High-Energy Gamma-Ray Emission from Galactic Kerr-Newman Black

THE ASTROPHYSICAL JOURNAL, 498 : 660È665, 1998 May 10 ( 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A.

HIGH-ENERGY GAMMA-RAY EMISSION FROM GALACTIC KERR-NEWMAN BLACK HOLES. II. THE RADIATIVE JETS BRIAN PUNSLY 4014 Emerald Street 116, Torrance, CA 90503 Received 1996 September 30 ; accepted 1997 December 9

ABSTRACT A model of the unidentiÐed high-latitude Galactic hard c-ray (EGRET) sources based on black hole electrodynamics is presented in this paper and its companion. The c-ray emission is produced in a bipolar outÑow from a charged, rotating black hole (Kerr-Newman black hole) in a low-density region of the Galaxy. The model is a synthesis of pair creation scenarios for pulsars, the theory of black hole magnetospheres and synchrotron self-Compton (SSC) large-scale jets. In this article it is shown that the resulting emission from the SSC jet is consistent with the constraints imposed on the broadband spectral energy distribution implied by the lack of identiÐcation of the c-ray sources in other frequency bands. Subject headings : black hole physics È gamma rays : theory È ISM : jets and outÑows È radiation mechanisms : nonthermal 1.

INTRODUCTION

able with changes of intensity by a factor of 5 or more being common (Thompson et al. 1995, 1996). Secondly Ozel & Thompson (1996) estimate peak apparent high-energy c-ray luminosities of 1È5 ] 1032 ergs s~1, assuming the emission is radiated isotropically from the source. However, the extreme time variability suggests relativistically beamed emission and Doppler enhancement can drastically increase Ñux levels along the line of sight. Thus, using the beamed Ñux value and assuming isotropic emission yields a value of apparent luminosity that can greatly exceed the intrinsic luminosity. It is crucial for the reader to discriminate between intrinsic and apparent luminosities for this reason. All of the luminosities in the following are intrinsic unless speciÐcally designated as apparent. Combining the time variability and the peak apparent c-ray luminosity from Ozel & Thompson (1996), one Ðnds that the average highenergy c-ray luminosity is less than 2 ] 1032 ergs s~1. The model of the radiative jets considered here is consistent with these properties of the broadband spectra of the most powerful of the high-latitude galactic high-energy c-ray emitters :

Approximately 70 of the high-energy c-ray detections of EGRET are unidentiÐed (Thompson et al. 1995, 1996 ; Mattox et al. 1997 ; Punsly 1997). Ozel & Thompson (1996) estimate that possibly half or more of the high-latitude (in Galactic coordinates, declination o b o [ 10¡) unidentiÐed EGRET sources are Galactic in origin. It is proposed in this paper and its companion (Punsly 1998) that a new class of object is responsible for many of these unidentiÐed sources of c-ray emission, rapidly rotating, charged Galactic black holes of a few solar masses : Kerr-Newman black holes. In this paper it is shown that the radiative jets driven by the black hole central engine described in Punsly (1998) can produce a broad band spectrum consistent with that of the unidentiÐed EGRET sources from 108È1025 Hz. First it is important to understand what is meant by an unidentiÐed source (Thompson et al. 1995, 1996 ; Mattox et al. 1997). The EGRET Ðeld of view, deÐned by the 95% conÐdence contour, is very large typically with a radius of [1¡. Within such a large Ðeld many faint radio sources and faint starlike objects can be found. The known high-latitude detections are strong Ñat spectrum radio sources, mostly quasars. The unidentiÐed Ðelds have no strong radio sources or known starlike objects with emission lines (i.e., possible quasars or BL Lacs) within the 95% conÐdence contour. Furthermore, there are no strong infrared or X-ray sources in the Ðeld. The adjective strong is subjective and one can assign a meaningful deÐnition in terms of the Ðeld size. Given the surface density of radio sources there is over a 50% chance of a source with 200 mJy of emission at 5 GHz to exist within the EGRET 95% conÐdence contours by random chance (Condon 1984 ; Punsly 1997). Thus there is no way to know if a source 200 mJy strong at 5 GHz is the c-ray radiator or not. Consequently, we have the approximate upper bound on radio luminosity that the unidentiÐed EGRET sources have less than 250 mJy of 5 GHz radio Ñux. Furthermore, we do not expect the sources to be particularly bright in the infrared, optical, X-ray or low-frequency radio bands or they would have been picked up in previous scans of the NASA Extragalactic Database (Mattox et al. 1996 ; Dingus et al. 1996). We do have more deÐnite constraints of the c-ray emission. First of all, the c-ray luminosities are extremely vari-

