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Near-Infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared-luminous Galaxy NGC 4418
We present near-infrared and millimeter investigations of the nucleus ofthe infrared-luminous galaxy NGC 4418, which previous observationssuggest possesses a powerful buried active galactic nucleus (AGN). Wefind the following main results: (1) The infrared K-band spectrum showsCO absorption features at 2.3-2.4 μm from stars and very strongH2 emission lines. The luminosity ratios of H2emission lines are suggestive of a thermal origin, and the equivalentwidth of the H2 1-0 S(1) line is the second largest observedto date in an external galaxy, after the well-studied strongH2-emitting galaxy NGC 6240. (2) The infrared L-band spectrumshows a clear polycyclic aromatic hydrocarbon (PAH) emission feature at3.3 μm, which is usually found in star-forming galaxies. Theestimated star formation luminosity from the observed PAH emission canaccount for only a small fraction of the infrared luminosity. (3)Millimeter interferometric observations of the nucleus reveal a high HCN(1-0) to HCO+ (1-0) luminosity ratio of ~1.8, as has beenpreviously found in pure AGNs. (4) The measurements of HCN (1-0)luminosity using a single-dish millimeter telescope show that the HCN(1-0) to infrared luminosity ratio is slightly larger than the average,but within the scattered range, for other infrared-luminous galaxies.All of these results can be explained by the scenario in which, inaddition to energetically insignificant, weakly obscured star formationat the surface of the nucleus, a powerful X-ray-emitting AGN deeplyburied in dust and high-density molecular gas is present.
| L' and M' standard stars for the Mauna Kea Observatories Near-Infrared system
We present L' and M' photometry, obtained at the United Kingdom InfraredTelescope (UKIRT) using the Mauna Kea Observatories Near-Infrared(MKO-NIR) filter set, for 46 and 31 standard stars, respectively. The L'standards include 25 from the in-house `UKIRT Bright Standards' withmagnitudes deriving from Elias et al. and observations at the InfraredTelescope Facility in the early 1980s, and 21 fainter stars. The M'magnitudes derive from the results of Sinton and Tittemore. We estimatethe average external error to be 0.015 mag for the bright L' standardsand 0.025 mag for the fainter L' standards, and 0.026 mag for the M'standards. The new results provide a network of homogeneously observedstandards, and establish reference stars for the MKO system, in thesebands. They also extend the available standards to magnitudes whichshould be faint enough to be accessible for observations with moderndetectors on large and very large telescopes.
| JHK Standard Stars on the CIT Photometric System
We present a set of 58 stars with JHK standard values on the CIT systemand with a suitable magnitude range for use with array detectors onsmall- to moderate-size telescopes. Each final value is based on six to47 measures (with a mean of 17) obtained on separate nights with the USNaval Observatory (USNO) NICMOS3 (HgCdTe) camera. The objects include 20primary CIT standards from Elias et al. and 38 secondary sourcesselected from the SAAO and UKIRT standards lists, cover a K-magnituderange between 6.0 and 10.8, and lie north of declination -20°. Thestars were reduced to the CIT system as defined by Elias et al.,producing a USNO system that is identical to the near-infrared CITsystem. This work densifies the original CIT system by nearly a factorof 3 and extends its range by about 3 mag. The SAAO and UKIRT standardsare also compared with the CIT system.
| High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere
We present the results of 8 yr of infrared photometric monitoring of alarge sample of stars visible from Teide Observatory (Tenerife, CanaryIslands). The final archive is made up of 10,949 photometric measuresthrough a standard InSb single-channel photometer system, principally inJHK, although some stars have measures in L'. The core of this list ofstars is the standard-star list developed for the Carlos SánchezTelescope. A total of 298 stars have been observed on at least twooccasions on a system carefully linked to the zero point defined byVega. We present high-precision photometry for these stars. The medianuncertainty in magnitude for stars with a minimum of four observationsand thus reliable statistics ranges from 0.0038 mag in J to 0.0033 magin K. Many of these stars are faint enough to be observable with arraydetectors (42 are K>8) and thus to permit a linkage of the bright andfaint infrared photometric systems. We also present photometry of anadditional 25 stars for which the original measures are no longeravailable, plus photometry in L' and/or M of 36 stars from the mainlist. We calculate the mean infrared colors of main-sequence stars fromA0 V to K5 V and show that the locus of the H-K color is linearlycorrelated with J-H. The rms dispersion in the correlation between J-Hand H-K is 0.0073 mag. We use the relationship to interpolate colors forall subclasses from A0 V to K5 V. We find that K and M main-sequence andgiant stars can be separated on the color-color diagram withhigh-precision near-infrared photometry and thus that photometry canallow us to identify potential mistakes in luminosity classclassification.
