Measuring the Magnetic Field of Young Stars Using iSHELL Observations: BP Tau and V347 Aur

Flores, Carolina; Reipurth, Bo; Boogert, A. C. A.

doi:10.3847/1538-4357/ab35d4

Cited by 28 publications

(36 citation statements)

References 84 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the intensity spectrum, we were able to fit the unsigned magnetic field contained in active regions, for the Zeeman broadening, they produce in NIR atomic lines of various Landé factors. This analysis gave a magnetic field of 1.9 kG distributed over 15% of the stellar surface, corresponding to Bf value of 290 ± 58 G. These values are similar to other magnetic field measurements of stars in the same domain of rotation period and mass (Cranmer & Saar 2011;See et al 2019;Shulyak et al 2019;Flores et al 2019).…”

Section: Discussionsupporting

confidence: 86%

“…This value of the magnetic field strength and flux for HD 189733 is intermediate between nonactive, slow-rotators M dwarfs such as Gl 411 or Gl 380, which have typical fields lower than 1 kG (Moutou et al 2017;Flores et al 2019), and fast-rotator M dwarfs whose field usually ranges from 2 to 5 kG (Shulyak et al 2019). With a rotational period of 12 days, HD 189733 is similar to Gl 49, DS Leo, Gl 208 or CE Boo, whose magnetic field fluxes lie between 0.5 and 2 kG according to far-red measurements of FeH and Ti (see Fig.…”

Section: Zeeman Broadeningmentioning

confidence: 89%

“…The choice for these specific lines is the result of a trade-off analysis using the following criteria: large (and, respectively, very small) Landé factors, large line depths, no blending, and long wavelengths. Atomic and molecular lines in the K band that are used in M stars (e.g., Flores et al 2019), for instance, are too weak in the spectrum of HD 189733. Synthetic spectra including Zeeman splitting were calculated using the ZEEMAN spectrum synthesis code (Landstreet 1988;Wade et al 2001;Folsom et al 2016).…”

Section: Zeeman Broadeningmentioning

confidence: 99%

See 2 more Smart Citations

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

Moutou

Dalal

Donati

et al. 2020

A&A

View full text Add to dashboard Cite

SPIRou is the newest spectropolarimeter and high-precision velocimeter that has recently been installed at the Canada-France-Hawaii Telescope on Maunakea, Hawaii. It operates in the near-infrared and simultaneously covers the 0.98–2.35 μm domain at high spectral resolution. SPIRou is optimized for exoplanet search and characterization with the radial-velocity technique, and for polarization measurements in stellar lines and subsequent magnetic field studies. The host of the transiting hot Jupiter HD 189733 b has been observed during early science runs. We present the first near-infrared spectropolarimetric observations of the planet-hosting star as well as the stellar radial velocities as measured by SPIRou throughout the planetary orbit and two transit sequences. The planetary orbit and Rossiter-McLaughlin anomaly are both investigated and modeled. The orbital parameters and obliquity are all compatible with the values found in the optical. The obtained radial-velocity precision is compatible with about twice the photon-noise estimates for a K2 star under these conditions. The additional scatter around the orbit, of about 8 m s−1, agrees with previous results that showed that the activity-induced scatter is the dominant factor. We analyzed the polarimetric signal, Zeeman broadening, and chromospheric activity tracers such as the 1083nm HeI and the 1282nm Paβ lines to investigate stellar activity. First estimates of the average unsigned magnetic flux from the Zeeman broadening of the FeI lines give a magnetic flux of 290 ± 58 G, and the large-scale longitudinal field shows typical values of a few Gauss. These observations illustrate the potential of SPIRou for exoplanet characterization and magnetic and stellar activity studies.

show abstract

Section: Discussionsupporting

confidence: 86%

Section: Zeeman Broadeningmentioning

confidence: 89%

Section: Zeeman Broadeningmentioning

confidence: 99%

See 1 more Smart Citation

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

Moutou

Dalal

Donati

et al. 2020

A&A

View full text Add to dashboard Cite

show abstract

“…The spectral index determined by Connelley & Greene (2010), α=0.05, implies a flat-spectrum source, i.e., a transitional Class I protostar-Class II Classical T Tauri star (Lada & Wilking 1984). Flores et al (2019) used the cross-dispersed, high-resolution, near-infrared spectrograph iSHELL on the IRTF to measure the magnetic field strength associated with V347 Aur, and derived several fundamental properties. Their best-fit model parameters included effective temperature, T e =3233 K; log(g)=3.25; vsin(i)=11.7 km s −1 ; and magnetic field strength B= 1.36 kG.…”

