Radio continuum searches for black holes in globular clusters Jay - PowerPoint PPT Presentation

Radio continuum searches for black holes in globular clusters Jay Strader (Michigan St) with Laura Chomiuk (Michigan St) Laura Shishkovsky (Michigan St) Tom Maccarone (Texas Tech) James Miller-Jones (Curtin) Anil Seth (Utah) Craig Heinke (Alberta) Greg Sivakoff (Alberta) Nadine Neumayer (MPIA) Eva Noyola (UNAM)

Low-mass X-ray binaries Accretion onto a compact object (neutron star or black hole) produces X-ray, optical, and radio emission

Radio & X-ray for BHs For BHs with low Corbel et al. 2013 accretion rates, L r ~ L x0.6 radio detection increasingly efficient Jonker/Hynes L r L x

Why Now? The VLA upgrade Bandwidth is 20x higher than old VLA: an enormous upgrade for radio continuum observations just by changing the electronics

How Non-detections Look 1 pc M19 VLA

M22: Central sources Strader et al. 2012 flux density ~ 55-60 uJy flat spectrum: S ~ v 0.0-0.2 central spatial location no X-rays VLA Chandra

Still not X-ray detected in new simultaneous Chandra data, have L X < 5 x 10 29 erg/s

Radio & X-ray Miller-Jones, JS et al., 2015 radio/X-ray ratio suggests these are BHs

Radio & X-ray Miller-Jones, JS et al., 2015 transitional MSP/LMXB appear to follow offset relation

Optical Counterparts? Strader et al. 2012 ~ 0.34 M WD?

Radio Proper Motions for M22 Sources Would completely rule out background sources Keep trying (and being foiled) at getting a clean 2nd epoch of data 46 +/- 6 uJy

M62: A nicer BH candidate 25” Chomiuk et al 2013 VLA Chandra (only 19 uJy!) power-law X-ray spectrum:

Radio & X-ray Redux Miller-Jones, JS et al., 2015 similar to V404 Cyg (longish period for BHXB) optical match is a red giant possible to get AO RVs: first set taken

A candidate in 47 Tuc 20” Miller-Jones, JS, et al 2015 ATCA Chandra

Radio & X-ray Miller-Jones, JS et al., 2015

Optical Data Optical counterpart is well-known UV- bright variable, with a UV HST spectrum HST (275W) HST (814W) Knigge et al. 2008 no He 1640 CIV

X-ray Data Heinke et al 2005 Unusual X-ray spectrum, consistent with the presence of OVIII emission

47 Tuc X9 in addition, there is a good upper limit on H- alpha emission from narrow-band HST photometry presence of C/O emission with no H/He emission suggests donor is a CO WD an HST broadband spectrum could rule out H emission and provide more evidence for ultracompact interpretation

M10 POSTER BY LAURA SHISHKOVSKY flat-spectrum radio source within core of cluster deep Chandra data will be taken this cycle (L X < 6 x 10 32 ) red giant counterpart

Population Conclusions? among BH candidate secondaries: 2 RGB stars, 1 MS star, 1-2 WDs, 1 sub-subgiant median distance of GC with BH candidates is 4 kpc: suggests search is sensitivity limited, and thus a large population of candidate BHs