| Near infrared coronagraph images of IRC +10216. Faint structures at 1-5arcsec from the central star
We present J, H and K band coronagraph images of the circumstellarenvelope around IRC +10216 (CWLeo) obtained with a near infrared camera, CIAO and the 8.2 mSubaru telescope. A circular occulting mask of 2arcsec in diameter wasused to block out the light from the bright central object. The imagesshow 2 collimated radial structures to the NNW and WNW, 2 fan-likestructures to the S and NE, respectively, and 3 arc-like structures at aradius of 4 to 5 arcsec from the stellar center. We compare thisintermediate size-scale structure to that seen on larger and smallerscales and find evidence for a deviation from spherically symmetricoutflow beginning ~ 150 years ago. Previous near infrared speckleimaging has revealed a complex clumpy structure on a scale of less than200 mas, and it is likely that at least some of the radial features seenin our images could be due to shadowing by dust clumps close to thestar.
| Protoplanetary Disks in the Nearest Star-Forming Cloud: Mid-Infrared Imaging and Optical Spectroscopy of MBM 12 Members
The recent identification of several groups of young stars within 100 pcof the Sun has generated widespread interest. Given their proximity andpossible age differences, these systems are ideally suited for detailedstudies of star and planet formation. Here we report on the firstinvestigation of protoplanetary disks in one such group, thehigh-latitude cloud MBM 12 at a distance of ~65 pc. We presentmid-infrared observations of the eight candidate pre-main-sequence (PMS)members and the two main-sequence (MS) stars in the same line of sight,which may or may not be associated with the group. We have also derivedHα and Li line widths from medium-resolution optical spectra. Wereport the discovery of significant mid-infrared excess from six PMSstars-LkHα 262, LkHα 263, LkHα 264, E02553+2018, RXJ0258.3+1947, and S18-presumably due to optically thick circumstellardisks. Our flux measurements for the other two PMS stars and the two MSstars are consistent with photospheric emission, allowing us to rule outdusty inner disks. The disks we have found in MBM 12 represent thenearest known sample of very young protoplanetary systems and thus areprime targets for high-resolution imaging at infrared and millimeterwavelengths.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| Optical and infrared photometry of the Type IIn SN 1998S: days 11-146
We present contemporaneous optical and infrared (IR) photometricobservations of the Type IIn SN 1998S covering the period between 11 and146d after discovery. The IR data constitute the first ever IR lightcurves of a Type IIn supernova. We use blackbody and spline fits to thephotometry to examine the luminosity evolution. During the first 2-3months, the luminosity is dominated by the release of shock-depositedenergy in the ejecta. After ~100d the luminosity is powered mostly bythe deposition of radioactive decay energy from0.15+/-0.05Msolar of 56Ni which was produced inthe explosion. We also report the discovery of an astonishingly high IRexcess, K-L'=2.5, that was present at day 130. We interpret this asbeing due to thermal emission from dust grains in the vicinity of thesupernova. We argue that to produce such a high IR luminosity so soonafter the explosion, the dust must be pre-existing and so is located inthe circumstellar medium of the progenitor. The dust could be heatedeither by the UV/optical flash (IR echo) or by the X-rays from theinteraction of the ejecta with the circumstellar material.
| The dynamical evolution of the fragmented, bipolar dust shell around the carbon star IRC +10 216 . Rapid changes of a PPN-like structure?
