Search for the event horizon evidences Search for the event horizon evidences by means of optical observations with by means of optical observations with

high temporal resolutionhigh temporal resolution

G.Beskin, V.Debur, S.Karpov, V.Plokhotnichenko

Special Astrophysical Observatory of Russian Academy of Sciences, Russia

XXVI General Assembly of International Astronomical Union, Prague, 2006

Search for Isolated Black Holes:Search for Isolated Black Holes:WhyWhy, What, Where and How, What, Where and How

● Final stages of stellar evolution● Isolated BH – special case of stellar evolution● Laboratory of strong gravitational fields● Its existence itself is a test for various theories

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, Why, WhatWhat, Where and How, Where and How

● Necessary features (for any theory):

Compactness – large mass for small size (M>3M0 for stellar mass BH)

High energy density

Fast variability ~ rg/c

● Sufficient feature the presence of event horizon

it is what separates the BH from all other classes of compact massive objects, which may present in alternative gravity theories.

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, Why, WhatWhat, Where and How, Where and How

● The presence of event horizon manifest itself in the emission of accreted matter in its vicinity. Redshift and radiation damping

Periodic components of emission

Variable polarization

etc, etc, etc...

● It is necessary to study the complete set of parameters of photons generated near the BH horizon with maximal possible time resolution (r

g/c ~ 10-5 s)

It is the accreting gas that makes it possible to «see» the event horizon (the BH itself), but there should not be plenty of it, to keep the horizon visible.

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, What, Why, What, WhereWhere and How and How

● «Standard laboratories»

Accreting black holes (M > 3M0) in X-ray binaries

accretion rate ~ 10-11 – 10-8 M0/year

Accreting supermassive BHs(M>106 M0) in active galactic nuclei

accretion rate ~ M0/year

Problem: the event horizon is screened due to high accretion rate● Isolated stellar-mass black hole (ISMBH) is the best object to detect

and study the event horizon

Low accretion rate, ~10-18 – 10-14 M0/year

Low optical depth, < 10-5 – the event horizon is open

~30 % of radiation comes from inside 2rg

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, What, Why, What, WhereWhere and How and How

● Observable Manifestations of ISMBH (Shvartsman 1971, Bisnovatyi-Kogan & Ruzmaikin1975, Ipser&Price 1982, ...)

Spherical accretion (for ~ 90% of Galaxy volume) Importance of magnetic field (ties the particles together) Equipartition of energies (gravitational, magnetic, kinetic, thermal…) Mostly optical (synchrotron) emission with flat featureless spectrum Fast variability due to MHD instabilities

● New results (Beskin & Karpov 2005) Magnetic field energy conversion (due to equipartition)

by reconnections of magnetic field lines in current sheets Acceleration of electrons in current sheets up to ~ 105

Nonthermal (hard) variable tail of emission spectrum Flares due to clouds of accelerated electrons

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, What, Why, What, WhereWhere and How and How

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, What, Why, What, WhereWhere and How and How

● Complete set of ISMBH manifestations: Number ~ 107 in the Galaxy (~1000 inside 300 pc)

Brightness: m ~ 16m – 25m

Featureless spectra from radio to gamma-rays

Mass > 3M0 (if it is possible to estimate)

Variability on wide time scale range 10-7 – 107 s

Critical feature – the shortest flares with ~ 10-7 – 10-5 s with particular spectral behaviour and possible polarization

Optical range is the best to detect and study

such set of critical properties

maximum information about each detected photon

Search for Isolated Black Holes:Search for Isolated Black Holes:Why, What, Where and Why, What, Where and HowHow

● In order to search for it one need The list of candidate objects (matching all or some of predicted

properties)

Special hardware to get complete information on each photon with time resolution of 10-7 s

Special software to analyze parameters of each photon

Special people ready to play flute in front of tulips like Erasm Darwin

Such activity had been started by Shvartsman in 1970s as a MANIA experiment

We are MANIACS!!!

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

●Objects-candidates Objects with Continuous Optical Spectra - ...OCOSes

radio - ROCOSesgamma - GOCOSesradio + x-ray - XROCOSes

● DC-dwarfs ~ 200 WDs without lines, 13m – 20m, I/I < 5%

● ROCOSes and XROCOSes~ 40, 15m – 22m , with limits on spectral features I/I < 1-5%(for example, Tsarevsky et al 2005, Marti et al 2004)

● GOCOSes – unidentified point-like gamma-ray (100 Mev) sourcesEGRET (1991-1995) - ~200 with square deg boxesexample:J0616-33 – 0.5 deg box ~150 x-ray sources, 75 optical identifications up to 22m ,~20% could be featureless (La Palombara et al 2004).

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

●Objects-candidates Candidates with estimation of masses

● Long microlensing events - MACHOs ( > 1 year)N = 3 with T = 490 – 1120 days, V

t ~ 31 – 79 km/s

OGLE III detects ~103 events / year, with expected ~3 long due to massive objects (BHs?)

