arXiv 0709.22652007-09-14astro-ph

Discovery of very high-energy gamma-ray emission from the LBL object BL Lacertae

MAGIC Collaboration, M. Hayashida, K. Berger, E. Lindfors, V. Vitale, R. Wagner, E. Lorenz

备注：: 4 pages, 5 figures, to appear in the proceedings of the 30th International Cosmic Ray Conference, Merida, July 2007, on behalf of the MAGIC Collaboration

英文摘要：

The low-frequency peaked BL Lac (LBL) object BL Lacertae was observed with the MAGIC telescope from 2005 August to December (22.2 hr), and from 2006 July to September (26.0 hr). A very high energy (VHE) gamma-ray signal was discovered with a 5.1 sigma excess in the 2005 data. Above 200 GeV, an integral flux of (0.6+-0.2)x10e-11 m-2 s-1 was measured, corresponding to approximately 3% of the Crab flux. The differential spectrum between 150 and 900 GeV is rather steep, with a photon index of -3.6+-0.5. The light curve shows no significant variability during the observations in 2005. For the first time a clear detection of VHE gamma-ray emission from an LBL object was obtained. The 2006 data show no significant excess. This drop in flux follows the observed trend in optical activity

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

阅读原文

阅读 PDF ↗

arXiv 页面 ↗HTML 原文 ↗

本文内容

英文摘要相关论文

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

继续探索

相关论文

Discovery of very high energy gamma-ray emission from the low-frequency peaked BL Lacertae object BL Lacertae

The MAGIC collaboration observed BL Lacertae for 22.2 hr during 2005 August to December and for 26 hr during 2006 July to September. The source is the historical prototype and eponym of a class of low-frequency peaked BL Lacertae (LBL) objects. A very high energy (VHE) gamma-ray signal was discovered with a 5.1 sigma excess in the 2005 data. Above 200 GeV, an integral flux of 0.6+-0.2 x 10^(-11) cm^(-2) s^(-1) was measured, corresponding to approximately 3% of the Crab flux. The differential spectrum between 150 and 900 GeV is rather steep with a photon index of -3.6+-0.5. The light curve show…

2007-08-16astro-ph

The Radio Structure of High-Energy Peaked BL Lacertae Objects

We present VLA and first-epoch VLBA observations that are part of a program to study the parsec-scale radio structure of a sample of fifteen high-energy-peaked BL Lacs (HBLs). The sample was chosen to span the range of logarithmic X-ray to radio flux ratios observed in HBLs. As this is only the first epoch of observations, proper motions of jet components are not yet available; thus we consider only the structure and alignment of the parsec- and kiloparsec-scale jets. Like most low-energy-peaked BL Lacs (LBLs), our HBL sample shows parsec-scale, core-jet morphologies and compact, complex kilop…

2003-02-19astro-ph

BL的ROSAT X射线谱

The ROSAT X-ray Spectra of BL Lacertae Objects

我们利用WGA星表中给出的{ \it ROSAT}源的硬度比，研究了85个BL蝎虎座天体的X射线谱。这一样本包括所有具有高质量数据的WGA BL Lac，约占目前已知BL Lac的50%。我们发现，BL Lacs的能量幂律谱指数在0和3之间，平均值为$α_{\rm x}\sim 1.4$。然而，在通常选择在X射线波段的高能截止BL Lac（HBL）和通常在无线电勘测中发现的低能截止BL Lac（LBL）之间存在显著差异。HBL具有较陡的X射线光谱斜率（$α_{\rm x}\sim 1.5$），与$α_{\rm ox}$良好相关，与X射线-射电通量比和截止频率反相关，具有凸形的整体宽带光谱。另一方面，LBL具有更平坦的X射线谱（$α_{\rm x}\sim 1.1$）和凹的光学X射线连续谱。我们解释这些结果在不同的机制负责X射线发射的两个类，即同步辐射和逆康普顿的HBLs和LBLs分别。观察到的差异是一致的假设，HBLs和LBLs提供动力的基本上是相同的非热发动机不同，主要是在他们的同步加速器截止能量。

