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	Blazar - Wikipedia, the free encyclopedia
		A few rare objects may be "intermediate blazars" that appear to have a mixture of properties from both OVV quasars and BL Lac objecs.
		BL Lacertae shows many of the characteristics of quasars, but the optical spectrum was devoid of the spectral lines used to detemine redshift.
		As of 2003, a few hundreds of BL Lac objects are known.
	en.wikipedia.org /wiki/Blazar (1510 words)

	Blazar -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-28)
		The observed emission from a Blazar is greatly enhanced by (additional info and facts about relativistic effects) relativistic effects in the jet, a process termed (additional info and facts about relativistic beaming) relativistic beaming.The bulk speed of the plasma that constitues the jet can be in the range of 95%–99% of the speed of light.
		BL Lacertae shows many of the characteristics of quasars, but the optical (An ordered array of the components of an emission or wave) spectrum was devoid of the spectral lines used to detemine redshift.
		In 1972 a few variable optical and radio sources were grouped together and proposed as a new class of galaxy: (additional info and facts about BL Lacertae-type objects) BL Lacertae-type objects.
	www.absoluteastronomy.com /encyclopedia/b/bl/blazar.htm (1558 words)

	Blazar
		In astronomy, blazars, also known as BL Lac Objects or BL Lacs, are bright, starlike objects that can vary rapidly in their luminosity.
		The name of these objects comes from the prototype, a star-like object long believed to be a quite ordinary irregularly variable star.
		BL is a progressive ID not unlike car plates, and Lacerta is the constellation where it resides.
	www.brainyencyclopedia.com /encyclopedia/b/bl/blazar.html (491 words)

	BL Lac Meeting (Site not responding. Last check: 2007-10-28)
		The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties).
		For the large majority of BL Lacs the soft and medium energy X-ray bands are dominated by synchrotron emission and, unlike the case of OVVs, the emission mechanism is not in doubt.
		The BL Lac object Mkn 501, which is a source of TeV radiation, was observed with the BeppoSAX satellite on 7, 11, and 16 April 1997 during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA and CAT Cherenkov telescopes.
	www.astro.utu.fi /bl_lac98/abstracts.html (15225 words)

	Cormac Reynolds' Thesis
		The detection of significant quantities of thermal gas in the immediate vicinity of this object is somewhat unexpected given that BL Lac objects are distinguished from quasars by the small equivalent widths of their optical emission lines.
		If BL Lacs are shown not to be depleted in thermal gas on scales of ~ 1 pc, then it also seems likely that they are not depleted in gas on smaller scales and so some other explanation will be required to explain their low line luminosities.
		A kinematic model derived for the jet in BL Lac suggests that the flux density evolution of knots in the jet is not determined solely by changes in the Doppler factor resulting from changes in the direction of a constant speed jet.
	www.jive.nl /~reynolds/thesis/thesis.html (875 words)

	Excess of Mg II Absorbers in BL Lac Objects
		BL Lac objects are thought to be low-luminosity radio galaxies (Fanaroff-Riley 1974 class 1 sources, hereafter FR 1's) whose jet synchrotron and inverse-Compton emissions are Doppler-boosted (Blandford and Rees 1978; Urry and Padovani 1995).
		The detailed properties of many (but not all) BL Lac objects are consistent with this scenario, including (1) their presence in luminous early-type host galaxies (Abraham, Crawford, and McHardy 1992; Wurtz, Stocke, and Yee 1996) in poor clusters of galaxies (Wurtz et al.
		It is the high-z (z>0.5) BL Lac objects that are most discrepant in their properties, many of which have higher radio power levels than FR 1's and weak, quasar-like emission lines in their optical spectra (e.g., see Fig.
	ecf.hq.eso.org /~ralbrech/novdec97apjl/975444.html (3341 words)

	No Slide Title
		BL Lac objects are radio-loud AGN, with properties similar to quasars except for a lack of any strong emission lines.
		BL Lacs have a similar accretion process to radio-loud and radio-quiet quasars, but with a greater amount of outflow, which reduces the size of the accretion disk.
		BL Lacs have a different accretion process to quasars, in which a disk does not form – for example, an ADAF or ADIOS process with a low accretion rate.
	www.phys.unsw.edu.au /~mwhiting/papers/BLLac_poster_files/slide0001.htm (539 words)

