Search

Through an optical campaign performed at four telescopes located in the northern and southern hemispheres, we have obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 54-month Palermo BAT catalogue. All these objects also have observations taken with the Swift/XRT, ROSAT, or Chandra satellites, which allowed us to reduce the high-energy error box and pinpoint the most likely optical counterpart(s). We found that 69 sources in our sample are active galactic nuclei (AGNs) of which, 35 are classified as type 1 (with broad and narrow emission lines), 33 are classified as type 2 (with only narrow emission lines), and one is a high-redshift quasi-stellar object; the remaining 6 objects are galactic cataclysmic variables. Of the type 1 AGNs, 32 are objects of intermediate Seyfert type (1.2-1.9) and one is narrow-line Seyfert 1 galaxy; for 29 of the 35 type 1 AGNs, we have been able to estimate the central black hole mass and the Eddington ratio. Of the type 2 AGNs, two display optical features typical of the low-ionization nuclear emission-line region class, three are classified as transition objects, one is a starburst galaxy, and two are X-ray bright, optically normal galaxies. All galaxies classified in this work are relatively nearby objects (0.006-0.213) except for one at redshift 1.137. [ABSTRACT FROM AUTHOR]

We present VLT/X-shooter observations of a sample of 36 accreting low-mass stellar and substellar objects (YSOs) in the Lupus star-forming region, spanning a range in mass from ~0.03 to ~1.2 M, but mostly with 0.1 M☉ < M⋆ < 0.5 M☉. Our aim is twofold: firstly, to analyse the relationship between excess-continuum and line emission accretion diagnostics, and, secondly, to investigate the accretion properties in terms of the physical properties of the central object. The accretion luminosity (Lacc), and in turn the accretion rate ( Ṁacc), was derived by modelling the excess emission from the UV to the near-infrared as the continuum emission of a slab of hydrogen. We computed the flux and luminosity (Lline) of many emission lines of H, He, and Ca II, observed simultaneously in the range from ~330 nm to 2500 nm. The luminosity of all the lines is well correlated with Lacc. We provide empirical relationships between Lacc and the luminosity of 39 emission lines, which have a lower dispersion than relationships previously reported in the literature. Our measurements extend the Paβ and Brγ relationships to Lacc values about two orders of magnitude lower than those reported in previous studies. We confirm that different methodologies of measuring Lacc and Ṁacc yield significantly different results: Hα line profile modelling may underestimate Ṁacc by 0.6 to 0.8 dex with respect to Ṁacc derived from continuum-excess measures. These differences may explain the probably spurious bi-modal relationships between Ṁacc and other YSOs properties reported in the literature. We derived Ṁacc in the range 2 × 10-12-4 × 10-8 M☉ yr-1 and conclude that Ṁacc ∝ M⋆ 1.8(±0.2), with a dispersion lower by a factor of about 2 than in previous studies. A number of properties indicate that the physical conditions of the accreting gas are similar over more than 5 orders of magnitude in Ṁacc, confirming previous suggestions that the geometry of the accretion flow controls the rate at which the disc material accretes onto the central star. [ABSTRACT FROM AUTHOR]

Aims. During a full line survey towards IRC+10420 in the 3 and 1mm bands, we detected the emission of circumstellar nitric oxide for the first time. We aim to study the formation of NO and to confirm the enrichment of nitrogen expected for the most massive, evolved stars predicted by the hot bottom burning process. Methods. We counted on a detailed model of the structure and kinematics of the molecular gas around IRC+.10420. In addition, we used a chemical model to derive the NO abundance profile. We modified the initial nitrogen abundance in order to fit the observed NO profiles. These synthetic profiles were obtained using an LVG radiative transfer code. Results. We have detected NO in a circumstellar envelope for the first time, along with a variety of N-rich molecules, which in turn shows that IRC+10420 presents a N-rich chemistry. Furthermore, we have found that to reproduce the observed NO line profiles, the initial abundance of nitrogen in the chemical model has to be increased by a factor 20 with respect to the values of the standard O-rich stars. [ABSTRACT FROM AUTHOR]

Aims. We present an overview of the UV spectral properties of old novae as a class. The data and results of this paper, together with data from the outburst phases, will be utilized in a follow-up study to determine statistical properties and to investigate correlations among the physical parameters of the quiescent and eruptive phases. Methods. All the available IUE, HST, and FUSE archive data for 18 old novae were used to derive accurate and homogeneous estimates of the reddening from the 2175 Å extinction bump and to determine the intrinsic spectral energy distribution corresponding to the utilization of both existing extinction curves. We also measured all the emission and absorption lines. Results. We have found good agreement between spectra taken at different epochs and by different instruments, a clear indication of the near constancy of the SED on timescales of several years. With the possible exception of GK Per, the dereddened UV continua are represented well by a single-curve power-law distribution Fλ ∝λ-α, with α in the range 0.32-2.55 for one curve and 0.35-2.88 for the other one. The extrapolation of the various UV power laws to the optical range yields values that are in good agreement with the V magnitudes. We interpret this result as evidence that the SED is dominated by the accretion disk in the UV and optical spectral regions. A detailed study of the emission spectrum has led to measuring and identifying more than one hundred features and to detecting several lines that are rather uncommon in other CVs and whose identification is uncertain. [ABSTRACT FROM AUTHOR]

Context. Aminoacetonitrile has been detected in the interstellar medium, and the Strecker-type synthesis is considered as one of its possible formation mechanisms in this medium. Methyleneaminoacetonitrile (CH2NCH2CN, MAAN) is one of the by-products of the Strecker reaction and a good candidate for astrophysical detection. Aims. The rotational spectrum of MAAN has never been studied before. To provide the basis for MAAN detection in the interstellar medium we studied its millimeter- and submillimeter-wave spectrum. Methods. The rotational spectrum of MAAN was measured in the frequency range of 120-600 GHz. The spectroscopic study was supported by theoretical calculations of the molecular structure and harmonic force field. Results. The ground- and the two lowest excited vibrational states of the most stable synperiplanar conformation of MAAN were assigned and analyzed. The obtained sets of rotational constants allow us to accurately predict the transition frequencies of MAAN in the frequency range up to 900 GHz. [ABSTRACT FROM AUTHOR]

