[
{
"id": "authors:p76hy-hw016",
"collection": "authors",
"collection_id": "p76hy-hw016",
"cite_using_url": "https://authors.library.caltech.edu/records/p76hy-hw016",
"type": "article",
"title": "PEARLS: JWST Counterparts of Microjansky Radio Sources in the North Ecliptic Pole Time Domain Field. II. All Four Spokes",
"author": [
{
"family_name": "Willner",
"given_name": "S. P.",
"orcid": "0000-0002-9895-5758"
},
{
"family_name": "Gim",
"given_name": "Hansung B.",
"orcid": "0000-0003-1436-7658"
},
{
"family_name": "Polletta",
"given_name": "Maria del Carmen",
"orcid": "0000-0001-7411-5386"
},
{
"family_name": "Bowling",
"given_name": "Gibson B.",
"orcid": "0009-0007-0782-0721"
},
{
"family_name": "Cohen",
"given_name": "Seth H.",
"orcid": "0000-0003-3329-1337"
},
{
"family_name": "Estrada-Carpenter",
"given_name": "Vicente",
"orcid": "0000-0001-8489-2349"
},
{
"family_name": "Koekemoer",
"given_name": "Anton M.",
"orcid": "0000-0002-6610-2048"
},
{
"family_name": "O'Brien",
"given_name": "Rosalia",
"orcid": "0000-0003-3351-0878"
},
{
"family_name": "Pigarelli",
"given_name": "Alex",
"orcid": "0000-0001-9369-6921"
},
{
"family_name": "Willmer",
"given_name": "Christopher N. A.",
"orcid": "0000-0001-9262-9997"
},
{
"family_name": "Windhorst",
"given_name": "Rogier A.",
"orcid": "0000-0001-8156-6281"
},
{
"family_name": "Jansen",
"given_name": "Rolf A.",
"orcid": "0000-0003-1268-5230"
},
{
"family_name": "Ortiz",
"given_name": "Rafael",
"orcid": "0000-0002-6150-833X"
},
{
"family_name": "Summers",
"given_name": "Jake",
"orcid": "0000-0002-7265-7920"
},
{
"family_name": "Cotton",
"given_name": "William",
"orcid": "0000-0001-7363-6489"
},
{
"family_name": "Civano",
"given_name": "Francesca",
"orcid": "0000-0002-2115-1137"
},
{
"family_name": "Grogin",
"given_name": "Norman A.",
"orcid": "0000-0001-9440-8872"
},
{
"family_name": "Maksym",
"given_name": "W. P.",
"orcid": "0000-0002-2203-7889"
},
{
"family_name": "Saikia",
"given_name": "Payaswini",
"orcid": "0000-0002-5319-6620"
},
{
"family_name": "Silver",
"given_name": "Ross M.",
"orcid": "0000-0001-6564-0517"
},
{
"family_name": "Zhao",
"given_name": "Xiurui",
"orcid": "0000-0002-7791-3671",
"clpid": "Zhao-Xiurui"
}
],
"abstract": "JWST/NIRCam observations in the north ecliptic pole Time Domain Field (TDF) identify 4.4 μm counterparts for 206 of 211 radio sources with S(3 GHz) \u2273 5 μJy in a 65 arcmin2 field. One of the remaining radio sources is likely to be a radio lobe of a nearby Seyfert galaxy, and the four radio sources without counterparts could be spurious. All but five counterparts are brighter than magnitude 23.5 AB at 4.4 μm. A simple position match with a radius of 0.\"3 would have identified 198 of the counterparts but only in a 4.4 μm catalog created with aggressive deblending of multiple peaks within an object’s brightness distribution into distinct catalog sources. The properties of the radio host galaxies are mostly consistent with those found in Paper I: the median redshift is 1.15, and the radio emission, calculated by taking into account the nonlinear dependence of the radio luminosity on the star formation rate, is consistent with a star formation origin in ∼79% of the sample. For the other ∼21%, the radio flux could come from star formation hidden behind dust or from an active galactic nucleus (AGN). One difference from other studies of radio-source counterparts is that 66% of the radio hosts show at least one indication of an AGN’s presence. The presence of AGN and of hidden star formation could be elucidated by monitoring for source variability, and the TDF is the field most suited to such observations.