We present high-resolution J-, H-, and K-band observations and the firstH-K color image of the carbon star IRC +10 216. Theimages were reconstructed from 6 m telescope speckle interferogramsusing the bispectrum speckle interferometry method. The H and K imageswith resolutions between 70 mas and 92 mas consist of several compactcomponents within a 0\farcs2 radius and a fainter asymmetric nebula. Thebrightest four components are denoted with A to D in the order ofdecreasing brightness in the 1996 image. A comparison of our images from1995, 1996, 1997, and 1998 gives -- almost like a movie of five frames-- insight into the dynamical evolution of the inner nebula. Forinstance, the separation of the two brightest components A and Bincreased from 191 mas in 1995 to 265 mas in 1998. At the same time,component B is fading and the components C and D become brighter. TheX-shaped bipolar structure of the nebula, most prominently present inthe J-band image, implies an asymmetric mass-loss. Such asymmetries areoften present in protoplanetary nebulae but are unexpected for AGBstars. IRC +10 216 is thus likely to be very advancedin its AGB evolution, shortly before turning into a protoplanetarynebula. The cometary shapes of A in the H and J images and in the 0.79mu m and 1.06 mu m HST images suggest that the core of A is not thecentral star, but the southern lobe of a bipolar structure. The positionof the central star is probably at or near the position of component B,where the H-K color has a value of 4.2. If the star is at or near B,then the components A, C, and D are likely to be located at the innerboundary of the dust shell. Based on observations performed with the 6~mtelecope at the Special Astrophysical Observatory, Russia.
| Do galaxy mergers form elliptical galaxies? A comparison of kinematic and photometric properties
We present near-infrared K-band imaging and spectroscopy of a sample ofgalaxy mergers, which we use to derive light profile indices, absolutemagnitudes and central velocity dispersions. We find that the lightdistributions of mergers more nearly resemble those of ellipticals thanthose of bulges, but that the mergers lie well away from the FundamentalPlane defined by the ellipticals. We interpret this as being due toenhancement of the K-band surface brightness of the mergers by asignificant population of supergiant stars, and independent evidence forsuch a population is inferred from measurements of the depth of the2.3-μm CO absorption feature.
| New Near-Infrared Spectroscopy of the High-Redshift Quasar B1422+231 at Z = 3.62
We present new near-infrared (rest-frame UV-to-optical) spectra of thehigh-redshift, gravitationally lensed quasar B1422+231 (z=3.62).Diagnostic emission lines of Fe II, O III lambda5007, and Hβ,commonly used to determine the excitation, ionization, and chemicalabundances of radio-quiet and radio-loud quasars, were detected. Our newdata show that the ratio Fe II (UV)/Hβ=18.1+/-4.6 and Fe II(optical)/Hβ=2.3+/-0.6 are higher than those reported by Kawara etal. by factors of 1.6 and 3.3, respectively, although the ratio [O III]lambda5007/Hβ=0.19+/-0.02 is nearly the same between the twomeasurements. The discrepancy of the line flux ratios between themeasurements is likely due to improved data and fitting proceduresrather that to intrinsic variability. While approximately half of thehigh-z quasars observed to date have much more extreme Fe II(optical)/Hβ ratios, the line ratio measured for B1422+231 areconsistent with the observed range of Fe II (optical) ratios of low-zquasars.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Near-Infrared Spectroscopy of the High-Redshift Quasar S4 0636+68 at Z = 3.2
We present near-infrared (observed frame) spectra of the high-redshiftquasar S4 0636+68 at z = 3.2, which was previously thought to be one ofa group of ``strong'' Fe ii emitters [i.e., F(Fe iilambdalambda4434-4684)/F(Hβ) > 1]. Our K-band spectrum clearlyshows emission lines of Hβ and [O iii] lambdalambda4959, 5007, aswell as optical Fe ii emission. Our computed value of F(Fe iilambdalambda4434-4684)/F(Hβ) ~= 0.8 for S4 0636+68 is less thanpreviously thought and, in fact, is comparable to values found forradio-loud, flat-spectrum, low-z quasars. Therefore S4 0636+68 appearsnot to be a strong optical Fe ii emitter. Although more than half (5/8)of the high-z quasars observed to date are still classified as strongoptical Fe ii emitters, their Fe ii/Hβ ratios, for the most part,follow the same trend as do those of low-z quasars, i.e., ananticorrelation in EW(Fe ii)/EW(Hβ) versus EW([O iii])/EW(Hβ),with radio-loud quasars having a mean value of EW(Fe ii)/EW(Hβ)approximately half that of radio-quiet quasars at comparable values ofEW([O iii])/EW(Hβ).
