arXiv subjects

M. Ribó

Publications and source records attributed to M. Ribó.

At least 19 recordsLinked to original sources

arXiv2026

Enabling population studies on wind-driven Galactic binary systems

Galactic binaries driven by stellar wind shocks, such as colliding wind binaries (CWBs) and gamma-ray binaries (gBs), harbor one of the most efficient particle acceleration engines known in the Universe. Despite their potential, these sources remain relatively unexplored, particularly in the domains of low radio frequencies and very high resolution. As a result, we lack comprehensive population studies and well-characterized individual systems. Only a few of these binaries, such as the iconic gB PSR B1259$-$63 or the massive CWB WR 140, have been studied in enough detail to probe their wind dynamics and shock physics. Current observations lack the sensitivity to detect weak non-thermal synchrotron emission from low-energy particle populations and the angular resolution to resolve shock structures on sub-au scales. The Square Kilometre Array Observatory (SKAO) will mark a significant improvement in both sensitivity and resolution with its SKA-low and SKA-mid telescopes, solving these challenges. This will enable systematic studies of the winds and shock interactions in these binary systems. Additionally, SKA-VLBI will facilitate the observation of changes in shock geometry at different orbital phases, linking particle acceleration processes to the binary's orbital characteristics and stellar wind properties. SKAO will pave the way for comprehensive population studies of these energetic binary systems.

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arXiv2026

The IACOB project: XVI. Surface helium abundances in Galactic O-type stars: indications for identifying binary interaction products

The presence of massive O-type stars with surfaces enriched by CNO-cycle products has been known since the early 1980s. For many years, internal rotational mixing was assumed to be the dominant mechanism responsible for this chemical contamination. However, accumulating evidence now suggests that binary interaction -- particularly mass-transfer episodes -- may play an equally important, if not dominant, role. We aim to carry out a large-scale investigation of surface helium (He) abundances in Galactic O-type stars, based on the results from the analysis of high-quality spectroscopic data from the IACOB project. We perform a homogeneous spectroscopic analysis of 318 Galactic O-type stars with the IACOB-BROAD and FASTWIND/IACOB-GBAT tools, deriving rotational velocities, atmospheric parameters, and He abundances. We also account for the influence of binarity, runaway status, and parameter degeneracies (e.g., microturbulence, wind properties, diagnostic lines, and companion contamination) on the abundance determinations. We present homogeneously determined surface He abundances (YHe=N(He)/N(H)) for the so far largest, statistically significant sample of Galactic O-type stars. About 78% of the stars show He abundances consistent with the previously proposed cosmic abundance standard of YHe=0.098$\pm$0.002. The remaining 22% display clear He enrichment (YHe>0.13). We also provide observational evidence indicating that most of these He-enriched stars are likely the products of binary interaction. Our study highlights how large spectroscopic surveys are gradually opening robust observational avenues to identify the products of massive binary interaction. It also emphasizes the need for caution when interpreting the spectroscopic properties of apparently single O-type stars. A significant fraction may in fact be the outcome of binary evolution rather than isolated stellar birth.

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arXiv2025

An observational study of rotation and binarity of Galactic O-type runaway stars

Gaia DR3 data have revealed new massive runaway stars, while spectroscopic surveys enable detailed characterization. The relative contributions of binary supernova (BSS) and dynamical ejection (DES) scenarios to explain their runaway origin remain poorly constrained, particularly in the Milky Way. We aim to characterize the largest sample of Galactic O-type runaway stars ever investigated through their kinematics, rotation, and binarity to shed light into their origins. We use the GOSC-Gaia DR3 catalog, and IACOB spectroscopic information to build a sample with 214 O-type stars with projected rotational velocities ($v \sin{i}$), and a subsample of 168 O-type stars with additional information about their likely single (LS) or single-lined (SB1) spectroscopic binary nature. We also consider an additional sample of 65 double-lined (SB2) spectroscopic binaries. We find that among our sample of Galactic O-type runaways, most (74%) have $v \sin{i}<200$ km/s, whereas for normal stars this fraction is slightly higher (82%). There are no fast-moving runaways being fast rotators, except for HD 124 979. Runaways show lower SB1 fractions than normal stars, with no runaway SB1 fast-rotating systems; on average, runaways rotate faster than normal stars; and their runaway fraction is higher among fast rotators (44%) vs. the slow rotators (34%). This is consistent with BSS dominance for fast rotators. We also found that SB2 systems hardly reach runaway velocities with a low runaway fraction (10%). Runaways with 2D velocities > 60 km/s are mostly single and interpreted as DES products, while runaways with 2D velocities > 85 km/s are also interpreted as two-step products. Three of 12 runaway SB1 systems are HMXBs. Our study reveals that most Galactic O-type runaways are slow rotators, suggests a dominance of BSS among fast-rotating runaways, and of DES and two-step among the high-velocity ones. (Abridged)

