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S. Catalan

Publications and source records attributed to S. Catalan.

At least 19 recordsLinked to original sources
arXiv2023

Continuum reverberation mapping of MCG 08-11-011

We report the results from a photometric reverberation mapping campaign carried out with the C18 telescope at the Wise Observatory from 2019 to 2020, targeting the active galactic nucleus (AGN) MCG 08-11-011. The monitoring was conducted on a daily basis with specially designed narrow-band filters, spanning from optical to near-infrared wavelengths ($\sim4000$ to $8000${\AA}) and avoiding prominent broad emission lines. We aim to measure inter-band continuum time lags, determine the size-wavelength relation, and estimate the host-subtracted AGN luminosity for this system. We used the point-spread function photometry to extract the continuum light curves and measure the inter-band time lags using several methods, including the interpolated cross-correlation function, the z-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic and photometric mode), MICA, and a multivariate correlation function. We find wavelength-dependent lags, $\tau(\lambda)$, up to $\sim$7 days between the multiband light curves of MCG 08-11-011. The observed lags are larger than predictions based on standard thin-disk theory by a factor of $\sim3-7$. We discern a significantly steeper ($\tau \propto \lambda^{4.74}$) size-wavelength relation than the $\tau \propto \lambda^{4/3}$ expected for a geometrically thin and optically thick accretion disk, which may result from the contribution of diffuse continuum emission to the flux. These results are similar to those found by previous continuum reverberation mapping campaigns.

astro-ph.GA↗
arXiv2021

Continuum reverberation mapping of the quasar PG 2130+099

We present the results of an intensive six-month optical continuum reverberation mapping campaign of the Seyfert 1 galaxy PG 2130+099 at redshift z=0.063. The ground-based photometric monitoring was conducted on a daily basis with the robotic 46cm telescope of the Wise observatory located in Israel. Specially designed narrowband filters were used to observe the central engine of the active galactic nucleus (AGN), avoiding line contamination from the broad-line region (BLR). We aim to measure inter-band continuum time lags across the optical range and determine the size-wavelength relation for this system. We used two methods, the traditional point-spread function (PSF) photometry and the recently developed proper image subtraction technique, to independently perform the extraction of the continuum light curves. The inter-band time lags are measured with several methods, including the interpolated cross-correlation function, the z-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic mode), and MICA. PG 2130+099 displays correlated variability across the optical range, and we successfully detect significant time lags of up to 3 days between the multiband light curves. Using the flux variation gradient (FVG) method, we determined the AGN's host-galaxy-subtracted rest-frame 5100{\AA} luminosity at the time of our monitoring campaign with an uncertainty of 18%. While a continuum reprocessing model can fit the data reasonably well, our derived disk sizes are a factor of 2-6 larger than the theoretical disk sizes predicted from the AGN luminosity estimate of PG 2130+099. This result is in agreement with previous studies of AGN/quasars and suggests that the standard Shakura-Sunyaev disk theory has limitations in describing AGN accretion disks.

astro-ph.GA↗
arXiv2019

The ESO supernovae type Ia progenitor survey (SPY)

Close double degenerate binaries are one of the favoured progenitor channels for type Ia supernovae, but it is unclear how many suitable systems there are in the Galaxy. We report results of a large radial velocity survey for double degenerate (DD) binaries using the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY - SPY). Exposures taken at different epochs are checked for radial velocity shifts indicating close binary systems. We observed 689 targets classified as DA (displaying hydrogen-rich atmospheres), of which 46 turned out to possess a cool companion. We measured radial velocities (RV) of the remaining 643 DA white dwarfs. We managed to secure observations at two or more epochs for 625 targets, supplemented by eleven objects meeting our selection criteria from literature. The data reduction and analysis methods applied to the survey data are described in detail. The sample contains 39 double degenerate binaries, only four of which were previously known. 20 are double-lined systems, in which features from both components are visible, the other 19 are single-lined binaries. We provide absolute RVs transformed to the heliocentric system suitable for kinematic studies. Our sample is large enough to sub-divide by mass: 16 out of 44 low mass targets (<= 0.45 Msun) are detected as DDs, while just 23 of the remaining 567 with multiple spectra and mass >0.45 Msun are double. Although the detected fraction amongst the low mass objects (36.4 +/- 7.3%) is significantly higher than for the higher-mass, carbon/oxygen-core dominated part of the sample (3.9 +/- 0.8%), it is lower than the detection efficiency based upon companion star masses >= 0.05 Msun. This suggests either companion stars of mass < 0.05 Msun, or that some of the low mass white dwarfs are single.

