Luca Di Fabrizio - Academia.edu (original) (raw)

Papers by Luca Di Fabrizio

Research paper thumbnail of K2-79b and K2-222b: Mass Measurements of Two Small Exoplanets with Periods beyond 10 days that Overlap with Periodic Magnetic Activity Signals

The Astronomical Journal, 2022

We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting... more We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day orbital periods fall near periods of signals induced by stellar magnetic activity. The two signals might therefore interfere and lead to an inaccurate estimate of exoplanet mass. We present a method to mitigate these effects when radial velocity (RV) and activity-indicator observations are available over multiple observing seasons and the orbital period of the exoplanet is known. We perform correlation and periodogram analyses on subsets composed of each target's two observing seasons, in addition to the full data sets. For both targets, these analyses reveal an optimal season with little to no interference at the orbital period of the known exoplanet. We make a confident mass detection of each exoplanet by confirming agreement between fits to the full RV set and the optimal season. For K2-79b...

Research paper thumbnail of TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley

The Astronomical Journal, 2021

Studies of close-in planets orbiting M dwarfs have suggested that the M dwarf radius valley may b... more Studies of close-in planets orbiting M dwarfs have suggested that the M dwarf radius valley may be well-explained by distinct formation timescales between enveloped terrestrials, and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally-driven mass loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition's dependence on orbital separation such that studying the compositions of planets within the M dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short period planet TOI-1634 b (P = 0.989 days, F = 121F ⊕ , r p = 1.790 +0.080 −0.081 R ⊕) orbiting a nearby M2 dwarf (K s = 8.7, R s = 0.450 R , M s = 0.502 M) and whose size and orbital period sit within the M dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of 4.91 +0.68 −0.70 M ⊕ , which makes TOI-1634 b inconsistent with an Earth-like composition at 5.9σ and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky composition that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of the Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with M s 0.5 M .

Research paper thumbnail of LRS: ARC Software Specification Description

The purpose of this document is to provide to the SW developers all necessary information to mana... more The purpose of this document is to provide to the SW developers all necessary information to manage the CCD readout hardware (ARC controller) and to build the acquisition system for the Low Resolution Spectrograph (LRS) at the TNG.

Research paper thumbnail of Variable stars in the bar of the Large Magellanic Cloud: the photometric catalogue

The catalogue of the Johnson-Cousins B,V and I light curves obtained for 162 variable stars (135 ... more The catalogue of the Johnson-Cousins B,V and I light curves obtained for 162 variable stars (135 RR Lyrae, 4 candidate Anomalous Cepheids, 11 Classical Cepheids, 11 eclipsing binaries and 1 delta Scuti star) in two areas close to the bar of the Large Magellanic Cloud is presented along with coordinates, finding charts, periods, epochs, amplitudes, and mean quantities (intensity- and magnitude-averaged luminosities) of the variables with full coverage of the light variations. A star by star comparison is made with MACHO and OGLE II photometries based on both variable and constant stars in common, and the transformation relationships to our photometry are provided. The pulsation properties of the RR Lyrae stars in the sample are discussed in detail. Parameters of the Fourier decomposition of the light curves are derived for the fundamental mode RR Lyrae stars with complete and regular curves (29 stars). They are used to estimate metallicities, absolute magnitudes, intrinsic (B-V)o col...

Research paper thumbnail of DRAFT- submitted to AJ LUMINOSITIES AND PULSATIONAL PROPERTIES OF RR LYRAE VARIABLES IN THE BAR OF THE LARGE MAGELLANIC CLOUD 1

