M. Mateo

University of Michigan, Ann Arbor, MI, United States

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Publications (81)93.88 Total impact

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    ABSTRACT: The color-magnitude diagrams of ~7 × 105 stars obtained for 12 fields across the Galactic bulge with the Optical Gravitational Lensing Experiment project reveal a well-defined population of bulge red clump giants. We find that the distributions of the apparent magnitudes of the red clump stars are systematically fainter when observing toward lower Galactic l fields. The most plausible explanation for this distinct trend is that the Galactic bulge is a bar whose nearest end lies at positive Galactic longitude. We model this Galactic bar by fitting the observed luminosity functions in the red clump region of the color-magnitude diagram for all fields. We find that, almost regardless of the analytical function used to describe the three-dimensional distribution of stars in the Galactic bar, the resulting models have the major axis inclined to the line of sight from 20° to 30°, with axis ratios corresponding to x0:y0:z0 = 3.5:1.5:1. This puts a strong constraint on the possible range of the Galactic bar models.
    The Astrophysical Journal 01/2009; 477(1):163. · 6.28 Impact Factor
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    ABSTRACT: We have obtained radial velocities of three K giants and one faint carbon star in LGS 3, a dwarf companion of M31, based on 12 individual spectra obtained with the HIRES spectrograph on the Keck I telescope. The mean precision of these measurements is 3.8 km s{sup {minus}1}. The mean systemic velocity of LGS 3 is {minus}282.2{plus_minus}3.5 km s{sup {minus}1}. Monte Carlo simulations that take into account the individual velocity uncertainties and the maximum observed velocity difference reveal that the central velocity dispersion of LGS 3 is in the range 2.6{endash}30.5 km s{sup {minus}1}, with 95{percent} confidence; the most likely value for the central dispersion is 7.9{sup {plus}5.3} {sub {minus}2.9} km s{sup {minus}1}. These results agree with the kinematics of H i gas in LGS 3. This contrasts with the tendency for the gas and stars in other low-luminosity Local Group dwarfs to exhibit distinct spatial and kinematic properties. Taking into account the relative youth of LGS 3, we conclude that the {open_quotes}asymptotic{close_quotes} M/L ratio{emdash}the value the galaxy would exhibit if it were composed only of ancient stars{emdash}is M/L{sub V,LGS3} {ge}11 (at a 97.5{percent} confidence level), with a most probable value of 95{sup {plus}175} {sub {minus}56}. These values are consistent with the M/L{sub V} ratios observed in other well-studied early-type dwarfs of the Local Group. We have also estimated the mass of LGS 3 using modified Newtonian dynamics. These data represent the first moderately high precision optical spectra of giants in a dwarf system beyond the Galactic halo. We suggest future studies that are now feasible to study the dynamics of dwarf galaxies throughout the Local Group and beyond. {copyright} {ital {copyright} 1999.} {ital The Astronomical Society of the Pacific}
    Publications of the Astronomical Society of the Pacific 02/1999; 111(757). · 3.23 Impact Factor
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    ABSTRACT: We undertook a long term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder -- M31 and M33 -- using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between September 1996 and October 1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, fourth in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31D $[(\alpha,\delta)= (11.\arcdeg03, 41.\arcdeg27), J2000.0]$. We have found 71 variable stars: 5 eclipsing binaries, 38 Cepheids and 28 other periodic, possible long period or non-periodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request. Comment: submitted to the Astronomical Journal, 30 pages, 20 figures; paper and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT/
    The Astronomical Journal 02/1999; · 4.97 Impact Factor
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    ABSTRACT: We undertook a long term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder -- M31 and M33 -- using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between September 1996 and October 1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, third in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31C [(alpha,delta)=(11.10, 41.42) deg, J2000.0}]. We have found 115 variable stars: 12 eclipsing binaries, 35 Cepheids and 68 other periodic, possible long period or non-periodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request. Comment: submitted to the Astronomical Journal, 39 pages, 27 figures; paper and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT/
    The Astronomical Journal 01/1999; · 4.97 Impact Factor
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    ABSTRACT: Star formation in the outermost regions of the LMC, several kpc from the center, has been dormant for some Gyr. With wide field imaging surveys, sufficient stars can be measured to accurately delineate the critical turn-off and subgiant-branch regions of the CMD, and thus provide a picture of the first 10 Gyr of star formation in the LMC. We describe plans for such a survey and present preliminary results.
