Context. We continue to study star formation in dwarf galaxies located in nearby clusters. Aims. Known physical and chemical relations outlining the formation and evolution of dwarfs is compared in ...different environments, including the Local Volume (LV) and some nearby clusters studied previously. Methods. We used the TNG telescope for four nights in 2010 to acquire deep near-infrared imaging in K′ of 45 star forming dwarf galaxies located in the Abell 779, Abell 1367, Abell 1656 (Coma), and Abell 2151 (Hercules) clusters. Results. Surface photometry was approached based on past experience by using the sech law to account for the outer old stellar contribution plus a Gaussian component to model the inner starburst, proving the blue compact dwarf (BCD) classification of most targets. Sech central surface brightness, semimajor axis, sech, and total apparent magnitude were measured, allowing to estimate size, absolute luminosity and mass for all targets. Conclusions. The physical correlations between size, central brightness, and NIR luminosity appear to hold, but previously known linear fits break above MSK = − 19 for Abell 779, Abell 1367 and especially for Hercules, while the dwarf fundamental plane (FP) is probed by only half cluster members, suggesting harassment by the denser cluster environments. Nevertheless, the chemical relations between the oxygen abundance, luminosity, gas mass, baryonic mass, and gas fraction in a closed box model are probed by most members of the four studied clusters, and the starburst grows linearly with the K′ luminosity.
ABSTRACT
Photometric and spectroscopic data for two Low Luminosity Type IIP Supernovae (LL SNe IIP) 2020cxd and 2021aai are presented. SN 2020cxd was discovered 2 d after explosion at an absolute ...magnitude of Mr = −14.02 ± 0.21 mag, subsequently settling on a plateau which lasts for ∼120 d. Through the luminosity of the late light curve tail, we infer a synthesized 56Ni mass of (1.8 ± 0.5) × 10−3 M⊙. During the early evolutionary phases, optical spectra show a blue continuum ($T\, \gt $8000 K) with broad Balmer lines displaying a P Cygni profile, while at later phases, Ca ii, Fe ii, Sc ii, and Ba ii lines dominate the spectra. Hydrodynamical modelling of the observables yields $R\, \simeq$ 575 R⊙ for the progenitor star, with Mej = 7.5 M⊙ and $E\, \simeq$ 0.097 foe emitted during the explosion. This low-energy event originating from a low-mass progenitor star is compatible with both the explosion of a red supergiant (RSG) star and with an Electron Capture Supernova arising from a super asymptotic giant branch star. SN 2021aai reaches a maximum luminosity of Mr = −16.57 ± 0.23 mag (correcting for AV = 1.92 mag), at the end of its remarkably long plateau (∼140 d). The estimated 56Ni mass is (1.4 ± 0.5) × 10−2 M⊙. The expansion velocities are compatible with those of other LL SNe IIP (few 103 km s−1). The physical parameters obtained through hydrodynamical modelling are $R\, \simeq$ 575 R⊙, Mej = 15.5 M⊙, and E = 0.4 foe. SN 2021aai is therefore interpreted as the explosion of an RSG, with properties that bridge the class of LL SNe IIP with standard SN IIP events.
ABSTRACT
The first known asteroid with the orbit inside that of Venus is 2020 AV2. This may be the largest member of a new population of small bodies with the aphelion smaller than 0.718 au, called ...Vatiras. The surface of 2020 AV2 is being constantly modified by the high temperature, by the strong solar wind irradiation that characterizes the innermost region of the Solar system, and by high-energy micrometeorite impacts. The study of its physical properties represents an extreme test-case for the science of near-Earth asteroids. Here, we report spectroscopic observations of 2020 AV2 in the 0.5–1.5-μm wavelength interval. These were performed with the Nordic Optical Telescope and the William Herschel Telescope. Based on the obtained spectra, we classify 2020 AV2 as a Sa-type asteroid. We estimate the diameter of this Vatira to be $1.50_{-0.65}^{+1.10}$ km by considering the average albedo of A-type and S-complex asteroids ($p_V=0.23_{-0.08}^{+0.11}$), and the absolute magnitude (H = 16.40 ± 0.78 mag). The wide spectral band around 1 μm shows the signature of an olivine-rich composition. The estimated band centre BIC = 1.08 ± 0.02 μm corresponds to a ferroan olivine mineralogy similar to that of brachinite meteorites.
