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The Quintuplet cluster

I. A K-band spectral catalog of stellar sources^,,

A. Liermann - W.-R. Hamann - L. M. Oskinova

University of Potsdam, Institute for Physics and Astronomy, 14476 Potsdam, Germany

Received 11 June 2008 / Accepted 10 September 2008

Abstract
Context. Three very massive clusters are known to reside in the Galactic center region, the Arches cluster, the Quintuplet cluster, and the central parsec cluster, each of them rich in young hot stars. With new infrared instruments, this region is no longer obscured for the observer.
Aims. For understanding these very massive clusters, it is essential to know their stellar inventory. We provide comprehensive spectroscopic data for the stellar population of the Quintuplet cluster that will form the basis of subsequent spectral analyses.
Methods. Spectroscopic observations of the Quintuplet cluster were obtained with the Integral Field Spectrograph SINFONI-SPIFFI at the ESO-VLT. The inner part of the Quintuplet cluster was covered by 22 slightly overlapping fields, each of them of in size. The spectral range comprises the near-IR K-band from 1.94 to 2.45 m. The 3D data cubes of the individual fields were flux-calibrated and combined to one contiguous cube, from which the spectra of all detectable point sources were extracted.
Results. We present a catalog of black160 stellar sources in the inner part of the Quintuplet cluster. The flux-calibrated K-band spectra of 98 early-type stars and 62 late-type stars are provided as Online Material. Based on these spectra, we assign spectral types to all detected sources and derive synthetic -band magnitudes. Our sample is complete to about the 13th K-magnitude. We report the detection of two hitherto unknown Wolf-Rayet stars of late WC type (WC9 or later). Radial velocities are measured and employed to assess the cluster membership. The quantitative analysis of the early-type spectra will be the subject of a subsequent paper.

Key words: catalogs - Galaxy: center - Galaxy: open cluster and associations: individual: quintuplet - infrared: stars - stars: late-type - stars: early-type

1 Introduction

The Galactic center has long been hidden from optical observation due to high extinction in the visual. blackToday the advanced instruments for infrared radiation give access to this region. Three surprisingly young and massive stellar clusters were found within blacka projected distance of 35 pc from the central black hole: the Arches, the Quintuplet, and the central cluster. These clusters are found to be rich in massive stars (Arches: Blum et al. 2001, Figer 2004, Martins et al. 2008; Quintuplet: Figer et al. 1999a,1997, Figer 2004; Galactic center cluster: Eckart et al. 2004; Figer 2004). The prominent constellation of five infrared-bright stars gave the reason to name one of the blackclusters the ``Quintuplet cluster'' (Okuda et al. 1989,1987). It has a projected distance of 30 pc to the Galactic center, a cluster radius of about 1 pc, and an estimated age of about 4 million years (Okuda et al. 1990; Figer et al. 1999a).

First spectroscopic observations of the five ``Quintuplet proper'' stars black(later named Q1, Q2, Q3, Q4, and Q9 by Figer et al. 1999a) showed only a continuum without any features. Some of them have also been detected as far-IR and radio sources (Lang et al. 2005,1999,1997). Tuthill et al. (2006) resolved two of the original Quintuplet stars (Q2 and Q3) in space and time as colliding wind binaries, ejecting dust in the shape of a rotating ``pinwheel''. According to further spectroscopic studies (Figer et al. 1999a; Figer 2004), the cluster contains at least 100 O stars and 16 Wolf-Rayet stars. Two massive, evolved stars in their luminous blue variable black(LBV) phase, the ``Pistol star'' and blacka second LBV candidate, have been found in the Quintuplet cluster (Geballe et al. 2000). blackAt least two luminous stars of late spectral type K and M blackwere found in the cluster as well.

The present paper black(hereafter the ``LHO catalog'') provides a comprehensive spectral atlas of K-band spectra from stellar sources in the Quintuplet cluster. These spectra can form the basis of subsequent analysis of the luminous stellar population, which is blacka prerequisite for understanding the formation and evolution of this very massive cluster in its special galactic environment.

The paper is structured as follows. Section 2 gives details on the observations and data reduction. Section 3 contains the catalog with position, spectral classification, synthetic K mag, and radial velocity. The final Sect. 4 summarizes the catalog. The spectral atlas comprising 160 stars is shown in Table 2.

