New JWST redshifts for the host galaxies of CDF-S XT1 and XT2: understanding their nature

Abstract

CDF-S XT1 and XT2 are considered two canonical extragalactic fast X-ray transients (FXTs). In this work, we report new constraints on both FXTs, based on recent JWST NIRCam and MIRI photometry, as well as NIRspec spectroscopy for CDF-S XT2 that allow us to improve our understanding of their distances, energetics, and host galaxy properties compared to the pre-JWST era. We use the available HST and JWST archival data to determine the host properties and constrain the energetics of each FXT based on spectral energy distribution (SED) photometric fitting. The host of CDF-S XT1 is now constrained to lie at $z$=2.76, implying a host absolute magnitude $M_R=-19.14$~mag, stellar mass $M_{\ast }=$1.8e8~$M_{\odot }$, and star formation rate SFR$=0.62M_{\odot }$/yr. These properties lie at the upper end of previous estimates, leaving CDF-S XT1 with a peak X-ray luminosity of 2.8e47 erg/s. We argue that the best progenitor scenario for XT1 is a low-luminosity gamma-ray burst (GRB), although we do not fully rule out a proto-magnetar association or a jetted tidal disruption event involving a white dwarf and an intermediate-massive black hole. In the case of CDF-S XT2, JWST imaging reveals a new highly obscured component of the host galaxy, previously missed in HST images, while NIRspec spectroscopy securely places the host at $z$=3.4598. The new redshift implies a host with $M_R=-21.76$~mag, $M_{\ast }=5.5e10M_{\odot }$, SFR=160~$M_{\odot }$/yr, and FXT $L_{X,peak}=1.4e47$~erg/s. The revised energetics, similarity to X-ray flash event light curves, small host offset, and high host SFR favor a low-luminosity collapsar progenitor for CDF-S XT2. Although a magnetar model is not ruled out, it appears improbable. While these HST and JWST observations shed light on the host galaxies of XT1 and XT2, and by extension, on the nature of FXTs, a unique explanation for both sources remains elusive.

The manuscript was accepted by Astronomy & Astrophysics in January 2025

References in corpus (85)

