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New Relativistic Atomic Data for Fe IX
A large-scale configuration interaction (CI) calculation using ProgramCIV3 of Hibbert is performed for the lowest 87 fine-structure levels ofargon-like iron ions. We have calculated energy levels, oscillatorstrengths, and transition probabilities for all electric-dipole-allowedand intercombination transitions between the levels of3s23p6, 3s23p53d,3s3p63d, 3s23p54s,3s23p54p, 3s23p54d,3s3p64s, 3s23p54f, 3s3p64p,3s23p55s, 3s23p55p, and3s23p55d states of Fe IX in the LSJ couplingscheme. Lifetimes of the 3d levels are also determined. The calculationsinclude the major correlation effects. We attempt to correct theinaccuracies in the CI coefficients in the wave functions, which wouldlead to inaccuracy in transition probabilities by applying a``fine-tuning'' technique. The relativistic effects are incorporated byadding mass correction, Darwin term, and spin-orbit interaction terms tothe nonrelativistic Hamiltonian in the Breit-Pauli approximations. Thepresent results are in good agreement with other available calculationsand experiments. We predict new data for several levels where no othertheoretical or experimental results are available. We hope our extensivecalculations will be useful to experimentalists in identifying thefine-structure levels in their future work.
| Computed Hβ indices from ATLAS9 model atmospheres
Aims.Grids of Hβ indices based on updated (new-ODF) ATLAS9 modelatmospheres were computed for solar and scaled solar metallicities[+0.5], [+0.2], [0.0], [ -0.5] , [ -1.0] , [ -1.5] , [ -2.0] , [ -2.5]and for α enhanced compositions [+0.5a], [0.0a], [ -0.5a] , [-1.0a] , [ -1.5a] , [ -2.0a] , [ -2.5a] , and [ -4.0a] . Methods:.Indices for T_eff > 5000 K were computed with the same methods asdescribed by Lester et al. (1986, LGK86) except for a differentnormalization of the computed natural system to the standard system.LGK86 used special ODFs to compute the fluxes. For T_eff ≤ 5000 K wecomputed the fluxes using the synthetic spectrum method. In order toassess the accuracy of the computed indices comparisons were made withthe indices computed by Smalley & Dworetsky (1995, A&A, 293,446, MD95) and with the empirical relations T_eff-Hβ given byAlonso et al. (1996, A&A, 313, 873) for several metallicities.Furthermore, for cool stars, temperatures inferred from the computedindices were compared with those of the fundamental stars listed byMD95. The same kind of comparison was made between gravities for B-typestars. Results: .The temperatures from the computed indices are ingood agreement, within the error limits, with the literature values for4750 K ≤ T_eff ≤ 8000 K, while the gravities agree for T_eff> 9000 K. The computed Hβ indices for the Sun and for Procyonare very close to the observed values. The comparison between theobserved and computed Hβ indices as function of the observedHβ has shown a very small trend which almost completely disappearswhen only stars hotter than 10 000 K are considered. The trend due tothe cool stars is probably related with the low accuracy of thefundamental T_eff which are affected by large errors for most of thestars.
| Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I
We present a quantitative atlas and catalog of dark clouds derived byusing the optical database ``Digitized Sky Survey I''. Applying atraditional star-count technique to 1043 plates contained in thedatabase, we produced an AV map covering the entire region inthe galactic latitude range |b| ≤ 40°. The map was drawn at twodifferent angular resolutions of 6' and 18', and is shown in detail in aseries of figures in this paper. Based on the AV map, weidentified 2448 dark clouds and 2841 clumps located inside them. Somephysical parameters, such as the position, extent, and opticalextinction, were measured for each of the clouds and clumps. We alsosearched for counterparts among already known dark clouds in theliterature. The catalog of dark clouds presented in this paper lists thecloud parameters as well as the counterparts.
| Surface abundances of light elements for a large sample of early B-type stars - IV. The magnesium abundance in 52 stars - a test of metallicity
From high-resolution spectra a non-local thermodynamic equilibriumanalysis of the MgII 4481.2-Åfeature is implemented for 52 earlyand medium local B stars on the main sequence (MS). The influence of theneighbouring line AlIII 4479.9-Åis considered. The magnesiumabundance is determined; it is found that logɛ(Mg) = 7.67 +/-0.21 on average. It is shown that uncertainties in the microturbulentparameter Vt are the main source of errors inlogɛ(Mg). When using 36 stars with the most reliableVt values derived from OII and NII lines, we obtain the meanabundance logɛ(Mg) = 7.59 +/- 0.15. The latter value isprecisely confirmed for several hot B stars from an analysis of the MgII7877-Åweak line. The derived abundance logɛ(Mg) = 7.59 +/-0.15 is in excellent agreement with the solar magnesium abundancelogɛsolar (Mg) = 7.55 +/- 0.02, as well as with theproto-Sun abundance logɛps(Mg) = 7.62 +/- 0.02. Thus,it is confirmed that the Sun and the B-type MS stars in ourneighbourhood have the same metallicity.
| Variability of Stars in the Pulkovo Spectrophotometric Catalog
We present the results of a statistical study of brightness variabilityfor 693 stars of the Pulkovo spectrophotometric database in fivespectral bands in the range λλ 320 1080 nm. Significantbrightness variations were detected in at least one spectral bandagainst the background of the random noise for one-third of the starsnot earlier believed to be variable. A comparison of the distributionsof these variations in amplitude and spectral band for the normal andvariable stars shows that variability is inherent to most stars to someextent and is often wavelength dependent.