1996-01-17astro-ph

The Mass Distribution of Black Holes in BL Lacertae Objects

In this {\it Letter}, we make an attempt to estimate the masses of black holes and their distributions in BL Lac objects. We find there is a bimodal population of black hole masses in BL Lacs: the first has a lower-mass peak centred at $\sim 7.0 \times 10^6\sunm$ composed of high frequency-peaked BL Lacs (HBLs) and the second is a higher-mass ($>10^9\sunm$) population composed of low frequency-peaked BL Lacs (LBLs). The low mass family of black holes in HBLs does not satisfy the Magorrian et al. relation whereas the high mass family in LBLs does this relation and is in agreement with Laor's li…

2001-12-28astro-ph

BeppoSAX Observations of 1 Jy BL Lacertae Objects. I

We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1 Jy sample plus one additional source. The collected data cover the energy range 0.1 - 10 keV (observer's frame), reaching ~ 50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the LBL type) display a relatively flat (alpha_x ~ 0.9) X-ray spectrum, which we interpret as inverse Compton emission. Four objects (2/3 of the LBL) show some evidence for a low-energy steepening which is likely due to the synchrotron tail merging in…

2001-05-09astro-ph

Radio Luminosities and Classificatory Criteria of BL Lacertae Objects

Using the sample of radio selected BL Lacertae objects (RBLs) and X-ray selected BL Lacertae objects (XBLs) presented by Sambruna et al. (1996), we calculated the luminosities of radio, optical and X-ray of each source and made the statistical analysis among the luminosities at different wave-bands, broad-band spectral indices from radio to X-ray ($α_{\rm rx}$) and peak frequencies ($ν_p$). Our results are as follows: (i) there is a positive correlation between radio luminosity $L_{\rm r}$ and $α_{\rm rx}$ and a negative correlation between $L_{\rm r}$ and $ν_p$. High-energy peak BL Lacs (HBLs…

2002-05-25astro-ph

更多相关论文收起更多论文

The classification of BL Lacertae objects: the Ca H&K break

We investigate why BL Lacertae objects (BL Lacs) have values of the Ca H&K break (a stellar absorption feature) lower than low-power radio galaxies and if its use is justified to separate the two classes. For this purpose we relate this parameter to the radio and optical core emissions, as well as to the X-ray powers, for a sample of ~90 radio sources. We find that the Ca H&K break value decreases with increasing jet powers, and that it also anti-correlates with the radio core dominance parameter but not with extended radio emission. Based on this we conclude that the Ca H&K break value of BL …

2002-07-02astro-ph

Coordinated Multiwavelength Observations and Spectral Variability Modeling of Gamma-Ray Blazars

Our recent progress on time-dependent modeling of the multiwavelength spectra and variability of blazars with leptonic and hadronic jet models is reviewed. Special emphasis is placed on X-ray spectral variability of low-frequency peaked (LBLs) and intermediate BL Lac objects (IBLs). As an example, recent observational and modeling results of an extensive multiwavelength campaign of BL Lacertae in 2000 are presented. It is demonstrated how combined spectral and variability modeling of LBLs and IBLs can significantly constrain emission models and potential variability scenarios. In the case of B…

2004-03-25astro-ph

The Accretion Rates and Spectral Energy Distributions of BL Lacertae Objects

We investigate the relationship between accretion rates and the spectral energy distributions (SEDs) of BL Lac objects, using a sample of objects for which published information on the host galaxies, emission-line luminosities, and peak frequencies and luminosities of their SEDs are available. The sample is composed of 43 BL Lac objects which have a relatively continuous distribution of peak frequencies. Under the assumption that the observed emission lines are photoionized by the central accretion disk, we use the line luminosities to estimate the accretion luminosities and hence accretion ra…

2002-07-15astro-ph

37 GHz observations of a large sample of BL Lacertae objects

We present 37 GHz data obtained at Metsahovi Radio Observatory in 2001 December - 2005 April for a large sample of BL Lacertae objects. We also report the mean variability indices and radio spectral indices in frequency intervals 5 - 37 GHz and 37 - 90 GHz. Approximately 34 % of the sample was detected at 37 GHz, 136 BL Lacertae objects in all. A large majority of the detected sources were low-energy BL Lacs (LBLs). The variability index values of the sample were diverse, the mean fractional variability of the sample being ΔS_2 = 0.31. The spectral indices also varied widely, but the average r…

2007-05-07astro-ph

Are the X-ray Spectra of Flat-spectrum Radio Quasars and BL Lacertae Objects Different?

