants (Gamma Tau) has implications for understanding the formation of late-type stellar coronae as a function of the evolutionary state of the star. The Hyades giants are interesting because they are all clump giants in the Helium burning phase, similar to the cool primary of Capella. The Hyades giants show significantly more magnetic activity than expected from their state of evolution (and slowed-down rotation). Thus these systems provide an important clue to dynamo action. The data were obtained by the satellite on 13 March 2001 for a total RGS exposure of 58220 seconds. These data were delivered to the PI on 7 August 2001. The data could not be reprocessed until SAS Version 5.3.3 which became available 7 June 2002. Although the guidelines for assessing background rates suggested that half the data were contaminated, it does not appear that the spectral region of the RGS was adversely affected by unusually high background. The spectra show strong lines of Fe XVII and XVIII, O VII and VIII, Ne IX and X, along with numerous weaker lines. The emission measure distribution is highly reminiscent of Capella; if anything, the emission measure distribution is steeper at 6 million K than for Capella. Gamma Tau is the second brightest of the Hyades clump giants. Pallavicini et al. have shown that the luminosity of the brightest Hyades giant (Theta Tau) is remarkably similar to its luminosity as measured by Einstein. Short-term variability is also modest. We are addressing the variability issue now for Gamma Tau. Initial results were reported at the 2003 Seattle AAS meeting. A paper is in preparation for submission to the Astrophysical Journal.

Mushotzky, Richard F.↗

NASA NTRS2002

Requirements analysis for a multi-spacecraft flight system

The StarLight mission scheduled to launch June 2006, will demonstrate the separated spacecraft technologies of formation flying, precision formation, estimation, and long baseline stellar interferometry.

StarLight systems engineering requirements↗

NASA NTRS2012

Servicing Mission 4 and the Extraordinary Science of the Hubble Space Telescope

Just two years ago, NASA astronauts performed a challenging and flawless final Space Shuttle servicing mission to the orbiting Hubble Space Telescope. With science instruments repaired on board and two new ones installed, the observatory. is more powerful now than ever before. I will show the dramatic highlights of the servicing mission and present some of the early scientific results from the refurbished telescope. Its high sensitivity and multi-wavelength capabilities are revealing the highest redshift galaxies ever seen, as well as details of the cosmic web of intergalactic medium, large scale structure formation, solar system bodies, and stellar evolution. Enlightening studies of dark matter, dark energy, and exoplanet atmospheres add to the profound contributions to astrophysics that are being made with Hubble, setting a critical stage for future observatories such as the James Webb Space Telescope.

Wiseman, Jennifer J.↗

NASA NTRS2013

The Host Galaxies of Type Ia Supernovae Discovered by the Palomar Transient Factory

We present spectroscopic observations of the host galaxies of 82 low-redshift type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF). We determine star-formation rates, gas-phase stellar metallicities, and stellar masses and ages of these objects. As expected, strong correlations between the SN Ia light-curve width (stretch) and the host age mass metallicity are found: fainter, faster-declining events tend to be hosted by older massive metal-rich galaxies. There is some evidence that redder SNe Ia explode in higher metallicity galaxies, but we found no relation between the SN colour and host galaxy extinction based on the Balmer decrement, suggesting that the colour variation of these SNe does not primarily arise from this source. SNe Ia in higher-mass metallicity galaxies also appear brighter after stretch colour corrections than their counterparts in lower mass hosts, and the stronger correlation is with gas-phase metallicity suggesting this may be the more important variable. We also compared the host stellar mass distribution to that in galaxy targeted SN surveys and the high-redshift untargeted Supernova Legacy Survey (SNLS). SNLS has many more low mass galaxies, while the targeted searches have fewer. This can be explained by an evolution in the galaxy stellar mass function, coupled with a SN delay-time distribution proportional to t1. Finally, we found no significant difference in the mass--metallicity relation of our SN Ia hosts compared to field galaxies, suggesting any metallicity effect on the SN Ia rate is small.

host↗

NASA NTRS2016

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel, X-ray data from NuSTAR, Swift, Suzaku, and Chandra, and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1-1000 micron luminosity of 5.5 × 10(exp 46) ergs/s and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 10(exp 46) ergs/s and a viewing angle and half-opening angle both of approximately 36deg from pole-on. The starburst has a star formation rate of (110 +/- 34) Stellar Mass/yr and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Gamma approx. =l 1.8 and a line-of-sight column density of N(sub H) approx. = 5 × 10(exp 23) sq cm. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N(sub H) and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L(sub bol) approx.(0.5-2.5) ×10(exp 47) ergs/s. The X-ray and infrared data are further consistent with co-aligned AGN obscurers in which the line of sight "skims" the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.

