<i>SUZAKU</i>
                    DETECTION OF SUPERHARD X-RAY EMISSION FROM THE CLASSICAL NOVA V2491 CYGNI

Takei, Dai; Tsujimoto, Masahiro; Kitamoto, Shunji; Ness, J. U.; Drake, J. J.; Takahashi, H.; Mukai, K.

doi:10.1088/0004-637x/697/1/l54

Cited by 30 publications

(40 citation statements)

References 33 publications

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“…In the latter case, any accompanying radioactive decay emission will depend on ejecta mass and ejecta velocity for a given white dwarf mass (Hernanz et al 2002), which can be different for each subsequent outburst. Previous observations of emission up to 70 keV with Suzaku (Takei et al 2009) and the likely ∼0.1 MeV Compton/ OSSE detection of V382 Vel 1999 (Cheung et al 2015c) suggest extended timescale emission in classical novae and should motivate continuum emission searches with INTEGRAL (Winkler et al 2003) and ASTRO-H (Takahashi et al 2012;Coppi et al 2014) at later times than so far considered for the nuclear decay emission.…”

Section: Discussionmentioning

confidence: 80%

Fermi-Lat Gamma-Ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015

Cheung

Jean

Shore

et al. 2016

ApJ

108

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We report the Fermi Large Area Telescope (LAT) detections of high-energy (>100 MeV) γ-ray emission from two recent optically bright classical novae, V1369 Centauri 2013 and V5668 Sagittarii 2015. At early times, Fermi target-of-opportunity observations prompted by their optical discoveries provided enhanced LAT exposure that enabled the detections of γ-ray onsets beginning ∼2 days after their first optical peaks. Significant γ-ray emission was found extending to 39-55 days after their initial LAT detections, with systematically fainter and longerduration emission compared to previous γ-ray-detected classical novae. These novae were distinguished by multiple bright optical peaks that encompassed the time spans of the observed γ-rays. The γ-ray light curves and spectra of the two novae are presented along with representative hadronic and leptonic models, and comparisons with other novae detected by the LAT are discussed.

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Section: Discussionmentioning

confidence: 80%

Fermi-Lat Gamma-Ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015

Cheung

Jean

Shore

et al. 2016

ApJ

108

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“…The only other nova to have been detected in the X-rays before the outburst was Nova Oph 1998 (=V2487 Oph, Hernanz and Sala, 2002). This contributed to trigger a tight X-ray monitoring of the outburst evolution, which results are described by Page et al, (2008Page et al, ( , 2010; Osborne et al, (2008); Ness et al, (2008a,b); Kuulkers et al (2008); Takei et al, (2009) ;Takei & Ness (2010). NOph08-2 displayed initially a hard X-ray spectrum originating from shocked gas, while a much brighter and softer X-ray spectrum emerged later.…”

Section: Introductionmentioning

confidence: 84%

An extensive optical study of V2491 Cyg (Nova Cyg 2008 N.2), from maximum brightness to return to quiescence

Munari

Siviero

Dallaporta³

et al. 2011

New Astronomy

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The photometric and spectroscopic evolution of the He/N and very fast Nova Cyg 2008 N2 (V2491 Cyg) is studied in detail. A primary maximum was reached at V=7.45±0.05 on April 11.37 (±0.1) 2008 UT, followed by a smooth decline characterized by t V 2 =4.8 days, and then a second maximum was attained at V=9.49±0.03, 14.5 days after the primary one. This is the only third nova to have displayed a secondary maximum, after V2362 Cyg and V1493 Aql. The development and energetics of the secondary maximum is studied in detail. The smooth decline that followed was accurately monitored until day +144 when the nova was 8.6 mag fainter than maximum brightness, well into its nebular phase, with its line and continuum emissivity declining as t −3 . The reddening affecting the nova was E B−V =0.23±0.01, and the distance of 14 kpc places the nova at a height above the galactic plane of 1.1 kpc, larger than typical for He/N novae. The expansion velocity of the bulk of ejecta was 2000 km/sec, with complex emission profiles and weak P-Cyg absorptions during the optically thick phase, and saddle-like profiles during the nebular phase. Photo-ionization analysis of the emission line spectrum indicates that the mass ejected by the outburst was 5.3 10 −6 M ⊙ and the mass fractions to be X=0.573, Y=0.287, Z=0.140, with those of individual elements being N=0.074, O=0.049, Ne=0.015. The metallicity of the accreted material was [Fe/H]=−0.25, in line with ambient value at the nova galacto-centric distance. Additional spectroscopic and photometric observations at days +477 and +831 show the nova returned to the brightness level of the progenitor and to have resumed the accretion onto the white dwarf.

