Rotational modulation of spectroscopic Zeeman signatures in low-mass stars
Ryan C. Terrien, Allison Keen, Katy Oda, Winter Parts, Guðmundur Stefánsson, Suvrath Mahadevan, Paul Robertson, Joe P. Ninan, Corey Beard, Chad F. Bender, Willi… 展开作者
Ryan C. Terrien, Allison Keen, Katy Oda, Winter Parts, Guðmundur Stefánsson, Suvrath Mahadevan, Paul Robertson, Joe P. Ninan, Corey Beard, Chad F. Bender, William D. Cochran, Katia Cunha, Scott A. Diddams, Connor Fredrick, Samuel Halverson, Fred Hearty, Adam Ickler, Shubham Kanodia, Jessica E. Libby-Roberts, Jack Lubin, Andrew J. Metcalf, Freja Olsen, Lawrence W. Ramsey, Arpita Roy, Christian Schwab, Verne V. Smith, Ben Turner
Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multi-year near-infrared spectroscopic monitoring of two such stars -- GJ 699 (Barnard's Star) and Teegarden's Star -- carried out with Habitable Zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum with higher amplitudes towards longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Angstrom neutral potassium (K I) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known $145\pm15$ d rotation period of GJ 699, and measure the rotation period of Teegarden's Star to be $99.6\pm1.4$ d. Based on simulations of the K I line and the wavelength-dependence of the line width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the near-infrared for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.
Almost three decades ago, Mathys (1990) demonstrated the importance of studying Ap stars showing resolved Zeeman split Fe II 6147.7 and 6149.2 lines. Such Zeeman split lines can be seen in stars whose projected rotational velocity is sufficiently small and whose magnetic field is strong enough to exceed the rotational Doppler broadening. Observations of resolved Zeeman split lines permit the diagnosis of the average of the modulus of the magnetic field over the visible stellar hemisphere. Although Zeeman splitting is not expected in faster rotating hot massive stars, we have recently been disc…
High-dispersion, archival spectra of magnetic Ap stars with resolved Zeeman components in Stokes I are used to derive a simple relation that can be utilised to estimate the mean surface field strengths of stars with v sin i > 10 km/s. For each star, the mean surface field, as measured from the observed splitting in Fe II at 6149 A, is compared to the differential broadening of spectral lines with large and small Lande factors in order to produce a relation to estimate the field strengths of magnetic stars with unresolved Zeeman patterns. The method is shown to be reliable for rotational veloci…
Aims. The goal of this study is to investigate the small-scale magnetic fields of the two spectroscopic binary T Tauri stars V1878 Ori and V4046 Sgr. This is done to complete the observational characterisation of the surface magnetic fields of these stars because only their large-scale magnetic fields have been studied with Zeeman Doppler imaging (ZDI) so far. Methods. To investigate the small-scale magnetic fields, the differential Zeeman intensification of near-infrared Ti I lines was investigated using high-resolution archival spectra obtained with the ESPaDOnS spectrograph at the CFHT. In …
Direct measurements of the stellar magnetic fields are based on the splitting of spectral lines into polarized Zeeman components. With few exceptions, Zeeman signatures are hidden in data noise and a number of methods have been developed to measure the average, over the visible stellar disk, of longitudinal components of the magnetic field. As to faint stars, at present observable only with low resolution spectropolarimetry, a method is based on the regression of the Stokes V signal against the first derivative of Stokes I. Here we present an extension of this method to obtain a direct measure…
Context. A lot of effort has been put into the detection and determination of stellar magnetic fields using the spectral signal obtained from the combination of hundreds or thousands of individual lines, an approach known as multi-line techniques. However, so far most of multi-line techniques developed that retrieve stellar mean longitudinal magnetic fields recourse to sometimes heavy simplifications concerning line shapes and Zeeman splittings. Aims. To determine stellar longitudinal magnetic fields by means of the Principal Components Analysis and Zeeman Doppler Imaging (PCA-ZDI) multi-line …
