Flaring X-Ray Emission from HST-1, a Knot in the M87 Jet

Harris, D. E.; Biretta, J. A.; Junor, W.; Perlman, E.; Sparks, W. B.; Wilson, A. S.

doi:10.1086/374773

Cited by 118 publications

(132 citation statements)

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“…X-ray data have been taken with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra satellite. For details of the Chandra data reduction procedures, see Harris et al (2003), Perlman et al (2003), and Harris et al (2009). In brief, a 1/8th segment of the back illuminated S3 chip of the ACIS detector aboard Chandra is used.…”

Section: X-raymentioning

confidence: 99%

“…This approach uses the event 1 file with no grade filtering (so as to recover all events affected by "grade migration") and energies from 0.2 to 17 keV are integrated so as to recover all the energy of the piled events. Other uncertainties for piled events come from the on-board filtering, the "eat-thy-neighbor" effect, and second-order effects such as release of trapped charge (see Appendix A of Harris Harris et al (2003), the basic analysis for this paper adopts the rectangular regions used in Harris et al (2006) so as to encompass more of the point-spread function. All events within each rectangle are weighted by their energy and the sum of these energies, when divided by the exposure times, gives the final keV s −1 value used in the light curve.…”

Section: X-raymentioning

confidence: 99%

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The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

ApJ

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175

146

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The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3−6)×10 9 M ) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) γ -ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE γ -ray emitter since 2006. The VHE γ -ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE γ -ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of τ rise (1-3) × 10 −11 photons cm −2 s −1 ), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken ∼3 days after the peak of the VHE γ -ray emission reveal an enhanced flux from the core (flux increased by factor ∼2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE γ -ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: [2002][2003][2004][2005][2006][2007][2008][2009]). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE γ -ray emission from M 87 are reviewed in the light of the new data.

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Section: X-raymentioning

confidence: 99%

Section: X-raymentioning

confidence: 99%

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

ApJ

Self Cite

175

146

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“…ObsID 011119010 of NGC 4636 and 13814 of NGC 5195 met these criteria, but a visual inspection showed low number counts in the hard band and were rejected from the sample. Finally, NGC 4486 was rejected because it is well known that this source is dominated by the jet emission (Harris et al 2003(Harris et al , 2006(Harris et al , 2009(Harris et al , 2011.…”

Section: Sample and Datamentioning

confidence: 99%

X-ray spectral variability of LINERs selected from the Palomar sample

Hernández-García

González‐Martín

Masegosa

et al. 2014

A&A

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Context. Variability is a general property of active galactic nuclei (AGN). The way in which these changes occur at X-rays is not yet clearly understood. In the particular case of low-ionization nuclear emission line region (LINER) nuclei, variations on the timescales from months to years have been found for some objects, but the main driver of these changes is still debated. Aims. The main purpose of this work is to investigate the X-ray variability in LINERs, including the main driver of these variations, and to search for possible differences between type 1 and 2 objects. Methods. We examined the 18 LINERs in the Palomar sample with data retrieved from the Chandra and/or XMM-Newton archives that correspond to observations gathered at different epochs. All the spectra for the same object were fitted simultaneously to study long-term variations. The nature of the variability patterns were studied by allowing different parameters to vary during the spectral fit. Whenever possible, short-term variations from the analysis of the light curves and long-term UV variability were studied. Results. Short-term variations are not reported in X-rays. Three LINERs are classified as non-AGN candidates in X-rays, all of them are Compton-thick candidates; none of them show variations at these frequencies, and two of them vary in the UV. Long-term X-ray variations were analyzed in 12 out of 15 AGN candidates; about half of them showed variability (7 out of the 12). At UV frequencies, most of the AGN candidates with available data are variable (five out of six). Thus, 13 AGN candidates are analyzed at UV and/or X-rays, ten of which are variable at least in one energy band. None of the three objects that do not vary in X-rays have available UV data. This means that variability on long-timescales is very common in LINERs. These X-ray variations are mainly driven by changes in the nuclear power, while changes in absorptions are found only for NGC 1052. We do not find any difference between type 1 and 2 LINERs, neither in the number of variable cases (three out of five type 1 and four out of seven type 2 LINERs), nor in the nature of the variability pattern. We find indications of an anticorrelation between the slope of the power law, Γ, and the Eddington ratio. Conclusions. LINERs are definitely variable sources irrespective of whether they are classified as optical type 1 or 2. Their BH masses, accretion rates, and variability timescales place them in the same plane as more powerful AGN at X-rays. However, our results suggest that the accretion mechanism in LINERs may be different. UV variations of some type 2 LINERs were found, this could support the hypothesis of a torus that disappears at low luminosities.

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“…Since most photons are of order 1 keV, the magnitudes of these two observational parameters are quite similar. Further details of our processing methods can be found in Papers I, III, and V of our series (Harris et al 2003(Harris et al , 2006(Harris et al , 2009.…”

Section: Data Processingmentioning

confidence: 99%

AN EXPERIMENT TO LOCATE THE SITE OF TeV FLARING IN M87

Harris¹,

Massaro

Cheung

et al. 2011

ApJ

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We describe a Chandra X-ray target-of-opportunity project designed to isolate the site of TeV flaring in the radio galaxy M87. To date, we have triggered the Chandra observations only once (2010 April) and by the time of the first of our nine observations, the TeV flare had ended. However, we found that the X-ray intensity of the unresolved nucleus was at an elevated level for our first observation. Of the more than 60 Chandra observations we have made of the M87 jet covering nine years, the nucleus was measured at a comparably high level only three times. Two of these occasions can be associated with TeV flaring, and at the time of the third event, there were no TeV monitoring activities. From the rapidity of the intensity drop of the nucleus, we infer that the size of the emitting region is of order a few light days × the unknown beaming factor; comparable to the same sort of estimate for the TeV emitting region. We also find evidence of spectral evolution in the X-ray band which seems consistent with radiative losses affecting the non-thermal population of the emitting electrons within the unresolved nucleus.

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Flaring X-Ray Emission from HST-1, a Knot in the M87 Jet

Cited by 118 publications

References 11 publications

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

X-ray spectral variability of LINERs selected from the Palomar sample

AN EXPERIMENT TO LOCATE THE SITE OF TeV FLARING IN M87

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