J/ApJ/873/L5 Magnetic field measurements of Ap/Bp stars (Chojnowski+, 2019)
Discovery of resolved magnetically split lines in SDSS/APOGEE spectra of 157
Ap/Bp stars.
Chojnowski S.D., Hubrig S., Hasselquist S., Castelli F., Whelan D.G.,
Majewski S.R., Nitschelm C., Garcia-Hernandez D.A., Stassun K.G., Zamora O.
<Astrophys. J., 873, L5 (2019)>
=2019ApJ...873L...5C 2019ApJ...873L...5C
ADC_Keywords: Stars, peculiar; Magnetic fields; Spectral types; Atomic physics;
Spectra, infrared; Spectra, optical
Keywords: atomic data ; infrared: stars ; stars: chemically peculiar ;
stars: magnetic field
Abstract:
We report on magnetic field measurements of 157 chemically peculiar
A/B stars (Ap/Bp) based on resolved, magnetically split absorption
lines present in H-band spectra provided by the Sloan Digital Sky
Survey (SDSS)/Apache Point Observatory Galactic Evolution Experiment
(APOGEE) survey. These stars represent the extreme magnetic end of a
still-growing sample of >900 Ap/Bp stars selected among the APOGEE
telluric standard stars as those with CeIII absorption lines and/or
literature Ap/Bp classifications. The lines most frequently resolved
into their split components for these stars in the H-band pertain
primarily pertain to CeIII, CrII, FeI, MnII, SiI, and CaII, in
addition to one or more unidentified ions. Using mean magnetic field
modulus () estimates for transitions with known Lande factors, we
estimate effective Lande factors for 5 CeIII lines and 15 unknown
lines and proceed to measure of 157 stars, only 3 of which have
previous literature estimates of . This 183% increase in the number
of Ap/Bp stars for which has been measured is a result of the
large number of stars observed by SDSS/APOGEE, extension of
high-resolution Ap/Bp star observations to fainter magnitudes, and the
advantages of long wavelengths for resolving magnetically split lines.
With ∼25kG, the star 2MASS J02563098+4534239 is currently the most
magnetic star of the SDSS/APOGEE sample. Effective Lande factors,
representative line profiles, and magnetic field moduli are presented.
The validity of the results is supported using optical,
high-resolution, follow-up spectra for 29 of the stars.
Description:
This Letter focuses primarily on data from the two APOGEE instruments,
which are 300-fiber, R=22500, H-band spectrographs that operate on the
Sloan 2.5m telescope at Apache Point Observatory (APO) and on the
Du Pont 2.5m telescope at Las Campanas Observatory (LCO).
We also obtained optical spectra of 29 stars using the Astrophysical
Research Consortium Echelle Spectrograph (ARCES) on the ARC 3.5m
telescope at APO. ARCES covers the full optical spectrum
(3500-10000Å) at a resolution of R=31500.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 149 Effective Lande g Factors; from erratum published
in 2019, ApJ, 876, L34
table2.dat 100 157 Magnetic field modulus estimates
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See also:
B/mk : Catalogue of Stellar Spectral Classifications (Skiff, 2009- )
III/218 : ELODIE archive (Prugniel+, 2001)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
III/260 : General Catalogue of Ap and Am stars (Renson+ 2009)
I/322 : UCAC4 Catalogue (Zacharias+, 2012)
J/AJ/149/7 : SDSS-III/APOGEE. I. Be stars (Chojnowski+, 2015)
J/ApJS/221/24 : SDSS-III APOGEE H-band spectral line lists (Shetrone+, 2015)
J/A+A/601/A14 : Radial velocities of magnetic Ap stars (Mathys, 2017)
J/MNRAS/480/2953 : Catalogue of CP stars (HgMn, ApBp, AmFm) (Ghazaryan+, 2018)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Ion Ion designation
8- 16 F9.3 0.1nm Wave [15148.35/16911.44] Vacuum wavelength; Angstroms
18- 23 F6.3 [-] log(gf) [-3.1/1.12]? log oscillator strength
25- 27 F3.1 --- Jlow [0/7]? Lower angular momentum quantum number
29- 33 F5.3 --- glow [0.5/3.004]? Lower Lande factor
35- 40 F6.3 eV Elow [0/13.7]? Lower energy value
42- 44 F3.1 --- Jhigh [0/8]? Upper angular momentum quantum number
46- 50 F5.3 --- ghigh [0/3.31]? Upper Lande factor
52- 57 F6.3 eV Ehigh [0.7/14.5]? Upper energy value
59- 63 F5.3 --- geff [0.5/2.15] Effective Lande g factor
65- 69 F5.3 --- e_geff [0.02/0.16] Uncertainty in geff
71- 72 I2 --- N* [1/98] Number of stars used
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- 2MASS 2MASS identifier
18- 33 A16 --- OName Other identifier
35- 39 F5.2 mag Vmag [6.3/12.4] UCAC4 catalog V band magnitude
41- 45 F5.2 mag Hmag [6.2/11] 2MASS H band magnitude
47- 48 I2 --- Nsp [1/25] Number of APOGEE spectra
50- 53 I4 --- S/N [54/1885] Signal-to-Noise ratio of combined
spectrum
55- 67 A13 --- SpT Estimated or literature spectral type
69 A1 --- r_SpT Reference code for SpType (1)
71- 75 F5.2 dT BH [3.58/24.61] Magnetic field modulus
from H band data in units of kGauss
77- 80 F4.2 dT e_BH [0.15/1.4] Uncertainty in BH
81 A1 --- u_BH [:] Uncertainty flag on BH (2)
83- 84 I2 --- o_BH [2/61] Number of spectral lines
used to measure BH
86- 90 F5.2 dT BO [4.6/23.6]? Magnetic field modulus
from optical data in units of kGauss
92- 95 F4.2 dT e_BO [0.03/1.1]? Uncertainty in BO
97 A1 --- r_BO Reference code for BO (1)
99-100 I2 --- o_BO [1/50]? Number of spectral lines
used to measure BO
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Note (1): Reference code as follows:
1 = Renson & Manfroid (2009A&A...498..961R 2009A&A...498..961R -- Cat. III/260)
2 = Skiff (2014, Cat. B/mk);
3 = SIMBAD;
4 = Own data (ARC 3.5m/ARCES)
5 = Mathys (2017, J/A+A/601/A14);
6 = Freyhammer et al. (2008MNRAS.389..441F 2008MNRAS.389..441F).
Note (2):
: = a less reliable measurement, usually due to large scatter between
different lines and/or measurements near the resolution limit of
APOGEE.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Aug-2020