Photometric Mode Research Articles

The Nainital-Cape Survey

The Nainital-Cape survey is a dedicated research programme to search and study pulsational variability in chemically peculiar stars in the Northern Hemisphere. The aim of the survey is to search such chemically peculiar stars which are pulsationally unstable. The observations of the sample stars were carried out in high-speed photometric mode using a three-channel fast photometer attached to the 1.04-m Sampurnanand telescope at ARIES. The new photometric observations confirmed that the pulsational period of star HD25515 is 2.78-hrs. The repeated time-series observations of HD113878 and HD118660 revealed that previously known frequencies are indeed present in the new data sets. We have estimated the distances, absolute magnitudes, effective temperatures and luminosities of these stars. Their positions in the H-R diagram indicate that HD25515 and HD118660 lie near the main-sequence while HD113878 is an evolved star. We also present a catalogue of 61 stars classified as null results, along with the corresponding 87 frequency spectra taken over the time scale 2002-2008. A statistical analysis of these null results shows, by comparison with past data, that the power of the noise in the light curves has slightly increased during the last few years.

C/2002 VQ94 (LINEAR) and 29P/Schwassmann–Wachmann 1 — CO + and N +2 rich comets

We investigated comets active at large heliocentric distances using observations obtained at the 6-m BTA telescope (SAO RAS, Russia). Long-slit and photometric modes of the focal reducer SCORPIO were used. Two of the comets, 29P/Schwassmann–Wachmann 1 (SW1) and C/2002 VQ94 (LINEAR) were observed to be emission rich. Detection of CO + and N + 2 emissions in the comae of these comets is evidence that they were formed in the outer regions of the Solar System or in a pre-solar interstellar cloud in a low temperature environment with T ⩽ 25 K . The ratio of N + 2/CO + is equal to 0.011 and 0.027 for SW1 and LINEAR, respectively. Comet LINEAR is the most distant object in the Solar System (7.332 AU) for which CO + and N + 2 are measured. The photometric maximum of the isolated CO + coma in Comet LINEAR is shifted by 1.4 arcsec ( 7.44 × 10 3 km ) relative to the photometric maximum of the dust coma. This shift deviates from the sunward direction by 63 degrees.

The HELAS NA5 Workpackage Frequency Analysis and Mode Identification for Asteroseismology

I present the software tool of the HELAS NA5 Workpackage Frequency Analysis and Mode Identification for Asteroseismology. We term this tool FAMIAS. It will be a collection of software tools for the frequency analysis and mode identification of photometric as well as spectroscopic data of oscillating stars packed into a graphical user interface. The workpackage is currently in the stage of development and will be made publicly available in a well documented form at the end of 2007. The creation of this data analysis tool is one of the objectives of the NA5 workpackage “Asteroseismology” within HELAS. For the spectroscopic mode identification, the moment method as well as various methods based on the Doppler broadening of the line profile will be implemented. The photometric mode identification will be based on the method of amplitude ratios and phase differences in different passbands. Therefore, pre-computed grids with the frequency values and their non-adiabatic eigenfunctions in the outer atmosphere for different kinds of stars will be included in the package.

Theoretical aspects of g-mode pulsations in γ Doradus stars

Inhalt (u.a.): M. BREGER: Delta Scuti stars: Observational aspects; M.S. Cunha: Theory of rapidly oscillating Ap stars; M. SACHKOV et al.: Vertical structure of pulsations in roAp stars; G. HOUDEK: Theoretical asteroseismology of solar-like oscillations; B.L. POPIELSKI: Core modes as a seismic probe of mixing beyond the convective core; M. GODART: Temperature gradients in the core overshooting region; W.A. DZIEMBOWSKI – J. DASZYŃSKA-DASZKIEWICZ – A.A. PAMYATNYKH: Interpretation of the Be star HD 163868 oscillation spectrum based on the MOST observations; D. KILKENNY: Pulsating Hot Subdwarfs – An Observational Review; M.H. MONTGOMERY: Mapping Convection using Pulsating White Dwarf Stars; M. ROTH: The Network Activities in HELAS; I. KUDZEJ et al.: A New Slovak Observatory 500 km from Vienna; W.W. WEISS: Microsatellites; G. KOPACKI – S. FRANDSEN: RR Lyrae stars in M4