1. 2 ] 1032 ergs s~1 time-averaged apparent high-energy c-ray luminosity, 2. Order of magnitude variability in the c-ray luminosity, 3. Less that 50 mJy of radio Ñux at 5 GHz, 4. An inconspicuous optical apparent magnitude [16, 5. A dip in the spectral energy distribution in the X-ray band. Invoking galactic black holes to explain the observed behavior of extreme objects is not new in astrophysics. The existence of galactic black holes is widely accepted in the astrophysical community, the most notable black hole candidate is Cyg X-1 (Shapiro & Teukolsky 1983). However, the best known black hole candidates such as Cyg X-1 are, at most, only soft c-ray sources and are not EGRET detections (Thompson et al. 1995). Not coincidentally, there never has been the need to introduce a large-scale magnetic Ðeld to describe the emissivity of these black hole candidates at other frequencies. Thus, the heretofore acknowledged black hole candidates are considered to be at most weakly magnetized. However, recently two new potential galactic black hole 660

GAMMA-RAY EMISSION FROM BLACK HOLES. II candidates have been detected as soft c-ray repeaters (Mirabel & Rodriguez 1994 ; Tingay et al. 1995 ; Bailyn et al. 1995 ; Harmon et al. 1995 ; Hjellming & Rupen 1995), GRS 1915]105 and GRO J1655[40. These sources have bipolar outÑows and episodically they become much stronger hard X-ray sources than even Cyg X-1 (Mirabel & Rodriguez 1994). Levinson & Blandford (1996) have interpreted this bipolar outÑow as resulting from a highly magnetized accretion Ñow from a companion star onto a black hole. The accretion Ñow supports a large-scale poloidal magnetic Ðeld BP with BP B 108 G at the surface of the accretion disk (R. D. Blandford 1996, private communication). The black hole in the model is weakly magnetized by comparison as its potential bipolar outÑow is not needed to describe the emissivity of these soft c-ray repeaters. These black hole candidates are nondetections by EGRET (D. J. Thompson 1996, private communication). Thus, a highly magnetized accretion Ñow onto a weakly magnetized black hole, as proposed by Levinson & Blandford (1996) is not a viable model for the unidentiÐed EGRET detections considered here. However, it does lend support to the idea that strong magnetic Ðelds (with a largescale Ñux in excess of 1022 G cm2) can exist around galactic black holes. By analogy with other compact objects formed by stellar collapse, such as white dwarfs and neutron stars, one expects a galactic population of magnetized black holes. About 5% of white dwarfs are strongly magnetized (Shapiro & Teukolsky 1983) and strongly magnetized neutron stars are commonly believed to be pulsars (Michel 1982). If a certain fraction of the galactic black hole population is strongly magnetized then they have a heretofore unknown emissivity, as they are not associated with any of the astronomical sources currently described in the literature. Thusly motivated, it is proposed here that a new class of object, isolated magnetized black holes (i.e., no accretion disk or binary companion) resulting from stellar collapse is the parent population for the unidentiÐed high-latitude EGRET galactic detections. These Kerr-Newman black holes have a magnetic moment that is always parallel to the rotation axis, unlike neutron stars. Thus, they do not pulse like a neutron star can. The unidentiÐed EGRET sources show no evidence of pulsation (Thompson et al. 1995), and therefore there is no evidence that these are Geminga type pulsars. In the companion paper (Punsly 1998), it was established that a bipolar magnetically dominated MHD wind can be driven by a Kerr-Newman black hole immersed in a lowdensity region of the ISM. This wind can manifest itself as twin large-scale jets supporting a broadband luminosity. The model chosen for the central engine is a rapidly rotating black hole of 7 M with a polar magnetic Ðeld strength _ of 1010 G. The wind transports 3.5 ] 1032 ergs s~1 (in our model) in each hemisphere (see ° 4.4 of Punsly 1998). It was discussed in Punsly (1991) that such winds possibly dissipate strongly near the outer light cylinder, deÐned by the cylindrical radius r \ 1.44 ] 108 cm in our model, (see M This conclusion is based on the fact ° 4.3.2 of Punsly 1998). that this is not a unipolar inductor driven wind (as in a pulsar), but the unstable conÐguration of an ingoing Alfven wave (associated with the plasma injection mechanism) reÑecting from the black hole ergosphere. Furthermore, electromagnetic jets are generally considered to convert Poynting Ñux to mechanical and thermal inertia (shocks)