",
"doi": "10.3847/1538-4357/ae796c",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-08-01",
"series_number": "2",
"volume": "1006",
"issue": "2",
"pages": "219"
},
{
"id": "authors:dzmqk-4fz83",
"collection": "authors",
"collection_id": "dzmqk-4fz83",
"cite_using_url": "https://authors.library.caltech.edu/records/dzmqk-4fz83",
"type": "article",
"title": "Characterizing the \u03b3-Ray Emission from Low-luminosity AGN",
"author": [
{
"family_name": "Karwin",
"given_name": "Christopher M.",
"orcid": "0000-0002-6774-3111"
},
{
"family_name": "Khatiya",
"given_name": "Nikita S.",
"orcid": "0009-0002-2068-3411"
},
{
"family_name": "Boughelilba",
"given_name": "Margot",
"orcid": "0000-0003-1046-1647"
},
{
"family_name": "Zhao",
"given_name": "Xiurui",
"orcid": "0000-0002-7791-3671",
"clpid": "Zhao-Xiurui"
},
{
"family_name": "Reimer",
"given_name": "Anita",
"orcid": "0000-0001-8604-7077"
},
{
"family_name": "Ajello",
"given_name": "Marco",
"orcid": "0000-0002-6584-1703"
}
],
"abstract": "\n
A majority of the active galactic nuclei (AGN) in the local Universe are classified as low-luminosity AGN (LLAGN), having bolometric luminosities \u22721042 erg s−1. Although high-energy γ-ray emission is predicted from both the jets and disks of LLAGN, to date only four have been detected by the Fermi Large Area Telescope (Fermi-LAT). In this work, we therefore conduct a comprehensive study of all the LLAGN from the Palomar spectroscopic survey of bright, northern galaxies, including both subthreshold and detected γ-ray sources, using 14.4 yr of LAT data. Our analysis results in a new detection of one LLAGN, as well as a detection of the subthreshold population using a stacking technique. We find that the signal from the subthreshold sample is consistent with being dominated by star formation activity, although a contribution from compact jets or a mixed contribution from jetted and nonjetted systems is also feasible. On the other hand, the individually detected LLAGN are likely dominated by jet emission. We perform detailed spectral modeling for a subset of these sources and find that the γ-ray signal can be explained by synchrotron self-Compton radiation if the inner jet emission region is weakly magnetized, with its total energy density being strongly particle dominated and only slowly moving. With this work we also publicly release our Python-based stacking library for analyzing subthreshold source populations with the LAT based on a proven technique used in numerous studies.
\n
\n
This work discusses the broadband X-ray spectral analysis of 11 candidate heavily obscured active galactic nuclei (AGN) selected based on their infrared and X-ray properties by a recently published machine learning algorithm. This paper is part of a larger work to identify and characterize all AGN in the local Universe (z < 0.1) with the largest line-of-sight (los) column densities (NH), the so-called Compton-thick (NH,los ≥ 1024 cm−2) AGN. We modeled the X-ray spectra using two physically motivated models: UXClumpy and RXTorusD. Of the 11 AGN in our sample, we found 3 to be obscured with 22.7 < LogNH,los ≤ 23.0, 5 with 23.0 < LogNH,los ≤ 23.25, and 3 with 23.4 < LogNH,los ≤ 23.9, according to UXClumpy. Meanwhile, according to RXTorusD, we found 3 AGN to be obscured with 22.7 < LogNH,los ≤ 23.0, 4 with 23.0 < LogNH,los ≤ 23.4, and 4 with 23.85 < LogNH,los ≤ 23.96. Additionally, this work served as a comparison between UXClumpy and RXTorusD. We found broad agreement between the two, with 8 of 11 sources agreeing on the value of the photon index Γ, while only 5 of 11 sources agree on the NH,los value within the 90% confidence level.
\n
\n
We report the discovery of the first transient relativistic iron Kα line in an active galactic nucleus (AGN), J1047+5907. The line was detected 21.5 days (rest frame) after an X-ray coronal flare was observed in 2008, and it exhibits significant broadening consistent with relativistic reflection from the accretion disk in the vicinity of the central supermassive black hole (SMBH). The line has a width of ∼300 eV, corresponding to a Keplerian velocity of 14,000 km s−1, at a distance of 5–41 light-days from the SMBH, strongly implying that the observed coronal flare triggered the emergence of the line. This event provides rare direct evidence of the response of the accretion disk to impulsive coronal illumination and offers a new method to probe the SMBH and disk physics. The relativistic modeling favors a broadened line produced by distant reflection from an accretion disk around a rapidly spinning black hole viewed at an intermediate inclination, consistent with other observations. Systematic monitoring of type 1 AGN following strong X-ray flares may open a new observational window into the innermost regions of AGN, enabling constraints on the physics of SMBH and its accretion disk at different radii that are otherwise challenging to access.
\n
\n
Giant radio sources (GRSs) harbor the Universe’s largest structures generated by individual galaxies, with projected source sizes exceeding 700 kpc. These enigmatic objects have been mainly studied at radio frequencies, and their physical properties in the high-energy domain are poorly understood. Here we present the results of a multiwavelength study focused on NuSTAR J112829+5831.8 (J1128+5831), the only known GRS serendipitously detected with the Nuclear Spectroscopic Telescope Array. Being located in proximity to the famous interacting galaxy system, Arp 299, J1128+5831 has been serendipitously observed also by the Chandra X-ray Observatory, Hubble Space Telescope, and XMM-Newton satellites. From radio observations with the Low Frequency Array, the NRAO VLA Sky Survey, and the Very Large Array Sky Survey, we have determined that J1128+5831 has an overall steep radio spectrum (α = −0.86; Fν ∝ να) and a low core dominance (CD = −2.4, in log-scale), indicating the source to be viewed at large angles. From the X-ray spectral analysis, we found J1128+5831 to harbor an obscured active galactic nucleus (AGN) with neutral hydrogen column density exceeding 1023 cm−2. Its optical spectrum, taken with the Dark Energy Spectroscopic Instrument, exhibits prominent narrow emission lines but lacks broad components, thus confirming J1128+5831 to be a Type 2 AGN powered by a radiatively efficient accreting system. Overall, the broadband properties of J1128+5831 are consistent with those observed for the general GRS population.