MIDI observations of 1459 Magnya: First attempt of interferometric observations of asteroids with the VLTI

The Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) can be used to obtain direct determination of the sizes and the albedos of asteroids. We present results of the first attempt to carry out interferometric observations of asteroids with the Mid Infrared Interferometric Instrument (MIDI) at the VLTI. Our target was 1459 Magnya. This is the only V-type asteroid known to exist in the outer main-belt, and its IRAS-albedo turns out to be rather low for an object of this taxonomic class. Interferometric fringes were not detected, very likely due to the fact that the flux emitted by the asteroid was lower than expected and below the MIDI threshold for fringe detection. However, by fitting the Standard Thermal Model to the N-band infrared flux measured by MIDI in photometric mode and to the visible absolute magnitude, obtained from quasi-simultaneous B- and V-band photometric observations, we have derived a geometric visible albedo of 0.37 ± 0.06 and an effective diameter of 17 ± 1 km . This new estimate of the albedo differs from that previously obtained by IRAS and is more consistent with the V-type taxonomic classification of 1459 Magnya.

Global solar Doppler velocity determination with the GOLF/SoHO instrument

The Global Oscillation at Low Frequencies (GOLF) experiment is a resonant scattering spectrophotometer on board the Solar and Heliospheric Observatory (SoHO) mission, originally designed to measure the disk-integrated solar oscillations of the Sun. This instrument was designed in a relative photometric mode involving both wings of the neutral sodium doublet (D1 at λ 5896 and D2 at λ 5890 A). However, a “one-wing” photometric mode has been selected to ensure 100% continuity in the measurements after a problem in the polarization mechanisms. Thus the velocity is obtained from only two points on the same wing of the lines. This operating configuration imposes tighter constraints on the stability of the instrument with a higher sensitivity to instrumental variations. In this paper we discuss the evolution of the instrument during the last 8 years in space and the corrections applied to the measured counting rates due to known instrumental effects. We also describe a scaling procedure to obtain the variation of the Doppler velocity based on our knowledge of the sodium profile slope and we compare it to previous velocity estimations.

Time-dependent convection seismic study of five γ Doradus stars

We apply for the first time the time-dependent convection (TDC) treatment of Gabriel and Grigahcene et al. to the photometric mode identification in γ Doradus (γ Dor) stars. We consider the influence of this treatment on the theoretical amplitude ratios and phase differences. Comparison with the observed amplitudes and phases of the stars γ Dor, 9 Aurigae, HD 207223 = HR 8330, HD 12901 and 48501 is presented and enables us to identify the degree � of the pulsation modes for four of them. We also determine the mode stability for different models of these stars. We show that our TDC models agree better with observations than with frozen convection models. Finally, we compare the results obtained with different values of the mixing-length parameter α.

Wind-velocity lidar measurements by use of a Mach-Zehnder interferometer, comparison with a Fabry-Perot interferometer.

We present the first wind-velocity profiles obtained with a direct-detection Doppler lidar that uses a Mach-Zehnder interferometer (MZI) as spectral discriminator. The measurements were performed in the lower stratosphere, between 10 and 40 km in altitude, at the Observatoire de Haute Provence (OHP), France, during nighttime. They are in excellent agreement with those obtained simultaneously and independently with the already validated double Fabry-Perot interferometer (FPI) of the OHP Doppler lidar (mean difference lower than the combined standard deviation). A statistical analysis shows that the random error obtained with this experimental MZI is 1.94 times the Cramer-Rao lower bound and is approximately half of that given by the FPI (both operating in photometric mode). Nevertheless, the present MZI measurements are sensitive to the presence of atmospheric particles and need an additional correction, whereas the OHP FPI is designed to be insensitive to particulate scattering.

