We present updated orbital elements for the Wolf–Rayet (WR) binary WR 140 (HD 193793; WC7pd + O5.5fc). The new orbital elements were derived using previously published measurements along with 160 new ...radial velocity measurements across the 2016 periastron passage of WR 140. Additionally, four new measurements of the orbital astrometry were collected with the CHARA Array. With these measurements, we derive stellar masses of M(WR)=10.31±0.45Mꙩ and M(O)=29.27±1.14Mꙩ. We also include a discussion of the evolutionary history of this system from the Binary Population and Spectral Synthesis model grid to show that this WR star likely formed primarily through mass-loss in the stellar winds, with only a moderate amount of mass lost or transferred through binary interactions.
Using the Zwicky Transient Facility alert stream, we are conducting a large spectroscopic campaign to construct a complete, volume-limited sample of transients brighter than 20 mag, and coincident ...within 100″ of galaxies in the Census of the Local Universe catalog. We describe the experiment design and spectroscopic completeness from the first 16 months of operations, which have classified 754 supernovae. We present results from a systematic search for calcium-rich gap transients in the sample of 22 low-luminosity (peak absolute magnitude M > −17), hydrogen-poor events found in the experiment. We report the detection of eight new events, and constrain their volumetric rate to 15% 5% of the SN Ia rate. Combining this sample with 10 previously known events, we find a likely continuum of spectroscopic properties ranging from events with SN Ia-like features (Ca-Ia objects) to those with SN Ib/c-like features (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations distinguished by their red (g − r 1.5 mag) or green ( mag) colors at the r-band peak, wherein redder events show strong line blanketing features and slower light curves (similar to Ca-Ia objects), weaker He lines, and lower Ca ii/O i in the nebular phase. We find that all together the spectroscopic continuum, volumetric rates, and striking old environments are consistent with the explosive burning of He shells on low-mass white dwarfs. We suggest that Ca-Ia and red Ca-Ib/c objects arise from the double detonation of He shells, while green Ca-Ib/c objects are consistent with low-efficiency burning scenarios like detonations in low-density shells or deflagrations.
ABSTRACT
The bright and understudied classical Be star HD 6226 has exhibited multiple outbursts in the last several years during which the star grew a viscous decretion disc. We analyse 659 optical ...spectra of the system collected from 2017 to 2020, along with a ultraviolet spectrum from the Hubble Space Telescope and high cadence photometry from both Transiting Exoplanet Survey Satellite (TESS) and the Kilodegree Extremely Little Telescope (KELT) survey. We find that the star has a spectral type of B2.5IIIe, with a rotation rate of 74 per cent of critical. The star is nearly pole-on with an inclination of 13${_{.}^{\circ}}$4. We confirm the spectroscopic pulsational properties previously reported, and report on three photometric oscillations from KELT photometry. The outbursting behaviour is studied with equivalent width measurements of H α and H β, and the variations in both of these can be quantitatively explained with two frequencies through a Fourier analysis. One of the frequencies for the emission outbursts is equal to the difference between two photometric oscillations, linking these pulsation modes to the mass ejection mechanism for some outbursts. During the TESS observation time period of 2019 October 7 to 2019 November 2, the star was building a disc. With a large data set of H α and H β spectroscopy, we are able to determine the time-scales of dissipation in both of these lines, similar to past work on Be stars that has been done with optical photometry. HD 6226 is an ideal target with which to study the Be disc-evolution given its apparent periodic nature, allowing for targeted observations with other facilities in the future.
In early 2009, immediately following the end of the WR140 periastron campaign (see these proceedings), I turned my telescope back to epsilon Aurigae in time for the start of the eclipse. As well as ...being an interesting object in its own right, the Pro-Am campaign being run on epsilon Aurigae during the current eclipse is a good example of how amateur spectroscopists can make a useful contribution. epsilon Aurigae is a naked eye magnitude 3 star and was first noted to be variable by Johan Frisch in 1821. It was subsequently found to be an eclipsing binary with a period of 27.1 years which undergoes an approximately 2 year long flat-bottomed eclipse with approximately 0.8 magnitude drop in V.
Variations in the equivalent width of the neutral potassium line at 7699A are reported, during ingress and into totality of the current eclipse of the enigmatic eclipsing binary epsilon Aurigae. The ...increase and plateaus of line strength are correlated with new system parameters and interferometric imaging constraints, plus ancillary data being reported contemporaneously. Together, these data reveal structural details of the transiting disc, never before measured. Measured ring and gap placements do not immediately fit any proposed model using simple tidal estimation. However, we predict egress times of interest and urge continued monitoring of this star during the balance of its eclipse, and encourage theoretical treatment of the disc substructure to be pursued.
We present updated orbital elements for the Wolf-Rayet (WR) binary WR\,140 (HD\,193793; WC7pd + O5.5fc). The new orbital elements were derived using previously published measurements along with ...{\color{black}160} new radial velocity measurements across the 2016 periastron passage of WR 140. Additionally, four new measurements of the orbital astrometry were collected with the CHARA Array. With these measurements, we derive stellar masses of \(M_{\rm WR} = 10.31\pm0.45 M_\odot\) and \(M_{\rm O} = 29.27\pm1.14 M_{\odot}\). We also include a discussion of the evolutionary history of this system from the Binary Population and Spectral Synthesis (BPASS) model grid to show that this WR star likely formed primarily through mass loss in the stellar winds, with only a moderate amount of mass lost or transferred through binary interactions.
The bright and understudied classical Be star HD 6226 has exhibited multiple outbursts in the last several years during which the star grew a viscous decretion disk. We analyze 659 optical spectra of ...the system collected from 2017-2020, along with a UV spectrum from the Hubble Space Telescope and high cadence photometry from both TESS and the KELT survey. We find that the star has a spectral type of B2.5IIIe, with a rotation rate of 74% of critical. The star is nearly pole-on with an inclination of \(13.4\) degree. We confirm the spectroscopic pulsational properties previously reported, and report on three photometric oscillations from KELT photometry. The outbursting behavior is studied with equivalent width measurements of H\(\alpha\) and H\(\beta\), and the variations in both of these can be quantitatively explained with two frequencies through a Fourier analysis. One of the frequencies for the emission outbursts is equal to the difference between two photometric oscillations, linking these pulsation modes to the mass ejection mechanism for some outbursts. During the TESS observation time period of 2019 October 7 to 2019 November 2, the star was building a disk. With a large dataset of H\(\alpha\) and H\(\beta\) spectroscopy, we are able to determine the timescales of dissipation in both of these lines, similar to past work on Be stars that has been done with optical photometry. HD 6226 is an ideal target with which to study the Be disk-evolution given its apparent periodic nature, allowing for targeted observations with other facilities in the future.
We present preliminary results of a 4-month campaign carried out in the framework of the Mons project, where time-resolved Hα observations are used to study the wind and circumstellar properties of a ...number of OB stars.
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