| The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence
We present far-ultraviolet (FUV) spectra of the classical T Tauri starRU Lup covering the 912-1710 Å spectral range, as observed by theHubble Space Telescope STIS and the Far Ultraviolet SpectroscopicExplorer satellite. We use these spectra, which are rich in emission andabsorption lines, to probe both the accreting and outflowing gas.Absorption in the Lyα profile constrains the extinction toAV~0.07 mag, which we confirm with other diagnostics. Weestimate a mass accretion rate of (5+/-2)×10-8Msolar yr-1 using the optical-NUV accretioncontinuum. The accreting gas is also detected in bright, broad lines ofC IV, Si IV, and N V, which all show complex structures across the lineprofile. Many other emission lines, including those of H2 andFe II, are pumped by Lyα. RU Lup's spectrum varies significantlyin the FUV; our STIS observations occurred when RU Lup was brighter thanseveral other observations in the FUV, possibly because of a high massaccretion rate.
| B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?
Projected rotational velocities (vsini) have been measured for 216 B0-B9stars in the rich, dense h and χ Persei double cluster and comparedwith the distribution of rotational velocities for a sample of fieldstars having comparable ages (t~12-15 Myr) and masses (M~4-15Msolar). For stars that are relatively little evolved fromtheir initial locations on the zero-age main sequence (ZAMS) (those withmasses M~4-5 Msolar), the mean vsini measured for the h andχ Per sample is slightly more than 2 times larger than the meandetermined for field stars of comparable mass, and the cluster and fieldvsini distributions differ with a high degree of significance. Forsomewhat more evolved stars with masses in the range 5-9Msolar, the mean vsini in h and χ Per is 1.5 times thatof the field; the vsini distributions differ as well, but with a lowerdegree of statistical significance. For stars that have evolvedsignificantly from the ZAMS and are approaching the hydrogen exhaustionphase (those with masses in the range 9-15 Msolar), thecluster and field star means and distributions are only slightlydifferent. We argue that both the higher rotation rates and the patternof rotation speeds as a function of mass that differentiatemain-sequence B stars in h and χ Per from their field analogs werelikely imprinted during the star formation process rather than a resultof angular momentum evolution over the 12-15 Myr cluster lifetime. Wespeculate that these differences may reflect the effects of the higheraccretion rates that theory suggests are characteristic of regions thatgive birth to dense clusters, namely, (1) higher initial rotationspeeds; (2) higher initial radii along the stellar birth line, resultingin greater spin-up between the birth line and the ZAMS; and (3) a morepronounced maximum in the birth line radius-mass relationship thatresults in differentially greater spin-up for stars that become mid- tolate-B stars on the ZAMS.
| Highly ionized gas in the local ISM: Some like it hot?
We present HST-STIS medium-resolution spectra (R 6.5 kms-1) of the ultraviolet interstellar absorption linesobserved towards 4 early-type stars located within the localinterstellar medium (ISM), with sight-line distances <186 pc in thegeneral direction of the Loop I superbubble (l = 330°, b =+18°). These data have been supplemented with high resolution (R 3 km s-1) visible absorption observations of the NaID-lines towards these 4 stars. Our main discovery is the detection ofhighly ionized absorption components of CIV, SiIV and NV towards the twomost distant targets, HD 127381 and HD 142256. These lines-of-sight areknown to cross both the near and far neutral interface boundaries to theLoop I cavity, in addition to intersecting the fragmented shell ofneutral and partially ionized gas that defines the boundary to the LocalBubble. However, the presently measured narrow line profile-widths andtheir measured absorption intensities are found to be incompatible withtheoretical models that predict high ion absorption due to the presenceof evaporating cloud conduction interfaces. We conclude that theformation of high ions in the local ISM is highly dependent on thelocation of the absorbing gas clouds with respect to nearby sources ofboth hot X-ray emitting gas and/or photo-ionization. Our observationshave also revealed at least 6 gas clouds with distances ranging from 5pc to 150 pc along these sight-lines. We have detected a cloud ofneutral and partially ionized gas with a velocity of -15 kms-1 and a hydrogen column density of log N(HI +HII) 19.3 cm-2 that is thought to define the boundary to the LocalBubble cavity at a distance of ~90 pc in this galactic direction. Thefar neutral boundary to the Loop I superbubble cavity is also detectedat a distance of 150-180 pc and is composed of two cold clouds moving atvelocities close to Vhelio 0 km s-1possessing a combined hydrogen column density of log N(HI + HII)≫19.5 cm-2. In contrast, we have also detected three lowdensity, warm and partially ionized diffuse clouds with averagevelocities of ~-10, -23 and -32 km s-1, that are all locatedwithin a distance of ~150 pc. The cloud component at V -23 kms-1 may be associated with the very local "G-cloud" at adistance of <5 pc, but we also provide evidence for its placement ata greater distance. The measured velocities of the majority of the gasclouds we have detected along all 4 sight-lines are consistent with aninflow of gas into the LB cavity from the direction of the Loop Isuperbubble. This gas is flowing through a region of fragmentation at adistance of ~90 pc that represents the interaction region between theLoop I and Local Bubble cavities.
