Observations of nonmagnetic CP stars Glenn M Wahlgren

Observations of non-magnetic CP stars Glenn M. Wahlgren Lund Observatory IAU Symposium No. 224 The A-Star Puzzle

B 2 B 5 B 7 B 9. 5/A 0 Hg. Mn A 2/A 3 -- hot Am -- Am He-weak He-strong Bp IAU Symposium No. 224 The A-Star Puzzle Ap

He-w Bp Hg. Mn Bp Hot Am Ap IAU Symposium No. 224 The A-Star Puzzle Am Ap

Topics in nm. CP star research – One Decade Ago • Basic properties (colors, fluxes, temperatures, classification) • Binarity (statistics) • Spectrum analysis (element abundances, isotopes) Extensions to UV (IUE, HST) Rumblings about stratification • Magnetic fields (presence in nm. CP stars) • Variability (photometric, spectroscopic) • New wavelength regimes X-ray: late-type B stars IAU Symposium No. 224 The A-Star Puzzle

New wavelength regime : far ultraviolet (FUSE) HD 108662 Bp HD 182308 B 9 p Hg. Mn HD 36981 B 5 V IAU Symposium No. 224 The A-Star Puzzle

IAU Symposium No. 224 The A-Star Puzzle

Binarity / multiplicity among nm. CP stars Companions continue to be identified, > 60% (Hubrig & Mathys 1996) Hg. Mn stars have a high presence in SB 2 systems Am stars have a high presence in binaries Companions with Teff < 10000 K are Am stars (? )(Ryabchikova et al. 1998) Main sequence B, A stars as companions to Cepheids (Evans 1995), with implications for ages and onset of CP phenomenon SU Cyg system: A (Cepheid) + (B (Hg. Mn) +C), Orb. Per. 549. 16, 4. 67 d (Wahlgren & Evans 1998) T Mon system: A (Cepheid) + (B(Bp) + C), C implied from velocities (Evans et al. 1999) AW Per system: A (Cepheid) + (B(B 8 V) +C), C implied from mass function (Evans et al. 2000) X-rays appear to originate from cool companions of late-B stars IAU Symposium No. 224 The A-Star Puzzle

Elemental abundances Categories of abundance analyses: Am stars: Studies favor the observation of stellar clusters for determining the onset and development of peculiarity with age. The basic picture of the Am abundance pattern has not changed. Hg. Mn stars: Studies focus on individual stars for specific tasks, such as isotope analysis, the study of a specific element(s) in several stars, or the abundance distribution of a particular star. Progress has been made in including more elements into the abundance pattern and in identifying new phenomena from the spectra. IAU Symposium No. 224 The A-Star Puzzle

Elemental abundance distribution for c Lupi A (Hg. Mn) The heaviest stable elements ( 73 _< Z _< 83 ) (But what does this mean ? ) IAU Symposium No. 224 The A-Star Puzzle

Abundance analyses: lessons learned The influence of velocity fields on line profiles. A 1 m V A 0 IV B 9 Hg. Mn B 9. 5 V B 9 Hg. Mn a) Am stars: strong lines show asymmetry, with deeper blue line wings (Landstreet 1998). A 1 m V A 2 m A 5 m b) Hg. Mn stars: turbulent velocity influences both the derived abundance and isotope composition of Hg in sharp-lined stars (Dolk et al. 2003). figure from Landstreet (1998) IAU Symposium No. 224 The A-Star Puzzle

Isotope anomalies Previous knowledge pertained to He, Pt, Hg New observations extended to include: Ca (Castelli & Hubrig 2004) wavelength shifts of Ca II IR triplet interpreted as anomalous isotope composition in Hg. Mn stars Ga (Nielsen et al. 2000, & Ph. D thesis 2002) mention of possible wavelength shift of Ga II lines in Hg. Mn star k Cancri Pt (several studies of Hg. Mn stars) variability among lines Hg (several studies of Hg. Mn stars) q-parameter found to be untenable at high spectral resolution heaviest isotopes most prominent isotopic composition not a constant for different lines of Hg II Pb (Leckrone et al. 1999) tentative claim to an anomaly, based on one Pb III line in Hg. Mn star c Lupi. Tl (Leckrone et al. 1996) wavelength shift of Tl II 1908Å indicative of only heavier isotope present in Hg. Mn star c Lupi IAU Symposium No. 224 The A-Star Puzzle