Context. The discovery of amino acids in meteorites fallen to Earth and the detection of glycine, the simplest of them, in samples returned from a comet to Earth strongly suggest that the chemistry of the interstellar medium is capable of producing such complex organic molecules and that they may be widespread in our Galaxy. Aims. Our goal is to investigate the degree of chemical complexity that can be reached in the interstellar medium, in particular in dense star-forming regions. Methods. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M), two regions where high-mass stars are formed, with the IRAM 30 m telescope in the 3 mm atmospheric transmission window. Partial surveys at 2 and 1.3 mm were performed in parallel. The spectra were analyzed with a simple radiative transfer model that assumes local thermodynamic equilibrium but takes optical depth effects into account. Results. About 3675 and 945 spectral lines with a peak signal-to-noise ratio higher than 4 are detected at 3 mm toward Sgr B2(N) and (M), i.e. about 102 and 26 lines per GHz, respectively. This represents an increase by about a factor of two over previous surveys of Sgr B2. About 70% and 47% of the lines detected toward Sgr B2(N) and (M) are identified and assigned to 56 and 46 distinct molecules as well as to 66 and 54 less abundant isotopologues of these molecules, respectively. In addition, we report the detection of transitions from 59 and 24 catalog entries corresponding to vibrationally or torsionally excited states of some of these molecules, respectively, up to a vibration energy of 1400 cm-1 (2000 K). Excitation temperatures and column densities were derived for each species but should be used with caution. The rotation temperatures of the detected complex molecules typically range from ~50 to 200 K. Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl formate were reported for the first time in space based on this survey, as were five rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We also report the detection of transitions from within twelve new vibrationally or torsionally excited states of known molecules. Absorption features produced by diffuse clouds along the line of sight are detected in transitions with low rotation quantum numbers of many simple molecules and are modeled with ~30-40 velocity components with typical linewidths of ~3-5 km s-1. Conclusions. Although the large number of unidentified lines may still allow future identification of new molecules, we expect most of these lines to belong to vibrationally or torsionally excited states or to rare isotopologues of known molecules for which spectroscopic predictions are currently missing. Significant progress in extending the inventory of complex organic molecules in Sgr B2(N) and deriving tighter constraints on their location, origin, and abundance is expected in the near future thanks to an ongoing spectral line survey at 3 mm with ALMA in its cycles 0 and 1. The present single-dish survey will serve as a solid basis for the line identification and analysis of such an interferometric survey. [ABSTRACT FROM AUTHOR]

Aims. We would like to understand the chemistry of dense clouds and their hot cores more quantitatively by obtaining more complete knowledge of the chemical species present in them. Methods. We have obtained high-resolution infrared absorption spectroscopy at 3-4 μm toward the bright infrared source CRL 2136. Results. The fundamental vibration-rotation band of HCl has been detected within a dense cloud for the first time. The HCl is probably located in the warm compact circumstellar envelope or disk of CRL 2136. The fractional abundance of HCl is (4.9-8.7) × 10-8, indicating that approximately 20% of the elemental chlorine is in gaseous HCl. The kinetic temperature of the absorbing gas is 250 K, half the value determined from infrared spectroscopy of 13CO and H2O. The percentage of chlorine in HCl is approximately that expected for gas at this temperature. The reason for the difference in temperatures between the various molecular species is unknown. [ABSTRACT FROM AUTHOR]

We retrieved optical-depth spectra of the Titanian haze in the range 1-5 μm from solar occultation data obtained by the Cassini/Visual Infrared Mapping Spectrometer (VIMS) at altitudes of 59-502 km. Only limited wavelength intervals within this spectral range have been analyzed before. The haze spectra we retrieved are mostly similar to those of alkane particles (or powders), with three major absorption peaks typical of alkane powders at 2.3, 3.4, and 4.3 μm. This result suggests that at least in the ~60-500 km altitude range, the Titanian haze is mostly composed of alkane particles, possibly with some trace impurities. The absence of the 3.0 and 4.6 μm features excludes the molecules containing NH and CN bonds that are typical of laboratory-made tholins reported in the literature. The alkane-like spectral characteristics of the haze we observed at ~60-500 km differ from previous results obtained at different or overlapping altitudes: a) the presence of aromatic compounds derived from solar-pumped emissions observed at high altitude (600-1250 km) by Cassini/VIMS near 3.3 μm; and b) the detection of HCN and NH3 in the cores of haze particles collected at low altitude (20-130 km) by the Huygens/Aerosol Collector and Pyrolyser (ACP). We suggest that these different characteristics arise from different structural layers formed by coagulation/coalescence during particle sedimentation. [ABSTRACT FROM AUTHOR]

Context. Circumstellar disc evolution is paramount for the understanding of planet formation. The gas in protoplanetary discs large program (GASPS) aims at determining the circumstellar gas and solid mass around ∼250 pre-main-sequence Herbig Ae and T Tauri stars. Aims. We aim to understand the origin and nature of the circumstellar matter orbiting 51 Oph, a young (<1 Myr) luminous B9.5 star. Methods. We obtained continuum and line observations with the PACS instrument on board the Herschel Space Observatory and continuum data at 1.2 mm with the IRAM 30 m telescope. The spectral energy distribution and line fluxes were modelled using the physico-chemo radiative transfer code ProDiMo to constrain the gas and solid mass of the disc around 51 Oph. The disc vertical hydrostatic structure was computed self-consistently together with the gas thermal balance. Results. We detected a strong emission by atomic oxygen [Oi] at 63 microns using the Herschel Space Observatory. The [Oi] emission at 145 microns, the [Cii] emission at 158 microns, the high-J CO emissions, and the warm water emissions were not detected. Continuum emission was detected at 1.2 mm. The continuum from the near- to the far-infrared and the [Oi] emission are well explained by the emission from a compact (Rout = 10-15 AU) hydrostatic disc model with a gas mass of 5 × 10-6 M☉, 100 times that of the solid mass. However, this model fails to match the continuum millimeter flux, which hints at a cold outer disc with a mass in solids of ∼10-6 M☉ or free-free emission from a photoevaporative disc wind. This outer disc can either be devoid of gas and/or is too cold to emit in the [Oi] line. A very flat extended disc model (Rout = 400 AU) with a fixed vertical structure and dust settling matches all photometric points and most of the [Oi] flux. Conclusions. The observations can be explained by an extended flat disc where dust grains have settled. However, a flat gas disc cannot be reproduced by hydrostatic disc models. The low mass of the 51 Oph inner disc in gas and dust may be explained either by the fast dissipation of an initial massive disc or by a very small initial disc mass. [ABSTRACT FROM AUTHOR]

We present results of near-infrared (near-IR) JHK (1.07 - 2.5/µm) spectroscopic and photometric observations of Nova V476 Scuti (V476 Sct) which was discovered in outburst in 2005 September. The near-IR observations of the nova presents the evolution of the post-maxima spectra and near-IR light curve. The spectra of V476 Sct, observed on 9 different epochs, show prominent lines due to HI, OI, CI and NI. Based on the IR spectral signatures we independently identify it as a Fe II type of nova, consistent with the same classification obtained from optical spectra. A detailed identification of the observed spectral lines is presented. The near-IR JHK light curve extending for a period of about 59 days after outburst clearly shows the formation of a optically thin dust shell, a phenomenon which is not commonly observed in novae. By fitting black body curves to the spectral energy distributions (SEDs) the temperatures of the dust shell on different epochs have been estimated. Dust formation in V476 Sct is consistent with the presence of lines of elements with low-ionization potential like Na and Mg in the early spectra which had earlier been suggested by us to be potential indicators of dust formation at a later phase in a nova's development. [ABSTRACT FROM AUTHOR]