    Proceedings of the International Astronomical Union 01/1999; 190.
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    ABSTRACT: We present deep HST color-magnitude diagrams of fields centered on the six old LMC globular clusters NGC 1754, NGC 1835, NGC 1898, NGC 1916, NGC 2005, and NGC 2019. Separate cluster and field star CMDs are shown. The time of formation of the LMC is studied from an analysis of the cluster CMDs. Based on a comparison of the CMDs with sequences of the Milky Way clusters M3, M5, and M55, we suggest that the LMC formed its first stars at the same time as the Milky Way to within 1 Gyr. We derive abundances and reddenings of the clusters that agree roughly with published values. Adopting our measured abundances, we find additional evidence that these LMC globular clusters are as old as the oldest Milky Way clusters through a comparison of our data with the horizontal branch evolutionary models of Lee, Demarque, and Zinn (1994). The evolution of the LMC following its formation is studied through an analysis of the field star CMDs. Through an automated comparison with stellar evolution models, we extract the star formation histories implied by the CMDs and luminosity functions. We explore the effects of varying the reddening, distance modulus, and IMF of the field stars on the derived star formation histories. We discuss the evidence for different star formation histories among the six fields.
    Proceedings of the International Astronomical Union 01/1999; 190.
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    ABSTRACT: This is a first step in the ongoing program to improve the direct distance estimate to two important galaxies in the cosmological distance ladder -- M31 and M33. The massive photometry we have obtained as part of our project DIRECT over the past 3 years provides us with very good light curves for known and new Cepheid variables. The light curves afford meaningful Fourier decompositions. As a result we are able to study the signature of the resonance center between the fundamental and the second overtone pulsational modes. Resonance signatures are sensitive to metallicity as already established by Cepheid studies in LMC, SMC, and the Galaxy. We make use of them to distinguish between Cepheids of different populations and metallicity inside each galaxy (M31 and M33). The handle on metallicity and large number of new Cepheids with very good BVI photometry helps us build improved period-luminosity (PL) relations for each galaxy. We derive their distances by using the standard technique of comparing PL relations, but are able to correct individually for extinction. The ultimate goal of project DIRECT is to derive direct Baade-Wesselink distances to Cepheids in M31 and M33, as well as direct distances to detached eclipsing binaries.
    11/1998; 30:1409.
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    ABSTRACT: The following tables contain the results of photometry performed on Hubble Space Telescope WFPC2 images of the Large Magellanic Cloud globular clusters NGC 1754, 1835, 1898, 1916, 2005, and 2019. The magnitudes reported here were measured from Planetary Camera F555W and F814W images using DoPHOT (Schechter, Mateo, & Saha 1993) and afterwards transformed to Johnson V/Kron-Cousins I using equation 9 of Holtzman et al. (1995PASP..107.1065H). We carried out photometry on both long (1500 sec combined in F555W, 1800 sec in F814W) and short (40 sec combined in F555W, 60 sec in F814W) exposures. Where the short exposure photometry produced smaller errors, we report those magnitudes in place of those measured from the long exposures. For each star, we give an integer identifier, its x and y pixel position as measured in the F555W PC image, its V and I magnitude, the photometric errors reported by DoPHOT, both the V and I DoPHOT object types (multiplied by 10 if the reported magnitude was measured in the short exposure frame), and a flag if the star was removed during our procedure for statistical field star subtraction. Summary of data reduction and assessment of photometric accuracy: Cosmic ray rejection, correction for the y-dependent CTE effect (Holtzman et al. 1995a), geometric distortion correction, and bad pixel flagging were applied to the images before performing photometry. For the photometry, we used version 2.5 of DoPHOT, modified by Eric Deutsch