Context. M31N 2015M31N -01a (or M31LRN 2015 is a red nova that erupted in January 2015 -the first event of this kind observed in M 31 since 1988. Very few similar events have been confirmed as of 2015. Most of them are considered to be products of stellar mergers. Aims. Results of an extensive optical monitoring of the transient in the period January-March 2015 are presented. Methods. Eight optical telescopes were used for imaging. Spectra were obtained on the Large Altazimuth Telescope (BTA), the Gran Telecsopio Canarias (GTC) and the Rozhen 2 m telescope. Results. We present a highly accurate 70 d light curve and astrometry with a 0.05 uncertainty. The colour indices reached a minimum of 2−3 d before peak brightness and rapidly increased afterwards. The spectral type changed from F5I to F0I in 6 d before the maximum and then to K3I in the next 30 d. The luminosity of the transient was estimated to be 8.7 +3.3 −2.2 × 10 5 L during the optical maximum. Conclusions. Both the photometric and the spectroscopic results confirm that the object is a red nova, similar to V838 Monocerotis.

We identify the rich carbon star population of the Magellanic-type dwarf irregular galaxy WLM (Wolf-Lundmark-Melotte) and study its photometric properties from deep near-IR observations. The galaxy also exhibits a clear presence of oxygen-rich population. We derive a carbon to M-star ratio of C/M = 0.56 ± 0.12, relatively high in comparison with many galaxies. The spatial distribution of the AGB stars in WLM hints at the presence of two stellar complexes with a size of a few hundred parsecs. Using the H i map of WLM and the derived gas-to-dust ratio for this galaxy N(H i)/E(B − V) = 60 ± 10 [10 21 at. cm −2 mag −1 ] we re-determined the distance modulus of WLM from the IR photometry of four known Cepheids, obtaining (m − M) 0 = 24.84 ± 0.14 mag. In addition, we determine the scale length of 0.75 ± 0.14 kpc of WLM disk in the J-band.

Abstract. We propose the first association of an optical counterpart with a luminous supersoft X-ray source in M31, RX J0044.0+4118, observed with ROSAT in July 1991. The PSPC position is at 1.6 angular distance from a candidate nova in outburst in September of 1990. This is interesting because the incidence of classical novae among supersoft X-ray sources is an open question. The proposed optical counterpart was measured at R 17.7 in September of 1990, and it had faded to R > 19.2 when it was observed again after 70 days. The light curve was too sparsely monitored for definite conclusions on the speed class of the nova. No other variable objects with V < 23.5 were found in the ROSAT spatial error box. We evaluate that the probability that a classical or recurrent nova was in outburst in the ROSAT error box in the few years preceding the observation is very small, so the proposed identification is meaningful. We also show evidence that the associated supersoft X-ray source turned off in the third year after the outburst.

Whiting 1 is a member of the fast-growing group of young globular clusters in the Milky Way halo. Preliminary estimates of its fundamental parameters have been provided using optical photometry and low resolution spectroscopy. In an attempt to strengthen our knowledge of Whiting 1, in this study we employ a complementary approach. Isochrone fitting method was applied on the Near-Infrared Color-Magnitude Diagram and yields an age t=5.7±0.3 Gyr, metallicity z=0.006±0.001 ([Fe/H]=−0.5±0.1) and distance modulus (m − M) 0 =17.48±0.10. Our results confirm that Whiting 1 is a young and moderately metal-rich globular cluster. It is one of the youngest from the Sgr dSph. We fitted an Elson, Fall and Freeman (EFF) profile to the near-infrared number counts, and measured cluster core radius r c =9.1 ′′ ±3.9 ′′ . Two probable eclipsing variables in the cluster were found from multi-epoch V band photometry. Finally, an unknown galaxy cluster was identified on our K vs. (J − K) color-magnitude diagram. It has a redshift z∼1, and it is located at about 1 ′ from the center of Whiting 1 at α J2000 = 02 h 02 m 56.6 s , δ J2000 = −03• 16 ′ 09 ′′ , contaminating the cluster photometry.