We present a spectral line survey of the protoplanetary nebula (PPN) AFGL 2688 in the frequency ranges of 71-111 GHz, 157-160 GHz, and 218-267 GHz using the Arizona Radio Observatory 12 m telescope and the Heinrich Hertz Submillimeter Telescope. A total of 143 individual spectral features associated with 32 different molecular species and isotopologues were identified. The molecules C3H, CH3CN, H2CO, H2CS, and HCO+ were detected for the first time in this object. By comparing the integrated line strengths of different transitions, we are able to determine the rotation temperatures, column densities, and fractional abundances of the detected molecules. The C, O, and N isotopic ratios in AFGL 2688 are compared with those in IRC+10216 and the Sun, and were found to be consistent with stellar nucleosynthesis theory. Through comparisons of molecular line strengths in asymptotic giant branch stars, PPNs, and planetary nebulae, we discuss the evolution in circumstellar chemistry in the late stages of evolution. [ABSTRACT FROM AUTHOR]

Context. Sulfur emission lines in the soft X-ray and extreme-ultraviolet regions are observed in a variety of laboratory and astrophysical spectra. But accurate electron impact excitation data for S XIII for state-of-the-art NLTE spectral models are scarce. Aims. We calculated electron-impact excitation collision strengths and effective collision strengths of S XIII for transitions among the lowest-lying 98 fine-structure states 1s22lnl′ corresponding to principal quantum numbers n = 2, 3, 4. The effective collision strengths for these transitions were computed over a wide temperature range (log10 Te (K) = 4.53-7.53) for various astrophysical plasma conditions. Methods. We used the fully-relativistic parallel Dirac R-matrix code to calculate collision strengths. To generate target wavefunctions and energy levels for scattering calculations, we employed the GRASP0 multi-configuration Dirac-Fock code for states up to n = 5. Results. The wavefunctions are generated from 27 configurations - 1s22lnl′ (n = 2, 3, 4, 5) - giving rise to 166 j j energy levels. The collision and effective collision strengths among the lowest 98 fine-structure levels are compared with the previous theoretical calculations. The collision strengths for most transitions agree well at higher incident electron energies. Conclusions. The resonant contributions to effective collision strengths are most dominant at lower temperatures. [ABSTRACT FROM AUTHOR]

Context. Observations of the circumstellar envelopes of post-asymptotic giant branch (post-AGB) stars provide information about their mass-loss history during the AGB phase and about the chemistry inside envelopes after that phase. Aims. We analyze visual observations of C2 molecule in absorption and millimeter and sub-millimeter observations of CO molecule in emission with the aim of determining the physical and chemical conditions in the circumstellar shell of the carbon-rich post-AGB star IRAS 22272+5435. Methods. We determined the column densities and excitation structure of C2 from equivalent width analysis of the molecular absorptions. The thermal and density structure of post-AGB shell (AGB remnant) is constrained by multilevel radiative transfer modeling of CO emission lines. The chemical structure of the envelope was computed and then used in the multilevel radiative transfer in C2 for comparison with observed column densities. Results. We estimate the column density of C2 to be 3.2 × 1015 cm-2. From the chemical model we estimate peak abundance of C2 as 6.8 × 10-6 relative to nucleon density. The absorption of molecular lines originate in the ring between 5 and 10 × 1016 cm. The excitation temperature of the lowest levels of 58 K is consistent with the gas kinetic temperature derived from the CO modeling. The initial abundance of the parent molecule C2H2 inferred from the analysis is found to be 1.27 × 10-5 relative to nucleon density. Conclusions. C2 molecule is a promising tool for probing the temperature structure of the envelopes of post-AGB objects and indirectly for determining the chemical abundance of acetylene. [ABSTRACT FROM AUTHOR]

We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitess grism spectroscopic data obtained with the Advanced Camera for Surveys on board Hubble Space Telescope. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random survey of galaxies, as well as the availability of a wide variety of ancillary observations complemented by the spectroscopic results. Using the PEARS data, we are able to identify star-forming galaxies (SFGs) within the redshift volume 0 < z < 1.5. Star-forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allows us to detect the presence of multiple emission-line regions (ELRs) within a single galaxy. We identified a total of 1162 Hα, [OIII], and/or [O II] emission lines in the PEARS sample of 906 galaxies to a limiting flux of ~10-18 erg s-1 cm-2. The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis, we find three key results: (1) the computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; (2) the star-forming systems show evidence of complex morphologies with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass. (3) Also, the number density of SFGs with M" ⩾ 109 M☉ decreases by an order of magnitude at z ⩽ 0.5 relative to the number at 0.5 < z <0.9, supporting the argument of galaxy downsizing. [ABSTRACT FROM AUTHOR]

An assessment of the in-flight radiometric calibration of the Hinode EUV Imaging Spectrometer (EIS) is presented. This is done with the line ratio technique applied to a wide range of observations of the quiet Sun, active regions, and flares from 2006 until 2012. The best diagnostic lines and the relevant atomic data are discussed in detail. Radiances over the quiet Sun are also considered, with comparisons with previous measurements. Some departures in the shapes of the ground calibration responsivities are found at the start of the mission. These shapes do not change significantly over time, with the exception of the shorter wavelengths of the EIS short-wavelength (SW) channel, which shows some degradation. The sensitivity of the SW channel at longer wavelengths does not show significant degradation, while that of the long-wavelength (LW) channel shows a significant degradation with time. By the beginning of 2010 the responsivity of the LW channel was already lower than the values measured on the ground by a factor of two or more. A first-order correction is proposed. With this correction, the main ratios of lines in the two channels become constant to within a relative 20%, and the He ii 256 Å radiances over the quiet Sun also become constant over time. This correction removes long-standing discrepancies for a number of lines and ions, in particular those involving the strongest Fe x, Fexiii, Fexiv, Fexvii, and Fe xxiv lines, where discrepancies of factors of more than two were found. These results have important implications for various EIS science analyses, in particular for measurements of temperatures, emission measures and elemental abundances. [ABSTRACT FROM AUTHOR]

This paper outlines the rather narrow conditions on a radiatively decoupled plasma where a Maxwell-Boltzmann (MB) distribution can be assumed with confidence. The complementary non-thermal distribution with nonperturbative kurtosis is argued to have a much broader purview than has previously been accepted. These conditions are expressed in terms of the electron Knudsen number, Ke, the ratio of the electron mean free path to the scale length of electron pressure. Rather generally, f (v < v2(Ke)) will be Gaussian, so that MB atomic or wave particle effects controlled by speeds v < v2 = w(15/8Ke)1/4 will remain defensible, where w is the most probable speed. The sufficient condition for Spitzer-Braginskii plasma fluid closure at the energy equation requires globally Ke(s) ⩽ 0.01; this global condition pertains to the maximum value of Ke along the arc length s of the magnetic field (to its extremities) provided that contiguous plasma remains uncoupled from the radiation field. The non-thermal regime Ke > 0.01 is common in all main-sequence stellar atmospheres above approximately 0.05 stellar radii from the surface. The entire solar corona and wind are included in this regime where non-thermal distributions with kurtosis are shown to be ubiquitous, heat flux is not well modeled by Spitzer-Braginskii closure, and fluid modeling is qualitative at best. [ABSTRACT FROM AUTHOR]

