We present results from an ongoing Keck spectroscopic survey of red giant stars in a field located along the major axis of M31, ≈ 34 kpc in projection from the nucleus and near the luminous globular cluster G1. We use multislit LRIS spectroscopy to measure the Ca ii nearinfrared triplet in 41 stars ranging in apparent magnitude from 20 < I < 22. Of these, 23 stars are found to have radial veloc...

The MEGA microlensing survey is introduced and several topics about variable stars in M31 are discussed. An adopted model population of semiregular (SR) variable stars is presented, and the efficiency to recover these stars in M31 in a specific example MEGA dataset is predicted. The period-flux amplitude relation of the SRs discovered by MEGA could be used to measure the inclination of the M31 ...

We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named Guoshoujing Telescope) during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey (SDSS), Kitt Peak National Observatory (KPNO) 4 m telescope, Xuyi Sch...

The most conspicuous feature of the large-scale magnetic field in the Andromeda nebula (M31) is a magnetic belt centred at a galacto-centric radius of about 10 kpc. We suggest a nonlinear dynamo model for M31, which associates this belt with the gas density profile as well as with the kinematic parameters of M31. Our model is based on the observed density profile and vertical structure of the g...

The highly anisotropic distribution and apparent alignment of the Galactic satellites in polar great planes begs the question how common such distributions are. The satellite system of M31 is the only nearby system for which we currently have sufficiently accurate distances to study the three-dimensional satellite distribution. We present the spatial distribution of the 15 presently known M31 c...

The 1991 ROSAT PSPC M31 X-ray point source catalog has been screened in order to set up a sample of candidate supersoft sources in this galaxy, additional to the 16 supersoft sources already known in M31 (Supper et al. 1997). Selection criteria used were based on hardness ratios (“X-ray colors”), as developed in an earlier paper (Kahabka 1998). An additional criterion to be fulfilled was that t...

We present deep (V ≃ 27) V and I -band stellar photometry obtained using the Hubble Space Telescope’s WFPC2 in two fields in the M31 halo. These fields are located 32 and 50 from the center of M31 approximately along the SE minor axis at the locations of the M31 globular star clusters G302 and G312 respectively. The M31 halo luminosity functions are not consistent with a single high-metallicity...

The lightcurve of PA-99-N2, one of the recently announced microlensing candidates towards M31, shows small deviations from the standard Paczyński form. We explore a number of possible explanations, including correlations with the seeing, the parallax effect and a binary lens. We find that the observations are consistent with an unresolved RGB or AGB star in M31 being microlensed by a binary len...

The hypothesized supermassive black hole in the nucleus of M31 (which we shall hereafter call M31*) has many features in common with Sgr A* at the Galactic Center, yet they differ in several significant and important ways. Though M31* is probably ten times heavier, its radio luminosity at 3.6 cm is only one third that of Sgr A*. At the same time, M31* is apparently thousands of times more lumin...

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 Telescope and KPNO 4m, are sufficient to rule out masses in the range of ∼ 0.003 M⊙ to 0.08 M⊙ as the primary consistuents of the mass of M31 towards this field. F...