1. Optical counterparts to Ultraluminous X-ray sources Jeanette Gladstone - University of Alberta T. P. Roberts (U of Durham), A. D. Goulding (CfA) T. Cartwright & C. O. Heinke, (U of A), C. Copperwheat & A. J. Levan (U of Warwick), M. R. Goad (U of Leceister) Jeanette Gladstone - University of Alberta T. P. Roberts (U of Durham), A. D. Goulding (CfA) T. Cartwright & C. O. Heinke, (U of A), C. Copperwheat & A. J. Levan (U of Warwick), M. R. Goad (U of Leceister)

2. University of AlbertaJeanette GladstoneX-ray Universe 2011 What are Ultraluminous X-ray sources?  X-ray point source residing outside the nucleus of the galaxy  Thought to be X-ray binaries, containing black hole  L X > 10 39 erg s -1 (above Eddington limit for 10 solar mass black hole)  X-ray point source residing outside the nucleus of the galaxy  Thought to be X-ray binaries, containing black hole  L X > 10 39 erg s -1 (above Eddington limit for 10 solar mass black hole) composite X-ray (red)/optical (blue & white) image of the spiral galaxy M74 (NASA/CXC/U. Michigan/J. Liu et al.) We know they contain black holes but, what are their masses? What option do we have to explain their nature? Why do we care?

3. University of Alberta What are ULXs? Intermediate mass black holes  Missing link in the mass scale  Provide route to form super- massive black holes  Provide insight into the formation of galaxies Stellar mass black holes  Contain objects we can easily form  Some of the most extreme accretors in our universe  Provides a need for new accretion physics Jeanette GladstoneX-ray Universe 2011 Why do we care? Either way, we have something different and new to study After more than 30 years of study, we are currently unable to settle this in the X-ray band … how about optical? After more than 30 years of study, we are currently unable to settle this in the X-ray band … how about optical?

4. University of AlbertaJeanette GladstoneX-ray Universe 2011 Identification of optical counterparts  Can use unprecedented spatial resolution of the Chandra telescope  Allows for more accurate positioning of sources  Also need help of HST  Can use unprecedented spatial resolution of the Chandra telescope  Allows for more accurate positioning of sources  Also need help of HST From Zampier et al 2004 showing 90% confidence radii for various X-ray instruments against and ESO 3.6m R-band image of NGC 1313 X-2

5. University of Alberta New search for stellar counterparts  Search restricted <5 Mpc  Total of 45 ULXs  31 have both archival Chandra & HST data  23 have potential optical counterparts  Search restricted <5 Mpc  Total of 45 ULXs  31 have both archival Chandra & HST data  23 have potential optical counterparts Jeanette GladstoneX-ray Universe 2011 Gladstone et al in prep M81 X-6 NGC 3034 ULX6

6. University of AlbertaJeanette GladstoneX-ray Universe 2011 Optical counterparts - one stage further  38 potential counterparts, some are multiple  As data is archival, we have 1-5 bands for each  Magnitudes from available bands can be used to get first order estimate on stellar types  38 potential counterparts, some are multiple  As data is archival, we have 1-5 bands for each  Magnitudes from available bands can be used to get first order estimate on stellar types NGC 1313 X-1 IC342 X-1

7. University of Alberta Stellar types?  Reveals many are consistent with OB type stars (although some appear later- M, K & G type)  Absolute magnitudes more indicative of giant stars  Reveals many are consistent with OB type stars (although some appear later- M, K & G type)  Absolute magnitudes more indicative of giant stars Jeanette GladstoneX-ray Universe 2011 Need to account for X-ray irradiation effects, due to high levels of X-ray emitted from these sources. Need to account for X-ray irradiation effects, due to high levels of X-ray emitted from these sources.

8. University of Alberta Accounting for an accretion disc  Apply irradiation models to binary systems containing a black hole and a companion star  Black holes cover stellar and intermediate mass range 1000 M   Covers a range of stellar masses and radii  Multiple bands required so only able to apply to ~20 possible counterparts  Apply irradiation models to binary systems containing a black hole and a companion star  Black holes cover stellar and intermediate mass range 1000 M   Covers a range of stellar masses and radii  Multiple bands required so only able to apply to ~20 possible counterparts Jeanette GladstoneX-ray Universe 2011

9. University of Alberta Case 1: 8 40M  Case 2: M * < 20 M , 8 < R * < 80 R , M BH – no constraint Jeanette GladstoneX-ray Universe 2011 cos (i) = 0 cos (i) = 0.5 NGC 253 ULX2 Current data cannot provide us with enough information to differentiate We need multiple bands in the same epoch & deeper images to improve statistics

10. University of Alberta Another reason for constructing a catalogue …  Secondary aim of this catalogue was to search for optical counterparts that are bright enough to allow for optical spectroscopic follow-up  Highlighted several good sources for follow-up  Secondary aim of this catalogue was to search for optical counterparts that are bright enough to allow for optical spectroscopic follow-up  Highlighted several good sources for follow-up Jeanette GladstoneX-ray Universe 2011

11. University of Alberta Pilot spectra of the ULX counterparts Jeanette GladstoneX-ray Universe 2011  Gemini G-MOS spectra obtained  Gemini-S  NGC 1313 X-2, 3 hr  Gemini-N  NGC 5204 X-1, 0.8 hr  Ho IX X-1, 1.5 hr  Gemini G-MOS spectra obtained  Gemini-S  NGC 1313 X-2, 3 hr  Gemini-N  NGC 5204 X-1, 0.8 hr  Ho IX X-1, 1.5 hr

12. University of Alberta Varying He II emission? Jeanette GladstoneX-ray Universe 2011

13. University of AlbertaJeanette GladstoneX-ray Universe 2011  Slight complication …  A deeper look reveals extended He II emission  Single He II line contains 2 components  Currently don’t have the resolution to separate the two  We can work with limits however …  A deeper look reveals extended He II emission  Single He II line contains 2 components  Currently don’t have the resolution to separate the two  We can work with limits however … Ho IX X-1 Moon et al 2011

14. University of Alberta Constraining the mass? Jeanette GladstoneX-ray Universe 2011 Ho IX X-1 2σ upper limits: K < 97 km s -1

15. University of Alberta What are ULXs?  Cannot answer this as yet, do have lower limits  need photometry at multiple wavebands (and spectra) to help classify counterpart  Need greater signal-to-noise and/or resolution to start to statistically separate the He II components  Cannot answer this as yet, do have lower limits  need photometry at multiple wavebands (and spectra) to help classify counterpart  Need greater signal-to-noise and/or resolution to start to statistically separate the He II components  Confirmed 12 possible, identified 26 new potential candidates  Many consistent with OB classification (although some later giants also identified)  By accounting for X-ray irradiation, we are beginning to constrain their mass and radius Jeanette GladstoneX-ray Universe 2011 What about their companions?