	Warde_article
		BL Lacs are observed at a low beaming angle, typically less than 10 degrees, Quasars are galaxies that are observed at the same beaming angle as BL Lacs but which are much more energetic.
		Each parameter was tested within a specific range; we tested ro from.05 to.20, lo from 0.1 to 10.0, y from 1.0 to 4.0, x from 175.0 to 183.0 for the object BL Lac and from 265.0 to 273.0 for source 2134 +004, f from 0.0 to 360.0, and q from 4.0 to 10.0.
		The shock that appears in the BL Lac contour maps from August 2001 and January 2002 is called S11.
	www.sbc.edu /honors/HJSpecial_Iss04/Warde.htm (1318 words)

	News May 2002: Long XMM-Newton observation of the BL Lac Mkn 421 shows previous studies underestimate jet properties
		Some of them are bright radio sources, and a few of these radio galaxies are BL Lac objects, rare galaxies which look more like stars than galaxies in optical images.
		The X-rays from BL Lacs are thought to come from a jet of particles interacting with a magnetic field, giving rise to synchrotron radiation.
		Recent X-ray observations of the bright BL Lac object Markarian 421 made with XMM-Newton by Steve Sembay, Rick Edelson, Alex Markowitz, Gareth Griffiths, and Martin Turner from the Universities of Leicester and California.
	www.star.le.ac.uk /news/0402.html (793 words)

	Comments on Individual Sources
		Therefore, even though the line is clearly broad (FWHM=3800 km/s), this object is similar to objects such as Mkn 501 and BL Lac which share this property and must be classified as a BL Lac.
		We have classified this object as a radio galaxy; however, a higher signal-to-noise spectrum is clearly necessary to confirm its nature.
		We are classifying this object as a BL Lac because of its small equivalent-width emission line and low Ca H and K break contrast (C = 0.22).
	www.eso.org /~ppadovan/survey/dxrbs_paper/node9.html (1611 words)

	MARKARIAN 501 (Site not responding. Last check: 2007-10-28)
		Markarian 501 is an astronomical object known as a BL LAC object.
		(1996) and 2) observe the object during a gamma-ray/radio burst as observed in the spring of 1997.
		The object was observed on a nearly nightly basis through the summer and fall of 1997 and the early spring of 1998.
	www.astro.ufl.edu /~doug/research/mrk501.html (1263 words)

	Theory - Active Galactic Nuclei (Site not responding. Last check: 2007-10-28)
		The bright reddish object to the lower left of the center is a BL Lac object at the center of a cluster of galaxies.
		RGB 1745+398 was identified as a BL Lac object by Laurent-Muehleisen et al.
		The location of this nearby BL Lac object (z = 0.267) in the center of a cluster suggests that some portion of the X-ray emission is coming from the intra-cluster gas.
	www.mpe.mpg.de /theory/background-picture.html (276 words)

	EVN observations of the BL Lac object 1219+285 (ResearchIndex)
		EVN observations of the BL Lac object 1219+285 (ResearchIndex)
		EVN observations of the BL Lac object 1219+285
		It is strongly variable and polarized with the magnetic field orientated transverse to the VLBI jet [2], as typically observed in BL Lac objects.
	citeseer.ist.psu.edu /223494.html (379 words)

	I
		BL Lacertae type quasars, or blazars, are known for their violent variability at all observable wavelengths.
		BL Lac objects show neither absorption nor emission lines in their spectra and are believed to be the centers of relatively gas free galaxies.
		Quasars are also thought to be the centers of galaxies, at a distance of many billion light years away, but differ from BL Lac objects in that they do show emission lines.
	www.ifa.hawaii.edu /~mcgrath/0235.html (1550 words)

	[No title]
		According to the EUVE science team, the object is a tremendously energetic elliptical galaxy that radiates as much energy as a trillion suns.
		Some astrophysicists think such a galaxy, called a "BL Lac Object," may contain at its center a super-sized fl hole with a mass of 100 million suns and may be a cousin to the even more mysterious quasars.
		BL Lac Objects, like PKS 2155-304, vary dramatically in brightness in all other spectral regions.
	science.ksc.nasa.gov /shuttle/missions/status/r92-169 (659 words)

