Transformations between 2MASS, SDSS and BVRI photometric systems: bridging the near-infrared and optical

We present colour transformations for the conversion of the Two Micron All Sky Survey (2MASS) photometric system to the Johnson–Cousins UBVRI system and further into the Sloan Digital Sky Survey (SDSS) ugriz system. We have taken SDSS gri magnitudes of stars measured with the 2.5-m telescope from SDSS Data Release 5 (DR5), and BVRI and   JHK _s   magnitudes from Stetson's catalogue and Cutri et al., respectively. We matched thousands of stars in the three photometric systems by their coordinates and obtained a homogeneous sample of 825 stars by the following constraints, which are not used in previous transformations: (1) the data are dereddened, (2) giants are omitted and (3) the sample stars selected are of the highest quality. We give metallicity, population type and transformations dependent on two colours. The transformations provide absolute magnitude and distance determinations which can be used in space density evaluations at short distances where some or all of the SDSS ugriz magnitudes are saturated. The combination of these densities with those evaluated at larger distances using SDSS ugriz photometry will supply accurate Galactic model parameters, particularly the local space densities for each population.     

The regression of effective temperatures in APOGEE and LAMOST

We use the random forest to regress the surface effective temperatures of stars in APOGEE from SDSS DR16 and LAMOST DR6. When the NUV-u, u-g, g-r, r-i, i-J, J-H, H-K, K-WISE_4_5 magnitudes are used as machine learning features, the coefficient of determination of regression are 94.91% in APOGEE and 90.46% in LAMOST. The standard deviation of the prediction and pipeline temperatures are 93.89K in APOGEE and 113.10K in LAMOST. When the NUV-J, J-H, H-K, K-WISE_4_5 magnitudes are used as features, the coefficient of determination of regression are 94.37% in APOGEE and 88.89% in LAMOST. The standard deviation is 96.59K in APOGEE and 119.92K in LAMOST. The J-H magnitudes are the most important feature to predict the effective temperatures, and the NUV-J magnitudes are the second important feature. The NUV-J, J-H, H-K, K-WISE_4_5 magnitudes are from the all-sky survey and can be employed widely to regress the effective temperatures of stars.     

Absolute Magnitudes of Be Stars Based on Hipparcos Parallaxes

The absolute visual magnitudes of 457 Be stars are determined from Hipparcos parallaxes, subsequently the mean absolute visual magnitudes of Be stars for luminosity classes III, IV and V are obtained. The new Mv calibration is compared with existing calibrations. It is found that Be stars are generally brighter than B stars of the corresponding spectral types, and that there is no direct correlation between absolute magnitudes and the stellar rotational velocity, these results are in agreement with some earlier results. A new and interesting result is that there is no direct correlation between near infrared excess and absolute visual magnitudes for Be stars. Moreover, possible biases, such as the Malmquist bias and the Lutz–Kelker bias, are also discussed.     

Time to Perform the Physical Observations of Asteroids

The astrometric observations of asteroids are often performednear their opposition, where they have faster apparent motions andbrighter visual magnitudes. However, the physical observations ofasteroids (photometric and spectral) often require longer exposuretimes as well as brighter magnitudes for better signal-to-noiseratio, which are combined effects of both apparent moving speedsand visual magnitudes. We derive the equations of the apparentmotion of asteroid in geocentric ecliptic coordinates. Comparisonof the apparent magnitudes of asteroid at opposition and atstationary shows that the magnitude differences in the two casesare around 1 magnitude in average for most main belt asteroids,but are much larger for Near Earth Asteroids. Combining withcomparison of asteroid apparent motion, the proper time forasteroid physical observation in different cases are discussed.     

An analysis of Almagest magnitudes for the study of stellar evolution

Visual magnitude data in Ptolemy's Almagest are analysed by comparing them with modern photoelectric magnitudes on the Pogson scale, after taking extinction into account. The results show that a linear relationship exists between Almagest and Pogson scales, contrary to the findings of earlier authors, with one Almagest magnitude being equal to about 1.36 Pogson magnitudes. This result is used to transform Almagest magnitudes to the Pogson scale. A study is made of changes in the visual magnitudes of supergiant stars in the Almagest between classical and modern times (an interval of nearly 19 centuries). No evidence is found for any secular changes in the mean brightness of these stars, contrary to the conclusion of Mayer (Observatory 104, 77 (1984)). However, it is shown that the Almagest magnitudes for stars in the Milky Way are on average 0.34 Pogson magnitudes too faint, and about half the Almagest supergiants are affected by this. Finally, some evidence is cited for the visual atmospheric extinction in classical times being significantly less than today. If this is the case, and it is not taken into account, it would mimic an apparent supergiant brightening of about 0.1 magnitudes over this time interval.     

Model for surface reactions on interstellar grains — A numerical study

A model of the formation of molecules by surface reactions on interstellar grains is described and assessed numerically. The model predicts that for the molecules—other than H₂-likely to be important in the interstellar medium, the formation rates by surface reactions are insensitive to the nature of the surface. The formation rates have magnitudes which are significant when compared with other routes. The model also describes H₂ formation in high density clouds and shows it to be parameter dependent.     

