BL Lacertae identifications in a ROSAT-selected sample of<i>Fermi</i>unidentified objects

Masetti, N.; Sbarufatti, B.; Parisi, P.; Jiménez‐Bailón, E.; Chavushyan, V.; Vogt, F.; Sguera, V.; Stephen, J. B.; Palazzi, E.; Bassani, L.; Bazzano, A.; Fiocchi, M.; Galaz, Gaspar; Landi, R.; Malizia, A.; Minniti, D.; Morelli, L.; Ubertini, P.

doi:10.1051/0004-6361/201322611

Cited by 42 publications

(57 citation statements)

References 77 publications

(158 reference statements)

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“…1RXS J083842.1−282723 3.1. Optical Spectroscopy Our mean spectrum of 1RXS J083842.1−282723 (Figure 2, upper panel) appears similar to that published by Masetti et al (2013), with strong, single-peaked Balmer and He I lines on a blue continuum. He II λ4686 is just detected with an emission equivalent width (EW) of ∼ 8Å, but is much less prominent than Hβ (EW ≈ 125Å).…”

Section: X-ray and Optical Observationssupporting

confidence: 76%

“…Now we know that transitional MSPs are distinguishable from CVs by their X-ray and optical light curves, which show characteristic dips and flares that are unique to this class de Martino et al 2013). We employed this test to reevaluate two ROSAT All-Sky Survey X-ray sources in Fermi error circles that were spectroscopically classified as CVs by Masetti et al (2013). Using X-ray and optical time-series data for one of these, 1RXS J154439.4−112820/3FGL J1544.6−1125, we concluded that it is almost certainly an MSP binary in the accreting state (Bogdanov & Halpern 2015).…”

Section: Introductionmentioning

confidence: 99%

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X-Ray and Optical Study of the Gamma-ray Source 3FGL J0838.8–2829: Identification of a Candidate Millisecond Pulsar Binary and an Asynchronous Polar

Halpern¹,

Bogdanov²,

Thorstensen³

2017

ApJ

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We observed the field of the Fermi source 3FGL J0838.8−2829 in optical and X-rays, initially motivated by the cataclysmic variable (CV) 1RXS J083842.1−282723 that lies within its error circle. Several X-ray sources first classified as CVs have turned out to be γ-ray emitting millisecond pulsars (MSPs). We find that 1RXS J083842.1−282723 is in fact an unusual CV, a stream-fed asynchronous polar in which accretion switches between magnetic poles (that are ≈ 120• apart) when the accretion rate is at minimum. High-amplitude X-ray modulation at periods of 94.8±0.4 minutes and 14.7±1.2 hr are seen. The former appears to be the spin period, while the latter is inferred to be one-third of the beat period between the spin and the orbit, implying an orbital period of 98.3 ± 0.5 minutes. We also measure an optical emission-line spectroscopic period of 98.413 ± 0.004 minutes, which is consistent with the orbital period inferred from the X-rays. In any case, this system is unlikely to be the γ-ray source. Instead, we find a fainter variable X-ray and optical source, XMMU J083850.38−282756.8, that is modulated on a time scale of hours in addition to exhibiting occasional sharp flares. It resembles the black widow or redback pulsars that have been discovered as counterparts of Fermi sources, with the optical modulation due to heating of the photosphere of a low-mass companion star by, in this case, an as-yet undetected MSP. We propose XMMU J083850.38−282756.8 as the MSP counterpart of 3FGL J0838.8−2829.

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Section: X-ray and Optical Observationssupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

X-Ray and Optical Study of the Gamma-ray Source 3FGL J0838.8–2829: Identification of a Candidate Millisecond Pulsar Binary and an Asynchronous Polar

Halpern¹,

Bogdanov²,

Thorstensen³

2017

ApJ

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“…Indeed two objects (1FHL J1223.3+7953 and 1FHL J2257.9-3644) have been optically classified as BL Lac objects. As already noted by Stephen et al (2010) and confirmed by Masetti et al (2013), the association of Fermi sources with soft X-ray counterparts favours discovery of this type of blazar. The preference for finding BL Lac when using soft X-ray data is very likely related to the SED of these objects compared to flat spectrum radio quasars.…”

Section: Discussionsupporting

confidence: 57%

Swift/XRT counterparts to unassociatedFermihigh-energy LAT sources

Landi

Bassani

Stephen

et al. 2015

A&A

Self Cite

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We report the results from our analysis of a large set of archival data acquired with the X-ray telescope (XRT) onboard Swift, covering the sky region surrounding objects from the first Fermi Large Area Telescope (LAT) catalogue of high-energy sources (1FHL), which still lack an association. Of the 23 regions analysed, 10 did not show any evidence of X-ray emission, but 13 were characterised by the presence of one or more objects emitting in the 0.3-10 keV band. Only in a couple of cases is the X-ray counterpart located outside the Fermi positional uncertainty, while in all other cases the associations found are compatible with the high-energy error ellipses. All counterparts we found have been studied in detail by means of a multi-waveband approach to evaluate their nature or class; in most cases, we have been able to propose a likely or possible association except for one Fermi source whose nature remains doubtful at the moment. The majority of the likely associations are extragalactic in nature, most probably blazars of the BL Lac type.

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“…For 114 sources with no redshift, it was possible to assign z ll as discussed in Sect. 3.2, and for another 12 we could only assign upper limits based on Shaw et al (2013b,a), Pita et al (2014), Furniss et al (2013), Danforth et al (2010), Masetti et al (2013), and Sbarufatti et al (2005b). There still remains 71 objects (12% of the confirmed HSPs) for which no z nor z ll could be estimated.…”

Section: The Redshift Distribution and Blazar Sequencementioning

confidence: 94%

“…Most of the redshift values come from BZCAT (Massaro et al 2009), from the recent optical spectroscopy work of Shaw et al (2013b), Masetti et al (2013), Pita et al (2014), from the SDSS Data Release 12, and from NED. Even though most of the previously identified HSPs showed BL Lac-like spectra, reliable redshift measurements are available when absorption features and/or the Ca H&K break are visible.…”

Section: The Redshift Distribution and Blazar Sequencementioning

confidence: 99%

1WHSP: An IR-based sample of ~1000 VHEγ-ray blazar candidates

Arsioli

Fraga

Giommi

et al. 2015

A&A

103

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Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E > ∼ 100 GeV) a high fraction of high Galactic latitude sources are blazars of the high synchrotron peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims. High synchrotron peaked blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray), we estimated synchrotron peak frequencies and fluxes of each object. Results. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is online at http://www.asdc.asi.it/1whsp/, providing a direct link to the SED building tool where multi-frequency data for each source can be easily visualised.

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BL Lacertae identifications in a ROSAT-selected sample ofFermiunidentified objects

Cited by 42 publications

References 77 publications

X-Ray and Optical Study of the Gamma-ray Source 3FGL J0838.8–2829: Identification of a Candidate Millisecond Pulsar Binary and an Asynchronous Polar

X-Ray and Optical Study of the Gamma-ray Source 3FGL J0838.8–2829: Identification of a Candidate Millisecond Pulsar Binary and an Asynchronous Polar

Swift/XRT counterparts to unassociatedFermihigh-energy LAT sources

1WHSP: An IR-based sample of ~1000 VHEγ-ray blazar candidates

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