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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

A Hubble Space Telescope Survey for Novae in M87. II. Snuffing out the Maximum Magnitude–Rate of Decline Relation for Novae as a Non-standard Candle, and a Prediction of the Existence of Ultrafast Novae

The extensive grid of numerical simulations of nova eruptions from the work of Yaron et al. first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are in the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10{sup −7}–10{sup −8} M {sub ⊙}, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. These same models predict the existence of ultrafast novae that display decline times, t {sub 2,} to be as short as five hours. We outline a strategy for their future detection.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

A Hubble Space Telescope survey for novae in M87.I. light and color curves, spatial distributions, and the nova rate

The Hubble Space Telescope has imaged the central part of M87 over a 10 week span, leading to the discovery of 32 classical novae (CNe) and nine fainter, likely very slow, and/or symbiotic novae. In this first paper of a series, we present the M87 nova finder charts, and the light and color curves of the novae. We demonstrate that the rise and decline times, and the colors of M87 novae are uncorrelated with each other and with position in the galaxy. The spatial distribution of the M87 novae follows the light of the galaxy, suggesting that novae accreted by M87 during cannibalistic episodes are well-mixed. Conservatively using only the 32 brightest CNe we derive a nova rate for M87: ${363}_{-45}^{+33}$ novae yr –1 . We also derive the luminosity-specific classical nova rate for this galaxy, which is ${7.88}_{-2.6}^{+2.3}\,{\mathrm{yr}}^{-1}/{10}^{10}\,{L}_{\odot }{,}_{K}$. Both rates are 3–4 times higher than those reported for M87 in the past, and similarly higher than those reported for all other galaxies. As a result, we suggest that most previous ground-based surveys for novae in external galaxies, including M87, miss most faint, fast novae, and almost all slow novae near the centers of galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1993

Models for various aspects of dwarf novae and nova-like stars

The first attempts to explain the nature of dwarf novae were based on the assumption of single-star phenomena, in which emission lines were assumed to be caused by circumstellar gas shells. The outburst behavior was tentatively ascribed to the kind of (also not understood) mechanism leading to nova outbursts. The realization that some, and possibly all, dwarf novae and nova-like stars (and novae) are binaries eventually led to models which bore more and more similarities to the modern interpretation on the basis of the Roche model. Not all cataclysmic variables are known binaries. In fact, with respect to the entire number of known objects, the proven binaries are still the minority, but all the brightest variables are in fact known to binaries. Not a single system is known which exhibits the usual characteristics of a cataclysmic variable and at the same time can be declared with certainty to be a single star. Two systems are known, the dwarf nova EY Cyg and the recurrent nova V1017 Sgr, in which, in spite of intensive search, no radial velocity variations have been found; but they still exhibit composite spectra consisting of a bright continuum, an emission spectrum, and a cool absorption spectrum. If the Roche model is correct, it is to be expected that a small percentage of objects is viewed pole-on, so orbital motions do not make themselves felt as Doppler shifts of spectral lines. So even these two systems support the hypothesis that all cataclysmic variables (with the possible exception of symbiotic stars) are binaries. In cataclysmic variables, it seems that the brightness changes observed in dwarf novae and nova-like stars in the optical and the UV are due directly to changes in the accretion disks. The study and understanding of accretion disks in these systems can bear potentially valuable consequences for many other fields in astronomy. The observed spectra of dwarf novae and nova-like stars comprise a fairly large range: pure emission spectra, pure absorption spectra, a mixture of both, asymmetric line profiles, very different slopes of the continuous flux distribution -- and one single system may exhibit all of these features at different times. Agreement and disagreement between computed and observed spectra should show whether or not the Roche model is applicable and where it probably will have to be modified and improved. Except for their outburst behavior and its immediate consequences, novae, dwarf novae, and nova-like stars cannot be physically distinguished from each other.

