- ID:
- ivo://CDS.VizieR/J/A+A/609/A53
- Title:
- Tracing stars of MW dwarf galaxies: Sextans
- Short Name:
- J/A+A/609/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep and very spatially extended CTIO/DECam g and r photometric catalogue of point-sources (reaching out to ~2 magnitudes below the oldest main-sequence turn-off and covering ~20deg^2^) around the Sextans dwarf spheroidal galaxy, together with another catalogue of literature spectroscopic measurements (Walker et al., 2009, Cat. J/AJ/137/3100 and Battaglia et al., 2011, Cat. J/MNRAS/411/1013) with updated membership probabilities.
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- ID:
- ivo://CDS.VizieR/J/A+A/643/A141
- Title:
- Tracing total molecular gas in galaxies
- Short Name:
- J/A+A/643/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Molecular gas is a necessary fuel for star formation. The CO (1-0) transition is often used to deduce the total molecular hydrogen, but is challenging to detect in low metallicity galaxies, in spite of the star formation taking place. In contrast, the [CII] 158um is relatively bright, highlighting a potentially important reservoir of H_2_ that is not traced by CO (1-0), but residing in the [CII] - emitting regions.Here we aim to explore a method to quantify the total H_2_ mass (MH_2_) in galaxies and learn what parameters control the CO-dark reservoir. We present Cloudy grids of density, radiation field and metallicity in terms of observed quantities, such as [OI], [CI], CO (1-0), [CII] and L_TIR_ and the total MH_2_. We provide recipes based on these models to derive total MH_2_ mass estimates from observations. We apply the models to the Herschel Dwarf Galaxy Survey, extracting the total MH_2_ for each galaxy and compare this to the H_2_ determined from the observed CO (1-0) line. This allows us to quantify the reservoir of H_2_ that is CO-dark and traced by the [CII]158um. We demonstrate that while the H2 traced by CO(1-0) can be negligible, the [CII] 518um can trace the total H2. We find 70% to 100 % of the total H2 mass is not traced by CO (1-0) in the dwarf galaxies, but is well-traced by [CII] 158um. The CO-dark gas mass fraction correlates with the observed L[CII]/LCO(1-0) ratio. A conversion factor for [CII] 158um to total H_2_ and a new CO-to-total-MH_2_ as a function of metallicity, is presented. While low metallicity galaxies may have a feeble molecular reservoir as surmised from CO observations, the presence of an important reservoir of molecular gas, not detected by CO, can exist. We suggest a general recipe to quantify the total mass of H2 in galaxies, taking into account the CO and [CII] observations. Accounting for this CO-dark H_2_ gas, we find that the star forming dwarf galaxies now fall on the Schmidt-Kennicuttrelation. Their star-forming efficiency is rather normal, since the reservoir from which they form stars is now more massive when introducing the [CII] measures of the total H_2_, compared to the little amount of H_2_ in the CO-emitting region.
