[
{
"id": "authors:tdfz4-53k08",
"collection": "authors",
"collection_id": "tdfz4-53k08",
"cite_using_url": "https://authors.library.caltech.edu/records/tdfz4-53k08",
"type": "article",
"title": "Fast X-Ray Transients in NuSTAR Data",
"author": [
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Jaimes",
"given_name": "Joahan Casta\u00f1eda",
"clpid": "Jaimes-Joahan-Casta\u00f1eda"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Grefenstette",
"given_name": "Brian",
"orcid": "0000-0002-1984-2932",
"clpid": "Grefenstette-B-W"
}
],
"abstract": "\n
Fast X-ray transients (FXTs) are flashes of X-rays that last for a few hundreds of seconds to a few hours. An enigmatic population of these transients that did not have a clear origin has been known for several decades, mostly found serendipitously in soft X-ray imaging observations. Recent progress in this field by the Einstein Probe has found that many FXTs are associated with gamma-ray bursts and the collapse of massive stars. Motivated by this, we searched the NuSTAR archive in the harder 3–79 keV band for ∼1000 s duration transients. From 204 Ms of exposure, we present five candidate FXTs, four of which are spectrally hard, with power-law indices −3 < Γ < 0, setting them apart from FXTs discovered in the soft band. Three have potential associations with galaxies at z = 0.1–2, implying 3–79 keV luminosities of 1043–1048 erg s−1 and volumetric event rates of 125–2900 Gpc−3 yr−1. The properties of these NuSTAR FXTs most resemble low-luminosity gamma-ray bursts and would be much more common than their higher-luminosity counterparts in this redshift range.
\n
\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
We present a series of five new broadband X-ray observations of the ultraluminous X-ray source Holmberg IX X-1, performed by XMM-Newton and NuSTAR in coordination. The first three of these show high soft X-ray fluxes but a near total collapse of the high-energy (\u227315 keV) emission, previously seen to be surprisingly stable across all prior broadband observations of the source. The latter two show a recovery in hard X-rays, remarkably once again respecting the same stable high-energy flux exhibited by all of the archival observations. We also present a joint analysis of all broadband observations of Holmberg IX X-1 to date (encompassing 11 epochs in total) in order to investigate whether it shows the same luminosity–temperature behaviour as NGC 1313 X-1 (which also shows a stable high-energy flux), whereby the hotter disc component in the spectrum exhibits two distinct, positively-correlated tracks in the luminosity–temperature plane. Holmberg IX X-1 may show similar behaviour, but the results depend on whether the highest energy emission is assumed to be an up-scattering corona or an accretion column. The strongest evidence for this behaviour is found in the former case, while in the latter the new 'soft' epochs appear distinct from the other high-flux epochs. We discuss possible explanations for these new 'soft' spectra in the context of the expected structure of super-Eddington accretion flows around black holes and neutron stars, and highlight a potentially interesting analogy with the recent destruction and re-creation of the corona seen in the AGN 1ES 1927+654.
