Leicester University Physics Department

Past Research

An artist's impression of the white dwarf/red dwarf binary RE J1629+781, painted by Paul Doherty for BBC's Sky at Night programme and later given by him to the Leicester X-ray Astronomy group.

An artist's impression of the white dwarf/red dwarf binary RE J1629+781, painted by Paul Doherty for BBC's Sky at Night programme and later given by him to the Leicester X-ray Astronomy group. This jpeg version of the original work was created by M.R.Burleigh.

Introduction:

During the 1990s, the ROSAT EUV/soft X-ray sky survey data underpinned the work carried out on white dwarfs, either in direct analysis of the broadband photometric observations or through follow-up studies of the newly discovered stars in the sample. Eventually, we published a large scale study of the optical and EUV properties of the white dwarfs in the survey ( Marsh et al 1997a, MNRAS and Marsh et al, 1997b, MNRAS ), which probably represents the final major exploitation of the resource in our area.

Following this, the emphasis of the work has shifted to the exploitation of spectroscopic observations from the Extreme Ultraviolet Explorer (EUVE), ORFEUS, IUE and HST. We gained a significant fraction of the observing time on EUVE and were very successful with our HST programmes. Although IUE was finally shut down in 1996, reprocessing of the data for the final archive yielded a significant improvment in data quality, allowing new science to be done. At the same time we continued to develop the white dwarf atmospheric models needed to interpret the observations.

One highlight of the 1997-1999 period was the availability of early release data from the Hipparcos project. Following the 1992 call for proposals, we requested the parallax measurements for a group of hot white dwarfs detected in the ROSAT survey. The unprecedented accuracy of the Hipparcos data allowed the first accurate measurements of white dwarf distances and, as a result, establishes the mass-radius relation empirically. Until then, few direct tests of the theoretical mass-radius relation had been possible.

Summaries of some past highlights of the white dwarf research are given below (before 2000).

• An EUV-selected sample of H-rich white dwarfs

• Helium and heavier elements in hot white dwarf atmospheres

• Hipparcos observations and the mass-radius relation

• Stellar Atmospheres

• The pre-cataclysmic system REJ0720-318

• The ionization of the local interstellar medium

• The Whole Earth Telescope Projec t

• The record breaking magnetic white dwarf REJ 0317-853

More Recent Research (2000-2003):

See also the posters entitled “Sirius-type binary stars” and “The record breaking magnetic white dwarf RE J 0317-853” available on our posters page.

SOUNDING ROCKETS AND INSTRUMENTATION

We are involved in the design and flight of the next generation of spacebourne EUV instrumentation. Known as J-PEX , this normal incidence spectrometer is being tested in a series of sounding rocket flights. You can read an overview of this program by clicking the link below.

• The Joint Astrophysical Plasmadynamic Experiment.

For more detail, go to the J-PEX Page

SIRIUS-TYPE BINARY SYSTEMS

The first white dwarf to be discovered, Sirius, is a (WD+MS) binary system. However, the majority of catalogued white dwarf stars are isolated objects. With around 65% of all stars being members of multiple systems, it is important that studies of white dwarfs include stars in binaries. Read about the importance of these systems here.

• Sirius-type Binary Systems

WHITE DWARF EVOLUTION

Our work at Leicester is aimed at understanding the nature and evolution of white dwarf stars. Spectroscopic observations from the Extreme Ultraviolet Explorer (EUVE), ORFEUS and the Hubble Space Telescope are providing us with important new scientific results, some of which are presented on the page below.

• White dwarf evolution

We use a wide variety of facilities, both ground and space based. A linked list is available here.

Use of PPARC and other facilities

A significant fraction of our research is based on studies using orbiting observatories operating in various parts of the Electromagnetic Spectrum. For links to more information on these select from the list below.

• ROSAT (Roentgen Satellit): X-ray and EUV

• EUVE (Extreme Ultraviolet Explorer): EUV

• IUE (International Ultraviolet Explorer): far-UV

• HST (Hubble Space Telescope): far-UV, optical and infra-red

• WET (Whole Earth Telescope): high speed optical photometry

• FUSE (Far Ultraviolet Spectroscopic Explorer)