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Surface abundances of light elements for a large sample of early B-type stars - III. An analysis of helium lines in spectra of 102 stars
Non-local thermodynamic equilibrium analysis of He I lines in spectraof 102 B stars is implemented in order to derive the helium abundanceHe/H, the microturbulent parameter Vt and the projectedrotation velocity v sini. A simultaneous determination of He/H andVt for the stars is effected by analysing equivalent widthsof the 4471- and 4922-Å lines primarily as indicators of He/H andthe 4713-, 5016-, 5876- and 6678-Å lines primarily as indicatorsof Vt. The rotation velocities v sini are found from profilesof the same lines. It is shown that, when Vt > 7 kms-1, the Vt(He I) values determined from He Ilines are systematically overestimated as compared with theVt(OII, NII) values derived from OII and NII lines. Thisdiscrepancy is especially appreciable for hot evolved B giants withVt(He I) = 16-23 km s-1 and may indicate a failureof classical model atmospheres to represent the strong He I lines forthese stars.Two programme stars, HR 1512 and 7651, are found to be helium-weakstars. The remaining 100 stars are divided into three groups accordingto their masses M. The microturbulent parameter Vt(He I) islow for all stars of group A (M= 4.1-6.9 Msolar) and for allstars with the relative ages t/tMS < 0.8 of group B (M=7.0-11.2 Msolar). Their Vt(He I) values are withinthe 0 to 5 km s-1 range, as a rule; the mean value isVt= 1.7 km s-1. Only evolved giants of group B,which are close to the termination of the main-sequence (MS)evolutionary phase (t/tMS > 0.8), show Vt(He I)up to 11 km s-1. The helium abundance He/H is correlated withthe relative age t/tMS in both groups; the averaged He/Henhancement during the MS phase is 26 per cent. For group C, containingthe most massive stars (M= 12.4-18.8 Msolar), theVt(He I) values display a correlation with t/tMS,varying from 4 to 23 km s-1. The He/H determination for hotevolved B giants of the group with Vt(He I) > 15 kms-1 depends on a choice between the Vt(He I) andVt(OII, NII) scales. The mean He/H enrichment by 67 per centduring the MS phase is found, if the abundances He/H are based on theVt(OII, NII) scale; however, two evolved giants withespecially high v sini, HR 7446 and 7993, show the He/H enhancement byabout a factor of 2.5. When using the same Vt scale, we founda trend of He/H with projected rotational velocities v sini a largedispersion for v sini > 150 km s-1 can result fromdifferences in masses M.A comparison with the stellar model computations with rotationallyinduced mixing shows that the observed helium enrichment during the MSphase can be explained by rotation with initial velocities 250-400 kms-1. The He/H distribution on M and v sini based on theVt(OII, NII) scale seems to be in better agreement with thetheory than one based on the Vt(He I) scale. The mean valueHe/H = 0.10 derived for stars in the zero age main sequence (ZAMS)vicinity can be adopted as the typical initial helium abundance forearly B stars in the solar neighbourhood.
| Atomic Deuterium/Hydrogen in the Galaxy
An accurate value of the D/H ratio in the local interstellar medium(LISM) and a better understanding of the D/H variations with position inthe Galactic disk and halo are vitally important questions as theyprovide information on the primordial D/H ratio in the Galaxy at thetime of the protosolar nebula, and the amount of astration and mixing inthe Galaxy over time. Recent measurements have been obtained with UVspectrographs on FUSE, HST, and IMAPS using hot white dwarfs, OB stars,and late-type stars as background light sources against which to measureabsorption by D and H in the interstellar medium along the lines ofsight. Recent analyses of FUSE observations of seven white dwarfs andsubdwarfs provide a weighted mean value of D/H = (1.52±0.08)× 10‑5 (15.2 ± 0.8 ppm), consistent withthe value of (1.50 ± 0.10) × 10‑5 (15.0± 1.0 ppm) obtained from analysis of lines of sight toward nearbylate-type stars. Both numbers refer to the ISM within about 100 pc ofthe Sun, which samples warm clouds located within the Local Bubble.Outside of the Local Bubble at distances of 200 to 500 pc, analyses offar-UV spectra obtained with the IMAPS instrument indicate a much widerrange of D/H ratios between 0.8 to 2.2 ppm. This portion of the Galacticdisk provides information on inhomogeneous astration in the Galaxy.
| Far Ultraviolet Spectroscopic Explorer Survey of the Local Interstellar Medium within 200 Parsecs
We present Far Ultraviolet Spectroscopic Explorer observations of theinterstellar gas toward 30 white dwarf stars and one subdwarf (SdO)star. These sight lines probe the Local Bubble (LB) and the localinterstellar medium (LISM) near the LB. We systematically measure thecolumn densities for the following species: C II, C II*, C III, N I, NII, O I, Ar I, Si II, P II, Fe II, Fe III, and H2. Our surveydetected only diffuse H2 molecular clouds(fH2<~10-4) along six sight lines.There is no evidence from this study that H2 exists wellinside the perimeter of the LB. The kinematical temperature forH2 is less than the usual temperature observed in the localinterstellar clouds, implying different gas phases in the LISM. Therelative abundance ratios of Si II, P II, and Fe II give insight aboutthe dust content. These ratios vary but are similar to the depletionpatterns observed in warm and halo diffuse clouds in more distant sightlines in the Galaxy. The N I/O I and Ar I/O I ratios are significantlysubsolar within the LB. Outside the LB a larger scatter is observed fromsubsolar to solar. Because Ar and N are only weakly depleted into dustgrains if at all, the deficiencies of their neutral forms are likely dueto photoionization. The evidence for significant ionization of N (andhence Ar) is strengthened by the detection and measurement of N II,which is a dominant ion for this element toward many sight lines. C IIIappears to be ubiquitous in the LISM toward our sight lines, but C IIremains the dominant ionization stage of C. The limits on Fe III/Fe IIimply that Fe II is the dominant ion. These observations imply thatphotoionization is the main ionization mechanism in the LISM and do notsupport the existence of a highly ionized condition in the past. In viewof the variations observed in the different atomic and ionic ratios, thephotoionization conditions vary significantly in the LB and the LISM.The cooling rate in the LISM, lc [in ergs s-1 (H Iatom)-1], derived from the emission of the C II 157.7 μmline has a mean value of loglc=-25.59+/-0.32 dex, verysimilar to previous determinations.