High-precision space-based photometry obtained by the \emph{Kepler} and \emph{TESS} missions has revealed evidence of rotational modulation associated with main sequence (MS) A and late-B type stars. Generally, such variability in these objects is attributed to inhomogeneous surface structures (e.g. chemical spots), which are typically linked to strong magnetic fields ($B\gtrsim100\,{\rm G}$) visible at the surface. It has been reported that $\approx44$~per~cent of all A-type stars observed during the \emph{Kepler} mission exhibit rotationally modulated light curves. This is surprising conside…
Efforts to discover and characterize habitable zone planets have primarily focused on Sun-like stars and M dwarfs. K stars, however, provide an appealing compromise between these two alternatives that has been relatively unexplored. Understanding the ultraviolet (UV) environment around such stars is critical to our understanding of their planets, as the UV can drastically alter the photochemistry of a planet's atmosphere. Here we present near-UV and far-UV \textit{Hubble Space Telescope}'s Cosmic Origins Spectrograph observations of 39 K stars at three distinct ages: 40 Myr, 650 Myr, and $\app…
High resolution spectroscopy and spectropolarimetry have been undertaken at the Anglo-Australian Telescope in order to identify suitable targets for magnetic studies of young sun-like stars, for the proxy study of early solar evolution. This study involved the investigation of some variable late F-/early G-type sun-like stars originally identified by the Hipparcos mission. Of the 38 stars observed for this study, HIP 31021, HIP 64732, HIP 73780 were found to be spectroscopic binary stars while HIP 19072, HIP 67651 and HIP 75636 are also likely to be binaries while HIP 33111 could even be a tri…
(Abridged) The goal of this work is to investigate if SiO, H2O and HCN maser emission within the ALMA frequency range can be detected with observable levels of fractional linear polarization in the regime where the Zeeman frequency (gOmega) is greater than the stimulated emission rate (R) and the decay rate of the molecular state (Gamma). We have used a radiative transfer code to calculate the fractional linear polarization as a function of the emerging brightness temperature for a number of rotational transition of SiO, H2O and HCN which have been observed to display maser emission at submill…
We present the most precise to date orbital and physical parameters of the well known short period (P=5.975 d), eccentric (e=0.3) double-lined spectroscopic binary BY Draconis, a prototype of a class of late-type, active, spotted flare stars. We calculate the full spectroscopic/astrometric orbital solution by combining our precise radial velocities (RVs) and the archival astrometric measurements from the Palomar Testbed Interferometer (PTI). The RVs were derived based on the high resolution echelle spectra taken between 2004 and 2008 with the Keck I/HIRES, Shane/CAT/HamSpec and TNG/SARG telesc…
Context. The study of rotational velocity distributions for normal stars requires an accurate spectral characterization of the objects in order to avoid polluting the results with undetected binary or peculiar stars. This piece of information is a key issue in the understanding of the link between rotation and the presence of chemical peculiarities. Aims. A sample of 47 low v sin i A0-A1 stars (v sin i < 65km/s), initially selected as main-sequence normal stars, are investigated with high-resolution and high signal-to-noise spectroscopic data. The aim is to detect spectroscopic binaries and ch…
Massive stars play a key role in the evolution of the Universe. Our goal is to compare observed and predicted properties of single Galactic O stars to identify and constrain uncertain physical parameters and processes in stellar evolution and atmosphere models. We used a sample of 53 objects with spectral types from O3 to O9.7. For 30 of these, we determined the main photospheric and wind parameters, using optical spectroscopy and applying the FASTWIND code. For the remaining objects, literature data, obtained by means of the CMFGEN code, were used instead. The properties of our sample were co…
We investigate the magnetic field at the surface of 48 red giants selected as promising for detection of Stokes V Zeeman signatures in their spectral lines. We use the spectropolarimeters Narval and ESPaDOnS to detect circular polarization within the photospheric absorption lines of our targets and use the least-squares deconvolution (LSD) method. We also measure the classical S-index activity indicator, and the stellar radial velocity. To infer the evolutionary status of our giants and to interpret our results, we use state-of-the-art stellar evolutionary models with predictions of convective…
