- ID:
- ivo://CDS.VizieR/J/ApJ/889/142
- Title:
- Swift/XRT and NICER timing study of MAXI J1820+070
- Short Name:
- J/ApJ/889/142
- Date:
- 03 Dec 2021 13:13:00
- Publisher:
- CDS
- Description:
- We present a detailed timing analysis of the bright black hole X-ray binary MAXI J1820+070 (ASASSN-18ey), during its first detected outburst lasting from 2018 March until 2019 October based on Swift/XRT window timing mode observations, corresponding UVOT data and NICER observations. The light curves clearly show four outbursts, with the source remaining in the hard state during its first outburst, while the rise of the second outburst corresponds with the transition to the soft state. A similar double outburst of GX339-4 has been observed in 2004. Here it is followed by two hard-state only outbursts. In many observations the power density spectra showed type-C quasi-periodic oscillations (QPOs) with characteristic frequencies below 1Hz, which suggests that the source stayed in a state of low effective accretion for large parts of its outburst. The absence of other types of QPOs hinders a precise determination of the state transitions, but from combining NICER and Swift/XRT data, we find that MAXI J1820+070 went from the hard-intermediate to the soft state in less than one day. The covariance ratios derived from NICER data show an increase toward lower energies, which indicate that the source should make a transition to the soft state. This transition finally took place, after MAXI J1820+070 stayed in the hard state at rather constant luminosity for about 116 days. The steepness of the increase of the covariance ratios is not correlated with the amount of rms variability and it does not show a monotonic evolution along the outburst.
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- ID:
- ivo://CDS.VizieR/J/ApJS/245/15
- Title:
- Swift XRT follow-up of LIGO/Virgo GW triggers
- Short Name:
- J/ApJS/245/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Neil Gehrels Swift Observatory carried out prompt searches for gravitational-wave (GW) events detected by the LIGO/Virgo Collaboration (LVC) during the second observing run ("O2"). Swift performed extensive tiling of eight LVC triggers, two of which had very low false-alarm rates (GW170814 and the epochal GW170817), indicating a high confidence of being astrophysical in origin; the latter was the first GW event to have an electromagnetic counterpart detected. In this paper we describe the follow-up performed during O2 and the results of our searches. No GW electromagnetic counterparts were detected; this result is expected, as GW170817 remained the only astrophysical event containing at least one neutron star after LVC's later retraction of some events. A number of X-ray sources were detected, with the majority of identified sources being active galactic nuclei. We discuss the detection rate of transient X-ray sources and their implications in the O2 tiling searches. Finally, we describe the lessons learned during O2 and how these are being used to improve the Swift follow-up of GW events. In particular, we simulate a population of gamma-ray burst afterglows to evaluate our source ranking system's ability to differentiate them from unrelated and uncataloged X-ray sources. We find that ~60%-70% of afterglows whose jets are oriented toward Earth will be given high rank (i.e., "interesting" designation) by the completion of our second follow-up phase (assuming that their location in the sky was observed), but that this fraction can be increased to nearly 100% by performing a third follow-up observation of sources exhibiting fading behavior.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/47
- Title:
- Swift/XRT 0.2-10keV observations of SN2009ip
- Short Name:
- J/ApJ/768/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some supernovae (SNe) show evidence for mass-loss events taking place prior to their explosions. Measuring their pre-outburst mass-loss rates provides essential information regarding the mechanisms that are responsible for these events. Here we present XMM-Newton and Swift X-ray observations taken after the latest, and presumably the final, outburst of SN 2009ip. We use these observations as well as new near-infrared and visible-light spectra and published radio and visible-light observations to put six independent order-of-magnitude constraints on the mass-loss rate of the SN progenitor prior to the explosion. Our methods utilize the X-ray luminosity, the bound-free absorption, the H{alpha} luminosity, the SN rise time, free-free absorption, and the bolometric luminosity of the outburst detected prior to the explosion. Assuming spherical mass loss with a wind-density profile, we estimate that the effective mass-loss rate from the progenitor was between 10^-3^ and 10^-2^M_{sun}_/yr, over a few years prior to the explosion, with a velocity of ~10^3^km/s. This mass-loss rate corresponds to a total circumstellar matter (CSM) mass of ~0.04M_{sun}_, within 6x10^15^cm of the SN. We note that the mass-loss rate estimate based on the H{alpha} luminosity is higher by an order of magnitude. This can be explained if the narrow-line H{alpha} component is generated at radii larger than the shock radius, or if the CSM has an aspherical geometry. We discuss simple geometries which are consistent with our results.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/144
- Title:
- Swift/XRT 0.5-10keV obs. of MAXI J1659-152
- Short Name:
- J/ApJ/808/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an energy dependent X-ray variability study of the 2010 outburst of the black hole X-ray binary MAXI J1659-152 with the Swift X-ray Telescope (XRT). The broadband noise components and the quasi-periodic oscillations (QPO) observed in the power spectra show a strong and varied energy dependence. Combining Swift XRT data with data from the Rossi X-ray Timing Explorer, we report, for the first time, an rms spectrum (fractional rms amplitude as a function of energy) of these components in the 0.5-30keV energy range. We find that the strength of the low-frequency component (<0.1Hz) decreases with energy, contrary to the higher frequency components (>0.1Hz) whose strengths increase with energy. In the context of the propagating fluctuations model for X-ray variability, we suggest that the low-frequency component originates in the accretion disk (which dominates emission below ~2keV) and the higher frequency components are formed in the hot flow (which dominates emission above ~2keV). As the properties of the QPO suggest that it may have a different driving mechanism, we investigate the Lense-Thirring precession of the hot flow as a candidate model. We also report on the QPO coherence evolution for the first time in the energy band below 2keV. While there are strong indications that the QPO is less coherent at energies below 2keV than above 2keV, the coherence increases with intensity similar to what is observed at energies above 2keV in other black hole X-ray binaries.