2 Observations

2.1 The data

We obtained service mode observations with the ESO VLT UT4 (Yepun) blacktelescope between May and July 2006 using the integral field spectrograph SPIFFI of the SINFONI module thatis equipped with a Rockwell Hawaii 2RD detector (Eisenhauer et al. 2003; Bonnet et al. 2004). The adaptive optics facility could not be used since no suitable guide star is available in this field and the laser guide star was not offered blackduring this period.

The observations consist of 22 observation blocks (OBs) covering the dense center of the Quintuplet cluster with slightly overlapping fields of view of (see Fig. 1). The ABBA cycles were performed with an exposure time of  mn on each science field. The grating for the K-band (1.95-2.45 m) provides a spectral resolution of . Table 1 gives an overview blackof the observations with their date and the center coordinates of the FoV. In the same mode, standard stars were observed at similar airmass for the flux calibration of the spectra.

2.2 Data reduction

The first steps of the data reduction were performed using the SPRED software (Abuter et al. 2006). Raw frames are corrected for bad pixels, distortion, and flatfield, followed by the wavelength calibration. The slitlets are stacked into a data cube, which then consists of layers of monochromatic images. This reduction process was applied to the science exposures as well as to the standard star observations.

Table 1:   List of observation blocks (OBs).

Sky subtraction was not performed at this stage of the data reduction, since the sky frames turned out to be contaminated by stellar sources that would create ``negative stars'' in the reduced data; blacktherefore, sky frames could not be applied. The sharp emission peaks in the extracted spectra, especially those of the fainter objects, are caused by blacktelluric OH contamination (see Fig. 2)black.

Further data reduction was performed with a self-written IDL cascade consisting of three parts. First, the standard star data cubes were sky-subtracted, using the monochromatic median of a pre-defined ``star free'' subarray of the field for each wavelength layer. Then, the standard star spectra were extracted by adding all pixels within a predefined extraction radius, mimicblackking a synthetic apeblackrture. blackEach standard star spectrum was identified with a Kurucz model (Kurucz 1993), selected according to the spectral type (between B and G) and scaled to the 2MASS -band magnitude (Skrutskie et al. 2006). blackThe calibration curve that will be applied later to the science observations, was obtained as the ratio between the model flux and the extracted standard-star spectrum. As the Kurucz models do not reproduce the Br line profile perfectly, the residual feature in blackthe calibration curve was smoothed out by interpolation between 2.15 and 2.17 m.

blackSky subtraction for the science observations was also performed with a monochromatic median of a pre-defined ``star-free'' subarray of each cube. Subsequently, each blackscience observation was flux-calibrated by blackmultiplying the cube wavelength plane with the corresponding value of the calibration curve. Then, all OBs were combined to one mosaic. The nominal telescope pointing turned out to be too imprecise for this purpose. Instead, we generated 2D images for each OB by ``collapsing'' the data cube to a passband image. These images were then used to determine the mutual spatial offsets between the fields by manually overlaying them on the HST composite image by Figer (HST program 7364, STScI-PRC1990-30b). Applying these offsets, all 22 blackOB cubes were combined into one grand mosaic cube, averaging the flux for pixels in overlapping regions.

The final part of the IDL cascade takes this grand mosaic cube blackand collapses it to a passband image. Then an automated search for detecting point sources was run on this 2D image. The radius to extract point sources was generally set to 4 pixels. A smaller synthetic aperture was chosen for stars that have close neighbors or are at the borders of the grand mosaic cube. In any case the applied calibration curve was based on standard star spectra extracted with the same aperture. Figure 3 shows the blackpassband image of the grand mosaic cube overlayed with the detected sources and their running number in this ``LHO'' catalog.

3 The catalog

3.1 Coordinates and identification

blackTo derive the coordinates, we superimpose the map of the detected sources (Fig. 3) on the HST image of the field (Fig. 1). The well-determined positions of foreground stars from the USNO-B catalog (Monet et al. 2003) are used to construct the mapping between the pixel positions and the celestial coordinates. An overlay image with coordinates is shown in Fig. 4.

Table 2 lists all black160 extracted sources. Column 1 gives the running number in this ``LHO'' catalog, followed by the coordinates in Cols. 2 and 3. The SIMBAD database was employed to find possible cross-identifications (see Col. 7).

blackLang et al. (2005) report that for their radio sources QR 1, QR 2, and QR 3 no counterparts are found in the near-IR. This led these authors to discuss the possibility that the sources are ultracompact H II regions with ongoing star formation. We confirm the absence of K-band counterparts for these radio sources in our data.