Previous studies on the rotation of Sun-like stars revealed that the rotational rates of young stars converge towards a well-defined evolution that follows a power-law decay. It seems, however, that some binary stars do not obey this relation, often by displaying enhanced rotational rates and activity. In the Solar Twin Planet Search program we observed several solar twin binaries, and found a multiplicity fraction of $42\% \pm 6\%$ in the whole sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and HIP 103983) clearly exhibit the aforementioned anomalies. We investigated…
We report on new radial velocity measurements of massive stars that are either suspected binaries or lacking prior observations. This is part of a survey to identify and characterize spectroscopic binaries among O-type stars with the goal of comparing the binary fraction of field and runaway stars with those in clusters and associations. We present orbits for HDE 308813, HD 152147, HD 164536, BD-16 4826 and HDE 229232, Galactic O-type stars exhibiting single-lined spectroscopic variation. By fitting model spectra to our observed spectra we obtain estimates for effective temperature, surface gr…
We aim to characterise the surface magnetic fields of a sample of 8 T Tauri stars from high-resolution near-IR spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our goals are 1) to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, 2) to expand the sample of stars with measured surface magnetic field strengths, 3) to investigate possible rotational or long-term magnetic variability by comparing spectral time series of given targets, and 4) to compare the magnetic field modulus <B> tracing small…
Activity correlation and temporal variation of small-scale magnetic fields on young Sun-like stars
Uppsala University（乌普萨拉大学）；Keele University（基尔大学）；Universidade Federal de Minas Gerais（米纳斯吉拉斯联邦大学）；University of Tartu（塔尔图大学）；Universidade do Porto（波尔图大学）；Namzitu astro（Namzitu 天文台）
Phase-resolved observations of the solar-type star Ksi Bootis A were obtained using the NARVAL spectropolarimeter at the Telescope Bernard Lyot (Pic du Midi, France) during years 2007, 2008, 2009 and 2010. The data sets enable us to study both the rotational modulation and the long-term evolution of various magnetic and activity tracers. Here, we focus on the large-scale photospheric magnetic field (reconstructed by Zeeman-Doppler Imaging), the Zeeman broadening of the FeI 846.84 nm magnetic line, and the chromospheric CaII H and H alpha emission.
Magnetic fields in cool stars are ubiquitous but can still be challenging to characterize due to their complexity and relatively low strength. The polarization signature amplitudes are proportional to the field strength, and current studies of cool star magnetic fields are using circular polarization only since linear polarization is even weaker. However, circular polarization is only sensitive to the line-of-sight component of the magnetic field, meaning that many structural features are not recovered or may be misinterpreted when only circular polarization is used for reconstruction of stell…
Rotation is of key importance for the evolution of hot massive stars, however, the rotational velocities of these stars are difficult to determine. Based on our own data for 31 Galactic O stars and incorporating similar data for 86 OB supergiants from the literature, we aim at investigating the properties of rotational and extra line-broadening as a function of stellar parameters and at testing model predictions about the evolution of stellar rotation. Fundamental stellar parameters were determined by means of the code FASTWIND. Projected rotational and extra broadening velocities originate fr…
New magnetic Ap stars with split Zeeman components are presented. These stars were discovered from observations with the FEROS spectrograph at the ESO 2.2-m telescope. Fifteen new magnetic stars are analysed here. Several stars with very strong magnetic fields were found, including HD\,70702 with a 15-kG, and HD\,168767 with a 16.5-kG magnetic field strength measured using split Zeeman components of spectral lines and by comparison with synthetic calculations. The physical parameters of the stars were estimated from photometric and spectroscopic data. Together with previously published results…
We report spectroscopic observations of 23 candidates for Kepler asteroseismic targets and 10 other stars in the Kepler field, carried out at two observatories (see the footnote). For all these stars, we derive the radial velocities, effective temperature, surface gravity, metallicity, the projected rotational velocity, and estimate the MK type. HIP 97513 and HIP 92132 are classified as suspected new single-lined spectroscopic binaries. For 28 stars, the radial velocity is measured for the first time.
