RU Lup SPIRou observations - IRYSS

Alexis - last update 2025-12-18

News from 2025-12-pres

• Slides at pres/2025_alexislavail_zoomIRYSS.pdf
• Comments:
  • Bonnie: check Stokes V in emission lines
  • Check Helium line for the double peaked absorption component (cf Armeni 2024)
  • Evelyne: check Stokes V in He 1083 nm
  • Colour code data points in Bl phase folded curve

Misc

• vmin vmax for longitudinal field -30 to 24 km/s
• Remember: SPIRou wavelength are in vacuum. vald wavelength need to be converted with air2vac (done)

Worklog

2025-09-08

Looking seriously at the wavelengt intervals used in Sousa et al. (2023) to compute veiling. The plots for RU Lup in the YJHK bands are shown below.

Concerns:

1. wavelength region are very narrow -> large uncertainties on veiling

2. renormalization clearly needed for the K band interval, but also for perhaps H band.

TODO

BERV (DONE)

The spectra are BERV corrected.

Compute using barrycorrpy and correct at spirou_addsplice.py runtime. Need to grab the fits keywords for observation time (MJDMID is probably best) and target coordinates + observatory coordinates.

Done, check compute_berv in spirou_addsplice.py. When spectra are co-added, they are interpolated to the wavelength solution of the first spectrum before being added.

Surface gravity

Estimate log(g). I still have the notebook with the methology I used for Lavail et al. (2019). The methodology is (quoted from the paper):

To place the stars on the H-R diagram, we used effective temperatures from the literature, and derived consistent stellar luminosities following a methodology adapted from Villebrun et al. (2019). We obtained J-band magnitudes m_J from 2MASS (Cutri et al. 2003), V-band magnitudes m_V from Bouvier & Appenzeller (1992) and Torres et al. (2006, and references therein), and parallaxes \pi from Gaia DR2 (Gaia Collaboration 2016, 2018). Then, we obtained the stellar luminosities through the following set of equations:

E(V - J) = (m_V - m_J) - (V - J)_0

A_J = R_J \times E(V - J)

M_J = m_J + 5 + 5 \log_{10}(\pi) - A_J

M_{\text{bol}} = M_J + BC_J

\frac{L}{L_\odot} = 10^{-(M_{\text{bol}} - M_{\text{bol},\odot})/2.5}

where (V - J)_0 is the empirical intrinsic colour and E(V - J) the colour excess, A_J the extinction in the J-band, R_J the total to selective extinction set to 0.437 following Villebrun et al. (2019), \pi the parallax in arcseconds, and BC_J the bolometric correction in the J-band. The empirical intrinsic colours and bolometric corrections for 5–30 Myr PMS stars were computed according to Pecaut & Mamajek (2013), and we adopted the associated value of M_{\text{bol},\odot} = 4.755.

Veiling

Veiling: measure veiling. Suggestion from JF: measure in each band following Sousa et al. (2023). In that paper, they measure veiling in the following wavelength intervals:

1. 10710 Å − 10810 Å (Y),
2. 12840 Å − 12910 Å (J),
3. 16120 Å − 16220 Å (H),
4. 22600 Å − 22690 Å (K)

However :

The stars RU Lup, DO Tau and, DG Tau present many emission lines along the spec tra, probably originating from the accretion shock, which is a characteristic of high-mass accretion rate systems, which prevented us from using the same Y and J spectral regions for the veiling calculations. Then, for these targets, we used the spectral regions 10760 Å−10785 Å and 12400 Å−12550 Å to measure the r_Y and r_J veilings, respectively.

The methodology is the compare the depth of line in the target spectrum with a WTTS (non-accreting) of similar spectral parameters. What about comparing with a synthetic spectrum computed for the target stellar parameters?

The table below lists the WTTS used for measuring veiling by Sousa et al. (2023) (auto-extracted from PDF - beware and double check the paper for values if critical)

RU Lup has the highest veiling of the lot, DG Tau and DO Tau come second and third.

