J/A+A/682/A151 SALT spectrum of CXOU J005440.5-374320 (Sacchi+, 2024)
A soft and transient ultraluminous X-ray source with six-hour modulation in the
NGC 300 galaxy.
Sacchi A., Esposito P., de Martino D., Soria R., Israel G.L., Sander A.A.C.,
Sidoli L., Buckley D.A.H., Monageng I.M., Tiengo A., Arca Sedda M.,
Pinto C., Di Stefano R., Imbrogno M., Carleo A., Rivolta G.
<Astron. Astrophys. 682, A151 (2024)>
=2024A&A...682A.151S 2024A&A...682A.151S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; X-ray sources ; Spectra, optical
Keywords: galaxies: individual: NGC300 -
X-rays: individuals: CXOU J005440.5-374320
Abstract:
We investigate the nature of CXOU J005440.5-374320 (J0054), a peculiar
bright (∼4x1039erg/s) and soft X-ray transient in the spiral galaxy
NGC300 with a six-hour periodic flux modulation that was detected in a
2014 Chandra observation. Subsequent observations with Chandra and
XMM-Newton, as well as a large observational campaign of NGC300 and
its sources performed with the Swift Neil Gehrels Observatory, showed
that this source exhibits recurrent flaring activity: four other
outbursts were detected across 8 years of monitoring. Using data from
the Swift/UVOT archive and from the XMM-Newton/OM and Gaia
catalogues, we determined that the source is likely associated with a
bright blue optical/ultraviolet counterpart. This prompted us to
perform followup observations with the Southern African Large
Telescope in December 2019. With the multi-wavelength information at
hand, we discuss several possibilities for the nature of J0054.
Although none is able to account for the full range of the observed
peculiar features, we found that the two most promising scenarios are
a stellar-mass compact object in a binary system with a Wolf-Rayet
star companion, or the recurrent tidal stripping of a stellar object
trapped in a system with an intermediate-mass (1000M☉) black
hole.
Description:
Two spectra were acquired on December 2 and December 15, 2019
(Progr.ID: 2018-2-LSP-001), with the Southern African Large Telescope
(SALT), equipped with the Robert Stobie Spectrograph (RSS) in the
long-slit (8"x1.5") spectroscopy mode. The PG0300 and PG0900 gratings
were used for the observations with exposure times of 1800s and
2000s, respectively.
Objects:
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RA (2000) DE Designation(s)
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00 54 40.5 -37 43 20 CXOU J005440.5-374320
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectrum.dat 30 3158 SALT spectrum of CXOU J005440.5-374320
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Byte-by-byte Description of file: spectrum.dat
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda Wavelength
18- 30 F13.7 ct Counts Counts
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Acknowledgements:
Andrea Sacchi, andrea.sacchi(at)cfa.harvard.edu
(End) Patricia Vannier [CDS] 12-Feb-2024