Seismic modelling of the $\beta\,$Cep star EN (16) Lacertae

We perform seismic modelling of the massive Cep star EN Lacertae. The starting point of our analysis is the spectroscopic mode identification recently performed. To this, we add a new updated photometric mode identification based upon a non-adiabatic description of the eigenfunctions in the outer atmosphere. Both mode identifications agree and this allows us to fine-tune the stellar parameters of EN Lacertae with unprecedented precision. This is done by producing a huge amount of stellar models with different parameters and selecting those that fulfill the frequency values and the mode identification. Our study is the first one of its kind in which a reconcilation between observed pulsational characteristics and theoretical models can be achieved at a level that allows accurate determination of the basic stellar parameters of a massive oscillator. We derive a mass of and an age of 15.7 million years if we assume that convective overshooting does not occur.

New grids of ATLAS9 atmospheres

Using up-to-date model atmospheres (Heiter et al. 2002) with the turbulent convection approach developed by Canuto et al. (1996, CGM), quadratic, cubic and square root limb darkening coecients (LDC) are calculated with a least square fit method for the Stromgren photometric system. This is done for a sample of solar metallicity models with eective temperatures between 6000 and 8500 K and with logg between 2.5 and 4.5. A comparison is made between these LDC and the ones computed from model atmospheres using the classical mixing length prescription with a mixing length parameter = 1:25 and= 0:5. For CGM model atmospheres, the law which reproduces better the model intensity is found to be the square root one for the u band and the cubic law for thev band. The results are more complex for the b andy bands depending on the temperature and gravity of the model. Similar conclusions are reached for MLT = 0:5 models. As expected much larger dierences are found between CGM and MLT with= 1:25. In a second part, the weighted limb-darkening integrals, b', and their derivatives with respect to temperature and gravity, are then computed using the best limb-darkening law. These integrals are known to be very important in the context of photometric mode identification of non-radial pulsating stars. The eect of convection treatment on these quantities is discussed and as expected dierences in the b' coecients and derivatives computed with CGM and MLT= 0:5 are much smaller than dierences obtained between computations with CGM and MLT = 1:25.

A photometric mode identification method, including an improved non-adiabatic treatment of the atmosphere

We present an improved version of the method of photometric mode identification of Heynderickx et al. (1994). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions determined in the outer stellar atmosphere according to the formalism recently proposed by Dupret et al.(2002). Our improved photometric mode identification technique is therefore no longer dependent on ad hoc parameters for the non-adiabatic effects. It contains the complete physical conditions of the outer atmosphere of the star, provided that rotation does not play a key role. We apply our improved method to the two slowly pulsating B stars HD 74560 and HD 138764 and to the beta Cephei star EN (16) Lac. Besides identifying the degree l of the pulsating stars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on parameters such as the metallicity and the mixing-length parameter alpha (a procedure we label non-adiabatic asteroseismology).

An Improved Method of Photometric Mode Identification: Applications to Slowly Pulsating B, β Cephei, δ Scuti and γ Doradus Stars

We present an improved version of the method of photometric mode identification based upon the inclusion of non-adiabatic eigenfunctions determined in the stellar atmosphere, according to the formalism recently proposed by Dupret et al. (2002).We apply our method to β Cephei, Slowly Pulsating B, δ Scuti and γ Doradus stars. Besides identifying the degree l of the pulsatingstars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on the metallicity for β Cephei and SPBs, the characteristics of the superficial convection zone for δ Scuti and γ Doradus starsand the limb-darkening law.

Photometric amplitudes and phases of nonradial oscillation in rotating stars

Effects of rotational mode coupling on photometric parameters of stellar oscillations are studied. At moderate rotation rates, a strong coupling between modes of spherical harmonic degree, $\ell$, differing by 2 and of the same azimuthal order, $m$, takes place if the frequencies are close. This is a common situation amongst main sequence pulsators. Numerical results for a sequence of $\beta$ Cephei star models are reported for the two- and three-mode couplings. One consequence of mode coupling is that modes of higher degree should be considered in photometric mode identification. Modes with nominal degree $\ell>2$ acquire substantial $\ell\le2$ components and therefore are more likely to reach detectable amplitudes. Coupled mode positions in the amplitude ratio - phase difference diagrams, based on multicolour photometry, become both aspect- and $m$-dependent. Examples of the mode path in the diagram with varying aspect are given. The diagrams remain a useful tool for mode identification in rotating stars but the tool must be used with care.

