Broad-band characteristics of seven new hard X-ray selected cataclysmic variables

F. Bernardini, D. de Martino, K. Mukai, Dave Russell, M. Falanga, N. Masetti, C. Ferrigno, G. Israel

Research output: Contribution to journalArticle

Abstract

We present timing and spectral analysis of a sample of seven hard X-ray selected cataclysmic variable candidates based on simultaneous X-ray and optical observations collected with XMM-Newton, complemented with Swift/BAT and INTEGRAL /IBIS hard X-ray data and ground-based optical photometry. For six sources, X-ray pulsations are detected for the first time in the range of ∼296-6098 s, identifying them as members of the magnetic class. Swift J0927.7-6945, Swift J0958.0-4208, Swift J1701.3-4304, Swift J2113.5+5422 and ossibly PBC J0801.2-4625 are intermediate polars (IPs), while Swift J0706.8+0325 is a short (1.7 h) orbital period polar, the 11th hard X-ray-selected identified so far. X-ray orbital modulation is also observed in Swift J0927.7-6945 (5.2 h) and Swift J2113.5+5422 (4.1 h). Swift J1701.3-4304 is discovered as the longest orbital period (12.8 h) deep eclipsing IP. The spectra of the magnetic systems reveal optically thin multitemperature emission between 0.2 and 60 keV. Energy-dependent spin pulses and the orbital modulation in Swift J0927.7-6945 and Swift J2113.5+5422 are due to intervening local high-density absorbing material (NH ∼ 1022 - 23 cm-2). In Swift J0958.0-4208 and Swift J1701.3-4304, a soft X-ray blackbody (kT ∼ 50 and ∼80 eV) is detected, adding them to the growing group of 'soft' IPs. White dwarf masses are determined in the range of ∼0.58-1.18M⊙, indicating massive accreting primaries in five of them. Most sources accrete at rates lower than the expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h) nova-like CV, Swift J0746.3-1608 shows peculiar spectrum and light curves suggesting either an atypical low-luminosity CV or a low-mass X-ray binary.

Original languageEnglish (US)
Pages (from-to)4815-4837
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume470
Issue number4
DOIs
Publication statusPublished - Oct 1 2017

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Keywords

  • 1608 (aka 1RXS J074616.8-161127)
  • 4304 (aka IGR J17014-4306)
  • 462324)
  • 4625 (aka 1RXS J080114.6
  • 6945
  • Novae, Cataclysmic variables
  • White dwarfs
  • X-rays: binaries
  • X-rays: individual: PBC J0801.2
  • X-rays: individual: Swift J0706.8+0325
  • X-rays: individual: Swift J0746.3
  • X-rays: individual: Swift J0927.7
  • X-rays: individual: Swift J0958.0-4208
  • X-rays: individual: Swift J1701.3
  • X-rays: individual: Swift J2113.5+5422

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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