	[No title]
		We could neither detect the host galaxy nor a galaxy along the line-of-sight to the BL Lac as claimed from previous observations.
		All 4 companions have similar redshifts as the BL Lac and may (at least in part) trigger the enormous activity in this source.
		Alternatively, the BL Lac could also be located in the outskirts of a galaxy cluster or even be projected on a large-scale structure as indicated by spectra of 30 galaxies in the field.
	aspbooks.org /custom/publications/paper?paper_id=73 (224 words)

	BL Lac - Wikipedia, the free encyclopedia
		BL Lacertae, an active galaxy, prototype of the BL Lacertae objects
		BL Lac object, a type of active galaxy, based on the prototype BL Lacertae galaxy
		This is a disambiguation page — a list of articles associated with the same title.
	en.wikipedia.org /wiki/BL_Lac (90 words)

	antibloom (Site not responding. Last check: 2007-10-28)
		One of our observing projects involves monitoring PKS 0215+015, a BL-lac object with a resting 18.3 mag in V. The object is being monitored for a flare which will facilitate a spectral analysis of interposed hydrogen clouds with the Hubble Space Telescope.
		The object and field comparison stars are very close to SAO 110456, which shines at 5.58 in V. The SAO star causes severe blooming across the field during our normal 12 minute exposures (Figure 1).
		Different deep sky objects, exposures, and clocking frequencies were used to grade the efficacy of the anti-blooming.
	www.nfo.edu /antibloo.htm (1869 words)

	BL Lac Objects (Site not responding. Last check: 2007-10-28)
		BL Lacertae objects (BL Lac for short) exhibit no emission lines but have a strong continuum stretching from rf through X-ray frequencies.
		Here are spectra of BL Lac and other active galaxies - see the following description.
		Here are some light curves at different wavelengths illustrating the variability in intensity of BL Lac and some other active galaxies.
	csep10.phys.utk.edu /astr162/lect/active/BLlac.html (143 words)

	Homework #2 (Site not responding. Last check: 2007-10-28)
		The strong emission line in the spectrum (labeled Ly a) is formed when the electrons of hydrogen atoms jump from the first excited energy state to the ground state.
		Figure 2 shows the velocity at which an object of a given redshift is travelling away from us.
		Determine the radial velocity (as a fraction of the speed of light) of the quasar using figure 2 and the redshift you determined in a.
	www.astro.washington.edu /bbeck/102/hwlabexa/homework4.html (603 words)

	Quasars & AGN (Site not responding. Last check: 2007-10-28)
		OJ287 was the object of much attention in 1993, when an international group of professional astronomers drew up an observing program to monitor it using land based and satellite telescopes, and asked for amateurs to help with the long term study.
		This BL Lac object is the most distant on this list, estimated to be an astonishing 4 billion light years away.
		In 1971 it became the first radio source to be classified as a BL Lac object.
	www.belmontnc.4dw.net /qso.htm (689 words)

	Abstract (The X-ray Spectrum of the BL Lac Object EXO 055625-3838.6) (Site not responding. Last check: 2007-10-28)
		Abstract (The X-ray Spectrum of the BL Lac Object EXO 055625-3838.6)
		We report the results from observations of the BL Lac object EXO 055625-3838.6 carried out in the X-ray band using ROSAT and ASCA during 1993 and 1995.
		However, based upon the results presented here, we suggest the BL Lac probably did not contribute significantly to earlier hard X-ray observations made using collimated instruments.
	lheawww.gsfc.nasa.gov /~george/papers/timmy/abstract.html (188 words)

	VERON93 - Quasars and AGN
		The VERON93 database is the 6th edition of the Veron-Cetty & Veron "Catalogue of Quasars and Active Galactic Nuclei (1993)." It contains data for 7383 (+54) quasars, 1855 AGNs, and 171 BL Lac objects.
		Radio_Detect This is Yes if the object has been detected as a radio source and No if it is not a radio source.
		In the case of sources found not to be quasars, this is the value of the NEW class definition.
	heasarc.gsfc.nasa.gov /W3Browse/all/veron93.html (411 words)