We study the X-ray spectra of 114 flat-spectrum radio quasars (FSRQ) using the hardness ratios as given in the WGA catalogue of ROSAT sources. This sample includes all WGA FSRQ with high-quality data and comprises about 20 per cent of presently known such objects, which makes this the largest FSRQ sample ever studied in the X-ray band. We find that FSRQ have a distribution of energy spectral indices ranging between 0 and 3 with a mean value alpha_x ~ 1. This is consistent with that of low-energy cutoff BL Lacs (LBL; alpha_x ~ 1.1), generally found in radio surveys, but significantly different …

1996-10-14astro-ph

On the relationship between BL Lacertae objects and radio galaxies

We present deep radio images at 1.4 GHz of a large and complete sample of BL Lacertae objects (BL Lacs) selected from the Deep X-ray Radio Blazar Survey (DXRBS). We have observed 24 northern sources with the Very Large Array (VLA) in both its A and C configurations and 15 southern sources with the Australia Telescope Compact Array (ATCA) in its largest configuration. We find that in the DXRBS, as in the 1-Jy survey, which has a radio flux limit roughly ten times higher than the DXRBS, a considerable number (about a third) of BL Lacs can be identified with the relativistically beamed counterpar…

2008-09-18astro-ph

Very high energy observations of the BL Lac objects 3C 66A and OJ 287

Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we have observed the BL Lac objects 3C 66A and OJ 287. These are members of the class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three LBLs predicted by Costamante and Ghisellini to be potential sources of very high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae, has recently been detected by the MAGIC collaboration. Our observations have not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab…

2007-07-18astro-ph

Discovery of >350 GeV Gamma Rays from the BL Lacertae Object 1ES 2344+514

We present the discovery of >350 GeV gamma-ray emission from the BL Lacertae object 1ES 2344+514 with the Whipple Observatory 10m gamma-ray telescope. This is the third BL Lac object detected at gamma-ray energies above 300 Gev, the other two being Markarian 421 (Mrk 421) and Mrk501. These three active galactic nuclei are all X-ray selected and have the lowest known redshifts of any BL Lac objects currently identified. The evidence for emission derives primarily from an apparent flare on December 20, 1995 when a 6 sigma excess was detected with a flux approximately 63% of the very high energy …

1997-12-24astro-ph

一个面向样本的BL蝎虎座天体目录

A Sample-oriented Catalogue of BL Lacertae Objects

我们提出了一个目录，233 BL Lacertae对象通过广泛的书目检索更新到1995年年中编译。目录中所列的很大一部分放射源属于定义明确的样本，可用于统计目的。一个较小的部分包括杂项（但确认）BL Lac和分类为BL Lac候选对象。我们讨论了不同样品的选择标准，报告发现了两个以前未被注意的BL Lacs在帕洛玛-格林调查，并评论一些仍然身份不明的高银河纬度伽马射线（EGRET）源与BL Lacs的可能关联。本文还简要讨论了星表的一些统计性质。

1995-11-15astro-ph

Discovery of Very High Energy $γ$-Rays from Markarian~180 Triggered by an Optical Outburst

The high-frequency-peaked BL Lacertae object Markarian~180 (Mrk~180) was observed to have an optical outburst in 2006 March, triggering a Target of Opportunity observation with the MAGIC telescope. The source was observed for 12.4 hr and very high energy $γ$-ray emission was detected with a significance of 5.5 $σ$. An integral flux above 200 GeV of $(2.3\pm0.7)\times10^{-11} {cm}^{-2} {s}^{-1}$ was measured, corresponding to 11% of the Crab Nebula flux. A rather soft spectrum with a photon index of $-3.3\pm0.7$ has been determined. No significant flux variation was found.