New B,V CCD photometry in the standard Johnson system is presented for two 13 ′ × 13 ′ fields (la... more New B,V CCD photometry in the standard Johnson system is presented for two 13 ′ × 13 ′ fields (later referred to as ”field A ” and ”field B”) located close to the bar of the LMC and partially overlapping with fields #6 and #13 of the MACHO microlensing experiment. We detected 128 RR Lyrae variables in the two areas and obtained full coverage of the B and V light curves for 93 and 107 variables, respectively, among which 9 double-mode pulsators (RRd’s). The average apparent luminosity of the single-mode RR Lyrae’s with complete V and B light curves is < V(RR)> = 19.352±0.023 (52 stars) and < B(RR)> = 19.762 ± 0.023 (48 stars) in field A, and < V(RR)> = 19.314 ± 0.025 (41 stars) and < B(RR)> = 19.656 ± 0.030 in field B (33 stars). The average apparent luminosity of the clump stars in the same fields is ∼ 0.12 mag brighter than the RR Lyrae level (< Vclump> = 19.223 ± 0.003 and 19.200±0.003, in field A (5345 stars) and B (3639 stars), respectively). An est...

Research paper thumbnail of Pulsating Variable Stars in the Coma Berenices dwarf spheroidal galaxy 1

We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint ... more We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint Milky Way satellite, recently discovered by the Sloan Digital Sky Survey. We have obtained V, B − V and V, V − I color-magnitude diagrams that reach V ∼ 23.0−23.2 mag showing the galaxy turnoff at V ∼ 21.7 mag, and have performed the first study of the variable star population of this new Milky Way companion. Two RR Lyrae stars (a fundamental-mode-RRaband a first overtone-RRc- pulsator) and a short period variable with period P=0.12468 days were identified in the galaxy. The RRab star has a rather long period of Pab = 0.66971 days and is about 0.2 mag brighter than the RRc variable and other non-variable stars on the galaxy horizontal branch. In the period-amplitude diagram the RRab variable falls closer to the loci of Oosterhoff 1 Based on data collected at the 1.52 m telescope of the INAF-Osservatorio Astronomico di Bologna,

Research paper thumbnail of Variable stars in the bar of the Large Magellanic Cloud: the

Research paper thumbnail of Outflows and jets from low mass protostars in Bok globules: the case of CB230

We have been investigating the low-mass star forming process in the Bok globule CB230 through NIR... more We have been investigating the low-mass star forming process in the Bok globule CB230 through NIR and mm wavelengths observations. A bright hot jet component emanating from a deeply embedded YSO has been found in the 1.64 μm line of [FeII], suggesting the presence of dissociative J-type shocks. The jet is composed of two well-defined knots and is located at the base of a larger scale, cold, molecular outflow. The [FeII] emission has been confirmed by the detection of several bright lines towards the jet as well as towards the driving YSO. These results allow us to investigate how the mass loss activity from YSOs affects the high-density medium hosting the newly-born low-mass stars.

Research paper thumbnail of On the remote Galactic Globular Cluster NGC 2419 1

We present a new, deep (V ∼ 26) study of the Galactic globular cluster NGC 2419 based on B, V, I ... more We present a new, deep (V ∼ 26) study of the Galactic globular cluster NGC 2419 based on B, V, I time-series CCD photometry over about 10 years and extending beyond the cluster published tidal radius. We have identified 101 variable stars of which 60 are new discoveries, doubling the known RR Lyrae stars and including 12 SX Phoenicis stars. The average period of the RR Lyrae stars (〈Pab〉=0.662 d, and 〈Pc〉=0.366 d, for fundamental-mode −RRab − and first-overtone pulsators, respectively), and the position in the period-amplitude diagram both confirm that NGC 2419 is an Oosterhoff II cluster. The average apparent magnitude of the RR Lyrae stars is 〈V〉=20.31±0.01 (σ=0.06, 67 stars) and leads to the distance modulus µ0=19.60 ± 0.05. The Color-Magnitude Diagram, reaching about 2.6 mag below the cluster turn-off, does not show clear evidence of multiple stellar populations. Cluster stars are found until r ∼ 10.5 ′, and possibly as far as r ∼ 15 ′ , suggesting that the literature tidal radi...

Research paper thumbnail of Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX

The Astrophysical Journal

We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We d... more We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (T eq ∼4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R∼115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask crosscorrelation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84±14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10 −3-10 −5 bar level.

