arXiv subjects

Carlos Contreras

Publications and source records attributed to Carlos Contreras.

At least 37 records · Page 2Linked to original sources

arXiv2022

SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO-Virgo Event GW190814

On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star-black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera (DECam) on the 4m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on 8 separate nights to observe 11 candidates using the 4.1m Southern Astrophysical Research (SOAR) telescope's Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.

astro-ph.HE↗

arXiv2022

A puzzle solved after two decades: SN 2002gh among the brightest of superluminous supernovae

We present optical photometry and spectroscopy of the superluminous SN 2002gh from maximum light to $+204$ days, obtained as part of the Carnegie Type II Supernova (CATS) project. SN 2002gh is among the most luminous discovered supernovae ever, yet it remained unnoticed for nearly two decades. Using Dark Energy Camera archival images we identify the potential SN host galaxy as a faint dwarf galaxy, presumably having low metallicity, and in an apparent merging process with other nearby dwarf galaxies. We show that SN 2002gh is among the brightest hydrogen-poor SLSNe with $M_{V} = -22.40 \pm 0.02$, with an estimated peak bolometric luminosity of $2.6 \pm 0.1 \times 10^{44}$ erg s$^{-1}$. We discount the decay of radioactive nickel as the main SN power mechanism, and assuming that the SN is powered by the spin down of a magnetar we obtain two alternative solutions. The first case, is characterized by significant magnetar power leakage, and $M_{\mathrm{ej}}$ between 0.6 and 3.2 $M_{\odot}$, $P_{\mathrm{spin}} = 3.2$ ms, and $B = 5 \times 10^{13}$ G. The second case does not require power leakage, resulting in a huge ejecta mass of about 30 $M_{\odot}$, a fast spin period of $P_{\mathrm{spin}} \sim 1$ ms, and $B\sim 1.6 \times 10^{14}$ G. We estimate a zero-age main-sequence mass between 14 and 25 $M_{\odot}$ for the first case and of about 135 $M_{\odot}$ for the second case. The latter case would place the SN progenitor among the most massive stars observed to explode as a SN.

astro-ph.HE↗

arXiv2022

Soft Pomeron in the Colour Glass Condensate approach

In this paper we suggest a new approach to the structure of the soft Pomeron: based on the $t$-channel unitarity, we expressed the exchange of the soft Pomeron through the interaction of the dipole of small size of the order of $1/Q_s(Y)$ ($Q_s(Y)$ is the saturation momentum) with the hadrons. Therefore, it is shown that the typical distances in soft processes are small $r \sim 1/Q_s\Lb \h Y \Rb $, where $Y \,=\,ln s$. The saturation momentum, which determines the energy dependence of the scattering amplitude is proportional to $ Q^2_s\Lb \h Y \Rb \propto\,\exp\Lb\h λ\,Y\Rb$, with $λ\approx\,0.2$, and this behaviour is in perfect agreement with phenomenological Donnachie-Landshoff Pomeron. We demonstrate that the saturation models could describe the experimental data for $σ_{tot},σ_{el},σ_{diff} $ and $B_{el}$. Hence our approach is a good first approximation to start discussion of the soft processes in CGC approach on the solid theoretical basis.

hep-ph↗

arXiv2022

SN 2012ij: A low-luminosity type Ia supernova and evidence for continuous distribution from 91bg-like explosion to normal ones

In this paper, we present photometric and spectroscopic observations of a subluminous type Ia supernova (SN Ia) 2012ij, which has an absolute $B$-band peak magnitude $M_{B,\rm{max}}$ = $-$17.95 $\pm$ 0.15 mag. The $B$-band light curve exhibits a fast post-peak decline with $Δm_{15}(B)$ = 1.86 $\pm$ 0.05 mag. All the $R$ and $I$/$i$-band light curves show a weak secondary peak/shoulder feature at about 3 weeks after the peak, like some transitional subclass of SNe Ia, which could result from an incomplete merger of near-infrared (NIR) double peaks. The spectra are characterized by Ti~{\sc ii} and strong Si~{\sc ii} $λ$5972 absorption features that are usually seen in low-luminosity objects like SN 1999by. The NIR spectrum before maximum light reveals weak carbon absorption features, implying the existence of unburned materials. We compare the observed properties of SN 2012ij with those predicted by the sub-Chandrasekhar-mass and the Chandrasekhar-mass delayed-detonation models, and find that both optical and NIR spectral properties can be explained to some extent by these two models. By comparing the secondary maximum features in $I$ and $i$ bands, we suggest that SN 2012ij is a transitional object linking normal SNe Ia to typical 91bg-like ones. From the published sample of SNe Ia from the $Carnegie~Supernova~Project~II$ (CSP-II), we estimate that the fraction of SN 2012ij-like SNe Ia is not lower than $\sim$ 2%.