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arXiv2025

New stellar bow shocks and bubbles found around runaway stars

Runaway stars with peculiar high velocities can generate stellar bow shocks. Only a few bow shocks show clear radio emission. Our goal is to identify and characterize new stellar bow shocks around O and Be runaway stars in the infrared (IR), and to study their possible radio emission and nature. Our input data is a catalog of O and Be runaways compiled using Gaia DR3. We used WISE IR images to search for bow shocks around these runaways, Gaia DR3 data to determine the actual motion of the runaway stars corrected for interstellar medium (ISM) motion caused by Galactic rotation, and archival radio data to search for emission signatures. We finally explored the radio detectability of these sources under thermal and nonthermal scenarios. We found 9 new stellar bow shock candidates, 3 new bubble candidates, and 1 intermediate structure candidate. One of them is an in situ bow shock candidate. We also found 17 already known bow shocks in our sample, though we discarded one, and 62 miscellaneous sources showing some IR emission around the runaways. We geometrically characterized the sources in IR using the WISE-4 band and estimated the ISM density at the bow shock positions, obtaining median values of ~6 and ~4 cm$^{-3}$ using 2D and 3D peculiar velocities. Most of the new discovered bow shocks come from new runaway discoveries. Within our samples we found that ~24% of the O-type runaway stars show bow shocks, while this decreases to ~3% for Be-type runaway stars. Two bow shocks present radio emission but not as clear counterparts, and two others show hints of radio emission. The physical scenarios indicate that two sources could still be compatible with nonthermal radio emission. The new sample of O and Be runaway stars allowed us to discover both new stellar bow shocks and bubbles. Their geometrical characterization can be used to assess the physical scenario of the radio emission. (Abridged)

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arXiv2024

Runaway O and Be stars found using Gaia DR3, new stellar bow shocks and search for binaries

A relevant fraction of massive stars are runaways, moving with a significant peculiar velocity with respect to their environment. Kicks from supernova explosions or the dynamical ejection of stars from clusters can account for the runaway genesis. We have used Gaia DR3 data to study the velocity distribution of massive O and Be stars from the GOSC and BeSS catalogs and identify runaway stars using a 2D-velocity method. We have discovered 42 new runaways from GOSC and 47 from BeSS, among a total of 106 and 69 runaways found within these catalogs, respectively. These numbers imply a percentage of runaways of ~25% for O-type stars ~5% for Be-type stars. The higher percentages and higher velocities found for O-type compared to Be-type runaways suggest that the dynamical ejection scenario is more likely than the supernova explosion scenario. We have also performed multi-wavelength studies of our runaways. We have used WISE infrared images to discover 13 new stellar bow shocks around the runaway stars. We have also conducted VLA radio observations of some of these bow shocks. Finally, our runaway stars include six X-ray binaries and one gamma-ray binary, implying that new such systems could be found by conducting detailed multi-wavelength studies. In this work we report on this ongoing project to find new runaway stars, study their interaction with the ISM and search for high-energy binary systems.