• The James Webb Space Telescope
• EAZY: A Fast, Public Photometric Redshift Code
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• An online repository of Swift/XRT light curves of GRBs
• Observation of gravitational waves from two neutron star-black hole coalescences
• Stellar Population Inference with Prospector
• An optical supernova associated with the X-ray flash XRF 060218
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• The James Webb Space Telescope Mission
• NIRCam Performance on JWST In Flight
• From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109
• The rate, luminosity function and time delay of non-Collapsar short GRBs
• Stellar masses from the CANDELS survey: the GOODS-South and UDS fields
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
• REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination
• The Millisecond Magnetar Central Engine in short GRBs
• Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for their Progenitors
• Discovery of the nearby long, soft GRB 100316D with an associated supernova
• The Star Formation Main Sequence in the Hubble Space Telescope Frontier Fields
• In-orbit Performance of the Near-Infrared Spectrograph NIRSpec on the James Webb Space Telescope
• The MUSE Hubble Ultra Deep Field Survey: II. Spectroscopic redshifts and comparisons to color selections of high-redshift galaxies
• JADES NIRSpec Initial Data Release for the Hubble Ultra Deep Field: Redshifts and Line Fluxes of Distant Galaxies from the Deepest JWST Cycle 1 NIRSpec Multi-Object Spectroscopy
• Fast, Slow, Early, Late: Quenching Massive Galaxies at z~0.8
• ALMA spectroscopic survey in the Hubble Ultra Deep Field: Continuum number counts, resolved 1.2-mm extragalactic background, and properties of the faintest dusty star forming galaxies
• A unified picture for low-luminosity and long gamma-ray bursts based on the extended progenitor of llgrb 060218/SN 2006aj
• GASS: The Parkes Galactic All-Sky Survey. Update: improved correction for instrumental effects and new data release
• The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
• Can the early X-ray afterglow of GRBs be explained by a contribution from the reverse shock?
• Bulk Lorentz factors of Gamma-Ray Bursts
• "Late prompt" emission in Gamma Ray Bursts?
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. I. Bursts detected in the triggered mode
• The Palomar Transient Factory Core-Collapse Supernova Host-Galaxy Sample. I. Host-Galaxy Distribution Functions and Environment-Dependence of CCSNe
• A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
• The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at $z=0.27$
• Short GRB Host Galaxies I: Photometric and Spectroscopic Catalogs, Host Associations, and Galactocentric Offsets
• A mildly relativistic outflow from the energetic, fast-rising blue optical transient CSS161010 in a dwarf galaxy
• A thousand days after the merger: continued X-ray emission from GW170817
• IFU observations of the GRB 980425/SN 1998bw host galaxy: emission line ratios in GRB regions
• Illuminating Massive Black Holes With White Dwarfs: Orbital Dynamics and High Energy Transients from Tidal Interactions
• The nature of the dwarf starforming galaxy associated with GRB 060218 / SN2006aj
• Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
• A Comprehensive Radio View of the Extremely Bright Gamma-Ray Burst 130427A
• The deepest X-ray view of high-redshift galaxies: constraints on low-rate black-hole accretion
• An ALMA survey of the S2CLS UDS field: Optically invisible submillimetre galaxies
• A Comparative Study of Long and Short GRBs. I. Overlapping Properties
• Nonthermal gamma-ray and X-ray flashes from shock breakout in gamma-ray bursts/supernovae
• SN 2007bg: The Complex Circumstellar Environment Around One of the Most Radio-Luminous Broad-Lined Type Ic Supernovae
• X-ray properties of TDEs
• The Interpretation and Implication of the Afterglow of GRB 060218
• Bayesian Single-Epoch Photometric Classification of Supernovae
• Shock Breakout in 3-Dimensional Red Supergiant Envelopes
• Extragalactic fast X-ray transient candidates discovered by Chandra (2000-2014)
• Two fast X-ray transients in archival Chandra data
• The Chandra Deep Fields: Lifting the Veil on Distant Active Galactic Nuclei and X-Ray Emitting Galaxies
• Blasts from the Past: Supernova Shock Breakouts among X-Ray Transients in the XMM-Newton Archive
• Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects
• The afterglow of a relativistic shock breakout and low-luminosity GRBs
• Unveiling the population of orphan Gamma Ray Bursts
• The broad-line type Ic SN 2020bvc: signatures of an off-axis gamma-ray burst afterglow
• Mass, Spin, and Ultralight Boson Constraints from the Intermediate Mass Black Hole in the Tidal Disruption Event 3XMM J215022.4-055108
• X-ray flares, plateaus, and chromatic breaks of GRB afterglows from up-scattered forward-shock emission
• ZTF20aajnksq (AT2020blt): A Fast Optical Transient at $z\approx 2.9$ With No Detected Gamma-Ray Burst Counterpart
• Extragalactic FXT Candidates Discovered by Chandra (2014-2022)
• The hidden side of cosmic star formation at z > 3: Bridging optically-dark and Lyman break galaxies with GOODS-ALMA
• The Peculiar Transient AT2018cow: A Possible Origin of A Type Ibn/IIn Supernova
• A Supernova Candidate at z=0.092 in XMM-Newton Archival Data
• Deepest view of AGN X-ray variability with the 7 Ms Chandra Deep Field-South survey
• Discovery of Three Candidate Magnetar-powered Fast X-ray Transients from Chandra Archival Data
• $JWST$ Insight Into a Lensed $HST$-dark Galaxy and its Quiescent Companion at $z=2.58$
• Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST
• The EXTraS Project: Exploring the X-ray transient and variable sky
• The host galaxy of GRB 980425 / SN1998bw: a collisional ring galaxy
• On the properties of a newborn magnetar powering the X-ray transient CDF-S XT2
• CDF-S XT1 and XT2: White Dwarf Tidal Disruption Events by Intermediate-Mass Black Holes?
• Constraining the intrinsic population of Long Gamma-Ray Bursts: implications for spectral correlations, cosmic evolution and their use as tracers of star formation
• A blast from the infant Universe: the very high-z GRB 210905A
• The Rapidly Spinning Intermediate-Mass Black Hole 3XMM J150052.0+015452
• On the Binary-Neutron-Star Post-Merger Magnetar Origin of XRT 210423
• The Fast X-ray Transient XRT 210423 and its Host Galaxy
• Possible origin of AT2021any: a failed GRB from a structured jet
• False outliers of the Ep,i - Eiso correlation?
• MOCCA-SURVEY Database -- I. Tidal disruption events of white dwarfs in globular clusters and young massive clusters
• GRB 111209A/SN 2011kl: Collapse of a supramassive magnetar with r-mode oscillation and fall-back accretion onto a newborn black hole
• Luminosity function and event rate density of XMM-Newton-selected supernova shock-breakout candidates
• Observability of flashes from ejecta crashes in aspherical supernovae, with application to SN 2008D

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