相关论文: Through Andromeda and Beyond: AGN Optical Transien…

We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing). We present a subset of four short timescale, high signal-to-noise microlensing candidates found by imposing severe selection criteria: the…

AgapeZ1 is the brightest and the shortest duration microlensing candidate event found in the Agape data. It occured only 42" from the center of M31. Our photometry shows that the half intensity duration of the event6 is 4.8 days and at…

We report the serendipitous detection of a very bright, very nearby microlensing event. In late October 2006, an otherwise unremarkable A0 star at a distance ~1 kpc (GSC 3656-1328) brightened achromatically by a factor of nearly 40 over the…

M31-2015-LRN is a likely stellar merger discovered in the Andromeda Galaxy in 2015. We present new optical to mid-infrared photometry and optical spectroscopy for this event. Archival data shows that the source started to brighten $\sim$2…

We present the first M31 candidate microlensing events from the Microlensing Exploration of the Galaxy and Andromeda (MEGA) survey. MEGA uses several telescopes to detect microlensing towards the nearby Andromeda galaxy, M31, in order to…

We report the final analysis of a search for microlensing events in the direction of the Andromeda galaxy, which aimed to probe the MACHO composition of the M31 halo using data collected during the 1998-99 observational campaign at the MDM…

We provide a set of microlensing event rate maps for M31, the Andromeda Galaxy. Rates for M31 microlensing were calculated on the basis of a four component model of the lens and source populations: disk and bulge sources lensed by bulge,…

We report results from intensive monitoring of two fields on either side of M31,emphasizing microlensing involving stars and masses in M31. These results stem from the three-year VATT/Columbia survey of variability on 3d to 2m timescales.…

We describe the results of a search for microlensing events affecting stars in the outer bulge and inner disk of M31, due both to masses in M31 and the Galaxy. These observations, from 1994 and 1995 on the Vatican Advanced Technology…

We present results of a microlensing survey toward the Andromeda Galaxy (M31) carried out during four observing seasons at the Isaac Newton Telescope (INT). This survey is part of the larger microlensing survey toward M31 performed by the…

We study three transient X-ray sources, that were bright in the central region of M31 galaxy in the year 2000. Observations with Chandra and XMM-Newton allowed us for the first time in the history of X-ray astronomy, to build light curves…

The rare case of changing-look (CL) AGNs, with the appearance or disappearance of broad Balmer emission lines within a few years, challenges our understanding of the AGN unified model. We present a sample of 21 new CL AGNs at $0.08<z<0.58$,…

We analyze four extreme active galactic nuclei (AGN) transients to explore the possibility that they are caused by rare, high-amplitude microlensing events. These previously unknown type-I AGN are located in the redshift range 0.6-1.1 and…

The photometric evolution of M31-RV has been investigated on 1447 plates of the Andromeda galaxy obtained over half a century with the Asiago telescopes. M31-RV is a gigantic stellar explosion that occurred during 1988 in the Bulge of M31…

We identify an object previously thought to be a star in the disk of M31, J0045+41, as a background $z\approx0.215$ AGN seen through a low-absorption region of M31. We present moderate resolution spectroscopy of J0045+41 obtained using GMOS…

We consider the feasibility of directly observing gravitational microlensing in extra-galactic sources, whose stars are not generally resolved. This precludes use of the simple optical depth to microlensing formulation, which is applicable…

We announce the discovery of a quasar behind the disk of M31, which was previously classified as a remarkable nova in our neighbour galaxy. The paper is primarily aimed at the outburst of J004457+4123 (Sharov 21), with the first part…

We report the discovery of a short-duration microlensing candidate in the northern field of the POINT-AGAPE pixel lensing survey towards M31. The full-width half-maximum timescale is very short, just 1.8 days. Almost certainly, the source…

We present a 10-year X-ray light curve and the spectra of a peculiar X-ray transient in the spiral galaxy M81. The source was below the detection limit of ROSAT PSPC before 1993, but it brightened substantially in 1993, with luminosities…

We re-analyze the M31 microlensing event WeCAPP-GL1/Point-AGAPE-S3 taking into account that stars are not point-like but extended. We show that the finite size of stars can dramatically change the self-lensing eventrate and (less…