Short-period line profile and light variations in the Herbig Ae star V351 Orionis

We present 318 high-dispersion echelle spectra and 450 UBVRCIC observations of the pre-main-sequence star V351 Orionis. These data were obtained simultaneously over a two-week period. The star is unusual in that it no longer shows the frequent sharp fadings that occurred prior to 1986. We find features characteristic of Herbig Ae stars: Hα emission, sharp and broad Na ii absorption components and weak He i absorption. The Hα profile is strongly variable with a time-scale of 1 d and normally is an inverse P Cygni profile, but on occasions overt emission disappears altogether. The equivalent widths of the sharp Na ii absorption lines have decreased quite markedly since 1995, indicating a decrease in the column density of gas in the line of sight. We also detect very weak forbidden [O i] emission. There is no evidence for veiling of the star, but a possible 1.0-d or 0.5-d period in the equivalent widths of the lines could indicate the presence of an accretion hotspot. The star is of particular interest because it is pulsating. We detect at least two periods in the light variation and a further period from the radial velocity variations. Attempts at photometric mode identification were not successful, but from the morphology of the line profiles we can identify one mode as non-radial. In addition, we see on some nights several residual absorption subfeatures moving across the line profile from blue to red. These are almost certainly caused by one or more modes of high degree (l≈8).

Mode identification in the Scuti Star 1 Mon

We present new multicolour photometry and simultaneous high-dispersion spectroscopy for the δ Scuti star 1 Mon. The two main periodicities in the star are still present, but the third known period is not directly detected in the new radial velocities or light variations. However, it is detected in the periodogram of the second moment of the line profile variations. We use the cross-correlation function as an approximation for the line profile variations. By computing theoretical profiles for a given mode and comparing them with phased cross-correlation profiles, we are able to determine a goodness-of-fit criterion and estimate the most probable spherical harmonic degree, the azimuthal order, m, of the pulsation and also the angle of inclination. We then compare the relative amplitudes and phases of the photometric variations in five wavebands and obtain the best estimates of for the two visible periodicities. We confirm the earlier determinations that the main periodicity is a radial mode and that the other periodicity is probably We show that the line profile variations and light variations give consistent results. We point out the importance of a long wavelength range when using the photometric mode identification technique. Finally, we attempt to match the two periods with unstable modes from linear, non-adiabatic calculations. We are able to show that the principal period is well matched by either the fundamental or first overtone radial mode, but could not find a satisfactory fit to the mode. We discuss implications for mode identification of δ Scuti stars based on what we have learned from this star.

The potential role of intracerebral glutathione in the retention of a representative 99MTc SNS/S mixed ligand complex in mice brain

The synthesis, radiochemistry and biodistribution in mice of 99mTcO{[(CH3CH2)2NCH2CH2-N(CH2CH2S)2] (p-SPh-COOCH2CH3)}, I, are reported herein. Complex I forms by binding of (CH3CH2)2NCH2CH2N(CH2CH2SH)2 and p-HSPhCOOCH2CH3 ligands to reduced 99mTc using glucoheptonate (GH) as transfer ligand. Corroboration of structure with an authentic 99gTc sample is achieved by reverse phase high pressure liquid chromatography (RP-HPLC) adopting parallel radiometric and photometric detection modes. By incubation at 37°C with glutathione (GSH) in aqueous medium I tranforms to an hydrophilic compound, as shown by HPLC. Tissue distribution experiments reveal high uptake and retention of I in mice brain.