Star	Std	vrad	rY	rJ	rH	rK	EWHeI	EWPaβ	EWBrγ	Ṁ_Paβ	Ṁ_Brγ	α2-8
CI Tau	V819TAU	16.3 ± 0.5	0.53 ± 0.28	0.49 ± 0.17	0.39 ± 0.09	0.92 ± 0.23	9.5 ± 3.2	14.0 ± 2.6	7.9 ± 1.8	2.2	4.2	-0.84
DoAr 44	V819TAU	-6.1 ± 0.7	0.20 ± 0.09	0.48 ± 0.10	0.60 ± 0.06	1.28 ± 0.05	5.4 ± 1.4	9.1 ± 0.8	3.8 ± 0.5	1.7	1.5	-1.09
GQ Lup	TWA9A	-3.0 ± 0.3	0.19 ± 0.09	0.58 ± 0.11	0.78 ± 0.14	1.87 ± 0.26	0.9 ± 2.0	6.3 ± 1.6	2.0 ± 0.7	2.5	1.9	-0.89
TW Hya	TWA25	12.4 ± 0.1	0.08 ± 0.07	0.09 ± 0.06	0.10 ± 0.05	0.23 ± 0.11	5.1 ± 4.9	15.9 ± 6.2	6.8 ± 2.6	0.6	0.3	-1.92
V2129 Oph	V819TAU	-7.1 ± 0.6	0.05 ± 0.10	0.11 ± 0.06	0.25 ± 0.07	0.76 ± 0.16	0.9 ± 1.1	1.0 ± 0.7	0.5 ± 0.3	0.2	0.1	-1.62
BP Tau	V819TAU	15.2 ± 0.6	0.22 ± 0.09	0.36 ± 0.06	0.36 ± 0.09	0.78 ± 0.10	3.9 ± 1.4	7.7 ± 1.4	3.2 ± 0.8	1.3	1.1	-1.69
DG Tau	TWA9A	15.1 ± 3.4	0.29 ± 0.22	0.80 ± 0.20	1.09 ± 0.16	2.90 ± 0.51	11.7 ± 2.7	16.3 ± 2.1	6.8 ± 1.0	6.4	7.6	-0.26
RU Lup	TWA9A	-1.3 ± 1.4	1.14 ± 0.51	1.70 ± 0.65	1.65 ± 0.44	6.27 ± 2.97	23.2 ± 4.0	30.1 ± 3.0	12.2 ± 1.5	7.8	11.9	-0.21
V2247 Oph	TWA25	-5.8 ± 0.5	-0.02 ± 0.07	-0.06 ± 0.01	0.01 ± 0.03	-0.03 ± 0.02	0.0 ± 0.2	0.1 ± 0.1	-0.1 ± 0.2	0.009	–	-2.54
DO Tau	TWA25	16.1 ± 1.0	0.50 ± 0.40	0.78 ± 0.41	1.07 ± 0.32	2.33 ± 0.61	1.0 ± 1.8	12.7 ± 3.9	4.0 ± 1.9	2.3	3.4	-0.54
V347 Aur	TWA25	8.1 ± 0.6	0.31 ± 0.19	0.46 ± 0.26	0.37 ± 0.15	1.12 ± 0.31	-0.9 ± 1.1	6.7 ± 2.1	2.9 ± 1.0	7.1	7.3	-0.62
J1604	V819TAU	-5.8 ± 0.8	-0.14 ± 0.11	0.20 ± 0.07	0.22 ± 0.13	0.81 ± 0.23	-2.6 ± 1.8	-0.1 ± 0.2	0.3 ± 0.1	–	0.013	-2.81
PDS 70	TWA9A	5.0 ± 0.4	0.02 ± 0.11	0.18 ± 0.04	0.19 ± 0.07	0.34 ± 0.08	-0.7 ± 0.9	0.2 ± 0.2	0.1 ± 0.2	0.007	0.003	–
GM Aur	TWA9A	14.5 ± 0.3	-0.00 ± 0.06	0.13 ± 0.09	0.11 ± 0.06	0.31 ± 0.10	3.4 ± 2.8	10.2 ± 3.2	4.7 ± 1.9	1.3	1.0	–