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arXiv2023

Galactic runaway O and Be stars found using Gaia DR3

A relevant fraction of massive stars are runaway stars. These stars move with a significant peculiar velocity with respect to their environment. We aim to discover and characterize the population of massive and early-type runaway stars in the GOSC and BeSS catalogs using Gaia DR3 astrometric data. We present a 2-dimensional method in the velocity space to discover runaway stars as those that deviate significantly from the velocity distribution of field stars, which are considered to follow the Galactic rotation curve. We found 106 O runaway stars, 42 of which were not previously identified as runaways. We found 69 Be runaway stars, 47 of which were not previously identified as runaways. The dispersion of runaway stars is a few times higher in Z and b than that of field stars. This is explained by the ejections they underwent when they became runaways. The percentage of runaways is 25.4% for O-type stars, and it is 5.2% for Be-type stars. In addition, we conducted simulations in 3 dimensions for our catalogs. They revealed that these percentages could increase to ~30% and ~6.7%, respectively. Our runaway stars include seven X-ray binaries and one gamma-ray binary. Moreover, we obtain velocity dispersions of ~5 km/s perpendicular to the Galactic plane for O- and Be-type field stars. These values increase in the Galactic plane to ~7 km/s for O-type stars due to uncertainties and to ~9 km/s for Be-type stars due to Galactic velocity diffusion. The excellent Gaia DR3 astrometric data have allowed us to identify a significant number of O-type and Be-type runaways in the GOSC and BeSS catalogs. The higher percentages and higher velocities found for O-type compared to Be-type runaways underline that the dynamical ejection scenario is more likely than the binary supernova scenario. Our results open the door to identifying new high-energy systems among our runaways by conducting detailed studies.

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arXiv2021

Measurement of performance of the NectarCAM photodetectors

NectarCAM is a camera for the medium-sized telescopes of the Cherenkov Telescope Array (CTA), which covers the energy range of 100 GeV to 30 TeV. The camera is equipped with 265 focal plane modules (FPMs). Each FPM comprises 7 pixels, each consisting of a photo-multiplier tube, a preamplifier, an independently controlled power supply, and a common control system. We developed a dedicated test bench to validate and qualify the industrial FPM production and to measure the performance of each FPM in a dark room before its integration in the camera. We report the measured performance of 61 FPM prototypes obtained with our experimental setup. We demonstrate that the gains of the photo multiplier tubes are stable and that pulse widths, transit time spreads, afterpulse rates and charge resolutions are within the specifications for NectarCAM.

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arXiv2019

Multi-wavelength observation of MAXI J1820+070 with MAGIC, VERITAS and H.E.S.S

MAXI J1820+070 is a new low-mass microquasar hosting a black hole recently discovered in X-rays by the MAXI instrument. It is the counterpart of ASASSN-18ey, discovered in optical a few days before by ASAS-SN. This source underwent a major outburst in 2018, during which it completed the typical "q-shaped" path in the hardness-intensity diagram. MAGIC, VERITAS and H.E.S.S. gamma-ray telescopes observed the sky position of MAXI J1820+070 for a total of more than 90 hours in 2018. In addition, some observations were carried out using MAGIC Central Pixel - a dedicated central pixel capable of detecting fast optical signals (10 kHz sampling rate, peak sensitivity in the U-band). This contribution presents the methods used to search for transient optical and very high energy gamma-ray emission from MAXI J1820+070, as well as the latest results in these energy ranges.

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arXiv2018

Refining the origins of the gamma-ray binary 1FGL J1018.6-5856

Gamma-ray binaries are systems composed of a massive star and a compact object that exhibit emission from radio to very high energy gamma rays. They are ideal laboratories to study particle acceleration and a variety of physical processes that vary as a function of the orbital phase. We aim to study the radio emission of the gamma-ray binary 1FGL J1018.6-5856 to constrain the emitting region and determine the peculiar motion of the system within the Galaxy to clarify its origin by analyzing an observation with the Australian Long Baseline Array at 8.4~GHz. We combined these data with the optical Gaia DR2 and UCAC4 catalogs to consolidate the astrometry information therein. 1FGL J1018.6-5856 shows compact radio emission ($< 3$ mas or $\lesssim 20$ au at $\sim 6.4$ kpc distance), implying a brightness temperature of $\gtrsim 5.6 \times 10^6$ K, and confirming its nonthermal origin. We report consistent results between the proper motion reported by Gaia DR2 and the positions obtained from the Gaia, UCAC4, and LBA data. We also determined the distance to 1FGL J1018.6-5856 to be $6.4_{-0.7}^{+ 1.7}$ kpc. Together with the radial velocity of the source we computed its three-dimensional proper and peculiar motion within the Galaxy. We obtained a peculiar motion on its regional standard of rest (RSR) frame of $|u| = 45_{-9}^{+30}$ km s$^{-1}$, with the system moving away from the Galactic plane. In the simplest scenario of a symmetric stellar core collapse we estimate a mass loss of $ 4 \lesssim ΔM \lesssim 9$ M$_{\odot}$ during the creation of the compact object. 1FGL J1018.6-5856 exhibits compact radio emission similar to that detected in other gamma-ray binaries. We provide the first accurate peculiar motion estimations of the system and place it within the Galaxy. The obtained motion and distance excludes its physical relation with the supernova remnant G284.3-1.8.