",
"doi": "10.1093/mnras/staf1609",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-11",
"series_number": "3",
"volume": "543",
"issue": "3",
"pages": "2902-2916"
},
{
"id": "authors:e8d73-2zp08",
"collection": "authors",
"collection_id": "e8d73-2zp08",
"cite_using_url": "https://authors.library.caltech.edu/records/e8d73-2zp08",
"type": "article",
"title": "A massive gas outflow outside the line of sight: Imaging polarimetry of the blue excess Hot Dust-Obscured Galaxy W0204\u20130506",
"author": [
{
"family_name": "Assef",
"given_name": "R. J.",
"orcid": "0000-0002-9508-3667"
},
{
"family_name": "Stalevski",
"given_name": "M.",
"orcid": "0000-0001-5146-8330"
},
{
"family_name": "Armus",
"given_name": "L.",
"orcid": "0000-0003-3498-2973",
"clpid": "Armus-L"
},
{
"family_name": "Bauer",
"given_name": "F. E.",
"orcid": "0000-0002-8686-8737"
},
{
"family_name": "Blain",
"given_name": "A.",
"orcid": "0000-0001-7489-5167"
},
{
"family_name": "Brightman",
"given_name": "M.",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "D\u00edaz-Santos",
"given_name": "T.",
"orcid": "0000-0003-0699-6083"
},
{
"family_name": "Eisenhardt",
"given_name": "P. R. M.",
"clpid": "Eisenhardt-P-R-M"
},
{
"family_name": "Fern\u00e1ndez-Aranda",
"given_name": "R.",
"orcid": "0000-0002-7714-688X"
},
{
"family_name": "Jun",
"given_name": "H. D.",
"orcid": "0000-0003-1470-5901"
},
{
"family_name": "Liao",
"given_name": "M.",
"orcid": "0000-0002-9137-7019"
},
{
"family_name": "Li",
"given_name": "G.",
"orcid": "0000-0003-4007-5771"
},
{
"family_name": "Martin",
"given_name": "L. R.",
"orcid": "0000-0002-4950-7940"
},
{
"family_name": "Shablovinskaia",
"given_name": "E.",
"orcid": "0000-0003-2914-2507"
},
{
"family_name": "Shobhana",
"given_name": "D.",
"orcid": "0000-0002-5033-8056"
},
{
"family_name": "Stern",
"given_name": "D.",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Tsai",
"given_name": "C.-W.",
"orcid": "0000-0002-9390-9672"
},
{
"family_name": "Vayner",
"given_name": "A.",
"orcid": "0000-0002-0710-3729",
"clpid": "Vayner-Andrey"
},
{
"family_name": "Walton",
"given_name": "D. J.",
"orcid": "0000-0001-5819-3552"
},
{
"family_name": "Wu",
"given_name": "J.",
"orcid": "0000-0001-7808-3756"
},
{
"family_name": "Zewdie",
"given_name": "D.",
"orcid": "0000-0003-4293-7507"
}
],
"abstract": "Aims. Hot Dust-Obscured Galaxies (Hot DOGs) are a population of hyper-luminous, heavily obscured quasars. Although nearly Compton-thick nuclear obscurations are typical for Hot DOGs, a fraction show blue UV spectral energy distributions consistent with unobscured quasar activity, albeit two orders of magnitude fainter than expected from their mid-IR luminosity. The origin of the UV emission in these blue excess Hot DOGs (BHDs) has been linked to scattered light from the central engine. Here we study the properties of the UV emission in the BHD WISE J020446.13–050640.8 (W0204–0506).
\nMethods. We used imaging polarization observations in the RSpecial band obtained with the FORS2 instrument at VLT. We compared these data with radiative transfer simulations to constrain the characteristics of the scattering material.
\nResults. We find a spatially integrated polarization fraction of 24.7\u2005±\u20050.7%, confirming the scattered-light nature of the UV emission of W0204–0506. The source is spatially resolved in the observations, and we find a gradient in polarization fraction and angle that is aligned with the extended morphology of the source found in HST/WFC3 imaging. A dusty, conical polar outflow starting at the active galactic nucleus sublimation radius with a half-opening angle of \u227250\u2006deg viewed at an inclination \u227345\u2006deg can reproduce the observed polarization fraction if the dust is graphite-rich. We find that the gas mass and outflow velocity are consistent with the range of values found for [O\u202fIII] outflows through spectroscopy in other Hot DOGs, though it is unclear whether the outflow is energetic enough to affect the long-term evolution of the host galaxy. Our study highlights the unique potential of polarization imaging for studying dusty quasar outflows and providing complementary constraints to those obtained through traditional spectroscopic studies.
