On the nature of the hard X-ray sources SWIFT J1907.3−2050, IGR J12123−5802 and IGR J19552+0044

Bernardini, F.; Martino, D. de; Mukai, K.; Falanga, M.; Andruchow, I.; Bonnet‐Bidaud, J. M.; Masetti, N.; Buitrago, Diego H. González; Mouchet, M.; Tovmassian, G.

doi:10.1093/mnras/stt1434

Cited by 34 publications

(72 citation statements)

References 69 publications

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“…Unsurprisingly, the strongest and sharpest peak is detected from I band (plotted in Figure 6 by red color) at a 17.7 cycles per day frequency corresponding to a 81.3 m period. This matches, within statistical uncertainty, the shortest X-ray periodic signal found by Bernardini et al (2013). The periodic signal is formed by a strong hump in the spectra of the object, which grows larger toward red wavelengths.…”

Section: Photometric Variability and Periodssupporting

confidence: 85%

“…The simultaneous multiband photometry shows that the amplitude of the variability depends on Bernardini et al (2013) wavelength ( Figure 1). We collected sufficient photometric data from various sources to analyze the complexity of light curves of IGR 1955+0044.…”

Section: Photometric Variability and Periodsmentioning

confidence: 99%

“…Thorstensen & Halpern (2013) obtained time series of spectroscopic and photometric data, but the coverage was insufficient to determine the period in either domain without ambiguity. Bernardini et al (2013) studied the X-ray behavior of the object using XMM-Newton. These authors point out that IGR 1955+0044 is a highly variable Xray source with a rather hard spectrum, showing also nearinfrared and infrared variability.…”

Section: Introductionmentioning

confidence: 99%

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IGR J19552+0044: A new asynchronous short period polar

Tovmassian

González–Buitrago

Thorstensen

et al. 2017

A&A

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Context. Based on XMM-Newton X-ray observations IGR J19552+0044 appears to be either a pre-polar or an asynchronous polar. Aims. We conducted follow-up optical observations to identify the sources and periods of variability precisely and to classify this X-ray source correctly. Methods. Extensive multicolor photometric and medium-to high-resolution spectroscopy observations were performed and period search codes were applied to sort out the complex variability of the object. Results. We found firm evidence of discording spectroscopic (81.29 ± 0.01 m) and photometric (83.599 ± 0.002 m) periods that we ascribe to the white dwarf (WD) spin period and binary orbital period, respectively. This confirms that IGR J19552+0044 is an asynchronous polar. Wavelength dependent variability and its continuously changing shape point at a cyclotron emission from a magnetic WD with a relatively low magnetic field below 20 MG. Conclusions. The difference between the WD spin period and the binary orbital period proves that IGR J19552+0044 is a polar with the largest known degree of asynchronism (0.97 or 3%).

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Section: Photometric Variability and Periodssupporting

confidence: 85%

Section: Photometric Variability and Periodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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IGR J19552+0044: A new asynchronous short period polar

Tovmassian

González–Buitrago

Thorstensen

et al. 2017

A&A

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“…Other CVs with more complex light curves and multiple periods have also been proposed as extreme asynchronous polars, most notably RX J0524+42, dubbed "Paloma" (Schwarz et al 2007;Joshi et al 2016), and IGR J19552+0044 (Bernardini et al 2013;Thorstensen & Halpern 2013). Paloma is suggested to have an orbital period of 157 minutes, and a spin period that is either 136 or 146 minutes, which are asynchronous by 14% or 7% respectively (Schwarz et al 2007).…”

Section: Xmm-newton Analysismentioning

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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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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“…XMM-Newton has proven to be the best observatory, currently operating, to identify periodic signals on the timescales exhibited by CVs (minutes -hours) and to characterize their spectral properties (see e.g. Bernardini et al 2012Bernardini et al , 2013. In Section 2 we present the XMM-Newton data complemented with the Swift BAT data.…”

Section: Introductionmentioning

confidence: 99%

Swift J2218.4+1925: a new hard-X-ray-selected polar observed with XMM–Newton

Bernardini

Martino

Mukai

et al. 2014

Monthly Notices of the Royal Astronomical Society

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Swift J2218.4+1925, a hard X-ray source detected by Swift BAT, has been proposed as a candidate magnetic cataclysmic variable of the polar type from optical spectroscopy. Using XMM-Newton we perform detailed timing and spectral analysis with simultaneous X-ray (0.3 − 10 keV) and optical B band data. We complement the spectral study with archival hard X-ray (14 − 70 keV) spectra collected by Swift BAT as well as with optical, near and mid-infrared photometry from SDSS, 2M ASS and W ISE archive, respectively. A strong periodic X-ray signal at 2.16 h, fully consistent with the recently determined spectroscopic orbital period, adds Swift J2218.4+1925 to the small group of hard X-ray polars and locates it at the low edge of the orbital period gap. The X-ray pulse profile shows the typical bright and faint phases seen in polars, that last ∼ 70% and ∼ 30% of the orbit, respectively. A pronounced dip centred on the bright phase is also detected. It is stronger at lower energies and is mainly produced by photoelectric absorption. A binary inclination i ∼ 40 o − 50 o and a magnetic colatitude β ∼ 55 o − 64 o are estimated. The source appears to accrete over a large area ∼ 24 o wide. A multi-temperature optically thin emission with complex absorption well describes the broad-band (0.3 − 70 keV) spectrum, with no signs of a soft X-ray blackbody component. The spectral shape strongly varies with the source rotation reaching plasma temperatures up to 55 keV, hardening at the dip and being softer during the faint phase (∼ 7 keV). We also find the first indication of an absorption edge due to a warm absorber in a polar. Indication of overabundance of neon is found in the RGS spectra. The UV to mid-IR spectral energy distribution reveals an excess in the near and mid-IR, likely due to low cyclotron harmonics. We further estimate a WD mass of 0.97 M ⊙ and a distance of 230 − 250 pc.

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On the nature of the hard X-ray sources SWIFT J1907.3−2050, IGR J12123−5802 and IGR J19552+0044

Cited by 34 publications

References 69 publications

IGR J19552+0044: A new asynchronous short period polar

IGR J19552+0044: A new asynchronous short period 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 J2218.4+1925: a new hard-X-ray-selected polar observed with XMM–Newton

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