We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z ≳ 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays.We identify a total of 11 possible absorption lines, with single-line statistical significances between 2.2σ and 4.1σ. Six of these lines are detected at high single-line statistical significance (3.6⩽ σ ⩽ 4.1), while the remaining five are regarded as marginal detections in association with either other X-ray lines detected at higher significance and/or far-ultraviolet (FUV) signposts. Three of these lines are consistent with metal absorption at z ≃ 0, and we identify them with Galactic Oi and C ii. The remaining eight lines may be imprinted by intervening absorbers and are all consistent with being high-ionization counterparts of FUV Hi and/or Ovi intergalactic medium signposts. In particular, five of these eight possible intervening absorption lines (single-line statistical significances of 4.1σ, 4.1σ, 3.9σ, 3.8σ, and 2.7σ), are identified as Cv and C vi Kα absorbers belonging to three WHIM systems at zX = 0.312, zX = 0.237, and = 0.133, which also produce broad Hi (and Ovi for the zX = 0.312 system) absorption in the FUV. For two of these systems (zX = 0.312 and 0.237), the Chandra X-ray data led the a posteriori discovery of physically consistent broad Hi associations in the FUV (for the third system the opposite applies), so confirming the power of the X-ray-FUV synergy forWHIM studies. The true statistical significances of these three X-ray absorption systems, after properly accounting for the number of redshift trials, are 5.8σ (zX = 0.312; 6.3σ if the low-significance Ov and C v Kβ associations are considered), 3.9σ (zX = 0.237), and 3.8σ ( = 0.133), respectively. [ABSTRACT FROM AUTHOR]

The 557.7 nm green line and the 297.2 nm ultraviolet line in oxygen have been studied extensively due to their importance in astrophysics and atmospheric science. Despite the enormous effort devoted to these two prominent transition lines over 30 years, and in fact going back to 1934, the ratio of their transition probabilities remains a subject of major discrepancies amongst various theoretical calculations for many decades. Moreover, theoretical results are inconsistent with available laboratory results, as well as recent spacecraft measurements of Earth's airglow. This work presents new relativistic theoretical calculations of the transition probabilities of these two photoemission lines from neutral oxygen using the multi-configuration Dirac–Hartree–Fock method. Our calculations were performed in both length and velocity gauges in order to check for accuracy and consistency, with agreement to 8%. Whilst remaining a challenging computation, these results directly bear upon interpretations of plasma processes and ionization regimes in the universe. [ABSTRACT FROM AUTHOR]

We present observations with the Very Large Telescope and Hubble Space Telescope (HST) of the broad emission lines from the inner ejecta and reverse shock of SN 1987A from 1999 February until 2012 January (days 4381-9100 after explosion).We detect broad lines from Hα, Hβ,Mg I], Na I, [OI], [Ca II], and a feature at ~9220 Å.We identify the latter line with MgII λλ9218, 9244, which is most likely pumped by Lyα fluorescence. Hα and Hβ both have a centrally peaked component extending to~4500 km s-1 and a very broad component extending to≳11,000 km s-1, while the other lines have only the central component. The low-velocity component comes from unshocked ejecta, heated mainly by X-rays from the circumstellar environment, whereas the very broad component comes from faster ejecta passing through the reverse shock, created by the collision with the circumstellar ring. The flux in Hα from the reverse shock has increased by a factor of four to six from 2000 to 2007. After that there is a tendency of flattening of the light curve, similar to what may be seen in the optical lines from the shocked ring. The core component seen in Hα, [CaII], and MgII has experienced a similar increase, which is consistent with that found from HST photometry. The energy deposition of the external X-rays is calculated using explosion models for SN 1987A and we predict that the outer parts of the unshocked ejecta will continue to brighten because of this. The external X-ray illumination also explains the edge-brightened morphology of the ejecta seen in the HST images. We finally discuss evidence for dust in the ejecta from line asymmetries [ABSTRACT FROM AUTHOR]

Ethyl cyanide, CH3CH2CN, is an important interstellar molecule with a very dense rotational-vibrational spectrum. On the basis of new laboratory data in the range of 17-605 GHz and ab initio calculations, two new vibrational states, v12 and v20, have been detected in molecular clouds of Orion. Laboratory data consist of Stark spectroscopy (17-110 GHz) and frequency-modulated spectrometers (GEM laboratory in Valladolid: 17-170, 270-360 GHz; Toyama: 26-200 GHz; Emory: 200-240 GHz; Ohio State: 258-368 GHz; and JPL: 270-318, 395-605 GHz). More than 700 distinct lines of each species were measured in J up to 71 and in Ka up to 25. The states were fitted with Watson's S-reduction Hamiltonian. The two new states have been identified in the interstellar medium toward the Orion Nebula (Orion KL). The ground state, the isotopologues of CH3CH2CN, and the vibrationally excited states have been fitted to obtain column densities and to derive vibrational temperatures. All together, ethyl cyanide is responsible for more than 2000 lines in the observed frequency range of 80-280 GHz. [ABSTRACT FROM AUTHOR]

The Herschel Space Observatory carried out observations at far-infrared wavelengths, which significantly increased our knowledge of the interstellar medium and the star-formation process in the Milky Way and external galaxies, as well as our understanding of astrochemistry.Absorption features, known, e.g., from observations at millimeter wavelengths, are more commonly observed in the far-infrared, in particular toward strong dust continuum sources. The lowest energy transitions are not only observed at LSR-velocities related to the source, but often also at velocities associated with diffuse molecular clouds along the line of sight toward the background source.Unbiased spectral line surveys of the massive and very luminous Galactic Center sources Sagittarius B2(M) and (N) were carried out across the entire frequency range of the high-resolution Heterodyne Instrument for Far-Infrared Astronomy (HIFI). An absorption feature was detected toward both sources at about 617.531 GHz, corresponding to 20.599 cm−1, 485.47 μm, or 2.5539 meV. This feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the sources themselves. The carriers of at least a substantial part of the DIBs are thought to reside in the diffuse interstellar medium. Therefore, we consider this absorption feature to be a far-infrared DIB analog.Subsequent dedicated observations confirmed that the line is present only in the foreground clouds on the line of sight toward other massive star-forming regions in the Galactic disk. There is indication that the feature has substructure, possibly of fine or hyperfine nature. Attempts to assign the feature to atomic or molecular species have been unsuccessful so far. [ABSTRACT FROM PUBLISHER]

