department of physics and astronomy phd recruitment day – 31 st jan 2007 the unidentified fuv...
DESCRIPTION
PhD Recruitment Day – 31 st Jan 2007 Solutions for the DO line problem 1.Unidentified lines belong to high ionisation/ excitation species not included in the spectral line lists. 2.Unidentified lines belong to iron group and post iron group species not included in the spectral line lists. 3.Unidentified lines belong to a species wholly unexpected to be present in the DO. IntroductionTRANSCRIPT
DEPARTMENT OF PHYSICS AND ASTRONOMY
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
The unidentified FUV lines of hydrogen deficient dwarfs
David BoyceDavid BoyceM. A. Barstow, J. K. BarstowM. A. Barstow, J. K. Barstow
F. James, R. Laird, P. DobbieF. James, R. Laird, P. DobbieA. Forbes, J. Aston, B. BoolesA. Forbes, J. Aston, B. Booles
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
The unsolved problem of EUV The unsolved problem of EUV deficiencydeficiency
DO white dwarfs are significantly EUV deficientDO white dwarfs are significantly EUV deficient To reduce the predicted EUV flux, without increasing the assumed elemental To reduce the predicted EUV flux, without increasing the assumed elemental
abundances above the values determined from IUE and HST spectra, it is abundances above the values determined from IUE and HST spectra, it is necessary to find an alternative source of photospheric opacity.necessary to find an alternative source of photospheric opacity.
A possible source could be from additional, as yet undetected elements that are A possible source could be from additional, as yet undetected elements that are not currently included in the theoretical model calculations. not currently included in the theoretical model calculations.
The DO line problemThe DO line problem The FUV spectra of DO white dwarfs contain more unidentified lines than The FUV spectra of DO white dwarfs contain more unidentified lines than
identified ones.identified ones. The result of incomplete and inaccurate atomic data?The result of incomplete and inaccurate atomic data?
Introduction
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Solutions for the DO line problemSolutions for the DO line problem
1.1. Unidentified lines belong to high ionisation/ excitation species not included in Unidentified lines belong to high ionisation/ excitation species not included in the spectral line lists.the spectral line lists.
2.2. Unidentified lines belong to iron group and post iron group species not Unidentified lines belong to iron group and post iron group species not included in the spectral line lists.included in the spectral line lists.
3.3. Unidentified lines belong to a species wholly unexpected to be present in the Unidentified lines belong to a species wholly unexpected to be present in the DO.DO.
Introduction
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Processing and candidate selectionProcessing and candidate selection
All hydrogen deficient dwarfs were obtained from MAST and processed in the usual way (Barstow et al All hydrogen deficient dwarfs were obtained from MAST and processed in the usual way (Barstow et al
2003).2003).
The data has been calibrated using the calfuse pipeline version 2.0.5 or later, resulting in several spectra (covering different wavelength segments) per FUSE exposure. The exposures for each segment are then co-added, weighting each according to exposure time, and finally the segments are combined, weighted by their signal-to-noise ratio, to produce a single spectrum
Stars badly effected by molecular hydrogen were thrown out
Data reduction
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
A two component mysteryA two component mystery
1.1. The ISM contributes a complex The ISM contributes a complex and poorly understood and poorly understood component to the DO spectra.component to the DO spectra.
2.2. This component is not exactly This component is not exactly the same as in the more the same as in the more familiar DA spectrafamiliar DA spectra
3.3. How many of the unidentified How many of the unidentified lines that were previously lines that were previously thought to be photospheric thought to be photospheric originate in fact from the ISM?originate in fact from the ISM?
Introduction
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Velocity discrimination; the basic Velocity discrimination; the basic ideaidea
Line velocity
Average photospheric velocity
Average ISM velocity
Star
1St
ar 1
Star
2
Star
2
Star
1
Line position
Star
2
Star
2
Velocity Discrimination
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Velocity discrimination; real starsVelocity discrimination; real stars From well known lines we know an average velocity for the star and the ISM in that direction
Pho
tosp
heric
ISM
Pho
tosp
heric
ISM
Line=photospheric
Pho
tosp
heric
ISM
Line=ISM
Graph of predicted lab wavelength
Using multiple stars we can differentiate between an unknown line being Photospheric or ISM without even knowing what it is.
vcc
0
Velocity Discrimination
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Velocity Velocity discrimination; the discrimination; the
resultsresults1.1. Velocity discrimination clearly Velocity discrimination clearly
separates ISM lines from separates ISM lines from photospheric linesphotospheric lines
2.2. Origin of lines found without Origin of lines found without knowing line identityknowing line identity
Velocity Discrimination
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
A side note about O A side note about O VIVI
O VI in FUV spectra of white dwarfs considered O VI in FUV spectra of white dwarfs considered to be tracers of hot gas in the interstellar to be tracers of hot gas in the interstellar mediummedium
Since the distance to white dwarfs puts them Since the distance to white dwarfs puts them just inside, on or just outside the “hot local just inside, on or just outside the “hot local bubble” we can test the origin of the O VI using bubble” we can test the origin of the O VI using velocity discrimination.velocity discrimination.
Our results show that all O VI detected along Our results show that all O VI detected along the lines of sights of stars within the local the lines of sights of stars within the local bubble had O VI of a stellar origin.bubble had O VI of a stellar origin.