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arXiv2017

Gamma rays from microquasars Cygnus X-1 and Cygnus X-3

Gamma-ray observations of microquasars at high and very-high energies can provide valuable information of the acceleration processes inside the jets, the jet-environment interaction and the disk-jet coupling. Two high-mass microquasars have been deeply studied to shed light on these aspects: Cygnus X-1 and Cygnus X-3. Both systems display the canonical hard and soft X-ray spectral states of black hole transients, where the radiation is dominated by non-thermal emission from the corona and jets and by thermal emission from the disk, respectively. Here, we report on the detection of Cygnus X-1 above 60 MeV using 7.5 yr of Pass8 Fermi-LAT data, correlated with the hard X-ray state. A hint of orbital flux modulation was also found, as the source is only detected in phases around the compact object superior conjunction. We conclude that the high-energy gamma-ray emission from Cygnus X-1 is most likely associated with jets and its detection allow us to constrain the production site. Moreover, we include in the discussion the final results of a MAGIC long-term campaign on Cygnus X-1 that reaches almost 100 hr of observations at different X-ray states. On the other hand, during summer 2016, Cygnus X-3 underwent a flaring activity period in radio and high-energy gamma rays, similar to the one that led to its detection in the high-energy regime in 2009. MAGIC performed comprehensive follow-up observations for a total of about 70 hr. We discuss our results in a multi-wavelength context.

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arXiv2017

The First Simultaneous X-Ray/Radio Detection of the First Be/BH System MWC 656

MWC 656 is the first known Be/black hole (BH) binary system. Be/BH binaries are important in the context of binary system evolution and sources of detectable gravitational waves because they are possible precursors of coalescing neutron star/BH binaries. X-ray observations conducted in 2013 revealed that MWC 656 is a quiescent high-mass X-ray binary (HMXB), opening the possibility to explore X-ray/radio correlations and the accretion/ejection coupling down to low luminosities for BH HMXBs. Here we report on a deep joint Chandra/VLA observation of MWC 656 (and contemporaneous optical data) conducted in 2015 July that has allowed us to unambiguously identify the X-ray counterpart of the source. The X-ray spectrum can be fitted with a power law with $Γ\sim2$, providing a flux of $\simeq4\times10^{-15}$ erg cm$^{-2}$ s$^{-1}$ in the 0.5-8 keV energy range and a luminosity of $L_{\rm X}\simeq3\times10^{30}$ erg s$^{-1}$ at a 2.6 kpc distance. For a 5 M$_\odot$ BH this translates into $\simeq5\times10^{-9}$ $L_{\rm Edd}$. These results imply that MWC 656 is about 7 times fainter in X-rays than it was two years before and reaches the faintest X-ray luminosities ever detected in stellar-mass BHs. The radio data provide a detection with a peak flux density of $3.5\pm1.1$ $μ$Jy beam$^{-1}$. The obtained X-ray/radio luminosities for this quiescent BH HMXB are fully compatible with those of the X-ray/radio correlations derived from quiescent BH low-mass X-ray binaries. These results show that the accretion/ejection coupling in stellar-mass BHs is independent of the nature of the donor star.

