Identification of Be Stars from LAMOST

http://www.astrosurf.com/buil/bestars/m45/img.htmChien-Cheng Lin (林建爭)1, J.L. Hou1, L. Chen1, Z.Y. Shao1, W.P. Chen2, C.D. Lee2, P.C. Yu3, C.H. Hsia4, 1. Shanghai Astronomical Observatory, CAS 2. National Central Univ., 3. UCLA, 4. HKU

• Non-supergiants B-type with Balmer emission lines stars. • Rapidly rotating stars, 75% of breakup velocity (>100 km/s) or

above (Slettebak 1966) —> circumstellar discs. • Born as rapid rotators, binary mass transfer, main-sequence

evolution (Mathew+ 2008)

Be StarsAchernar

Rivinius+ 2013Kogure & Leung 2014

Spectral Type

Abs

olut

e m

agni

tude

EnvelopeStellar ActivitiesBinary interaction

• The increase fraction of Be stars in star clusters are found with increasing cluster distance from Galactic center (McSwain+ 2005). —> Low metallicity environment more Be stars. (so as field Be stars?)

• A homogenous (same survey) and comprehensive (age, distance, metallicity, rotation, etc.) Be star sample is needed.

Motivations

log(t) <7.0

log(t) <7.4

log(t) <8.0

log(t) >8.0

LMC

Galactic Anti-Center

Galactic Center

SMC

Zhang+ 2005 & Neiner+ 2012 & Raddi+ 2015

To Be or not to Be, that is the question.

— William Shakespeare's play Hamlet 1564-1616

LAMOST• The Large Sky Area Multi-Object Fiber Spectroscopic Telescope is

located at Xinglong station (seeing 2’’) in the Hebei province of China.

NAOC Beijing

LAMOST Xinglong

LAMOST

• A quasi-meridian reflecting Schmidt telescope (3.6-4.9 m), focal length 20 m (Cui+ 2012).

6.67x6.05 m

Focal Surface

Corrector Mirror

5.72x4.40 m

Fiber Optics

SpectrographsSpherical Mirror

-10 < Dec < 60

LAMOST

• A total of 16 low-resolution spectrographs (R~1800), 32 CCDs, and 4000 fibers in optical 3700 to 9000A (Xing+ 1998).

5 deg

9000 Å3700 Å

Star

Galaxy

QSO

LAMOST• Aim to have 5-years survey cover about 5 million objects with a limiting

magnitude of 18.5 in R-band

• The Pilot Survey 2011.09 - 2012.06 (~0.7 m, 90% stars)

• The 1st Regular Survey 2012.09 - 2013.06 (~1.5 m, 87% stars)

• The 2nd Regular Survey 2013.09 - 2014.06 (~1.9 m, 92% stars)

http://dr1.lamost.org/

LAMOST DR1: 2.2 M Obj.• O: 202 • B: 3,403 • A: 101,327 • F: 826,387 • G: 422,736 • K: 465,187 • M: 122,676 • Double: 338 • CV/Carbon: 518 • EM: 227 • WD: 1,194 • Non: 260,487

• Known Be: 3000+ (23 observed)

relative flux

287 Be star candidates

HeHe Hα

HβMg

H-KsIPHAS: Raddi+ 2013

100 deg2, 181 Be stars

Hα emitters

Be stars

Zhang+ 2005, Neiner+ 2011 >2000+ Be stars

LAMOST 178 Be stars

J-H

Be Stars from LAMOST DR1

Spatial Distribution

GAC

• Only 2 candidates are found in the star clusters with different ages, one is in Kronberger 18 (~15 Myr), and the other is in FSR 1025 (~400 Myr) (Lin+ 2015, submitted).

APOGEE H-band lines (R: 22,500) Chojnowski et al. 2014

LAMOST VS. APOGEE

Rot. > 200 km/s

B9B6B9 B9B9B9 B6B9 B9B9

Fλ/Fc

• Emission-line stars are in almost any evolutionary stage. Be stars are particular interesting due to their high rotation speeds, circumstellar disks, and different fraction of members in star clusters.

• The LAMOST spectra provides us an excellent opportunity to identify Be stars. From the LAMOST DR1 2.2 M objects with empirical line equivalent widths of known Be stars, 178 stars were identified to be new Be candidates and mostly distributed around Galactic Anti-Center. Only 2 Be stars are in star clusters with age 15 Myr and 400 Myr.

• Search for more Be stars in DR2 4 M objects and estimate their rotational speeds. Distance, age, reddening, etc. of Be stars will be estimated if they are in star clusters.

Summary

BH & AGN meeting @ Shanghai: http://accretion2015.csp.escience.cn/