astro-ph.HE↗

arXiv2021

Non-linear evolution in the re-summed next-to-leading order of perturbative QCD:\confronting the experimental data

In this paper we compare the experimental HERA data with the next-to-leading order approach (NLO) of Ref.[C.~Contreras, E.~Levin, R.~Meneses and M.~Sanhueza,Eur. Phys. J. C 80 (2020) no.11, 1029). This approach includes the re-summed NLO corrections to the kernel of the evolution equation, the correct asymptotic behaviour in the NLO at $τ= r^2 Q^2_s \,\gg\,1$; the impact parameter dependence of the saturation scale in accord with the Froissarrt theorem as well as the non-linear corrections. In this paper, we successfully describe the experimental data with the quality, which is not worse, than in the leading order fits with larger number of the phenomenological parameters. It is demonstrated, that the data could be described, taking into account both the diffusion on $\ln(k_T)$, which stems from perturbative QCD, and the Gribov's diffusion in impact parameters. It is shown an ability to describe the data at rather large values of $α_S$.

hep-ph↗

arXiv2021

pQCD running couplings finite and monotonic in the infrared: when do they reflect the holomorphic properties of spacelike observables?

We investigate a large class of perturbative QCD (pQCD) renormalization schemes whose beta functions $β(a)$ are meromorphic functions of the running coupling and give finite positive value of the coupling $a(Q^2)$ in the infrared regime ("freezing"), $a(Q^2) \to a_0$ for $Q^2 \to 0$. Such couplings automatically have no singularities on the positive axis of the squared momenta $Q^2$ ($ \equiv -q^2$). Explicit integration of the renormalization group equation (RGE) leads to the implicit (inverted) solution for the coupling, of the form $\ln (Q^2/Q^2_{\rm in}) = {\cal H}(a)$. An analysis of this solution leads us to an algebraic algorithm for the search of the Landau singularities of $a(Q^2)$ on the first Riemann sheet of the complex $Q^2$-plane, i.e., poles and branching points (with cuts) outside the negative semiaxis. We present specific representative examples of the use of such algorithm, and compare the found Landau singularities with those seen after the 2-dimensional numerical integration of the RGE in the entire first Riemann sheet, where the latter approach is numerically demanding and may not always be precise. The specific examples suggest that the presented algebraic approach is useful to find out whether the running pQCD coupling has Landau singularities and, if yes, where precisely these singularities are.

hep-ph↗

arXiv2020

The value of the Hubble-Lemaître constant queried by Type Ia Supernovae: A journey from the Calán-Tololo Project to the Carnegie Supernova Program

We assess the robustness of the two highest rungs of the "cosmic distance ladder" for Type Ia supernovae and the determination of the Hubble-Lemaître constant. In this analysis, we hold fixed Rung 1 as the distance to the LMC determined to 1 % using Detached Eclipsing Binary stars. For Rung 2 we analyze two methods, the TRGB and Cepheid distances for the luminosity calibration of Type Ia supernovae in nearby galaxies. For Rung 3 we analyze various modern digital supernova samples in the Hubble flow, such as the Calán-Tololo, CfA, CSP, and Supercal datasets. This metadata analysis demonstrates that the TRGB calibration yields smaller $H_0$ values than the Cepheid calibration, a direct consequence of the systematic difference in the distance moduli calibrated from these two methods. Selecting the three most independent possible methodologies/bandpasses ($B$, $V$, $J$), we obtain $H_{0}=69.9 \pm 0.8$ and $H_{0} =73.5 \pm 0.7$ km s$^{-1}$ Mpc$^{-1}$ from the TRGB and Cepheid calibrations, respectively. Adding in quadrature the systematic uncertainty in the TRGB and Cepheid methods of 1.1 and 1.0 km s$^{-1}$ Mpc$^{-1}$, respectively, this subset reveals a significant 2.0 $σ$ systematic difference in the calibration of Rung 2. If Rung 1 and Rung 2 are held fixed, the different formalisms developed for standardizing the supernova peak magnitudes yield consistent results, with a standard deviation of 1.5 km s$^{-1}$ Mpc$^{-1}$, that is, Type Ia supernovae are able to anchor Rung 3 with 2 % precision. This study demonstrates that Type Ia supernovae have provided a remarkably robust calibration of R3 for over 25 years.