We have determined spectroscopic orbits for five single-lined spectroscopic binaries, HD 100167, HD 135991, HD 140667, HD 158222, HD 217924. Their periods range from 60.6 to 2403 days and the eccentricities, from 0.20 to 0.84. Our spectral classes for the stars confirm that they are of solar type, F9 to G5, and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are close to the solar value and on average are 0.12 greater than abundances from a photometric calibration. Four of the five stars are rotating faster than their predicted pseudosynchronous rotational velocities.
It has been shown that rotational lines observed in the Horsehead nebula PDR are probably not caused by l-C3H+, as was originally suggested. In the search for viable alternative candidate carriers, quartic force fields are employed here to provide highly accurate rotational constants, as well as fundamental vibrational frequencies, for another candidate carrier: 1 ^1A' C3H-. The ab initio computed spectroscopic constants provided in this work are, compared to those necessary to define the observed lines, as accurate as the computed spectroscopic constants for many of the known interstellar ani…
Stellar rotation is of key importance for the formation process, evolution, and final fate of massive stars. In this paper we review results from the study of the spin rate properties of a sample of more than 400 Galactic O-type stars surveyed by the IACOB and OWN projects. By combining vsini, Teff, and logg estimates (resulting from a detailed quantitative spectroscopic analysis) with information about the spectroscopic binarity status for an important fraction of the stars in the sample, we provide a renewed overview about how the empirical distribution of projected rotational velocities in …
The analysis of Li I 6708A line was performed for 6 rotational phases distributed over the whole rotational period (9.5 years) of HD166473. The magnetic field model was constructed based on the polarimetric measurements from (Mathys et al. 20007). For each observed phase the modulus of the magnetic field was also estimated from simulation of the Fe II 6147A, 6149A and Pr III 6706.7A line profiles taking into account Zeeman magnetic splitting. The lithium abundance in each phase was obtained from fitting the observed Li I 6708A profile with the synthetic one calculated assuming Paschen-Back spl…
It is still unclear how common the Sun is when compared to other similar stars in regards to some of its physical properties, such as rotation. Considering that gyrochronology relations are widely used today to estimate ages of stars in the main sequence, and that the Sun is used to calibrate it, it is crucial to assess if these procedures are acceptable. We analyze the rotational velocities -- limited by the unknown rotation axis inclination angle -- of an unprecedented large sample of solar twins in order to study the rotational evolution of Sun-like stars, and assess if the Sun is a typical…
CP2 stars show periodic photometric, spectroscopic, and magnetic variations with the rotational period. They are generally slow rotators, with rotational periods exceeding half a day, except for the late B-type star HD 60431, which has an unusually short rotational period of 0.4755 days. As slow rotation is deemed a necessary criterion for the establishment of chemical peculiarities, this characteristic renders HD 60431 a special object that might offer valuable insight into, and constraints on, the formation and evolution of CP2 stars. Our study aims at analysing the light variability, derivi…
With new data from the Galactic O-Star Spectroscopic Survey, we confirm and expand the ONn category of late-O, nitrogen-enriched (N), rapidly rotating (n) giants. In particular, we have discovered two "clones" (HD 102415 and HD 117490) of one of the most rapidly rotating O stars previously known (HD 191423, "Howarth's Star"). We compare the locations of these objects in the theoretical HR Diagram to those of slowly rotating ON dwarfs and supergiants. All ON giants known to date are rapid rotators, whereas no ON dwarf or supergiant is; but all ON stars are small fractions of their respective sp…
In eclipsing binaries the stellar rotation of the two components will cause a rotational Doppler beaming during eclipse ingress and egress when only part of the eclipsed component is covered. For eclipsing binaries with fast spinning components this photometric analogue of the well-known spectroscopic Rossiter-McLaughlin effect can exceed the strength of the orbital effect. Example light curves are shown for a detached double white dwarf binary, a massive O-star binary and a transiting exoplanet case, similar to WASP-33b. Inclusion of the rotational Doppler beaming in eclipsing systems is a pr…