Ladous, Constanze↗
DOE OSTI2017

Common envelope ejection for a luminous red nova in M101

We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light curve showed two distinct peaks with absolute magnitudes M{sub r}⩽−12.4 and M{sub r}≃−12, on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of ≈3700 K and low expansion velocities (≈−300 km s{sup −1}) for the H i, Ca ii, Ba ii, and K i lines. From archival data spanning 15–8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L ∼ 8.7 × 10{sup 4} L{sub ⊙}, T{sub eff}≈7000 K, and an estimated mass of M1=18±1 M{sub ⊙}. This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5−10 M{sub ⊙}) and NGC 4490-OT (30 M{sub ⊙}).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1993

Classical novae and recurrent novae: General properties

We describe the observable characteristics of classical novae and recurrent novae obtained by different techniques (photometry, spectroscopy, and imaging) in all the available spectral ranges. We consider the three stages in the life of a nova: quiescence (pre- and post-outburst), outburst, final decline and nebular phase. We describe the photometric properties during the quiescent phase. We describe the photometric properties during outburst, the classification according the rate of decline (magnitudes per day), which permits us to define very fast, fast, intermediate, slow, and very slow novae and the correlation between luminosity and speed class. We report the scanty data on the spectra of the few known prenovae and those on the spectra of old novae and those of dwarf novae and nova-like, which, however, are almost undistinguishable. We describe the typical spectra appearing from the beginning of the outburst, just before maximum, up to the nebular phase and the correlation between spectral type at maximum, expansional velocity, and speed class of the nova. We report the existing infrared observations, which permit us to explain some of the characteristics of the outburst light curve, and give evidence of the formation of a dust shell in slow and intermediate novae (with the important exception of the very slow nova HR Del 1967) and its absence or quasi-absence in fast novae. The ultraviolet and X-ray observations are described. The X ray observations of novae, mainly from the two satellites EINSTEIN and EXOSAT, are reported. Observations of the final decline and of the envelopes appearing several months after outburst are also reported.

Hack, Margherita↗
DOE OSTI2017

A Hubble Space Telescope survey for novae in M87 – III. Are novae good standard candles 15 d after maximum brightness?

Ten weeks of daily imaging of the giant elliptical galaxy M87 with the Hubble Space Telescope (HST) has yielded 41 nova light curves of unprecedented quality for extragalactic cataclysmic variables. We have recently used these light curves to demonstrate that the observational scatter in the so-called maximum-magnitude rate of decline (MMRD) relation for classical novae is so large as to render the nova-MMRD useless as a standard candle. Here in this paper, we demonstrate that a modified Buscombe–de Vaucouleurs hypothesis, namely that novae with decline times t2 > 10 d converge to nearly the same absolute magnitude about two weeks after maximum light in a giant elliptical galaxy, is supported by our M87 nova data. For 13 novae with daily sampled light curves, well determined times of maximum light in both the F606W and F814W filters, and decline times t 2 > 10 d we find that M87 novae display M606W,15 = -6.37 ± 0.46 and M814W,15 = -6.11 ± 0.43. If very fast novae with decline times t 2 < 10 d are excluded, the distances to novae in elliptical galaxies with stellar binary populations similar to those of M87 should be determinable with 1σ accuracies of ± 20 percent with the above calibrations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Searching for Sterile Neutrinos In the NOvA Experiment and Measurements of Hadronic Energy Response with NOvA Test Beam Data

The NOvA (NuMI Off-Axis electron neutrino Appearance) experiment is a long-baseline neutrino oscillation experiment composed of two functionally identical detectors: a 300-ton Near Detector and a 14-kton Far Detector, separated by 809 km and placed 14 mrad off the axis of the NuMI neutrino beam created at Fermilab. This configuration enables NOvA’s rich neutrino physics program, which includes measuring neutrino mixing parameters, determining the neutrino mass hierarchy, probing CP violation in the leptonic sector, studying neutrino cross sections, searching for sterile neutrinos, and more.\\ In this thesis I will present two independent analyses developed within the NOvA experiment. The first is a search for light sterile neutrino oscillations in the 3+1 framework using $\nu_\mu$-CC and NC samples from the NOvA Near and Far Detectors. Light sterile neutrinos are hypothetical neutral leptons that do not participate in the weak interactions but can mix with the three known active neutrinos: $\nu_e$, $\nu_\mu$, and $\nu_\tau$. Anomalous results, such as $\nu_e$/$\bar{\nu}e$ appearance in a $\nu_\mu$ ($\bar{\nu}_\mu$) beam observed by the MiniBooNE and LSND experiments, can be explained by the existence of sterile neutrinos. Thus, proving the existence of this type of neutrino is essential. The latest results of these searches in the NOvA experiment, along with contributions to this effort, will be presented.\\ The second is the first measurement of the pion energy response using data from the NOvA Test Beam experiment. The NOvA Test Beam experiment, deployed at Fermilab, uses a scaled-down 30-ton NOvA detector to analyze tagged beamline particles. The beamline can select and identify electrons, muons, pions, kaons, and protons with momenta ranging from 0.4 to 1.4 GeV/c. Pions are an important component of the hadronic system in neutrino interactions, and understanding how the detector responds to these particles is crucial for the validation of the simulation and the reduction of detector calibration uncertainties, which remain one of the largest systematic uncertainties in NOvA analyses.