18485. Swift-XRT long GRB durations
- ID:
- ivo://CDS.VizieR/J/ApJ/800/16
- Title:
- Swift-XRT long GRB durations
- Short Name:
- J/ApJ/800/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of a number of gamma-ray bursts (GRBs) with duration exceeding 1000s has opened the debate on whether these bursts form a new class of sources, the so-called ultra-long GRBs, or if they are rather the tail of the distribution of the standard long GRB duration. Using the long GRB sample detected by Swift, we investigate the statistical properties of long GRBs and compare them with the ultra-long burst properties. We compute the burst duration of long GRBs using the start epoch of the so-called "steep decay" phase detected with Swift/XRT. We discuss also the differences observed in their spectral properties. We find that ultra-long GRBs are statistically different from the standard long GRBs with typical burst duration less than 100-500s, for which a Wolf-Rayet star progenitor is usually invoked. Together with the presence of a thermal emission component we interpret this result as indication that the usual long GRB progenitor scenario cannot explain the extreme duration of ultra-long GRBs, their energetics, as well as the mass reservoir and size that can feed the central engine for such a long time.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1177
- Title:
- Swift-XRT observations of GRBs
- Short Name:
- J/MNRAS/397/1177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous X-ray analysis of all 318 Gamma Ray Bursts detected by the X-ray Telescope on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2-3 we detail the methods which the Swift-XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift-XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4-6 we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/945
- Title:
- Swift/XRT obs. of unidentified IBIS sources
- Short Name:
- J/MNRAS/403/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most recent IBIS/ISGRI survey, i.e. the fourth one, lists 723 hard X-ray sources, many still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies, i.e. below 10keV. In order to overcome this lack of X-ray information, we cross-correlated the list of IBIS sources included in the fourth IBIS catalogue with the Swift/X-ray Telescope (XRT) data archive, finding a sample of 20 objects, not yet reported in the literature, for which XRT data could help in the search for the X-ray and hence optical counterpart and/or, for the first time, in the study of the source spectral and variability properties below 10keV. 16 of these objects are new INTEGRAL detections, while four were already listed in the third survey but not yet observed in X-rays.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/433
- Title:
- SWIRE/Chandra survey in Lockman Hole Field
- Short Name:
- J/ApJS/185/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a moderate-depth (70ks), contiguous 0.7deg^2^ Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (logN_H_>23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8keV) flux ~4x10^-16^erg/cm^2^/s. We present the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The logN versus logS agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24um detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7uJy rms) VLA data yield 251 (>4{sigma}) radio counterparts, 44% of the X-ray sources in the field. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition, RL. The majority of these are red and relatively faint in the optical so that the use of RL to select those AGNs with the strongest radio emission becomes questionable. Using the 24um to radio flux ratio (q_24_) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. We conclude that q_24_ is a more reliable indicator of radio-loudness. Use of RL should be confined to the optically selected type 1 AGN.
- ID:
- ivo://CDS.VizieR/II/255
- Title:
- SWIRE ELAIS N1 Source Catalogs
- Short Name:
- II/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Wide-area InfraRed Extragalactic survey (SWIRE; Lonsdale et al., 2003PASP..115..897L) Version 1.0 data products release includes an image atlas and a source catalogs from the first of the 6 SWIRE fields to be observed by Spitzer, the ELAIS-N1 field. The release includes both Spitzer IRAC and MIPS mid/far-infrared data products and also Ug'r'i'Z optical data covering the same regions of the sky from the Isaac Newton Telescope (INT) Wide-Field Survey (WFS; McMahon et al., 2001NewAR..45...97M; Gonzalez-Solares et al., 2004, MNRAS, in press). The Version 1.0 SWIRE ELAIS-N1 Source Catalogs have three parts: (1) a catalog including IRAC and MIPS 24{mu}m sources which have been band-merged together. The Spitzer source list has been positionally matched to the optical source list and we report optical position and 5-band magnitude data for each successful match. This catalog contains only sources lying with the region which has full coverage in all four IRAC bands; (2) a 70{mu}m catalog; and (3) a 160{mu}m catalog. The longer wavelength catalogs have not been band-merged with the IRAC+24{mu}m catalog or the optical source list at this time because of complex source confusion issues. The two MIPS-Ge catalogs cover the full area scanned by each MIPS-array, except for areas of low coverage around each edge, and are not restricted to the full IRAC coverage area. All data are available at http://data.spitzer.caltech.edu/popular/swire/20041027_enhanced_v1_EN1
- ID:
- ivo://CDS.VizieR/J/A+A/476/151
- Title:
- SWIRE ELAIS-S1 IR-peak galaxy IR fluxes
- Short Name:
- J/A+A/476/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Main data on the IR-peakers sample in the SWIRE ELAIS-S1 field. For each IR-peak galaxy, we report R band magnitude (AB units, from the ESIS survey, Berta et al., 2006A&A...451..881B), Spitzer SWIRE fluxes (Lonsdale et al., 2003PASP..115..897L, 2004ApJS..154...54L), photometric redshift (based on Hyper-z fit, Bolzonella et al., 2000A&A...363..476B), the stellar mass and its minimal-maximal range. The stellar mass estimate is based on mixed stellar population (MSP) synthesis (Berta et al., 2004A&A...418..913B). The minimal and maximal stellar masses are obtained by exploring the SFH-extinction parameter space with the Adaptive Simulated Annealing algorithm (Ingber et al., 2001, http://www.ingber.com/asa01_lecture.pdf). See the paper associated to these data for more details.