Table 2:   Catalog of stars detected in the central Quintuplet cluster field.

3.2 Spectral classification

Classification of OB stars was performed according to Hanson et al. (2005,1996) and Morris et al. (1996), concentrating on the most prominent lines in the K-band region (H I 2.1661 m Br, He I 2.0587 m, He II 2.1891 m, C IV triplet around 2.0796 m, N III/C III 2.1155 m) for comparison with their template spectra. Additional He I lines (2.1127/37 m, 2.1499 m, 2.1623 m) were employed to distinguish supergiants from giants. Spectral peculiarities are given in Table 2 in the classical nomenclature and are followed by ``?'' in uncertain cases, such as noisy spectra or blends with atmospheric OH lines. An example of an O star spectrum is shown in Fig. 5.

Wolf-Rayet stars have been classified following the criteria from Crowther et al. (2006). For WC stars we measured line equivalent widths and determined the ratio C IV 2.079 m/C III 2.108 m. The ratio He II (2.189 m)/Br (2.166 m) was used for the subtype classification of WN stars. A strongly increasing continuum with wavelength was considered to indicate the dominance of warm dust emission, marked with ``d'' in the spectral classification.

Our sample contains eleven previously known WR stars, four WN, and seven WC. Two new WR stars are found in our sample, LHO 76 and 79.

We could not identify LHO 76 with any previously known source. Therefore we claim that this object is a newly discovered WR star in the Quintuplet cluster, and its spectral type is WC9d (Fig. 6). Following the naming scheme of van der Hucht (2001), this star would blacksqueeze in between the known stars WR 102da and WR 102db. A possible scheme to rename this group could be LHO  (new), WR 102db (old) WR 102dc (new), WR 102dc (old) WR 102dd (new), WR 102dd (old) WR 102de (new).

The other blacknew WR star - LHO 79 - has already been listed by Figer et al. (1999a) as qF 250, but classified as <B0 I. We re-classify this star as spectral type WC9d (see Fig. 7). blackThis increases the total number of WR stars in the sample to 13.

All WC stars turned out to be of late subtype, WC8 and WC9. In all cases the WC9 spectra blackdisplay dust emission, while the two WC8 spectra (LHO 34 and 47) are free of such contamination.

The stellar spectra of LHO 75 and 102 are blackparticularly drowned in dust emission. The diluted stellar lines appear unusually narrow. The identification of the classification line C III 2.110 m is questionable, making the WC9 subtype uncertain (``WC9?d'') for these two stars.

blackLate-type stars were classified using the dominating features of the absorption bands caused by the CO first overtone. We find both ¹²CO and ¹³CO absorption, the latter indicating late type (super-)giant stars (Goorvitch 1994; Wallace & Hinkle 1997; Kleinmann & Hall 1986). Figure 2 shows LHO 4 as an example blackof an M star. We then measured the equivalent width of the band-head CO (2-0) to determine the effective temperature

and spectral subtypes of the stars

following González-Fernández et al. (2008). The integer number Granges from 0 to 13 representing the subtypes from K0 to M7, e.g. G =6 gives M0. Derived G values were rounded to the next integer to blackdetermine the subtypes blackas listed in Table 2. Both relations are only applicable for (super-) giant stars, an assumption that blackis justified by the blackpresence of the ¹³CO band absorption mentioned aboveblack, as well as by the synthetic magnitudes, see Sect. 3.3. For seven stars, the measured equivalent width was so small that the resulting G value was slightly in the negative range. We classify these stars as ``K0?'' in Table 2 to indicate that they might be of an earlier spectral subtype.

Table 3:   Spectral-type distribution.