astro-ph.SR↗
arXiv2016

Supernova 2014J at M82: II. Direct Analysis of Spectra Obtained with Isaac Newton and William Herschel Telescopes

We analyze a time series of optical spectra of SN~2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the SYNOW code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal SNe Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si II, S II, Mg II, and Ca II. These ions persist to maximum light with the appearance of Na I and Mg I. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 days after maximum light. The +100 day identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6,000 km/s. Our results are in relatively good agreement with other analyses in the IR. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors.

astro-ph.SR↗
arXiv2016

A search for white dwarfs in the Galactic plane: the field and the open cluster population

We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope (VST) H$α$ Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compared our findings to those for other cluster white dwarfs. A white dwarf in NGC 3532 is the most massive known cluster member (1.13 M$_{\odot}$), likely with an oxygen-neon core, for which we estimate an $8.8_{-4.3}^{+1.2}$ M$_{\odot}$ progenitor, close to the mass-divide between white dwarf and neutron star progenitors. A cluster member in Ruprecht 131 is a magnetic white dwarf, whose progenitor mass exceeded 2-3 M$_{\odot}$. We stress that wider searches, and improved cluster distances and ages derived from data of the ESA Gaia mission, will advance the understanding of the mass-loss processes for low- to intermediate-mass stars.

astro-ph.SR↗
arXiv2014

The first planet detected in the WTS: an inflated hot-Jupiter in a 3.35 day orbit around a late F-star [ERRATUM]

We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope (UKIRT) in August 2007. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ~ 16 were constructed for ~60000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby-Eberly Telescope (HET) allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01 +- 0.35 Mj and a planetary radius of 1.49+0.16-0.18 Rj. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 Mj. The high irradiation from the host star ranks the planet in the pM class.

astro-ph.EP↗
arXiv2014

The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1

We present high time resolution SDSS-$g'$ and SDSS-$z'$ light curves of the primary eclipse in SDSS J141126.20+200911.1, together with time-resolved X-Shooter spectroscopy and near-infrared $JHK_{s}$ photometry. Our observations confirm the substellar nature of the companion, making SDSS J141126.20+200911.1 the first eclipsing white dwarf/brown dwarf binary known. We measure a (white dwarf model dependent) mass and radius for the brown dwarf companion of $M_{2} = 0.050 \pm 0.002$ $M_{\odot}$ and $R_{2} = 0.072 \pm 0.004$ $M_{\odot}$, respectively. The lack of a robust detection of the companion light in the $z'$-band eclipse constrains the spectral type of the companion to be later than L5. Comparing the NIR photometry to the expected white dwarf flux reveals a clear $K_s$-band excess, suggesting a spectral type in the range L7-T1. The radius measurement is consistent with the predictions of evolutionary models, and suggests a system age in excess of three Gyr. The low companion mass is inconsistent with the inferred spectral type of L7-T1, instead predicting a spectral type nearer T5. This indicates that irradiation of the companion in SDSS J1411 could be causing a significant temperature increase, at least on one hemisphere.

astro-ph.SR↗
arXiv2014

WTS-2 b: a hot Jupiter orbiting near its tidal destruction radius around a K-dwarf