Research paper thumbnail of The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations

Astronomy and Astrophysics, 2008

Context. To investigate the earliest phases of star formation and study how newly-born stars inte... more Context. To investigate the earliest phases of star formation and study how newly-born stars interact with the surrounding medium, we performed a line and continuum survey at NIR and mm-wavelengths of a sample of relatively isolated Bok globules. Aims. We present a follow-up observational program of a star-forming site in the globule CB230. From narrow-band continuum observations of this site, we had discovered a bright [FeII] jet, which originates in the low-mass YSO CB230-A. We aim to investigate the physical properties of the region from where the jet is launched. Methods. Our analysis was carried out using low-resolution NIR spectra acquired with the camera NICS at the TNG telescope, with JH and HK grisms and a 1 arcsec-wide slit. These observational data were complemented with infrared photometric data from the Spitzer space telescope archive. Results. The relevant physical properties of CB230-A were constrained by SED fitting of fluxes from the NIR to the mm. The YSO spectrum exhibits a significant number of atomic and molecular emission lines and absorption features. The characteristics of this spectrum suggest that we are observing a region in the close vicinity of CB230-A, i. e. its photosphere and/or an active accretion disk. The spectra of the knots in the jet contain a large number of emission lines, including a rich set of [FeII] lines. Emission due to H 2 and [FeII] are not spatially correlated, confirming that [FeII] and H 2 are excited by different mechanisms, in agreement with the models where [FeII] traces dissociative J-shocks and molecular hydrogen traces slower C-shocks. By using intensity ratios involving density-sensitive [FeII] lines, we estimated the electron densities along the jet to be 6 × 10 3-1 × 10 4 cm −3. This indicates either high density post-shock regions of ionised gas or regions with a high degree of ionisation. Conclusions. By combining the present data with previously obtained maps at NIR-and mm-wavelengths, the emerging scenario is that CB230-A is a Class 0/I YSO driving an atomic jet that is observed to be almost monopolar probably due to its inclination to the plane of the sky and the resulting higher extinction of its red side. This primary jet appears to be sufficiently energetic to open the cavity visible in the NIR images and drive the large-scale molecular outflow observed at mm-wavelengths. CB230-A was revealed to be a good location to test the innermost structure of accreting low-mass protostars.

Research paper thumbnail of The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations

Astronomy and Astrophysics, 2008

Context. To investigate the earliest phases of star formation and study how newly-born stars inte... more Context. To investigate the earliest phases of star formation and study how newly-born stars interact with the surrounding medium, we performed a line and continuum survey at NIR and mm-wavelengths of a sample of relatively isolated Bok globules. Aims. We present a follow-up observational program of a star-forming site in the globule CB230. From narrow-band continuum observations of this site, we had discovered a bright [FeII] jet, which originates in the low-mass YSO CB230-A. We aim to investigate the physical properties of the region from where the jet is launched. Methods. Our analysis was carried out using low-resolution NIR spectra acquired with the camera NICS at the TNG telescope, with JH and HK grisms and a 1 arcsec-wide slit. These observational data were complemented with infrared photometric data from the Spitzer space telescope archive. Results. The relevant physical properties of CB230-A were constrained by SED fitting of fluxes from the NIR to the mm. The YSO spectrum exhibits a significant number of atomic and molecular emission lines and absorption features. The characteristics of this spectrum suggest that we are observing a region in the close vicinity of CB230-A, i. e. its photosphere and/or an active accretion disk. The spectra of the knots in the jet contain a large number of emission lines, including a rich set of [FeII] lines. Emission due to H 2 and [FeII] are not spatially correlated, confirming that [FeII] and H 2 are excited by different mechanisms, in agreement with the models where [FeII] traces dissociative J-shocks and molecular hydrogen traces slower C-shocks. By using intensity ratios involving density-sensitive [FeII] lines, we estimated the electron densities along the jet to be 6 × 10 3-1 × 10 4 cm −3. This indicates either high density post-shock regions of ionised gas or regions with a high degree of ionisation. Conclusions. By combining the present data with previously obtained maps at NIR-and mm-wavelengths, the emerging scenario is that CB230-A is a Class 0/I YSO driving an atomic jet that is observed to be almost monopolar probably due to its inclination to the plane of the sky and the resulting higher extinction of its red side. This primary jet appears to be sufficiently energetic to open the cavity visible in the NIR images and drive the large-scale molecular outflow observed at mm-wavelengths. CB230-A was revealed to be a good location to test the innermost structure of accreting low-mass protostars.

