X-ray Emission Line Profiles of Hot Stars David H. Cohen and Stanley P. Owocki Presented at “Two Years of Chandra Science” Washington, D.C., September
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Personality Types Measure I S A C E R Tie Total Males N 84 38 60 41 52 70 25 370 O bserved G PA M 3.25 3.25 3.23 2.98 3.13 3.10 3.35 3.18 SD .53 .42 .57 .63 .51 .47 .53 .53 ACT-Com posite M 23.80 22.26 23.13 23.05 22.81 22.71 22.28 23.00 SD 3.98 3.60 4.32 4.09 4.20 4.06 4.68 4.11 Adjusted G PA M 3.22 3.28 3.22 2.98 3.13 3.11 3.39 Females N 110 142 106 114 115 33 87 707 O bserved G PA M 3.30 3.38 3.48 3.24 3.21 3.35 3.27 3.32 SD .48 .50 .40 .56 .51 .48 .51 .50 ACT-Com posite M 22.90 21.80 23.18 21.97 21.10 22.79 21.53 22.10 SD 3.97 3.91 3.82 3.65 3.78 3.06 3.68 3.83 Adjusted G PA M 3.26 3.40 3.43 3.24 3.25 3.32 3.30 Examination of Holland’s Predictive Pattern Order Hypothesis for Academic Achievement William D. Beverly and Robert A. Horn Northern Arizona University, Educational Psychology, Flagstaff, AZ This study reexamined Holland’s assertion that higher educational achievement goes with the following primary personality order: I, S, A, C, E, R. Similar to prior research, mixed support emerged for Holland’s prediction. Current findings show a similar clustering of personality types when looking at GPA for males (see Table 5). That is, the top three types identified in the present study (I, S, A) match Holland’s prediction (I, S, A), but not with the same significance. The lowest three types identified in this study (E, R, C) are consistent with Holland’s lowest three (C, E, R). For females, A and S types clustered in the top three with R, and C and E types clustered in the lower three with I. Also shown in Table 5 are the rank orderings for males and females when looking at aptitude and at achievement controlling for aptitude. Similar clustering appears for this set of data, again providing limited support for Holland’s prediction. Similar to prior research, primary personality types appear to be a more valid predictor of academic achievement for males than for females. Holland’s model of career development is used in a number of applied settings, such as school guidance and counseling, and has been identified as the most popular model of counseling among elementary, middle, and high school counselors. Considering that this model is one of the most established guidance and counseling approaches used in academic settings, school counselors and other professionals should be aware that the evidence for Holland’s hypothesis regarding personality type and academic achievement is limited, and, at times, conflicting. A recommendation is for school counselors to use more than a student’s primary personality type to make any meaningful predictions. The more comprehensive and complete the personality profile, the more precise the explanatory power of the theory, as there is a more accurate understanding of the individual’s interests, traits, and preferences. Although Holland has proposed that there are six primary personality types, he also maintains that a three-letter code is a better estimate of an individual’s overall personality. Holland considers congruence, consistency, and differentiation central to his theory, and such variables can only be considered when using more than a primary Introduction Research Questions Methodology Results Discussion and Implications 1. Is Holland’s pattern order hypothesis supported when looking at academic major GPA? 2. Is Holland’s pattern order hypothesis for academic achievement supported when looking at aptitude? 3. Is Holland’s pattern order hypothesis supported when looking at Table 1 Observed GPA, ACT-Composite, and Adjusted GPA for Male and Female Primary Personality Types Participants A total of 1077 undergraduate students, consisting of 370 (34.4%) males and 707 (65.6%) females, comprised this study’s sample. Each of the six primary personality types was represented for males and females (see Table 1). Students were degree-seeking students at a mid-sized university who entered as first-time freshmen and subsequently earned a Bachelors degree. Procedures The participants’ primary Holland personality types were identified by determining each individual’s highest score obtained from the Entering Freshman ACT Assessment. Highest scores tied with one or more of the remaining five scores were categorized separately as tied. The participants’ ACT-Composite scores (aptitude) and academic major GPA (achievement) were obtained from official university records. Academic major GPA was chosen as our measure of academic achievement as it reflects coursework more consistent with a student’s expressed interest, and, as such, would be more congruent with one’s personality type. For males, looking at academic major GPA, the Holland personality types ranked as Tie, I, S, A, E, R, C, F(6, 363) = 2.30, p = .034, Partial 2 = .037. For females, the Holland personality types ranked as A, S, R, I, Tie, C, E, F(6, 700) = 3.86, p = .001, Partial 2 = .032. Post hoc multiple comparisons for males and females on academic major GPA are shown in Table 2. Table 2 Pairwise Comparisons for Males and Females