J/ApJ/956/102 Accretion rates of TW Hya from 25yrs sp. obs. (Herczeg+, 2023) ================================================================================ Twenty-five years of accretion onto the classical T Tauri star TW Hya. Herczeg G.J., Chen Y., Donati J.-F., Dupree A.K., Walter F.M., Hillenbrand L.A., Johns-Krull C.M., Manara C.F., Gunther H.M., Fang M., Schneider P.C., Valenti J.A., Alencar S.H.P., Venuti L., Alcala J.M., Frasca A., Arulanantham N., Linsky J.L., Bouvier J., Brickhouse N.S., Calvet N., Espaillat C.C., Campbell-White J., Carpenter J.M., Chang S.-J., Cruz K.L., Dahm S.E., Eisloffel J., Edwards S., Fischer W.J., Guo Z., Henning T., Ji T., Jose J., Kastner J.H., Launhardt R., Principe D.A., Robinson C.E., Serna J., Siwak M., Sterzik M.F., Takasao S. =2023ApJ...956..102H ================================================================================ ADC_Keywords: Stars, variable; Spectra, optical; Extinction Keywords: Classical T Tauri stars ; Stellar accretion disks ; Protoplanetary disks ; High resolution spectroscopy ; Variable stars Abstract: Accretion plays a central role in the physics that governs the evolution and dispersal of protoplanetary disks. The primary goal of this paper is to analyze the stability over time of the mass accretion rate onto TW Hya, the nearest accreting solar-mass young star. We measure veiling across the optical spectrum in 1169 archival high-resolution spectra of TW Hya, obtained from 1998-2022. The veiling is then converted to accretion rate using 26 flux- calibrated spectra that cover the Balmer jump. The accretion rate measured from the excess continuum has an average of 2.51x10^-9^M_{sun}_/yr and a Gaussian distribution with an FWHM of 0.22 dex. This accretion rate may be underestimated by a factor of up to 1.5 because of uncertainty in the bolometric correction and another factor of 1.7 because of excluding the fraction of accretion energy that escapes in lines, especially Ly{alpha}. The accretion luminosities are well correlated with He line luminosities but poorly correlated with H{alpha} and H{beta} luminosity. The accretion rate is always flickering over hours but on longer timescales has been stable over 25 years. This level of variability is consistent with previous measurements for most, but not all, accreting young stars. Description: We measure veiling across the optical spectrum in 1169 archival high-resolution spectra of TW Hya, obtained from 1998-2022. The analysis for this survey is built from a foundation of 284 spectra obtained with the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) at the Canada-France-Hawaii Telescope (CFHT). We also downloaded reduced science spectra of TW Hya obtained with the Fiber-fed Extended Range Optical Spectrograph (FEROS) at MPG/ESO 2.2m telescope, the High Accuracy Radial velocity Planet Searcher (HARPS) at the ESO La Silla 3.6m telescope, in addition to many spectra obtained with other instruments. Most Magellan/MIKE spectra were obtained and published by Dupree+ (2012ApJ...750...73D) and Dupree+ (2014ApJ...789...27D), with detailed descriptions of the reductions and calibrations. Most HARPS, VLT/UVES, and FEROS spectra were automatically reduced and then downloaded from the ESO archive. Of the FEROS spectra, 54 spectra were reduced and published by Alencar & Batalha (2002ApJ...571..378A) and Batalha+ (2002ApJ...580..343B). Most Keck/HIRES spectra were obtained from the Keck Observatory Archive. The VLT/ESPRESSO data were obtained as part of the PENELLOPE program, with the reduction described in Manara+ (2021A&A...650A.196M). We also obtained high-resolution spectra with CHIRON, a bench-mounted, fiber-fed, cross-dispersed echelle spectrograph on the 1.5m telescope at the Cerro Tololo Inter-American Observatory (CTIO) and is part of the Small and Moderate Aperture Research Telescope System (SMARTS). This paper uses almost all high-resolution spectra that we could find that cover <6000{AA} and had available, high-quality reductions. See Section 3 and Table 1. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 11 01 51.90 -34 42 17.0 TW Hya = V* TW Hya ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 119 15 Summary of instruments table5.dat 51 1169 Veiling and accretion measurements fig1.dat 77 179932 Coadded ESPaDOnS spectra of TW Hya (see Appendix A) -------------------------------------------------------------------------------- See also: III/174 : High Resolution Atlas of Symbiotic Stars (Van Winckel+ 1993-1994) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) I/350 : Gaia EDR3 (Gaia Collaboration, 2020) II/362 : i-band variability of YSOs (Sergison+, 2020) J/A+AS/101/485 : Multisite UBVRI photometry in Tau-Aur cloud (Bouvier+ 1993) J/ApJ/686/1195 : IR photometry in the {gamma} Vel cluster (Hernandez+, 2008) J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009) J/ApJ/745/119 : Close companions to young