- ID:
- ivo://CDS.VizieR/J/A+A/408/387
- Title:
- Transformation between ICRS and ITRS
- Short Name:
- J/A+A/408/387
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the current IAU hierarchy of the relativistic reference systems, practical formulae for the transformation between barycentric (BCRS) and geocentric (GCRS) celestial reference systems are derived. BCRS is used to refer to ICRS, International Celestial Reference System. This transformation is given in four versions, dependent on the time arguments used for BCRS (TCB or TDB) and for GCRS (TCG or TT). All quantities involved in these formulae have been tabulated with the use of the VSOP theories (IMCCE theories of motion of the major planets). In particular, these formulae may be applied to account for the indirect relativistic third-body perturbations in motion of Earth's satellites and Earth's rotation problem. We propose to use the SMART theory (IMCCE theory of Earth's rotation) in constructing the Newtonian three-dimensional spatial rotation transformation between GCRS and ITRS, the International Terrestrial Reference System. This transformation is compared with two other versions involving extra angular variables currently used by IERS, the International Earth Rotation Service. It is shown that the comparison of these three forms of the same transformation may be greatly simplified by using the proposed composite rotation formula.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A64
- Title:
- Trans-HCOOH hyperfine structure
- Short Name:
- J/A+A/520/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Formic acid, HCOOH, is the simplest organic acid and the first that has been identified in the interstellar medium. Its astrophysical relevance has motivated this spectroscopic study. The aim of this investigation is to provide very accurate rest frequencies for the trans isomer of HCOOH as well as to improve the spectroscopic and hyperfine parameters available in the literature for this molecule. The Lamb-dip technique has been exploited in order to record the rotational spectrum of trans-HCOOH at sub-Doppler resolution in the millimeter- and submillimeter-wave frequency ranges and, when possible, to resolve the hyperfine structure due to the hydrogen nuclei. THz measurements have been carried out as well. The experimental investigation has been supported by high-level quantum-chemical calculations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/1468
- Title:
- Transient black hole X-ray binaries XMM obs.
- Short Name:
- J/MNRAS/471/1468
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All observations of Galactic X-ray binaries are affected by absorption from gas and dust in the interstellar medium (ISM) which imprints narrow (line) and broad (photoelectric edges) features on the continuum emission spectrum of the binary. Any spectral model used to fit data from a Galactic X-ray binary must therefore take account of these features; when the absorption is strong (as for most Galactic sources) it becomes important to accurately model the ISM absorption in order to obtain unbiased estimates of the parameters of the (emission) spectrum of the binary system. In this paper, we present analysis of some of the best spectroscopic data from the XMM-Newton RGS instrument using the most up-to-date photoabsorption model of the gaseous ISM ISMabs. We calculate column densities for H, O, Ne and Fe for seven transient black hole X-ray binary systems. We find that the hydrogen column densities in particular can vary greatly from those presented elsewhere in the literature. We assess the impact of using inaccurate column densities and older X-ray absorption models on spectral analysis using simulated data. We find that poor treatment of absorption can lead to large biases in inferred disc properties and that an independent analysis of absorption parameters can be used to alleviate such issues.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A147
- Title:
- Transient processing and analysis using AMPEL
- Short Name:
- J/A+A/631/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Both multi-messenger astronomy and new high-throughput wide-field surveys require flexible tools for the selection and analysis of astrophysical transients. Here we introduce the alert management, photometry, and evaluation of light curves (AMPEL) system, an analysis framework designed for high-throughput surveys and suited for streamed data. AMPEL combines the functionality of an alert broker with a generic framework capable of hosting user-contributed code; it encourages provenance and keeps track of the varying information states that a transient displays. The latter concept includes information gathered over time and data policies such as access or calibration levels. We describe a novel ongoing real-time multi-messenger analysis using AMPEL to combine IceCube neutrino data with the alert streams of the Zwicky Transient Facility (ZTF). We also reprocess the first four months of ZTF public alerts, and compare the yields of more than 200 different transient selection functions to quantify efficiencies for selecting Type Ia supernovae that were reported to the Transient Name Server (TNS). We highlight three channels suitable for (1) the collection of a complete sample of extragalactic transients, (2) immediate follow-up of nearby transients, and (3) follow-up campaigns targeting young, extragalactic transients. We confirm ZTF completeness in that all TNS supernovae positioned on active CCD regions were detected. AMPEL can assist in filtering transients in real time, running alert reaction simulations, the reprocessing of full datasets as well as in the final scientific analysis of transient data. This is made possible by a novel way of capturing transient information through sequences of evolving states, and interfaces that allow new code to be natively applied to a full stream of alerts. This text also introduces a method by which users can design their own channels for inclusion in the AMPEL live instance that parses the ZTF stream and the real-time submission of high-quality extragalactic supernova candidates to the TNS.
