scholarly journals EXOCROSS: a general program for generating spectra from molecular line lists

2018 ◽  
Vol 614 ◽  
pp. A131 ◽  
Author(s):  
Sergei N. Yurchenko ◽  
Ahmed F. Al-Refaie ◽  
Jonathan Tennyson
Keyword(s):  
Partition Function ◽  
Line Profiles ◽  
Molecular Line ◽  
Specific Heats ◽  
Quantum Numbers ◽  
Fortran Code ◽  
General Program ◽  
Vibrational Bands ◽  
High Degree ◽  
Two Temperature

EXOCROSS is a Fortran code for generating spectra (emission, absorption) and thermodynamic properties (partition function, specific heat, etc.) from molecular line lists. Input is taken in several formats, including ExoMol and HITRAN formats. EXOCROSS is efficiently parallelized showing also a high degree of vectorization. It can work with several line profiles such as Doppler, Lorentzian and Voigt and support several broadening schemes. Voigt profiles are handled by several methods allowing fast and accurate simulations. Two of these methods are new. EXOCROSS is also capable of working with the recently proposed method of super-lines. It supports calculations of lifetimes, cooling functions, specific heats and other properties. EXOCROSS can be used to convert between different formats, such as HITRAN, ExoMol and Phoenix. It is capable of simulating non-LTE spectra using a simple two-temperature approach. Different electronic, vibronic or vibrational bands can be simulated separately using an efficient filtering scheme based on the quantum numbers.

scholarly journals On the nature of protostellar H2O masers

1987 ◽  
Vol 122 ◽  
pp. 141-142
Author(s):  
G. M. Rudnitskij
Keyword(s):  
Active Phase ◽  
Young Star ◽  
Line Profiles ◽  
Free Electrons ◽  
Heavy Particles ◽  
Vlbi Observations ◽  
Generation Region ◽  
Star Formation Regions ◽  
Maser Radio ◽  
Two Temperature

Most sources of B2O maser radio emission at 1.35 cm, associated with star formation regions, show strong variability with, sometimes, rapid bursts of emission (see, e.g., Liljeström 1984, Rowland and Cohen 1986, and references therein). A preliminary conclusion on the possible cyclicity of H2O maser variability can be drawn (Lekht et al. 1982, 1983), with a quasiperiod of several years. The “quiet” state of a maser source, with moderate, slowly varying values of the line flux density, turns to the “active” phase with H2O line bursts (Lekht et al. 1983). The H2O maser generation region is probably located in a rotating gas-and-dust disc (torus) around a protostar (or young star). This is pointed to by VLBI observations showing in some sources maser features arranged in an ellipsoidal structure around a common centre (presumably, the protostellar object - see Downes et al. 1979), as well as by symmetrical character of E2O line profiles of many masers (Lekht et al. 1982). As an excitation mechanism for H2O, collisional pumping in two-temperature medium behind a shock front (with hot heavy particles and cold free electrons or vice versa) is widely accepted (Bolgova et al. 1982, Kylafis and Norman 1986).

Evolution of Chemistry and Molecular Line Profiles during Protostellar Collapse

2004 ◽  
Vol 617 (1) ◽  
pp. 360-383 ◽  
Author(s):  
Jeong‐Eun Lee ◽  
Edwin A. Bergin ◽  
Neal J. Evans II
Keyword(s):  
Line Profiles ◽  
Molecular Line ◽  
Protostellar Collapse

HITRAN2020: An overview of what to expect

2020 ◽  
Author(s):  
Robert Hargreaves ◽  
Iouli Gordon ◽  
Laurence Rothman ◽  
Robab Hashemi ◽  
Ekaterina Karlovets ◽  
...  
Keyword(s):  
Application Programming Interface ◽  
Line Profiles ◽  
Hitran Database ◽  
Individual Molecule ◽  
Application Programming ◽  
Vibrational Bands ◽  
Atmospheric Radiative Transfer ◽  
Almost All ◽  
Programming Interface ◽  
Scientific Collaborations

