Sean Brittain Herbig Ae/Be Stars Clemson University
Supported by NSF AST-0954811 Herbig Ae/Be Stars in Context
Accretion properties of Herbig Ae/Be stars Outline Disk properties of Herbig Ae/Be Stars
Herbig Ae/Be Stars as Laboratories for Studying Planet Formation
Spectral type F5-B0 with emission lines
Defining a Infrared excess (i.e. a disk, not classical New Class Be)
Luminosity class III- V (not B[e] supergiants)
Waters & Waelkens 1998 2-10 M⊙
Defining a New Class: Analogs to Disk CTTSs
Pre/Zero Age Main Sequence Herbig Ae/Be Stars: Stellar Evolutionary Perspective B8 A0 F0 G0 K0 M0
T Tauri Stars
Intermediate Mass T Tauri Stars
Herbig Ae/Be Stars ≲10% have detectable B-fields (Alecian+2013) Magnetic Properties Fields greater than 200 G are very rare, most less than 100 G (Hubrig+2019). There are exceptions of Herbig such as the 3.5kG HD101412 (Hubrig+2010) Ae/Be Stars Evidence that early HBe stars are less magnetic than HAe stars and that there is a break in the accretion properties between HAe and HBe stars (Vink+2002, 2003, 2005; Mottram+2007; Cauley& Johns Krull+2014, 2015; Ababakr+2017 – but also see Reiter+2018) Accretion on to Herbig Ae/Be Stars
? (e.g., Muzerolle+2004)
Boundary layer accretion? (e.g., Cauley & Johns-Krull 2014, 2015)
Adapted from Kraus et al. 2008 Accretion on to Herbig Ae/Be Stars
Guimarães et al. 2006 Accretion on to Herbig Ae/Be Stars
Spectro-interferometry of Br g implies the HI from HD 100546 arises from a Keplerian disk. Mendigutia+2015 Accretion on to Herbig Ae/Be Stars
90% of sample could be fit with MSA model Fairlamb+2015, 2017 How do the magnetic properties of young stars evolve as they transition from IMTTs to HAeBes?
Why do some HAeBes harbor kG magnetic fields (e.g., V380 Ori and HD101412)? Open What is the topology of the magnetic fields? Questions What is the origin of the relationship between the luminosity of emission lines and the stellar accretion rate?
See talks by James Muzerolle, Christian Schneider, Jorick Vink, Evelyne Alecian, and Silva Järvinen Herbig Ae/Be Disks: Group I vs Group II
Meeus+2001; Dullemond+2002 Relationship between Stellar Mass and Disk Fraction
Ribas+2015 Continuum mm flux: T, k, gas/dust, and distribution uncertain
H2: E2’=500K, weak oscillator strengths, disk optically thick at Measuring lowest energy lines (28mm) Mass is HD: E1’=120K, low abundance, Hard! model dependent, lines are widely spaced (120, 60, 40, 30, 20mm).
CO: E1’=5K, unclear abundance, dissociation, freeze out Alternative Estimate: Stellar Accretion Rate
−휂 • 푀ሶ 푡 = 푀ሶ (푡0)(푡/푡0)
−휂+1 ∞ −푀ሶ (푡0)푡0(푡/푡0) ∞ 푀ሶ (푡0) 푡0 = | = 푀푑푖푠푘 = 푀ሶ 푡 푑푡 • 푡0 −휂+1 푡0 휂−1
• For 휂 = 3Τ2 푀푑푖푠푘 = 2푀ሶ 푡0
• Need age and accretion rate – provides the mass of reservoir available for accretion. • Accretion rates variable • Not all disk mass accretes (R≳100au)
Sicilia-Aguilar+2010 Comparison of Methods 1. CO observations imply gas/dust~10 (e.g., Williams & Best 2014) 2. Dust observations assume gas/dust=100 3. Accretion rate measures imply gas/dust=1000 0.1x 1x 10x
Dong, Najita, & Brittain 2018 l Boö Herbig Ae/Be Stars
Dust Rich Dust Poor
Banzatti+2018 l Boö Herbig Ae/Be Stars
Kama+2015 Drake+2005 Disk Masses of Herbig Ae/Be Stars
Dong, Najita, & Brittain 2018 Gravitationally Unstable Disks
Hall+2019 AB AUR MWC 480 MWC 758 PDS 201 HD 56895 HD 97048
HIP 54557 HD 100546 HD104237 PDS 141 PDS 389 SAO 206462
PDS 395 PDS 76 HD 142527 PDS 78 PDS 80 HIP 80425
IRS 48 WLY 1-53 HD 148352 HIP 81474 HD 163296 HD 169142
Hashimoto+11; Kusakabe+12; Benisty+15; Ginski+16; Follette+17; Stokler+17; Avenhaus+17; Follette+15; Monnier+17; Pohl+17 See talk by Antonio Garufi Dong+2018 Planets Form around Intermediate Mass Stars
HR 8799 (F0)
b PIC (A6)
MAROIS, ET AL. 2008
• L AGRANGE ET AL. 2010 Planet Fraction vs Stellar Mass
Johnson+ 2010 Indirect Signatures
planets? GI?
