ﻻ يوجد ملخص باللغة العربية
We investigate the relationship between the IR observed properties of the EXor variables and the mechanisms active during their evolutionary stage. To this aim, we have constructed a catalog of all the IR (1-100 micron) photometric and spectroscopic observations appearing during the last 30 years in the literature. New results of our monitoring program based on near- and mid-IR photometry and near-IR spectroscopy and polarimetry of one object (V1118 Ori) are presented, complementing those given in a previous paper and related to a different activity period. Our catalog indicates how the database accumulated so far is inadequate for any statistical study of the EXor events. Nevertheless, all the observational evidence can be interpreted into a coherent scheme. The sources that present the largest brightness variations tend to become bluer while brightening. The scenario of disk accretion based on viscous friction between particles agrees with the observations. The new results on V1118 Ori confirm such a general view. The striking novelty is represented by a near-IR spectrum of V1118 Ori taken 1 yr after the last monitored outburst: any emission line previously detected has now totally disappeared at our sensitivity. For the same source, mid-IR photometry is provided here for the first time and allows us to construct a meaningful SED. The first polarimetric data show that V1118 Ori is intrinsically polarized and its spotted, magnetized surface becomes recognizable during the less active phases.
After a quiescence period of about 10 years, the classical EXor source V1118 Ori has undergone an accretion outburst in 2015 September. The maximum brightness (DV > 4 mag) was reached in 2015 December and was maintained for several months. Since 2016
EXor objects are young variables that show episodic variations of brightness commonly associated to enhanced accretion outbursts. With the aim of investigating the long-term photometric behaviour of a few EXor sources, we present here data from the a
We present a near-IR study of the EXor variable V1118 Ori, performed by following a slightly declining phase after a recent outburst. In particular, the near-IR (0.8 - 2.3 micron) spectrum, obtained for the first time, shows a large variety of emissi
As part of an ALMA survey to study the origin of episodic accretion in young eruptive variables, we have observed the circumstellar environment of the star V2775 Ori. This object is a very young, pre-main sequence object which displays a large amplit
We present Atacama Large Millimeter/ sub-millimeter Array (ALMA) observations of V883 Ori, an FU Ori object. We describe the molecular outflow and envelope of the system based on the $^{12}$CO and $^{13}$CO emissions, which together trace a bipolar m