to handle floating-point images. We found that there were insufficient numbers of bright, isolated stars in the PC frames for producing aperture corrections. Aperture corrections as a function of position in the frame were instead derived using WFPC2 point spread functions kindly provided by Peter Stetson. As these artificially generated aperture corrections agree well with ones derived from isolated stars in the WF chips, we trust that they are reliable to better than 0.05 mag. In agreement with the report of Whitmore & Heyer (1997), we found an offset in mean magnitudes between the short- and long-exposure photometry. We corrected for this effect by adjusting the short-exposure magnitudes to match, on average, those of the long exposures. Finally, we merged the short- and long- exposure lists of photometry as described above and transformed the magnitudes from the WFPC2 system to Johnson V/Kron-Cousins I, applying the Holtzman et al. (1995PASP..107.1065H) zero points. Statistical field star subtraction was performed using color-magnitude diagrams of the field stars produced from the combined WF frames. Completeness and random and systematic errors in the photometry were extensively modelled through artificial star tests. Crowding causes the completeness to be a strong function of position in the frame, with detection being most difficult near the cluster centers. In addition, we found that crowding introduces systematic errors in the photometry, generally
    VizieR Online Data Catalog. 11/1998;
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    ABSTRACT: We report on HST observations of six candidate old globular clusters in the Large Magellanic Cloud: NGC 1754, NGC 1835, NGC 1898, NGC 1916, NGC 2005 and NGC 2019. Deep exposures with the F555W and F814W filters provide us with colour-magnitude diagrams that reach to an apparent magnitude in V of ~25, well below the main sequence turnoff. These particular clusters are involved with significantly high LMC field star densities and care was taken to subtract the field stars from the cluster colour-magnitude diagrams accurately. In two cases there is significant variable reddening across at least part of the image, but only for NGC 1916 does the differential reddening preclude accurate measurements of the CMD characteristics. The morphologies of the colour- magnitude diagrams match well those of Galactic globular clusters of similar metallicity. All six have well-developed horizontal branches, while four clearly have stars on both sides of the RR Lyrae gap. The abundances obtained from measurements of the height of the red giant branch above the level of the horizontal branch are 0.3 dex higher, on average, than previously measured spectroscopic abundances. Detailed comparisons with Galactic globular cluster fiducials show that all six clusters are old objects, very similar in age to classical Galactic globulars such as M5, with little age spread among the clusters. This result is consistent with ages derived by measuring the magnitude difference between the horizontal branch and main sequence turnoff. We also find a similar chronology by comparing the horizontal branch morphologies and abundances with the horizontal branch evolutionary tracks of Lee, Demarque, & Zinn (1994). Our results imply that the LMC formed at the same time as the Milky Way Galaxy.
    Monthly Notices of the Royal Astronomical Society 07/1998; · 5.23 Impact Factor
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    ABSTRACT: We have obtained 2640 CCD spectra with resolution ~4Å in the region 7250-9000Å for 976 stars lying near the red giant branches in color-magnitude diagrams of 52 Galactic globular clusters. Radial velocities of ~16km/s accuracy per star determined from the spectra are combined with other criteria to assess quantitative membership probabilities. Measurements of the equivalent widths of the infrared calcium triplet lines yield a relative metal-abundance ranking with a precision that compares favorably to other techniques. Regressions between our system and those of others are derived. Our reduction procedures are discussed in detail, and the resultant catalog of derived velocities and equivalent widths is presented. The metal abundances derived from these data will be the subject of a future paper. (c) Astronomical Society of the Pacific (1 data file).