We report the discovery of WTS-2 b, an unusually close-in 1.02-day hot Jupiter (Mp=1.12MJ, Rp=1.363RJ) orbiting a K2V star, which has a possible gravitationally-bound M-dwarf companion at 0.6 arcsec separation contributing ~20 percent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ~40 Myr, assuming a tidal dissipation quality factor of Q'*=10^6. Q'* is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of T_shift~17 seconds after 15 years assuming Q'*=10^6. A shift less than this would place a direct observational constraint on the lower limit of Q'* in this system. We also report a correction to the previously published expected T_shift for WASP-18 b, finding that T_shift=356 seconds after 10 years for Q'*=10^6, which is much larger than the estimated 28 seconds quoted in WASP-18 b discovery paper. We attempted to constrain Q'* via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straight-forward constraints on Q'* will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.

astro-ph.EP↗
arXiv2013

A 1500 deg$^2$ Near Infrared Proper Motion Catalogue from the UKIDSS Large Area Survey

The UKIDSS Large Area Survey (LAS) began in 2005, with the start of the UKIDSS program as a 7 year effort to survey roughly 4000 deg$^2$ at high galactic latitudes in Y, J, H and K bands. The survey also included a significant quantity of 2-epoch J band observations, with an epoch baseline greater than 2 years to calculate proper motions. We present a near infrared proper motion catalogue for the 1500 deg$^2$ of the 2 epoch LAS data, which includes 135,625 stellar sources and a further 88,324 with ambiguous morphological classifications, all with motions detected above the 5$σ$ level. We developed a custom proper motion pipeline which we describe here. Our catalogue agrees well with the proper motion data supplied for a 300 deg$^2$ subset in the current WFCAM Science Archive (WSA) tenth data release (DR10) catalogue, and in various optical catalogues, but it benefits from a larger matching radius and hence a larger upper proper motion detection limit. We provide absolute proper motions, using LAS galaxies for the relative to absolute correction. By using local 2nd order polynomial transformations, as opposed to linear transformations in the WSA, we correct better for any local distortions in the focal plane, not including the radial distortion that is removed by the UKIDSS pipeline. We present the results of proper motion searches for new brown dwarfs and white dwarfs. We discuss 41 sources in the WSA DR10 overlap with our catalogue with proper motions $>$300 $mas yr^{-1}$, several of which are new detections. We present 15 new candidate ultra-cool dwarf binary systems.

astro-ph.SR↗
arXiv2013

A spectroscopic and proper motion search of Sloan digital Sky Survey: red subdwarfs in binary systems

Red subdwarfs in binary systems are crucial for both model calibration and spectral classification. We search for red subdwarfs in binary systems from a sample of high proper motion objects with Sloan digital Sky Survey spectroscopy. We present here discoveries from this search, as well as highlight several additional objects of interest. We find 30 red subdwarfs in wide binary systems including: two with spectral type of esdM5.5, 6 companions to white dwarfs and 3 carbon enhanced red subdwarfs with normal red subdwarf companions. 15 red subdwarfs in our sample are partially resolved close binary systems. With this binary sample, we estimate the low limit of the red subdwarf binary fraction of ~ 10%. We find that the binary fraction goes down with decreasing masses and metallicities of red subdwarfs. A spectroscopic esdK7 subdwarf + white dwarf binary candidate is also reported. 30 new M subdwarfs have spectral type of >= M6 in our sample. We also derive relationships between spectral types and absolute magnitudes in the optical and near-infrared for M and L subdwarfs, and we present an M subdwarf sample with measured U, V, W space velocities.

astro-ph.GA↗
arXiv2013

Axion cooling of white dwarfs

The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

astro-ph.SR↗
arXiv2012

The impact of mergers in the mass distribution of white dwarfs

Recent surveys have allowed to derive the white dwarf mass distribution with reasonable accuracy. This distribution shows a noticeable degree of structure that it is often attributed to the evolution of close binaries in general, and to mergers in particular. To analyze if the origin of this structure can be attributed to the merger of double white dwarfs, we have used a simplified population synthesis model that retains the essential processes of formation of double degenerate binaries. Special care has been taken to avoid artifacts introduced by discontinuities in the distribution functions. Our result is that these structures are not probably due to mergers, but they can provide a deep insight on the evolution of close binary systems.

