Aman Kaur

CXOM31 J004253.1+411422: the first ultraluminous X-ray transient in M 31

Context. We seek clarification of the nature of X-ray sources detected in Mxa031. Here we focus on CXOM31xa0J004253.1+411422, the brightness of which suggests that it belongs to the class of ultraluminous X-ray sources. Aims. 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. Methods. A multicomponent model was applied to the spectra obtained from XMM-Newton data to evaluate the relative contributions from thermal and nonthermal emission. The time dependence of this ratio was evaluated over a period of forty days. We simultaneously fit data from XMM-Newton EPIC-pn, MOS1, and MOS2 detectors with (nonthermal) powerlaw and (thermal) multicolored blackbody. Results. The X-ray spectrum is best fit by the combination of a thermal component with kT xa0~xa01xa0keV and a powerlaw component with a photon index of approximatelyxa02.6. From combined analysis of Chandra , Swift , and XMM-Newton data, the unabsorbed total luminosity of this source decreases from xa0~3.8xa0×xa010 39 xa0ergu2009s -1 in the first observation to xa0~0.5xa0×xa010 39 xa0ergu2009s -1 over a period of three months. The decay closely follows an exponential decline with a time constant of 32xa0days. 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 xa0~xa01xa0keV in conjunction with a nonthermal high-energy tail, is also consistent with spectral properties of other ULXs in the “high state”. Conclusions. Our analysis indicates that the underlying source of this first ULX in Mxa031 is a black hole of mass, M xa0≥xa013 M ⊙ , accreting near the Eddington limit, that underwent a transient outburst followed by an exponential decay reminiscent of transients associated with galactic X-ray novae.

M31N 2008-12a—THE REMARKABLE RECURRENT NOVA IN M31: PANCHROMATIC OBSERVATIONS OF THE 2015 ERUPTION

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of

Gamma-Ray-emitting Narrow-line Seyfert 1 Galaxies in the Sloan Digital Sky Survey

P_mathrm{rec}=351pm13

Breaking the Habit: The Peculiar 2016 Eruption of the Unique Recurrent Nova M31N 2008-12a

days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug.

CXO J004318.8+412016, a steady supersoft X-ray source in M 31

28.28pm0.12

New High-z BL Lacs Using the Photometric Method with Swift and SARA

UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities

Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

sim13000

Nova in M31: M31N 2011-01a

km s

Three new optical nova candidates in M 31

^{-1}

Supersoft X-ray transient leads to the discovery of the second optical nova in a M 31 globular cluster

, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is