<p>The HITRAN database is an integral component of numerous atmospheric radiative transfer models and it is therefore essential that the database contains the most appropriate up-to-date spectroscopic parameters. To this end, the HITRAN2020 database is scheduled to be released at the end of this year.  The compilation of this edition (as is the tradition for the HITRAN database) exemplifies the efficiency and necessity of worldwide scientific collaborations. It is a titanic effort of experimentalists, theoreticians and atmospheric scientists, who measure, calculate and validate the HITRAN data.</p><p>The HITRAN line-by-line lists for almost all 49 molecules have been updated in comparison to HITRAN2016 (Gordon et al., 2017), the previous compilation. The extent of these updates depend on the molecule, but range from small adjustments for a few lines of an individual molecule to complete replacements of line lists and the introduction of new isotopologues. Many new vibrational bands have been added to the database, thereby extending the spectral coverage and completeness of the datasets. In addition the accuracy of the parameters for major atmospheric absorbers has been substantially increased, often featuring sub-percent uncertainties.</p><p>Furthermore, the amount of parameters has also been significantly increased. For example, HITRAN2020 will now incorporate non-Voigt line profiles for many gases, broadening by water vapour (Tan et al., 2019), as well as updated collision induced absorption sets (Karman et al., 2019). The HITRAN2020 edition will continue taking advantage of the new structure and interface available at www.hitran.org (Hill et al., 2016) and the HITRAN Application Programming Interface (Kochanov et al., 2016).</p><p>This talk will provide a summary of these updates, emphasizing details of some of the most important or drastic improvements.</p><p><strong>References:</strong></p><p>Gordon, I.E., .et al., (2017), <em>JQSRT</em> <strong>203</strong>, 3–69.  (doi:10.1016/j.jqsrt.2017.06.038)</p><p>Hill, C., et al., (2016), <em>JQSRT</em> <strong>177</strong>, 4–14.  (doi:10.1016/j.jqsrt.2015.12.012)</p><p>Karman, T., et al. (2019), <em>Icarus</em> <strong>328</strong>, 160–175.  (doi:10.1016/j.icarus.2019.02.034)</p><p>Kochanov, R.V., et al.,( 2016), <em>JQSRT</em> <strong>177</strong>, 15–30.  (doi:10.1016/j.jqsrt.2016.03.005)</p><p>Tan, Y., et al., (2019),<em> J. Geophys. Res. Atmos.</em> <strong>124</strong>, 11580-11594. (doi:10.1029/2019JD030929)</p><p> </p>

scholarly journals Mode Determination by Fourier Analysis of Line-Profile Variations: Application to τ Peg

1993 ◽  
Vol 139 ◽  
pp. 147-147
Author(s):  
E.J. Kennelly ◽  
G.A.H. Walker ◽  
W.J. Merryfield ◽  
J.M. Matthews
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Line Profiles ◽  
High Resolution Data ◽  
Low Degree ◽  
Scuti Star ◽  
High Degree ◽  
Scuti Stars ◽  
Resolution Data ◽  
Good Agreement

AbstractThe identification of modes of oscillation is an important first step towards the seismology of stars. Low- and high-degree nonradial modes of oscillation may appear as variations in the line profiles of rapidly rotating δ Scuti stars. We present a technique whereby complex patterns in the line profiles are decomposed into Fourier components in both time and “Doppler space”. The technique is applied to the 7.3-hour time series of high-resolution data obtained from CFHT for the δ Scuti star τ Peg. In addition to the low-degree mode which has been identified in photometric studies (Breger 1991), we find evidence for at least three high-degree modes near 11 and 15. Correcting for the rotation of the star, most of these modes appear to oscillate with frequencies near 17 cycles day-1. Our results are found to be in good agreement with the theoretical limits imposed on the frequencies of oscillation by the models of Dziembowski (1990).

scholarly journals Signatures of turbulence in the dense interstellar medium

1991 ◽  
Vol 147 ◽  
pp. 119-136
Author(s):  
E. Falgarone ◽  
T.G. Phillips
Keyword(s):  
Interstellar Medium ◽  
Turbulent Flows ◽  
Fractal Geometry ◽  
Molecular Clouds ◽  
Large Range ◽  
Line Profiles ◽  
Physical Processes ◽  
Molecular Line ◽  
Scale Size ◽  
Excitation Conditions