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arXiv2015

Orbital and superorbital variability of LS I +61 303 at low radio frequencies with GMRT and LOFAR

LS I +61 303 is a gamma-ray binary that exhibits an outburst at GHz frequencies each orbital cycle of $\approx$ 26.5 d and a superorbital modulation with a period of $\approx$ 4.6 yr. We have performed a detailed study of the low-frequency radio emission of LS I +61 303 by analysing all the archival GMRT data at 150, 235 and 610 MHz, and conducting regular LOFAR observations within the Radio Sky Monitor (RSM) at 150 MHz. We have detected the source for the first time at 150 MHz, which is also the first detection of a gamma-ray binary at such a low frequency. We have obtained the light-curves of the source at 150, 235 and 610 MHz, all of them showing orbital modulation. The light-curves at 235 and 610 MHz also show the existence of superorbital variability. A comparison with contemporaneous 15-GHz data shows remarkable differences with these light-curves. At 15 GHz we see clear outbursts, whereas at low frequencies we see variability with wide maxima. The light-curve at 235 MHz seems to be anticorrelated with the one at 610 MHz, implying a shift of $\sim$ 0.5 orbital phases in the maxima. We model the shifts between the maxima at different frequencies as due to changes in the physical parameters of the emitting region assuming either free-free absorption or synchrotron self-absorption, obtaining expansion velocities for this region close to the stellar wind velocity with both mechanisms.

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arXiv2015

Physical properties of the gamma-ray binary LS 5039 through low and high frequency radio observations

We have studied in detail the 0.15-15 GHz radio spectrum of the gamma-ray binary LS 5039 to look for a possible turnover and absorption mechanisms at low frequencies, and to constrain the physical properties of its emission. We have analysed two archival VLA monitorings, all the available archival GMRT data and a coordinated quasi-simultaneous observational campaign conducted in 2013 with GMRT and WSRT. The data show that the radio emission of LS 5039 is persistent on day, week and year timescales, with a variability $\lesssim 25~\%$ at all frequencies, and no signature of orbital modulation. The obtained spectra reveal a power-law shape with a curvature below 5 GHz and a turnover at $\sim0.5$ GHz, which can be reproduced by a one-zone model with synchrotron self-absorption plus Razin effect. We obtain a coherent picture for a size of the emitting region of $\sim0.85~\mathrm{mas}$, setting a magnetic field of $B\sim20~\mathrm{mG}$, an electron density of $n_{\rm e}\sim4\times10^5~{\rm cm^{-3}}$ and a mass-loss rate of $\dot M\sim5\times10^{-8}~{\rm M_{\odot} yr^{-1}}$. These values imply a significant mixing of the stellar wind with the relativistic plasma outflow from the compact companion. At particular epochs the Razin effect is negligible, implying changes in the injection and the electron density or magnetic field. The Razin effect is reported for first time in a gamma-ray binary, giving further support to the young non-accreting pulsar scenario.

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arXiv2015

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outburst with a period of ~4.6 yr. We present optical photometric observations of LS I +61 303 spanning ~1.5 yr and contemporaneous Halpha equivalent width (EW Halpha) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EW Halpha presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ~0.1-0.2 in orbital phase with respect to the EW Halpha measurements at similar superorbital phases, and presents a lag of ~0.1 and ~0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EW Halpha, are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EW Halpha is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk.

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arXiv2014

Discovery of X-ray emission from the first Be/black hole system

MWC 656 (= HD 215227) was recently discovered to be the first binary system composed of a Be star and a black hole (BH). We observed it with \textit{XMM-Newton}, and detected a faint X-ray source compatible with the position of the optical star, thus proving it to be the first Be/BH X-ray binary. The spectrum analysis requires a model fit with two components, a black body plus a power law, with $k_{\rm B}T = 0.07^{+0.04}_{-0.03}$~keV and a photon index $Γ= 1.0\pm0.8$, respectively. The non-thermal component dominates above $\simeq$0.8 keV. The obtained total flux is $F(0.3$--$5.5~{\rm keV}) = (4.6^{+1.3}_{-1.1})\times10^{-14}$ erg cm$^{-2}$ s$^{-1}$. At a distance of $2.6\pm0.6$~kpc the total flux translates into a luminosity $L_{\rm X} = (3.7\pm1.7)\times10^{31}$ erg s$^{-1}$. Considering the estimated range of BH masses to be 3.8--6.9 $M_{\odot}$, this luminosity represents $(6.7\pm4.4)\times10^{-8}~L_{\rm Edd}$, which is typical of stellar-mass BHs in quiescence. We discuss the origin of the two spectral components: the thermal component is associated with the hot wind of the Be star, whereas the power law component is associated with emission from the vicinity of the BH. We also find that the position of MWC~656 in the radio versus X-ray luminosity diagram may be consistent with the radio/X-ray correlation observed in BH low-mass X-ray binaries. This suggests that this correlation might also be valid for BH high-mass X-ray binaries (HMXBs) with X-ray luminosities down to $\sim10^{-8} L_{\rm Edd}$. MWC~656 will allow the accretion processes and the accretion/ejection coupling at very low luminosities for BH~HMXBs to be studied.

