8 Search Results

Neptunes represent one of the main types of exoplanets and have chemical-physical characteristics halfway between rocky and gas giant planets. Therefore, their characterization is important for understanding and constraining both the formation mechanisms and the evolution patterns of planets. We investigate the exoplanet candidate TOI-1422 b, which was discovered by the TESS space telescope around the high proper-motion G2 V star TOI-1422 (V = 10.6 mag), 155 pc away, with the primary goal of confirming its planetary nature and characterising its properties. We monitored TOI-1422 with the HARPS-N spectrograph for 1.5 yr to precisely quantify its radial velocity (RV) variation.more » We analyse these RV measurements jointly with TESS photometry and check for blended companions through high-spatial resolution images using the AstraLux instrument. We estimate that the parent star has a radius of R$$_\star$$ = 1.019_-0.013^+0.014 R_⊙, and a mass of M$$_\star$$ = 1.019_-0.013^+0.014 M_⊙. Our analysis confirms the planetary nature of TOI-1422 b and also suggests the presence of a Neptune-mass planet on a more distant orbit, the candidate TOI-1422 c, which is not detected in TESS light curves. The inner planet, TOI-1422 b, orbits on a period of P_b = 12.9972 ± 0.0006 days and has an equilibrium temperature of T_eq,b = 867 ± 17 K. With a radius of R_b = 3.96_-0.11^+0.13 R_⊕, a mass of M_b = 9.0_-2.0^+2.3 M_⊕ and, consequently, a density of ρ_b = 0.795_-0.235^+0.290g cm^-3, it can be considered a warm Neptune-sized planet. Compared to other exoplanets of a similar mass range, TOI-1422 b is among the most inflated, and we expect this planet to have an extensive gaseous envelope that surrounds a core with a mass fraction around 10% – 25% of the total mass of the planet. The outer non-transiting planet candidate, TOI-1422 c, has an orbital period of P_c = 29.29_-0.20^+0.21 days, a minimum mass, M_csin i, of 11.1_-2.3^+2.6 M_⊕, an equilibrium temperature of T_eq,c = 661 ± 13 K and, therefore, if confirmed, could be considered as another warm Neptune.« less

ABSTRACT We present a precise characterization of the TOI-561 planetary system obtained by combining previously published data with TESS and CHEOPS photometry, and a new set of 62 HARPS-N radial velocities (RVs). Our joint analysis confirms the presence of four transiting planets, namely TOI-561 b (P = 0.45 d, R = 1.42 R⊕, M = 2.0 M⊕), c (P = 10.78 d, R = 2.91 R⊕, M = 5.4 M⊕), d (P = 25.7 d, R = 2.82 R⊕, M = 13.2 M⊕), and e (P = 77 d, R = 2.55 R⊕, M = 12.6 R⊕). Moreover, we identify an additional, long-period signal (>450 d) in the RVs, which could be duemore » to either an external planetary companion or to stellar magnetic activity. The precise masses and radii obtained for the four planets allowed us to conduct interior structure and atmospheric escape modelling. TOI-561 b is confirmed to be the lowest density (ρb = 3.8 ± 0.5 g cm−3) ultra-short period (USP) planet known to date, and the low metallicity of the host star makes it consistent with the general bulk density-stellar metallicity trend. According to our interior structure modelling, planet b has basically no gas envelope, and it could host a certain amount of water. In contrast, TOI-561 c, d, and e likely retained an H/He envelope, in addition to a possibly large water layer. The inferred planetary compositions suggest different atmospheric evolutionary paths, with planets b and c having experienced significant gas loss, and planets d and e showing an atmospheric content consistent with the original one. The uniqueness of the USP planet, the presence of the long-period planet TOI-561 e, and the complex architecture make this system an appealing target for follow-up studies.« less