Research paper thumbnail of A Pair of TESS Planets Spanning the Radius Valley around the Nearby Mid-M Dwarf LTT 3780

Research paper thumbnail of Anomalous Pulsation of Field RR Lyrae Variables: Photometric and Spectroscopic Study of CM Leo, BS Com, and CU Com

International Astronomical Union Colloquium

We present results on three presumed “anomalous” RRab stars: one is found to be an RRc variable, ... more We present results on three presumed “anomalous” RRab stars: one is found to be an RRc variable, and the two others need further study.

Research paper thumbnail of Light Curves and Metal Abundances of RR Lyrae Variables in the Bar of the Large Magellanic Cloud

International Astronomical Union Colloquium

The Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance... more The Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance scale. However, a difference of 0.2−0.3 mag exists in its distance as predicted by the short and long distance scales. Distances to the LMC from Population II objects are founded on the RR Lyrae variables. We have undertaken an observational campaign devoted to the definition of the average apparent luminosity, and to the study of the mass–metallicity relation for RR Lyrae stars in the bar of the LMC. These are compared with analogous quantities for cluster RR Lyrae stars. The purpose is to see whether an intrinsic difference in luminosity, possibly due to a difference in mass, might exist between field and cluster RR Lyrae stars, which could be responsible for the well-known dichotomy between short and long distance scales. Preliminary results are presented on the V and B − V light curves, the average apparent visual magnitude, and the pulsational properties of 102 RR Lyrae stars in th...

Research paper thumbnail of Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b

Research paper thumbnail of Precise Masses in the WASP-47 System

The Astronomical Journal

We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a... more We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈ 19 hour orbit, and a Neptune in a ≈ 9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 M ⊕) and radius (1.810 ± 0.027 R ⊕) inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.

Research paper thumbnail of Distance scale, variable stars and stellar populations in Local Group galaxies

International Astronomical Union Colloquium, 2004

We present an overview of our study of the short period variable stars in the Large Magellanic Cl... more We present an overview of our study of the short period variable stars in the Large Magellanic Cloud, and in the dwarf galaxies Fornax, Leo I, and NGC 6822. Light curves are presented for RR Lyrae stars, Anomalous Cepheids and, for the first time, for Dwarf Cepheids in the field and in the globular cluster #3 of the Fornax galaxy.

Research paper thumbnail of Variable Stars in the SDSS Dwarf Spheroidal Galaxies

We present an overview of the results from our survey for variable stars in the dwarf spheroidal ... more We present an overview of the results from our survey for variable stars in the dwarf spheroidal galaxies recently discovered by the SDSS. The brightest of these new dSph&amp;amp;amp;#39;s, Canes Venatici I, has a significant number of RR Lyrae stars and is an Oosterhoff Intermediate type object, much like the majority of the traditional dSph&amp;amp;amp;#39;s. Some of the fainter SDSS

Research paper thumbnail of Berkeley 32 BVI photometry and spectroscopy (D'Orazi+, 2006)

Our data were acquired at the Italian Telescopio Nazionale Galileo, on the Canary Islands, using ... more Our data were acquired at the Italian Telescopio Nazionale Galileo, on the Canary Islands, using DOLORES (device optimized for the low resolution), a focal reducer capable of imaging and low-resolution spectroscopy, on UT 2000 November 26 and 2004 February 14. (2 data files).