2006-09-22astro-ph

Discovery of Very High Energy gamma-rays from 1ES 1011+496 at z=0.212

We report on the discovery of Very High Energy (VHE) gamma-ray emission from the BL Lacertae object 1ES1011+496. The observation was triggered by an optical outburst in March 2007 and the source was observed with the MAGIC telescope from March to May 2007. Observing for 18.7 hr we find an excess of 6.2 sigma with an integrated flux above 200 GeV of (1.58$\pm0.32) 10^{-11}$ photons cm$^{-2}$ s$^{-1}$. The VHE gamma-ray flux is >40% higher than in March-April 2006 (reported elsewhere), indicating that the VHE emission state may be related to the optical emission state. We have also determined th…

2007-12-04astro-ph

Hadronic gamma-ray emission models

The discovery of rapid and simultaneous TeV/optical (UV, X-ray) variability provides strong evidence against the interaction between a thermal radiation field produced by an accretion flow and relativistic electrons in a jet as the origin of the gamma-rays in BL Lacertae objects. Synchrotron-self-Compton scattering (SSC) or proton-initiated cascades (PIC) remain viable mechanisms. The mechanisms predict very different magnetic field strengths and upper cut-off energies in the gamma-ray sources, i.e. the field strengths in SSC models are more than two orders of magnitude lower than in PIC model…

1996-12-06astro-ph

XMM-Newton observations of the TeV BL Lac object PKS 2155--304 in 2006: signature of inverse Compton X-ray emission?

This paper reports the first discovery of possible inverse Compoton (IC) X-ray emission below 10 keV in the typical high-energy peaked BL Lac object (HBL) PKS 2155--304. Two XMM-Newton observations performed in 2006 reveal that the 0.6--10 keV X-ray spectra of the source harden ($ΔΓ\sim$ 0.1--0.3) at break energies of about 4 keV. The concave X-ray spectra of the source could be easily interpretated by a mixture of a steep component (i.e., the high energy tail of the synchrotron emission) and a flat one (i.e., the low energy side of the IC emission). However, the steep spectra ($Γ\sim$ 2.3) in…

2008-04-23astro-ph

VERITAS Discovery of >200GeV Gamma-ray Emission from the Intermediate-frequency-peaked BL Lac Object W Comae

We report the detection of very high-energy gamma-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae (z=0.102) by VERITAS. The source was observed between January and April 2008. A strong outburst of gamma-ray emission was measured in the middle of March, lasting for only four days. The energy spectrum measured during the two highest flare nights is fit by a power-law and is found to be very steep, with a differential photon spectral index of Gamma = 3.81 +- 0.35_stat +- 0.34_syst. The integral photon flux above 200GeV during those two nights corresponds to roughly …

2008-08-07astro-ph

Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES 0806+524

The high-frequency-peaked BL-Lacertae object \objectname{1ES 0806+524}, at redshift z=0.138, was observed in the very-high-energy (VHE) gamma-ray regime by VERITAS between November 2006 and April 2008. These data encompass the two-, and three-telescope commissioning phases, as well as observations with the full four-telescope array. \objectname{1ES 0806+524} is detected with a statistical significance of 6.3 standard deviations from 245 excess events. Little or no measurable variability on monthly time scales is found. The photon spectrum for the period November 2007 to April 2008 can be chara…

2008-12-04astro-ph

The Flux Variability of Markarian 501 in Very High Energy Gamma Rays

The BL Lacertae object Markarian 501 was identified as a source of gamma-ray emission at the Whipple Observatory in March 1995. Here we present a flux variability analysis on several times-scales of the 233 hour data set accumulated over 213 nights (from March 1995 to July 1998) with the Whipple Observatory 10 m atmospheric Cherenkov imaging telescope. In 1995, with the exception of a single night, the flux from Markarian 501 was constant on daily and monthly time-scales and had an average flux of only 10% that of the Crab Nebula, making it the weakest VHE source detected to date. In 1996, the…

1999-03-05astro-ph