Giorgio Calderone

There is a short gamma-ray burst prompt phase at the beginning of each long one

We compare the prompt intrinsic spectral properties of a sample of short Gamma--ray Burst (GRB) with the first 0.3 seconds (rest frame) of long GRBs observed by Fermi/GBM. We find that short GRBs and the first part of long GRBs lie on the same E_p--E_iso correlation, that is parallel to the relation for the time averaged spectra of long GRBs. Moreover, they are indistinguishable in the E_p--L_iso plane. This suggests that the emission mechanism is the same for short and for the beginning of long events, and both short and long GRBs are very similar phenomena, occurring on different timescales. If the central engine of a long GRB would stop after ~0.3 * (1+z) seconds the resulting event would be spectrally indistinguishable from a short GRB.

The optical-UV emissivity of quasars: Dependence on black hole mass and radio loudness

We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 < z < 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) alpha_3000 continuum slopes (L_\nu~\nu^alpha at 3000Ang) with increasing black hole mass, bluer alpha_3000 with increasing luminosity at 3000Ang, and bluer alpha_3000 with increasing spin of the black hole, when all other parameters are held fixed. We find no clear evidence for any of these predictions in the data. In particular we find that: (i) alpha_3000 shows no significant dependence on black hole mass or luminosity. Dedicated Monte Carlo tests suggest that the substantial observational uncertainties in the black hole virial masses can effectively erase any intrinsic dependence of alpha_3000 on black hole mass, in line with some previous studies. (ii) The mean slope alpha_3000 of radio-loud sources, thought to be produced by rapidly spinning black holes, is comparable to, or even redder than, that of radio-quiet quasars. Indeed, although quasars appear to become more radio loud with decreasing luminosity, we still do not detect any significant dependence of alpha_3000 on radio loudness. The predicted mean alpha_3000 slopes tend to be bluer than in the data. Disk models with high inclinations and dust extinction tend to produce redder slopes closer to empirical estimates. Our mean alpha_3000 values are close to the ones independently inferred at z<0.5 suggesting weak evolution with redshift, at least for moderately luminous quasars.

QSFit: automatic analysis of optical AGN spectra

We present QSFit (Quasar Spectral Fitting package), a new software package to automatically perform the analysis of active galactic nuclei (AGNs) optical spectra. The software provides luminosity estimates for the AGN continuum, the Balmer continuum, both optical and ultraviolet iron blended complex, host galaxy and emission lines, as well as width, velocity offset and equivalent width of 20 emission lines. Improving on a number of previous studies on AGN spectral analysis, QSFit fits all the components simultaneously, using an AGN continuum model which extends over the entire available spectrum, and is thus a probe of the actual AGN continuum whose estimates are scarcely influenced by localized features (e.g. emission lines) in the spectrum. We used QSFit to analyse 71  251 optical spectra of Type 1 AGN at z < 2 (obtained by the Sloan Digital Sky Survey, SDSS) and to produce a publicly available catalogue of AGN spectral properties. Such catalogue allowed us (for the first time) to estimate the AGN continuum slope and the Balmer continuum luminosity on a very large sample, and to show that there is no evident correlation between these quantities the redshift. All data in the catalogue, the plots with best-fitting model and residuals, and the idl code we used to perform the analysis, are available on a dedicated website. The whole fitting process is customizable for specific needs, and can be extended to analyse spectra from other data sources. The ultimate purpose of QSFit is to allow astronomers to run standardized recipes to analyse the AGN data, in a simple, replicable and shareable way.

Multiple Depth DB Tables Indexing on the Sphere

Any project dealing with large astronomical datasets should consider the use of a relational database server (RDBS). Queries requiring quick selections on sky regions, objects cross-matching and other high-level data investigations involving sky coordinates could be unfeasible if tables are missing an effective indexing scheme. In this paper we present the Dynamic Index Facility (DIF) software package. By using the HTM and HEALPix sky pixelization schema, it allows a very efficient indexing and management of spherical data stored into MySQL tables. Any table hosting spherical coordinates can be automatically managed by DIF using any number of sky resolutions at the same time. DIF comprises a set of facilities among which SQL callable functions to perform queries on circular and rectangular regions. Moreover, by removing the limitations and difficulties of 2-d data indexing, DIF allows the full exploitation of the RDBS capabilities. Performance tests on Giga-entries tables are reported together with some practical usage of the package.

ESPRESSO instrument control software and electronics: commissioning in Paranal

The ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) spectrograph, after the preliminary tests carried out at the Astronomical Observatory of Geneva (Switzerland), has been shipped and re-integrated at the Very Large Telescope (VLT) site in Cerro Paranal (Chile). The instrument control software, designed and developed at INAF–Osservatorio Astronomico di Trieste, had to face several challenges since ESPRESSO is the first instrument placed at the VLT Coud`e Combined Laboratory able to be fed by up to 4 Telescope Units simultaneously (through an incoherent focus), and whose electronics is based on Beckhoff PLCs. Moreover, ESPRESSO requires a careful stabilization of the field image in order to maximize the light flux through the fiber hole, and reach the instrumental radial-velocity precision level of 10 cm/s. These circumstances lead to the development of a few solutions specifically dedicated to ESPRESSO. In this paper we will summarize the features of the ESPRESSO control software, the tests performed during the integration phase in Europe, and discuss the main performances obtained during the commissioning phase and ”first light” observations in Chile