And some stellar parameters

Star	SpT	v sin i	Av	i	2018	2019a	2019b	2020a	2020b	2021a	2021b	2022a	References
Accreting systems
CI Tau	K4	9.5±0.5	0.65	55+35/-10	2	6	26	5	39	–	–	–	(1), (2), (2), (2)
DoAr 44	K2-K3	17.0±1.1	2.0±0.2	30±5	–	8	–	–	–	–	–	–	(3), (3), (3), (3)
GQ Lup	K7	5±1	0.7	~30	–	8	–	18	6	–	–	–	(4), (5), (4), (5)
TW Hya	K6	6.0±1.2	0.0	18±10	–	12	–	14	–	27	–	–	(1), (1), (6), (7)
V2129 Oph	K5	14.5±0.3	0.6	60	9	–	–	17	8	–	–	–	(1), (1), (8), (9)
BP Tau	K5	9.0±0.5	0.45	~45	–	–	21	–	–	–	34	–	(10), (11), (6), (11)
V347 Aur	M2-M3	11.7+0.16/-0.24	3.4	40	–	–	18	–	13	12	22	–	(12), (13), (12), (14)
DG Tau	K6	24.7±0.7	1.60±0.15	38±2	–	–	–	2	29	–	–	–	(10), (10), (6), (15)
RU Lup	K7	8.5±4.8	0.0	24	–	–	–	9	–	17	13	1	(16), (17), (14), (18)
V2247 Oph	M0	20.5±0.5	0.98±0.02	45±10	–	–	–	9	7	–	–	–	(19), (20), (19), (20)
DO Tau	M0	14.3±0.5	0.75	37.0±3.7	–	–	–	3	8	–	–	–	(6), (21), (6), (15)
J1604	K3	17.3±0.4	1.0	>61	–	–	–	12	–	–	–	–	(22), (22), (24), (23)
PDS 70	K7	16.0±0.5	0.01±0.07	50±8	–	–	–	4	–	–	–	6	(19), (25), (19), (25)
GM Aur	K4-K5	14.9±0.3	0.3±0.3	≥63	–	–	–	–	2	–	34	–	(26), (26), (26), (26)
Non-accreting systems
V819 Tau	K4	9.5	–	–	–	1	–	–	–	–	–	–	(27), (27)
TWA 25	M0.5	12.9±1.2	–	–	25	14	–	–	–	–	–	–	(6), (1)
TWA 9A	K6	7±3	–	–	–	1	–	–	–	–	–	–	(6), (1)

From Sect. 4.3 of Sousa et al. (2023):

RU Lup is the unique target with an evident change in the veiling along the observational periods in the four bands, but much more pronounced in the K band, along with a high standard deviation. We associate this change in the veiling with an occasional high accretion episode that occurred in 2021a, and despite the veiling still being high in 2021b, it seems to start to diminish later on. In 2022a, it is even smaller, but we have only one observation to serve as the basis for this assumption. The circumstellar emission lines’ equivalent widths corroborate with this assumption, as they increase in 2021a and start to decrease in the subsequent observation periods, similarly to the veiling. In contrast, the average veiling is stable, at least for most of the stars we analyzed, except for very high accreting systems, such as RU Lup, which can present episodic high veiling.

Methods

Different possibilities here:

• compare with a SPIRou spectrum of a non-accreting WTTS (TWA 9) shifted + broadened.
• compare with a synthetic spectrum? The issue there is the reliability of the line list.
• compare LSD profiles computed in different bands for RU Lup and e.g TWA 9. Use CO lines for K band.

Extracted from VALD3 Teff 4000 K, log(g) = 4, vmic = 2 km/s, threshold = 0.01, line list between 9500 and 25000 Å. Contains 9336 lines.

Reminder, disk integration is done with e.g

./s3div.Linux t4000g4.0_B0.0kG.mout s.prf 8.5 0. 1000000. 70000.