",
"doi": "10.1051/0004-6361/202555245",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2025-10",
"volume": "702",
"pages": "A124"
},
{
"id": "authors:abb5d-k2h91",
"collection": "authors",
"collection_id": "abb5d-k2h91",
"cite_using_url": "https://authors.library.caltech.edu/records/abb5d-k2h91",
"type": "article",
"title": "A NuSTAR Study of Quasiperiodic Oscillations from the Ultraluminous X-Ray Sources in M82",
"author": [
{
"family_name": "El Byad",
"given_name": "Hamza",
"orcid": "0009-0001-5473-4953"
},
{
"family_name": "Bachetti",
"given_name": "Matteo",
"orcid": "0000-0002-4576-9337"
},
{
"family_name": "Columbu",
"given_name": "Silvia",
"orcid": "0000-0001-5420-0719"
},
{
"family_name": "Rodriguez",
"given_name": "Giuseppe",
"orcid": "0000-0001-9054-8712"
},
{
"family_name": "Pilia",
"given_name": "Maura",
"orcid": "0000-0001-7397-8091"
},
{
"family_name": "Middleton",
"given_name": "Matthew J.",
"orcid": "0000-0002-8183-2970"
},
{
"family_name": "Walton",
"given_name": "Dominic J.",
"orcid": "0000-0001-5819-3552"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Earnshaw",
"given_name": "Hannah",
"orcid": "0000-0001-5857-5622",
"clpid": "Earnshaw-Hannah-P"
},
{
"family_name": "Forster",
"given_name": "Karl",
"orcid": "0000-0001-5800-5531",
"clpid": "Forster-K"
},
{
"family_name": "Grefenstette",
"given_name": "Brian",
"orcid": "0000-0002-1984-2932",
"clpid": "Grefenstette-B-W"
},
{
"family_name": "F\u00fcrst",
"given_name": "Felix"
},
{
"family_name": "Heida",
"given_name": "Marianne",
"orcid": "0000-0002-1082-7496"
},
{
"family_name": "Imbrogno",
"given_name": "Matteo",
"orcid": "0000-0001-8688-9784"
},
{
"family_name": "Lai",
"given_name": "Eleonora Veronica",
"orcid": "0000-0002-6421-2198"
},
{
"family_name": "Maccarone",
"given_name": "Thomas",
"orcid": "0000-0003-0976-4755"
}
],
"abstract": "\n
The study of quasiperiodic oscillations (QPOs) in X-ray binaries provides valuable insights into the physics of accretion around compact objects. The M82 galaxy hosts multiple ultraluminous X-ray sources, including two prominent ones—X-1 and X-2—where X-1 is suspected to harbor an intermediate-mass black hole. In this work, we analyze data from 39 NuSTAR observations acquired between 2014 and 2024 to investigate the aperiodic X-ray variability in M82. In particular, we study in detail the evolution of the QPOs from M82 X-1 in the range 20–300 mHz. We do not find additional timing features in the data, besides a frequently present broad noise component at lower frequencies. The QPO behaves similarly to other classes of low-frequency oscillations in accreting compact objects, both black holes and neutron stars.
\n
We present a census of the Compton-thick (CT) active galactic nucleus (AGN) population and the column density (N_H\u2060\u2060) distribution of AGN in our cosmic backyard using a mid-infrared selected AGN sample within 15 Mpc. The column densities are measured from broad-band X-ray spectral analysis, mainly using data from Chandra and NuSTAR. Our sample probes AGN with intrinsic 2–10 keV luminosities of L\u2082\u208b\u2081\u2080,int = 10³\u2077-10\u2074³ erg s\u207b¹, reaching a parameter space inaccessible to more distant samples. We directly measure a 32\u207a³\u2070\u208b\u2081\u2088 CT AGN fraction and obtain an N_H distribution that agrees with that inferred by the Swift-BAT survey. Restricting the sample to the largely unexplored domain of low-luminosity AGN with L\u2082\u208b\u2081\u2080,int ≤ 10\u2074² erg s\u207b¹\u2060, we found a CT fraction of \u206019\u207a³\u2070\u208b\u2081\u2084 per cent, consistent with those observed at higher luminosities. Comparing the host-galaxy properties between the two samples, we find consistent star formation rates, though the majority of our galaxy have lower stellar masses (by ≈ 0.3 dex). In contrast, the two samples have very different black hole mass (M_(BH)\u2060\u2060) distributions, with our sample having ≈ 1.5 dex lower mean mass (M_(BH)\u2060 ~10\u2076 M\u2299\u2060). Additionally, our sample contains a significantly higher number of LINERs and H ii-type nuclei. The Eddington ratio range probed by our sample, however, is the same as Swift-BAT, although the latter dominates at higher accretion rates, and our sample is more evenly distributed. The majority of our sample with λEdd ≥ 10\u207b³ tend to be CT, while those with λEdd < 10\u207b³ are mostly unobscured or mildly obscured.