3.3 Photometry

From our flux-calibrated spectra, we derived synthetic K-band magnitudes. For comparability we chose the (K ``short'') filter of 2MASS, which is centered at 2.159 m, and used the calibration constant from Cohen et al. (2003) for the photometric zero point. blackFifteen LHO stars are in common with the sample of Glass et al. (1999). We compare our derived magnitudes with their values and obtain blacka mean agreement within black0.4 mag. The magnitudes obtained for all catalog objects are listed in Table 2. The number of stars per magnitude is shown in Fig. 8 as a histogram. blackThe distribution follows a power law up to  mag, which indicates that our catalog is complete to this magnitude.

blackTo determine the approximate luminosity class of our blacklate-type stars, we plotted their magnitudes blackversus their determined effective temperature (Fig. 9). For comparison we take models (Kurucz 1993) of G0, K0, and M0 stars of the luminosity classes I and III, with assumed masses of 1.1 , 0.8 , and 0.4 , respectively. The model fluxes are scaled for the adopted cluster distance of 8 kpc (Reid 1993) and diminished according to the average extinction of A_K = 3.28 mag (Figer et al. 1999a). The models are connected in Fig. 9 by solid lines to mark the approximate regions of the corresponding luminosity class. Most of our sample stars scatter around the line for supergiants. Some stars are slightly less bright and blacktherefore are assigned to luminosity class II. A few starsblack, LHO 6, LHO 7, and LHO 115, seem to be extremely brightblack, see Fig. 9.

3.4 Cluster membership

For all spectra in the catalog, we measured the wavelength of a prominent feature, Br  for blackearly-type stars and CO (2-0) for blacklate-type stars, and derived the radial velocity for the individual objects (Fig. 10 and Table 2). blackHeliocentric corrections were applied to the radial velocities. The black measurement errors can be expected to blackbe maximal 37 km s^-1 blackfrom the nominal spectral resolution of the instrument. The results may be more uncertain for some of the more noisy spectra (marked with ``:'' in Table 2).

Assuming that the blackfifteen bright Quintuplet stars from the QPM list (Glass et al. 1990) are real cluster members, we derived their mean radial velocity black , with a standard deviation of  km s^-1. This is in good agreement with the 130 km s^-1 found by Figer et al. (1999a). blackFor a prediction of the internal velocity dispersion of the cluster, we followed Kroupa (2002). Despite the reported young age, we assumed a virialized cluster, a star formation efficiency between 20 and 40 % (Kroupa 2002), and a stellar mass in the range of (Figer et al. 1999a). This yields a radial velocity dispersion of 8-18 km s^-1, which agrees with the determined standard deviation of the fifteen QPM stars,  km s^-1. Therefore we consider blackthe interval around as a blackcriterion for cluster membership. blackAs Fig. 10 shows, there are a few stars in our sample with lower radial velocities, blackprimarily of late spectral type. They blackhave to be considered as foreground objects, i.e. K or M dwarfs, and are marked ``f'' in Table 2.

4 Summary

We present blackthe first K-band spectral catalog of black160 stellar sources in the central region of the Quintuplet cluster. Integral field black spectra were obtained with the SINFONI-SPIFFI on UT4 from May to July 2006. Our catalog comprises blackflux-calibrated spectra of 98 black early-type stars (OB and WR) and 62 blacklate-type stars (K to M) blackwith a spectral resolution of . Table 3 lists the number of stars per spectral class.

All black160 sources are listed in Table 2 with their blackLHO number, which was assigned to the source in our data reduction and identification processes (Col. 1), the determined coordinates of the source (blackCols. 2 and 3), and the derived synthetic magnitude (Col. 4). The spectral type is given in Col. 5. black radial velocities (RV) are given in Col. 6, together with an assessment whether this RV value indicates a foreground object (``f''). Finally we give a complete list of aliases and cross-identification with previous catalogs and surveys in Col. 7. Note that about 100 objects of our list are cataloged here for the first time.

Two new WR stars blackof WC spectral subtype are found in our sample, LHO 76 and 79, increasing the number ratio WC:WN in the Quintuplet cluster to black10:6 in total (9:4 contained in our field). WC stars are outstandingly frequent and bright in the Quintuplet cluster. For comparison, blackthe WC:WN number ratios from van der Hucht (2006) are 0:17 for the Arches cluster, 12:17 for the central cluster, and 8:19 for Westerlund I, respectively. A difference blackto the solar neighbourhood blackWC:WN ratio of 38:25 black (van der Hucht 2001) can be seen. A detailed analysis of the WR star subsample with the Potsdam models for expanding atmospheres (PoWR) is in preparation.

blackAmong the new stars in our catalog there are a number of late-type supergiants. In case the red supergiants (RSG) are real cluster members, as supported by their radial velocities, the question of age and coeval evolution of the Quintuplet cluster has to be addressed again in this context.