Formula

I am always confused by the actual veiling formula so here is a reminder from Stempels & Piskunov (2003)

The contribution of the veiling continuum to the overall spectrum of CTTS is a function of wavelength. Therefore, it is appropriate to define the so-called veiling factor V(\lambda), which is the relative strength of the veiling component compared with the stellar component at a certain wavelength \lambda. Here it is assumed that the veiling factor does not change throughout the observed interval around \lambda, which is true if the interval is short with respect to the typical size of the veiling continuum. Thus,

V(\lambda) = \frac{I_{vc}}{I_{sc}}

where I_{vc} is the intensity of the veiling continuum and I_{sc} the intensity of the stellar continuum. By defining d as the unveiled relative line depth, and d^* as the observed relative line depth, the veiling at a certain wavelength \lambda can be determined by minimizing

\chi^2 = \left(\frac{d^* - \frac{d}{1 + V(\lambda)}}{\sigma_d}\right)^2

Here \sigma_d is the standard error of the line depth d, which can be determined from the SNR of the observations in the continuum. The resulting formal error \sigma_V of V can be calculated from the standard relation \sigma_V^2 = 2/\nabla\chi^2(V). However, as will be shown later, the true error on the veiling measurements is larger than the formal error \sigma_V, because of small differences between the line shapes of synthetic spectra and observed spectra due to errors in the atomic data and limitations in our spectral synthesis calculations and stellar atmosphere models.

For this method to work, a template spectrum providing d is needed. This can either be an observed non-veiled template or a synthetic spectrum. The method we use for veiling determinations is similar to the method used by Hartigan et al. (1989), with the only difference that in these studies observed spectra are used as templates for the underlying photosphere, while we calculate synthetic template spectra.

Previous papers

• Armeni et al. (2024) - "Evidence for magnetic boundary layer accretion in RU Lup - A spectrophotometric analysis"
• Wojtczak et al. (2024) - " The interplay between disk wind and magnetospheric accretion mechanisms in the innermost environment of RU Lup." VLTI Gravity paper.
• Stock et al. (2022) - "Accretion variability in RU Lup". Paper based on ESPadOnS data.
• Huang et al. (2020) - "Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup"
• Gahm et al. (2013) - "Face to phase with RU Lupi"

Stellar parameters

From Armeni et al. 2024, from ESPRESSO high-res, Table 1

Parameter	Value	Ref.
d	158.9 ± 0.7 pc	[1]
SpT	K7	[2]
Teff	4250 ± 60 K	[3]
v sin i	8.6 ± 1.4 km s⁻¹	[3]
RV	0.55 ± 0.06 km s⁻¹	[3]
VF₅₅₀₀	1.57 ± 0.31	[3]
L⋆	1.46 ± 0.67 L☉	[4]
M⋆	0.55 ± 0.13 M☉	[4]
R⋆	2.27 ± 0.52 R☉	[3]
P⋆	3.71 ± 0.01 d	[5]
i⋆	16 ± 5°	[3]
iᵈ	16₊₆₋₈°	[6]
Rco	∼3.64 R⋆	[3]
Av	∼0.07 mag	[7]

References for Table 1:

• [1] Gaia Collaboration (2021)
• [2] Alcalá et al. (2017)
• [3] This work (Sect. 3)
• [4] Manara et al. (2023)
• [5] Stempels et al. (2007)
• [6] GRAVITY Collaboration (2021)
• [7] Herczeg et al. (2005)

Interesting individual spectral lines in the near-IR

In the following plots, the left panel splits the observation in the 3 observing cycles. Right panel has everything stacked. The observation are sorted in 3 periods.

1. 2020-05-31 to 2020-07-10 (9 exp)
2. 2021-06-19 to 2021-08-26 (30 exp)
3. 2022-05-15 ( 1exp)

Of course, the classic He I 1083 nm line Plot as PNG, PDF

But also:

Emission in the Paschen-β and Brackett-γ lines of H I (1282.16 and 2166.12 nm, respectively) can be used as a measure of accre- tion (Natta et al. 2004; Rigliaco et al. 2012), but can also reveal outflows (Whelan et al. 2004)

-- from Donati et al. (2025) section 5.

Bracket γ Plot as PNG, PDF

Paschen β Plot as PNG, PDF

Helium 2058