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

●Objects-candidates Candidates with estimation of masses

● Self-lensing in binaries (Beskin & Tuntsov 2003)BH + WD – 106 – 107 binaries in Galaxy~103 till 23m

Optimal orientation probability ~ 3 ·10-3

For SDSS facilities - ~3 such binary systems per yearLAMOST - ~5 VISTA - ~5

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

● Softwareprocessing of photon time of arrivals to study the variability of emission Historical

y2-functions (Shvartsman 1977) – statistical analysis of time intervals between photons

Contemporary● Fourier power spectra● Light curve analysis – intensity statistics, normalized residuals and flares● Periodograms

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

● Hardware Russian 6-m BTA telescope

«Old maniacal epoch» (before 1997)● Standard multicolor photometer

with diaphragm using PMTs● U, B, V, R filters● 4 – 10 arcsec diaphragm● 10% quantum efficiency● 1 us time resolution● Real limit ~ 17m - 18m

MANIAMANIA - - MMultichannel ultichannel AAnalysis of nalysis of NNanosecond anosecond IIntensity ntensity AAlterationslterations

● Hardware Russian 6-m BTA telescope

«New maniacal epoch» (since 1998)● Development of position-sensitive

detectors (PSDs) with high timeresolution based on multichannelplates (MCPs) electron multiplication

The coordinates are measured by meansof comparison of electron charges on a different parts of a multi-segment cathode

● Now we may work with objects~ 2 - 3 mag fainter

PPosition-osition-SSensitive ensitive DDetectoretector

● Photocathode – S20 (3700 – 7500 )● MCP stack gain – 106.● Collector configuration – cross-like (4 electrodes)● Spatial resolution – 70 m (0.21'')● Time resolution – 700 ns● Number of pixels – 7·104

● Work diameter – 22 mm● Detector noise – 200-500 counts/s

PPosition-osition-SSensitive ensitive DDetectoretector

● Acquisition system «Quantochron 4-48» - special time-code convertor

● Designed as a PCI-slot device based on SPARTAN FPGA chip● Max data flow – 106 counts/s● Time resolution – 30 ns

MMultichannel ultichannel PPanoramic anoramic SSpectropolarimeterpectropolarimeter

● Modes of operation One-color (U, B, V, R) photometry and

polarimetry ● Panoramic, FOV ~ 1'

Four-color photometry and polarimetry● Object + comparison star, FOV ~15''

Spectropolarimetry● 1''-5'' slit

simultaneous measurement of 3 Stokes parameters

● Limits (good weather conditions) 20m – 21m for T=1h exposure

Spectroscopic Spectrololarimetric Multicolor photopolarimetric

Panoramic photopolarimetry

Photon counting

Results of Results of oldold MANIA program MANIA program

● DC-dwarfs 20 most interesting objects studied

● Long-time variability● Unusual colors

Upper limits derived

● Svar

< 50% - 2% for 10-6 – 40 s

● ROCOSes 20 most interesting objects studied

● Radio compactness● Long-time variability

Upper limits

● Svar

< 20% - 1% for 10-6 – 40 s

NewNew Results: Results: MACHO-99-BLG-22MACHO-99-BLG-22

● First direct single black hole candidate● Microlensing event with T=1120±90 days● Projected velocity – 75±8 km/s● Baseline magnitude – I=19.2m

● Model of lens position (Bennett et al 2002)

D=0.5 kpc M=130M0 Vt=70 km/s

D=2 kpc M=30M0 Vt=56 km/s

D=6 kpc M=3.5M0 Vt=19 km/s

NewNew Results: Results: MACHO-99-BLG-22MACHO-99-BLG-22● Optical limits:

Hubble ACS (Feb 27, 2005)● I < 20m

BTA MANIA (Jun 28, 2006)● Variable component: B < 21.2m

on 10-5 – 1 s time scale

● X-ray limits: RXTE PCA Scans (Revnivtsev,

Sunyaev 2002)< 10-11 эрг/с/см2

ROSAT All Sky Survey< 10-13 эрг/с/см2

XMM-Newton (Vestrand, unpublished)< 10-14 эрг/с/см2

5'' x 5''

NewNew Results: Results: MACHO-99-BLG-22MACHO-99-BLG-22

Distance > 2kpc 3.5M0 < Mass < 30M

0

Observations to be continued...

NewNew ResultsResults: ROCOSes (2006): ROCOSes (2006)

● 8C 0716+714 Highly variable radio + optical object with featureless spectrum

B=15.5

Studied on BTA in multicolor mode

Fractional RMS < 5% on 10-5 – 1 s

● J1942+10 (thanks to G.Tsarevsky) XROCOS with R=16.1

Studied on BTA in polarimetric mode

Fractional RMS < 10% on 10-5 – 1 s

Perspectives...Perspectives...

● New position-sensitive detector GaAr photocathode

QE ~ 50% over 4000 – 8500 16-electrode collector

spatial resolution ~ 10 – 20 m - like CCD

Number of pixels ~ 106 - like CCD

● Observations in Dec 2006

Our testbed - Our testbed - Crab pulsar Crab pulsar (2006)(2006)

Hearthbeat of a pulsar spectrum

Phased light curve with 5s resolution

We most likely already see several hundreds of isolated black holes

All we need is to prove it

Maniacs hope for the best