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“…With the small extinction E(B − V ) 0.2 (43, 47, 48), the absolute magnitude is 3.5 mag making this unlikely a red giant. We obtained V -band magnitudes from the American Association of Variable Star Observers (AAVSO) 6 (49), averaged them in 0.25 day bins, and these are plotted along with the γ-ray light curves (Fig. S6).…”

Section: V339 Del 2013mentioning

confidence: 99%

“…radioactive decay at ∼MeV energies that remain undetected in individual novae (5) and < ∼ 0.1 MeV emission detected in isolated cases (6).…”

mentioning

confidence: 99%

Fermi establishes classical novae as a distinct class of gamma-ray sources

Ackermann

Ajello

Albert

et al. 2014

Science

168

102

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A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in γ rays and stood in contrast to the first γ-ray detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft spectrum transient γ-ray sources detected over 2−3 week durations. The γ-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic γ-ray sources.The Fermi-LAT [Large Area Telescope; (1)], launched in 2008, continuously scans the sky in γ rays, thus enabling searches for transient sources. When a nova explodes in a symbiotic binary system, the ejecta from the white dwarf surface expand within the circumstellar wind of the red giant companion and high-energy particles can be accelerated in a blast wave driven in the high-density environment (2) so that variable γ-ray emission can be produced, as was detected at >100 MeV energies by the LAT in V407 Cygni 2010 (V407 Cyg) (3). In a classical nova, by contrast, the ejecta quickly expand beyond the confines of the compact binary into a much lower density environment. High-energy particle acceleration could therefore be related to a bow shock driven by the ejecta in the interstellar medium, or to turbulence and eventually weaker internal shocks formed in the inhomogeneous ejecta itself. The contribution of such expanding nova shells to cosmic-ray acceleration had been considered (4), but no predictions have so far been made for >100 MeV γ-rays. The classical novae (or simply "novae" where appropriate) detected by the LAT with 12−20σ significances (Table 1, Fig. 1) -V959 Monocerotis 2012 (V959 Mon), V1324 Scorpii 2012 (V1324 Sco), and V339 Delphini 2013 (V339 Del) -were unanticipated. These observed γ rays have higher energies than nuclear line emission by * All authors with their affiliations appear at the end of this paper. †To whom correspondence should be addressed. E-mail: Teddy.Cheung@nrl.navy.mil (C. C. Cheung); E-mail: Pierre.Jean@irap.omp.eu (P. Jean); E-mail: shore@df.unipi.it (S. N. Shore) 1 arXiv:1408.0735v1 [astro-ph.HE] 4 Aug 2014 radioactive decay at ∼MeV energies that remain undetected in individual novae (5) and < ∼ 0.1 MeV emission detected in isolated cases (6).V959 Mon was detected as a transient γ-ray source in June 2012 by the LAT while close (∼ 20• separation) to the Sun (7) and then optically in August (8). Ultraviolet spectroscopy revealed an oxygen-neon nova (9), recognized as the class with the most massive white dwarfs ( > ∼ 1.1 M ) with massive ( > ∼ 8 M ) progenitors [e.g., (10)]. The expected peak visual magnitude of ∼5 would have been observable with the naked eye ∼50 days earlier, when the γ-ray transient was detected (9). V339 D...

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SUZAKU DETECTION OF SUPERHARD X-RAY EMISSION FROM THE CLASSICAL NOVA V2491 CYGNI

Cited by 30 publications

References 33 publications

Fermi-Lat Gamma-Ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015

Fermi-Lat Gamma-Ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015

An extensive optical study of V2491 Cyg (Nova Cyg 2008 N.2), from maximum brightness to return to quiescence

Fermi establishes classical novae as a distinct class of gamma-ray sources

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