Isolated, Massive Supergiants near the Galactic Center

We have carried out a pilot project to assess the feasibility of using radio, infrared, and X-ray emission to identify young, massive stars located between 1 and 25 pc from the Galactic center. We first compared catalogs compiled from the VLA, Chandra, and 2MASS. We identified two massive, young stars: the previously identified star that is associated with the radio H II region H2 and a newly identified star that we refer to as CXOGC J174516.1-290315. The infrared spectra of both stars exhibit very strong Brγ and He I lines and resemble those of massive supergiants that have evolved off of the main sequence but not yet reached the Wolf-Rayet phase. We estimate that each star has a bolometric luminosity ≳106 L☉. These two stars are also associated with bright mid-infrared sources from the MSX survey, although the origin of this emission is uncertain. Likewise, the detection of these two sources in X-rays is surprising because stars at similar evolutionary states are not uniformly bright X-ray sources. Therefore, we suggest that both stars are in binary systems that contain either OB stars whose winds collide with those of the luminous supergiants or compact objects that are accreting from the winds of the supergiants. We also identify X-ray emission from a nitrogen-type Wolf-Rayet star and place upper limits on the X-ray luminosities of three more evolved, massive stars that previously have been identified between 1 and 25 pc from Sgr A*. Finally, we briefly discuss the implications that future searches for young stars will have for our understanding of the recent history of star formation near the Galactic center.

[1]  Carlos E. C. J. Gabriel,et al.  Astronomical Data Analysis Software and Systems Xv , 2022 .

[2]  W. N. Brandt,et al.  A Remarkable Low-Mass X-Ray Binary within 0.1 Parsecs of the Galactic Center , 2005, astro-ph/0503572.

[3]  E. Feigelson,et al.  The Spectra and Variability of X-Ray Sources in a Deep Chandra Observation of the Galactic Center , 2004, astro-ph/0403463.

[4]  Y. Nazé,et al.  HD 108: The mystery deepens with XMM-Newton observations , 2004, astro-ph/0402480.

[5]  Adam J. Burgasser,et al.  The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries , 2004, astro-ph/0402325.

[6]  Ferrara,et al.  X-ray/optical observations of A0535+26/HDE 245770 in quiescence , 2003, astro-ph/0309819.

[7]  M. Egan,et al.  Dusty ring nebulae around new candidate Luminous Blue Variables , 2003 .

[8]  R. Cutri.  Catalog generation for the 2MASS All-Sky data release , 2003 .

[9]  E. Serabyn,et al.  An Extended Star Formation History for the Galactic Center from Hubble Space Telescope NICMOS Observations , 2003, astro-ph/0309757.

[10]  T. Paumard,et al.  New results on the Galactic Center Helium stars , 2003 .

[11]  Mark Morris,et al.  Dynamical Friction on Star Clusters near the Galactic Center , 2003, astro-ph/0307271.

[12]  Simon Portegies Zwart,et al.  The Origin of IRS 16: Dynamically Driven In-Spiral of a Dense Star Cluster to the Galactic Center? , 2003, astro-ph/0303599.

[13]  R. Ignace,et al.  The Conspicuous Absence of X-ray Emission from Carbon-Enriched Wolf-Rayet Stars. , 2003, astro-ph/0303025.

[14]  John T. Rayner,et al.  SpeX: A Medium‐Resolution 0.8–5.5 Micron Spectrograph and Imager for the NASA Infrared Telescope Facility , 2003 .

[15]  W. N. Brandt,et al.  A Deep Chandra Catalog of X-Ray Point Sources toward the Galactic Center , 2003, astro-ph/0301371.

[16]  M. Egan,et al.  An Infrared Ring Nebula around MSX5C G358.5391+00.1305: The True Nature of Suspected Planetary Nebula Wray 17-96 Determined via Direct Imaging and Spectroscopy , 2002 .

[17]  S. White,et al.  Radio images of four luminous blue variable stars , 2002 .

[18]  R. Launhardt,et al.  The Nuclear Bulge of the Galaxy. III. Large-Scale Physical Characteristics of Stars and Interstellar Matter , 2002, astro-ph/0201294.

[19]  J. Nousek,et al.  Simulating CCDs for the Chandra Advanced CCD Imaging Spectrometer , 2001, astro-ph/0111003.

[20]  P. Hut,et al.  The Lives and Deaths of Star Clusters near the Galactic Center , 2001, astro-ph/0102259.

[21]  UCLA,et al.  Chandra X-Ray Spectroscopic Imaging of Sagittarius A* and the Central Parsec of the Galaxy , 2001, astro-ph/0102151.

[22]  M. Karovska,et al.  Early Chandra X-Ray Observations of η Carinae , 2001, astro-ph/0101206.

[23]  J. Blommaert,et al.  Mid-infrared imaging and spectroscopy of the enigmatic cocoon stars in the Quintuplet Cluster , 2000, astro-ph/0010558.

[24]  T. Berghöfer,et al.  ROSAT HRI observations of P Cyg and surrounding area , 2000 .

[25]  E. Serabyn,et al.  Hubble Space Telescope/NICMOS Observations of Massive Stellar Clusters near the Galactic Center , 1999 .

[26]  M. Burton,et al.  Isolated Hot Stars in the Galactic Center Vicinity , 1999 .

[27]  L. Burderi,et al.  The Two-Component X-Ray Broadband Spectrum of X Persei Observed by BeppoSAX , 1998 .

[28]  W. Goss,et al.  Ionized Gas in Sgr B2 Main on Scales of 0.065 Arcsecond (600 Au) , 1998 .

[29]  I. McLean,et al.  The Pistol Star , 1998 .

[30]  Howard A. Bushouse,et al.  Astronomical Data Analysis Software and Systems VII , 1998 .

[31]  M. Rieke,et al.  A spectral atlas of hot, luminous stars at 2 microns , 1996 .

[32]  P. Conti,et al.  Infrared Spectra of Massive Stars in Transition: WNL, Of, Of/WN, Be, B[e], and Luminous Blue Variable Stars , 1996 .

[33]  J. Schmitt,et al.  (Erratum) The ROSAT all-sky survey catalogue of optically bright OB-type stars. , 1996 .

[34]  E. Physik.  RONTGENSTRAHLUNG FROM THE UNIVERSE , 1996 .

[35]  Alfred Krabbe,et al.  The Nuclear Cluster of the Milky Way: Star Formation and Velocity Dispersion in the Central 0.5 Parsec , 1995 .

[36]  Kris Davidson,et al.  THE LUMINOUS BLUE VARIABLES: ASTROPHYSICAL GEYSERS , 1994 .

[37]  W. Wegner.  Intrinsic colour indices of OB supergiants, giants and dwarfs in the UBVRIJHKLM System , 1994 .

[38]  W. Goss,et al.  VLA Radio Recombination Line Observations of Ionized Gas in the -30 Kilometers per Second Molecular Cloud (G0.04+0.03) near the Galactic Center. I. The Discrete Radio Sources , 1993 .

[39]  C. Leitherer,et al.  What are the Mass-Loss Rates of O Stars? , 1993 .

[40]  Mark R. Morris,et al.  Massive star formation near the Galactic center and the fate of the stellar remnants , 1993 .

[41]  Mark R. Morris,et al.  Structural details of the Sagittarius A complex - evidence for a large-scale poloidal magnetic field in the Galactic center region , 1987 .