We are using five different surveys to compile the largest sample of diffuse interstellar band (DIB) measurements ever collected. GOSSS is obtaining intermediate-resolution blue-violet spectroscopy of ~2500 OB stars, of which 60% have already been observed and processed. The other four surveys have already collected multi-epoch high-resolution optical spectroscopy of 700 OB stars with different telescopes, including the 9 m Hobby-Eberly Telescope in McDonald Observatory. Some of our stars are highly-extinguished targets for which no good-quality optical spectra have ever been published. For all of the targets in our sample we have obtained accurate spectral types, measured non-DIB ISM lines, and compiled information from the literature to calculate the extinction. Here we present the first results of the project, the properties of twenty DIBs in the 4100-5500 Å range. We clearly detect a couple of previously elusive DIBs at 4170 Å and 4591 Å; the latter could have coronene and ovalene cations as carriers. [ABSTRACT FROM PUBLISHER]

Multiple observations of methanimine (CH2NH) and methyl amine (CH3NH2) have been performed toward Sgr B2(N) at 1, 2, and 3 mm using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. In the frequency range 68-280 GHz, 23 transitions of CH2NH and 170 lines of CH3NH2 have been observed as individual, distinguishable features, although some are partially blended with other lines. For CH2NH, the line profiles indicate VLSR = 64.2 ±1.4 km s-1 and ▵ V1/2 = 13.8 ±2.8 km s-1, while VLSR = 63.7 ± 1.6 km s-1 and ▵ V1/2 = 15.1 ± 3.0 km s-1 for CH3NH2, parameters that are very similar to those of other organic species in Sgr B2(N). From these data, rotational diagrams were constructed for both species. In the case of CH2NH, a rotational temperature of Trot = 44 ± 13 K and a column density of Ntot = (9.1 ± 4.4) × 1014 cm-2 were determined from the analysis. For CH3NH2, Trot = 159 ± 30 K and Ntot = (5.0 ± 0.9) × 1015 cm-2, indicating that this species is present in much warmer gas than CH2NH. The fractional abundances for CH2NH and CH3NH2 were established to be f (H2) ≈ 3.0 × 10-10 and f (H2) ≈ 1.7 × 10-9, respectively. It has been proposed that CH2NH is formed on grains via hydrogenation of HCN; further hydrogenation of CH2NH on surfaces leads to CH3NH2. However, given the dissimilarity between the rotational temperatures and distributions of CH2NH and CH3NH2 in Sgr B2, it is improbable that these species are closely related synthetically, at least in this source. Both CH2NH and CH3NH2 are more likely created by neutral-neutral processes in the gas phase. [ABSTRACT FROM AUTHOR]

Context. One of the big questions in astrochemistry is whether complex organic molecules are formed in the gas phase after evaporation of the icy mantles of interstellar dust grains or at intermediate temperatures within these icy mantles. Dimethyl ether (CH3OCH3) is one of these species that may form through either of these mechanisms, but it is yet unclear which is dominant. Aims. The goal of this paper is to determine the respective importance of solid state vs. gas phase reactions for the formation of dimethyl ether. This is done by a detailed analysis of the excitation properties of the ground state and the torsionally excited states, v11 = 1 and v15 = 1, toward the high-mass star-forming region G327.3-0.6. Methods. With the Atacama Pathfinder EXperiment 12 m submillimeter telescope, we performed a spectral line survey toward G327.3-0.6 around 1.3, 1.0, and 0.9 mm as well as at 0.43 and 0.37 mm. The observed CH3OCH3 spectrum is modeled assuming local thermal equilibrium. Results. CH3OCH3 has been detected in the ground state, v= 0, and in the torsionally excited states v11 = 1 and v15 = 1, for which lines have been detected here for the first time. The emission is modeled with an isothermal source structure as well as with a non-uniform spherical structure. In the isothermal case two components at 80 and 100 K are needed to reproduce the dimethyl ether emission, whereas an abundance jump at 85 K or a model with two abundance jumps at 70 and 100 K fit the emission equally well for the non-uniform source model. The emission from the torsionally excited states, v11 = 1 and v15 = 1, is very well fit by the same model as the ground state. Conclusions. For non-uniform source models one abundance jump for dimethyl ether is sufficient to fit the emission, but two components are needed for the isothermal models. This suggests that dimethyl ether is present in an extended region of the envelope and traces a non-uniform density and temperature structure. Both types of models furthermore suggest that most dimethyl ether is present in gas that is warmer than 100 K, but a smaller fraction of 5%-28% is present at temperatures between 70 and 100 K. The dimethyl ether present in this cooler gas is likely formed in the solid state, while gas phase formation probably is dominant above 100 K. Finally, the v11 = 1 and v15 = 1 torsionally excited states are easily excited under the density and temperature conditions in G327.3-0.6 and will thus very likely be detectable in other hot cores as well. [ABSTRACT FROM AUTHOR]

Context. Dimethyl ether is one of the most abundant complex organic molecules (COMs) in star-forming regions. Like other COMs, its formation process is not yet clearly established, but the relative abundances of its deuterated isotopomers may provide crucial hints in studying its chemistry and tracing the source history. The mono-deuterated species (CH2DOCH3) is still a relatively light molecule compared to other COMs. Its spectrum is the most intense in the THz domain in the 100-150 K temperature regime, tracing the inner parts of the low-mass star-forming region. Therefore, it is necessary to measure and assign its transitions in this range in order to be able to compute accurate predictions required by astronomical observations, in particular with the telescope operating in the submm range, such as ALMA. Aims. We present the analysis of mono-deuterated dimethyl ether in its ground-vibrational state, based on an effective Hamiltonian for an asymmetric rotor molecules with internal rotors. The analysis covers the frequency range 150-990 GHz. Methods. The laboratory rotational spectrum of this species was measured with a submillimeter spectrometer (50-990 GHz) using solid-state sources. For the astronomical detection, we used the IRAM 30 m telescope to observe a total range of 27 GHz, in 4 frequency bands from 100 GHz to 219 GHz. Results. New sets of spectroscopic parameters have been determined by a least squares fit with the ERHAM code for both conformers. These parameters have permitted the first identification in space of both mono-deuterated DME isomers via detection of twenty transitions in the solar-type protostar IRAS 16293-2422 with the IRAM 30 m telescope. The DME deuteration ratio in this source appears as high as observed for methanol and formaldehyde, two species known to play an important role in the COMs formation history. [ABSTRACT FROM AUTHOR]

Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (∼80 per cent) of the targets are YSOs, of which 131 are massive YSOs (LBOL > 5 × 103 L⊙, M > 8 M⊙). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7 < AV < 114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Brγ, H2, fluorescent Fe ii, CO bandhead, [Fe ii] and He i 2–1 1S–1P, in order of frequency of occurrence. In total, ∼40 per cent of the YSOs display either fluorescent Fe ii 1.6878 μm or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ∼60 per cent of the sources exhibit [Fe ii] or H2 emission, indicating the presence of an outflow. Three quarters of all sources have Brγ in emission. A good correlation with bolometric luminosity was observed for both the Brγ and H2 emission line strengths, covering 1 < LBOL < 3.5 × 105 L⊙. This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs. [ABSTRACT FROM PUBLISHER]