\n
\n
We present observations and analysis of the bound planetary microlensing event KMT-2025-BLG-1616. The planetary signal was captured by the Korea Microlensing Telescope Network and the Dark Energy Camera Rogue Earths and Mars Survey (DREAMS). DREAMS’s minute-cadence observations break the central/resonant degeneracy in the binary-lens models. The color of the faint source star (I = 22) is measured from the DREAMS’s r − z color. The planetary system has a planet-host mass ratio of q ∼ 5 × 10−4. A Bayesian analysis yields a host-star mass of ∼0.3 M\u2299, a planetary mass of ∼40 M⊕, a projected planet-host separation of ∼1.6 au, and a lens distance of ∼7.5 kpc. Based on the photometric precision achieved by DREAMS for this event, we simulate free-floating planet (FFP) detections and find that DREAMS is sensitive to Mars-mass FFPs in the Galactic bulge and Moon-mass FFPs in the Galactic disk.
\n
X-ray surveys are one of the most unbiased methods for detecting Compton-thick (CT; NH ≥ 1024 cm−2) active galactic nuclei (AGN), which are thought to comprise up to 60% of AGN within z \u2272 1.0. These CT AGN are often difficult to detect with current instruments, but the X-ray data within the JWST-North Ecliptic Pole (NEP) Time Domain Field present a unique opportunity to study faint and obscured AGN. The NEP contains the deepest NuSTAR survey to date, and X. Zhao et al. detected 60 hard X-ray sources from the combined exposure of NuSTAR’s Cycle 5 and 6 observations. In this work, we utilize the NuSTAR Cycle 5+6+8+9 data and simultaneous XMM-Newton observations in order to perform the first spectroscopic analysis of the 60 source catalog. We present this analysis and measure the NH distribution of the sample. We measure an observed CT fraction of 0.13_(−0.04)^(+0.15) down to an observed 8–24 keV flux of 6.0 × 10−14 erg s cm−2, and we correct our analysis for absorption bias to estimate an underlying CT fraction of 0.32_(−0.08)^(+0.23). The derived obscuration distribution and CT fraction are consistent with population synthesis models and previous surveys.
",
"doi": "10.3847/1538-4357/ae196a",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-12-20",
"series_number": "2",
"volume": "995",
"issue": "2",
"pages": "203"
},
{
"id": "authors:rfmb2-mky04",
"collection": "authors",
"collection_id": "rfmb2-mky04",
"cite_using_url": "https://authors.library.caltech.edu/records/rfmb2-mky04",
"type": "article",
"title": "Hard X-Ray Emission in AU Mic Flares: A Minor Contributor to Planetary Atmospheric Escape",
"author": [
{
"family_name": "Hu",
"given_name": "Yifan",
"orcid": "0009-0006-2331-651X",
"clpid": "Hu-Yifan"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Favata",
"given_name": "Fabio",
"orcid": "0009-0001-8144-2526"
},
{
"family_name": "Pan",
"given_name": "Haiwu"
},
{
"family_name": "Grefenstette",
"given_name": "Brian",
"orcid": "0000-0002-1984-2932",
"clpid": "Grefenstette-B-W"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0003-2992-8024",
"clpid": "Harrison-F-A"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Yuan",
"given_name": "Weimin"
},
{
"family_name": "Yung",
"given_name": "Yuk L.",
"orcid": "0000-0002-4263-2562",
"clpid": "Yung-Y-L"
},
{
"family_name": "Zhao",
"given_name": "Xiurui",
"orcid": "0000-0002-7791-3671",
"clpid": "Zhao-Xiurui"
}
],
"abstract": "\n
Stellar flares are potent drivers of atmospheric evolution on orbiting exoplanets, primarily through extreme ultraviolet (EUV) and soft X-ray irradiation. However, the contribution of hard X-rays (HXR; 3–20 keV), which penetrate deeper into planetary atmospheres, to mass loss and particle acceleration has remained poorly understood. To quantify the HXR share of the total radiative budget, we conducted quasi-simultaneous observations of the active M-dwarf AU Mic using NuSTAR, Swift, and the Einstein Probe. Our analysis detected two major flares, and we performed an empirical check by deriving a quiescent-phase soft X-ray (SXR; 0.3–3 keV) to HXR relation and then applying it to the flares. By combining this with the quiescent coronal SXR–EUV relation conversion of J. Sanz-Forcada et al, we computed the total high-energy flux (EUV + SXR + HXR) and assessed the relative role of HXR in atmospheric escape. We find that HXR accounts for only a few percent of the total radiative energy budget during both quiescent and flaring states. While a high-energy spectral tail is detected in the second flare, time-resolved spectroscopy reveals a dominant chromospheric-evaporation signature, indicating that the flare energetics are primarily thermal.
\n