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Carles Badenes

Publications and source records attributed to Carles Badenes.

At least 55 records · Page 3Linked to original sources
arXiv2021

The RR Lyrae Delay-Time Distribution: A Novel Perspective on Models of Old Stellar Populations

The delay-time distribution (DTD) is the occurrence rate of a class of objects as a function of time after a hypothetical burst of star formation. DTDs are mainly used as a statistical test of stellar evolution scenarios for supernova progenitors, but they can be applied to many other classes of astronomical objects. We calculate the first DTD for RR Lyrae variables using 29,810 RR Lyrae from the OGLE-IV survey and a map of the stellar-age distribution (SAD) in the Large Magellanic Cloud (LMC). We find that $\sim 46\%$ of the OGLE-IV RR Lyrae are associated with delay-times older than 8 Gyr (main-sequence progenitor masses less than 1 M$_{\odot}$), and consistent with existing constraints on their ages, but surprisingly about $51\%$ of RR Lyrae appear have delay times $1.2-8$ Gyr (main-sequence masses between $1 - 2$ M$_{\odot}$ at LMC metallicity). This intermediate-age signal also persists outside the Bar-region where crowding is less of a concern, and we verified that without this signal, the spatial distribution of the OGLE-IV RR Lyrae is inconsistent with the SAD map of the LMC. Since an intermediate-age RR Lyrae channel is in tension with the lack of RR Lyrae in intermediate-age clusters (noting issues with small-number statistics), and the age-metallicity constraints of LMC stars, our DTD result possibly indicates that systematic uncertainties may still exist in SAD measurements of old-stellar populations, perhaps stemming from the construction methodology or the stellar evolution models used. We described tests to further investigate this issue.

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arXiv2020

Analysis of Previously Classified White Dwarf-Main Sequence Binaries Using Data from the APOGEE Survey

We present analyses of near-infrared, spectroscopic data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey for 45 previously confirmed or candidate white dwarf-main sequence (WDMS) binaries identified by the optical SDSS and LAMOST surveys. Among these 45 systems, we classify three as having red giant primaries in the LAMOST sample and fourteen to be young stellar object contaminants in the photometrically identified SDSS sample. From among the subsample of 28 systems that we confirm to have MS primaries, we derive and place limits on orbital periods and velocity amplitudes for fourteen. Seven systems have significant velocity variations that warrant a post-common-envelope (PCE) binary classification -- four of which are newly classified, three of which are newly confirmed, and five for which we can derive full orbital parameters. If confirmed, one of these newly discovered systems (2M14544500+4626456) will have the second longest orbital period reported for a typical, compact PCE WDMS binary ($P=15.1$ days). In addition to the seven above, we also recover and characterize with APOGEE data the well known PCE WDMS systems EG UMa and HZ 9. We also investigate the overall metallicity distribution of the WDMS sample, which is a parameter space not often explored for these systems. Of note, we find one system (2M14244053+4929580) to be extremely metal-poor (${\rm [Fe/H]}=-1.42$) relative to the rest of the near-solar sample. Additionally, the PCE systems in our sample are found to be, on average, higher in metallicity than their wide-binary counterparts, though we caution that with this small number of systems, the sample may not be representative of the overall distribution of WDMS systems.

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arXiv2020

The delay time distribution of supernovae from integral-field spectroscopy of nearby galaxies

Constraining the delay-time distribution (DTD) of different supernova (SN) types can shed light on the timescales of galaxy chemical enrichment and feedback processes affecting galaxy dynamics, and SN progenitor properties. Here, we present an approach to recover SN DTDs based on integral field spectroscopy (IFS) of their host galaxies. Using a statistical analysis of a sample of 116 supernovae in 102 galaxies, we evaluate different DTD models for SN types Ia (73), II (28) and Ib/c (15). We find the best SN Ia DTD fit to be a power law with an exponent $α= -1.1\pm 0.3$ (50\% confidence interval), and a time delay (between star formation and the first SNe) $Δ= 50^{+100}_{-35}~Myr$ (50\% C.I.). For core collapse (CC) SNe, both of the Zapartas et al. (2017) DTD models for single and binary stellar evolution are consistent with our results. For SNe II and Ib/c, we find a correlation with a Gaussian DTD model with $σ= 82^{+129}_{-23}~Myr$ and $σ= 56^{+141}_{-9}~Myr$ (50\% C.I.) respectively. This analysis demonstrates that integral field spectroscopy opens a new way of studying SN DTD models in the local universe.

