Abstract
Cosmic dust plays a dominant role in the universe, especially in the formation of stars and planetary systems. Furthermore, the surface of cosmic dust grains is the benchwork where molecular ...hydrogen and simple organic compounds are formed. We manipulate individual dust particles in a water solution by contactless and noninvasive techniques such as standard optical and Raman tweezers, to characterize their response to mechanical effects of light (optical forces and torques) and to determine their mineral compositions. Moreover, we show accurate optical force calculations in the T-matrix formalism highlighting the key role of composition and complex morphology in the optical trapping of cosmic dust particles. This opens perspectives for future applications of optical tweezers in curation facilities for sample-return missions or in extraterrestrial environments.
We study the rotational dynamics of solid chiral and birefringent microparticles induced by elliptically polarized laser light in optical tweezers. We find that both reflection of left circularly ...polarized light and residual linear retardance affect the particle dynamics. The degree of ellipticity of laser light needed to induce rotations is found. The experimental results are compared with analytical calculations of the transfer of angular moment from elliptically polarized light to chiral birefringent particles.
Abstract
The aim of this work is to characterize the counterpart to the INTErnational Gamma-Ray Astrophysics Laboratory high-mass X-ray binary candidate IGR J19294+1816 so as to establish its true ...nature. We obtained H-band spectra of the selected counterpart acquired with the Near Infrared Camera and Spectrograph instrument mounted on the Telescopio Nazionale Galileo 3.5-m telescope which represents the first infrared spectrum ever taken of this source. We complement the spectral analysis with infrared photometry from UKIDSS, 2MASS, WISE, and NEOWISE data bases. We classify the mass donor as a Be star. Subsequently, we compute its distance by properly taking into account the contamination produced by the circumstellar envelope. The findings indicate that IGR J19294+1816 is a transient source with a B1Ve donor at a distance of d = 11 ± 1 kpc, and luminosities of the order of 1036–37 erg s−1, displaying the typical behaviour of a Be-X-ray binary.
Chirality is one of the most prominent and intriguing aspects of nature, from spiral galaxies down to aminoacids. Despite the wide range of living and non-living, natural and artificial chiral ...systems at different scales, the origin of chirality-induced phenomena is often puzzling. Here we assess the onset of chiral optomechanics, exploiting the control of the interaction between chiral entities. We perform an experimental and theoretical investigation of the simultaneous optical trapping and rotation of spherulite-like chiral microparticles. Due to their shell structure (Bragg dielectric resonator), the microparticles function as omnidirectional chiral mirrors yielding highly polarization-dependent optomechanical effects. The coupling of linear and angular momentum, mediated by the optical polarization and the microparticles chiral reflectance, allows for fine tuning of chirality-induced optical forces and torques. This offers tools for optomechanics, optical sorting and sensing and optofluidics.
Aims. We search for new ultracool dwarfs and report here our observations of 78 ultracool dwarf candidates that have been photometrically selected using the DENIS survey point source catalogue. We ...analyze low-resolution optical spectroscopic observations to estimate spectral types of all candidates. Methods. We derive spectral types for each object using measurements of the PC3 spectral index as defined in Martín et al. They range from M6 to L3. The Hα emission and NaI subordinate doublet (818.3 nm and 819.9 nm) equivalent widths are measured in the spectra to identify young stellar objects. Spectroscopic indices of TiO, VO, CrH, and FeH molecular features are also reported. Results. A rule-of-thumb criterion for selecting young very low-mass objects using the NaI doublet equivalent width is given. It is used to confirm seven new members of the Upper Sco OB association and two new members of the R Cr-A star-forming region. Four of our field objects are also classified as very young, but are not members of any known nearby young association. The frequency of lower-gravity young objects in our field ultracool sample is 8.5%. Our results provide the first spectroscopic classification for 42 ultracool dwarfs in the solar vicinity with spectrophotometric distances in the range 17 pc to 65 pc (3 of them being new L dwarfs within 20 pc).
Extensive optical and near-infrared observations of the Type Ib supernova (SNIb) 1999dn are presented, covering the first year after explosion. These new data turn this object, already considered a ...prototypical SNIb, into one of the best observed objects of its class. The light curve of SN 1999dn is mostly similar in shape to that of other SNeIb but with a moderately faint peak (MV
=−17.2 mag). From the bolometric light curve and ejecta expansion velocities, we estimate that about 0.11 M⊙ of 56Ni were produced during the explosion and that the total ejecta mass was 4-6 M⊙ with a kinetic energy of at least 5 × 1051 erg. The spectra of SN 1999dn at various epochs are similar to those of other stripped envelope SNe showing clear presence of H at early epochs. The high explosion energy and ejected mass, along with the small flux ratio Ca ii/O i measured in the nebular spectrum, together with the lack of signatures of dust formation and the moderate metallicity environment is not inconsistent with a single massive progenitor (M
ZAMS≥ 23-25 M⊙) for SN 1999dn.