| X-Ray Modeling of Very Young Early-Type Stars in the Orion Trapezium: Signatures of Magnetically Confined Plasmas and Evolutionary Implications
The Orion Trapezium is one of the youngest and closest star-formingregions within our Galaxy. With a dynamic age of ~3×105yr, it harbors a number of very young hot stars, which likely are on thezero-age main sequence (ZAMS). We analyzed high-resolution X-ray spectrain the wavelength range of 1.5-25 Å of three of itsX-ray-brightest members (Θ1 Ori A, C, and E) obtainedwith the High Energy Transmission Grating Spectrometer (HETGS) on boardthe Chandra X-Ray Observatory. We measured X-ray emission lines,calculated differential emission measure distributions (DEMs), andfitted broadband models to the spectra. The spectra from all three starsare very rich in emission lines, specifically from highly ionized Fe,which includes emission from Fe XVII to Fe XXV ions. A complete linelist is included. This is a mere effect of high temperatures rather thanan overabundance of Fe, which in fact turns out to be underabundant inall three Trapezium members. Similarly there is a significantunderabundance in Ne and O as well, whereas Mg, Si, S, Ar, and Ca appearclose to solar. The DEM derived from over 80 emission lines in thespectrum of Θ1 Ori C indicates three peaks located at7.9, 25, and 66 MK. The emission measure varies over the 15.4 day windperiod of the star. For the two phases observed, the low-temperatureemission remains stable, while the high-temperature emission showssignificant differences. The line widths seem to show a similarbifurcation, where we resolve some of the soft X-ray lines withvelocities up to 850 km s-1 (all widths are stated ashalf-width at half-maximum), whereas the bulk of the lines remainunresolved with a confidence limit of 110 km s-1. Thebroadband spectra of the other two stars can be fitted with severalcollisionally ionized plasma model components within a temperature rangeof 4.3-46.8 MK for Θ1 Ori E and 4.8-42.7 MK forΘ1 Ori A. The high-temperature emissivity contributesover 70% to the total X-ray flux. None of the lines are resolved forΘ1 Ori A and E with a confidence limit of 160 kms-1. The influence of the strong UV radiation field on theforbidden line in the He-like triplets allows us to set an upper limiton distance of the line-emitting region from the photosphere. The bulkof the X-ray emission cannot be produced by shock instabilities in aradiation-driven wind and are likely the result of magnetic confinementin all three stars. Although confinement models cannot explain all theresults, the resemblance of the unresolved lines and of the DEM withrecent observations of active coronae in II Peg and AR Lac during flaresis quite obvious. Thus we speculate that the X-ray production mechanismin these stars is similar, with the difference that the Orion stars maybe in a state of almost continuous flaring driven by the wind. Weclearly rule out major effects due to X-rays from a possible companion.The fact that all three stars appear to be magnetic and are near zeroage on the main sequence also raises the issue of whether the Orionstars are simply different or whether young massive stars enter the mainsequence carrying significant magnetic fields. The ratiologLX/Lbol using the ``wind'' component of thespectrum is -7 for the Trapezium stars, consistent with the expectationfrom O stars. This suggests that massive ZAMS stars generate their X-rayluminosities like normal O stars and magnetic confinement provides anadditional source of X-rays.
| The Chemical Composition and Gas-to-Dust Mass Ratio of Nearby Interstellar Matter
We use recent results on interstellar gas toward nearby stars andinterstellar by-products within the solar system to select among theequilibrium radiative transfer models of the nearest interstellarmaterial presented in Slavin & Frisch. For the assumption thatO/H~400 parts per million, models 2 and 8 are found to yield good fitsto available data on interstellar material inside and outside of theheliosphere, with the exception of the Ne abundance in the pickup ionand anomalous cosmic-ray populations. For these models, the interstellarmedium (ISM) at the entry point to the heliosphere hasn(H0)=0.202-0.208 cm-3,n(He0)=0.0137-0.0152 cm-3, and ionizationsχ(H)=0.29-0.30, χ(He)=0.47-0.51. These best models suggest thatthe chemical composition of the nearby ISM is ~60%-70% subsolar if S isundepleted. Both H0 and H+ need to be includedwhen evaluating abundances of ions found in warm diffuse clouds. Models2 and 8 yield an H filtration factor of ~0.46. Gas-to-dust mass ratiosfor the ISM toward ɛ CMa are Rgd=178-183 for solarabundances of Holweger or Rgd=611-657 for an interstellarabundance standard 70% solar. Direct observations of dust grains in thesolar system by Ulysses and Galileo yield Rgd~=115 for models2 and 8, supporting earlier results (Frisch and coworkers). If the localISM abundances are subsolar, then gas and dust are decoupled over smallspatial scales. The inferred variation in Rgd over parseclength scales is consistent with the fact that the ISM near the Sun ispart of a dynamically active cluster of cloudlets flowing away from theSco-Cen association. Observations toward stars within ~500 pc show thatRgd correlates with the percentage of the dust mass that iscarried by iron, suggesting that an Fe-rich grain core (by mass) remainsafter grain destruction. Evidently large dust grains (>10-13g) and small dust grains (<10-13 g) are not well mixedover parsec length spatial scales in the ISM. It also appears that verysmall C-dominated dust grains have been destroyed in the ISM withinseveral parsecs of the Sun, since C appears to be essentiallyundepleted. However, if gas-dust coupling breaks down over the cloudlifetime, the missing mass arguments applied here to determineRgd and dust grain mineralogy are not appropriate.