The advent of space-based photometry provides the opportunity for the first precise characterizations of variability in Mercury-Manganese (HgMn/CP3) stars, which might advance our understanding of their internal structure. We have carried out a spectroscopic and photometric investigation of the candidate CP3 star KIC 6128830. A detailed abundance analysis based on newly-acquired high-resolution spectra was performed, which confirms that the star's abundance pattern is fully consistent with its proposed classification. Photometric variability was investigated using four years of archival Kepler…
Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. III. Comparison between Starspot Mapping, Zeeman Doppler Imaging, and Multiwavelength Variability
Hitotsubashi University（一桥大学）；The University of Tokyo（东京大学）；The Hakubi Center for Advanced Research, Kyoto University（京都大学博雅研究高级中心）；Department of Physics, Kyoto University（京都大学物理学系）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Department of Physics, The Catholic University of America（美利坚天主教大学物理学系）；Division of Science, National Astronomical Observatory of Japan, NINS（日本国立天文台科学部）；Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES（图卢兹大学、法国国家科学研究中心、法国国家空间研究中心天体物理与行星学研究所在）；Department of Physics, American University（美国大学物理学系）
After a brief introduction into the asteroseismic modelling of stars, we provide a compilation of the current seismic estimates of the core overshooting parameter and of the rotational frequency of single and binary massive stars. These important stellar parameters have meanwhile become available for eleven OB-type stars, among which three spectroscopic pulsating binaries and one magnetic pulsator. We highlight the potential of ongoing and future analyses of eclipsing binary pulsators as essential laboraties to test stellar structure and evolution models of single and binary stars.
We have studied the magnetic field of about 50 active and non-active single G-K-type red giants by means of spectropolarimetry with Narval and ESPaDOnS. 30 giants have been significantly Zeeman-detected. A close study of the 17 giants with known rotational periods shows that the measured magnetic field strength is correlated to the rotation, in particular to the Rossby number. 4 giants for which the magnetic field is measured to be outstandingly strong with respect to the rotational period or the evolutionary state are identified as probable Ap-star descendants. We detail their magnetic proper…
We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed with the FIES spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50 stars. Balmer, Fe I, and Fe II lines were used to derive effective temperatures, surface gravities, and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the…
We present a novel technique that uses the autocorrelation of the spectrum of a star to measure the line broadening caused by the modulus of its average surface magnetic field. The advantage of the autocorrelation comes from the fact that it can detect very small spectral line broadening effects because it averages over many spectral lines and therefore gives an average with a very high signal to noise ratio. We validate the technique with the spectra of known magnetic stars and obtain autocorrelation curves that are in full agreement with published magnetic curves obtained with Zeeman splitti…
By studying young magnetically active late-type stars, i.e. analogues to the young Sun, one can draw conclusions on the evolution of the solar dynamo. We determine the topology of the surface magnetic field and study the relation between the magnetic field and cool photospheric spots in three young late-type stars. High-resolution spectropolarimetry of the targets were obtained with the HARPSpol instrument mounted at the ESO 3.6 m telescope. The signal-to-noise ratio of the Stokes IV measurements were boosted by combining the signal from a large number of spectroscopic absorption lines through…