astro-ph.SR↗
arXiv2012

The first planet detected in the WTS: an inflated hot-Jupiter in a 3.35 day orbit around a late F-star

We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J=16 were constructed for 60000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby-Eberly Telescope allowed us to estimate the spectroscopic parameters of the host star, a late-F main sequence dwarf (V=16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 days, a planetary mass of 4.01+-0.35 Mj and a planetary radius of 1.49+-0.17 Rj. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 Mj.

astro-ph.EP↗
arXiv2012

The brightest pure-H ultracool white dwarf

We report the identification of LSR J0745+2627 in the United Kingdom InfraRed Telescope Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) as a cool white dwarf with kinematics and age compatible with the thick-disk/halo population. LSR J0745+2627 has a high proper motion (890 mas/yr) and a high reduced proper motion value in the J band (H_J=21.87). We show how the infrared-reduced proper motion diagram is useful for selecting a sample of cool white dwarfs with low contamination. LSR J0745+2627 is also detected in the Sloan Digital Sky Survey (SDSS) and the Wide-field Infrared Survey Explorer (WISE). We have spectroscopically confirmed this object as a cool white dwarf using X-Shooter on the Very Large Telescope. A detailed analysis of its spectral energy distribution reveals that its atmosphere is compatible with a pure-H composition model with an effective temperature of 3880+-90 K. This object is the brightest pure-H ultracool white dwarf (Teff<4000 K) ever identified. We have constrained the distance (24-45 pc), space velocities and age considering different surface gravities. The results obtained suggest that LSR J0745+2627 belongs to the thick-disk/halo population and is also one of the closest ultracool white dwarfs.

astro-ph.SR↗
arXiv2012

White dwarfs as physics laboratories: the case of axions

White dwarfs are almost completely degenerate objects that cannot obtain energy from thermonuclear sources, so their evolution is just a gravothermal cooling process. Recent improvements in the accuracy and precision of the luminosity function and in pulsational data of variable white dwarfs suggest that they are cooling faster than expected from conventional theory. In this contribution we show that the inclusion of an additional cooling term due to axions able to interact with electrons with a coupling constant g_ae ~(2-7)x10^{-13} allows to fit better the observations.

astro-ph.SR↗
arXiv2012

Discovery of the benchmark metal poor T8 dwarf BD+01 2920B

We have searched the WISE first data release for widely separated (<10,000AU) late T dwarf companions to Hipparcos and Gliese stars. We have discovered a new binary system containing a K-band suppressed T8p dwarf WISEP J1423+0116 and the mildly metal poor ([Fe/H]=-0.38+-0.06) primary BD+01 2920 (Hip 70319), a G1 dwarf at a distance of 17.2pc. This new benchmark has Teff=680+-55K and a mass of 20-50 Mjup. Its spectral properties are well modelled except for known discrepancies in the Y and K bands. Based on the well determined metallicity of its companion, the properties of BD+01 2920B imply that the currently known T dwarfs are dominated by young low-mass objects. We also present an accurate proper motion for the T8.5 dwarf WISEP J075003.84+272544.8.

astro-ph.SR↗
arXiv2010

Axions and White Dwarfs

White dwarfs are almost completely degenerate objects that cannot obtain energy from the thermonuclear sources and their evolution is just a gravothermal process of cooling. The simplicity of these objects, the fact that the physical inputs necessary to understand them are well identified, although not always well understood, and the impressive observational background about white dwarfs make them the most well studied Galactic population. These characteristics allow to use them as laboratories to test new ideas of physics. In this contribution we discuss the robustness of the method and its application to the axion case.

astro-ph.SR↗