- ID:
- ivo://CDS.VizieR/J/PAZh/28/323
- Title:
- Transient X-ray burster KS 1731-260
- Short Name:
- J/PAZh/28/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the transient X-ray burster KS 1731-260 from 1988 until 1999 with the Kvant/TTM telescope supplemented with published data from the ASM and PCA instruments of the RXTE observatory for 1996-2001.
- ID:
- ivo://CDS.VizieR/J/ApJ/643/356
- Title:
- Transient X-ray sources in M31
- Short Name:
- J/ApJ/643/356
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From 1999 October to 2002 August, 45 transient X-ray sources were detected in M31 by Chandra and XMM-Newton. We have performed spectral analysis of all XMM-Newton and Chandra ACIS detections of these sources, as well as flux measurements of Chandra HRC detections. The result is absorption-corrected X-ray light curves for these sources covering this 2.8yr period, along with spectral parameters for several epochs of the outbursts of most of the transient sources. We supply a catalog of the locations, outburst dates, peak observed luminosities, decay time estimates, and spectral properties of the transient sources, and we discuss similarities with Galactic X-ray novae. Duty cycle estimates are possible for eight of the transients and range from 34% to 2%; upper limits to the duty cycles are estimated for an additional 15 transients and cover a similar range. We find five transients that have rapid decay times and may be ultracompact X-ray binaries. Spectra of three of the transients suggest that they may be faint Galactic foreground sources. If even one is a foreground source, this suggests a surface density of faint transient X-ray sources of >~1deg^2^.
- ID:
- ivo://CDS.VizieR/J/AJ/159/83
- Title:
- Transit analysis for the K2-25 system
- Short Name:
- J/AJ/159/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance of planets with orbital periods of a few to tens of days suggests that exoplanets experience complex dynamical histories. Planets in young stellar clusters or associations have well-constrained ages and therefore provide an opportunity to explore the dynamical evolution of exoplanets. K2-25b is a Neptune-sized planet in an eccentric, 3.48day orbit around an M4.5 dwarf star in the Hyades cluster (650Myr). In order to investigate its non-zero eccentricity and tight orbit, we analyze transit timing variations (TTVs) which could reveal clues to the migration processes that may have acted on the planet. We obtain 12 nonconsecutive transits using the MEarth observatories and long-term photometric monitoring, which we combine with 10 transits from the Spitzer Space Telescope and 20 transits from K2. Tables of MEarth photometry accompany this work. We fit each transit lightcurve independently. We first investigate whether inhomogeneities on the stellar surface (such as spots or plages) are differentially affecting our transit observations. The measured transit depth does not vary significantly between transits, though we see some deviations from the fiducial transit model. We then looked for TTVs as evidence of a nontransiting perturber in the system. We find no evidence for >1M_{Earth}_ mass companions within a 2:1 period ratio, or for >5M_{Earth}_ mass planets within a 7:2 period ratio.
- ID:
- ivo://CDS.VizieR/J/AJ/161/72
- Title:
- 180 Transit and occultation times for WASP-12b
- Short Name:
- J/AJ/161/72
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- Theory suggests that the orbits of some close-in giant planets should decay due to tidal interactions with their host stars. To date, WASP-12b is the only hot Jupiter reported to have a decaying orbit, at a rate of 29{+/-}2ms/yr. We analyzed data from NASA's Transiting Exoplanet Survey Satellite (TESS) to verify that WASP-12b's orbit is indeed changing. We find that the TESS transit and occultation data are consistent with a decaying orbit with an updated period of 1.091420090{+/-}0.000000041days and a decay rate of 32.53{+/-}1.62ms/yr. We find an orbital decay timescale of {tau}=P/|P|=2.90{+/-}0.14Myr. If the observed decay results from tidal dissipation, the modified tidal quality factor is Q_*_'=1.39{+/-}0.15x10^5^, which falls at the lower end of values derived for binary star systems and hot Jupiters. Our result highlights the power of space-based photometry for investigating the orbital evolution of short-period exoplanets.