Research paper thumbnail of K2-79b and K2-222b: Mass Measurements of Two Small Exoplanets with Periods beyond 10 days that Overlap with Periodic Magnetic Activity Signals

The Astronomical Journal, 2022

We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting... more We present mass and radius measurements of K2-79b and K2-222b, two transiting exoplanets orbiting active G-type stars observed with HARPS-N and K2. Their respective 10.99 day and 15.39 day orbital periods fall near periods of signals induced by stellar magnetic activity. The two signals might therefore interfere and lead to an inaccurate estimate of exoplanet mass. We present a method to mitigate these effects when radial velocity (RV) and activity-indicator observations are available over multiple observing seasons and the orbital period of the exoplanet is known. We perform correlation and periodogram analyses on subsets composed of each target's two observing seasons, in addition to the full data sets. For both targets, these analyses reveal an optimal season with little to no interference at the orbital period of the known exoplanet. We make a confident mass detection of each exoplanet by confirming agreement between fits to the full RV set and the optimal season. For K2-79b...

Research paper thumbnail of TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley

The Astronomical Journal, 2021

Studies of close-in planets orbiting M dwarfs have suggested that the M dwarf radius valley may b... more Studies of close-in planets orbiting M dwarfs have suggested that the M dwarf radius valley may be well-explained by distinct formation timescales between enveloped terrestrials, and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally-driven mass loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition's dependence on orbital separation such that studying the compositions of planets within the M dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short period planet TOI-1634 b (P = 0.989 days, F = 121F ⊕ , r p = 1.790 +0.080 −0.081 R ⊕) orbiting a nearby M2 dwarf (K s = 8.7, R s = 0.450 R , M s = 0.502 M) and whose size and orbital period sit within the M dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of 4.91 +0.68 −0.70 M ⊕ , which makes TOI-1634 b inconsistent with an Earth-like composition at 5.9σ and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky composition that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of the Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with M s 0.5 M .

Research paper thumbnail of LRS: ARC Software Specification Description

The purpose of this document is to provide to the SW developers all necessary information to mana... more The purpose of this document is to provide to the SW developers all necessary information to manage the CCD readout hardware (ARC controller) and to build the acquisition system for the Low Resolution Spectrograph (LRS) at the TNG.

Research paper thumbnail of Variable stars in the bar of the Large Magellanic Cloud: the photometric catalogue

The catalogue of the Johnson-Cousins B,V and I light curves obtained for 162 variable stars (135 ... more The catalogue of the Johnson-Cousins B,V and I light curves obtained for 162 variable stars (135 RR Lyrae, 4 candidate Anomalous Cepheids, 11 Classical Cepheids, 11 eclipsing binaries and 1 delta Scuti star) in two areas close to the bar of the Large Magellanic Cloud is presented along with coordinates, finding charts, periods, epochs, amplitudes, and mean quantities (intensity- and magnitude-averaged luminosities) of the variables with full coverage of the light variations. A star by star comparison is made with MACHO and OGLE II photometries based on both variable and constant stars in common, and the transformation relationships to our photometry are provided. The pulsation properties of the RR Lyrae stars in the sample are discussed in detail. Parameters of the Fourier decomposition of the light curves are derived for the fundamental mode RR Lyrae stars with complete and regular curves (29 stars). They are used to estimate metallicities, absolute magnitudes, intrinsic (B-V)o col...

Research paper thumbnail of DRAFT- submitted to AJ LUMINOSITIES AND PULSATIONAL PROPERTIES OF RR LYRAE VARIABLES IN THE BAR OF THE LARGE MAGELLANIC CLOUD 1

