arXiv subjects

Daniela P. Iglesias

Publications and source records attributed to Daniela P. Iglesias.

5 recordsLinked to original sources

arXiv2026

A search for circumstellar gas in pre-main-sequence debris discs using absorption spectroscopy

Gas in debris discs is thought to be either inherited from the protoplanetary stage or released from the solid, rocky content of planetesimal belts. Its presence can impact planetary atmospheres and their potential for habitability, which stresses the need to ascertain its origin and composition. Most detections to date are around main-sequence stars, with only a few gas-bearing debris discs identified around pre-main-sequence stars, mainly through millimetre CO line searches. We investigate narrow gas absorption features superimposed on the photospheric Ca II K & H and Na I D1 & D2 lines in a sample of 125 pre-main sequence and 5 relatively young (<17Myr) stars. All stars are associated with IR excess emission indicative of presence of a debris disc. By comparing their residual spectra (photosphere-subtracted) to those of nearby stars, interstellar cloud velocities, and stellar radial velocities, we test whether interstellar absorption is the culprit and ascertain circumstellar gas origin. Using these methods, out of the 130 targets, we identified two new gas-bearing debris discs: TYC7879-1373-1, which exhibits stable absorption, and HIP30414, which shows variable gas absorption features linked likely to ongoing accretion. Both these systems are pre-main-sequence stars younger than 5Myr. TYC6822-283-1 has absorption features of inconclusive origin. This study increases the number of currently known very young (<10Myr) debris discs with circumstellar gas to eight, paving the path to future systematic studies of objects caught in transition from protoplanetary to debris disc stages.

astro-ph.EP↗

arXiv2025

HD 44892: The youngest (or oldest?) gas-harbouring debris disc around an intermediate mass star

We present the first detections of gas around a 2.1 Myr old debris disc-bearing intermediate-mass star, HD 44892. Gas is detected both in $^{12}$CO (2-1) emission through ALMA Band 6 observations and in absorption in Ca II K and H, seen with high-resolution UVES spectroscopy. $^{13}$CO and C$^{18}$O (2-1) are not detected. The star exhibits a 12 $μ$m fractional excess of $7.86^{+0.11}_{-2.27}$, placing it in the transition stage between protoplanetary and debris discs. Our detection of 1.3 mm emission yields the dust mass of 0.019$\pm$0.009 $M_{\oplus}$ assuming 115 K temperature. The $^{13}$CO non-detection places an upper limit on CO gas mass of $\sim$10$^{-2}$ $M_{\oplus}$. The $^{12}$CO detection yields a CO gas mass of (7.86$\pm$2.05)$\times$10$^{-5}$ $M_{\oplus}$ or (1.62$\pm$0.17)$\times$10$^{-4}$ $M_{\oplus}$ assuming a gas temperature of 20 K or 50 K, respectively. These should be considered as lower limits since $^{12}$CO emission may be optically thick. With UVES, we find variability in Ca II K and H lines, which can be interpreted by transiting circumstellar gas, ruling out interstellar absorption as their origin. Both the dust mass, which is within an order of magnitude of HD 141569, and the gas mass derived here indicate a late gas dispersal stage of the protoplanetary disc. Through our analysis we deem the alternative age of 800 Myr unlikely.

astro-ph.EP↗

arXiv2023

Gas absorption towards the eta Tel debris disc: winds or clouds?

eta Telescopii is a ~23 Myr old A-type star surrounded by an edge-on debris disc hypothesised to harbour gas. Recent analysis of far- and near-ultraviolet spectroscopic observations of eta Tel found absorption features at ~-23 km/s and ~-18 km/s in several atomic lines, attributed to circumstellar and interstellar gas, respectively. In this work, we put the circumstellar origin of the gas to a test by analysing high resolution optical spectroscopy of eta Tel and of three other stars with a similar line of sight as eta Tel: HD 181327, HD 180575, and rho Tel. We found absorption features at ~-23 km/s and ~-18 km/s in the Ca ii H&K lines, and at ~-23 km/s in the Na i D1&D2 doublet in eta Tel, in agreement with previous findings in the ultraviolet. However, we also found absorption features at ~-23 km/s in the Ca ii K lines of the three other stars analysed. This strongly implies that the absorption lines previously attributed to circumstellar gas are more likely due to an interstellar cloud traversing the line of sight of eta Tel instead.

astro-ph.SR↗

arXiv2022

X-Shooter Survey of Young Intermediate Mass Stars -- I. Stellar Characterization and Disc Evolution

Intermediate mass stars (IMSs) represent the link between low-mass and high-mass stars and cover a key mass range for giant planet formation. In this paper, we present a spectroscopic survey of 241 young IMS candidates with IR-excess, the most complete unbiased sample to date within 300 pc. We combined VLT/X-Shooter spectra with BVR photometric observations and Gaia DR3 distances to estimate fundamental stellar parameters such as Teff, mass, radius, age, and luminosity. We further selected those stars within the intermediate mass range 1.5 <= Mstar/Msun <= 3.5 and discarded old contaminants. We used 2MASS and WISE photometry to study the IR-excesses of the sample, finding 92 previously unidentified stars with IR-excess. We classified this sample into 'protoplanetary', 'hybrid candidates' and 'debris' discs based on their observed fractional excess at 12microns, finding a new population of 17 hybrid disc candidates. We studied inner disc dispersal timescales for λ < 10μm and found very different trends for IMSs and low mass stars (LMSs). IMSs show excesses dropping fast during the first 6 Myrs independently of the wavelength, while LMSs show consistently lower fractions of excess at the shortest wavelengths and increasingly higher fractions for longer wavelengths, with slower dispersal rates. In conclusion, this study demonstrates empirically that IMSs dissipate their inner discs very differently than LMSs, providing a possible explanation for the lack of short period planets around IMSs.

astro-ph.SR↗

arXiv2019

An unusually large gaseous transit in a debris disc

We present the detection of an unusually large transient gas absorption in several ionized species in the debris disc star HD 37306 using high-resolution optical spectra. We have been analysing a large sample of debris discs searching for circumstellar gas absorptions aiming to determine the frequency of gas in debris discs. HD 37306 stood out showing remarkably broad absorptions superimposed onto several photospheric Ca ii, Fe ii and Ti ii lines. The observed absorptions, unlike typical exocometary transits, lasted for at least eight days. Here we analyse simultaneous spectroscopic and photometric data of the event and evaluate different scenarios that might explain the observed features. We conclude that the most likely scenario might be an exocometary break-up releasing a significant amount of gas close to the star, producing an occulting "ring"/"torus" shape.

astro-ph.EP↗