Optical tweezers in a dusty universe Polimeno, P.; Magazzù, A.; Iatì, M. A. ...
European physical journal plus,
03/2021, Volume:
136, Issue:
3
Journal Article
Peer reviewed
Open access
Optical tweezers are powerful tools based on focused laser beams. They are able to trap, manipulate, and investigate a wide range of microscopic and nanoscopic particles in different media, such as ...liquids, air, and vacuum. Key applications of this contactless technique have been developed in many fields. Despite this progress, optical trapping applications to planetary exploration are still to be developed. Here we describe how optical tweezers can be used to trap and characterize extraterrestrial particulate matter. In particular, we exploit light scattering theory in the T-matrix formalism to calculate radiation pressure and optical trapping properties of a variety of complex particles of astrophysical interest. Our results open perspectives in the investigation of extraterrestrial particles on our planet, in controlled laboratory experiments, aiming for
space tweezers
applications: optical tweezers used to trap and characterize dust particles in space or on planetary bodies surface.
Aims.Spectroscopic monitoring of BL Lac objects is a difficult task that nonetheless can provide important information on the different components of the active galactic nucleus. Methods.We performed ...optical spectroscopic monitoring of the BL Lac object AO 0235+164 ($z=0.94$) with the VLT and TNG telescopes from Aug. 2003 to Dec. 2004, during an extended WEBT campaign. The flux of this source is both contaminated and absorbed by a foreground galactic system at $z=0.524$, the stars of which can act as gravitational micro-lenses. Results.In this period the object was in an optically faint, though variable state, and a broad $\ion{Mg}{ii}$ emission line was visible at all epochs. The spectroscopic analysis reveals an overall variation in the $\ion{Mg}{ii}$ line flux of a factor 1.9, while the corresponding continuum flux density changed by a factor 4.3. Most likely, the photoionising radiation can be identified with the emission component that was earlier recognised to be present as a UV-soft-X-ray bump in the source spectral energy distribution and that is visible in the optical domain only in very faint optical states. We estimate an upper limit to the broad line region (BLR) size of a few light months from the historical minimum brightness level; from this we infer the maximum amplification of the $\ion{Mg}{ii}$ line predicted by the microlensing scenario. Conclusions.Unless we have strongly overestimated the size of the BLR, only very massive stars could significantly magnify the broad $\ion{Mg}{ii}$ emission line, but the time scale of variations due to these (rare) events would be of several years. In contrast, the continuum flux, coming from much smaller emission regions in the jet, could be affected by microlensing from the more plausible MACHO deflectors, with variability time scales of the order of some months.
ABSTRACT
To date, only 18 exoplanets with radial velocity (RV) semi-amplitude <2 m s−1 have had their masses directly constrained. The biggest obstacle to RV detection of such exoplanets is ...variability intrinsic to stars themselves, e.g. nuisance signals arising from surface magnetic activity such as rotating spots and plages, which can drown out or even mimic planetary RV signals. We use Kepler-37 – known to host three transiting planets, one of which, Kepler-37d, should be on the cusp of RV detectability with modern spectrographs – as a case study in disentangling planetary and stellar activity signals. We show how two different statistical techniques – one seeking to identify activity signals in stellar spectra, and another to model activity signals in extracted RVs and activity indicators – can each enable a detection of the hitherto elusive Kepler-37d. Moreover, we show that these two approaches can be complementary, and in combination, facilitate a definitive detection and precise characterization of Kepler-37d. Its RV semi-amplitude of 1.22 ± 0.31 m s−1 (mass 5.4 ± 1.4 M⊕) is formally consistent with TOI-178b’s $1.05^{+0.25}_{-0.30}$ m s−1, the latter being the smallest detected RV signal of any transiting planet to date, though dynamical simulations suggest Kepler-37d’s mass may be on the lower end of our 1σ credible interval. Its consequent density is consistent with either a water-world or that of a gaseous envelope ($\sim 0.4{{\ \rm per\ cent}}$ by mass) surrounding a rocky core. Based on RV modelling and a re-analysis of Kepler-37 TTVs, we also suggest that the putative (non-transiting) planet Kepler-37e should be stripped of its ‘confirmed’ status.
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