| Surprisingly Little O VI Emission Arises in the Local Bubble
This paper reports the first study of the O VI resonance line emission(λλ1032, 1038) originating in the Local Bubble (or LocalHot Bubble) surrounding the solar neighborhood. In spite of the factthat O VI absorption within the Local Bubble has been observed, noresonance line emission was detected during our 230 ks Far UltravioletSpectroscopic Explorer observation of a ``shadowing'' filament in thesouthern Galactic hemisphere. As a result, tight 2 σ upper limitsare set on the intensities in the 1032 and 1038 Å emission lines:500 and 530 photons cm-2 s-1 sr-1,respectively. These values place strict constraints on models andsimulations. They suggest that the O VI-bearing plasma and the X-rayemissive plasma reside in distinct regions of the Local Bubble and arenot mixed in a single plasma, whether in equilibrium withT~106 K or highly overionized with T~4 to6×106 K. If the line of sight intersects multiple coolclouds within the Local Bubble, then the results also suggest thathot/cool transition zones differ from those in current simulations. Withthese intensity upper limits, we establish limits on the electrondensity, thermal pressure, path length, and cooling timescale of the OVI-bearing plasma in the Local Bubble. Furthermore, the intensity of OVI resonance line doublet photons originating in the Galactic thick diskand halo is determined (3500-4300 photons cm-2 s-1sr-1), and the electron density, thermal pressure, pathlength, and cooling timescale of its O VI-bearing plasma are calculated.The pressure in the Galactic halo's O VI-bearing plasma (3100-3800 Kcm-3) agrees with model predictions for the total pressure inthe thick disk/lower halo. We also report the results of searches forthe emission signatures of interstellar C I, C II, C III, N I, N II, NIII, Mg II, Si II, S II, S III, S IV, S VI, Fe II, and Fe III.
| Elemental Abundances and Mass Densities of Dust and Gas in the Local Interstellar Cloud
Observationally derived gas-phase abundances and appropriate assumptionsfor the total elemental abundances of dust and gas determine theelemental composition of dust and the elemental depletion from gas inthe interstellar medium (ISM). In addition to the elemental abundances,the total mass ratio of hydrogen atoms to dust grains per spatial volumeis a measure of the interaction between dust and gas in the ISM. Recentremote astronomical observations and in situ measurements provide theopportunity of estimating the elemental abundances and the hydrogengas-to-dust mass ratio of the Local Interstellar Cloud (LIC), in whichthe Sun is currently embedded. We show that the composition of dust inthe LIC is similar to that of cometary dust in the solar system,although the nitrogen abundance remains uncertain. Depletions ofelements from the LIC gas are consistent with measurements of warmneutral clouds in the Galactic disk, except for Mg and Si, which areheavily depleted in the LIC. Remote astronomical observations and insitu measurements give essentially the same value for the gas-to-dustmass ratio of the LIC, which is comparable to the average value of thediffuse ISM in the Galaxy. This indicates the association of dust withgas in the LIC, which is also inferred from the depletion pattern in theLIC. Neither the depletions of elements nor the gas-to-dust mass ratioshow evidence for severe grain destruction that would result from shockswith velocity ~1.5×107 cm s-1 as suggestedby a model that postulates the LIC to be a fragment of the expandingLoop I superbubble shell. Our results rather favor an alternative modelthat describes the origin of the LIC as being one of H I cloudletsexpelled from the interaction zone between the Loop I superbubble andthe Local Bubble, which encloses the LIC and similar clouds in the solarneighborhood.
| 3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
| Quantitative Stellar Spectral Classification. II. Early Type Stars
The method developed by Stock & Stock (1999) for stars of spectraltypes A to K to derive absolute magnitudes and intrinsic colors from theequivalent widths of absorption lines in stellar spectra is extended toB-type stars. Spectra of this type of stars for which the Hipparcoscatalogue gives parallaxes with an error of less than 20% were observedwith the CIDA one-meter reflector equipped with a Richardsonspectrograph with a Thompson 576×384 CCD detector. The dispersionis 1.753 Å/pixel using a 600 lines/mm grating in the first order.In order to cover the spectral range 3850 Å to 5750 Å thegrating had to be used in two different positions, with an overlap inthe region from 4800 Å to 4900 Å . A total of 116 stars wasobserved, but not all with both grating positions. A total of 12measurable absorption lines were identified in the spectra and theirequivalent widths were measured. These were related to the absolutemagnitudes derived from the Hipparcos catalogue and to the intrinsiccolors (deduced from the MK spectral types) using linear and secondorder polynomials and two or three lines as independent variables. Thebest solutions were obtained with polynomials of three lines,reproducing the absolute magnitudes with an average residual of about0.40 magnitudes and the intrinsic colors with an average residual of0.016 magnitudes.