| The near-infrared extinction law and limits on the pre-main-sequence population of the Rho Ophiuchi dark cloud
We describe new techniques to measure the NIR extinction law and toplace limits on the premain-sequence stellar population of a dark cloud.We analyze JHK imaging data for the central 1 sq deg of the Rho Ophiuchicloud core and show that nearly all stars projected onto regions of lowCS intensity, ICS 10 K km/s, are background stars. Most sources atlarger CS intensities lie within cloud material. We use the backgroundstars to derive the slope of the NIR extinction law, E(J-H)/E(H-K) =1.57 +/- 0.03. This result is consistent with previous extinction lawsbut has a factor of two to three smaller uncertainty. The new Rho Ophextinction law yields strong constraints on the number of previouslyundiscovered premain-sequence stars in the cloud, 46 +/- 11, and thenumber of previously undiscovered young stars with near-IR excesses, 15+/- 4. Neither limit exceeds the number of known premain-sequence starsin the cloud about 100. Thus, current samples of premain-sequence starsare reasonably complete for K = 14 or less.
| Near infrared surface photometry of late-type Virgo cluster galaxies
Near Infrared (K' band) surface photometry has been obtained for 102 (88late-type) Virgo cluster galaxies. A subset of 20 galaxies was alsoimaged in the H band. Magnitudes and diameters within the 21.5 and 22.0mag arcsec$^{-2}$ isophote, concentration indices and total H and K'magnitudes are derived. Basic statistical properties of a completesample of spiral galaxies spanning the range 6.3 < K'_T < 13.5 aregiven. Tables 3, 5 and 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html} Based on observations taken atthe Calar Alto Observatory, operated by the Max-Planck-Institut furAstronomie (Heidelberg) jointly with the Spanish National Commission forAstronomy.
| Near-Infrared Surface-Photometry of Edge-on Scd Galaxies, NGC 3556 and NGC 4244
Near-infrared images in the J and K' bands of two edge-on late-typegalaxies, NGC 3556 and NGC 4244, were obtained with the newly developedcommon-use instrument for infrared imaging and spectroscopy at theOkayama Astrophysical Observatory (OASIS). These images were analyzed toyield the surface-photometric and model parameters for the globalstructure of these Scd galaxies. NGC 3556 shows a disk and a bar-likestructure, both of which have an approximately exponentialsurface-brightness distribution. The absorption feature of NGC 3556 iscomplex, and only the most prominent central dark lane of A_J<0.5 wastaken into the modeling. NGC 4244 comprises a disk and a weak bulge,both having an approximately exponential surface-brightnessdistribution, suffering under negligible internal absorption by a faintdark lane of A_J<0.1. Global models of the 3-D emissivity structureand absorption layer have been constructed to reproduce the observedmain features. The global models indicate that both galaxies areoptically thin in the V band when seen face on (tau_ {0,V} < 0.4),with the reservation of a possible presence of locally opaque structuresin NGC 3556. Brief discussions are given concerning the insufficiency ofsimple absorption-layer models and the strong contrast between the twoScd galaxies regarding their interstellar matter and star-formingactivities.
| IR Spectroscopy of the Gravitationally Lensed Quasar B1422+231: Mg II lambda 2798 and Fe II Emission from the Broad-Line Gas at Z = 3.62
The rest-frame UV-optical (2000--5300 A) spectrum of the gravitationallylensed flat-spectrum radio-loud quasar B1422+231 system at z = 3.62 ispresented. The spectrum is similar to the Large Bright Quasar Survey(LBQS) composite spectrum (Francis et al.), which indicates nosignificant UV-optical spectral evolution in some quasars at 0 < z< 3.6. The Fe II(UV + optical)/Mg II lambda 2798 flux ratio is 12.2+/- 3.9, which is comparable to 8.9 for the LBQS composite spectrum ofquasars at z = 1--2 analyzed in this work, and 7.8 +/- 2.6 for quasarsat z = 0.15--0.63 analyzed by Wills, Netzer, & Wills. It isconcluded that the majority of stars in the host galaxy of B1422+231have formed much earlier (~1.5 Gyr) than z = 3.6. The first detection of[O III] lambda 5007 in a quasar beyond z = 3 is also reported.
| Determination of effective temperatures for an extended sample of dwarfs and subdwarfs (F0-K5).