    VizieR Online Data Catalog. 02/1998;
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    ABSTRACT: We undertook a long term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder -- M31 and M33, using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, detached eclipsing binaries provide us with the potential to determine these distances with an accuracy better than 5%. The massive photometry obtained in order to detect DEBs provides us with the light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries the distance estimates will be free of any intermediate steps. As a first step of the DIRECT project, between September 1996 and January 1997 we have obtained 36 full nights on the Michigan-Dartmouth-MIT (MDM) 1.3-meter telescope and 45 full/partial nights on the F. L. Whipple Observatory (FLWO) 1.2-meter telescope to search for detached eclipsing binaries and new Cepheids in the M31 and the M33 galaxies. In this paper, second in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31A ($\alpha_{2000.0},\delta_{2000}=11.34\deg,41.73\deg$). We have found 75 variable stars: 15 eclipsing binaries, 43 Cepheids and 17 other periodic, possible long period or non-periodic variables. The catalog of variables, as well as their photometry and finding charts, are available using the anonymous ftp service and the WWW. The CCD frames are available on request. Comment: submitted to the Astronomical Journal, 29 pages, 18 figures; paper and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/papers/M31A/ and through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT/
    The Astronomical Journal 12/1997; · 4.97 Impact Factor
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    ABSTRACT: During 1996 and 1997 we have obtained 95 nights on the FLWO 1.2-meter telescope and 35 nights on the MDM 1.3-meter telescope to search for detached eclipsing binaries and Cepheids in the M31 and the M33 galaxies. This is a first step in the ongoing program to improve the direct distance estimate to two important galaxies in the cosmological distance ladder -- M31 and M33. Detached eclipsing binaries provide us with the potential to determine these distances with an accuracy better than 5% and possibly to better than 1%. The massive photometry provides us with good light curves for known and new Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. With both Cepheids and eclipsing binaries the distance estimates will be free of any intermediate steps. We present the lightcurves of the Cepheids found in M31 and M33 and discuss the period-luminosity relations derived in different regions of the disk. We study the effects of differential extinction and metallicity, as well as the distribution of Cepheids in different spiral arms.
    11/1997; 29:1242.
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    ABSTRACT: CCD photometry for 42 variables from the field of 47 Tuc = NGC 104 is presented. VI photometry for a large set of stars from the surveyed fields is also given. (3 data files).
    VizieR Online Data Catalog. 09/1997;
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    ABSTRACT: We have obtained 2640 CCD spectra with resolution ~4 Angstrom in the region 7250-9000 Angstroms for 976 stars lying near the red giant branches in color-magnitude diagrams of 52 Galactic globular clusters. Radial velocities of ~16 km/second accuracy per star determined from the spectra are combined with other criteria to assess quantitative membership probabilities. Measurements of the equivalent widths of the infrared calcium triplet lines yield a relative metal-abundance ranking with a precision that compares favorably to other techniques. Regressions between our system and those of others are derived. Our reduction procedures are discussed in detail, and the resultant catalog of derived velocities and equivalent widths is presented. The metal abundances derived from these data will be the subject of a future paper. Comment: To appear in August 1997 PASP. Also available at http://www.hia.nrc.ca/eprints.html
    Publications of the Astronomical Society of the Pacific 07/1997; · 3.23 Impact Factor
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    ABSTRACT: We present the Catalog of Periodic Variable Stars in the Galactic Bulge. The Catalog is based on observations collected during the OGLE (Optical Graviational Lensing Experiment) microlensing search: (1) 213 periodic variable stars brighter than Imag=18mag: 31 pulsating, 116 eclipsing and 66 miscellaneous type variables from the Baade's Window BWC field are presented. (2) 800 variable stars found in four Baade's Window fields BW1, BW2, BW3 and BW4 are presented. Among them 71 are classified as pulsating, 465 as eclipsing and 264 as miscellaneous type. (3) 644 variable stars: 64 pulsating, 352 eclipsing and 228 miscellaneous type were detected in four Baade's Window fields BW5, BW6, BW7 and BW8. Analysis of periodic variable stars found in overlapping regions of the Baade's Window fields yields an average completeness of the Catalog equal to about 80% of periodic variables objects registered in the OGLE databases and about 65% of all periodic variable stars in the observed region of the sky. (4) 631 variable stars: 59 pulsating, 348 eclipsing and 224 miscellaneous type were detected in third Baade's Window fields BW9, BW10, and BW11. (5) 574 variables stars: 44 pulsating, 369 eclipsing and 161 miscellaneous type were detected in four fields located symmetrically in the galactic latitude around the Galactic center: MM5-A, MM5-B, MM7-A and MM7-B. (3 data files).