astro-ph.CO↗

arXiv2020

Optical and Near-Infrared Observations of the Nearby Type Ia Supernova 2017cbv

Supernova (SN) 2017cbv in NGC 5643 is one of a handful of type Ia supernovae (SNe~Ia) reported to have excess blue emission at early times. This paper presents extensive $BVRIYJHK_s$-band light curves of SN 2017cbv, covering the phase from $-16$ to $+125$ days relative to $B$-band maximum light. SN 2017cbv reached a $B$-band maximum of 11.710$\pm$0.006~mag, with a post-maximum magnitude decline $Δm_{15}(B)$=0.990$\pm$0.013 mag. The supernova suffered no host reddening based on Phillips intrinsic color, Lira-Phillips relation, and the CMAGIC diagram. By employing the CMAGIC distance modulus $μ=30.58\pm0.05$~mag and assuming $H_0$=72~$\rm km \ s^{-1} \ Mpc^{-1}$, we found that 0.73~\msun $^{56}$Ni was synthesized during the explosion of SN 2017cbv, which is consistent with estimates using reddening-free and distance-free methods via the phases of the secondary maximum of the NIR-band light curves. We also present 14 near-infrared spectra from $-18$ to $+49$~days relative to the $B$-band maximum light, providing constraints on the amount of swept-up hydrogen from the companion star in the context of the single degenerate progenitor scenario. No $Paβ$ emission feature was detected from our post-maximum NIR spectra, placing a hydrogen mass upper limit of 0.1 $M_{\odot}$. The overall optical/NIR photometric and NIR spectral evolution of SN 2017cbv is similar to that of a normal SN~Ia, even though its early evolution is marked by a flux excess no seen in most other well-observed normal SNe~Ia. We also compare the exquisite light curves of SN 2017cbv with some $M_{ch}$ DDT models and sub-$M_{ch}$ double detonation models.

astro-ph.HE↗

arXiv2020

The Carnegie Supernova Project-I: Correlation Between Type Ia Supernovae and Their Host Galaxies from Optical to Near-Infrared Bands

We present optical and near-infrared ($ugriYJH$) photometry of host galaxies of Type Ia supernovae (SN~Ia) observed by the \textit{Carnegie Supernova Project-I}. We determine host galaxy stellar masses and, for the first time, study their correlation with SN~Ia standardized luminosity across optical and near-infrared ($uBgVriYJH$) bands. In the individual bands, we find that SNe~Ia are more luminous in more massive hosts with luminosity offsets ranging between $-0.07 \pm0.03$ mag to $-0.15\pm0.04$ mag after light-curve standardization. The slope of the SN~Ia Hubble residual-host mass relation is negative across all $uBgVriYJH$ bands with values ranging between $-0.036\pm 0.025$ mag/dex to $-0.097\pm 0.027$ mag/dex -- implying that SNe~Ia in more massive galaxies are brighter than expected. The near-constant observed correlations across optical and near-infrared bands indicate that dust may not play a significant role in the observed luminosity offset--host mass correlation. We measure projected separations between SNe~Ia and their host centers, and find that SNe~Ia that explode beyond a projected 10 kpc have a $\rm 30\% \ to \ 50\%$ reduction of the dispersion in Hubble residuals across all bands -- making them a more uniform subset of SNe~Ia. Dust in host galaxies, peculiar velocities of nearby SN~Ia, or a combination of both may drive this result as the color excesses of SNe~Ia beyond 10 kpc are found to be generally lower than those interior, but there is also a diminishing trend of the dispersion as we exclude nearby events. We do not find that SN~Ia average luminosity varies significantly when they are grouped in various host morphological types. Host galaxy data from this work will be useful, in conjunction with future high-redshift samples, in constraining cosmological parameters.