",
"doi": "10.1093/mnras/staf956",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-07",
"series_number": "4",
"volume": "540",
"issue": "4",
"pages": "3827-3849"
},
{
"id": "authors:6qs87-63c17",
"collection": "authors",
"collection_id": "6qs87-63c17",
"cite_using_url": "https://authors.library.caltech.edu/records/6qs87-63c17",
"type": "article",
"title": "Discovery of extreme quasi-periodic eruptions in a newly accreting massive black hole",
"author": [
{
"family_name": "Hern\u00e1ndez-Garc\u00eda",
"given_name": "Lorena",
"orcid": "0000-0002-8606-6961"
},
{
"family_name": "Chakraborty",
"given_name": "Joheen",
"orcid": "0000-0002-0568-6000"
},
{
"family_name": "S\u00e1nchez-S\u00e1ez",
"given_name": "Paula",
"orcid": "0000-0003-0820-4692"
},
{
"family_name": "Ricci",
"given_name": "Claudio",
"orcid": "0000-0001-5231-2645"
},
{
"family_name": "Cuadra",
"given_name": "Jorge",
"orcid": "0000-0003-1965-3346"
},
{
"family_name": "McKernan",
"given_name": "Barry",
"orcid": "0000-0002-9726-0508"
},
{
"family_name": "Ford",
"given_name": "K. E. Saavik",
"orcid": "0000-0002-5956-851X"
},
{
"family_name": "Ar\u00e9valo",
"given_name": "Patricia",
"orcid": "0000-0001-5675-6323"
},
{
"family_name": "Rau",
"given_name": "Arne",
"orcid": "0000-0001-5990-6243"
},
{
"family_name": "Arcodia",
"given_name": "Riccardo",
"orcid": "0000-0003-4054-7978"
},
{
"family_name": "Kara",
"given_name": "Erin",
"orcid": "0000-0003-0172-0854"
},
{
"family_name": "Liu",
"given_name": "Zhu"
},
{
"family_name": "Merloni",
"given_name": "Andrea",
"orcid": "0000-0002-0761-0130"
},
{
"family_name": "Bruni",
"given_name": "Gabriele",
"orcid": "0000-0002-5182-6289"
},
{
"family_name": "Goodwin",
"given_name": "Adelle",
"orcid": "0000-0003-3441-8299"
},
{
"family_name": "Arzoumanian",
"given_name": "Zaven",
"orcid": "0009-0008-6187-8753"
},
{
"family_name": "Assef",
"given_name": "Roberto J.",
"orcid": "0000-0002-9508-3667"
},
{
"family_name": "Baldini",
"given_name": "Pietro",
"orcid": "0009-0002-5164-3279"
},
{
"family_name": "Bayo",
"given_name": "Amelia",
"orcid": "0000-0001-7868-7031"
},
{
"family_name": "Bauer",
"given_name": "Franz E.",
"orcid": "0000-0002-8686-8737"
},
{
"family_name": "Bernal",
"given_name": "Santiago",
"orcid": "0000-0002-3519-3231"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Calistro Rivera",
"given_name": "Gabriela",
"orcid": "0000-0003-0085-6346"
},
{
"family_name": "Gendreau",
"given_name": "Keith",
"orcid": "0000-0001-7115-2819"
},
{
"family_name": "Homan",
"given_name": "David",
"orcid": "0000-0002-3243-874X"
},
{
"family_name": "Krumpe",
"given_name": "Mirko"
},
{
"family_name": "Lira",
"given_name": "Paulina",
"orcid": "0000-0003-1523-9164"
},
{
"family_name": "Mart\u00ednez-Aldama",
"given_name": "Mary Loli",
"orcid": "0000-0002-7843-7689"
},
{
"family_name": "Salvato",
"given_name": "Mara",
"orcid": "0000-0001-7116-9303"
},
{
"family_name": "Sotomayor",
"given_name": "Bel\u00e9n"
}
],