Looking at Academic Major GPA Source p ES Males Tie (3.35)and R ealistic (3.10) .037 .49 Tie (3.35)and C onventional (2.98) .005 .72 Investigative (3.25)and C onventional (2.98) .006 .52 Social (3.25)and C onventional (2.98) .023 .52 Artistic (3.23)and C onventional (2.98) .020 .47 Females Artistic (3.48)and Investigative (3.30) .008 .36 Artistic (3.48)and Tie (3.27) .004 .41 Artistic (3.48)and C onventional (3.24) .000 .48 Artistic (3.48)and Enterprising (3.21) .000 .55 Social (3.38)and C onventional (3.24) .021 .29 Social (3.38)and Enterprising (3.21) .005 .36 For males, looking at ACT-Composite, the Holland personality types ranked as I, A, C, E, R, Tie, S, F(6, 363) = .95, p = .462, Partial 2 = .015. For females, the Holland personality types ranked as A, I, R, C, S, Tie, E, F(6, 700) = 4.31, p < .001, Partial 2 = .036. Post hoc multiple comparisons for females on ACT-Composite are shown in Table 3. Table 3 Pairwise Comparisons for Females Looking at ACT-Composite Source p ES Females Artistic (23.18)and C onventional (21.97) .017 .32 Artistic (23.18)and Social (21.80) .004 .37 Artistic (23.18)and Tie (21.53) .003 .44 Artistic (23.18)and Enterprising (21.10) .000 .55 Investigative (22.90)and Social (21.80) .022 .29 Investigative (22.90)and Tie (21.53) .012 .36 Investigative (22.90)and Enterprising (21.10) .000 .48 R ealistic (22.79)and Enterprising (21.10) .024 .45 For males, looking at academic major GPA controlling for ACT-Composite (aptitude), the Holland personality types ranked as Tie, S, A, I, E, R, C, F(6, 362) = 2.63, p = .017, Partial 2 = .042. For females, the Holland personality types ranked as A, S, R, Tie, I, E, C, F(6, 699) = 2.80, p = .011, Partial 2 = .023. Post hoc multiple comparisons for males and females on academic major GPA controlling for ACT-Composite are shown in Table 4. Source p ES Males Tie (3.39)and R ealistic (3.11) .017 .56 Tie (3.39)and Enterprising (3.13) .035 .52 Tie (3.39)and C onventional (2.98) .001 .84 Social (3.28)and C onventional (2.98) .006 .62 Artistic (3.22)and C onventional (2.98) .014 .50 Investigative (3.22)and C onventional (2.98) .011 .49 Females Artistic (3.43)and Investigative (3.26) .009 .36 Artistic (3.43)and Enterprising (3.25) .006 .38 Artistic (3.43)and C onventional (3.24) .004 .39 Social (3.40)and Investigative (3.26) .022 .29 Social (3.40)and Enterprising (3.25) .014 .36 Social (3.40)and C onventional (3.24) .009 .31 Table 4 Pairwise Comparisons for Males and Females Looking at Academic Major GPA Controlling for ACT-Composite Holland’s Hypothesis I S A C E R B/H G PA – M ales Tie I S A E R C B/H G PA – Fem ales A S R I Tie C E B/H AC T-C – M ales I A C E R Tie S B/H AC T-C – Fem ales A I R C S Tie E B/H Adjusted G PA – M ales Tie S A I E R C B/H Adjusted G PA – Fem ales A S R Tie I E C Table 5 Comparisons of Primary Personality Pattern Orders Holland proposed a personality theory which provides a parsimonious means of conceptualizing diverse aspects of vocational and personality development. His theory contends that individuals and environments can be characterized by their resemblance to one of six types: Realistic, Investigative, Artistic, Social, Enterprising, or Conventional (R, I, A, S, E, C, see Figure 1). Holland views individuals’ vocational and educational choices, preferences, behaviors, and achievements as a function of their personality. Holland’s theory proposes three diagnostic relationships (i.e., congruence, consistency, and differentiation) to assist professionals with their assessments of individuals; he predicts that greater degrees of congruence, consistency, and differentiation will be associated with greater stability, satisfaction, and achievement. When put into an educational perspective, this should equate to greater levels of retention and academic achievement for students. Holland hypothesized an ordering of the primary personality patterns in terms of educational behaviors, asserting that higher educational achievement goes with the following primary personality pattern order: I, S, A, C, E, R. This hypothesis has received limited empirical research with mixed results. However, Holland maintains that this order exists in educational behavior, reaffirming that educational achievement follows the pattern order: Investigative, Social, Artistic, Conventional, Enterprising, and Realistic. The limited and conflicting research on Holland’s hypothesis was the catalyst for this study. R ealistic Investigative C onventional Enterprising Social Artistic R ealistic Investigative C onventional Enterprising Social Artistic Figure 1 Holland’s Hexagonal Model
Presented at “Two Years of Chandra Science” Washington, D.C., September 5-7, 2001
In collaboration with
J. Elliot Reed (Swarthmore ‘03)
Geneviève de Messieres (Swarthmore ‘04)
Carolin Cardamone (Wellesley ‘02)
Asif Ud-Doula (University of Delaware)
Marc Gagne (West Chester University)
Joseph MacFarlane (Prism Computational Sciences)
Duane Liedahl (Lawrence Livermore National Lab)
Nathan Miller (University of Wisconsin, Madison)
Joseph Cassinelli (University of Wisconsin, Madison)
(Swarthmore College; University of Delaware)
Solar-type magnetic heating? Or massive stellar wind shock heating?