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arXiv2014

Multi-wavelength observations of the binary system PSR B1259-63/LS 2883 around the 2010-2011 periastron passage

We report on broad multi-wavelength observations of the 2010-2011 periastron passage of the gamma-ray loud binary system PSR B1259-63. High resolution interferometric radio observations establish extended radio emission trailing the position of the pulsar. Observations with the Fermi Gamma-ray Space Telescope reveal GeV gamma-ray flaring activity of the system, reaching the spin-down luminosity of the pulsar, around 30 days after periastron. There are no clear signatures of variability at radio, X-ray and TeV energies at the time of the GeV flare. Variability around periastron in the H$α$ emission line, can be interpreted as the gravitational interaction between the pulsar and the circumstellar disk. The equivalent width of the H$α$ grows from a few days before periastron until a few days later, and decreases again between 18 and 46 days after periastron. In near infrared we observe the similar decrease of the equivalent width of Br$γ$ line between the 40th and 117th day after the periastron. For the idealized disk, the variability of the H$α$ line represents the variability of the mass and size of the disk. We discuss possible physical relations between the state of the disk and GeV emission under assumption that GeV flare is directly related to the decrease of the disk size.

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arXiv2013

Observations of VHE gamma-ray binaries with the MAGIC Telescopes

Several binary systems, composed of a star and a compact object, have been detected in the GeV-TeV range. Several systems have been observed but only a handful of sources have shown emission at those energies. Here, we present the observations conducted by MAGIC of different γ-ray binary systems. On one hand, we show the latest studies on the binary system LS I +61 303, which displays variability on different timescales. With the latest MAGIC observations, we will try to shed light on our understanding of this source, by presenting super-orbital and multi-wavelength studies. On the other hand, we show the observational results on the binary system HD 215227. This source has been proposed as a new γ-ray binary for being spatially coincident with the gamma-ray source AGL J2241+4454 detected by AGILE at E >100 GeV.

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arXiv2013

The NectarCAM camera project

In the framework of the next generation of Cherenkov telescopes, the Cherenkov Telescope Array (CTA), NectarCAM is a camera designed for the medium size telescopes covering the central energy range of 100 GeV to 30 TeV. NectarCAM will be finely pixelated (~ 1800 pixels for a 8 degree field of view, FoV) in order to image atmospheric Cherenkov showers by measuring the charge deposited within a few nanoseconds time-window. It will have additional features like the capacity to record the full waveform with GHz sampling for every pixel and to measure event times with nanosecond accuracy. An array of a few tens of medium size telescopes, equipped with NectarCAMs, will achieve up to a factor of ten improvement in sensitivity over existing instruments in the energy range of 100 GeV to 10 TeV. The camera is made of roughly 250 independent read-out modules, each composed of seven photo-multipliers, with their associated high voltage base and control, a read-out board and a multi-service backplane board. The read-out boards use NECTAr (New Electronics for the Cherenkov Telescope Array) ASICs which have the dual functionality of analogue memories and Analogue to Digital Converter (ADC). The camera trigger to be used will be flexible so as to minimize the read-out dead-time of the NECTAr chips. We present the camera concept and the design and tests of the various subcomponents. The design includes the mechanical parts, the cooling of the electronics, the readout, the data acquisition, the trigger, the monitoring and services.

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