stars. I. ChaI & Tau (Nguyen+, 2012) J/A+A/551/A107 : X-shooter spectra of 24 young stellar objects (Manara+, 2013) J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013) J/A+A/561/A2 : 36 accreting YSOs emission lines (Alcala+, 2014) J/AJ/147/82 : Monitoring of disk-bearing stars in NGC 2264 (Cody+, 2014) J/ApJ/784/127 : UV spectra of classical T Tauri stars (France+, 2014) J/ApJ/786/97 : Photospheric properties of T Tauri stars (Herczeg+, 2014) J/A+A/592/A83 : HD 100546 and TW Hya model abundances (Kama+, 2016) J/A+A/600/A20 : Lupus YSOs X-shooter spectroscopy (Alcala+, 2017) J/A+A/602/A33 : X-Shooter spectroscopy of YSOs in Lupus (Frasca+, 2017) J/A+A/632/A46 : TW Hydrae association with X-shooter (Venuti+, 2019) J/A+A/643/A99 : DoAr 44 ugri light curves (Bouvier+, 2020) J/AJ/162/101 : K2 ugri & H{alpha} phot. in the Lagoon Nebula (Venuti+, 2021) J/A+A/667/A124 : GIARPS T Tauri spectra (GHOsT) (Gangi+, 2022) J/AJ/163/263 : 323 YSOs properties with ZTF (Hillenbrand+, 2022) J/AJ/164/201 : Accretion in 9 Orion OB1b T-Tauri stars (Pittman+, 2022) J/ApJ/935/54 : LDT UBVRI photometry of 14 T-Tauri (Robinson+, 2022) J/A+A/672/A5 : GM Aur LCOGT urgi light curves (Bouvier+, 2023) J/AJ/165/269 : TW Hya association candidate members (Luhman, 2023) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 A3 --- Set HRS: high-resolution spectra; or MRS: low- and medium-resolution spectra 5- 17 A13 --- Tel Telescope 19- 27 A9 --- Inst Instrument 29 A1 --- f_Inst Flag on Inst (1) 31- 34 I4 0.1nm lam1 [3000/5000] Wavelength lower range in Angstrom 35 A1 --- --- [-] 36- 40 I5 0.1nm lam2 [5700/25000] Wavelength upper range in {AA} 42 A1 --- f_Range Flag on Range (1) 44- 49 I6 --- Res [1000/140000] Resolution 51 A1 --- f_Res Flag on Res (1) 53- 62 A10 --- Aperture Aperture 64 A1 --- f_Aperture Flag on Aperture (1) 66- 68 A3 --- Sky Sky substraction 70- 72 I3 --- Nsp [1/467] Number of spectra 74- 82 A9 --- Years Observed year(s) 84- 119 A36 --- Ref Instrument reference -------------------------------------------------------------------------------- Note (1): Flag as follows: a = Typical setting, some spectra obtained with other wavelength settings and slit widths. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 11 F11.5 d MJD [51008.9/59698.2] Modified Julian Date 13- 17 F5.3 --- r5050 [0.13/2.13] Veiling from 5000-5100{AA} 19- 23 F5.3 --- e_r5050 [0.002/0.12] Uncertainty in r5050 25- 30 F6.4 Lsun Lum [0.008/0.14] Luminosity 32- 40 E9.3 Msun/yr Mdot [4.6e-10/7.5e-09] Accretion rate 42- 51 A10 --- Inst Instrument (1) -------------------------------------------------------------------------------- Note (1): Instrument as follows: 2dcoude = McDonald 2.7m 2D-Coude (4 occurrences) chiron = SMARTS CHIRON (68 occurrences) ctio = CTIO 4m Echelle spectrograph (1 occurrences) espadons = CFHT ESPaDOnS (284 occurrences) espresso = VLT ESPRESSO (5 occurrences) feros = ESO-MPG 2.2m FEROS (241 occurrences) harps = ESO 3.6m HARPS (34 occurrences) hires = Keck I HIRES (18 occurrences) mike = Magellan MIKE-red spectrograph (467 occurrences) uves = VLT UVES (44 occurrences) uves-short = (3 occurrences) -------------------------------------------------------------------------------- Byte-by-byte Description of file: fig1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.3 0.1nm lambda [3697.9/10481.5] Wavelength; Angstroms 12- 19 F8.5 --- f0 [-3.32/43.5] Normalized f0 flux density (1) 21- 28 F8.5 --- f1 [-7.25/38.4] Normalized f1 flux density (1) 30- 37 F8.5 --- f2 [-7.98/43.9] Normalized f2 flux density (1) 39- 46 F8.5 --- f3 [-3.57/43.2] Normalized f3 flux density (1) 48- 57 F10.5 --- f4 [-211/43.6] Normalized f4 flux density (1) 59- 68 F10.5 --- f5 [-218.3/268] Normalized f5 flux density (1) 70- 77 F8.5 --- fresid [-9.21/9.61] Residual spectrum (2) -------------------------------------------------------------------------------- Note (1): Coadded spectra (as in Table 10): f0 = average of 14 spectra with relative r_5050_=1.1-1.52 (avg 1.25, highest veiling) f1 = average of 17 spectra with relative r_5050_=0.8-0.85 (avg 0.83) f2 = average of 12 spectra with relative r_5050_=0.6-0.65 (avg 0.62) f3 = average of 11 spectra with relative r_5050_=0.4-0.45 (avg 0.43) f4 = average of 11 spectra with relative r_5050_=0.2-0.25 (avg 0.23) f5 = average of 17 spectra with relative r_5050_=-0.01-0.03 (avg 0.01, lowest veiling) The spectra f0, f1, f2, f3, f4, f5, are calculated by normalizing each spectrum across 25{AA} wavelength ranges and then calculating the average. Note (2): The residual spectrum, is the difference between f0 and f5, after subtracting off the estimated veiling for f0, as: fresid=f0-(f5+r_lambda_)/(1+r_lambda_) where r_lambda_ is the local veiling. -------------------------------------------------------------------------------- History: From electronic version of the journal Licences: cc-by ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Jan-2026