We have applied the InfraRed Flux Method (IRFM) to a sample of 475dwarfs and subdwarfs in order to derive their effective temperatureswith a mean accuracy of about 1.5%. We have used the new homogeneousgrid of theoretical model atmosphere flux distributions developed byKurucz (1991, 1993) for the application of the IRFM. The atmosphericparameters of the stars cover, roughly, the ranges:3500K<=T_eff_<=8000K -3.5<=[Fe/H]<=+0.53.5<=log(g)<=5. The monocromatic infrared fluxes at the continuum,and the bolometric fluxes are derived using recent results, whichsatisfy the accuracy requeriments of the work. Photometric calibrationshave been revised and applied to estimate metallicities, although directspectroscopic determinations were preferred when available. The adoptedinfrared absolute flux calibration, based on direct optical measurementsof angular stellar diameters, sets the effective temperatures determinedusing the IRFM on the same scale than those obtained by direct methods.We derive three temperatures, T_J_, T_H_ and T_K_, for each star usingthe monochromatic fluxes at different infrared wavelengths in thephotometric bands J, H, and K. They show good consistency over 4000 K,and no trend with wavelength may be appreciated. We provide a detaileddescription of the steps followed for the application of the IRFM, aswell as the sources of the errors associated to the different inputs ofthe method, and their transmission into the final temperatures. We alsoprovide comparison with previous works.
| The empirical scale of temperatures of the low main sequence (F0V-K5V).
We have calibrated the effective temperatures of the low main sequencestars ranging spectral types from F0 to K5 versus [Fe/H] and colours(B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and ubvy-β, using alarge sample of dwarfs and subdwarfs. The effective temperatures, scaledto direct T_eff_ determinations via reliable angular diametermeasurements, were derived applying the InfraRed Flux Method with thenew grid of atmosphere models developed by Kurucz (1993). We have fittedpolynomial functions of the form θ_eff_=P(colour,[Fe/H]) usingthe least squares method. The precision of the fits ranges from 30K for(V-K) to 154K for (J-H). The new relations have been compared toprevious calibrations. We also provide the empirical intrinsic colours(U-B), (B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and β, inthe ranges: 4000K[Fe/H]>-2.5.
| Fainter Southern JHK Standards Suitable for Infrared Arrays
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995MNRAS.276..734C&db_key=AST
| Near-infrared imaging of the Herbig-Haro object HH124
We report our findings from near-infrared imaging of the Herbig-Haroobject HH124. The outflow driving source is found to be deeply embeddednear the symmetry centre of the outflow. This near-infrared source,which we identify with IRAS 06382+1017, is associated with an infraredreflection nebula. The reflection nebula morphology and the spatialdistribution of H_2 emission in the vicinity of HH124D lead us topropose, as one possibility, the existence of two outflows. Analternative interpretation of the reflection nebula morphology isreflection off a dusty torus situated in the equatorial plane of IRAS06382+1017. We also report a tentative detection of Brgamma emissionassociated with IRAS 06382+1017. This emission may originate from thecircumstellar accretion disc's boundary layer or from a stellar wind,and indicates that IRAS 06382+1017 is a young, active T Tauri star. TheH_2 1-0 S(1) emission in HH124 is clumpy, especially in HH124C. Theoverall spatial distribution of the H_2 emission in the different shockfronts is consistent with emission on the wings of bow shocks with ahigher shock velocity for HH124C than for HH124E.