Dueñas Tonguino, David Francisco [Cincinnati U.] (↗
NASA NTRS1990

NOVA 201 ultrasonic thickness gage (NOVA Gage)

The measurement integrity of the NOVA 201 digital ultrasonic thickness gage (NOVA gage) was demonstrated by comparing the NOVA gage measurements to the thickness gage measurements, and determining the bias and uncertainty of the NOVA gage when measuring redesigned solid rocket motor (RSRM) hardware per engineering test plans (ETP). The NOVA gage was tested by three different operators on steel and aluminum RSRM hardware for wall thickness. The results show that the measurement bias is not consistent. The uncertainty of the bias is caused by the heterogeneous material properties of the RSRM components that influence the time of flight of ultrasonic waves. The measurement uncertainty inherent to the design and operation of the NOVA gage is less in comparison to the uncertainty of the bias. The total measurement uncertainty cannot be substantially reduced by taking more than one measurement. There is no correlation between bias and the surface finish range of this test unless 3-in-One oil is used as a couplant, in which case there appears to be a slight trend. There is no correlation between uncertainty and the surface finish range. The measurement uncertainty of the NOVA gage can be reduced using 3-in-One oil as a couplant.

Garecht, Diane↗
NASA NTRS1993

Nova V2214 Ophiuchi 1988 - A magnetic nova inside the period gap

The discovery of a coherent photometric modulation in Nova Oph 1988 with period 0.117515 +/- 0.000002 d, which is associated with the orbital period of the underlying binary, is reported. On the basis of photometric observations, it is concluded that Nova V2214 Oph 1988 is a magnetic nova with an orbital period inside the period gap. The inclusion of this system in the statistics of novae suggests that there is no period gap for novae and that there is a clear correlation between the occurrence of novae with short orbital periods and the presence of magnetic white dwarfs. It is suggested that funneling of the accretion flow onto the magnetic poles favors the conditions for a thermonuclear runaway, increasing the frequency of eruptions for magnetic systems.

Baptista, R.↗
NASA NTRS2012

The Radio Light Curve of the Gamma-Ray Nova in V407 CYG: Thermal Emission from the Ionized Symbiotic Envelope, Devoured from Within by the Nova Blast

We present multi-frequency radio observations of the 2010 nova event in the symbiotic binary V407 Cygni, obtained with the Karl G. Jansky Very Large Array (VLA) and spanning 1.45 GHz and 17.770 days following discovery. This nova.the first ever detected in gamma rays.shows a radio light curve dominated by the wind of the Mira giant companion, rather than the nova ejecta themselves. The radio luminosity grewas the wind became increasingly ionized by the nova outburst, and faded as the wind was violently heated from within by the nova shock. This study marks the first time that this physical mechanism has been shown to dominate the radio light curve of an astrophysical transient. We do not observe a thermal signature from the nova ejecta or synchrotron emission from the shock, due to the fact that these components were hidden behind the absorbing screen of the Mira wind. We estimate a mass-loss rate for the Mira wind of .Mw approximately equals 10(exp -6) Solar mass yr(exp -1). We also present the only radio detection of V407 Cyg before the 2010 nova, gleaned from unpublished 1993 archival VLA data, which shows that the radio luminosity of the Mira wind varies by a factor of 20 even in quiescence. Although V407 Cyg likely hosts a massive accreting white dwarf, making it a candidate progenitor system for a Type Ia supernova, the dense and radially continuous circumbinary material surrounding V407 Cyg is inconsistent with observational constraints on the environments of most Type Ia supernovae.