| Study of the X-Ray Background Spectrum and Its Large-Scale Fluctuation with ASCA
We studied the energy spectrum and the large-scale fluctuation of theX-ray background with the ASCA GIS instrument based on the ASCA MediumSensitivity Survey and Large Sky Survey observations. A total of 91fields with Galactic latitude |b| > 10° were selected with a skycoverage of 50 deg2 and 4.2 Ms of exposure. For each field,non-X-ray events were carefully subtracted and sources brighter than ~ 2× 1013 erg cm-2 s-1 (2-10keV)were eliminated. Spectral fits with a single power-law model for theindividual 0.7-10 keV spectra showed a significant excess below ~ 2keV,which could be expressed by an additional thermal model with kT ~= 0.4keV or a steep power-law model with a photon index ofΓsoft ~= 6. The 0.5-2keV intensities of the softthermal component varied significantly from field to field by 1 σ= 52 +4-5%, and showed a maximum toward theGalactic Center. This component is considered to be entirely Galactic.As for the hard power-law component, an average photon index of 91fields was obtained to be Γhard = 1.412 +/- 0.007 +/-0.025 and the average 2-10keV intensity was calculated asFhardX = (6.38 +/- 0.04 +/- 0.64) ×10-8erg cm-2 s-1 sr-1 (1σ statistical and systematic errors). The Galactic component ismarginally detected in the hard band. The 2-10keV intensities show a 1σ deviation of 6.49+0.56-0.61%, whiledeviation due to the reproducibility of the particle background is 3.2%.The observed deviation can be explained by the Poisson noise of thesource count in the f.o.v. (~ 0.5 deg2), even assuming asingle N-logS relation on the whole s ky. Based on the observedfluctuation and the absolute intensity, an acceptable region of theN-logS relation was derived, showing a consistent feature with therecent Chandra and XMM-Newton results. The fluctuation of the spectralindex was also examined; it implied a large amount of hard sources and asubstantial variation in the intrinsic source spectra(Γs ~= 1.1 +/- 1.0).
| Surface abundances of light elements for a large sample of early B-type stars - II. Basic parameters of 107 stars
Effective temperatures Teff, surface gravities logg andinterstellar extinctions AV are found for 107 B stars.Distances d of the stars, which are based on the derivedTeff, logg and AV values, show good agreement withthose obtained from the Hipparcos parallaxes. Comparing theTeff and logg values with evolutionary computations, we infermasses, radii, luminosities, ages and relative ages of the stars.Empirical relations between the Teff and logg parameters, onthe one hand, and the photometric indices Q, [c1] and β,on the other hand, are constructed; these relations give a fast methodfor the Teff and logg estimation of early and medium B stars.Inclusion of the infrared J, H and K colours into the Teff,logg and AV determination shows that (i) the Teffand logg parameters are altered only slightly; (ii) the AVvalue is rather sensitive to these colours, so an accuracy better than0.05mag in the JHK data is necessary for precise AVevaluation.
| Elemental Abundances and Ionization States within the Local Interstellar Cloud Derived from Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer Observations of the Capella Line of Sight
We use ultraviolet spectra of Capella from the Hubble Space Telescopeand Far Ultraviolet Spectroscopic Explorer satellites to studyinterstellar absorption lines from the Local Interstellar Cloud (LIC).Measurements of these lines are used to empirically determine theionization states of carbon, nitrogen, and silicon in the LIC, forcomparison with the predictions of theoretical photoionization models.We find that the observed ionization states are consistent withpreviously published photoionization predictions. Total abundances aredetermined for the elements mentioned above, and others, for comparisonwith solar abundances. Magnesium, aluminum, silicon, and iron are alldepleted by at least a factor of 10 toward Capella. The abundances ofcarbon, nitrogen, and oxygen are essentially solar, although the errorbars are large enough to also allow depletions of about a factor of 2for these elements. Based on observations made with the NASA-CNES-CSAFar Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by theJohns Hopkins University under NASA contract NAS5-32985. Also based onobservations with the NASA/ESA Hubble Space Telescope, obtained from theData Archive at the Space Telescope Science Institute, which is operatedby the Association of Universities for Research in Astronomy, Inc.,under NASA contract NAS5-26555.
| The Heavy-Element Enrichment of Lyα Clouds in the Virgo Supercluster
Using high signal-to-noise ratio echelle spectra of 3C 273 obtained withthe Space Telescope Imaging Spectrograph (resolution of 7 kms-1 FWHM), we constrain the metallicities of two Lyαclouds in the vicinity of the Virgo Cluster. We detect C II, Si II, andSi III absorption lines in the Lyα absorber atzabs=0.00530. Previous observations with the Far UltravioletSpectroscopic Explorer have revealed Lyβ-Lyθ absorptionlines at the same redshift, thereby accurately constraining the H Icolumn density. We model the ionization of the gas and derive[C/H]=-1.2+0.3-0.2, [Si/C]=0.2+/-0.1, andlognH=-2.8+/-0.3. The model implies a small absorberthickness, ~70 pc, and thermal pressure p/k~40 cm-3 K. It ismost likely that the absorber is pressure confined by an external mediumbecause gravitational confinement would require a very high ratio ofdark matter to baryonic matter. Based on a sample of Milky Way sightlines in which carbon and silicon abundances have been reliably measuredin the same interstellar cloud (including new measurements presentedherein), we argue that it is unlikely that the overabundance of Sirelative to C is due to depletion onto dust grains. Instead, thisprobably indicates that the gas has been predominately enriched byejecta from Type II supernovae. Such enrichment is most plausiblyprovided by an unbound galactic wind, given the absence of knowngalaxies within a projected distance of 100 kpc and the presence ofgalaxies capable of driving a wind at larger distances (e.g., H I1225+01). Such processes have been invoked to explain the observedabundances in the hot, X-ray-emitting gas in Virgo. However, the sightline to 3C 273 is more than 10° away from the X-ray emission region.We also constrain the metallicity and physical conditions of the Virgoabsorber at zabs=0.00337 in the spectrum of 3C 273 based ondetections of O VI and H I and an upper limit on C IV. If this absorberis collisionally ionized, the OVI/CIV limit requiresT>~105.3 K in the O VI-bearing gas. For either collisionalionization or photoionization, we find that [O/H]>~-2.0 atzabs=0.00337. Based on observations with the NASA/ESA HubbleSpace Telescope, obtained at the Space Telescope Science Institute,which is operated by the Association of Universities for Research inAstronomy, Inc., under NASA contract NAS 5-26555.