661

during interactions with the enveloping media (Begelman, Blandford, & Rees 1984 ; Marscher & Gear 1985). Consequently, we expect shocks or plasma instabilities to convert magnetic Ðeld energy to inertia beyond the light cylinder. In any event, we assume that the magnetically dominated black hole driven wind is transformed to an inertially dominated jet by one of the above dissipative processes when the cylindrical radius r \ 1.5 ] 108 cm (see Fig. 1). M With this assumption of inertial dominance, we compute the emissivity of the jet using the SSC (synchrotron selfCompton) model of Ghisellini, Maraschi, & Treves (1985) and Ghisellini & Maraschi (1989). The externally illuminated Compton models of Dermer & Schlickeiser (1993), Blandford & Levinson (1995), and Sikora, Begelman, & Rees (1994) are inappropriate because the black hole is in isolation and there is no signiÐcant soft photon source to illuminate the jet. Again, one must be careful to note the distinction between luminosity (meaning intrinsic power) and apparent luminosity (that which is measured at Earth assuming the Ñux was emitted isotropically even though it might be Doppler enhanced along the line of sight to Earth). The SSC models utilize relativistic beaming, thus the apparent luminosities exceed the intrinsic luminosities. Also note that in ° 4.4 of Punsly (1998), we calculated the synchrotron and c-ray luminosities from the particle creation zone, we associate these with the radiative luminosity of the plasma

FIG. 1.ÈLarge-scale structure of the MHD wind and SSC jet. The drawing is not to scale. The calculations in this paper refer to the Ñow downstream of the base of the paraboloidal region of the jet. Most of the high-energy c-rays are produced near the base of the paraboloidal jet.

662

PUNSLY

injection process in the central engine in contrast to the radiative luminosity of the jet. We Ðnd that the radiative luminosity of the black hole-jet system is dominated by the radiation from the SSC jet. In ° 2, we describe the paraboloidal region of the SSC jet (see Fig. 1). The high-energy c-rays are produced predominantly in the base of the paraboloidal portion of the jet as is typical of SSC models of EGRET sources. In ° 3, we discuss the fate of the stray c-ray luminosity from the particle acceleration gap introduced in ° 4.4 of Punsly (1998) and show that this is an unlikely source for the EGRET detected c-ray luminosity for an aligned jet. In ° 4, we model the conical region of the SSC jet. The next section is a computation of the large-scale radio luminosity. In ° 6, the broadband energy spectrum from 107 Hz radio through 1025 Hz hard c-rays is discussed. 2.

THE PARABOLOIDAL SSC JET

The SSC models of Ghisellini & Maraschi (1989) have two distinct regions, an inner paraboloidal jet and an outer conical extension. We consider the former here. Usually, the focus of such e†orts is to reproduce an observed blazar broadband spectrum without regards to the energy conservation budget within the jet (Sambruna et al. 1995 ; Maraschi, Ghisellini, & Celotti 1992 ; Pian et al. 1996). Here, we do better : we demand that the loss of thermal and mechanical energy from the jet as evaluated in the stationary frames of the hole, at large radial coordinate, equals the photon luminosity that is radiated away from the jet (integrated over 4n radians !). The cylindrical radius of the jet is given by r . In our M model r \ r x1@2 , M 0 r \ 1.5 ] 108 cm , 0 x 4 (R/R ) , 1 \ x \ 103 , 0 R \ 2.75 ] 1011 cm , 0

(2.1a) (2.1b) (2.1c) (2.1d)

and R [ R is the vertical distance from the base of the jet at x \ 1. 0 In equations (2.2)È(2.7) we parametrize an SSC jet that is roughly consistent with the energy conservation laws relating to the radiation losses. We assume that the electron energy spectrum that is injected into the jet above the light cylinder (by shocks and plasma instabilities) has a large population of very hot electrons. Namely, if c is the th thermal Lorentz factor, then the proper number density, n , p is chosen to satisfy

P

cmax

N c~1 dc , c th th 1 c (R ) \ 7.7 ] 103 , max 0 c (x) \ c (R )x~1@8 , max max 0 N (R ) \ 6.70 ] 107 cm~3 , c 0 n (R ) \ 7.50 ] 106 cm~3 . p 0 The Lorentz factor of bulk motion, ! , is 0 ! \ 1.80 , 0 n \ p