Chomiuk, Laura↗
DOE OSTI2017

Measurement of key resonance states for the P 30 ( p , γ ) S 31 reaction rate, and the production of intermediate-mass elements in nova explosions

We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the P-30(p, gamma)S-31 reaction critical for determining the production of intermediate-mass elements up to Ca in nova ejecta. The P-30(d,n)S-31 reaction was studied in inverse kinematics using the GRETINA gamma-ray array to measure the angle-integrated cross-sections of states above the proton threshold. In general, negative parity states are found to be most strongly produced but the absolute values of spectroscopic factors are typically an order of magnitude lower than predicted by the shell-model calculations employing WBP Hamiltonian for the negative-parity states. The results clearly indicate the dominance of a single 3/2(-) resonance state at 196 keV in the region of nova burning T approximate to 0.10-0.17 GM, well within the region of interest for nova nucleosynthesis. Hydrodynamic simulations of nova explosions have been performed to demonstrate the effect on the composition of nova ejecta.

Kankainen, A. (ORCID:0000000310827602)↗
NASA NTRS1978

Nova Ophiuchi 1977 - An X-ray nova

This letter reports the observation by the HEAO 1 satellite experiments of the X-ray nova in Ophiuchus discovered by Kaluzienski and Holt (1977), which is designated H1705-25. The SAO/MIT scanning modulation collimator has been used in conjunction with the NRL large-area sky survey to give two possible positions for the X-ray nova, each having errors of 0.3 by 1.8 arcmin. The discovery of a 16.5-magnitude optical nova (Nova Ophiuchi 1977) in one of the error boxes is reported, and the X-ray source is identified with the optical nova. The object is classified as being of the A0620-00 and A1524-61 type; i.e., a low-mass binary system.

Griffiths, R. E.↗
NASA NTRS1990

Nova LMC 1990 no. 2: The first extragalactic recurrent nova

International Ultraviolet Explorer (IUE) observations of Nova LMC (Large Magellanic Cloud) 1990 number 2 are presented. It is the first recurrent nova to be observed outside the Galaxy. Earlier optical outburst of the nova was observed in 1968, when it reached a maximum of about V = 10.2. The first observations caught the nova at UV maximum, and IUE spectra were obtained between 16 Feb. and 26 Mar. 1990, with 8 hour resolution during the first day of observations. No P Cyg profiles developed on the resonance lines, suggesting that very little mass was ejected and that the outburst was not spherical. The integrated UV luminosity was then 3.4 x 10(exp 38) erg/s which is above the Eddington limit for a one solar mass white dwarf (assuming E (B - V) = 0.15 and a distance of 55 kpc to the LMC). This is the first time that the luminosity of a recurrent nova has been directly obtained.

Shore, Steven N.↗
NASA NTRS1986

First optical candidate for a recovered classical nova in a globular cluster - Nova 1938 in M14

U, B, V, R, and H-alpha CCD frames of the field of the nova which appeared in the globular cluster M14 in 1938 have been compared with the nova discovery images. On the basis of positional coincidence, brightness, and blue color, a candidate nova was identified and its right ascension and declination to within 1 arcsec each. Confirmation of the candidate and detailed study of the quiescent nova will probably require Hubble Space Telescope observations.

Shara, Michael M.↗
NASA NTRS1990

A statistical analysis of IUE spectra of dwarf novae and nova-like stars

First results of a statistical analysis of the IUE International Ultraviolet Explorer archive on dwarf novae and nova like stars are presented. The archive contains approximately 2000 low resolution spectra of somewhat over 100 dwarf novae and nova like stars. Many of these were looked at individually, but so far the collective information content of this set of data has not been explored. The first results of work are reported.