| The Velocity Distribution of the Nearest Interstellar Gas
The bulk flow velocity for the cluster of interstellar cloudlets within~30 pc of the Sun is determined from optical and ultraviolet absorptionline data, after omitting from the sample stars with circumstellar disksor variable emission lines and the active variable HR 1099. A total of96 velocity components toward the remaining 60 stars yield a streamingvelocity through the local standard of rest of -17.0+/-4.6 kms-1, with an upstream direction of l=2.3d, b=-5.2d (usingHipparcos values for the solar apex motion). The velocity dispersion ofthe interstellar matter (ISM) within 30 pc is consistent with that ofnearby diffuse clouds, but present statistics are inadequate todistinguish between a Gaussian or exponential distribution about thebulk flow velocity. The upstream direction of the bulk flow vectorsuggests an origin associated with the Loop I supernova remnant.Groupings of component velocities by region are seen, indicatingregional departures from the bulk flow velocity or possibly separateclouds. The absorption components from the cloudlet feeding ISM into thesolar system form one of the regional features. The nominal gradientbetween the velocities of upstream and downstream gas may be an artifactof the Sun's location near the edge of the local cloud complex. The Sunmay emerge from the surrounding gas patch within several thousand years.
| Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| Boron Abundances in B-Type Stars: A Test of Rotational Depletion during Main-Sequence Evolution
Boron abundances have been derived for seven main-sequence B-type starsfrom Hubble Space Telescope STIS spectra around the B III λ2066line. In two stars, boron appears to be undepleted with respect to thepresumed initial abundance. In one star, boron is detectable but isclearly depleted. In the other four stars, boron is undetectable,implying depletions of 1-2 dex. Three of these four stars are nitrogenenriched, but the fourth shows no enrichment of nitrogen. Onlyrotationally induced mixing predicts that boron depletions areunaccompanied by nitrogen enrichments. The inferred rate of borondepletion from our observations is in good agreement with thesepredictions. Other boron-depleted nitrogen-normal stars are identifiedfrom the literature. In addition, several boron-depleted nitrogen-richstars are identified, and while all fall on the boron-nitrogen trendpredicted by rotationally induced mixing, a majority have nitrogenenrichments that are not uniquely explained by rotation. The spectrahave also been used to determine iron group (Cr, Mn, Fe, and Ni)abundances. The seven B-type stars have near-solar iron groupabundances, as expected for young stars in the solar neighborhood. Wehave also analyzed the halo B-type star PG 0832+676. We find[Fe/H]=-0.88+/-0.10, and the absence of the B III line gives the upperlimit [B/H]<-2.5. These and other published abundances are used toinfer the star's evolutionary status as a post-asymptotic giant branchstar. Based on observations made with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS 5-26555. These observations are associatedwith proposal GO 07400.
| The Ionization of Nearby Interstellar Gas
We present new calculations of the photoionization of interstellarmatter within ~5 pc of the Sun (which we refer to as the ``complex oflocal interstellar clouds,'' or CLIC) by directly observed radiationsources, including nearby hot stars and the diffuse emission of the softX-ray background (SXRB). In addition, we model the important, unobservedextreme-ultraviolet (EUV) emission both from the hot gas responsible forthe SXRB and from a possible evaporative boundary between the CLIC andthe hot gas. We carry out radiative transfer calculations and show thatthese radiation sources can provide the ionization and heating of thecloud required to match a variety of observations. The ionizationpredicted in our models shows good agreement with pickup ion results,interstellar absorption-line data toward ɛ CMa, and EUV opacitymeasurements of nearby white dwarf stars. Including the radiation fromthe conductive boundary improves agreement with data on the temperatureand electron density in the cloud. The presence of dust in the cloud, orat least depleted abundances, is necessary to maintain theheating/cooling balance and reach the observed temperature. Using thecolumn density observations as inputs, we derive the gas-phaseabundances of C, N, O, Mg, Si, S, and Fe. Based on these inferreddepletions, it appears that silicate and iron dust exists in the CLIC,while carbonaceous dust has been destroyed. In addition, we findevidence that the Ne abundance in the CLIC is larger than solar.