(2.2a) (2.2b) (2.2c) (2.2d) (2.2e)

(2.3)

Vol. 498

and it is taken as a constant. The jet makes an angle / to the line of sight to Earth / \ 15¡.00

(2.4)

that results in a constant Doppler enhancement factor d \ 2.85 (2.5) 0 The parameters in equations (2.1)È(2.3) yield a mechanical energy Ñux of 3.54 ] 1032 ergs s~1 at the base of the jet, matching the power delivered by the hole, L of ° 4.4 of wind Punsly (1998). The magnetic Ðeld at the base of the jet is mainly toroidal and is given by B \ 175G , 0 and as a function along the jet

(2.6a)

B(x) \ B x~1@2 . (2.6b) 0 Expression (2.6b) corresponds to conservation of Poynting Ñux. The loss of mechanical energy Ñux to radiation from the jet is given by the gradient in thermal inertia, (2.2c), and the variation in number density n(x) \ n x~1.5 . (2.7) 0 Equations (2.2c) and (2.7) are a crude way of mimicking the steepening of the electron thermal spectrum in (2.2a) due to radiation losses, in a manner that is amenable to simple SSC calculations. Using equation (13) of Ghisellini & Maraschi (1989), the apparent synchrotron luminosity observed at Earth is L B 4.5 ] 1033 ergs s~1 , (2.8) S with the energy concentrated in the frequency band, 1015È 1016 Hz (see Fig. 2). Note that this value exceeds the intrinsic luminosity of the jet found in ° 4.4 of Punsly (1998), due to Doppler enhancement. Similarly, computing the inverse Compton scattered radiation in the paraboloidal jet using (14) from Ghisellini & Maraschi (1989), the apparent c-ray luminosity at Earth, L , c is L [ 2.00 ] 1032 ergs s~1 . (2.9) c We note two changes from equation (14) of Ghisellini & Maraschi (1989) : 1. They are missing a factor of [c (a )/4n], in their nota1 0 (14), (see Tucker tion, in the expression for L (l) in equation c 1975). 2. The optical depth is increased by a factor of n by averaging the photon propagation path lengths over all directions in the jet. Most of the c-ray energy is emitted in the frequency band, 1023È1024 Hz (see Fig. 2). 3.

THE FATE OF GAP GAMMA-RAYS

It was discussed in ° 4.4 of Punsly (1998), that a Ñux of 1011È1012 eV stray c-rays are created within the gap that never pair create in the magnetic Ðeld. They carry an energy Ñux of 2.8 ] 1031 ergs s~1 and are a potential c-ray source for EGRET detection. The nature of the synchrotron spectrum from the paraboloidal jet depicted in Figure 2 indicates a peak at 5È40 eV. The scattering cross-section for

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GAMMA-RAY EMISSION FROM BLACK HOLES. II

663

FIG. 2.ÈBroadband spectral energy distribution for the jet model in the text. There are four distinct components : (1) low-frequency radio emission from an extended radio structure, (2) high-frequency radio emission from a large-scale jet, (3) synchrotron emission from the SSC jet, and (4) a c-ray SSC inverse Compton component.

pair creation of 5 ] 1011 eV c-rays with 5È10 eV UV photons is (Akhiezer & Berestetskii 1965) p B 10~25 cm2 . (3.1) c~S From the spectral energy distribution in Figure 2, if n is the s number density of synchrotron photons on the order of 5È40 eV, at the base of the jet, [n p ]~1 [ 109 cm . (3.2) s y~S Thus, equation (3.2) implies that the stray gap c-rays are converted to pair inertia at the base of the jet as a result of photonÈphoton scattering and are not a likely source of the EGRET detected c-ray Ñux. 4.

THE CONICAL JET

The conical region of the jet (see Fig. 1) produces virtually no c-ray luminosity and contributes to the low frequency portion (\5 ] 1013 Hz) of the synchrotron spectrum in Figure 2. The inertial energy Ñux at the terminus of the paraboloidal jet has been reduced by radiation losses (via eqs. [2.2c] and [2.7]) to be (S ) \ 8.39 ] 1030 ergs s~1 . (4.1) I final We match the energy Ñux from the paraboloidal jet to the conical jet and we note that the electrons have been cooled considerably in traversing the paraboloidal jet. Thus, we pick a steeper energy spectrum in the conical jet. Analogous to (2.2a) we choose in the cone the following param-