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arXiv2020

Geometry of the Draco C1 Symbiotic Binary

Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion -- likely a white dwarf -- belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provide updated stellar parameters for the cool, giant component, and constrain the temperature and mass of the hot, compact companion. Prior measurements of the periodicity of the system, based on only a few epochs of radial velocity data or relatively short baseline photometric observations, were sufficient only to place lower limits on the orbital period ($P > 300$ days). For the first time, we report precise orbital parameters for the binary system: With 43 radial velocity measurements from APOGEE spanning an observational baseline of more than 3 years, we definitively derive the period of the system to be $1220.0^{+3.7}_{-3.5}$ days. Based on the newly derived orbital period and separation of the system, together with estimates of the radius of the red giant star, we find that the hot companion must be accreting matter from the dense wind of its evolved companion.

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arXiv2020

The Close Binary Fraction as a Function of Stellar Parameters in APOGEE: A Strong Anti-Correlation With $α$ Abundances

We use observations from the APOGEE survey to explore the relationship between stellar parameters and multiplicity. We combine high-resolution repeat spectroscopy for 41,363 dwarf and subgiant stars with abundance measurements from the APOGEE pipeline and distances and stellar parameters derived using \textit{Gaia} DR2 parallaxes from \cite{Sanders2018} to identify and characterise stellar multiples with periods below 30 years, corresponding to \drvm$\gtrsim$ 3 \kms, where \drvm\ is the maximum APOGEE-detected shift in the radial velocities. Chemical composition is responsible for most of the variation in the close binary fraction in our sample, with stellar parameters like mass and age playing a secondary role. In addition to the previously identified strong anti-correlation between the close binary fraction and \feh\, we find that high abundances of $α$ elements also suppress multiplicity at most values of \feh\ sampled by APOGEE. The anti-correlation between $α$ abundances and multiplicity is substantially steeper than that observed for Fe, suggesting C, O, and Si in the form of dust and ices dominate the opacity of primordial protostellar disks and their propensity for fragmentation via gravitational stability. Near \feh{} = 0 dex, the bias-corrected close binary fraction ($a<10$ au) decreases from $\approx$ 100 per cent at \alh{} = $-$0.2 dex to $\approx$ 15 per cent near \alh{} = 0.08 dex, with a suggestive turn-up to $\approx$20 per cent near \alh{} = 0.2. We conclude that the relationship between stellar multiplicity and chemical composition for sun-like dwarf stars in the field of the Milky Way is complex, and that this complexity should be accounted for in future studies of interacting binaries.

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arXiv2020

Evidence of a Type Ia Progenitor for Supernova Remnant 3C 397

The explosive origin of the young supernova remnant (SNR) 3C 397 (G41.1-0.3) is debated. Its elongated morphology and proximity to a molecular cloud are suggestive of a core-collapse (CC) SN origin, yet recent X-ray studies of heavy metals show chemical yields and line centroid energies consistent with a Type Ia SN. In this paper, we analyze the full X-ray spectrum from 0.7-10 keV of 3C 397 observed with Suzaku and compare the line centroid energies, fluxes, and elemental abundances of intermediate-mass and heavy metals (Mg to Ni) to Type Ia and CC hydrodynamical model predictions. Based on the results, we conclude that 3C 397 likely arises from an energetic Type Ia explosion in a high-density ambient medium, and we show that the progenitor was a near Chandrasekhar mass white dwarf.

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arXiv2020

Response to Comment on "A Non-Interacting Low-Mass Black Hole -- Giant Star Binary System"

van den Heuvel & Tauris argue that if the red giant star in the system 2MASS J05215658+4359220 has a mass of 1 solar mass (M$_\odot$), then its unseen companion could be a binary composed of two 0.9 M$_\odot$ stars, making a triple system. We contend that the existing data are most consistent with a giant of mass $3.2^{+1.0}_{-1.0}$ M$_\odot$, implying a black hole companion of $3.3^{+2.8}_{-0.7}$ M$_\odot$.

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arXiv2020

The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra

This paper documents the sixteenth data release (DR16) from the Sloan Digital Sky Surveys; the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the southern hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey (TDSS) and new data from the SPectroscopic IDentification of ERosita Survey (SPIDERS) programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

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arXiv2020

An Ejecta Kinematics Study of Kepler's Supernova Remnant with High-Resolution $Chandra$ HETG Spectroscopy