astro-ph.CO↗

arXiv2020

Non-linear equation in the re-summed next-to-leading order of perturbative QCD: the leading twist approximation

In this paper, we use the re-summation procedure, suggested in Refs.\cite{DIMST,SALAM,SALAM1,SALAM2}, to fix the BFKL kernel in the NLO. However, we suggest a different way to introduce th non-linear corrections in the saturation region, which is based on the leading twist non-linear equation. In the kinematic region:$τ\,\equiv\,r^2 Q^2_s(Y)\,\leq\,1$ , where $r$ denotes the size of the dipole, $Y$ its rapidity and $Q_s$ the saturation scale, we found that the re-summation contributes mostly to the leading twist of the BFKL equation. Assuming that the scattering amplitude is small, we suggest using the linear evolution equation in this region. For $τ\,>\,1$ we are dealing with the re-summation of $\Lb \bas \,\ln τ\Rb^n$ and other corrections in NLO approximation for the leading twist.We find the BFKL kernel in this kinematic region and write the non-linear equation, which we solve analytically. We believe the new equation could be a basis for a consistent phenomenology based on the CGC approach.

hep-ph↗

arXiv2020

SN 2013aa and SN 2017cbv: Two Sibling Type Ia Supernovae in the spiral galaxy NGC 5643

We present photometric and spectroscopic observations of SN 2013aa and SN 2017cbv, two nearly identical type Ia supernovae (SNe Ia) in the host galaxy NGC 5643. The optical photometry has been obtained using the same telescope and instruments used by the Carnegie Supernova Project. This eliminates most instrumental systematics and provides light curves in a stable and well-understood photometric system. Having the same host galaxy also eliminates systematics due to distance and peculiar velocity, providing an opportunity to directly test the relative precision of SNe Ia as standard candles. The two SNe have nearly identical decline rates, negligible reddening, and remarkably similar spectra and, at a distance of $\sim 20$ Mpc, are ideal as potential calibrators for the absolute distance using primary indicators such as Cepheid variables. We discuss to what extent these two SNe can be considered twins and compare them with other supernova "siblings" in the literature and their likely progenitor scenarios. Using 12 galaxies that hosted 2 or more SNe~Ia, we find that when using SNe~Ia, and after accounting for all sources of observational error, one gets consistency in distance to 3 percent.

astro-ph.SR↗

arXiv2020

QCD Odderon: non linear evolution in the leading twist

In the paper we propose and solve analytically the non-linear evolution equation in the leading twist approximation for the Odderon contribution. We found three qualitative features of this solution, which differs the Odderon contribution from the Pomeron one :(i) the behaviour in the vicinity of the saturation scale cannot be derived from the linear evolution in a dramatic difference with the Pomeron case; (ii) a substantial decrease of the Odderon contribution with the energy; and (iii) the lack of geometric scaling behaviour. The two last features have been seen in numerical attempts to solve the Odderon equation.

hep-ph↗

arXiv2019

LSQ13ddu: A rapidly-evolving stripped-envelope supernova with early circumstellar interaction signatures

This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8$\pm$0.9 d to reach a peak brightness of $-$19.70$\pm$0.02 mag in the $\mathit{LSQgr}$ band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive $^{56}$Ni powering but can be explained through a combination of CSM interaction and an underlying $^{56}$Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.

astro-ph.HE↗

arXiv2019

The Odderon in QCD with running coupling

Starting from the leading Odderon solution of the three gluon system in perturbative QCD we introduce, as a first step towards the transition to the nonperturbative region, an infrared cutoff and use the running QCD coupling constant. In our numerical analysis we find that the fixed cut solution with intercept one persists, hinting at a physical Odderon with intercept one and a small t-slope.