Methods. We use the code MCFOST to solve the non-LTE problem of line formation in non-axisymmetric accreting magnetospheres. We compute the Brγ line profile originating from accretion columns for models with different magnetic obliquities. We also derive monochromatic synthetic images of the Brγ line emitting region across the line profile. This spectral line is a prime diagnostics of magnetospheric accretion in young stars and is accessible with the long baseline near-infrared interferometer GRAVITY installed at the ESO Very Large Telescope Interferometer. Results. We derive Brγ line profiles…
This is the first in a series of papers in which we describe and report the analysis of a large survey of Herbig Ae/Be stars in circular spectropolarimetry. Using the ESPaDOnS and Narval high-resolution spectropolarimeters at the Canada-France-Hawaii and Bernard Lyot Telescopes, respectively, we have acquired 132 circularly-polarised spectra of 70 Herbig Ae/Be stars and Herbig candidates. The large majority of these spectra are characterised by a resolving power of about 65,000, and a spectral coverage from about 3700 ang to 1 micron. The peak SNR per CCD pixel ranges from below 100 (for the f…
We analyze the photometric and spectroscopic variability of the classical T Tauri star V2129 Oph over several rotational cycles to test the dynamical predictions of magnetospheric accretion models. The photometric variability and the radial velocity variations in the photospheric lines can be explained by rotational modulation due to cold spots, while the radial velocity variations of the He I (5876 Å) line and the veiling variability are due to hot spot rotational modulation. The hot and cold spots are located at high latitudes and about the same phase, but the hot spot is expected to sit at …
Since solar-like oscillations were first detected in red-giant stars, the presence of non-radial oscillation modes has been debated. Spectroscopic line-profile analysis was used in the first attempt to perform mode identification, which revealed that non-radial modes are observable. Despite the fact that the presence of non-radial modes could be confirmed, the degree or azimuthal order could not be uniquely identified. Here we present an improvement to this first spectroscopic line-profile analysis. Aims: We aim to study line-profile variations of stochastically excited solar-like oscillations…
CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the CARMENES Guaranteed Time Observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 M dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present new high-resolution spectroscopic observations with FEROS, CAFE, and HRS of approximately 500 M dwarfs. For each new observation, we determined its radial velocity and measured its Halpha activity index…
We present projected rotational velocity measurements of the red giant in the symbiotic star MWC 560 (V694 Mon), using the high-resolution spectroscopic observations with the FEROS spectrograph. We find that the projected rotational velocity of the red giant is vsini = 8.2 +/- 1.5 km/s, and estimate its rotational period to be P_rot = 144-306 days. Using the theoretical predictions of tidal interaction and pseudosynchronization, we estimate the orbital eccentricity e=0.68-0.82. We briefly discuss the connection of our results with the photometric variability of the object.
Models of magnetically-driven accretion and outflows reproduce many observational properties of T Tauri stars. This concept is not well established for the more massive Herbig Ae/Be stars. We intend to examine the magnetospheric accretion in Herbig Ae/Be stars and search for rotational modulation using spectroscopic signatures, in this first paper concentrating on the well-studied Herbig Ae star HD101412. We used near-infrared spectroscopic observations of the magnetic Herbig Ae star HD101412 to test the magnetospheric character of its accretion disk/star interaction. We reduced and analyzed 3…
We present Spitzer Space Telescope archival mid-infrared (mid-IR) spectroscopy of a sample of eleven planetary nebulae (PNe). The observations, acquired with the Spitzer Infrared Spectrograph (IRS), cover the spectral range 5.2-14.5 μm that includes the H2 0-0 S(2) to S(7) rotational emission lines. This wavelength coverage has allowed us to derive the Boltzmann distribution and calculate the H2 rotational excitation temperature (Tex). The derived excitation temperatures have consistent values ~900+/-70 K for different sources despite their different structural components. We also report the d…
