2,147 research outputs found
A systematic search for novae in M31 on a large set of digitized archival Schmidt plates
This paper reports on the detection of optical novae in our neighbour galaxy
M31 based on digitized historical Tautenburg Schmidt plates. The accurate
positions of the detected novae lead to a much larger database when searching
for recurrent novae in M31. We conducted a systematic search for novae on 306
digitized Tautenburg Schmidt plates covering a time span of 36 years from 1960
to 1996. From the database of both ~ 300 000 light curves and about one million
detections on only one plate per colour band, nova candidates were efficiently
selected by automated algorithms and subsequently individually inspected by
eye. We report the detection of 84 nova candidates. We found 55 nova candidates
from the automated analysis of the light curves. Among these, 22 were
previously unknown, 12 were known but not identified on Tautenburg Schmidt
plates before, and 21 novae had been previously discovered on Tautenburg
plates. An additional 29 known novae could be confirmed by the detailed
investigation of single detections. One of our newly discovered nova candidates
shows a high position coincidence with a nova detected about 30 years earlier.
Therefore, this object is likely to be a recurrent nova. Furthermore, we
re-investigated all 41 nova candidates previously found on Tautenburg plates
and confirm all but two. Positions are given for all nova candidates with a
typical accuracy of ~ 0.4 arcsec. We present light curves and finding charts as
online material. The analysis of the plates has shown the wealth of information
still buried in old plate archives. Extrapolating from this survey,
digitization of other historical M31 plate archives (e.g. from the Mount Wilson
or Asiago observatories) for a systematic nova search looks very promising.Comment: 29 pages, 14 figures, 19 tables, accepted for publication in A&A.
Figs 6-14 are reduced in resolution due to the restrictions on space
available on astro-ph; v2: minor grammatical change
A remarkable recurrent nova in M 31: The 2010 eruption recovered and evidence of a six-month period
The Andromeda Galaxy recurrent nova M31N 2008-12a has been caught in eruption
nine times. Six observed eruptions in the seven years from 2008 to 2014
suggested a duty cycle of ~1 year, which makes this the most rapidly recurring
system known and the leading single-degenerate Type Ia Supernova progenitor
candidate; but no 2010 eruption has been found so far. Here we present evidence
supporting the recovery of the 2010 eruption, based on archival images taken at
and around the time. We detect the 2010 eruption in a pair of images at 2010
Nov 20.52 UT, with a magnitude of m_R = 17.84 +/- 0.19. The sequence of seven
eruptions shows significant indications of a duty cycle slightly shorter than
one year, which makes successive eruptions occur progressively earlier in the
year. We compared three archival X-ray detections with the well observed
multi-wavelength light curve of the 2014 eruption to accurately constrain the
time of their optical peaks. The results imply that M31N 2008-12a might have in
fact a recurrence period of ~6 months (175 +/- 11 days), making it even more
exceptional. If this is the case, then we predict that soon two eruptions per
year will be observable. Furthermore, we predict the next eruption will occur
around late Sep 2015. We encourage additional observations.Comment: 4 pages, 3 figures, 2 tables; submitted to A&A Letter
Multiwavelength observations of the 2015 nova in the Local Group irregular dwarf galaxy IC 1613
A nova in the Local Group irregular dwarf galaxy IC 1613 was discovered on 2015 September 10 and is the first nova in that galaxy to be spectroscopically confirmed. We conducted a detailed multi-wavelength observing campaign of the eruption with the Liverpool Telescope, the LCO 2m telescope at Siding Spring Observatory, and Swift, the results of which we present here. The nova peaked at and was fast-fading, with decline times of and days. The overall light curve decline was relatively smooth, as often seen in fast-fading novae. Swift observations spanned 40 days to 332 days post-discovery, but no X-ray source was detected. Optical spectra show the nova to be a member of the hybrid spectroscopic class, simultaneously showing Fe II and N II lines of similar strength during the early decline phase. The spectra cover the eruption from the early optically thick phase, through the early decline and into the nebular phase. The H absorption minimum from the optically thick spectrum indicates an expansion velocity of km s. The FWHM of the H emission line between 10.54 and 57.51 days post-discovery shows no significant evolution and remains at km s, although the morphology of this line does show some evolution. The nova appears close to a faint stellar source in archival imaging, however we find the most likely explanation for this is simply a chance alignment
CXOM31 J004253.1+411422: The first ultra-luminous X-ray transient in M 31
We seek clarification of the nature of X-ray sources detected in M 31. Here
we focus on CXOM31 J004253.1+411422, the brightness of which suggests that it
belongs to the class of ultraluminous X-ray sources. We determine the X-ray
properties of sources detected in the XMM-Newton Chandra monitoring program. We
investigate spectral properties and search for periodic or quasi-periodic
oscillations. A multi-component model is applied to the spectra obtained from
XMM-Newton data to evaluate the relative contributions from thermal and
non-thermal emission. The time dependence of this ratio is evaluated over a
period of forty days. We simultaneously fit data from XMM-Newton EPIC-pn, MOS1
and MOS2 detectors with (non-thermal) powerlaw and (thermal) multicolored
blackbody. The X-ray spectrum is best fit by the combination of a thermal
component with kT ~ 1 keV and a powerlaw component with photon index
approximately 2.6. From combined analysis of Chandra, Swift and XMM-Newton
data, the unabsorbed total luminosity of this source decreases from ~ 3.8 x
10^{39} erg s^{-1} in the first observation to ~ 0.5 x 10^{39} ergs s^{-1} over
a period of three months. The decay closely follows an exponential decline with
a time constant of 32 days. The source spectrum evolves significantly,
exhibiting a faster decline of the thermal component. We do not find evidence
of any significant temporal features in the power density spectrum. The
presence of a thermal component at kT ~ 1 keV in conjunction with a non-thermal
high energy tail, is also consistent with spectral properties of other ULXs in
the "high state". Our analysis indicates that the underlying source of this
first ULX in M~31 is a black hole of mass, M > 13 M_{sun}, accreting near the
Eddington limit, that underwent a transient outburst followed by an exponential
decay reminiscent of transients associated with galactic X-ray novae.Comment: Accepted by Astronomy and Astrophysics. 6 pages, 8 figure
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