spectroscopy can provide crucial new insights into the fundamental nature of the X-ray emission from hot stars
Uniform emission from a constant velocity, spherical shell
Sum over series of shells to build up a model of a wind
Occultation by the star blocks the back (red) side of the wind
Continuum opacity in the cold part of the wind
X-ray line profiles for parameterized wind emission models
fx ~ 1/rq
for r > Ro
v ~ (1 R / r)
* Ý M
4 vR*
=1, 3 , 5, 10
Why might we expect a smoothly distributed source of X-rays above some minimum radius and embedded in a cold, opaque stellar wind?
The line-force instability -- caused by the feedback inherent in the Doppler de-shadowing of an optically thick, line-driven flow -- provides a natural explanation
But there are other models too
Shock heating of wind can produce X-rays…but perhaps not enough
So, we can test the models with the new, high-resolution spectra being obtained by Chandra
Zeta Pup, an O supergiant with a massive wind: The strong Ne X Ly alpha line can be fit by a model with reasonable wind-shock parameters (
*=1.5; R0=1.5; q=0.5; =0.8)
2vinf/FWHMinst~ 20
Ne X
Within the spectrum of zeta Pup, there are trends seen in the line shapes
The wind is less optically thick at shorter wavelengths;
The O VIII line’s breadth and relative flat-topped-ness indicates an origin in the outer wind
O VIIIMg XII
Four other hot stars have been observed with the Chandra HETGS:
1 Ori C (O7.5 V); Ori (O9.5 II); Ori (O9.5I); Sco (B0 V)
For none of these stars are the line profiles indicative of a smoothly and broadly distributed source within an optically thick wind
For zeta Ori, the lines are broad, but much more symmetrical and less blueshifted
This is the same model that fit the Ne X line in zeta Pup
There are several possibilities:
1. “Turbulence”
2. Line scattering
3. Non-isotropic clumping
4. Hybrid magnetic/wind-shock models (MCWS)
(1) Random motion of hot plasma, not embedded in a wind might explain Sco (and maybe Ori); but for the other stars, the FWHM exceeds the surface escape speed, and the shock temperatures associated with the line widths are huge; the extent of impulsive flare events required is unreasonable
What can lead to lines that are broad, but relatively unshifted and symmetric?
Thin vs. Thick line-emission
=1, 3 , 5, 10
cf. Ignace & Gayley 2001for=0 case
Line Opacity has a very different effect than continuum opacity
It tends to suppress the bluest and reddest photons; escape probabilities are largest for “sideways” trajectories out of Sobolev zones
This effect is most significant for a constant-velocity flow
Clumping can reduce continuum opacity in the wind
And non-isotropic clumping can also favor “sideways” escape, and thus suppression of the bluest and reddest photons, if the clumps are oblate
The Venetian Blind Model...
Zeta Puppis with Bo=400 G no radiative cooling
Initial after 2 days Zoom on final
Magnetically Confined Wind Shock (MCWS) Model
A dipole field plus a line-driven wind can generate a “magnetosphere” with a standing shock, and associated heating
Pup with Bo=2000 G
Zoom on densityDensityY- Velocity
-1000 vy (km/s) 1000
The Magnetically Confined Wind Shock model can
Redirect and confine the wind flow--if the magnetic field energy density exceeds the wind kinetic energy
But even if the magnetic energy density is less, the flow can be affected
This confinement can lead to strong shocks at the magnetic equator, heating gas that will be relatively stationary in the star’s frame
Conclusions
The prototypical O supergiant with a line-driven wind, z Pup, has X-ray line profiles consistent with optically thin line emission embedded in an optically thick wind -- the standard “wind shock model”
Later type O stars and early B stars have line profiles that are more symmetric and unshifted, and in some cases narrower
For magnetic hot stars, the MCWS model provides an intriguing possibility for explaining these profiles