Context.
Dwarf elliptical galaxies (dEs) are the most abundant in the Universe. Research into these objects in connection with late-type dwarf galaxies is important for evaluating theories of dwarf ...galaxy formation and evolution.
Aims.
Our past studies (2000-2010) suggested a possible evolutionary link between early- and late-type dwarf galaxies. These results are based on deep near-infrared (NIR) surface photometry data of dwarf irregulars (dIs), blue compact dwarfs (BCDs), and a small sample of Virgo dEs. As a continuation of those works, in 2017 we embarked on a study of dEs using the same surface photometry methods, with the aim being to compare early- and late-type dwarfs based on homogeneous datasets.
Methods.
We selected 74 dEs from two different environments for which we obtained deep images. Isophotal analysis was performed on the images to obtain surface brightness profiles. The two sampled environments were the Local Volume and Virgo cluster, which provide the possibility to compare isolated evolution against evolution in crowded environments. To compare dwarf datasets homogeneously, we used the NIR
Ks
band which is known to be a better gauge of galaxy mass, with reduced extinction compared to visible bands.
Results.
In this first paper, we derive apparent physical parameters for 72 dEs from deep NIR imaging and provide preliminary fitting results of their surface brightness profiles. Two targets were undetected in the Ks images, indicating possible misclassification. Physical parameters of 16 dEs are measured for the first time and the parameters of the remaining 56 dEs are compared with the literature. We obtain a mean difference between the measured physical parameters and the results from prior studies of about 0.2″ for the galaxy center coordinates, ≈20″ for the semi-major axis, ≈0.4 mag for the total apparent magnitude, ≈0.11 for the ellipticity, and ≈14° for the position angle. We find well-fitting surface brightness profiles for the dEs using the hyperbolic secant (sech) model combined with an exponential component. Alternatively, we find good agreement with observations for a sech plus a de Vaucouleurs law.
Binary quasars are extremely rare objects, used to investigate clustering on very small scales at different redshifts. The cases where the two quasar components are gravitationally bound, known as ...physical binary quasars, can also exhibit enhanced astrophysical activity and therefore are of particular scientific interest. Here we present the serendipitous discovery of a physical pair of quasars with an angular separation of Δθ = (8.76 0.11)″. The redshifts of the two quasars are consistent within the errors and measured as z = (1.76 0.01). Under the motivated assumption that the pair does not arise from a single gravitationally lensed quasar, the resulting projected physical separation was estimated as (76 1) kpc. For both targets we detected Si iv, C iv, C iii, and Mg ii emission lines. However, the two quasars show significantly different optical colors, one being among the most reddened quasars at z > 1.5 and the other with colors consistent with typical quasar colors at the same redshift. Therefore it is ruled out that the sources are a lensed system. This is our second serendipitous discovery of a pair of two quasars with different colors, having a separation 10″, which extends the catalog of known small-separation quasar pairs.
This is the fourth data paper publishing lightcurve survey work of 52 Near Earth Asteroids (NEAs) using 10 telescopes available to the EURONEAR network between 2017 and 2020. Forty six targets were ...not observed before our runs (88% of the sample) but some of these were targeted during the same oppositions mainly by Brian Warner. We propose new periods for 20 targets (38% of the sample), confirming published data for 20 targets, while our results for 8 targets do not match published data. We secured periods for 15 targets (29% of the sample), candidate periods for 23 objects (44%), tentative periods for 11 asteroids (21%), and have derived basic information about 3 targets (6% of the sample). We calculated the lower limit of the ellipsoid shape ratios
a
/
b
for 46 NEAs (including 13 PHAs). We confirmed or suggested 4 binary objects, recommending two of them for follow-up during future dedicated campaigns.