The spectral atlas of the catalog is shown in Fig. 11; 98 stars are of early spectral type (O, B and WR), and 62 of late type (K and M). A few spectra are dominated by dust emission. For each detected source it comprises the flux-calibrated K-band spectrum in the wavelength range from 1.95 to 2.45 m. The spectra are binned to 4 Å , some spectra suffer from atmospheric OH emission lines. The ``LHO'' numbering of the stars refers to Table 2. The wavelength scale refers to the local standard of rest.

Acknowledgements

blackWe thank the anonymous referee for helpful suggestions on the manuscript. blackFurthermore, the authors thank A. Barniske for the valuable help in preparing the Phase 2 material. T. Szeifert and D. Nürnberger supported A. L. with very useful discussions on the ESO SINFONI-SPIFFI instrument, data reduction pipelines, its results and technical details in handling the huge amount of data. Furthermore A.L. thanks H. Todt for supporting, discussing, and writing IDL routines on integral field spectroscopy data in the reduction process. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. A. Liermann is supported by the Deutsche Forschungsgemeinschaft (DFG) under grant HA 1455/19.

References

• Abuter, R., Schreiber, J., Eisenhauer, F., et al. 2006, New Astron. Rev., 50, 398 [NASA ADS] [CrossRef] (In the text)
• Blum, R. D., Schaerer, D., Pasquali, A., et al. 2001, AJ, 122, 1875 [NASA ADS] [CrossRef] (In the text)
• Bonnet, H., Abuter, R., Baker, A., et al. 2004, The Messenger, 117, 17 [NASA ADS] (In the text)
• Cohen, M., Wheaton, W. A., & Megeath, S. T. 2003, AJ, 126, 1090 [NASA ADS] [CrossRef] (In the text)
• Crowther, P. A., Hadfield, L. J., Clark, J. S., Negueruela, I., & Vacca, W. D. 2006, MNRAS, 372, 1407 [NASA ADS] [CrossRef] (In the text)
• Eckart, A., Moultaka, J., Viehmann, T., Straubmeier, C., & Mouawad, N. 2004, ApJ, 602, 760 [NASA ADS] [CrossRef] (In the text)
• Eisenhauer, F., Abuter, R., Bickert, K., et al. 2003, in Instrument Design and Performance for Optical/Infrared Ground-based Telescopes, ed. M. Iye, & A. F. M. Moorwood, Proc. SPIE, 4841, 1548 (In the text)
• Figer, D. F. 2004, in The Formation and Evolution of Massive Young Star Clusters, ed. H. J. G. L. M. Lamers, L. J. Smith, & A. Nota, ASP Conf. Ser., 322, 49 (In the text)
• Figer, D. F., McLean, I. S., & Najarro, F. 1997, ApJ, 486, 420 [NASA ADS] [CrossRef]
• Figer, D. F., McLean, I. S., & Morris, M. 1999a, ApJ, 514, 202 [CrossRef]
• Figer, D. F., Morris, M., Geballe, T. R., et al. 1999b, ApJ, 525, 759 [CrossRef]
• Geballe, T. R., Najarro, F., & Figer, D. F. 2000, ApJ, 530, L97 [NASA ADS] [CrossRef] (In the text)
• Giveon, U., Sternberg, A., Lutz, D., Feuchtgruber, H., & Pauldrach, A. W. A. 2002, ApJ, 566, 880 [NASA ADS] [CrossRef]
• Glass, I. S., Moneti, A., & Moorwood, A. F. M. 1990, MNRAS, 242, 55P [NASA ADS] (In the text)
• Glass, I. S., Matsumoto, S., Carter, B. S., & Sekiguchi, K. 1999, MNRAS, 304, L10 [NASA ADS] [CrossRef] (In the text)
• González-Fernández, C., Cabrera-Lavers, A., Hammersley, P. L., & Garzón, F. 2008, A&A, 479, 131 [NASA ADS] [CrossRef] [EDP Sciences] (In the text)
• Goorvitch, D. 1994, ApJS, 95, 535 [NASA ADS] [CrossRef] (In the text)