Weak emission lines in the He-weak star 3 Cen A Multiplet 13 WEL first detected in CP stars 3 Cen A (He-w) and 46 Aql (Hg. Mn) (Sigut et al. 2000). Later expanded to identify 350 lines in 3 Cen A (Wahlgren & Hubrig 2004). Lines identified originate from highexcitation energy levels in singlyionized atoms. Elements identified: P, Si, Ca, Cr, Mn, Fe, Co, Ni, Cu, Hg Multiplet 11 IAU Symposium No. 224 The A-Star Puzzle

Weak emission lines in Hg. Mn stars Mn-rich Mn-normal (Wahlgren & Hubrig 2000) WEL present in all main sequence mid to late B stars. Implications for element segregation in upper atmosphere. IAU Symposium No. 224 The A-Star Puzzle

Spectrum variability of the Hg. Mn star a And Hg II 3984Å line shows continuous variations with a period of 2. 38 d (rotation). Less pronounced variability detected in lines Hg II 6149, 5677, as well as other lines, but need to be addressed in terms of binary component (96. 88 d period). DI techniques show that the line profile variability can be explained as an inhomogeneous distribution of mercury, with higher concentrations occurring along the rotational equator. Does the Hg surface distribution have a magnetic origin ? ? ? IAU Symposium No. 224 The A-Star Puzzle Adelman et al. (2002) Ilyin (2000) Ryabchikova et al. (1999) Wahlgren et al. (2002)

Magnetic fields in nm. CP stars The potential for complex magnetic fields has been suggested through observations of the desaturation of magnetically sensitive line pairs in Hg. Mn and Am stars. Mathys & Lanz (1990): o Peg (A 1 m) Lanz & Mathys (1993): HD 29173 (Am), HD 195479 A (Am) Mathys & Hubrig (1995): 74 Aqr A (Hg. Mn), c Lupi B (A 2 m) Hubrig et al. (1999, 2001): several Hg. Mn stars Also, see catalogue of Bychkov et al. (2003). However, no fields are detected via the longitudinal Zeeman effect, implying no field structures similar to magnetic Ap stars. (Shorlin et al. 2002). But can there be other evidence ? (abundances of certain ions (Pr III)) IAU Symposium No. 224 The A-Star Puzzle

Stratification in Hg. Mn stars Stratification has been suggested based upon: -Ionization anomalies -Abundance trends of Cr II lines in the wing of Hb - He line profiles Concerns: -Treatment of depth dependent turbulence -Mixing data of different quality (ex. IUE and optical) IAU Symposium No. 224 The A-Star Puzzle figure from Nielsen (2002)

Crossing Boundaries: Hg. Mn – Am stars Deficiency for all Teff Ex: He, C, N, O Enhancement for all Teff Ex: Nd, Pr, Ce, Ba, Sr, (V, Fe) figures from Dolk (2002, Ph. D Thesis) IAU Symposium No. 224 The A-Star Puzzle

Crossing Boundaries: Hg. Mn – Am stars Trend for abundance to decrease as Teff decreases Ex: Ni, Al, S Trend for abundance to increase as Teff increases Ex: Mn, P, Ca, Sc, Ti, Y, Zr figures from Dolk (2002, Ph. D thesis) IAU Symposium No. 224 The A-Star Puzzle

Crossing Boundaries: Hg. Mn – Am stars X - Hg. Mn O - Am figure from Adelman et al. (2003) IAU Symposium No. 224 The A-Star Puzzle