We present an ensemble of recent observational results on molecular clouds which, taken separately, could all be understood by invoking various unrelated physical processes, but taken all together form a coherent ensemble stressing the imprints of turbulence in the physics of the cold interstellar medium. These results are first, the existence of wings in the molecular line profiles, which can be interpreted on statistical grounds as the signature of the intermittency of the velocity field in turbulent flows, second the fractal geometry of the cloud edges, with properties reminiscent of those of various surfaces studied in turbulent laboratory flows, and third, the fact that the dense gas fills only a very small fraction of the space. The last points are supported by CO multitransition observations of a few fields in nearby molecular clouds. They show that the excitation conditions are the same for the gas emitting in the linewings and in the linecores and are also remarkably uniform over a large range (factor 10) of column densities. An attractive interpretation of the molecular line data is that most of the 12CO(J=2—1) and (J=3—2) emissions arise in cold (Tk ≥ 10K) and dense (nH2 ∼ 104cm—3 or more) structures distributed on a fractal set with no characteristic scale size greater than about 1000 AU.

scholarly journals Molecular line profiles from contracting dense cores

2010 ◽  
Vol 407 (4) ◽  
pp. 2434-2442 ◽  
Author(s):  
Steven W. Stahler ◽  
Jeffrey J. Yen
Keyword(s):  
Line Profiles ◽  
Molecular Line ◽  
Dense Cores

scholarly journals High-resolution spectroscopic view of planet formation sites

2010 ◽  
Vol 6 (S276) ◽  
pp. 50-53 ◽  
Author(s):  
Zsolt Regály ◽  
Laszlo Kiss ◽  
Zsolt Sándor ◽  
Cornelis P. Dullemond
Keyword(s):  
High Resolution ◽  
Planet Formation ◽  
Giant Planet ◽  
Circumstellar Disks ◽  
Disk Surface ◽  
Line Profiles ◽  
Molecular Line ◽  
Near Ir ◽  
Velocity Flow ◽  
Core Accretion

AbstractTheories of planet formation predict the birth of giant planets in the inner, dense, and gas-rich regions of the circumstellar disks around young stars. These are the regions from which strong CO emission is expected. Observations have so far been unable to confirm the presence of planets caught in formation. We have developed a novel method to detect a giant planet still embedded in a circumstellar disk by the distortions of the CO molecular line profiles emerging from the protoplanetary disk's surface. The method is based on the fact that a giant planet significantly perturbs the gas velocity flow in addition to distorting the disk surface density. We have calculated the emerging molecular line profiles by combining hydrodynamical models with semianalytic radiative transfer calculations. Our results have shown that a giant Jupiter-like planet can be detected using contemporary or future high-resolution near-IR spectrographs such as VLT/CRIRES or ELT/METIS. We have also studied the effects of binarity on disk perturbations. The most interesting results have been found for eccentric circumprimary disks in mid-separation binaries, for which the disk eccentricity - detectable from the asymmetric line profiles - arises from the gravitational effects of the companion star. Our detailed simulations shed new light on how to constrain the disk kinematical state as well as its eccentricity profile. Recent findings by independent groups have shown that core-accretion is severely affected by disk eccentricity, hence detection of an eccentric protoplanetary disk in a young binary system would further constrain planet formation theories.

scholarly journals Photospheric molecular line profiles in cool stars

1981 ◽  
Vol 59 ◽  
pp. 119-124
Author(s):  
S.T. Ridgway ◽  
E.D. Friel
Keyword(s):  
Spectral Lines ◽  
High Spectral Resolution ◽  
High Signal ◽  
Line Profiles ◽  
Signal To Noise ◽  
Molecular Line ◽  
Ejection Process ◽  
Cool Stars ◽  
Mass Ejection ◽  
Selection Of

AbstractSpectral lines of the ΔV=2 rotation vibration bands of CO are well suited for study of photospheric motions and the mass ejection process in cool stars. We have obtained high spectral resolution (1.8 km/sec) and high signal-to-noise (>102) line profiles for a selection of K and M giants. These profiles are being studied for evidence of gas motions in the photosphere and near circumstellar regions.

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