    VizieR Online Data Catalog. 07/1997;
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    ABSTRACT: We present the fifth part of the OGLE Catalog of Periodic Variable Stars in the Galactic bulge. 574 variable stars: 44 pulsating, 369 eclipsing and 161 miscellaneous type were detected in four fields located symmetrically in galactic lattitude around the Galactic center: MM5-A, MM5-B, MM7-A and MM7-B. The Catalog and individual observations are available in digital form from the OGLE Internet archive.
    05/1997;
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    ABSTRACT: Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars -- 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries were identified -- 9 contact systems and 3 detached/semi-detached systems. Seven eclipsing binaries are located in the blue straggler region on the cluster color-magnitude diagram (CMD) and four binaries can be considered main-sequence systems. One binary is probably a member of the SMC. Eight contact binaries are likely members of the cluster and one is most probably a foreground star. We show that for the surveyed region of 47 Tuc, the relative frequency of contact binaries is very low as compared with other recently surveyed globular clusters. The sample of identified variables also includes 15 red variables with periods ranging from about 2 days to several weeks. A large fraction of these 15 variables probably belong to the SMC but a few stars are likely to be red giants in 47 Tuc. VI photometry for about 50 000 stars from the cluster fields was obtained as a by product of our survey. Comment: Latex file, l-aa style, 10 pages, 7 ps figures included. Submitted to A&A. Figure 8 available from ftp://sirius.astrouw.edu.pl/pub/jka/47Tuc/fig8.ps.Z
    Astronomy and Astrophysics Supplement Series 05/1997;
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    ABSTRACT: We undertook a long term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder -- M31 and M33, using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, detached eclipsing binaries provide us with the potential to determine these distances with an accuracy better than 5%. The massive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries the distance estimates will be free of any intermediate steps. As a first step of the DIRECT project, between September 1996 and January 1997 we have obtained 36 full nights on the Michigan-Dartmouth-MIT (MDM) 1.3-meter telescope and 45 full/partial nights on the F. L. Whipple Observatory (FLWO) 1.2-meter telescope to search for detached eclipsing binaries and new Cepheids in the M31 and the M33 galaxies. In this paper, first in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31B ($\alpha_{2000.0},\delta_{2000}=11.20\deg,41.59\deg$). We have found 85 variable stars: 12 eclipsing binaries, 38 Cepheids and 35 other periodic, possible long period or non-periodic variables. The catalog of variables, as well as their photometry and finding charts, are available using the anonymous ftp service and the WWW.
    The Astronomical Journal 04/1997; · 4.97 Impact Factor
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    ABSTRACT: This paper present the first part of the Optical Gravitational Lensing Experiment (OGLE) General Catalog of Stars in the Galactic Bulge. The catalog is based on observations collected during the OGLE microlensing search. This part contains 33196 stars brighter than I=18mag identified in the Baade's Window BWC field. Stars from remaining 20 OGLE fields will be presented in similar form in the next parts of the Catalog. (1 data file).
    VizieR Online Data Catalog. 04/1997;
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    ABSTRACT: Table 1 lists light curve parameters and rectangular coordinates for variables OGLEGC 71-211. Table 2 contains equatorial coordinates of variables OGLEGC 71-211. Tables (table3 to 203) contain V-band light curves for variables OGLEGC71-211. (3 data files).
    VizieR Online Data Catalog. 02/1997;

Publication Stats

1k Citations
93.88 Total Impact Points

Institutions

  • 1994–2009
    • University of Michigan
      • Department of Astronomy
      Ann Arbor, MI, United States
  • 1997–1999
    • Honolulu University
      Honolulu, Hawaii, United States
  • 1995
    • Princeton University
      • Department of Astrophysical Sciences
      Princeton, New Jersey, United States