New B,V CCD photometry in the standard Johnson system is presented for two 13 ′ × 13 ′ fields (la... more New B,V CCD photometry in the standard Johnson system is presented for two 13 ′ × 13 ′ fields (later referred to as ”field A ” and ”field B”) located close to the bar of the LMC and partially overlapping with fields #6 and #13 of the MACHO microlensing experiment. We detected 128 RR Lyrae variables in the two areas and obtained full coverage of the B and V light curves for 93 and 107 variables, respectively, among which 9 double-mode pulsators (RRd’s). The average apparent luminosity of the single-mode RR Lyrae’s with complete V and B light curves is < V(RR)> = 19.352±0.023 (52 stars) and < B(RR)> = 19.762 ± 0.023 (48 stars) in field A, and < V(RR)> = 19.314 ± 0.025 (41 stars) and < B(RR)> = 19.656 ± 0.030 in field B (33 stars). The average apparent luminosity of the clump stars in the same fields is ∼ 0.12 mag brighter than the RR Lyrae level (< Vclump> = 19.223 ± 0.003 and 19.200±0.003, in field A (5345 stars) and B (3639 stars), respectively). An est...

Research paper thumbnail of Pulsating Variable Stars in the Coma Berenices dwarf spheroidal galaxy 1

We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint ... more We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint Milky Way satellite, recently discovered by the Sloan Digital Sky Survey. We have obtained V, B − V and V, V − I color-magnitude diagrams that reach V ∼ 23.0−23.2 mag showing the galaxy turnoff at V ∼ 21.7 mag, and have performed the first study of the variable star population of this new Milky Way companion. Two RR Lyrae stars (a fundamental-mode-RRaband a first overtone-RRc- pulsator) and a short period variable with period P=0.12468 days were identified in the galaxy. The RRab star has a rather long period of Pab = 0.66971 days and is about 0.2 mag brighter than the RRc variable and other non-variable stars on the galaxy horizontal branch. In the period-amplitude diagram the RRab variable falls closer to the loci of Oosterhoff 1 Based on data collected at the 1.52 m telescope of the INAF-Osservatorio Astronomico di Bologna,

Research paper thumbnail of Variable stars in the bar of the Large Magellanic Cloud: the

Research paper thumbnail of Outflows and jets from low mass protostars in Bok globules: the case of CB230

We have been investigating the low-mass star forming process in the Bok globule CB230 through NIR... more We have been investigating the low-mass star forming process in the Bok globule CB230 through NIR and mm wavelengths observations. A bright hot jet component emanating from a deeply embedded YSO has been found in the 1.64 μm line of [FeII], suggesting the presence of dissociative J-type shocks. The jet is composed of two well-defined knots and is located at the base of a larger scale, cold, molecular outflow. The [FeII] emission has been confirmed by the detection of several bright lines towards the jet as well as towards the driving YSO. These results allow us to investigate how the mass loss activity from YSOs affects the high-density medium hosting the newly-born low-mass stars.

Research paper thumbnail of On the remote Galactic Globular Cluster NGC 2419 1

We present a new, deep (V ∼ 26) study of the Galactic globular cluster NGC 2419 based on B, V, I ... more We present a new, deep (V ∼ 26) study of the Galactic globular cluster NGC 2419 based on B, V, I time-series CCD photometry over about 10 years and extending beyond the cluster published tidal radius. We have identified 101 variable stars of which 60 are new discoveries, doubling the known RR Lyrae stars and including 12 SX Phoenicis stars. The average period of the RR Lyrae stars (〈Pab〉=0.662 d, and 〈Pc〉=0.366 d, for fundamental-mode −RRab − and first-overtone pulsators, respectively), and the position in the period-amplitude diagram both confirm that NGC 2419 is an Oosterhoff II cluster. The average apparent magnitude of the RR Lyrae stars is 〈V〉=20.31±0.01 (σ=0.06, 67 stars) and leads to the distance modulus µ0=19.60 ± 0.05. The Color-Magnitude Diagram, reaching about 2.6 mag below the cluster turn-off, does not show clear evidence of multiple stellar populations. Cluster stars are found until r ∼ 10.5 ′, and possibly as far as r ∼ 15 ′ , suggesting that the literature tidal radi...

Research paper thumbnail of Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX

The Astrophysical Journal

We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We d... more We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (T eq ∼4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R∼115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask crosscorrelation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84±14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10 −3-10 −5 bar level.

