Hypervelocity Stars. I. The Spectroscopic Survey

Abstract

We discuss our targeted search for hypervelocity stars (HVSs), stars traveling with velocities so extreme that dynamical ejection from a massive black hole is their only suggested origin. Our survey, now half complete, has successfully identified a total of four probable HVSs plus a number of other unusual objects. Here we report the most recently discovered two HVSs: SDSS J110557.45+093439.5 and possibly SDSS J113312.12+010824, traveling with Galactic rest-frame velocities at least +508+-12 and +418+-10 km/s, respectively. The other late B-type objects in our survey are consistent with a population of post main-sequence stars or blue stragglers in the Galactic halo, with mean metallicity [Fe/H]=-1.3 and velocity dispersion 108+-5 km/s. Interestingly, the velocity distribution shows a tail of objects with large positive velocities that may be a mix of low-velocity HVSs and high-velocity runaway stars. Our survey also includes a number of DA white dwarfs with unusually red colors, possibly extremely low mass objects. Two of our objects are B supergiants in the Leo A dwarf, providing the first spectroscopic evidence for star formation in this dwarf galaxy within the last ~30 Myr.

10 pages, uses emulateapj, accepted by ApJ

References in corpus (48)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Dwarf Galaxies of the Local Group
• The USNO-B Catalog
• The Fourth Data Release of the Sloan Digital Sky Survey
• SINFONI in the Galactic Center: young stars and IR flares in the central light month
• Abundance Patterns in the Draco, Sextans and Ursa Minor Dwarf Spheroidal Galaxies
• RVSAO 2.0: Digital Redshifts and Radial Velocities
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I
• The Updated Zwicky Catalog (UZC)
• Ejection of hypervelocity stars by the (binary) black hole(s) in the Galactic center
• Identification of A-colored Stars and Structure in the Halo of the Milky Way from SDSS Commissioning Data
• The Present and Future Mass of the Milky Way Halo
• Discovery of an Unbound Hyper-Velocity Star in the Milky Way Halo
• A Catalog of Spectroscopically Identified White Dwarf Stars in the First Data Release of the Sloan Digital Sky Survey
• US 708 - An unbound hyper-velocity subluminous O star
• HE 0437-5439 -- an unbound hyper-velocity main-sequence B-type star
• Intermediate-mass star models with different helium and metal contents
• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• The Draco and Ursa Minor dwarf spheroidals. A comparative study
• The characteristics of high velocity O and B stars which are ejected from supernovae in binary systems
• Probing the Shape of the Galactic Halo with Hyper-Velocity Stars
• WFPC2 Observations of Leo A: A Predominantly Young Galaxy within the Local Group
• Variable Stars in Leo A: RR Lyraes, Short-period Cepheids, and Implications on Stellar Content
• Three-body encounters in the Galactic centre: the origin of the hypervelocity star SDSS J090745.0+024507
• A Successful Targeted Search for Hypervelocity Stars
• An Initial Survey of White Dwarfs in the Sloan Digital Sky Survey
• Cool White Dwarfs in the Sloan Digital Sky Survey
• The Fate of Former Companions to Hypervelocity Stars Originating at the Galactic Center
• N-body simulations of stars escaping from the Orion nebula
• The Red Giant Branch Tip and Bump of the Leo II dwarf spheroidal galaxy
• The RR Lyrae Distance to the Draco Dwarf Spheroidal Galaxy
• A Helium White Dwarf of Extremely Low Mass
• On the UV Bright Phase of Metal-Rich Horizontal-Branch Stars
• Modeling complete distributions with incomplete observations: The velocity ellipsoid from Hipparcos data
• Distant field BHB stars and the mass of the Galaxy I: Classification of halo A-type stars
• The distance to the Leo I dwarf spheroidal galaxy from the Red Giant Branch Tip
• Full-Fledged Dwarf Irregular Galaxy Leo A
• Deep HST Imaging of Sextans A. II. Cepheids and Distance
• Draco -- A Failure of the Tidal Model
• Wolf-Rayet and O Star Runaway Populations from Supernovae
• The Origins and Evolutionary Status of B Stars Found Far From the Galactic Plane II: Kinematics and Full Sample Analysis
• The Origins and Evolutionary Status of B Stars Found Far From the Galactic Plane I: Composition and Spectral Features
• The Hypervelocity Star SDSS J090745.0+024507 is a Short-Period Variable
• Distant field BHB stars and the mass of the Galaxy II: Photometry and spectroscopy of UKST candidates 16<B<19.5, 11<R<52 kpc
• The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A
• The Century Survey Galactic Halo Project I: Stellar Spectral Analysis
• The Century Survey Galactic Halo Project II: Global Properties and the Luminosity Function of Field Blue Horizontal Branch Stars
• Distant Field BHB Stars III: Identification of a probable outer halo stream at Galactocentric distance r = 70 kpc

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• Kinematics in galactic tidal tails - A source for Hypervelocity stars?
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• Probing the shape of the Milky Way dark matter halo with hypervelocity stars: a new method
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