We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for Fe xxv Heα and/or Fe xxvi Lyα absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E ≳ 6.7 keV in 20/51 sources at the PMC ≥ 95 per cent level, which corresponds to ∼40 per cent of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to Fe xxv Heα and Fe xxvi Lyα at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the Fe K absorption components are log (NH/cm−2) ≈ 23 and log (ξ/erg cm s−1) ≈ 4.5, respectively. Measured outflow velocities span a continuous range from <1500 km s−1 up to ∼100 000 km s−1, with mean and median values of ∼0.1 c and ∼0.056 c, respectively. The results of this work are consistent with those recently obtained using XMM–Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe. [ABSTRACT FROM AUTHOR]

We present the X-ray spectral results from the longest X-ray Multi-mirror Mission–Newton observation, 133 ks, of the low-luminosity active galactic nucleus NGC 7213. The hardness-ratio analysis of the X-ray light curves discloses a rather constant X-ray spectral shape, at least for the observed exposure time, enabling us to perform X-ray spectral studies using the total observed spectrum. Apart from a neutral Fe Kα emission line, we also detect narrow emission lines from the ionized iron species, Fe xxv and Fe xxvi. Our analysis suggests that the neutral Fe Kα originates from a Compton-thin reflector, while the gas responsible for the high-ionization lines is collisionally excited. The overall spectrum, in the 0.3–10 keV energy band, registered by the European Photon Imaging Camera can be modelled by a power-law component (with a slope of Γ ≃ 1.9) plus two thermal components at 0.36 and 8.84 keV. The low-energy thermal component is entirely consistent with the X-ray spectral data obtained by the Reflection Grating Spectrometer between 0.35–1.8 keV. [ABSTRACT FROM AUTHOR]

Two optically obscured Wolf–Rayet (WR) stars have been recently discovered by means of their infrared (IR) circumstellar shells, which show signatures of interaction with each other. Following the systematics of the WR star catalogues, these stars obtain the names WR 120bb and WR 120bc. In this paper, we present and analyse new near-IR, J-, H- and K-band spectra using the Potsdam Wolf–Rayet model atmosphere code. For that purpose, the atomic data base of the code has been extended in order to include all significant lines in the near-IR bands.The spectra of both stars are classified as WN9h. As their spectra are very similar the parameters that we obtained by the spectral analyses hardly differ. Despite their late spectral subtype, we found relatively high stellar temperatures of 63 kK. The wind composition is dominated by helium, while hydrogen is depleted to 25 per cent by mass.Because of their location in the Scutum–Centaurus Arm, WR 120bb and WR 120bc appear highly reddened, $A_{K_{\rm s}} \approx 2$ mag. We adopt a common distance of 5.8 kpc to both stars, which complies with the typical absolute K-band magnitude for the WN9h subtype of −6.5 mag, is consistent with their observed extinction based on comparison with other massive stars in the region, and allows for the possibility that their shells are interacting with each other. This leads to luminosities of $\log (\mathrm{{\rm \textit {L}}/L}_{\odot }) = 5.66$ and 5.54 for WR 120bb and WR 120bc, with large uncertainties due to the adopted distance.The values of the luminosities of WR 120bb and WR 120bc imply that the immediate precursors of both stars were red supergiants (RSG). This implies in turn that the circumstellar shells associated with WR 120bb and WR 120bc were formed by interaction between the WR wind and the dense material shed during the preceding RSG phase. [ABSTRACT FROM AUTHOR]

We present a study of the accretion flow to the intermittent accreting millisecond pulsar, HETE J1900.1−2455, based on observations made simultaneously by XMM–Newton and RXTE. The 0.33–50 keV energy spectrum is described by the sum of a hard Comptonized component produced in an optically thin τ ≃ 1 corona, a soft thermal kTin ≃ 0.2 keV component interpreted as accretion disc emission, and of disc reflection of the hard component. Two emission features are detected at energies of 0.98(1) and 6.58(7) keV, respectively. The latter is identified as Kα transition of Fe xxiii–xxv. A simultaneous detection in the European Photon Imaging Camera (EPIC-pn), EPIC-MOS2 and Reflection Grating Spectrometer (RGS) spectra favours an astrophysical origin also for the latter, which has an energy compatible with Fe-Lα and helium-like Ne-Kα transitions. The broadness of the two features, σ/E ≃ 0.1, suggests a common origin, resulting from reflection in an accretion disc with inclination of (30+ 4− 3)°, and extending down to Rin = 25+ 16− 11 gravitational radii from the compact object. However, the strength of the feature at lower energy measured by EPIC-pn cannot be entirely reconciled with the amplitude of the Fe-Kα line, hampering the possibility of describing it in terms of a broad-band reflection model, and preventing a firm identification. Pulsations at the known 377.3 Hz spin frequency could not be detected with an upper limit of 0.4 per cent at 3σ confidence level on the pulsed fractional amplitude.We interpret the value of the inner disc radius estimated from spectral modelling and the lack of significant detection of coherent X-ray pulsations as an indication of a disc accretion flow truncated by some mechanism connected to the overall evolution of the accretion disc, rather than by the neutron star magnetic field. This is compatible with the extremely close similarity of spectral and temporal properties of this source with respect to other, non-pulsing atoll sources in the hard state. [ABSTRACT FROM AUTHOR]

We report the first detection of pure rotational transitions of TiO and TiO2 at (sub-)millimeter wavelengths towards the red supergiant VYCMa. A rotational temperature, Trot, of about 250K was derived for TiO2. Although Trot was not well constrained for TiO, it is likely somewhat higher than that of TiO2. The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow. [ABSTRACT FROM AUTHOR]

We present an analysis of the 100 ks X-ray spectrum of the narrow-line Seyfert 1 Galaxy Ark 564, taken with the Low Energy Transmission Grating Spectrometer (LETGS) on board Chandra. Using X2 statistics, several continuum models of the time-averaged spectrum of this object are compared, obtaining a semi-empirical solution for the description of the intrinsic emission continuum and a physical solution for the intrinsic absorption of the system. We find that the 0.1-10 keV spectrum can be well described by a power law plus two thermal components that account for the soft step. We are also able to detect and measure several narrow, unresolved absorption lines arising from highly ionized species of C, N, O, and Fe. The material seems to have a velocity consistent with the systemic velocity of the galaxy. This piece of evidence, in addition to the very low observed column density of NH ~ 1020 cm-2, is in good agreement with the scenario of a transverse biconical outflow with a gas density of n ⩽ 3 × 1012 cm-3at distances beyond the broad-line region r ⩾ 10 lt-days, but a dust torus origin cannot be ruled out. [ABSTRACT FROM AUTHOR]