Ladous, Constanze↗
NASA NTRS1990

Nova LMC 1990 no. 1: The first extragalactic neon nova

International Ultraviolet Explorer (IUE) observations of nova LMC (Large Magellanic Cloud) 1990 No. 1, the first neon (or ONeMg) nova observed outside the Galaxy are presented. The observations were obtained from 17 Jan. to Mar. 1990, with especially dense coverage during the first 25 days of the outburst. (The neon nova categorization is based on the detection of forbidden Ne 3-4 lines in optical spectra; the ultraviolet neon lines were not detected.) During the first 30 days of the outburst, the radiative losses were dominated by the N 5 delta 1240 and C 4 delta 1550 lines. The maximum ejection velocity was approximately 8000 km/s, based on the blue absorption edge of the C 4 P-Cygni profile. Early in the outburst of Nova LMC 1990 No. 1 the UV luminosity alone was approximately 3 times 10 to the 38th power erg/sec, implying that the bolometric luminosity was well in excess of the Eddington luminosity for a one solar mass object.

Sonneborn, George↗
NASA NTRS1994

On the decay of outbursts in dwarf novae nad X-ray novae

We perform computations using a time-dependent model for the accretion disk limit-cycle mechanism to examine the decay of the optical light following the peak of a dwarf nova outburst. We present the results of a parameter study of the physical input variables which affect the decay rate. In the model, the decay is brought about by a cooling transition front which begins at large radii in the disk and moves inward. The nature of the decay is strongly influenced by the radial dependence of the accretion disk viscosity parameter alpha. To obtain exponential decays for typical dwarf nova parameters, we require alpha proportional to r(exp epsilon(sub 0)), where epsilon(sub 0) approximately = 0.3-0.4. The exact value of epsilon(sub 0) which produces exponential decays depends on factors such as the mass of the accreting star and the inner radius of the accretion disk. Therefore, the observed ubiquity of exponential decays in two different types of systems (dwarf novae and X-ray novae) leads us to believe that alpha is an unnatural scaling for the viscosity. The physics of the cooling transition front must be self-regulating in that the timescale (-parital derivative of lnSigma(r)/partial derivative +)(exp -1) (where Sigma is the surface density) for mass extraction across the front remains constant. This may be consistent with a scaling alpha proportional to (h/r)(exp n), where h is the local disk semi-thickness and n approximately 1-2. As regards the speed of the cooling front, we find v(sub F)(r) proportional to r(exp p), where p approximately 3 at large radii, with an abrupt transition to p approximately 0 at some smaller radius. The r(exp 3) dependence is much steeper than has been found by previous workers and appears to result from the strong variation of specific heat within the cooling front when the front resides at a large radius in the disk. The outflow of disk material across the cooling front causes a significant departure of dln T(sub dff0/dln r from the standard value of -0.75 (expected from steady state accretion) within about 0.2 dex in radius of the break associated with the cooling front -- T(sub eff) aproximately 10(exp 3.9) K (r/10(exp 10 cm)) (exp -0.1). These effects should be observable with eclipse mapping. Finally, it appears that the relatively slow decay rate for the optical flux in the 1975 outburst of A0620-00 can be accounted for if the primary is a approximately 10 Solar mass black hole.

Cannizzo, John K.↗
DOE OSTI2016

ORIGINS OF ABSORPTION SYSTEMS OF CLASSICAL NOVA V2659 CYG (NOVA CYG 2014)

We report on high-dispersion spectroscopy results of a classical nova V2659 Cyg (Nova Cyg 2014) that are taken 33.05 days after the V -band maximum. The spectrum shows two distinct blueshifted absorption systems originating from H i, Fe ii, Ca ii, etc. The radial velocities of the absorption systems are −620 km s{sup −1}, and −1100 to −1500 km s{sup −1}. The higher velocity component corresponds to the P-Cygni absorption features frequently observed in low-resolution spectra. Much larger numbers of absorption lines are identified at the lower velocity. These mainly originate from neutral or singly ionized Fe-peak elements (Fe i, Ti ii, Cr ii, etc.). Based on the results of our spectroscopic observations, we discuss the structure of the ejecta of V2659 Cyg. We conclude that the low- and high-velocity components are likely to be produced by the outflow wind and the ballistic nova ejecta, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