A complete automatization of an educational observatory at INAF-OATs

The Astronomical Observatory of Trieste (OATs), part of the Italian Institute for Astrophysics (INAF), hosts a Celestron C14 telescope, equipped with a robotic Paramount ME equatorial mount, used for public outreach. The telescope is installed inside a dome, recently upgraded with a Beckhoff PLC control system, a SIEMENS inverter for the communication with the motor of the domes roof, and further equipment to allow the complete automatization of the system. A peculiarity of the system is that, when operating, the telescope may exceed the height of the roof: due to this fact the telescope pointing is constrained by the full opening of the roof and, oppositely, the closing of the roof is allowed only when the telescope is in park position. Appropriate sensors are installed to monitor the position of the telescope to properly handle the complete opening or closing of the roof. Several emergency operations are also foreseen, for example in case of bad weather or lost connection with the user. The PLC software has been developed using TwinCAT software. An OPC-UA server is installed in the PLC and allows the communication with a web interface. The web GUI, developed in PHP and Javascript, allows the user to perform the remote operations like switching on all the instrumentations, open the domes roof, park the telescope and view the status of the system. Furthermore through TheSkyX software it is possible to perform the pointing of the telescope and its set up. A dedicated script, interfaced with TheSkyX, have been implemented to perform a complete automated acquisition. An appropriate data storage system is foreseen. All these elements, that cooperate to create a fully remoted controlled system, are presented in this paper.

Astrocook: a thousand recipes to cook a spectrum

Astrocook is a new Python package to analyze the spectra of quasi-stellar objects (QSOs) from the near-UV band to the near-infrared band. The project stems from the lessons learned in developing the data analysis software for the VLT ESPRESSO spectrograph. The idea is to leverage numerical libraries like SciPy, NumPy, and Lmfit and astronomical libraries like Astropy to produce a collection of high-level recipes capable of interpreting the features observed in QSO spectra (such as the emission continuum and the absorption systems) in an automated and validated way. The package provides great flexibility in designing the operational workflow, as well as a set of interactive tools to apply the recipes in a seamless way. The aim is to achieve the combination of accuracy, stability, and repeatability of the procedure that is required by several compelling science cases in the era of ”precision cosmology” (e.g. the measurement of a possible variability in the value of fundamental constants, and the direct measurement of the accelerated expansion of the Universe).

ESPRESSO data flow in operations: results of commissioning activities

ESPRESSO, the next generation ESO VLT high-resolution ultra-stable spectrograph, after the successful Preliminary Acceptance Europe held at the integration site of the Observatory of Geneva, has been re-integrated at Paranal and started its commissioning activities at the end of 2017. One critical aspect for ESPRESSO future operations, compared with other instruments currently running at ESO, is the way it will be operated which poses several constraints on its data flow. ESPRESSO has been conceived and developed as a “truly science-grade products generating machine” thanks to its fixed format and long-term stability. In addition to the Data Reduction Software (DRS), a Data Analysis Software (DAS), developed within the standard ESO Data Flow System, will be provided to the users – a novelty for the instruments at Paranal. Moreover, ESPRESSO will be fed either by the light of any of the UTs or by the incoherently combined light of up to four UTs, a feature which required a re-thinking of the current Paranal data handling injection schema. In this paper, after describing the main challenges and peculiarities of the ESPRESSO data flow system listed above, we will present the results of the first commissioning activities and the lessons learned to handle data produced by an instrument with such ambitious scientific requirements.

EELT-HIRES the high resolution spectrograph for the E-ELT: software and hardware solutions for its control

The current E-ELT instrumentation plan foresees a High Resolution Spectrograph conventionally indicated as EELTHIRES whose Phase A study has started in March 2016. Since 2013 however, a preliminary study of a modular E-ELT instrument able to provide high-resolution spectroscopy (R~100,000) in a wide wavelength range (0.37-2.5 μm) has been already conducted by an international consortium (termed “HIRES initiative”). Taking into account the requirements inferred from this preliminary work in terms of both high-level operations as well as low-level control, we will present in this paper possible solutions for HIRES hardware and software architecture. The validity of the proposed architectural and hardware choices will be eventually discussed based also on the experience gained on a real-working instrument, ESPRESSO, the next generation high-stability spectrograph for the VLT and to certain extent the precursor of HIRES.

The technical CCDs in ESPRESSO: usage, performances, and network requirements

The Echelle Spectrograph for Rocky Exoplanets and Stable Spectral Observations (ESPRESSO) requires active-loop stabilization of the light path from the telescope to the spectrograph, in order to achieve its centimeter-per- second precision goal. This task is accomplished by moving the mirrors placed along the light path by means of piezoelectric actuators. Two cameras are used to acquire the field and pupil images, and the required corrections are dynamically calculated and applied to the piezos. In this paper we will discuss the camera usage, performance and network bandwidth requirements for the ESPRESSO scientific operations.