We present high-resolution (R ~ 15 000) VLT/UVES optical spectra of two planetary nebulae (PNe; Tc 1 and M 1-20) where C60 (and C70) fullerenes have already been found. These spectra are of high quality (S/N > 300) for PN Tc 1, which permits us to search for the expected electronic transitions of neutral C60 and diffuse interstellar bands (DIBs). Surprisingly, we report the non-detection of the most intense optical bands of C60 in Tc 1, although this could be explained by the low C60 column density estimated from the C60 infrared bands if the C60 emission peaks far away from the central star. The strongest and most common DIBs in both fullerene PNe are normal for their reddening. Interestingly, the very broad 4428 Å DIB and the weaker 6309 Å DIB are found to be unusually intense in Tc 1. We also report the detection of a new broad (FWHM ~ 5 Å) unidentified band at ~6525 Å. We propose that the 4428 Å DIB (probably also the 6309 Å DIB and the new 6525 Å band) may be related to the presence of larger fullerenes (e.g., C80, C240, C320, and C540) and buckyonions (multishell fullerenes such as C60@C240 and C60@C240@C540) in the circumstellar envelope of Tc 1. [ABSTRACT FROM AUTHOR]

We use data from the bright atoll source 4U 1705-44 taken with XMM-Newton, BeppoSAX, and RXTE both in the hard and in the soft state to perform a self-consistent study of the reflection component in this source. Although the data from these X-ray observatories are not simultaneous, the spectral decomposition is shown to be consistent among the different observations, when the source flux is similar. We have therefore selected observations performed at similar flux levels in the hard and soft states to study the spectral shape in these two states in a broad-band (0.1-200 keV) energy range, with good energy resolution, and using self-consistent reflection models. These reflection models provide a good fit for the X-ray spectrum both in the hard and in the soft state in the whole spectral range. We discuss the differences in the main spectral parameters we find in both states, providing evidence that the inner radius of the optically thick disk slightly recedes in the hard state. [ABSTRACT FROM AUTHOR]

We report on Herschel/PACS observations of absorption lines of OH+, H2O+ and H3O+ in NGC 4418 and Arp 220. Excited lines of OH+ and H2O+ with Elower of at least 285 and ~200 K, respectively, are detected in both sources, indicating radiative pumping and location in the high radiation density environment of the nuclear regions. Abundance ratios OH+/H2O+ of 1-2.5 are estimated in the nuclei of both sources. The inferred OH+ column and abundance relative to H nuclei are (0.5-1) × 1016 cm-2 and ~2 × 10-8, respectively. Additionally, in Arp 220, an extended low excitation component around the nuclear region is found to have OH+/H2O+ ~ 5-10. H3O+ is detected in both sources with N(H3O+) ~ (0.5-2) × 1016 cm-2, and in Arp 220 the pure inversion, metastable lines indicate a high rotational temperature of ~500 K, indicative of formation pumping and/or hot gas. Simple chemical models favor an ionization sequence dominated by H+ → O+ → OH+ → H2O+ → H3O+, and we also argue that the H+ production is most likely dominated by X-ray/cosmic ray ionization. The full set of observations and models leads us to propose that the molecular ions arise in a relatively low density (≳104 cm-3) interclump medium, in which case the ionization rate per H nucleus (including secondary ionizations) is ς > 10-13 s-1, a lower limit that is several × 102 times the highest current rate estimates for Galactic regions. In Arp 220, our lower limit for ς is compatible with estimates for the cosmic ray energy density inferred previously from the supernova rate and synchrotron radio emission, and also with the expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray ionization due to an active galactic nucleus is responsible for the molecular ion production. [ABSTRACT FROM AUTHOR]

Context. The near-infrared (NIR) wavelength range offers some unique spectral features, and it is less prone to the extinction than the optical one. Recently, the first flux calibrated NIR library of cool stars from the NASA Infrared Telescope Facility (IRTF) have become available, and it has not been fully exploited yet. Aims. We want to develop spectroscopic diagnostics for stellar physical parameters based on features in the wavelength range 1-5 μm. In this work we test the technique in the I and K bands. The study of the Y, J, H, and L bands will be presented in the following paper. Methods. An objective method for semi-empirical definition of spectral features sensitive to various physical parameters is applied to the spectra. It is based on sensitivity map - i.e., derivative of the flux in the spectra with respect to the stellar parameters at a fixed wavelength. New optimized indices are defined and their equivalent widths (EWs) are measured. Results. The method is applied in the I- and K-band windows of the IRTF stellar spectra to verify the new technique by comparing the results with the known behavior of well-studied spectral features. A number of sensitive features to the effective temperature and surface gravity are re-identified or newly identified clearly showing the reliability of the sensitivity map analysis. Conclusions. The sensitivity map allows to identify the best bandpass limits for the line and nearby continuum. It reliably predicts the trends of spectral features with respect to a given physical parameter but not their absolute strengths. Line blends are easy to recognize when blended features have different behavior with respect to some physical stellar parameter. The use of sensitivity map is therefore complementary to the use of indices. We give the EWs of the new indices measured for the IRTF star sample. This new and homogeneous set of EWs will be useful for stellar population synthesis models and can be used to get element-by-element abundances for unresolved stellar population studies in galaxies. [ABSTRACT FROM AUTHOR]

Context. Formamide (HCONH2) is the simplest molecule with a peptide bond detected in the interstellar medium. One of the keys for understanding the mechanisms for forming formamide in massive hot cores is the comparison of the relative abundances of its deuterated isotopologues. Aims. No deuterated species of formamide have been detected to date mostly owing to the lack of laboratory spectral data, which is limited by cm-wave measurements up to 40 GHz. Therefore, we decided to extend the measurements and the analysis of the rotational spectra of deuterated istopologues of formamide into the terahertz range. Methods. We measured the rotational spectra of deuterated formamide in the frequency range 150-950 GHz using the Lille fast-scan and solid-state source spectrometers. Results. The ground vibrational states of 4 different isotopologues of formamide, DCONH2, cis-HCONHD, trans-HCONHD, and HCOND2, were assigned and analysed. The sets of the rotational and centrifugal distortion constants we obtained allow us to calculate accurate predictions of the transition frequencies for deuterated formamide in the frequency range above 1 THz and at least for J < 65 and Ka < 25. [ABSTRACT FROM AUTHOR]

Context. Glycolaldehyde (CH2OHCHO) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. Astronomical surveys of interstellar molecules, such as those available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of molecular species including new isotopologs - to identify these in the interstellar media. Aims. To achieve the detection of the 13C isotopologs of glycolaldehyde in the interstellar medium, their rotational spectra in the millimeter and submillimeter-wave regions were studied. Methods. The spectra of 13CH2OHCHO and CH2OH13CHO were recorded in the 150-945 GHz spectral range in the laboratory using a solid-state submillimeter-wave spectrometer in Lille. The observed line frequencies were measured with an accuracy of 30 kHz up to 700 GHz and of 50 kHz above 700 GHz. We analyzed the spectra with a standard Watson Hamiltonian. Results. About 10 000 new lines were identified for each isotopolog. The spectroscopic parameters were determined for the groundand the three lowest vibrational states up to 945 and 630 GHz. Previous microwave assignments of 13CH2OHCHO were not confirmed. Conclusions. The provided line-lists and sets of molecular parameters meet the needs for a first astrophysical search of 13C-glycolaldehydes. [ABSTRACT FROM AUTHOR]