| Far Ultraviolet Spectroscopic Explorer (FUSE) observations of emitting and absorbing gas in the Local Interstellar Chimney
We present Far Ultraviolet Spectroscopic Explorer (FUSE) satellitemeasurements of the absorption and emission characteristics ofinterstellar gas associated with the Local Interstellar Chimney, whichis an extension of the rarefied Local Bubble cavity that extends outwardfrom the galactic disk towards the lower galactic halo. Far ultraviolet(FUV) diffuse background emission has been detected in the highionization line of O VI (lambda 1032 Å) for two lines-of-sight (l= 162.7deg, b = +57.0deg) and (l =156.3deg, b = +57.8deg) at emission levels of2500+/-700 photons cm-2 s-1 sr-1 (LU)and 3300+/-1100 LU respectively. These levels of O VI emission are verysimilar to those found for four other lines-of-sight sampled thus far bythe FUSE satellite, implying a fairly constant level of average O VIsurface brightness emission at high galactic latitudes of about 2700 LUwith a standard deviation of 450 LU. These emission-line data aresupplemented by FUV interstellar absorption line measurements takentowards the hot DA white dwarf star, REJ 1032+532 (l =157.5deg, b = +53.2deg), whose distance of 116 pcplaces it within the Local Bubble region. No high ionizationinterstellar O VI lambda 1032 Å absorption has been detected (N(OVI) < 13.0 cm-2), which is consistent with thenon-detections of interstellar C IV and Si IV absorption reportedtowards this star by Holberg et al. (\cite{holberg99a}). Taken together,our FUV absorption and emission data may be explained by a scenario inwhich the O VI emission and absorption lines are both formed at theconductive interface of the neutral boundary to the Local Bubble. Forthe presently sampled sight-lines we have found no correlation betweenthe OVI emission line intensity and the associated 0.25 keV soft X-raybackground flux as measured in the R1 and R2 bands by the ROSATsatellite. The OVI line intensities also show no correlation with thesoft X-ray background flux attributable to emission from the milliondegree K gas of the Local Hot Bubble as modeled by Kuntz & Snowden(\cite{kuntz00}). Any (new) model of the Local Bubble must now be ableto explain (i) the low levels of variability in both the O VIemission-line intensity and the associated soft X-ray background fluxfor galactic sight-lines >|40|o, (ii) the observedpressure of P/k ~ 10 000 cm-3 K for the local hotinterstellar gas, and (iii) the paucity of high ionization absorptionlines observed within the local ISM and the sudden increase in theirmeasured column density for distances beyond the Local Bubble neutralboundary.
| The ISO-SWS post-helium atlas of near-infrared stellar spectra
We present an atlas of near-infrared spectra (2.36 mu m-4.1 mu m) of ~300 stars at moderate resolution (lambda /delta lambda ~ 1500-2000). Thespectra were recorded using the Short-Wavelength Spectrometer aboard theInfrared Space Observatory (ISO-SWS). The bulk of the observations wereperformed during a dedicated observation campaign after the liquidhelium depletion of the ISO satellite, the so-called post-heliumprogramme. This programme was aimed at extending the MK-classificationto the near-infrared. Therefore the programme covers a large range ofspectral types and luminosity classes. The 2.36 mu m-4.05 mu m region isa valuable spectral probe for both hot and cool stars. H I lines(Bracket, Pfund and Humphreys series), He I and He II lines, atomiclines and molecular lines (CO, H2O, NH, OH, SiO, HCN,C2H2, ...) are sensitive to temperature, gravityand/or the nature of the outer layers of the stellar atmosphere(outflows, hot circumstellar discs, etc.). Another objective of theprogramme was to construct a homogeneous dataset of near-infraredstellar spectra that can be used for population synthesis studies ofgalaxies. At near-infrared wavelengths these objects emit the integratedlight of all stars in the system. In this paper we present the datasetof post-helium spectra completed with observations obtained during thenominal operations of the ISO-SWS. We discuss the calibration of the SWSdata obtained after the liquid helium boil-off and the data reduction.We also give a first qualitative overview of how the spectral featuresin this wavelength range change with spectral type. The dataset isscrutinised in two papers on the quantitative classification ofnear-infrared spectra of early-type stars ({Lenorzer} et al.\cite{lenorzer:2002a}) and late-type stars (Vandenbussche et al., inprep). Based on observations with ISO, an ESA project with instrumentsfunded by ESA Members States (especially the PI countries France,Germany, the Netherlands and the United Kingdom) and with theparticipation of ISAS and NASA. The full atlas is available inelectronic form at www.edpsciences.org Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/390/1033
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| An atlas of 2.4 to 4.1 mu m ISO/SWS spectra of early-type stars
We present an atlas of spectra of O- and B-type stars, obtained with theShort Wavelength Spectrometer (SWS) during the Post-Helium program ofthe Infrared Space Observatory (ISO). This program is aimed at extendingthe Morgan & Keenan classification scheme into the near-infrared.Later type stars will be discussed in a separate publication. Theobservations consist of 57 SWS Post-Helium spectra from 2.4 to 4.1 μm, supplemented with 10 spectra acquired during the nominal mission witha similar observational setting. For B-type stars, this sample providesample spectral coverage in terms of subtype and luminosity class. ForO-type stars, the ISO sample is coarse and therefore is complementedwith 8 UKIRT Larcmin -band observations. In terms of the presence ofdiagnostic lines, the Larcmin -band is likely the most promising of thenear-infrared atmospheric windows for the study of the physicalproperties of B stars. Specifically, this wavelength interval containsthe Bralpha , Pfgamma , and other Pfund lines which are probes ofspectral type, luminosity class and mass loss. Here, we present simpleempirical methods based on the lines present in the 2.4 to 4.1 mu minterval that allow the determination of i) the spectral type of Bdwarfs and giants to within two subtypes; ii) the luminosity class of Bstars to within two classes; iii) the mass-loss rate of O stars and Bsupergiants to within 0.25 dex. Based on observations with ISO, an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, The Netherlands and the UK) and with theparticipation of ISAS and NASA. The appendix is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin.qcat?J/A+A/384/473
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