High-Speed Optical Spectroscopy

Marsh, T. R.

doi:10.1007/978-1-4020-6518-7_5

“…This makes it possible to observe time series of spectra with a negligible dead time of about 12ms between two frames. EMC-CDs are more efficient than conventional CCDs when the number of counts per pixel is smaller than the readout noise squared (Marsh 2008), which makes them particulary useful to observe faint targets at high cadence. They are therefore also known as Low Light Level CCDs (L3CCDs).…”

Section: Observationsmentioning

confidence: 99%

“…Therefore, the spectra were extracted along a 3rd order polynomial fit to the spectrum (trace) following Marsh (1989). Because the advantage of EMCCDs is largest when working at low count levels (Marsh 2008), the science spectra typically have low count levels. This prevents one from accurately fitting the trace of the curved spectra.…”

Section: Extraction and Calibration Of Curved Spectramentioning

confidence: 99%

Remarkable spectral variability on the spin period of the accreting white dwarf in V455 And

Bloemen

¹

,

Steeghs

²

,

Smedt

³

et al. 2013

Monthly Notices of the Royal Astronomical Society

Self Cite

View full text Add to dashboard Cite

We present spin-resolved spectroscopy of the accreting white dwarf binary V455 And. With a suggested spin period of only 67s, it has one of the fastest spinning white dwarfs known. To study the spectral variability on the spin period of the white dwarf, we observed V455 And with 2 s integration times, which is significantly shorter than the spin rate of the white dwarf. To achieve this cadence, we used the blue arm of the ISIS spectrograph at the 4.2-m William Herschel Telescope, equipped with an electron multiplying CCD (EMCCD). Strong coherent signals were detected in our time series, which lead to a robust determination of the spin period of the white dwarf (P spin = 67.619 ± 0.002 s). Folding the spectra on the white dwarf spin period uncovered very complex emission line variations in Hγ, He I λ4472 and He II λ4686. We attribute the observed spin phase dependence of the emission line shape to the presence of magnetically controlled accretion onto the white dwarf via accretion curtains, consistent with an intermediate polar type system. We are, however, not aware of any specific model that can quantitatively explain the complex velocity variations we detect in our observations. The orbital variations in the spectral lines indicate that the accretion disc of V455 And is rather structureless, contrary to the disc of the prototype of the intermediate polars, DQ Her. This work demonstrates the potential of electron multiplying CCDs to observe faint targets at high cadence, as readout noise would make such a study impossible with conventional CCDs.

show abstract

“…The instrumentation on SALT will also be developed further in the near future and promises research returns over a wide range of topics, from cosmological through stellar, to extra-solar planets. Its use in special niche observing (e.g., time-domain astrophysics -see Marsh (2007)) will ensure unique returns. A problem exists in lack of foresight to produce a generation of young astrophysicists ready to use the facilitya situation exacerbated by the trashing of the government research funding system that occurred at the beginning of this decade, which left university researchers stranded without a proper funding scheme.…”

Section: Discussionmentioning

confidence: 99%

Astrophysics in South Africa

Warner

¹

2008

Transactions of the Royal Society of South Africa

View full text Add to dashboard Cite

A brief overview is given of astrophysical research in South Africa in the past 30 years, highlighting some of the successes that have come from observations at optical, radio and gamma ray wavelengths. Many of these have been made possible by concentration on projects requiring large amounts of specialized observing time at good sites. These contributed to acceptance by the South African Government for funding of a major expansion of facilities. The world-class optical and radio instrumentation under construction will ensure opportunities for competitive research for decades to come.

show abstract

“…This makes it possible to observe time series of spectra with a negligible dead time of about 12ms between two frames. EMCCDs are more efficient than conventional CCDs when the number of counts per pixel is smaller than the readout noise squared (Marsh 2008), which makes them particulary useful to observe faint targets at high cadence. They are therefore also known as Low Light Level CCDs (L3CCDs).…”

Section: Observationsmentioning

confidence: 99%

Remarkable Spectral Variability on the Spin Period of the Accreting White Dwarf in V455 And

Bloemen¹

2014

High-Precision Studies of Compact Variable Stars

0

View full text Add to dashboard Cite

We present spin-resolved spectroscopy of the accreting white dwarf binary V455 And. With a suggested spin period of only 67s, it has one of the fastest spinning white dwarfs known. To study the spectral variability on the spin period of the white dwarf, we observed V455 And with 2 s integration times, which is significantly shorter than the spin rate of the white dwarf. To achieve this cadence, we used the blue arm of the ISIS spectrograph at the 4.2-m William Herschel Telescope, equipped with an electron multiplying CCD (EMCCD). Strong coherent signals were detected in our time series, which lead to a robust determination of the spin period of the white dwarf (P spin = 67.619 ± 0.002 s). Folding the spectra on the white dwarf spin period uncovered very complex emission line variations in Hγ, He I λ4472 and He II λ4686. We attribute the observed spin phase dependence of the emission line shape to the presence of magnetically controlled accretion onto the white dwarf via accretion curtains, consistent with an intermediate polar type system. We are, however, not aware of any specific model that can quantitatively explain the complex velocity variations we detect in our observations. The orbital variations in the spectral lines indicate that the accretion disc of V455 And is rather structureless, contrary to the disc of the prototype of the intermediate polars, DQ Her. This work demonstrates the potential of electron multiplying CCDs to observe faint targets at high cadence, as readout noise would make such a study impossible with conventional CCDs.

show abstract

High-Speed Optical Spectroscopy

Cited by 7 publications

References 44 publications

Remarkable spectral variability on the spin period of the accreting white dwarf in V455 And

Remarkable spectral variability on the spin period of the accreting white dwarf in V455 And

Astrophysics in South Africa

Remarkable Spectral Variability on the Spin Period of the Accreting White Dwarf in V455 And

Contact Info

Product

Resources

About