	PSPC Spectral Analysis (Site not responding. Last check: 2007-10-28)
		Such a convex spectral shape is predicted by inhomogeneous synchrotron models which are fashionable for BL Lac jets.
		The oxygen absorption trough feature which was reported from Einstein OGS data of PKS 2155-304, another bright BL Lac object, would have too small an equivalent width to be observed with the PSPC, if it were present in MKN421 at the same strength.
		During the pointed observation, the source was almost a factor of 10 brighter so that a total of 5 million photons were accumulated for a very high statistical significance spectrum in the 0.1-3 keV range.
	wave.xray.mpe.mpg.de /rosat/calibration/old/resp_pspc.info3.txt (1935 words)

	[No title] (Site not responding. Last check: 2007-10-28)
		If a new object appears to be associated with another, with a know distance, then the distance to the new source becomes known as well.
		An example is a BL Lac type object with a featureless spectrum observed to be at the center of a galaxy with a known redshift.
		An example is another BL Lac object with the absorption lines in its spectrum observed to be at the same redshift as a galaxy which is seen in the same direction: the BL Lac object must be behind the galaxy.
	antwrp.gsfc.nasa.gov /diamond_jubilee/papers/pac/3109.node2.html (596 words)

	[98.06] Confirmed Identification of the BL Lac Object 3EG J0433+2908 (Site not responding. Last check: 2007-10-28)
		We present a formal multiwavelength examination of the EGRET source 3EG J0433+2908 and conclude that the source is a BL Lac type blazar.
		Archival radio data confirms that 87GB 0430+2859 is by far the brightest flat-spectrum radio source within the 95% confidence contour of J0433+2908; data taken at GBI incicate that this radio source is variable on a timescale of ~1 month at 2.25 GHz and 8.3 GHz.
		Spectroscopy indicates that the optical counterpart exhibits a red, featureless spectrum typical of BL Lac type blazars.
	www.aas.org /publications/baas/v33n4/aas199/884.htm (285 words)

	W Comae (Site not responding. Last check: 2007-10-28)
		This is demonstrated with the example of the radio-selected BL Lac object W Comae, which is currently on the source list of the STACEE and CELESTE experiments, based on extrapolations of the EGRET flux measured from this source, and on model predictions from hadronic blazar jet models.
		We suggest that detailed measurements and analysis of the soft X-ray variability of W Comae may be used to break the degeneracy in the choice of possible fit parameters, and thus allow a more reliable prediction of the VHE emission from this object.
		Thus, we suggest this object as a promising target for VHE gamma-ray and co-ordinated broadband observations to distinguish between leptonic and hadronic jet models for blazars.
	www.phy.ohiou.edu /~mboett/wcomae.html (284 words)

	AAVSO: Markarian 421, Winter 2004 Variable Star Of The Season
		Subclassified as a BL Lac object, Mark 421 is one of the closest entities of its kind.
		As the naming convention suggests, this object was once thought to be a variable star.
		The super compact object may possess the mass and gravitational pull of a million to a few billion Suns, with a resulting diameter of less than one light-minute to several light-days.
	www.aavso.org /vstar/vsots/winter04.shtml (2637 words)

	Is 0406 + 121 the reddest BL Lac object?
		While no optical counterpart was identified, similar sources were often found to be either BL Lac-type objects or high redshift QSOs.
		detected the object in the near-IR, where it was observed to vary in luminosity over the six-month period between August 1978 and March 1979.
		The object, clearly visible on an intensified TV guider, was wobbled every 80 s between two circular apertures 2.5 arc s in diameter spaced 20 arc s apart.
	www.nature.com /cgi-taf/DynaPage.taf?file=/nature/journal/v283/n5749/abs/283746a0.html (316 words)

	Active Galaxies and Quasars - HST looks at NGC 1275 (Site not responding. Last check: 2007-10-28)
		It is a strong radio source (3C 84), and shows variability that has occasionally been attributed to seeing a BL Lacertae-like object "off the beam".
		Adding to the confusion, there is clearly something rich in gas and dust in front of NGC 1275, though the interloper's redshift is 3000 km/s higher than that of NGC 1275 itself.
		It shows up as a network of dusty patches with some associated blue star clusters in this view, and can also be detected absorbing radio emission at certain frequencies from the nucleus itself (it is the absorption which guarantees it to be in front of NGC 125 and its active nucleus).
	www.astr.ua.edu /keel/agn/ngc1275hst.html (414 words)

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