We present far-IR (57-196 mu) spectra of 21 protostars in the Orion molecular clouds, obtained with the Photodetector Array Camera and Spectrometer (PACS) onboard the Herschel Space observatory, as part of the Herschel Orion Protostar Survey (HOPS) program. We analyzed the CO emission lines (J_up = 14-46) in the PACS spectra, extracted within a projected distance of <= 2000 AU centered on the protostar. The total luminosity of the CO lines observed with PACS (L(CO)) is found to increase with increasing L_bol. The CO rotational temperature implied by the line ratios increases with J, and at lea…
We present a spectroscopic analysis of the most rapidly rotating stars currently known, VFTS 102 ($v_{e} \sin i = 649 \pm 52$ km s$^{-1}$; O9: Vnnne+) and VFTS 285 ($v_{e} \sin i = 610 \pm 41$ km s$^{-1}$; O7.5: Vnnn), both members of the 30 Dor complex in the Large Magellanic Cloud. This study is based on high resolution ultraviolet spectra from HST/COS and optical spectra from VLT X-shooter plus archival VLT GIRAFFE spectra. We utilize numerical simulations of their photospheres, rotationally distorted shape, and gravity darkening to calculate model spectral line profiles and predicted monoc…
Hyperfine-Resolved Rovibrational and Rotational Spectroscopy of OH$^+$ ($X ^3Σ^-$)
I. Physikalisches Institut, Universität zu Köln（科隆大学第一物理研究所）；CAS, Max-Planck-Institut für Extraterristrische Physik（中国科学院，德国马克斯·普朗克地外物理研究所）；Max-Planck-Institut für Radioastronomie（德国马克斯·普朗克射电天文研究所）
结合4 K 22极离子阱装置与高分辨红外和太赫兹辐射源，通过作用光谱方法扩展并精修了OH$^+$的基频振动带和$N=1 \leftarrow 0$转动跃迁的自旋多重态，首次以微波精度测量了$N=2 \leftarrow 1$转动跃迁的自旋多重态，并通过全局拟合改进了OH$^+$的光谱常数。
Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, an extensive spectroscopic study of the whole known O-star population in the association is still lacking. In this work, we created the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing and new spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the distrib…
Aims: We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood which may be used to investigate different aspects of the formation and evolution of the solar neighborhood in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. Methods: We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral ra…
We present the spectroscopic analysis of 333 OB-type stars extracted from VLT-MUSE observations of the central 30 x 30 pc of NGC 2070 in the Tarantula Nebula on the Large Magellanic Cloud, the majority of which are analysed for the the first time. The distribution of stars in the spectroscopic Hertzsprung-Russell diagram (sHRD) shows 281 stars in the main sequence. We find two groups in the main sequence, with estimated ages of 2.1$\pm$0.8 and 6.2$\pm$2 Myr. A subgroup of 52 stars is apparently beyond the main sequence phase, which we consider to be due to emission-type objects and/or signific…
We present a spectroscopic analysis of main sequence (MS) stars in the young globular cluster NGC1818 (age~40 Myrs) in the Large Magellanic Cloud. Our photometric survey on Magellanic Clouds clusters has revealed that NGC1818, similarly to the other young objects with age 600 Myrs, displays not only an extended MS Turn-Off (eMSTO), as observed in intermediate-age clusters (age~1-2 Gyrs), but also a split MS. The most straightforward interpretation of the double MS is the presence of two stellar populations: a sequence of slowly-rotating stars lying on the blue-MS and a sequence of fast rotator…
NGC1850 is the nearest Young Massive Cluster of the Local Group with a mass similar to those of Galactic globular clusters. Recent studies have revealed an extended morphology of its MSTO, which can be interpreted as a spread in either age or internal rotation. An accurate spectroscopic determination of its chemical properties is still missing. We analyse spectra obtained with MUSE in adaptive optics mode of 1167 stars in both components of this cluster (NGC1850A and NGC1850B). Thanks to this dataset, we measure an average metallicity of <[M/H]>=-0.31 +/- 0.01, a mean Ba abundance of <[Ba/Fe]>…
We present the COPS-DIGIT-FOOSH (CDF) Herschel spectroscopy data product archive, and related ancillary data products, along with data fidelity assessments, and a user-created archive in collaboration with the Herschel-PACS and SPIRE ICC groups. Our products include datacubes, contour maps, automated line fitting results, and best 1-D spectra products for all protostellar and disk sources observed with PACS in RangeScan mode for two observing programs: the DIGIT Open Time Key Program (KPOT_nevans_1 and SDP_nevans_1; PI: N. Evans), and the FOOSH Open Time Program (OT1_jgreen02_2; PI: J. Green).…
