1. Element spots in HgMn stars
Heidi Korhonen
Centre for Star and Planet Formation
&
Niels Bohr Institute
University of Copenhagen

2. Outline General properties of HgMn stars
Some history of line profile variability detections
Chemical element surface configurations
Temporal evolution of chemical spots
Are HgMn stars magnetic?
Kochukhov et al. 2005

3. HgMn stars Late B-type stars
Extreme overabundance of Hg/Mn (not always Mn)
Slowly rotating: <v sin i>=29 km/s
No strong large-scale organized magnetic fields
No enhancement in Rare Earth Elements, but of heavy elements W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi
Anomalous isotopic abundances of He, Hg, Pt, Tl, Pb, Ca.
About 150 stars are known
Dolk et al. 2002
Ca-48 shift in HD (HR 7143)
Castelli & Hubrig (2004)

4. Multiplicity among HgMn stars
Observations of 57 HgMn stars with VLT
25 binaries,
3 triples,
1 quadruple
Nine companion candidates found for the first time
Only five stars in the sample show no indication of multiplicity, taking into account that 44 systems are confirmed or suspected spectroscopic binaries
Schöller et al 2010 4

5. Vertical stratificationHD
Some evidence for vertical stratification:
of Cr (Savanov & Hubrig 2001)
of Mn (Alecian 1982; Sigut 2001)
of Ga (Lanz et al. 1993)
From the Thiam et al. (2010) sample of four HgMn stars only HD shows stratification of Mn
Dubaj et al. (2004) found no conclusive evidence of stratification of Fe lines in HD A.
Makaganiuk et al. (2012) found no convincing evidence of vertical stratification of Ti and Y in HD11753 Ti Cr Mn
Thiam et al. 2010 Fe

6. From Kurtz & Martinez 2000

7. Indications of spots on HgMn star: α And
Ryabchikova et al. (1999) did chemical abundance analysis of α And
They discovered changing line profiles of Hg at 3983 Å.
But they only had three epochs of observations.

8. Detection of spots on HgMn star: α And
„This first definitively identified spectrum variation in any
mercury-manganese star is not due to the orbital motion
of the companion. Rather, the variation is produced by
the combination of the day period of rotation of
the primary that we determined and a nonuniform surface
distribution of mercury that is concentrated in its equatorial
region.“ (Adelman et al. 2002)
Wade et al. 2006
Adelman et al. 2002

9. More spotted HgMn stars
Kochukhov et al. 2005
μ Lep: Kochukhov et al. 2011
AR Aur: Hubrig et al. 2006

10. Mapping chemical spots
From O. Kochukhov

11. First spot map: Hg in α And
Adelman et al. 2002

12. Configurations of chemical spots: 66 EriA
General asymmetry of chemical composition for the two hemispheres.
All four studied elements show higher abundance at rotational phases from 0.5 – 0.1 and a lower abundance for phases 0.1–0.5.
Makaganiuk et al. 2011a
A relative element underabundance on the side facing the secondary has also been reported for Y in AR Aur A (Hubrig et al. 2006),

13. Configurations of chemical spots: HD11753 (or φ Phe)
Y shows the largest
variability
Sr concentrates in
one spot
Ti has the largest
area covered by
spots
Cr shows the
smallest variability
Makaganiuk et al. 2012

14. “Weather” in α Andromedae
Slow variations in the chemical structures of HgMn star α And are seen from maps spanning seven years
Kochukhov et al. (2007) explained the behaviour with a non-equilibrium, dynamical evolution of the heavy-element clouds created by atomic diffusion.
Possibly the same underlying physics as the weather patterns on terrestrial and giant planets
Kochukhov et al. 2007

15. Secular spot evolution is also seen in AR Aur
Epochs of observations black diamonds: 2002 blue crosses: 2005 green circles: 2008 All observations from phase ~0.80
Hubrig et al. 2010

16. Long-term observations of HD11753
YII
SrII
Oct 2000
Dec 2000
Aug 2009
Jan 2010
Korhonen et al. 2013
All the data from CORALIE spectrograph at La Silla

17. Equivalent Widths at different epochs
Korhonen et al. 2013
Oct 2000 (plus), Dec 2000 (asterisk), Aug 2009 (square), Jan 2010 (triangle)

18. Fast temporal evolution of spots in HD11753
Oct 2000
Fast temporal evolution of spots in HD11753
Oct part1
First discovered by Briquet et al. (2010)
Reliability studied in more detail by Korhonen et al. (2013)
Oct part 2
Dec 2000
Korhonen et al. 2013

19. Magnetic fields in HgMn stars?
Detections of magnetic fields in some HgMn stars have been reported:
e.g., Mathys & Hubrig 1995; Hubrig & Castelli 2001; Hubrig et al. 2006
Other studies on the other hand have not found magnetic fields:
e.g., Landstreet 1982; Shorlin et al. 2002; Wade et al. 2006; Makaganiuk et al. 2011
At times the results agree, e.g., the non-detection of magnetic field in HD (Hubrig et al. 1999, Hubrig et al. 2006; Kochukhov et al. 2013)
At times the the results do not agree, e.g., in AR Aur Hubrig et al. (2010) detect weak field and Folsom et al. (2010) do not.
In the cases of discrepancy most of the non-detections are using LSD method, and the detections using the moment technique.
HD 71066
Kochukhov et al. 2013

20. Correlation of the magnetic field and spots?
HD 11753
Korhonen et al. 2013
NOTE: Investigations using LSD method have not found magnetic fields in HD (Makaganiuk et al. 2012; Kochukhov et al. 2013)
Hubrig et al. 2012

21. Conclusions HgMn stars are usually part of a binary or multiple system
Many of them show line-profile variations caused by chemical spots, most often in Hg and Mn, but also in other elements, e.g., Y, Sr, Ti, Cr and Ba
Secular spot evolution was discovered by Kochukhov et al. (2007)
Fast spot evolution by Briquet et al. (2010)
Weak magnetic fields have been reported in some HgMn stars
More detailed studies of magnetic fields using high resolution, high signal-to-noise spectropolarimetric observations are needed to resolve the issue concerning magnetic field detections.