Near-infrared High-resolution Spectroscopy Research Articles

The globular cluster VVV CL002 falling down to the hazardous Galactic centre

Context. The Galactic centre is hazardous for stellar clusters because of the strong tidal force in action there. It is believed that many clusters were destroyed there and contributed stars to the crowded stellar field of the bulge and the nuclear stellar cluster. However, the development of a realistic model to predict the long-term evolution of the complex inner Galaxy has proven difficult, and observations of surviving clusters in the central region would provide crucial insights into destruction processes. Aims. Among the known Galactic globular clusters, VVV CL002 is the closest to the centre, at 0.4 kpc, but has a very high transverse velocity of 400 km s−1. The nature of this cluster and its impact on Galactic astronomy need to be addressed with spectroscopic follow up. Methods. Here we report the first measurements of its radial velocity and chemical abundance based on near-infrared high-resolution spectroscopy. Results. We find that this cluster has a counter-rotating orbit constrained within 1.0 kpc of the centre, and as close as 0.2 kpc at the perigalacticon, confirming that the cluster is not a passerby from the halo but a genuine survivor enduring the harsh conditions of the tidal forces of the Galactic mill. In addition, its metallicity and α abundance ([α/Fe] ≃ +0.4 and [Fe/H] = −0.54) are similar to those of some globular clusters in the bulge. Recent studies suggest that stars with such α-enhanced stars were more common at 3–6 kpc from the centre around 10 Gyr ago. Conclusions. We infer that VVV CL002 was formed outside but is currently falling down to the centre, showcasing a real-time event that must have occurred to many clusters a long time ago.

APERO: A PipelinE to Reduce Observations—Demonstration with SPIRou

With the maturation of near-infrared high-resolution spectroscopy, especially when used for precision radial velocity, data reduction has faced unprecedented challenges in terms of how one goes from raw data to calibrated, extracted, and corrected data with required precisions of thousandths of a pixel. Here we present A PipelinE to Reduce Observations (apero), specifically focused on Spectro Polarimètre Infra ROUge (SPIRou), the near-infrared spectropolarimeter on the Canada–France–Hawaii Telescope (SPectropolarimètre InfraROUge, CFHT). In this paper, we give an overview of apero and detail the reduction procedure for SPIRou. apero delivers telluric-corrected 2D and 1D spectra as well as polarimetry products. apero enables precise stable radial velocity measurements on the sky (via the LBL algorithm), which is good to at least ∼2 m s−1 over the current 5 yr lifetime of SPIRou.

GIARPS High-resolution Observations of T Tauri stars (GHOsT)

Aims. In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we study the accretion properties of 37 classical T Tauri stars of the Taurus-Auriga star-forming region (SFR) with the aim of characterizing their relation with the properties of the central star, with jets and disk winds, and with the global disk structure, in synergy with complementary ALMA millimeter observations. Methods. We derive the stellar parameters, optical veiling, the accretion luminosity (Lacc), and the mass accretion rate (Ṁacc) in a homogeneous and self-consistent way using high-resolution spectra acquired at the Telescopio Nazionale Galileo with the HARPS-N and GIANO spectrographs that are flux-calibrated based on contemporaneous low-resolution spectroscopic and photometric ancillary observations. Results. The Lacc–L*, Ṁacc–M* and Ṁacc–Mdisk relations of the Taurus sample are provided and compared with those of the coeval SFRs of Lupus and Chamaeleon I. We analyzed possible causes for the observed large spreads in the relations. We find that (i) a proper modeling in deriving the stellar properties in highly spotted stars can reduce the spread of the Ṁacc–M* relation, (ii) transitional disks tend to have lower Ṁacc at a given M*, (iii) stars in multiple systems have higher Ṁacc at the same Mdisk, (iv) the Ṁacc versus disk surface density has a smaller spread than the Ṁacc–Mdisk, indicating that opacity effects might be important in the derivation of Mdisk. Finally, the luminosities of the [O i] 630 nm narrow low-velocity component and high-velocity component (HVC) and the deprojected HVC peak velocity were found to correlate with the accretion luminosity. We discuss these correlations in the framework of the currently accepted models of jets and winds. Conclusions. Our results demonstrate the potential of contemporaneous optical and near-infrared high-resolution spectroscopy to simultaneously provide precise measurements of the stellar wind and accretion wind properties of young stars.