We report our measurements of the bulk radial velocity from a sample of small, metal-rich ejecta knots in Kepler's Supernova Remnant (SNR). We measure the Doppler shift of the He-like Si K$α$ line center energy in the spectra of these knots based on our $Chandra$ High-Energy Transmission Grating Spectrometer (HETGS) observation to estimate their radial velocities. We estimate high radial velocities of up to $\sim$ 8,000 km s$^{-1}$ for some of these ejecta knots. We also measure proper motions for our sample based on the archival $Chandra$ Advanced CCD Imaging Spectrometer (ACIS) data taken in 2000, 2006, and 2014. Our measured radial velocities and proper motions indicate that some of these ejecta knots are almost freely-expanding after $\sim$ 400 years since the explosion. The fastest moving knots show proper motions up to $\sim$ 0.2 arcseconds per year. Assuming that these high velocity ejecta knots are traveling ahead of the forward shock of the SNR, we estimate the distance to Kepler's SNR $d$ $\sim$ 4.4 to 7.5 kpc. We find that the ejecta knots in our sample have an average space velocity of $ v_{s} \sim$ 4,600 km s$^{-1}$ (at a distance of 6 kpc). We note that 8 out of the 15 ejecta knots from our sample show a statistically significant (at the 90$\%$ confidence level) redshifted spectrum, compared to only two with a blueshifted spectrum. This may suggest an asymmetry in the ejecta distribution in Kepler's SNR along the line of sight, however a larger sample size is required to confirm this result.

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arXiv2020

A new and unusual LBV-like outburst from a Wolf-Rayet star in the outskirts of M33

MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AFAnd in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed around 29kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD5980 (in the SMC) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf-Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type~Ibn supernova progenitors.

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arXiv2020

A Nucleosynthetic Origin for the Southwestern Fe-rich Structure in Kepler's Supernova Remnant

{\it Chandra} X-ray observations of Kepler's supernova remnant indicate the existence of a high speed Fe-rich ejecta structure in the southwestern region. We report strong K-shell emission from Fe-peak elements (Cr, Mn, Fe, Ni), as well as Ca, in this Fe-rich structure, implying that those elements could be produced in the inner area of the exploding white dwarf. We found Ca/Fe, Cr/Fe, Mn/Fe and Ni/Fe mass ratios of 1.0--4.1\%, 1.0--4.6\%, 1--11\% and 2--30\%, respectively. In order to constrain the burning regime that could produce this structure, we compared these observed mass ratios with those in 18 one-dimensional Type Ia nucleosynthesis models (including both near-$M_{\rm Ch}$ and sub-$M_{\rm Ch}$ explosion models). The observed mass ratios agree well with those around the middle layer of incomplete Si-burning in Type Ia nucleosynthesis models with a peak temperature of $\sim$(5.0--5.3)$\times$10$^{9}$ K and a high metallicity, Z $>$ 0.0225. Based on our results, we infer the necessity for some mechanism to produce protruding Fe-rich clumps dominated by incomplete Si-burning products during the explosion. We also discuss the future perspectives of X-ray observations of Fe-rich structures in other Type Ia supernova remnants.

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arXiv2019

The Time-Domain Spectroscopic Survey: Radial Velocity Variability in Dwarf Carbon Stars

Dwarf carbon (dC) stars, main sequence stars showing carbon molecular bands, were initially thought to be an oxymoron since only AGB stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded to a white dwarf seems the most likely explanation. Indeed, a few types of giants known to show anomalous abundances --- notably, the CH, Ba and CEMP-s stars --- are known to have a high binary frequency. The dC stars may be the enhanced-abundance progenitors of most, if not all, of these systems, but this requires demonstrating a high binary frequency for dCs. Here, for a sample of 240 dC stars targeted for repeat spectroscopy by the SDSS-IV's Time Domain Spectroscopic Survey, we analyze radial velocity variability to constrain the binary frequency and orbital properties. A handful of dC systems show large velocity variability ($>$100 km s$^{-1}$). We compare the dCs to a control sample with a similar distribution of magnitude, color, proper motion, and parallax. Using MCMC methods, we use the measured $Δ$RV distribution to estimate the binary fraction and the separation distribution assuming both a unimodal and bimodal distribution. We find the dC stars have an enhanced binary fraction of 95\%, consistent with them being products of mass transfer. These models result in mean separations of less than 1 AU corresponding to periods on the order of 1 year. Our results support the conclusion that dC stars form from close binary systems via mass transfer.