eterization n \ con

P

cmax

N c~2 dc , (4.2a) con th th 1 c (R ) \ 3.25 ] 103 , (4.2b) max 0 R \ 2.75 ] 1014 cm , (4.2c) 0 c (R) \ c (R )y~1@8 , (4.2d) max max 0 y 4 (R/R ) , 1 \ y \ 103 , (4.2e) 0 r \ r y , r \ 4.73 ] 109 cm , (4.2f ) M c c where R [ R is the vertical displacement from the base of the conical jet0at y \ 1. The thermal Lorentz factor, c , is maxjet. continuous through the terminus of the paraboloidal However, as we abruptly change the electron energy spectral index at the base of the conical jet and choose the energy Ñux, S , continuous, the local number density I changes discontinuously. Energy Ñux conservation from the paraboloidal to the conical jet implies that (R ) \ 1.72 ] 105 cm~3 con 0

n

(4.3a)

and we choose (R) \ n (R )y~2.00 (4.3b) con con 0 We also pick the magnetic Ðeld continuous through the jet transition n

B(R ) \ 5.53G , 0 B(R) \ B(R )y~1 . 0

(4.4a) (4.4b)

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Vol. 498

The bulk Lorentz and Doppler factors are constant and are the same as in the paraboloid, given by (2.3) and (2.5), respectively. At the end of the conical jet, 2.75 ] 1017 cm from the black hole, the energy Ñux in the jet has been reduced to

tance from Earth to (5.1) and (5.2) we expect a 5 GHz radio Ñux of

S \ 3.54 ] 1030 ergs s~1 . (4.5) rj This is the energy Ñux that can feed the large-scale radio jets.

F (178 MHz) B 679 mJy . l

5.

THE LARGE-SCALE RADIO STRUCTURE

The conical jet model terminates D0.1 pc from the hole. At this point there are still twin beams of 3.5 ] 1030 ergs s~1 of mechanical energy Ñux that can potentially power an extended radio structure. It is envisioned that the bipolar outÑow can power dual arcsecond scale radio jets and two lobes of extended radio emission. The Ñow is probably mildly relativistic or nonrelativistic in the lobes (Bicknell 1994). First, note that most of the energy Ñux to the lobes is manifested in supporting the Ðelds and the particles necessary to produce radio emission, it is not realized as radio emission proper (Rawlings & Saunders 1991). Denote the radio luminosity of the lobes as P . Rawlings & Saunders (1991) estimated that for a sampleE of radio galaxies, they could relate P to the energy of the jet S , by E rj S B 10P . (5.1a) rj E There was a spread in the values of the coefficient on the right-hand side (from 3 to 70), but most sources had a coefficient very close to 10. We assume that the extended radio structure of a Kerr-Newman black hole driven wind is similar to these radio galaxies. We therefore assume that relation (5.1a) is accurate for the case at hand. Thus we anticipate based on equations (4.5) and (5.1a), a radio luminosity from the extended structure P B 3.50 ] 1029 ergs s~1 . (5.1b) E Consider the spectral shape of the extended emission, through the spectral index, a , F P l~a0, where l is the l frequency and F is the spectral0 density. Using extragalactic l radio sources as a model, the low frequency extended structure is typiÐed by a B 1 (Kellerman, Pauliny-Toth, & Wil0 liams 1969). The large-scale jets have spectral indices of a B 0.70 (Bridle & Perley 1984). We assume that the extra0 galactic radio source spectra are representative of the extended emission of Kerr-Newman black holes. Thus, we choose for the overall radio spectrum (Fig. 2) a \ 1.15 , 107 Hz \ l \ 109 Hz , (5.2a) 0 a \ 0.75 , 109 Hz \ l \ 1011 Hz . (5.2b) 0 In order to Ðnd the expected observed spectrum from (5.1) and (5.2), we need to know the distance to the source. Note that from (2.9), the apparent c-ray luminosity is [2 ] 1032 ergs s~1 and Ozel & Thompson (1996) estimate that the undetected galactic high-latitude EGRET sources have peak apparent c-ray luminosities of 1È5 ] 1032 ergs s~1. The EGRET sources are variable and an average apparent c-ray power of 2 ] 1032 ergs s~1 makes our black hole model indicative of one of the stronger undetected highlatitude galactic c-ray sources. Thus, we place the black hole at the far end of the distance scale from Earth proposed by Ozel & Thompson (1996), at B500 pc. Applying this dis-

F (5 GHz) B 43 mJy , l and a 178 MHz Ñux of

6.

