NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
A ~60 day Super-orbital Period Originating from the Ultraluminous X-ray Pulsar in M82Ultraluminous X-ray (ULX) pulsars are a new class of object powered by apparent super-critical accretion onto magnetized neutron stars. Three sources in this class have been identified so far; M82X-2, NGC 5907 ULX-1, and NGC 7793 P13 have been found to have two properties in common; ∼1 s spin periods, and for NGC 5907 ULX-1 and NGC 7793 P13 periodic X-ray flux modulations on timescales of ∼60–80 days. M82 X-2 resides in a crowded field that includes the ULX M82 X-1 separated from X-2 by 5″, as well as other bright point sources. A 60 day modulation has been observed from the region, but the origin has been difficult to identify; both M82 X-1 and X-2
have been suggested as the source. In this paper we present the analysis of a systematic monitoring campaign by Chandra, the only X-ray telescope capable of resolving the crowded field. From a simple Lomb–Scargle periodogram analysis and a more sophisticated Gaussian Process analysis we find that only X-2 exhibits a periodic signal around 60 days, supporting previous claims that it is the origin. We also construct a phase-averaged flux profile of the modulations from higher-cadence Swift/XRT data and find that the flux variations in the Chandra data are fully consistent with the flux profile. Since the orbit of the neutron star and its companion is known to be 2.5 days, the ∼60 day period must be super-orbital in origin. The flux of the modulations varies by a factor of ∼100 from the minimum to the maximum, with no evidence for spectral variations, making the origin difficult to explain.
Document ID
20210013216
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Murray Brightman
(California Institute of Technology Pasadena, California, United States)
Fiona A Harrison
(California Institute of Technology Pasadena, California, United States)
Matteo Bachetti
(California Institute of Technology Pasadena, California, United States)
Yanjun Xu
(California Institute of Technology Pasadena, California, United States)
Felix Fürst ORCID
(European Space Astronomy Centre Madrid, Spain)
Dominic J. Walton
(Institute of Astronomy Cambridge, United Kingdom)
Andrew Francis Ptak
(Goddard Space Flight Center Greenbelt, Maryland, United States)
Mihoko Yukita
(Johns Hopkins University Baltimore, Maryland, United States)
Andreas Zezas
(University of Crete Rethymno, Greece)
Date Acquired
April 6, 2021
Publication Date
March 10, 2019
Publication Information
Publication: Astrophysical Journal
Publisher: American Astronomical Society
Volume: 873
Issue: 2
Issue Publication Date: March 10, 2019
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Astronomy
Funding Number(s)
WBS: 399131
Distribution Limits
Public
Copyright
Portions of document may include copyright protected material.
Technical Review
External Peer Committee
Keywords
Individual galaxies
Neutron stars
Binary X-rays
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available