The visual appearance of artificial satellites

The paper lists the stellar magnitudes of satellites observed from the U.K. during 1965. Statistically derived values are given which describe the fluctuating or constant magnitudes and the rates of flashing.     

Polarization results of solar X-rays from OSO-7

Polarization measurements of solar X-ray events that were obtained with an instrument on OSO-7 are presented. The results appear to be consistent with the results of Tindo et al. on the existence and magnitudes of polarization. A comparison with polarization predictions when X-rays are produced by radial beams of electrons gives two examples of deviations from such a model.     

Effect of changes in magnitudes of QSOs in their redshift distribution

Strong emission lines may change the brightness of QSOs and hence their observed magnitudes. Since different lines will affect the magnitudes by entering a particular filter at different redshifts, this effect may alter the number of QSOs at a particular redshift and hence the redshift distribution. The present analysis shows that the influence of the emission lines on the U and B magnitudes are significantly correlated to the redshift distribution. It is concluded that the changes in observed magnitudes of QSOs caused by the emission lines have significant effects on the present redshift distribution.     

The possiblity of detection of ultracool dwarfs with the UKIRT Infrared Deep Sky Survey

We present predictions for the numbers of ultracool dwarfs in the Galactic disc population that could be detected by the WFCAM/UKIDSS Large Area Survey and Ultra Deep Survey. Simulated samples of objects are created with masses and ages drawn from different mass functions and birthrates. Each object is then given absolute magnitudes in different passbands based on empirically derived bolometric correction versus effective temperature relationships (or model predictions for Y dwarfs). These are then combined with simulated space positions, velocities and photometric errors to yield observables such as apparent magnitudes and proper motions. Such observables are then passed through the survey selection mechanism to yield histograms in colour. This technique also produces predictions for the proper motion histograms for ultracool dwarfs and estimated numbers for the as yet undetected Y dwarfs. Finally, it is shown that these techniques could be used to constrain the ultra-low-mass mass function and birthrate of the Galactic disc population.     

Contemporary kinematics of the Upper Rhine Graben: A 3D finite element approach

The Upper Rhine Graben (URG), a Cenozoic intra-plate rift situated in the Alpine foreland, is presently characterised by relative slow tectonic deformation and low to medium seismicity. Concurrently, it is a region with a significant amount of ongoing subsidence in two recent depocentres (0.1 to 0.2 mm/a geological, 1 mm/a geodetical rate). In this paper, the recent kinematic behaviour of the URG is simulated using a 3D finite element model, containing three lithospheric layers (upper mantle, lower crust and upper crust) with different rheological properties. First order fault structures (e.g. border faults) are implemented as frictional contact surfaces within the upper crustal layer. The stresses generated by applying lateral displacements over a time period of 10 ka are insufficient to obtain a match between predicted and observed stress magnitudes. Therefore, a technique of “combined pre-stressing” has been developed to avoid unrealistic deformation and unrealistic stress magnitudes within the model. The stress magnitudes and stress directions predicted are calibrated against in-situ stress measurements and stress indicator data. For benchmarking of the modelling results, the vertical surface displacements predicted are compared to surface uplift derived from geological and geomorphological data. Furthermore, predicted fault slip rates are compared to available geological and geodetical data. Parameters derived from the calculated stress tensor, such as fracture potential and the regime stress ratio are also analysed in order to describe the possible kinematic behaviour of the URG. The modelling results suggest that the URG is currently being reactivated as a sinistral strike–slip system with the central segment of the URG forming a restraining bend and the two recent depocentres situated in releasing bend settings. The modelling results suggest that both sinistral shearing and mantle uplift are active mechanisms driving the recent kinematics of the URG and that the recent subsidence within the two depocentres is re-enforced by ongoing mantle uplift additionally.     

Systematic Errors of High–Precision Photometric Catalogues

A very accurate imitation of Hipparcos and Tycho Hp, B _T, andV _T magnitudes was made using W, B, V, R magnitudes from the Tien Shan photometric catalogue. The calculated magnitudes were compared to the observed ones. It is shown that there are systematic differences between calculated and observed magnitudes. The systematic errors are supposed to be bound up with the sky scanning procedure on the Hipparcos satellite. Polynomials in powers of coordinates have been proposed to take into account the systematic errors. 6558 stars have been found to be appropriate high-precision photometric standards. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimated Visual Magnitudes of the EISCAT UHF Meteors

We have investigated the conditions for simultaneous meteor observations with the EISCAT UHF radar system and telescopic optical devices. The observed characteristics of 410 meteors detected by all three UHF receivers are compared with model simulations and their luminosity is calculated as a part of a meteoroid ablation model using a fifth order Runge–Kutta numerical integration technique. The estimated absolute visual magnitudes are in the range of +9 to +5. The meteors should therefore be observable using intensified CCD or EMCCD (Electron Multiplying CCD) cameras with telephoto lenses. A possible setup of a coordinated radar and optical campaign is suggested.     