The hot local bubble = The cold The hot local bubble = The cold local bubble local bubble
Velocity Discrimination
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Finding the photospheric velocityFinding the photospheric velocityFrom a large sample ofFrom a large sample ofidentified lines an averageidentified lines an averagephotospheric velocity canphotospheric velocity canbe calculated.be calculated.
Lines common to DOs and Lines common to DOs and DAs can be used for thisDAs can be used for this
However Hot DOs and However Hot DOs and PG1159 stars are a problemPG1159 stars are a problemdue to the lack of linesdue to the lack of linescommon to DAs common to DAs
Makes velocity discriminationMakes velocity discriminationharderharder
Finding the photospheric velocity for DOs
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
A new approach to finding the A new approach to finding the photospheric velocity photospheric velocity
933.378 N III -5.7767
933.384 S VI -7.7007
933.383 Ni VI -7.38
933.383 Ni VI -7.38
933.265 Co V 30.458
933.5 Co V -44.897
1031.91 O VI -9.2815
1031.72 Ni VI 46.1173
1031.72 Ni Vi 46.1173
1031.8 Ni VI 24.0738
1031.87 Co V 2.32037
1031.92 Fe II -12.472
Velocity Velocity
Finding the photospheric velocity for DOs
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Recurrent velocity analysis; DA starsRecurrent velocity analysis; DA starsUsing the Morton line list we Using the Morton line list we observe in the DA that there observe in the DA that there
is is peaks at the ISM andpeaks at the ISM andphotospheric velocityphotospheric velocity
Changing to the Kurucz line Changing to the Kurucz line listlist
Increases the recurrence of Increases the recurrence of The photospheric velocityThe photospheric velocity
Kurucz more complete for Kurucz more complete for higher ionisations higher ionisations
Finding the photospheric velocity for DOs
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Recurrent velocity analysis; DO starsRecurrent velocity analysis; DO starsUsing either Morton or Using either Morton or
Kurucz Kurucz We do not retrieve the We do not retrieve the photospheric velocity.photospheric velocity.
The unidentified lines thatThe unidentified lines thatmake up DOs and PG1159 make up DOs and PG1159
stars stars are not in the Morton or the are not in the Morton or the Kurucz line list. Kurucz line list.
No amount of looking will No amount of looking will solve solve
The DO line problem.The DO line problem.
Finding the photospheric velocity for DOs
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Results of velocity searchResults of velocity searchUsing these methods a photospheric velocity is found for a broad range of DOs and PG1159 stars
Using the photospheric velocity for DO line identification
Star name Photospheric velocity
Spectral type Temperature
PG1144+005 4.3 PG1159 150000K
PG1424+535 -15.7 Cool PG1159 110000K
PG1707+427 -40.1 Cool PG1159 85000K
WD0109+111 28.8 DO 75000K
WD1034+001 41.3 DO 100000K
WD1159-034 42.5 DO/PG1159 140000K
WD1202+608 -64 sDO (d degen) 58000K
WD0501-289 18.5 DO 70000K
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
High ionisation/excitation speciesHigh ionisation/excitation species
7/8
4/4
Generation of atomic data for high ionisation species is making progressGeneration of atomic data for high ionisation species is making progress
3/8
2/5
Some lines however not so well behavedSome lines however not so well behaved
Success rate
Using the photospheric velocity for DO line identification
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Post iron groupPost iron group
A considerable number of A considerable number of identifications of post iron group identifications of post iron group elements in the FUV spectra of elements in the FUV spectra of cool DOs have been put forward cool DOs have been put forward by Chayer et al 2005 by Chayer et al 2005
Do these lines appear in any of Do these lines appear in any of our stars?our stars?
Do these lines occupy the correct Do these lines occupy the correct velocity?velocity?
Chayer et al 2005Chayer et al 2005
Using the photospheric velocity for DO line identification
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
Post iron groupPost iron group
Species line Velocity? Photospheric?
As IV 946.5 Fail
As IV 953.3 Pass Fail
As IV 956.9 Fail
As IV 971.1 Fail
As IV 980.6 Fail
As IV 999.3 Pass Pass
As IV 1003.4 Fail
Using the photospheric velocity for DO line identification
Lines tested against photospheric velocity of starLines tested against photospheric velocity of star
Lines that fail the testLines that fail the test
Species Passes Total
As IV 1 7
As V 2 4
Se III 1 2
Se IV 0 7
Se V 0 2
Br VI 0 1
Sn IV 2 4
Te VI 1 2
I V 0 5
I VI 0 1
PhD Recruitment Day – 31PhD Recruitment Day – 31stst Jan 2007 Jan 2007
ConclusionsConclusions
Velocity discrimination allows us to identify ISM lines from Velocity discrimination allows us to identify ISM lines from photospheric linesphotospheric lines
Unknown lines not in linelistsUnknown lines not in linelists Post iron group species do not occur at detectable levels.Post iron group species do not occur at detectable levels. Velocity forms a powerful tool in testing line identitiesVelocity forms a powerful tool in testing line identities High excitation elements such as Ne VIII are the best High excitation elements such as Ne VIII are the best
candidates for the additional opacity required to solve the EUV candidates for the additional opacity required to solve the EUV deficit.deficit.