We have been regularly observing the bulge and inner disk of M31 for nearly 1 year, using both the HRC-I and ACIS-I instruments on the Chandra X-Ray Observatory. We present results from our program that are of interest to the study of the ISM in M31. In particular, we find that the unresolved emission within 3 of the center of M31 has a distinctly softer spectrum than that of most of the resolv...

We use data from the Isaac Newton Telescope Wide Field Camera survey of M31 to determine the surface brightness profile of M31 along the south-east minor axis. We combine surface photometry and faint red giant branch star counts to trace the profile from the innermost regions out to a projected radius of 4 (≈ 55 kpc) where μV ∼ 32 mag arcsec ; this is the first time the M31 minor axis profile h...

We report new, as yet unpublished HST/WFPC2 V, I pho-tometry of 9 globular clusters in M31. These are part of a total sample of 19 clusters on M31 with well observed CMDs from HST. The clusters have the full range of horizontal branch morphologies from blue HB to red clump, but none are found with an extreme (blue only) horizontal branch. Plots of HB type vs [Fe/H] are similar to those of Galac...

The Andromeda Galaxy (M31) has been observed with the UltraViolet Imaging Telescope (UVIT) instrument onboard AstroSat Observatory. M31 sky area was covered 19 fields, in multiple UV filters per field, over period of 2017 to 2019. entire galaxy FUV F148W filter, and more than half NUV filters. A new calibration data processing is described which improves astrometry photometry UVIT data. high sp...

The star formation history of the northern and southern M31 disk is measured using samples of BV photometry for 4’ × 4’ regions taken from the KPNO/CTIO Local Group Survey (Massey et al. 2001). The distances, mean reddening values, and age distributions of the stars in these regions were measured using the routines of Dolphin (1997, 2002). Independent measurements of overlapping fields show tha...

We perform an analytical study and a Monte Carlo (MC) analysis of the main features for microlensing events in pixel lensing observations towards M31. Our main aim is to investigate the lens nature and location of the 14 candidate events found by the MEGA collaboration. Assuming a reference model for the mass distribution in M31 and the standard model for our galaxy, we estimate the MACHO-to-se...

We study the possibility to detect extrasolar planets in M31 through pixel-lensing observations. Using a Monte Carlo approach, we select the physical parameters of the binary lens system, a star hosting a planet, and we calculate the pixel-lensing light curve taking into account the finite source effects. Indeed, their inclusion is crucial since the sources in M31 microlensing events are mainly...

We present results of KPNO 4-m optical spectroscopy of discrete emissionline nebulae and regions of diffuse ionized gas (DIG) in M31. Long-slit spectra of 16 positions in the NE half of M31 were obtained over a 5-15 kpc range in radial distance from the center of the galaxy with special attention to the annulus of high star formation between 8 and 12 kpc. Slit positions were chosen such that se...

I present preliminary BV resolved stellar photometry of the M31 disk measured from the data set of the NOAO/CTIO Local Group Survey. I have performed detailed analyses of the star formation histories in and around three currently active regions in the M31 disk: OB 78, OB 102 and the northeast spiral arm. The results suggest that low Hα emission from OB 78 compared to other active regions is dir...

Using ROSAT PSPC data, we have performed several tests aimed at understanding the origin of the soft X-ray spectral component detected from the bulge of M31. We find that a significant soft component in the spectrum of the bulge is spatially correlated with the unresolved X-ray emission near the core of M31, which is probably a hot interstellar medium or perhaps a population of multiple faint s...