We present new large-scale R-matrix (up to n = 4) and distorted wave (up to n = 6) scattering calculations for electron collisional excitation of Fe xi. These data are needed for the analysis of soft X-ray spectra of astrophysical plasmas, where strong n = 4 → n = 3 transitions are present. As found in previous work on Fe x, Fexii, and Fexiii, resonances from within the n = 4 levels and cascading from higher levels significantly increase the intensities of these lines. We provide a list of the strongest lines, many of which are unidentified. The present larger model produces intensities for decays from n = 3 levels mostly consistent with our previous work, however significant enhancements for some lower levels are found, in particular for the 3s2 3p3 3d 5D which can be used to measure electron temperatures in the solar corona with the Hinode/EIS spectrometer. [ABSTRACT FROM AUTHOR]

Context. Diacetylene, C4H2, has been identified in several astronomical environments through its infrared spectrum. In contrast, monodeuterated diacetylene (DC4H) has not been detected in space so far owing to the low isotopic abundance of deuterated species but also to the rather poor laboratory spectroscopic characterisation of this molecule. Aims. The aim of this work is to provide accurate spectroscopic parameters for DC4H to achieve reliable predictions for both its spectra at millimetre and infrared wavelengths. Methods. We studied the rotational spectrum of DC4H in the range 85-615 GHz by millimetre-wave spectroscopy and the infrared spectrum below 1000 cm-1 by high-resolution, Fourier-transform spectroscopy. Several pure rotational transitions were recorded in the ground state and in excited vibrational bending states. The three fundamental bands v6, v7, and v8 have been identified and assigned in the infrared spectrum. Results. The rotational transitions were analysed together with the infrared data in a global fit that produces very accurate rovibrational parameters. The observed frequencies and wavenumbers are reported to provide precise guidance for astronomical searches. [ABSTRACT FROM AUTHOR]

Context. The eclipsing low-mass X-ray binary X1822-371 is the prototype of the accretion disc corona (ADC) sources. Its inclination angle (≃82.5°) is high enough that flux from the neutron star is blocked by the edge-on accretion disc. Because the neutron star's direct emission is hidden, its ADC emission is visible. The physical properties of the ADC in X1822-371 have been widely studied, but are still debated in literature. In light of the recent literature and of the results reported in this work we show that the ADC is optically thin. Aims. We analyse two Chandra observations and one XMM-Newton observation to study the discrete features in this source and their variation as a function of the orbital phase, deriving constraints on the temperature, density, and location of the plasma responsible for emission lines. Methods. The HETGS and XMM/Epic-pn observed X1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.75-0.95, and, finally, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. All spectra cover the energy band between 0.35 and 12 keV. Results. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is 5 × 1022 cm-2 and the covered fraction is about 60-65%. We identify several emission lines of He-like and H-like ions, and a prominent fluorescence iron line associated with a blending of Fe I-Fe XV resonant transitions. The transitions of He-like ions show that the intercombination dominates over the forbidden and resonance lines. The line fluxes are the highest during the orbital phases between 0.04 and 0.75. Conclusions. We discuss the presence of an extended, optically thin corona with optical depth of about 0.01 that scatters the X-ray photons from the innermost region into the line of sight. The photoionised plasma producing the O VIII, Ne IX, Ne X, Mg XI, Mg XII, Si XIII, and Si XIV lines is placed in the bulge at the outer radius of the disc distant from the central source of 6 × 1010 cm. The O VII and the fluorescence iron line are probably produced in the photoionised surface of the disc at inner radii. Finally, we suggest that the observed local neutral matter is the matter transferred by the companion star that was expelled from the system by the X-ray radiation pressure, which in turn originated in the accretion process onto the neutron star. [ABSTRACT FROM AUTHOR]

We report the first identification of the optical bands of the B2Σ+-X 2S+ system of AlO in the red supergiant VYCMa. In addition to TiO, VO, ScO, and YO, which were recognized in the optical spectrum of the star long time ago, AlO is another refractory molecule which displays strong emission bands in this peculiar star. Simulating the bands of AlO, we derive a rotational temperature of the circumstellar gas of Trot = 700K. By resolving individual rotational components of the bands, we derive the kinematical characteristics of the gas, finding that the emission is centred at the stellar radial velocity and its intrinsic width is 13.5 kms-1 (full width at half maximum). It is the narrowest emission among all (thermal) features observed in VYCMa so far. The temperature and line widths suggest that the emission arises in gas located within ∼20 stellar radii, where the outflow is still being accelerated. This result contradicts equilibrium-chemistry models which predict substantial AlO abundances only to within a few stellar radii. We argue that non-equilibrium models involving propagation of shocks are needed to explain the observations. [ABSTRACT FROM AUTHOR]

Context. Pure gas-phase chemistry models do not succeed in reproducing the measured abundances of small hydrocarbons in the interstellar medium. Information on key gas-phase progenitors of these molecules sheds light on this problem. Aims. We aim to constrain the chemical content of the Horsehead mane with a millimeter unbiased line survey at two positions, namely the photo-dissociation region (PDR) and the nearby shielded core. This project revealed a consistent set of eight unidentified lines toward the PDR position. We associate them to the l-C3H+ hydrocarbon cation, which enables us to constrain the chemistry of small hydrocarbons. We observed the lowest detectable J line in the millimeter domain along a cut toward the illuminating direction to constrain the spatial distribution of the l-C3H+ emission perpendicular to the photo-dissociation front. Methods. We simultaneously fit 1) the rotational and centrifugal distortion constants of a linear rotor; and 2) the Gaussian line shapes located at the eight predicted frequencies. A rotational diagram is then used to infer the excitation temperature and the column density. We finally compare the abundance to the results of the Meudon PDR photochemical model. Results. Six out of the eight unidentified lines observable in the millimeter bands are detected with a signal-to-noise ratio from 6 to 19 toward the Horsehead PDR, while the two last ones are tentatively detected. Mostly noise appears at the same frequency toward the dense core, located less than 40" away. Moreover, the spatial distribution of the species integrated emission has a shape similar to radical species such as HCO, and small hydrocarbons such as C2H, which show enhanced abundances toward the PDR. The observed lines can be accurately fitted with a linear rotor model, implying a 1Σ ground electronic state. The deduced rotational constant value is B = 11 244.9512 ± 0.0015 MHz, close to that of l-C3H. Conclusions. This is the first detection of the l-C3H+ hydrocarbon in the interstellar medium. Laboratory spectroscopy is underway to confirm these results. Interferometric imaging is needed to firmly constrain the small hydrocarbon chemistry in the Horsehead. [ABSTRACT FROM AUTHOR]