ABSTRACT
In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in ...the BVRI bands acquired at 36 observatories around the world. In mid-2021 the source showed its historical maximum, with R = 11.14. The light curves display many episodes of intraday variability, whose amplitude increases with source brightness, in agreement with a geometrical interpretation of the long-term flux behaviour. This is also supported by the long-term spectral variability, with an almost achromatic trend with brightness. In contrast, short-term variations are found to be strongly chromatic and are ascribed to energetic processes in the jet. We also analyse the optical polarimetric behaviour, finding evidence of a strong correlation between the intrinsic fast variations in flux density and those in polarization degree, with a time delay of about 13 h. This suggests a common physical origin. The overall behaviour of the source can be interpreted as the result of two mechanisms: variability on time-scales greater than several days is likely produced by orientation effects, while either shock waves propagating in the jet, or magnetic reconnection, possibly induced by kink instabilities in the jet, can explain variability on shorter time-scales. The latter scenario could also account for the appearance of quasi-periodic oscillations, with periods from a few days to a few hours, during outbursts, when the jet is more closely aligned with our line of sight and the time-scales are shortened by relativistic effects.
We report the discovery, mass, and radius determination of TOI-1801 b, a temperate mini-Neptune around a young M dwarf. TOI-1801 b was observed in TESS sectors 22 and 49, and the alert that this was ...a TESS planet candidate with a period of 21.3 days went out in April 2020. However, ground-based follow-up observations, including seeing-limited photometry in and outside transit together with precise radial velocity (RV) measurements with CARMENES and HIRES revealed that the true period of the planet is 10.6 days. These observations also allowed us to retrieve a mass of 5.74 ± 1.46
M
⊕
, which together with a radius of 2.08 ± 0.12
R
⊕
, means that TOI-1801 b is most probably composed of water and rock, with an upper limit of 2% by mass of H
2
in its atmosphere. The stellar rotation period of 16 days is readily detectable in our RV time series and in the ground-based photometry. We derived a likely age of 600–800 Myr for the parent star TOI-1801, which means that TOI-1801 b is the least massive young mini-Neptune with precise mass and radius determinations. Our results suggest that if TOI-1801 b had a larger atmosphere in the past, it must have been removed by some evolutionary mechanism on timescales shorter than 1 Gyr.
•Between 2017 and 2019 we developed in Romania the NEARBY cloud-based online platform to reduce survey images, detect, validate and report in near real time asteroid detections and NEA candidates. In ...2018 and 2019 we tested NEARBY during a few pilot mini-surveys observed with the Isaac Newton Telescope in La Palma. Two NEAs were discovered, recovered and reported promptly to MPC, other 4 recently discovered NEAs were confirmed, and other 22 Hungarias and 7 Mars crossing asteroids were discovered using NEARBY. We compare NEARBY with other few available software, presenting case study for possible future planned EURONEAR surveys.
In 2015 we started a PhD thesis aiming to write a moving objects processing system (MOPS) aimed to detect near Earth asteroids (NEAs) in astronomical surveys planned within the EURONEAR project. Based on this MOPS experience, in 2017 we proposed the NEARBY project to the Romanian Space Agency, which awarded funding to the Technical University of Cluj-Napoca (UTCN) and the University of Craiovafor building a cloud-based online platform to reduce survey images, detect, validate and report in near real time asteroid detections and NEA candidates. The NEARBY platform was built and is available at UTCN since Feb 2018, being tested during 5 pilot surveys observed in 2017-2018 with the Isaac Newton Telescope in La Palma. Two NEAs were discovered in Nov 2018 (2018 VQ1 and 2018 VN3), being recovered and reported to MPC within 2 hours. Other 4 discovered NEAs were found from a few dozen possible NEA candidates promptly being followed, allowing us to discover 22 Hungarias and 7 Mars crossing asteroids using the NEARBY platform. Compared with other few available software, NEARBY could detect more asteroids (by 8-41%), but scores less than human detection (by about 10%). Using resulted data, the astrometric accurancy, photometric limits and an INT NEA survey case study are presented as guidelines for planning future surveys.
PDF