Section: Properties Of V347 Aurmentioning

confidence: 99%

“…Their best-fit model parameters included effective temperature, T e =3233 K; log(g)=3.25; vsin(i)=11.7 km s −1 ; and magnetic field strength B= 1.36 kG. Flores et al (2019) placed V347 Aur on the colormagnitude diagram to compare its position with the evolutionary models of Baraffe et al (2015) and Feiden (2016), finding a track-dependent mass in the range ∼0.2-0.4 M e and an age <1 Myr.…”

Section: Properties Of V347 Aurmentioning

confidence: 99%

Periodic Eruptive Variability of the Isolated Pre-main-sequence Star V347 Aurigae

Dahm

Hillenbrand

2020

View full text Add to dashboard Cite

V347 Aurigae is associated with the small dark cloud L1438 and appears to be an isolated pre-main-sequence star located at distance d≈200 pc. Multi-epoch, archival photometry reveals periodic brightness variations with amplitude V≈2.0 mag occurring on timescales of ∼160 days that have persisted for decades. Regular-cadence, optical imaging of the source with the Zwicky Transient Facility shows that a small reflection nebula illuminated by V347 Aur also fluctuates in brightness, at times fading completely. Multi-epoch, Keck/HIRES data suggests the presence of two distinct spectral components: a prominent emission-line-dominated spectrum with a heavily veiled continuum correlated with the bright photometric state, and an M-type absorption line spectrum associated with quiescence. All spectra exhibit strong Balmer and He I line emission, consistent with accretion, as well as high velocity emission arising from the forbidden transitions of [O I], [N II], and [S II] that are generally associated with collimated jets and disk winds. There is no evidence in existing high-dispersion spectroscopy or high-resolution imaging for binarity of V347 Aur. The repeating outburst events are possibly linked to accretion instabilities induced by an undetected companion or a structure within the circumstellar disk that periodically increases the mass accretion rate. V347 Aur is perhaps analogous to an EXor-type variable, though more regularly recurring.

show abstract

Hidden magnetic fields of young suns

Kochukhov

Hackman

Lehtinen

et al. 2020

A&A

View full text Add to dashboard Cite

Global magnetic fields of active solar-like stars are nowadays routinely detected with spectropolarimetric measurements and are mapped with Zeeman-Doppler imaging (ZDI). However, due to the cancellation of opposite field polarities, polarimetry captures only a tiny fraction of the magnetic flux and cannot assess the overall stellar surface magnetic field if it is dominated by a smallscale component. Analysis of Zeeman broadening in high-resolution intensity spectra can reveal these hidden complex magnetic fields. Historically, there were very few attempts to obtain such measurements for G dwarf stars due to the difficulty of disentangling Zeeman effect from other broadening mechanisms affecting spectral lines. Here we developed a new magnetic field diagnostic method based on relative Zeeman intensification of optical atomic lines with different magnetic sensitivity. Using this technique we obtained 78 field strength measurements for 15 Sun-like stars, including some of the best-studied young solar twins. We find that the average magnetic field strength B f drops from 1.3-2.0 kG in stars younger than about 120 Myr to 0.2-0.8 kG in older stars. The mean field strength shows a clear correlation with the Rossby number and with the coronal and chromospheric emission indicators. Our results suggest that magnetic regions have roughly the same local field strength B ≈ 3.2 kG in all stars, with the filling factor f of these regions systematically increasing with stellar activity. Comparing our results with the spectropolarimetric analyses of global magnetic fields in the same stars, we find that ZDI recovers about 1% of the total magnetic field energy in the most active stars. This figure drops to just 0.01% for the least active targets.

show abstract

Measuring the Magnetic Field of Young Stars Using iSHELL Observations: BP Tau and V347 Aur

Cited by 28 publications

References 84 publications

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

Periodic Eruptive Variability of the Isolated Pre-main-sequence Star V347 Aurigae

Hidden magnetic fields of young suns

Contact Info

Product

Resources

About