相关论文: Through Andromeda and Beyond: AGN Optical Transien…
Infrared observations of complete samples of active galactic nuclei (AGN) have shown that a substantial fraction of their bolometric luminosity is emitted at wavelengths ~8-1000microns. In radio-loud and Blazar-like objects much of this…
For the past five seasons, the Angstrom Project, an international microlensing collaboration, has been making observations of the central bulge of M31, the Andromeda galaxy, searching for microlensing events. This thesis describes the work…
Obscured active galactic nuclei (AGNs) are thought to be very common in the Universe. Observations and surveys have shown that the number of sources increases for near galaxies and at the low-luminosity regime (the so-called LLAGNs).…
We analyze PLANET and MACHO observations of MACHO 99-BLG-47, the first nearly-normal microlensing event for which high signal-to-noise-ratio data reveal a well-covered, short-duration anomaly. This anomaly occurs near the the peak of the…
E+A galaxies are believed to be a short phase connecting major merger ULIRGs with red and dead elliptical galaxies. Their optical spectrum suggests a massive starburst that was quenched abruptly, and their bulge-dominated morphologies with…
Microlensing events provide a unique capacity to study the stellar remnant population of the Galaxy. Optical microlensing suffers from a near complete degeneracy between the mass, the velocity and the distance. However, a subpopulation of…
We investigate the data collected by the high-cadence microlensing surveys during the 2022 season in search for planetary signals appearing in the light curves of microlensing events. From this search, we find that the lensing event…
We report the discovery of a microlensing candidate projected 2'54" from the center of M32, on the side closest to M31. The blue color (R-I= 0.00 +/- 0.14) of the source argues strongly that it lies in the disk of M31, while the proximity…
As part of a multi-wavelength campaign to observe the 2000--2002 outburst of the prototypical symbiotic star Z Andromedae, we observed this object six times each with the Multi-Element Radio Linked Interferometer Network (MERLIN) and Very…
Sensitive high angular resolution ($\sim$ 2$"$) CO(2-1) line observations made with the Submillimeter Array (SMA) of the flow emanating from the high-mass star forming region DR21 located in the Cygnus X molecular cloud are presented. These…
We re-analyze brightness data sampled intensively over 5 nights at two epochs separated by the quasar lens time delay, to examine the nature of the observed microlensing. We find strong evidence for a microlensing event with an amplitude of…
The microlensing interpretation of the optical afterglow of GRB 000301C seems naively surprising, since a simple estimate of the stellar microlensing rate gives less than one in four hundred for a flat Omega_Lambda=0.7 cosmology, whereas…
We present new horizontal branch (HB) distance measurements to 17 of the faintest known M31 satellites ($-6 \lesssim M_{V} \lesssim -13$) based on deep Hubble Space Telescope (HST) imaging. The color-magnitude diagrams extend $\sim$1-2…
Ultraluminous X-Ray Objects are off-nucleus point sources with $L_X=10^{39}$-$10^{41}$ erg/s and are among the most poorly understood X-ray sources. To help understand their nature, we are trying to identify their optical counterparts by…
In the last decade of Active Galactic Nuclei (AGN) monitoring programs, the Mets\"ahovi Radio Observatory detected multiple times seven powerful flaring narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz. Several hypotheses have been proposed,…
Variable A in M33 is a member of a rare class of highly luminous, evolved stars near the upper luminosity boundary that show sudden and dramatic shifts in apparent temperature due to the formation of optically thick winds in high mass loss…
Positron annihilation line at 511~keV is a known component of the gamma-ray diffuse emission. It is believed to be produced in the Galaxy, but there could be possible extragalactic contribution as well. E.g., positrons can be produced in…
We present integral field unit (IFU) observations covering the [O III]4959,5007 and H-Beta emission lines of sixteen z<0.2 type 2 active galactic nuclei (AGN). Our targets are selected from a well-constrained parent sample of 24,000 AGN so…
The Sloan Digital Sky Survey has revealed an overdensity of luminous red giant stars ~ 3 degrees (40 projected kpc) to the northeast of M31, which we have called Andromeda NE. The line-of-sight distance to Andromeda NE is within…
We present a comprehensive treatment of the pixel-lensing theory and apply it to lensing experiments and their results toward M31. Using distribution functions for the distances, velocities, masses, and luminosities of stars, we derive…