Photoelectric activity of the shell staro And: New observations and discussion

Photoelectric observations of the shell staro And, obtained in 1979, are presented. The star shows variations of some hundredth of magnitudes during a few hours. The trend to retake the values of the luminosity and colour indices prior to the reduction happened between JD 42,714-27, seems to continue. We also give a qualitative model which explains satisfactorily the main features observed after the 1975 shell episode.     

Flux Calibration of the BATC Survey and Its Application for Checking the Consistency of the Oke—Gunn Standards

1 INTRODUCTIONThe B eij lug- Ahs ona~ TaiP ei- C onnect lout Color S urvey of t he S by (Hereaft er B AT C ) ut driesthe 15 intermediate band filters to make CCD forage photometric ohs~ion. The BATCphotometric system ties its maghtude zero P~Oint to the spectro-photometric AB maghtudesystem. The AB system is a monochro~ic fi system fort introduced by Oke in 1969 with aprovisional calibration designated AB69.The AB system selects F subdwarfs around visual magnitude 9 as standa…     

<Emphasis Type="Italic">BVRI</Emphasis> CCD-photometry of comparison stars in the neighborhoods of galaxies with active nuclei. III

Observations with a matrix photometer are reported. The stellar magnitudes in the BVRcIc bands are estimated for 80 comparison stars in the neighborhoods of 10 galaxies with active nuclei: 2 Seyfert galaxies, 4 quasars, and 4 BL Lac objects. The stellar magnitudes of the observed stars range from 11 to 19^m.5. For stars with magnitudes of 14–15^m the typical photometric errors are 0^m.011, 0^m.008, 0^m.006, and 0^m.007 in the B, V, R, and I bands, respectively. The BVRI magnitudes for most of these stars were not known previously. 14′ × 14′ finding charts for these stars are included. These results can be used for differential BVRI photometry of active galactic nuclei. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 57–72 (February 2007).     

CCD photometry of seyfert galaxies

Morphology and elliptically averaged luminosity profiles have been derived from CCD surface photometry of thirteen seyfert galaxies. ApparentV andI magnitudes,V-I colour index, as well as absolute Mv and MI magnitudes have been calculatedV andI luminosity profiles of Mk 10, Mk 79, Mk 358, Mk 618, Mk 352, and Mk 110, are adjusted by the usual model bulge plus disk with structural parameters comparable to those observed in normal spirals. The averaged luminosity profiles of Mk 50, Mk 124, Mk 348, and 3C227 are fitted byr ^–1/4 law with structural parameters similar to those observed in ellipticals and red compact galaxies. Mk 42 and NGC 985 show disturbed luminosity profiles.     

Study of the inner satellites of Saturn by photographic photometry

Good photographs of Saturn and its five inner satellites were obtained on January 2, 1974 with the 105 cm telescope at Pic du Midi Observatory with exposure times of 45 sec. The spread function is constant over the field, and isotropic. The true photometric profiles of the satellites are obtained after deriving a model for the stray light coming from the rings. The magnitudes, computed by integration, are in good agreement with published values except for Mimas, which is nearly one magnitude fainter then previously believed.     

Predicted star counts and mean parallaxes down to the 23rd magnitude

Star counts and mean parallaxes as a function of B, V, R magnitudes down to 23 are presented. The data were computed by the use of two fundamental equations of stellar statistics. The assumed model considers the Galaxy as a symmetrical system with respect to its rotation axis and to its equatorial plane and as composed of the thin disk (main sequence and red giants), the thick disk and spheroid populations. Numbers of stars and mean parallaxes were derived in bins of galactic longitude and latitude of 30° and 10°, respectively. For the computation of the mean parallaxes depending on Galactic coordinates and magnitudes, series of products of Hermite and Legendre polynomials and of Fourier terms were used. The results of this paper may help in the planning of future survey missions and in the design of new telescopes. In addition, mean parallaxes can be used to derive corrections to absolute parallaxes and proper motions for any position in the sky.     

The magnitude and color of the Saturn system

Brightness measurements made during 1963-1965 and 1991-2009 are used in constructing models of the brightness of the Saturn system in the Johnson B, V, R and I system. The models cover nearly the full range of phase angles and ring opening angles visible from the Earth and are believed to be accurate to 0.03-0.05 magnitudes. A U-filter model is also selected which covers ring opening angles of between 4° and 14°. The model is the first such one that treats the light from the rings as a function of the saturnicentric latitude from the Earth and Sun in a way that is consistent with observations and theoretical considerations. Six conclusions of this work are: (1) the Saturn system brightens as the solar phase angle decreases, (2) the Saturn system has an opposition surge, (3) the opposition surge increases as the ring opening angle increases, (4) the solar phase angle coefficient increases as the ring opening angle increases, (5) the B-V, V-R and R-I color indexes change by up to 0.2 magnitudes as Saturn orbits the Sun and (6) the V-filter model in this report is a better fit to the 1963-2009 data than the one proposed by Harris (Harris, D.L. [1961]. In: Kuiper, G.P., Middlehurst, B.M. (Eds), Planets and Satellites. Univ. of Chicago, Chicago, IL, pp. 272-342].