Engineering Papers⌕ Search

Engineering topics

Honeycutt, R. K.

Publications and source records attributed to Honeycutt, R. K..

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

The 1991-2012 light curve of the old nova HR Lyrae

The 22 yr light curve of HR Lyr, acquired with a typical cadence of 2-6 days, is examined for periodic and quasi-periodic variations. No persistent periodicities are revealed. Rather, the light curve variations often take the form of nearly linear rises and falls having typical e-folding times of about 100 days. Occasional ∼0.6 mag outbursts are also seen, with properties similar to those of small outbursts found in some nova-like cataclysmic variables. When the photometry is formed into yearly averages, a decline of 0.012 ± 0.005 mag yr{sup –1} is apparent, consistent with the fading of irradiation-induced M-dot following the nova. The equivalent width of Hα is tabulated at three epochs over the interval 1986-2008 in order to compare with a recent result for DK Lac in which Hα was found to be fading 50 yr after the nova. However, our results for such a fading in HR Lyr are inconclusive.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The long-term light curve of the cataclysmic variable V794 Aquilae

The 1990-2012 light curve of the nova-like (NL) cataclysmic variable V794 Aql is studied in order to characterize and better understand the transitions to and from the faint state, and the variations within the bright state. Investigations of earlier portions of this data had concluded that the transitions to the low state were much slower than the rapid recovery, giving a sawtoothed appearance to the light curve. This behavior differs from that of most other VY Scl stars, which led to an interpretation of the large amplitude sawtooths as being due to an accretion disk (AD) instability. However, more recent photometry strongly suggests that the bright state itself has transitions of 1-1.5 mag, and that earlier studies had intermixed these bright state variations with the transitions to the low state. These newly recognized variations within the bright state sometimes appear as small outbursts (OBs) with typical amplitudes of 0.5-1.5 mag and spacings of ∼15-50 days. The rise times of the OBs are 2-3 times faster than the decline times. We argue that the V794 Aql bright state variations are due to AD behavior similar to that seen in dwarf novae, but with varying degrees of stability. Similar regular small OBs have also been reported in other NL CVs, which we compare with V794 Aql. The true deep low states in V794 Aql appear to be normal, having transition speeds and shapes very similar to the transitions in other VY Scl stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

WIND VARIABILITY IN BZ CAMELOPARDALIS

Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the H{alpha} line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted H{alpha} emission components in their BZ Cam spectra. We have attributed these emission components in H{alpha} to occasions when gas concentrations in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I {lambda}5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the wind due to the non-axisymmetric nature of the stream/disk interaction. Simultaneous photometry and spectroscopy were acquired on three nights in order to test the possible connection between flickering continuum light and the strength of the front-side wind. We found strong agreement on one night, some agreement on another, and no agreement on the third. We suggest that some flickering events lead to only back-side winds which will not have associated P-Cygni profiles.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

Spectroscopy and photometry of the dwarf nova BZ Ursae Majoris and the CV linewidth/K, mass-ratio relation

Time-resolved spectroscopy of the dwarf nova BZ Ursae Majoris (BZ UMa) reveals periodic velocity variations in the hydrogen emission lines with P = 97.9 +/- 0.1 min and K = 73 +/- 6 km/s. CCD photometry over a 16-month interval shows three outbursts of about 4 mag with a mean separation of 181 days. The mean full width at half maximum (FWHM) for the hydrogen beta emission is large, prompting a recalibration of the FWHM/K vs. mass ratio relation, giving a mass ratio (M(sub RD)/M(sub WD)) of 0.20 for BZ UMa. The short period, long outburst interval, and small mass ratio support the suggestion of BZ UMa being in the SU Ursae Majoris subclass of dwarf novae.

Jurcevic, J. S.↗
NASA NTRS1993

CP Puppis - No ordinary old nova

We present spectrophotometric data for the old nova CP Puppis (Nova Puppis 1942) that demonstrates the simultaneous existence of two distinct periods for the system. We find that the photometric period of 0.06834(7) day is 11 percent longer than the spectroscopic period. We also present Doppler tomographic images of CP Pup that indicate the existence of an accretion disk in the system. Finally, we interpret the observational evidence in terms of a DQ Herculis model and an SU Ursae Majoris model for CP Pup. While the evidence mildly supports both interpretations, it is insufficient for us to conclusively classify CP Pup as either a DQ Her system or an SU UMa system.

