2.16/2.4m observations of nearby compact objects & field halo stars Jifeng Liu, Hang Gong, Jincheng Guo Chao Liu (NAOC), Yu Bai (BNU) Monday, July 9, 2012
what can 2.16/2.4 do ... for us nearby compact objects, to solve the following problems mass distribution of black holes single degenerate scenario for SN Ia field halo stars in solar neighborhood, to age date the halo Monday, July 9, 2012
stellar mass black holes: theoretical prediction expected mass distribution for compact remnants from supernova explosions, for different theoretical considerations define a black hole as above 3 solar masses, then neutron stars dominate black holes by a fact of 10 always a continuous black hole mass distribution, with a cutoff at 10-15 Ms about ~1e7 black holes and ten times more neutron stars expected for the Milky Way (or one black hole out of 10,000 stars given a total of 1e11 stars) credit: Fryer & Kalogera (2001) Monday, July 9, 2012
Schematic diagram for 20 here I show about two dozens of stellar mass black holes with dynamically determined masses. The sizes of the companions, the accretion disks are to the scale as shown here. We also dynamically show the inclination of each system. The color scale represents temperature of the star. There are three black hole binaries with high mass companions, and 17 with low-mass confirmed black companions. hole binaries the color scale represents temperature of the star missing here are M 33 X-3 IC 10 X-1 NGC 300 X-1 credit: Jerome Orosz Monday, July 9, 2012
confirmed stellar mass black holes there is a significant absence of black holes below 5-7 solar masses (Bailyn et al. 1998; Farr et al. 2010): either our picture for supernova explosion is seriously wrong, or we are limited by small numbers we need a lot more than two dozens of black holes to test the possibilities data taken from McClintock & Remillard (2006) Monday, July 9, 2012
why so few so far? before we discuss how to get more, let’s see why so few. the conventional method starts from an X-ray source in the sky, which usually corresponds to many counterparts in the optical: wait for X-ray outburst suggestive of NS/BH binaries- > the companion brightens up and is identified in the optical-> back to low hard state -> monitor the companion in the optical for the light curve and radial velocity curve -> fit to model to get binary properties and BH mass -> is it really a black hole? so it really relies on X-ray outburst -- but we know most black hole binaries are very quiet without X-ray outbursts in our life span, so it will miss most black holes -- no wonder so few even after fours decades of work by hundreds of researchers (who just waited in idle most of the time)! Monday, July 9, 2012
GR effect as revealed by matter around black holes matter accreted onto a black hole forms a disk, with increasingly higher now let’s see how black holes can be used to test GR. here I show around the black hole its accretion disk. When matter accretes onto the black hole, they temperatures inward toward the black hole -- eventually so hot that the radiation don’t fall directly into black hole because of the angular momentum. instead, they spiral in, and form an accretion disk. peaks at X-ray this intense X-ray (and UV) distinguishes black holes from normal stars! indeed, all known stellar mass black holes are X-ray binaries the accretion disk truncates at the innermost stable circular orbit - inside which the materials undergo free-all toward the black hole X-ray optical inner edge ultraviolet = ISCO Monday, July 9, 2012
revealing the missed “quiet” black holes The new approach: select black hole binary candidates in the optical/UV with the UV signature expected for the accretion disk, as manifested by the spectral energy distribution of known black hole binaries Monday, July 9, 2012
because they are magneti presence of Ca II H&K arou spectroscopic verification to distinguish b/w GALEX sources with repea generally less than 0.6ma To summarize, UV bright s distinguish b/w different p possible UV bright sources: quasars (with strong emission lines) hot white dwarfs (with broad absorption lines) early-type hot stars late-type cool stars with giant flares, or magnetically active (w/ signature spectral lines Ca II H&K and Ca II triplet @ ~8500A) all the above are contaminants, what we are looking for are: late-type cool stars + NS/BH with excess UV radiation from accretion disk and corona Monday, July 9, 2012
such an approach possible only now three components for the approach all-sky UV survey with GALEX (a space mission in UV) and all- sky optical survey with Sloan to select UV bright sources all-sky spectroscopic survey such as LAMOST , China’s large sky area multi-object fiber spectroscopy telescope, to weed out contaminants LAMOST survey began last October, and will observe ~15K UV- bright sources over 5 years Monday, July 9, 2012
SN Ia: SD or DD? SN Ia as standard candles: only phenomenological, complete confidence in this method only after we know what they are SD: WD accreting from a companion explodes when exceeding Chandrasekhar mass limit DD: two WDs spiral in and merge to explode where to find SD? supersoft X-ray sources: heavily absorbed WDs w/ mass much higher than 0.6Ms: these should be very hot and UV bright! --- GALEX! how many targets suitable for 2.16/2.4m? GALEX -x- Hip/APASS: about 200 w/ fuv-nuv < -0.3 mag, vt/g < 11mag Monday, July 9, 2012
what can 2.16/2.4m do? main work done by LAMOST targets selected by LAMOST will be followed up photometrically and spectroscopically to obtain the binary masses and geometry the very bright ones (<13m) can be observed with 2.16/2.4m at least ~100 WDs can be observed have they been observed before? Monday, July 9, 2012
age of the halo halo formation scenarios: in situ star formation and/or accretion, inner/outer halo age dating of halo globular clusters: 10-14Gyrs Kalirai+2012: 4 newly born halo white dwarfs: 11.5+-0.7 Gyrs “halo” stars at Main-sequence turn-off as seen in the T eff histogram, as a function of metalicity: 10-12 Gyrs (Jofre+2011) Monday, July 9, 2012
Monday, July 9, 2012
Monday, July 9, 2012
halo field stars select from SIMBAD stars w/ 1kpc, w/ radial velocity: 36219 determine 3D velocity: u,v,w determine membership: thin, thick, halo? ~480 halo stars, including 405 firm members Monday, July 9, 2012
Monday, July 9, 2012
Monday, July 9, 2012
age: 9-11Gyrs? need to improve the error estimate by removing contaminant s of binaries: new radial velocity from 2.16/2.4m verify/ obtain metalicity Monday, July 9, 2012
summary 2.16/2.4m spectroscopy bright UV-excess sources as hot massive WDs, or even black hole/neutron star binaries bright field halo stars in the solar neighborhood, to age date the halo and probe the halo formation history or Can we? 1A resolution for 13mag w/ reasonable exposures Monday, July 9, 2012
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