• Gorlova, N., Lobel, A., Burgasser, A. J., et al. 2006, ApJ, 651, 1130 [NASA ADS] [CrossRef] (In the text)
• Hanson, M. M., Conti, P. S., & Rieke, M. J. 1996, ApJS, 107, 281 [NASA ADS] [CrossRef]
• Hanson, M. M., Kudritzki, R.-P., Kenworthy, M. A., Puls, J., & Tokunaga, A. T. 2005, ApJS, 161, 154 [NASA ADS] [CrossRef]
• Kleinmann, S. G., & Hall, D. N. B. 1986, ApJS, 62, 501 [NASA ADS] [CrossRef] (In the text)
• Kobayashi, Y., Okuda, H., Sato, S., Jugaku, J., & Dyck, H. M. 1983, PASJ, 35, 101 [NASA ADS]
• Kroupa, P. 2002, MNRAS, 330, 707 [NASA ADS] [CrossRef] (In the text)
• Kurucz, R. L. 1993, VizieR Online Data Catalog, 6039, 0 (In the text)
• Lang, C. C., Goss, W. M., & Wood, D. O. S. 1997, ApJ, 474, 275 [CrossRef]
• Lang, C. C., Figer, D. F., Goss, W. M., & Morris, M. 1999, AJ, 118, 2327 [CrossRef]
• Lang, C. C., Johnson, K. E., Goss, W. M., & Rodríguez, L. F. 2005, AJ, 130, 2185 [NASA ADS] [CrossRef]
• Law, C., & Yusef-Zadeh, F. 2004, ApJ, 611, 858 [NASA ADS] [CrossRef]
• Martins, F., Hillier, D. J., Paumard, T., et al. 2008, A&A, 478, 219 [NASA ADS] [CrossRef] [EDP Sciences] (In the text)
• Monet, D. G., Levine, S. E., Canzian, B., et al. 2003, AJ, 125, 984 [NASA ADS] [CrossRef] (In the text)
• Moneti, A., Glass, I., & Moorwood, A. 1992, MNRAS, 258, 705 [NASA ADS]
• Moneti, A., Glass, I. S., & Moorwood, A. F. M. 1994, MNRAS, 268, 194
• Morris, P. W., Eenens, P. R. J., Hanson, M. M., Conti, P. S., & Blum, R. D. 1996, ApJ, 470, 597 [NASA ADS] [CrossRef] (In the text)
• Nagata, T., Woodward, C. E., Shure, M., Pipher, J. L., & Okuda, H. 1990, ApJ, 351, 83 [NASA ADS] [CrossRef]
• Nagata, T., Hyland, A. R., Straw, S. M., Sato, S., & Kawara, K. 1993, ApJ, 406, 501 [NASA ADS] [CrossRef]
• Okuda, H., Shibai, H., Kobayashi, Y., et al. 1987, in Star Forming Regions, ed. M. Peimbert & J. Jugaku, IAU Symp., 115, 556
• Okuda, H., Shibai, H., Nakagawa, T., et al. 1989, in The Center of the Galaxy, ed. M. Morris, IAU Symp., 136, 281
• Okuda, H., Shibai, H., Nakagawa, T., et al. 1990, ApJ, 351, 89 [NASA ADS] [CrossRef] (In the text)
• Reid, M. J. 1993, ARA&A, 31, 345 [NASA ADS] [CrossRef] (In the text)
• Rousselot, P., Lidman, C., Cuby, J.-G., Moreels, G., & Monnet, G. 2000, A&A, 354, 1134 [NASA ADS] (In the text)
• Skrutskie, M. F., Cutri, R. M., Stiening, R., et al. 2006, AJ, 131, 1163 [NASA ADS] [CrossRef] (In the text)
• Tuthill, P., Monnier, J., Tanner, A., et al. 2006, Science, 313, 935 [NASA ADS] [CrossRef] (In the text)
• van der Hucht, K. A. 2001, VizieR Online Data Catalog, 3215, 0 (In the text)
• van der Hucht, K. A. 2006, A&A, 458, 453 [NASA ADS] [CrossRef] [EDP Sciences] (In the text)
• Wallace, L., & Hinkle, K. 1997, ApJS, 111, 445 [NASA ADS] [CrossRef] (In the text)

Footnotes

... sources

Based on observations collected at the ESO VLT (blackprogram 077.D-0281(A)).

...

Table 2 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/494/1137

...

Catalog in ascii mode will be available at the CDS in July 2009.

All Tables

Table 1:   List of observation blocks (OBs).

Table 2:   Catalog of stars detected in the central Quintuplet cluster field.

Table 3:   Spectral-type distribution.

All Figures

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