Roberto Speziali

Ground-based and Airborne Instrumentation for Astronomy IV

MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one in the J-band and one in the H-band, for detailed measurements of chemical abundances. The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of MOONS – extending into the near-IR – will provide the observational power necessary to study galaxy formation and evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch of re-ionization at z<8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS.

Optical and Infrared Observations of the Supernova SN 1999el

Optical and near-infrared light curves of the Type IIn supernova SN 1999el in NGC 6951 are presented. A period of 220 days (416 days in the near-infrared) is covered from the first observation obtained a few days before maximum light. Spectroscopic observations are also discussed. Using as a distance calibrator the Type Ia SN 2000E, which occurred some months later in the same galaxy, and fitting a blackbody law to the photometric data, we obtain a maximum bolometric luminosity for SN 1999el of ~1044 ergs s-1. In general, the photometric properties of SN 1999el are very similar to those of SN 1998S, a bright and well-studied Type IIn supernova, showing a fast decline in all observed bands similar to those of Type II-L supernovae. The differences with SN 1998S are analyzed and ascribed to the differences in a preexisting circumstellar envelope in which dust was already present at the moment of the SN outburst. We infer that light echoes may play a possibly significant role in affecting the observed properties of the light curves, although improved theoretical models are needed to account for the data. We conclude that mass loss in the progenitor RG stars is episodic and occurs in an asymmetric way. This implies that collapsing massive stars appear as normal Type II supernovae if this occurs far from major mass-loss episodes, whereas they appear as Type IIn supernovae if a large mass-loss episode is in progress.

CHARACTERIZING FAINT GALAXIES IN THE REIONIZATION EPOCH: LBT CONFIRMS TWO L < 0.2 L* SOURCES AT z = 6.4 BEHIND THE CLASH/FRONTIER FIELDS CLUSTER MACS0717.5+3745

We report the LBT/MODS1 spectroscopic confirmation of two images of faint Lyα emitters at z = 6.4 behind the Frontier Fields galaxy cluster MACSJ0717.5+3745. A wide range of lens models suggests that the two images are highly magnified, with a strong lower limit of μ > 5. These are the faintest z > 6 candidates spectroscopically confirmed to date. These may also be multiple images of the same z = 6.4 source as supported by their similar intrinsic properties, but the lens models are inconclusive regarding this interpretation. To be cautious, we derive the physical properties of each image individually. Thanks to the high magnification, the observed near-infrared (restframe ultraviolet) part of the spectral energy distributions and Lyα lines are well detected with S/N(m _(1500)) ≳ 10 and S/N(Lyα) ≃ 10-15. Adopting μ > 5, the absolute magnitudes, M _(1500), and Lyα fluxes are fainter than –18.7 and 2.8 × 10^(–18) erg s^(–1) cm^(–2), respectively. We find a very steep ultraviolet spectral slope β = –3.0 ± 0.5 (F _λ = λ^β), implying that these are very young, dust-free, and low metallicity objects, made of standard stellar populations or even extremely metal poor stars (age ≾ 30 Myr, E(B – V) = 0 and metallicity 0.0-0.2 Z/Z_☉). The objects are compact (<1 kpc^2) and with a stellar mass M_* < 10^8 M_☉. The very steep β, the presence of the Lyα line, and the intrinsic FWHM (<300 km s^(–1)) of these newborn objects do not exclude a possible leakage of ionizing radiation. We discuss the possibility that such faint galaxies may resemble those responsible for cosmic reionization.

The end of the white dwarf cooling sequence in M 67

In this paper, we present for the first time a proper-motion-selected white dwarf (WD) sample of the old Galactic open cluster M 67, down to the bottom of the WD cooling sequence (CS). The color-magnitude diagram is based on data collected with the LBC-Blue camera at the prime-focus of LBT. As first epoch data, we used CFHT-archive images collected 10 years before LBC data. We measured proper motions of all the identified sources. Proper motions are then used to separate foreground and background objects from the cluster stars, including WDs. Finally, the field-object cleaned WD CS in the V vs. B-I color-magnitude diagram is compared with the models. We confirm that the age derived from the location of the bottom of the WD CS is consistent with the turn off age.

The Be/X-ray transient KS 1947+300

We present optical spectroscopy and optical and infrared photometry of the counterpart to the transient X-ray source KS1947+300. The counterpart is shown to be a moderately reddened V = 14.2 early-type Be star located in an area of low interstellar absorption slightly above the Galactic plane. Changes in brightness are accompanied by correlated reddening of the source, as is expected in this kind of object. From intermediate resolution spectroscopy, we derive a spectral type B0Ve. If the intrinsic luminosity of the star is normal for its spectral type, KS1947+300 is situated at a distance of ∼10 kpc, implying that its X-ray luminosity at the peak of the spring 2000 X-ray outburst was typical of Type II outbursts in Be/X-ray transients. KS1947+300 is thus the first Be/X-ray recurrent transient showing Type II outbursts which has an almost circular orbit.

The identification of the optical/IR counterpart of the 15.8-s transient X–ray pulsar XTE J1946+274

We report on the discovery of the optical/IR counterpart of the 15.8 s transient X-ray pulsar XTE J1946+274. We re-analyzed archival BeppoSAX observations of XTE J1946+274 obtaining a new refined position (a circle with 22 00 radius at 90% confidence level). Based on this new position we carried out optical and infra-red (IR) follow-up observations. Within the new error circle we found a relatively optical faint (B= 18:6) IR bright (H= 12:1) early type reddened star (V R= 1:6). The optical spectra show strong H and H emission lines. The IR photometric observations of the field confirm the presence of an IR excess for the H-emitting star (K = 11:6, J H = 0:6) which is likely surrounded by a circumstellar envelope. Spectroscopic and photometric data indicate a B0-1V-IVe spectral-type star located at a distance of 8-10 kpc and confirm the Be-star/X-ray binary nature of XTE J1946+274.

SWIRCAM: a NIR imager-spectrometer to search for extragalactic supernovae

We present the main characteristics and astronomical results of SWIRCAM, a NIR imager-spectrometer mainly devoted to the search for extragalactic Supernovae, in the frame of the SWIRT project, a joint scientific collaboration among the Astronomical Observatories of Rome, Teramo and Pulkovo. The camera is currently at the focal plane of the AZT-24 1.1 m telescope at the Observing Station of Campo Imperatore, operated by the Astronomical Observatory of Rome. SWIRCAM saw its first light during December 1998 and it is currently employed for both the SWIRT operative phase and other institutional projects.

Large Binocular Telescope view of the atmosphere of GJ1214b

The atmospheric composition and vertical structure of the super-Earth GJ1214b has been a subject of debate since its discovery in 2009. Recent studies have indicated that high-altitude clouds might mask the lower layers. However, some data points that were gathered at different times and facilities do not fit this picture, probably because of a combination of stellar activity and systematic errors. We observed two transits of GJ1214b with the Large Binocular Camera, the dual-channel camera at the Large Binocular Telescope. For the first time, we simultaneously measured the relative planetary radius

Wide and deep near-UV (360 nm) galaxy counts and the extragalactic background light with the Large Binocular Camera

k=R_\mathrm{p}/R_\star

LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg IX

at blue and red optical wavelengths (