hep-th↗

arXiv2019

BFKL equation in the next-to-leading order: solution at large impact parameters

In this paper, we show (i) that the NLO corrections do not change the power-like decrease of the scattering amplitude at large impact parameter ($b^2 \,>\,r^2 \exp\left( 2\bar(α}_S η(1 + 4 \barα_S)\right)$, where $r$ denotes the size of scattering dipole and $η\,=\,\ln(1/x_{Bj})$ for DIS), and, therefore, they do not resolve the inconsistency with unitarity; and (ii) they lead to an oscillating behaviour of the scattering amplitude atlarge $b$, in direct contradiction with the unitarity constraints. However, from the more practical point of view, the NLO estimates give a faster decrease of the scattering amplitude as a function of $b$, and could be very useful for description of the experimental data. It turns out, that in a limited range of $b$, the NLO corrections generates the fast decrease of the scattering amplitude with $b$, which can be parameterized as $N\, \propto\,\exp( -\,μ\,b)$ with $μ\,\propto \,1/r$ in accord with the numerical estimates in Ref.[1].

hep-ph↗

arXiv2018

Probing type Ia supernova properties using bolometric light curves from the Carnegie Supernova Project and the CfA Supernova Group

We present bolometric light curves constructed from multi-wavelength photometry of Type Ia supernovae (SNe Ia) from the Carnegie Supernova Project and the CfA Supernova Group, using near-infrared observations to provide robust constraints on host galaxy dust extinction. This set of light curves form a well-measured reference set for comparison with theoretical models. Ejected mass and synthesized $^{56}$Ni mass are inferred for each SN Ia from its bolometric light curve using a semi-analytic Bayesian light curve model, and fitting formulae provided in terms of light curve width parameters from the SALT2 and SNooPy light curve fitters. A weak bolometric width-luminosity relation is confirmed, along with a correlation between ejected mass and the bolometric light curve width. SNe Ia likely to have sub-Chandrasekhar ejected masses belong preferentially to the broad-line and cool-photosphere spectroscopic subtypes, and have higher photospheric velocities and populate older, higher-mass host galaxies than SNe Ia consistent with Chandrasekhar-mass explosions. Two peculiar events, SN 2006bt and SN 2006ot, have normal peak luminosities but appear to have super-Chandrasekhar ejected masses.

astro-ph.HE↗

arXiv2018

Carnegie Supernova Project-II: Extending the Near-Infrared Hubble Diagram for Type Ia Supernovae to $z\sim0.1$

The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a "Cosmology" sample of $\sim100$ Type Ia supernovae located in the smooth Hubble flow ($0.03 \lesssim z \lesssim 0.10$). Light curves were also obtained of a "Physics" sample composed of 90 nearby Type Ia supernovae at $z \leq 0.04$ selected for near-infrared spectroscopic time-series observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.

astro-ph.HE↗

arXiv2018

The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant

We present an analysis of the final data release of the Carnegie Supernova Project I, focusing on the absolute calibration of the luminosity-decline-rate relation for Type Ia supernovae (SNeIa) using new intrinsic color relations with respect to the color-stretch parameter, $s_{BV}$, enabling improved dust extinction corrections. We investigate to what degree the so-called fast-declining SNeIa can be used to determine accurate extragalactic distances. We estimate the intrinsic scatter in the luminosity-decline-rate relation, and find it ranges from $\pm 0.13$ mag to $\pm 0.18$ mag with no obvious dependence on wavelength. Using the Cepheid variable star data from the SH0ES project (Riess et al., 2016), the SNIa distance scale is calibrated and the Hubble constant is estimated using our optical and near-infrared sample, and these results are compared to those determined exclusively from a near-infrared sub-sample. The systematic effect of the supernova's host galaxy mass is investigated as a function of wavelength and is found to decrease toward redder wavelengths, suggesting this effect may be due to dust properties of the host. Using estimates of the dust extinction derived from optical and NIR wavelengths, and applying these to H band, we derive a Hubble constant $H_0 = 73.2 \pm 2.3$ km/s/Mpc, whereas using a simple $B-V$ color-correction applied to B band yields $H_0 = 72.7 \pm 2.1$ km/s/Mpc. Photometry of two calibrating SNeIa from the CSP-II sample, SN2012ht and SN2015F, is presented and used to improve the calibration of the SNIa distance ladder.

astro-ph.CO↗