galaxies: evolution â€“ galaxies: individual ( IRA↗

NASA NTRS2020

Host Galaxies of Type Ic and Broad-lined Type Ic Supernovae from the Palomar Transient Factory: Implications for Jet Production

Unlike ordinary supernovae (SNe), some of which are hydrogen and helium deficient (called Type Ic SNe), broadlined Type Ic SNe (SNe Ic-bl) are very energetic events, and only SNe Ic-bl are coincident with long-duration gamma-ray bursts (GRBs). Understanding the progenitors of SN Ic-bl explosions versus those of their SNIc cousins is key to understanding the SN–GRB relationship and jet production in massive stars. Here we present the largest existing set of host galaxy spectra of 28 SNe Ic and 14 SNe Ic-bl, all discovered by the same galaxy untargeted survey, namely, the Palomar Transient Factory (PTF). We carefully measure their gas-phase metallicities, stellar masses (M*), and star formation rates (SFRs). We further reanalyze the hosts of 10 literature SN–GRBs using the same methods and compare them to our PTF SN hosts with the goal of constraining their progenitors from their local environments. We find that the metallicities, SFRs, and M* values of our PTF SN Ic-bl hosts are statistically comparable to those of SN–GRBs but significantly lower than those of the PTF SNe Ic. The mass–metallicity relations as defined by the SNe Ic-bl and SN–GRBs are not significantly different from the same relations as defined by Sloan Digital Sky Survey galaxies, contradicting claims by earlier works. Our findings point toward low metallicity as a crucial ingredient for SN Ic-bl and SN–GRB production since we are able to break the degeneracy between high SFR and low metallicity. We suggest that the PTF SNe Ic-bl may have produced jets that were choked inside the star or were able to break out of the star as unseen low-luminosity or off-axis GRBs.

Maryam Modjaz↗

NASA NTRS1984

Stellar populations in local group dwarf elliptical galaxies. II - NGC 205

NGC 205, a dwarf elliptical companion of M31, was studied using deep CCD photometry on the VRI system. Consideration is given to a comparison between the giant branch and the Galactic globular clusters, the degree of chemical enrichment in the outer parts of NGC 204, and the setting of constraints on the stellar population of NGC 205. Should the distance of the galaxy be that of M31, this field's stellar population is extremely old. If star formation in NGC 205 is a recurring phenomenon, it is confined to the interior of the galaxy. Should the stellar population of NGC 205 be as old as Galactic globular clusters, its distance modulus is 24.3 + or - 0.2. The giant branch location corresponds to a mean metallicity greater than or equal to -0.9 + or - 0.2, and a metallicity dispersion is determined to be sigma greater than or equal to 0.5 dex. Also noted is that the color distribution at a given luminosity appears to be positively skewed.

Mould, J.↗

NASA NTRS1990

Multi-waveband observations of colliding galaxies

Colliding galaxies represent a major challenge to both theorists and observers because of the large variety of phenomena which are expected to come into play during the interaction. Strong gravitational fluctuations may drive non-linear waves and instabilities throughout the stars and gas leading to enhanced star formation, nuclear activity and ultimately a mixing of the morphological components of the original galaxies. One relatively uncomplicated class of colliding galaxy where stellar waves play an important role in star formation are ring galaxies. Ring galaxies are probably formed when a companion galaxy passes through the center of a disk system driving circular waves through the disk (Lynds and Toomre 1976, Toomre 1978, Struck-Marcell 1990). Off-center collisions can generate non-circular waves and can be loosely described as banana-shaped although they may exhibit more complex forms as the waves expand into the disk. The propagation of such stellar and gaseous waves through the disk leads to enhanced star formation (e.g., Appleton and Struck-Marcell 1987a; Jeske 1986) and provides a unique probe of the response of the interstellar medium (ISM) to a propagating wave (see Appleton and Struck-Marcell 1987b). Here, the authors report results for 3 systems; the irregular ring Arp 143 (=VV 117); Wakamatsu's Seyfert ring (A0959-755; see Wakamatsu and Nishida 1987) and the brighter member of the pair of ring galaxies comprising of AM 1358-221. The most complete multi-wavelength data is for Arp 143. Optical charge coupled device (CCD) observations made with the 60 inch Palomar telescope at BV and r band, near-IR images at J (1.25 microns), H (1.65 microns) and k (2.2 microns) bands from the infrared camera (IRCAM) InSb array camera on the 3.8m United Kingdon Infrared Telescope (UKIRT) telescope and very large array (VLA) observations at 20cm in both the neutral hydrogen line and radio continuum are described. The observations of Wakamatsu's ring and AM 1358 were made only in the near-IR, and a comparison is made with available optical plate material.

Appleton, P. N.↗