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arXiv2019

Discovery of a Candidate Black Hole - Giant Star Binary System in the Galactic Field

We report the discovery of the first likely black hole in a non-interacting binary system with a field red giant. By combining radial velocity measurements from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) with photometric variability data from the All-Sky Automated Survey for Supernovae (ASAS-SN), we identified the bright rapidly-rotating giant 2MASS J05215658+4359220 as a binary system with a massive unseen companion. Subsequent radial velocity measurements reveal a system with an orbital period of 83 days and near-zero eccentricity. The photometric variability period of the giant is consistent with the orbital period, indicative of star spots and tidal synchronization. Constraints on the giant's mass and radius from its luminosity, surface gravity, and temperature imply an unseen companion with mass of $3.3^{+2.8}_{-0.7}$ M$_\odot$, indicating a low-mass black hole or an exceedingly massive neutron star. Measurement of the astrometric binary motion by {\it Gaia} will further characterize the system. This discovery demonstrates the potential of massive spectroscopic surveys like APOGEE and all-sky, high-cadence photometric surveys like ASAS-SN to revolutionize our understanding of the compact object mass function, and to test theories of binary star evolution and the supernova mechanism.

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arXiv2019

Close companions around young stars

Multiplicity is a fundamental property that is set early during stellar lifetimes, and it is a stringent probe of the physics of star formation. The distribution of close companions around young stars is still poorly constrained by observations. We present an analysis of stellar multiplicity derived from APOGEE-2 spectra obtained in targeted observations of nearby star-forming regions. This is the largest homogeneously observed sample of high-resolution spectra of young stars. We developed an autonomous method to identify double lined spectroscopic binaries (SB2s). Out of 5007 sources spanning the mass range of $\sim$0.05--1.5 \msun, we find 399 binaries, including both RV variables and SB2s. The mass ratio distribution of SB2s is consistent with a uniform for $q<0.95$ with an excess of twins with $q>0.95$. The period distribution is consistent with what has been observed in close binaries ($<10$ AU) in the evolved populations. Three systems are found to have $q\sim$0.1, with a companion located within the brown dwarf desert. There are not any strong trends in the multiplicity fraction (MF) as a function of cluster age from 1 to 100 Myr. There is a weak dependence on stellar density, with companions being most numerous at $Σ_*\sim30$ stars/pc$^{-2}$, and decreasing in more diffuse regions. Finally, disk-bearing sources are deficient in SB2s (but not RV variables) by a factor of $\sim$2; this deficit is recovered by the systems without disks. This may indicate a quick dispersal of disk material in short-period equal mass systems that is less effective in binaries with lower $q$.

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arXiv2019

Supernova Remnants in High Definition

Supernova remnants (SNRs) offer the means to study SN explosions, dynamics, and shocks at sub-parsec scales. X-ray observations probe the hot metals synthesized in the explosion and the TeV electrons accelerated by the shocks, and thus they are key to test recent, high-fidelity three-dimensional SN simulations. In this white paper, we discuss the major advances possible with X-ray spectro-imaging at arcsecond scales, with a few eV spectral resolution and a large effective area. These capabilities would revolutionize SN science, offering a three-dimensional view of metals synthesized in explosions and enabling population studies of SNRs in Local Group galaxies. Moreover, this future X-ray mission could detect faint, narrow synchrotron filaments and shock precursors that will constrain the diffusive shock acceleration process.

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arXiv2019

Catching Element Formation In The Act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.

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arXiv2019

Deep Chandra survey of the Small Magellanic Cloud. III. Formation efficiency of High-Mass X-ray binaries

We have compiled the most complete census of High-Mass X-ray Binaries (HMXBs) in the Small Magellanic Cloud with the aim to investigate the formation efficiency of young accreting binaries in its low metallicity environment. In total, we use 127 X-ray sources with detections in our \chandra X-ray Visionary Program (XVP), supplemented by 14 additional (likely and confirmed) HMXBs identified by \cite{2016A&A...586A..81H} that fall within the XVP area, but are not either detected in our survey (9 sources) or matched with any XVP source that has at least one OB counterpart in the OGLE-III catalog (5 sources). Specifically, we examine the number ratio of the HMXBs [N(HMXBs)] to {\it (a)} the number of OB stars, {\it (b)} the local star-formation rate (SFR), and {\it (c)} the stellar mass produced during the specific star-formation burst, all as a function of the age of their parent stellar populations. Each of these indicators serves a different role, but in all cases we find that the HMXB formation efficiency increases as a function of time (following a burst of star formation) up to $\sim$40--60\,Myr, and then gradually decreases. The peak formation efficiency N(HMXB)/SFR is (49 $\pm$ 14) $[10^{-5}~{\rm M_{\odot}/yr}]^{-1}$, in good agreement with previous estimates of the average formation efficiency in the broad $\sim$20--60\,Myr age range. The frequency of HMXBs is a factor of 8$\times$ higher than at $\sim$10\,Myr, and 4$\times$ higher than at $\sim$260\,Myr, i.e. at earlier and later epochs, respectively.

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