| M Giant Kinematics in Off-Axis Fields between 150 and 300 Parsecs from the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...449..623B&db_key=AST
| Near Infrared Imaging of Dwarf Ellipticals Irregulars and Blue Compact Galaxies in the Virgo Cluster
New near-IR images are presented for 13 dwarf galaxies in the Virgocluster. Together with previous data these provide a data base of JHKimaging for 26 dwarf ellipticals (dEs), dwarf irregulars (dIs) and bluecompact dwarfs (BCDs). These images show the dIs to be highly asymmetricand unrelaxed, implying that they are dynamically young and unevolved.This is consistent with their blue near-IR and optical-IR colours whichare most easily explained by young stellar populations. The dEs aresymmetrical and apparently relaxed, with very uniform colours indicatingthat they are dominated by old stars. They generally have exponentiallight profiles, but the brighter galaxies tend to exhibit more cuspedlight distributions, similar to the de Vaucouleurs profiles of brightellipticals. The BCDs have moderately asymmetric light profiles, andparadoxically red colours, possibly indicating an intermediate-agestellar population. They are probably dEs which have undergone bursts ofstar formation in the last few X 10^9^ years, whilst the dIs are afundamentally distinct population. Colour gradients are present in manyof the galaxies, invariably in the sense that the nuclei are redder thanthe surrounding galaxy light.
| Deep Infrared Array Photometry of Globular Clusters. I. M4
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994ApJ...423..640D&db_key=AST
| Near-infrared calibration stars for the Teide Observatory
Not Available
| The unusual K-band characteristics of the gravitational lens system MG 1131 + 0456
The radio morphology of the gravitational lens system MG 1131 + 0456 isthat of an 'Einstein ring'. Newly obtained K-prime-band images of thesystem reveal the presence of an infrared bright object that has amorphology reminiscent of that seen in the radio. There are two brightobjects embedded in an elliptical halo; these seem to be the infraredcounterparts to the radio morphology. Two nearby objects have no radiocounterparts. All four objects have extremely red optical-infraredcolors: R - K greater than 6. Few extragalactic objects are this red. Aplausible candidate for the source object is an unusually red radiogalaxy.
| IR photometry of the stars in Terzan 2
The giant branch of the globular cluster Terzan 2 has been studied usingthe Infrared Imaging Camera at the United Kingdom Infrared Telescope. AnIR color-magnitude diagram of this object has been obtained to studythis cluster relative to clusters with known metallicities and ages todetermine independent estimates for the parameters relevant to Terzan 2.The Terzan clusters are important as they are among the most metal-richmembers of the so-called disk component of the globular cluster system,but they are located in a direction very close to the galactic center;hence, observations are particularly difficult due to interstellarobscuration. Assuming that the cluster has Fe/H about -0.25 (Armandroffand Zinn, 1988), Terzan 2 is found to be at an intrinsic distancemodulus of 15.0 +/-0.2 mag with a reddening E(B-V) = 1.25 +/-0.15. Atthe corresponding distance, 10 kpc, the cluster is located approximately440 pc above the disk, well within the bulge of the galaxy.
| Supernova 1991X in NGC 4902
IAUC 5263 available at Central Bureau for Astronomical Telegrams.IAUC 5263 available at Central Bureau for Astronomical Telegrams.
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| JHK infrared standard stars and absolute calibration of the San Pedro Martir Observatory (OAN) photometric system
A set of reliable standard stars for the JHK photometric system of theSan Pedro Martir National Observatory (OAN) is presented. Meanextinction coefficients for the near-IR of this site are first reportedhere; effective wavelengths and flux calibration from observations ofVega are derived for the various bandpasses. Comparison with otherwidely used photometric systems is presented and, finally,transformation equations to CIT, AAO, ESO, and Johnson's systems arederived.
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Virgo |
| Ascensió Recta: | 12h17m57.54s |
| Declinació: | +01°34'31.1" |
| Magnitud Aparent: | 7.54 |
| Distancia: | 250.627 parsecs |
| Moviment propi RA: | -26.2 |
| Moviment propi Dec: | -7.8 |
| B-T magnitude: | 7.658 |
| V-T magnitude: | 7.55 |
Catàlegs i designacions:
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