Determination of p-hydroxyphenylglycine by reaction with o-phthalaldehyde using a flow-injection fluorimetric procedure

In the present study, new flow injection procedures for the determination of p-hydroxyphenylglycine using either photometric or fluorimetric detection are proposed. The methods are based on the reaction of the amino acid with o-phthalaldehyde and 2-mercaptoethanol. The calibration graphs based on peak area were linear in the ranges 20–300 ng ml −1 with fluorimetric detection and 5–60 μg ml −1 using the photometric mode. The detection limit calculated for the fluorimetric procedure was 10 ng ml −1. The method was applied to the determination of the free p-hydroxyphenylglycine present in industrial pharmaceutical samples of a Dane salt.

The TIRGO Lunar Occultation Program: Summary of the 1985-1995 Observations

view Abstract Citations (31) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The TIRGO Lunar Occultation Program: Summary of the 1985-1995 Observations Richichi, A. ; Baffa, C. ; Calamai, G. ; Lisi, F. Abstract A program of observations of lunar occultations in the near infrared was started at the TIRGO observatory in late 1985. After ten years of operation, we provide a list of all the events recorded up to the end of 1995 using the facility IR photometer. A total of 157 light curves were obtained, mostly aiming at measurements of angular diameters and binaries, with a total of 54 results in these fields. We use this database to investigate and discuss quantitatively the performance of the technique, in particular with respect to the limiting angular resolution, the limiting magnitude, the influence of the background and the probability of detection of a binary star under different conditions of observation. For the most important of these quantities, the limiting angular resolution φR, we find a dependence on the signal-to-noise ratio (SNR) that, within experimental errors, has the form of a power law. We also recognize and discuss the role played by the sampling time and scintillation effects. Finally, we describe briefly the fast photometric mode implemented in the TIRGO facility IR array-detector camera, which since late 1995 is also used routinely to record lunar occultations. Publication: The Astronomical Journal Pub Date: December 1996 DOI: 10.1086/118221 Bibcode: 1996AJ....112.2786R Keywords: OCCULTATIONS; INSTRUMENTATION: PHOTOMETERS full text sources ADS | data products SIMBAD (147) CDS (1)

Combined analysis of intracellular calcium with dual excitation fluorescence photometry and imaging

We have developed an integrated microscopy system combining fast dual-excitation fluorescence photometry and digital image analysis with high spatial resolution, based mainly on standard components. With the combination of these well-established techniques in one setup it is possible to monitor intracellular calcium with both sufficiently high temporal and high spatial resolution on the same preparation for many biological applications. Our system consists of a commercially available dual-excitation photometric system, an attached intensified charge coupled device (ICCD) camera, and a frame grabber board. With this integrated setup one can easily switch between the fast photometric mode (vratio = 100 Hz) and the imaging mode (vratio = 4.l7 up to 17 Hz). We used the system to record Fura-2 calcium images (340/380 nm ratios), which were correlated with the faster spot measurements and were analyzed by means of image processing. As an example for its application we reconstructed caffeine-induced calcium transients released from the sarcoplasmic reticulum of isolated and permeabilized skeletal muscle fiber preparations. Such a combined technique will also be important for cellular studies using other fluorescence indicators. Additionally, the described system has an external trigger facility that enables combination with other cell physiological methods, e.g., electrophysiological techniques.

Initial results from the extreme ultraviolet explorer

Data obtained during the first five months of calibration and science operation of the Extreme Ultraviolet Explorer (EUVE) are presented. Spectra of an extragalactic object were obtained; the object is detectable to wavelengths longer than 100Å, demonstrating that extragalactic EUV astronomy is possible. Spectra of a hot white dwarf, and a late-type star in quiescence and flaring are shown as examples of the type of spectrographic data obtainable with EUVE. Other objects for which broad band photometric mode data have been obtained and analyzed include an RS CVn star and several late-type stars. The backgrounds in the EUVE detectors are quite low and the character of the diffuse astronomical EUV background has been investigated using these very low rates. Evidence is presented showing that, contrary to previously published reports, EUVE is about three times more sensitive than the English Wide Field Camera in the short wavelength bandpass covered by both instruments. Only limited information has been extracted from the longer bandpasses covered only by EUVE. Nonetheless, the brightest EUV source in the sky, a B star, has been discovered and is detected only in these longer bandpasses.