In this paper, we present the results of the spectroscopic and photometric monitoring campaign of ASASSN-15ed. The transient was discovered quite young by the All Sky Automated Survey for SuperNovae (ASAS-SN) survey. Amateur astronomers allowed us to sample the photometric SN evolution around maximum light, which we estimate to have occurred on JD = 2457087.4 ± 0.6 in the r band. Its apparent r-band magnitude at maximum was r = 16.91 ± 0.10, providing an absolute magnitude Mr ≈ -20.04 ± 0.20, which is slightly more luminous than the typical magnitudes estimated for Type Ibn SNe. The post-peak evolution wasmore » well monitored, and the decline rate (being in most bands around 0.1 mag d^-1 during the first 25 d after maximum) is marginally slower than the average decline rates of SNe Ibn during the same time interval. The object was initially classified as a Type Ibn SN because early-time spectra were characterized by a blue continuum with superimposed narrow P-Cygni lines of He I, suggesting the presence of a slowly moving (1200–1500 km s^-1), He-rich circumstellar medium. Later on, broad P-Cygni He I lines became prominent. The inferred velocities, as measured from the minimum of the broad absorption components, were between 6000 and 7000 km s^-1. Lastly, as we attribute these broad features to the SN ejecta, this is the first time we have observed the transition of a Type Ibn SN to a Type Ib SN.« less

Here we report photometric and spectroscopic observations of the optical transient LSQ13zm. Historical data reveal the presence of an eruptive episode (that we label as ‘2013a’) followed by a much brighter outburst (‘2013b’) three weeks later, that we argue to be the genuine supernova explosion. This sequence of events closely resemble those observed for SN 2010mc and (in 2012) SN 2009ip. Furthermore, the absolute magnitude reached by LSQ13zm during 2013a (MR = -14.87 ± 0.25 mag) is comparable with those of supernova impostors, while that of the 2013b event (M_R = -18.46 ± 0.21 mag) is consistent with those ofmore » interacting supernovae. Our spectra reveal the presence of a dense and structured circumstellar medium, probably produced through numerous pre-supernova mass-loss events. In addition, we find evidence for high-velocity ejecta, with a fraction of gas expelled at more than 20 000 km s^-1. The spectra of LSQ13zm show remarkable similarity with those of well-studied core-collapse supernovae. From the analysis of the available photometric and spectroscopic data, we conclude that we first observed the last event of an eruptive sequence from a massive star, likely a Luminous Blue Variable, which a short time later exploded as a core-collapse supernova. Our detailed analysis of archival images suggests that the host galaxy is a star-forming Blue Dwarf Compact Galaxy.« less

The production of $π^+$, $π^–$, $$\hbox{K}^+$$, $$\hbox{K}^–$$, $$p$$, and $$\overline p$$ at mid-rapidity has been measured in proton-proton collisions at $$\sqrt{s}$$ = 900 GeV with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum ($$p_t$$) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges,more » the results are combined to extract spectra from $$p_t$$=100 MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean $$p_t$$ are compared with previous measurements, and the trends as a function of collision energy are discussed.« less

The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy $$\sqrt{s}=7$$ TeV, were measured in the central pseudorapidity region |η| < 1. Comparisons are made with previous measurements at $$\sqrt{s}=0.9$$ TeV and 2.36 TeV. At $$\sqrt{s}=7$$ TeV, for events with at least one charged particle in |η| < 1, we obtain dN_ch/dη = 6.01 ± 0.01(stat.)$$\mathbb +0.20\atop{-0.12} $$(syst.). This corresponds to an increase of 57.6% ± 0.4%(stat.)$$\mathbb +3.6\atop{-1.8} $$(syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV ismore » described fairly well by the negative binomial distribution.« less

Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range |η|<1.4. In the central region (|η|<0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density dNch/dη= 3.02 ± 0.01 (stat.)$$ +0.08\atop{-0.05} $$(syst.) for inelastic interactions, and dN_ch/dη = 3.58 ± 0.01 (stat.)$$ +0.12\atop{-0.12} $$(syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dN_ch/dη = 3.77 ± 0.01 (stat.)$$ +0.25\atop{-0.12} $$(syst.) for inelastic, and dN_ch/dη = 4.43 ± 0.01(stat.)$$ +0.17\atop{-0.12} $$(syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to highermore » energy is 24.7% ± 0.5%(stat.)$$ +5.7\atop{-2.8} $$%(syst.) for inelastic and 23.7% ± 0.5%(stat.)$$ +4.6\atop{-1.1} $$% 1.1%(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions.« less

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with themore » two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|<0.5, we obtain dN_ch/dη=3. 10±0. 13(stat.)±0.22(syst.) for all inelastic interactions, and dN_ch/dη=3.51±0. 15(stat.)±0. 25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN Sp$$\bar{p}$$S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.« less