Dong, Najita, & Brittain 2018 There are few detections of gas giant planets orbiting young, intermediate mass stars from 30-300 au (3/110; Bowler et al. 2016) Cold start or rare? b Pic is likely hot start (Snellen+2018; Dupuy+2019)
What is the origin of spiral structure?
How do we rule out the presence of spiral structure in disks?
Is it feasible to get uniform sensitivity on a sample that includes GI and GII sources?
Kratter & Lodato 2016 What is the actual mass of disks around Herbig Ae/Be stars?
Is the spiral structure caused by planets or some other effect?
Why do the disks around Herbig Ae/Be stars dissipate faster? Open Why do some disks seem to persist for very long times? Questions Are we missing WTTS analogs?
How do we probe the structure of Group II disks
What is the connection between the presence of gas giant planets and disk structures observed in disks around Herbig Ae/Be Stars Close-in gas giant planets appear to be more common around intermediate mass stars than their lower mass counterparts
Signatures of gas giant planets from 30- 300au are common (so far)
Herbig Ae/Be Stars as a Detections of gas giant planets from 30- Planet Formation 300au are rare. Therefore cold start? Laboratory
If so, then forming planets should radiate away their accretion energy and be quite bright.
Yet direct images of gas giant planets in disks are rare. IR Sub-mm
Credit: Jaehan Bae MIR better than NIR (Szulagyi+2019)?
Herbig Ae/Be Stars as a Planet Formation Episodic Accretion Laboratory (Brittain+2019)?
Other approaches? Spectroscopic Signposts of Giant Planet Formation
Regaly et al. 2010
Ayliffe & Bate 2010
Rdisk~1RH; Szulagyi+2014 Gemini IRTF VLT Keck
ALMA
Credit: Dr. Andrea Banzatti Spectrally Resolved Lines as Surrogates for High Resolution Imaging
−½ v(M*,i,r)∝r
(See Smak 1981) Spectrally Resolved Lines as Surrogates for High Resolution Imaging
−½ v(M*,i,r)∝r
(See Smak 1981)
Spectroastrometry
Red
Dl Dl Blue
Dx
−½ v(M*,i,r)∝r ?
(See Whelan & Garcia 2008) HD 100546: rovib CO
• CO hot bands (Dv=1, vlow>0) UV Fluoresced • CO v=1 also has thermal component • R(CO)~12 au – 100 au
Brittain et al. 2009; See also van der Plas et al. 2009; Hein Bertelsen 2014
Free of molecules: Habart+ 2006; Brittain+ 2009; van der Plas+2009; Carmona+ 2011; Liskowsky+2012
Evolution of the v=1-0 P26 CO Line Profile and Spectroastrometric Signal
Spectroastrometric Emission line Signal
2003
2006
2010
2013
Brittain+2014 Brittain+ 2019 Spectroastrometric Signal of the v=1-0 P26 CO line
Black: 2003 Red: 2017
Brittain+ 2019 Brittain+ 2019 Are we seeing emission from the circumplanetary disk or a bright spot on the inner rim?
Is such emission relatively Open Questions common?
What is the structure of circumplanetary disks (envelopes?)? How do Herbig Ae/Be Stars Accrete?
How Massive are Summary Herbig Ae/Be Star Disks?
How Common are Gas Giant Planets around Intermediate Mass Stars?