Possible Progression of Mass-flow Processes around Young Intermediate-mass Stars Based on High-resolution Near-infrared Spectroscopy. I. Taurus

Abstract We used the WINERED spectrograph to perform near-infrared high-resolution spectroscopy (resolving power R = 28,000) of 13 young intermediate-mass stars in the Taurus star-forming region. Based on the presence of near- and mid-infrared continuum emission, young intermediate-mass stars can be classified into three different evolutionary stages: Phases I, II, and III in the order of evolution. Our obtained spectra (λ = 0.91–1.35 μm) depict He i λ10830 and Pβ lines that are sensitive to magnetospheric accretion and winds. We also investigate five sources each for Pβ and He i lines that were obtained from previous studies along with our targets. We observe that the Pβ profile morphologies in Phases I and II corresponded to an extensive variety of emission features; however, these features are not detected in Phase III. We also observe that the He i profile morphologies are mostly broad subcontinuum absorption lines in Phase I, narrow subcontinuum absorption lines in Phase II, and centered subcontinuum absorption features in Phase III. Our results indicate that the profile morphologies exhibit a progression of the dominant mass-flow processes: stellar wind and probably magnetospheric accretion in the very early stage, magnetospheric accretion and disk wind in the subsequent stage, and no activities in the final stage. These interpretations further suggest that opacity in protoplanetary disks plays an important role in mass-flow processes. Results also indicate that He i absorption features in Phase III sources, associated with chromospheric activities even in such young phases, are characteristics of intermediate-mass stars.

NEAR-INFRARED HIGH-RESOLUTION SPECTROSCOPY OF THE OBSCURED AGN IRAS 01250+2832

We provide a new physical insight on the hot molecular clouds near the nucleus of the heavily obscured AGN IRAS 01250+2832, based on the results of near-infrared high-resolution spectroscopy of gaseous CO ro-vibrational absorption lines with Subaru/IRCS. The detected CO absorption lines up to highly excited rotational levels reveal that hot dense molecular clouds exist around the AGN under the peculiar physical conditions.

Circumstellar envelopes and disks of pre-main sequence stars

The current state of knowledge about circumstellar matter of young stellar objects is briefly reviewed. It appears that some very young stars yet to accrete substantial amounts of mass may be seen through their dusty infalling envelopes even at optical wavelengths, because of the presence of holes or large departures from spherical symmetry in the envelopes. The evidence for this picture is summarized in the context of one well-studied young star, HL Tau, indicating that much of the large-scale structure originally identified as a rotating disk is probably a flattened infalling envelope. Departures from spherical symmetry in protostellar clouds are likely to lead to quite flattened structures once collapse gets under way, further suggesting that infall in large-scale toroids may be a general feature of low-mass star formation. The best kinematic evidence for Keplerian disk rotation comes from optical and near-infrared high-resolution spectroscopy of the innermost regions of circumstellar disks. Disk masses are uncertain but are likely to be at least the order of “minimum mass” solar nebula models, if not much larger.

Thermal spectroscopy of Neptune: The stratospheric temperature, hydrocarbon abundances, and isotopic ratios

Portions of Neptune's disk-averaged spectrum were observed from the NASA/Infrared Telescope Facility in 1989 and 1990 with a cryogenic echelle array spectrometer, with resolution of ν/ Δν ∼ 10 4. A lower-resolution spectrum (Orton et al. 1990, Icarus 85, 257–265) was used in conjunction with the analysis of these spectra to provide a more reliable absolute intensity calibration. Together, these data imply a stratospheric temperature of 168 K near 1–10 μbar pressure. Considering the infrared data, Voyager UVS experiment, and Earth-based stellar occultation results, we adopt an uncertainty of ±10 K. The temperature profile adopted in this study is consistent with the size and shape of the H 2 J = 3−1 quadrupole feature which was detected in emission. The maximum mixing ratios of CH 4, C 2H 2, and C 2H 6 which are consistent with this temperature and its uncertainty are 7.5 −5.6 +18.6 × 10 −4, 5.1 −4.3 +2.0 × 10 −8, and 1.0 −0.8 +0.2 × 10 −6, respectively. These C 2H 2 and C 2H 6 abundances are completely consistent with previous measurements, after correcting for different temperature profile assumptions. The combined measurements imply a CH 3D/CH 4 ratio of 3.6 ± 0.5 × 10 −4, from which we deduce D/H = 1.13 ± 0.16 × 10 −4; this is enhanced with respect to solar values and consistent with near-infrared high-resolution spectroscopy (deBergh et al. 1990, Astrophys. J. 355, 661–666). High-resolution measurements of 13C 12CH 6 and 12C 2H 6 imply that 12C/ 13C = 78 ± 26, consistent with solar and telluric values.