White, James C., II↗
NASA NTRS1992

MR Persei - A new rotating, spotted flare star

Spectroscopy and photometry are used to show that MR Persei, an object originally classified as a dwarf nova, is in fact a flare star. The automated CCD photometry consists of sequences of exposures within a single night as well as long-term photometry over a five-month interval. One sequence shows a 30-min flare, accompanied by post-flare 'dips'. A 0.2 mag variation with a period of about one-half day is also seen in this sequence. The long-term photometry is used to refine the period to 0.45483 d, which we attribute to the rotation of a spotted star. Evidence for membership of MR Per in the young Alpha Per cluster is considered, and found to be inconclusive.

Honeycutt, R. K.↗
NASA NTRS1991

Mass loss in the 96 day binary UU Cancri

A series of 16 high-dispersion spectra at H-alpha have been obtained for the tidally distorted K giant-containing long-period binary UU Cnc, in order to both study the K giant's Doppler profiles and search for the effects of accretion onto the second component. While Doppler profiles of the system for a semidetached configuration fit the observations very well, those for existing overcontact light-curve solutions all yield poorer fits. Although the H-alpha line is always stronger than those of the common giants, its equivalent width is consistent with a K4 II classification reflective of the star's 50 solar radius size. Emission wings in H-alpha are possible evidence for an accretion disk.

Eaton, Joel A.↗
NASA NTRS1985

Chromospheric activity and TiO bands in M giants

Low-resolution IUE spectra of 23 cool giant stars ranging from K3 through M6 have been used to examine chromospheric activity in late-type giants. Previous studies have suggested a decrease in the fractional flux, normalized to bolometric flux, of the Mg II resonance lines (an indicator of chromospheric activity) with effective temperature. Using more accurately determined effective temperatures, this decrease is confirmed and found to be more rapid than previously suggested. A strong correlation is found between relative TiO band strengths, as measured by the Wing TiO index, and the level of chromospheric activity, as measured by Mg II fluxes. Cool giants which have weak TiO bands relative to the mean TiO strengths for stars of similar color also have Mg II lines that are weaker than the mean. Changes in composition and in chromospheric activity as a consequence of aging are suggested as a possible origin of this interesting relation.

Steiman-Cameron, T. Y.↗
NASA NTRS1974

On the relation between carbon star spectral types and colors

Observations of 32 carbon stars are listed in a table, taking into account the spectral classes given by Yamashita (1966) and Richer (1971). The relations between spectral type and color for carbon stars appear consistent with the differences between Yamashita's and Richer's types if carbon star groups I-III lie on a decreasing boundary temperature sequence.

Honeycutt, R. K.↗
NASA NTRS1974

Scanner observations of carbon stars from 5000 to 7000 A

New photoelectric spectral scans of 26 N-type and 11 R-type carbon stars are presented. The spectral energy distributions were also measured to gain new insight into the composition, chemistry, and structure of carbon star atmospheres. Using the best continuum points in the wavelength region from 5000 to 7000 A a color index is defined, taking into account fluxes at 0.57 and 0.68 microns. The new color index correlates well with the widely used (V-R) broad-band color index.-

Fay, T. D., Jr.↗
NASA NTRS1973

Scanner observations of hot helium-carbon stars.

Photoelectric spectral scans at 20 A resolution of four hot helium-carbon-rich stars have been reduced to fluxes and are presented in graphical form. Similar flux curves for several normal (hydrogen-rich) stars in the same temperature range are presented for comparison.

Fay, T.↗
NASA NTRS1972

Scanner observations of cool stars from 3400 to 11,000 A.

Evaluation of photoelectric scans of the M supergiant alpha Ori and the carbon stars 19 Psc, W Ori, and DS Peg made at 20-A resolution from 3400 to 6000 A and at 40-A resolution from 6000 to 11,000 A. The data are corrected for atmospheric extinction and for the instrumental response to obtain plots of log flux per unit frequency interval versus wavelength. The dominant spectral features are due to C2, CN, and TiO; the variation of these features with spectral class is pointed out.

Fay, T.↗