24 research outputs found
Small telescopes being effective: MAGIC or not?
The paper describes the MAGIC multi-mode focal reducer (Monitoring of Active
Galaxies by Investigation of their Cores), commissioned on the 1-m Zeiss-1000
telescope of the Special Astrophysical Observatory of the Russian Academy of
Sciences in September 2020. Three observational modes are currently realised:
photometry, polarimetry, and long-slit spectroscopy. Reducing the focal length
makes it possible to obtain a sufficiently large field of view for photometry
and a large slit height for spectroscopy of 12, as well as a large
field of view for polarimetry with a quadrupole Wollaston prism of
6.4. This feature makes the complex study of extended nebulae and
galaxies efficient. The MAGIC capabilities are presented in examples of
observations of various astronomical objects. The spectral mode in the range of
4000-7200 AA provides the spectral resolution 1000; for a starlike
target up to 14 mag in medium-band filters with a seeing of 1 for 20
minutes of total exposure, the photometry accuracy is better than 0.01 mag and
the polarization accuracy is better than 0.6%. Especially for the new focal
reducer, an offset guide and a position angle rotation system were implemented.
The results of the modernization of the baffle system in the optical scheme of
the telescope for the suppression of scattered light are also described
3D structure of the H ii region Sh2-235 from tunable-filter optical observations
We present observations of the H α, H β, [S ii] λλ6716, 6731 and [N ii] λ6583 emission lines in the galactic H ii region Sh2-235 with the Mapper of Narrow Galaxy Lines (MaNGaL), a tunable filter at the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We show that the H ii region is obscured by neutral material with AV ≈ 2-4 mag. The area with the highest AV is situated to the south-west from the ionizing star and coincides with a maximum detected electron density of â 300 cm-3. The combination of these results with archive AKARI far-infrared data allows us to estimate the contribution of the front and rear walls to the total column density of neutral material in S235 and explain the 3D structure of the region. The H ii region consist of a denser, more compact portion deeply embedded in the neutral medium and the less dense and obscured gas. The front and rear walls of the H ii region are inhomogeneous, with the material in the rear wall having a higher column density. We find a two-sided photodissociation region in the dense clump S235 East 1, illuminated by a UV field with G0 = 50-70 and 200 Habing units in the western and eastern parts, respectively. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
The TELPERION survey for distant [O iii] clouds around luminous and hibernating AGN
We present a narrow-band [O iii] imaging survey of 111 active galactic nucleus (AGN) hosts and 17 merging-galaxy systems, in search of distant extended emission-line regions (EELRs) around AGNs (either extant or faded). Our data reach deeper than detection from the broad-band SDSS data and cover a wider field than some early emission-line surveys used to study extended structure around AGNs. Spectroscopic follow-up confirms two new distant AGN-ionized clouds, in the merging systems NGC 235 and NGC 5514, projected at 26 and 75 kpc from the nuclei (respectively). We also recover the previously known region in NGC 7252. These results strengthen the connection between EELRs and tidal features; kinematically quiescent distant EELRs are virtually always photoionized tidal debris. We see them in ≈10 per cent of the galaxies in our sample with tidal tails. Energy budgets suggest that the AGN in NGC 5514 has faded by >3 times during the extra light traveltime ≈250 000 yr from the nucleus to the cloud and then to the observer; strong shock emission in outflows masks the optical signature of the AGN. For NGC 235 our data are consistent with but do not unequivocally require variation over ≈85 000 yr. In addition to these very distant ionized clouds, we find luminous and extensive line emission within four galaxies - IC 1481, ESO 362-G08, NGC 5514, and NGC 7679. Among these, IC 1481 shows apparent ionization cones, a rare combination with its LINER AGN spectrum. In NGC 5514, we measure a 7-kpc shell expanding at ≈370 km s-1 west of the nucleus. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631
We present an observational study of the luminous red nova (LRN) AT\,2021biy
in the nearby galaxy NGC\,4631. The field of the object was routinely imaged
during the pre-eruptive stage by synoptic surveys, but the transient was
detected only at a few epochs from \,days before maximum brightness.
The LRN outburst was monitored with unprecedented cadence both photometrically
and spectroscopically. AT\,2021biy shows a short-duration blue peak, with a
bolometric luminosity of \,erg\,s, followed by
the longest plateau among LRNe to date, with a duration of 210\,days. A
late-time hump in the light curve was also observed, possibly produced by a
shell-shell collision. AT\,2021biy exhibits the typical spectral evolution of
LRNe. Early-time spectra are characterised by a blue continuum and prominent H
emission lines. Then, the continuum becomes redder, resembling that of a K-type
star with a forest of metal absorption lines during the plateau phase. Finally,
late-time spectra show a very red continuum ( K)
with molecular features (e.g., TiO) resembling those of M-type stars.
Spectropolarimetric analysis indicates that AT\,2021biy has local dust
properties similar to those of V838\,Mon in the Milky Way Galaxy. Inspection of
archival {\it Hubble Space Telescope} data taken on 2003 August 3 reveals a
\,\msun\ progenitor candidate with log\,\,dex and \,K at solar metallicity. The above
luminosity and colour match those of a luminous yellow supergiant. Most likely,
this source is a close binary, with a 17--24\,\msun\ primary component.Comment: 21 pages, 14 figures. Accepted by Astronomy and Astrophysic
Forbidden hugs in pandemic times III. Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631
We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6 × 1041 erg s−1, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (TBB ≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival Hubble Space Telescope data taken on 2003 August 3 reveals a ∼20 M⊙ progenitor candidate with log (L/L⊙) = 5.0 dex and Teff = 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17–24 M⊙ primary component. </p