Research paper thumbnail of The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations

Astronomy and Astrophysics, 2008

Context. To investigate the earliest phases of star formation and study how newly-born stars inte... more Context. To investigate the earliest phases of star formation and study how newly-born stars interact with the surrounding medium, we performed a line and continuum survey at NIR and mm-wavelengths of a sample of relatively isolated Bok globules. Aims. We present a follow-up observational program of a star-forming site in the globule CB230. From narrow-band continuum observations of this site, we had discovered a bright [FeII] jet, which originates in the low-mass YSO CB230-A. We aim to investigate the physical properties of the region from where the jet is launched. Methods. Our analysis was carried out using low-resolution NIR spectra acquired with the camera NICS at the TNG telescope, with JH and HK grisms and a 1 arcsec-wide slit. These observational data were complemented with infrared photometric data from the Spitzer space telescope archive. Results. The relevant physical properties of CB230-A were constrained by SED fitting of fluxes from the NIR to the mm. The YSO spectrum exhibits a significant number of atomic and molecular emission lines and absorption features. The characteristics of this spectrum suggest that we are observing a region in the close vicinity of CB230-A, i. e. its photosphere and/or an active accretion disk. The spectra of the knots in the jet contain a large number of emission lines, including a rich set of [FeII] lines. Emission due to H 2 and [FeII] are not spatially correlated, confirming that [FeII] and H 2 are excited by different mechanisms, in agreement with the models where [FeII] traces dissociative J-shocks and molecular hydrogen traces slower C-shocks. By using intensity ratios involving density-sensitive [FeII] lines, we estimated the electron densities along the jet to be 6 × 10 3-1 × 10 4 cm −3. This indicates either high density post-shock regions of ionised gas or regions with a high degree of ionisation. Conclusions. By combining the present data with previously obtained maps at NIR-and mm-wavelengths, the emerging scenario is that CB230-A is a Class 0/I YSO driving an atomic jet that is observed to be almost monopolar probably due to its inclination to the plane of the sky and the resulting higher extinction of its red side. This primary jet appears to be sufficiently energetic to open the cavity visible in the NIR images and drive the large-scale molecular outflow observed at mm-wavelengths. CB230-A was revealed to be a good location to test the innermost structure of accreting low-mass protostars.

Research paper thumbnail of The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations

Astronomy and Astrophysics, 2008

Context. To investigate the earliest phases of star formation and study how newly-born stars inte... more Context. To investigate the earliest phases of star formation and study how newly-born stars interact with the surrounding medium, we performed a line and continuum survey at NIR and mm-wavelengths of a sample of relatively isolated Bok globules. Aims. We present a follow-up observational program of a star-forming site in the globule CB230. From narrow-band continuum observations of this site, we had discovered a bright [FeII] jet, which originates in the low-mass YSO CB230-A. We aim to investigate the physical properties of the region from where the jet is launched. Methods. Our analysis was carried out using low-resolution NIR spectra acquired with the camera NICS at the TNG telescope, with JH and HK grisms and a 1 arcsec-wide slit. These observational data were complemented with infrared photometric data from the Spitzer space telescope archive. Results. The relevant physical properties of CB230-A were constrained by SED fitting of fluxes from the NIR to the mm. The YSO spectrum exhibits a significant number of atomic and molecular emission lines and absorption features. The characteristics of this spectrum suggest that we are observing a region in the close vicinity of CB230-A, i. e. its photosphere and/or an active accretion disk. The spectra of the knots in the jet contain a large number of emission lines, including a rich set of [FeII] lines. Emission due to H 2 and [FeII] are not spatially correlated, confirming that [FeII] and H 2 are excited by different mechanisms, in agreement with the models where [FeII] traces dissociative J-shocks and molecular hydrogen traces slower C-shocks. By using intensity ratios involving density-sensitive [FeII] lines, we estimated the electron densities along the jet to be 6 × 10 3-1 × 10 4 cm −3. This indicates either high density post-shock regions of ionised gas or regions with a high degree of ionisation. Conclusions. By combining the present data with previously obtained maps at NIR-and mm-wavelengths, the emerging scenario is that CB230-A is a Class 0/I YSO driving an atomic jet that is observed to be almost monopolar probably due to its inclination to the plane of the sky and the resulting higher extinction of its red side. This primary jet appears to be sufficiently energetic to open the cavity visible in the NIR images and drive the large-scale molecular outflow observed at mm-wavelengths. CB230-A was revealed to be a good location to test the innermost structure of accreting low-mass protostars.