(5.3) (5.4)

THE BROADBAND SPECTRUM

Figure 2 displays the broadband emission from the bipolar outÑow powered by the Kerr-Newman black hole as predicted by the model described in the previous four sections. 6.1. Radio W avelengths The Ñux values of 43 mJy at 5 GHz and 679 mJy at 178 MHz shows that there exists models of c-ray loud KerrNewman black holes with too small an energy Ñux to appear in most radio surveys. If these are the missing EGRET sources then there should be no strong cataloged radio source associated with them. It should be noted that the model was constructed so as to have as little extended radio emission as possible. This was accomplished primarily by killing o† the inertial energy Ñux in the paraboloidal jet through equation (2.7). If the number density in (2.7) were chosen to die o† a little slower in the variable x, there would be more mechanical energy Ñux left in (4.5) that could feed the large-scale jets. It would be straightforward to construct models with 5 GHz Ñux densities of 100È200 mJy. The signiÐcance of this Ñux limit with regard to EGRET source identiÐcations and lack thereof was addressed in the introduction (° 1). There are simply too many of these weak radio sources in the large EGRET Ðelds to single out a radio source (Dingus et al. 1996 ; Mattox et al. 1996). 6.2. Optical W avelengths The Kerr-Newman black hole described in this model would appear as a 15thÈ16th magnitude blue star. In isolation it would have no emission lines. Conceivably, it could excite gas in surrounding nebulae, if they exist. The spectral Ñux should be somewhat variable due to the d2 dependence of emission from a jet (Lind & Blandford 1985). 6.3. UV W avelengths Most of the synchrotron energy is emitted in the ultraviolet. This might be a favorable band to detect these objects with the Hubble Space Telescope. The object would be variable in the UV due to the d2 dependence of the Ñux. 6.4. X-Ray L uminosity There is a dip in the spectral energy distribution of Figure 2 in the X-ray bands. There should be no cataloged X-ray source associated with EGRET detected Kerr-Newman black holes in isolation. 6.5. Gamma-Ray L uminosity The c-ray luminosity is peaked [1024 Hz in our model. The peak can be shifted quite easily in the SSC model. It appears difficult (or impossible) to achieve enough c-ray luminosity, with a weak optical synchrotron counterpart, in the SSC model if the peak is at a frequency less than 5 ] 1023 Hz. The energy in the c-ray band is variable

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GAMMA-RAY EMISSION FROM BLACK HOLES. II

because the total luminosity varies like d3 from a jet. The EGRET luminosity can change in the model by a factor of 2 if the jet wobbles from 15¡ to within 5¡ of the line of sight. Sambruna et al. (1995) and Maraschi et al. (1992) produce even larger variability in the c-ray spectrum of blazars by varying the parameters describing the injected electrons (i.e., spectral index and number density). The apparent c-ray luminosity is [2 ] 1032 ergs s~1 in agreement with Ozel & Thompson (1996). 7.

DISCUSSION

This paper and its companion utilize conventional astrophysical modeling (pair creation in vacuum gaps and SSC jets) in the setting of a Kerr-Newman black hole to reproduce the following observed properties of the putative highlatitude galactic EGRET sources : 1. Average apparent high-energy c-ray (EGRET) luminosities of D1032 ergs s~1, 2. High-energy c-ray variability, 3. Radio emission too low to be in a ““ strong ÏÏ source survey,

665

4. X-ray emission too low to be a survey, 5. Optically inconspicuous, apparent magnitude greater than 15 (except perhaps in a Ñare). The model created is successful in that it predicts EGRET sources that are not particularly active in other bands. As such, it was not clear how to model the spectrum in these other bands. We chose one SSC model in this paper, but it was not unique. The SSC model o†ers a wide variety of plausible output spectra. For instance, it might be that these sources are brighter in the optical than modeled here. If this is the case then a steeper spectral index in the c-ray band (it is Ñat in our model) will achieve the same luminosity as we found in ° 2. This article and its companion demonstrate two main concepts. Firstly, if plasma can be created on the vacuum Ðeld lines of a magnetized neutron star (a pulsar) then it can be created on the vacuum Ðeld lines of a Kerr-Newman black hole. Secondly, the power created in the KerrNewman magnetosphere can support an SSC jet that is compatible with the broadband luminosity of a putative class of high-latitude galactic EGRET sources.

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