723 research outputs found
Vsini-s for late-type stars from spectral synthesis in K-band region
We analyse medium-resolution spectra (R\sim 18000) of 19 late type dwarfs in
order to determine vsini-s using synthetic rather than observational template
spectra. For this purpose observational data around 2.2 m of stars with
spectral classes from G8V to M9.5V were modelled.
We find that the Na I (2.2062 and 2.2090 m) and CO 2-0 band
features are modelled well enough to use for vsini determination without the
need for a suitable observational template spectra. Within the limit of the
resolution of our spectra, we use synthetic spectra templates to derive vsini
values consistent with those derived in the optical regime using observed
templates. We quantify the errors in our vsini determination due to incorrect
choice of model parameters \Teff, log , , [Fe/H] or FWHM and
show that they are typically less than 10 per cent. We note that the spectral
resolution of our data(\sim 16 km/s) limited this study to relatively fast
rotators and that resolutions of 60000 will required to access most late-type
dwarfs.Comment: 8 pages, 4 figures, 3 tables, accepted to the MNRA
A catalogue of bright (K <9) M dwarfs
Using the Position and Proper Motion Extended-L (PPMXL) catalogue, we have used optical and near-infrared colour cuts together with a reduced proper motion cut to find bright M dwarfs for future exoplanet transit studies. PPMXL's low proper motion uncertainties allow us to probe down to smaller proper motions than previous similar studies. We have combined unique objects found with this method to that of previous work to produce 8479 K <9 M dwarfs. Low-resolution spectroscopy was obtained of a sample of the objects found using this selection method to gain statistics on their spectral type and physical properties. Results show a spectral-type range of K7-M4V. This catalogue is the most complete collection of K <9 M dwarfs currently available and is made available here.Peer reviewe
Modeling the spectrum of V4334 Sgr (Sakurai's Object)
Theoretical spectral energy distributions were computed for a grid of
hydrogen-deficient and carbon-rich model atmospheres of T(eff) in the range of
5000-6250 K and log g = 1.0 - 0.0 by the technique of opacity sampling, taking
into account continuous, molecular band and atomic line absorption. These
energy distributions were compared with the spectrum of V4334 Sgr (Sakurai's
object) of April, 1997 in the wavelength interval 300-1000 nm. We show that (1)
the shape of the theoretical spectra depends strongly on T(eff) but only very
weakly on the hydrogen abundance; (2) the comparison of the observed and
computed spectra permits to estimate T(eff) approximately 5500 K for V4334 Sgr
in April, 1997, and its interstellar reddening (plus a possible circumstellar
contribution) E(B-V) approximately 0.70.Comment: 7 pages, 8 figures, LaTeX, accepted by Astronomy and Astrophysic
The Synthesis of Agent Produced by Interaction of the Complex Trans-Dichlorodiamminplatinum(II) with Arabinogalactan and its Properties
ΠΡΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠΈ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ° ΡΡΠ°Π½Ρ-Π΄ΠΈΡ
Π»ΠΎΡΠΎΠ΄ΠΈΠ°ΠΌΠΌΠΈΠ½ΠΏΠ»Π°ΡΠΈΠ½Ρ(II) Ρ Π°ΡΠ°Π±ΠΈΠ½ΠΎΠ³Π°Π»Π°ΠΊΡΠ°Π½ΠΎΠΌ
ΠΏΠΎΠ»ΡΡΠ΅Π½ Π½ΠΎΠ²ΡΠΉ ΠΏΡΠ΅ΠΏΠ°ΡΠ°Ρ, ΠΊΠΎΡΠΎΡΡΠΉ ΠΎΡ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·ΠΎΠ²Π°Π½ ΠΌΠ΅ΡΠΎΠ΄Π°ΠΌΠΈ Π Π€Π, ΠΠ-ΡΠΏΠ΅ΠΊΡΡΠΎΡΠΊΠΎΠΏΠΈΠΈ, Π£Π€-
ΡΠΏΠ΅ΠΊΡΡΠΎΡΠΎΡΠΎΠΌΠ΅ΡΡΠΈΠΈ ΠΈ ΡΠ΅ΡΠΌΠΎΠ³ΡΠ°Π²ΠΈΠΌΠ΅ΡΡΠΈΠΈ. ΠΠ·ΡΡΠ΅Π½Ρ ΡΠΎΡΡΠ°Π² ΠΈ ΡΡΡΠΎΠ΅Π½ΠΈΠ΅ ΡΡΠΎΠ³ΠΎ ΠΏΡΠ΅ΠΏΠ°ΡΠ°ΡΠ°.
ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ ΡΡΠ°Π½Ρ-Π΄ΠΈΡ
Π»ΠΎΡΠΎΠ΄ΠΈΠ°ΠΌΠΌΠΈΠ½ΠΏΠ»Π°ΡΠΈΠ½Ρ(II) ΡΠ΄Π΅ΡΠΆΠΈΠ²Π°ΡΡΡΡ Π°ΡΠ°Π±ΠΈΠ½ΠΎΠ³Π°Π»Π°ΠΊΡΠ°Π½ΠΎΠΌ
Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π½ΡΠΌΠΈ ΡΠ²ΡΠ·ΡΠΌΠΈ, ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½Π½ΡΠΌΠΈ ΡΡΠΈΡΠ½ΡΠΌΠΈ Π³ΡΡΠΏΠΏΠ°ΠΌΠΈ, βΠ‘ β Π β Π‘ β NH3-Π³ΡΡΠΏΠΏΠ°ΠΌΠΈ
ΠΈΡΡ
ΠΎΠ΄Π½ΠΎΠ³ΠΎ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ°. ΠΠΎΠ»ΡΡΠ΅Π½ ΠΏΡΠ΅ΠΏΠ°ΡΠ°Ρ Ρ Π½ΠΎΠ²ΡΠΌΠΈ ΡΠ°ΡΠΌΠ°ΠΊΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ ΡΠ²ΠΎΠΉΡΡΠ²Π°ΠΌΠΈ β
ΠΏΠΎΠ²ΡΡΠ΅Π½Π½ΠΎΠΉ ΡΠ°ΡΡΠ²ΠΎΡΠΈΠΌΠΎΡΡΡΡ, ΠΏΠΎΠ½ΠΈΠΆΠ΅Π½Π½ΠΎΠΉ ΡΠΎΠΊΡΠΈΡΠ½ΠΎΡΡΡΡ ΠΈ Π±ΠΎΠ»ΡΡΠ΅ΠΉ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΡΡ ΠΏΠΎ
ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Ρ ΡΠΈΡ-Π΄ΠΈΡ
Π»ΠΎΡΠΎΠ΄ΠΈΠ°ΠΌΠΌΠΈΠ½ΠΏΠ»Π°ΡΠΈΠ½ΠΎΠΉ(II)The obtained new product of reaction of the complex trans-dichlorodiaminplatinum(II) with
arabinogalactan was characterized by XRD, IR-spectroscopy, UF-spetrophotometry and
thermogravimetry. The composition and structure of this product was studied. It has been shown that
trans-dichlorodiaminplatinum(II) associated with arabinogalactan through βC-O-C- amino hydrogen
of the original complex.
The synthesized product has the improved pharmacological properties being more soluble, less toxic
and shows a greater anticancer activity as compared to cis-dichlorodiaminplatinum(II
Infrared Spectra and Spectral Energy Distributions of Late-M- and L-Dwarfs
We have obtained 1.0-2.5um spectra at R~600 of 14 disk dwarfs with spectral
types M6 to L7. For four of the dwarfs we have also obtained infrared spectra
at R~3000 in narrow intervals. In addition, we present new L' photometry for
four of the dwarfs in the sample, which allows improved determinations of their
bolometric luminosities. We resolve the L-dwarf Denis-P J 0205-1159 into an
identical pair of objects separated by 0.35". The spectra, with the published
energy distribution for one other dwarf, are compared to synthetic spectra
generated by upgraded model atmospheres. Good matches are found for 2200> Teff
K>1900 (spectral types around M9 to L3), but discrepancies exist at Teff> 2300
K (M8) and for Teff<1800 K (L4-L7). At the higher temperatures the mismatches
are due to incompleteness in the water vapor linelist. At the lower
temperatures the disagreement is probably due to our treatment of dust: we
assume a photospheric distribution in equilibrium with the gas phase. We derive
effective temperatures for the sample from the comparison with synthetic
spectra and also by comparing our observed total intrinsic luminosities to
structural model calculations (which are mostly independent of the atmosphere
but are dependent on the unknown masses and ages of the targets). The two
derivations agree to ~200 K except for the faintest object in the sample where
the discrepancy is larger. Agreement with other temperature determinations is
also ~200 K, except for the L7 dwarf.Comment: 31 pages incl. 5 Tables and 12 Figures, accepted by ApJ for Feb 2001
issu
NY Her: possible discovery of negative superhumps
We presents result of CDD photometry for SU UMa dwarf nova NY Her during 6 nights in June 2017 when object was in quiescence.
Light curves clearly show strong amplitude variations in a range of 0Time series analysis revealed a period 0.07141(5) d,
that we identified as the period of possible negative superhumps of NY Her
Peierls Instabilities in Quasi-One-Dimensional Quantum Double-Well Chains
Peierls-type instabilities in quarter-filled () and half-filled
() quantum double-well hydrogen-bonded chain are investigated
analytically in the framework of two-stage orientational-tunnelling model with
additional inclusion of the interactions of protons with two different optical
phonon branches. It is shown that when the energy of proton-phonon coupling
becomes large, the system undergoes a transition to a various types of
insulator states. The influence of two different transport amplitudes on ground
states properties is studied. The results are compared with the pressure effect
experimental investigations in superprotonic systems and hydrogen halides at
low temperatures.Comment: 7 pages, RevTeX, 9 eps figure
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