Research paper thumbnail of A Pair of TESS Planets Spanning the Radius Valley around the Nearby Mid-M Dwarf LTT 3780

Research paper thumbnail of Anomalous Pulsation of Field RR Lyrae Variables: Photometric and Spectroscopic Study of CM Leo, BS Com, and CU Com

International Astronomical Union Colloquium

We present results on three presumed “anomalous” RRab stars: one is found to be an RRc variable, ... more We present results on three presumed “anomalous” RRab stars: one is found to be an RRc variable, and the two others need further study.

Research paper thumbnail of Light Curves and Metal Abundances of RR Lyrae Variables in the Bar of the Large Magellanic Cloud

International Astronomical Union Colloquium

The Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance... more The Large Magellanic Cloud (LMC) is widely considered a corner-stone of the astronomical distance scale. However, a difference of 0.2−0.3 mag exists in its distance as predicted by the short and long distance scales. Distances to the LMC from Population II objects are founded on the RR Lyrae variables. We have undertaken an observational campaign devoted to the definition of the average apparent luminosity, and to the study of the mass–metallicity relation for RR Lyrae stars in the bar of the LMC. These are compared with analogous quantities for cluster RR Lyrae stars. The purpose is to see whether an intrinsic difference in luminosity, possibly due to a difference in mass, might exist between field and cluster RR Lyrae stars, which could be responsible for the well-known dichotomy between short and long distance scales. Preliminary results are presented on the V and B − V light curves, the average apparent visual magnitude, and the pulsational properties of 102 RR Lyrae stars in th...

Research paper thumbnail of Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b

Research paper thumbnail of Precise Masses in the WASP-47 System

The Astronomical Journal

We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a... more We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈ 19 hour orbit, and a Neptune in a ≈ 9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 M ⊕) and radius (1.810 ± 0.027 R ⊕) inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.

Research paper thumbnail of Distance scale, variable stars and stellar populations in Local Group galaxies

International Astronomical Union Colloquium, 2004

We present an overview of our study of the short period variable stars in the Large Magellanic Cl... more We present an overview of our study of the short period variable stars in the Large Magellanic Cloud, and in the dwarf galaxies Fornax, Leo I, and NGC 6822. Light curves are presented for RR Lyrae stars, Anomalous Cepheids and, for the first time, for Dwarf Cepheids in the field and in the globular cluster #3 of the Fornax galaxy.

Research paper thumbnail of Variable Stars in the SDSS Dwarf Spheroidal Galaxies

We present an overview of the results from our survey for variable stars in the dwarf spheroidal ... more We present an overview of the results from our survey for variable stars in the dwarf spheroidal galaxies recently discovered by the SDSS. The brightest of these new dSph&amp;amp;amp;#39;s, Canes Venatici I, has a significant number of RR Lyrae stars and is an Oosterhoff Intermediate type object, much like the majority of the traditional dSph&amp;amp;amp;#39;s. Some of the fainter SDSS

Research paper thumbnail of Berkeley 32 BVI photometry and spectroscopy (D'Orazi+, 2006)

Our data were acquired at the Italian Telescopio Nazionale Galileo, on the Canary Islands, using ... more Our data were acquired at the Italian Telescopio Nazionale Galileo, on the Canary Islands, using DOLORES (device optimized for the low resolution), a focal reducer capable of imaging and low-resolution spectroscopy, on UT 2000 November 26 and 2004 February 14. (2 data files).