"abstract": "Quasi-periodic eruptions (QPEs) are rapid, recurring X-ray bursts from supermassive black holes, believed to result from interactions between accretion disks and surrounding matter. The galaxy SDSS1335+0728, previously stable for two decades, exhibited an increase in optical brightness in December 2019, followed by persistent active galactic nucleus (AGN)-like variability for 5 yr, suggesting the activation of a ~106-M\u2299 black hole. Since February 2024, X-ray emission has been detected, revealing extreme ~4.5-d QPEs with high fluxes and amplitudes, long timescales, large integrated energies and a ~25-d superperiod. Low-significance UV variations are reported, probably related to the long timescales and large radii from which the emission originates. This discovery broadens the possible formation channels for QPEs, suggesting that they are linked not solely to tidal disruption events but more generally to newly formed accretion flows, which we are witnessing in real time in a turn-on AGN candidate.
",
"doi": "10.1038/s41550-025-02523-9",
"issn": "2397-3366",
"publisher": "Nature Publishing Group",
"publication": "Nature Astronomy",
"publication_date": "2025-06",
"series_number": "6",
"volume": "9",
"issue": "6",
"pages": "895-906"
},
{
"id": "authors:0zebt-y7a32",
"collection": "authors",
"collection_id": "0zebt-y7a32",
"cite_using_url": "https://authors.library.caltech.edu/records/0zebt-y7a32",
"type": "article",
"title": "The NuSTAR Local AGN N_H Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe",
"author": [
{
"family_name": "Boorman",
"given_name": "Peter G.",
"orcid": "0000-0001-9379-4716",
"clpid": "Boorman-Peter-G"
},
{
"family_name": "Gandhi",
"given_name": "Poshak",
"orcid": "0000-0003-3105-2615"
},
{
"family_name": "Buchner",
"given_name": "Johannes",
"orcid": "0000-0003-0426-6634"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Ricci",
"given_name": "Claudio",
"orcid": "0000-0001-5231-2645"
},
{
"family_name": "Balokovi\u0107",
"given_name": "Mislav",
"orcid": "0000-0003-0476-6647"
},
{
"family_name": "Asmus",
"given_name": "Daniel",
"orcid": "0000-0003-0220-2063"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0002-4226-8959",
"clpid": "Harrison-F-A"
},
{
"family_name": "Svoboda",
"given_name": "Ji\u0159\u00ed",
"orcid": "0000-0003-2931-0742"
},
{
"family_name": "Greenwell",
"given_name": "Claire",
"orcid": "0000-0002-7719-5809"
},
{
"family_name": "Koss",
"given_name": "Michael J.",
"orcid": "0000-0002-7998-9581"
},
{
"family_name": "Alexander",
"given_name": "David M.",
"orcid": "0000-0002-5896-6313"
},
{
"family_name": "Annuar",
"given_name": "Adlyka",
"orcid": "0000-0003-0387-1429"
},
{
"family_name": "Bauer",
"given_name": "Franz E.",
"orcid": "0000-0002-8686-8737"
},
{
"family_name": "Brandt",
"given_name": "William N.",
"orcid": "0000-0002-0167-2453"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Civano",
"given_name": "Francesca",
"orcid": "0000-0002-2115-1137"
},
{
"family_name": "Chen",
"given_name": "Chien-Ting J.",
"orcid": "0000-0002-4945-5079"
},
{
"family_name": "Farrah",
"given_name": "Duncan",
"orcid": "0000-0003-1748-2010"
},
{
"family_name": "Forster",
"given_name": "Karl",
"orcid": "0000-0001-5800-5531",
"clpid": "Forster-Karl"
},
{
"family_name": "Grefenstette",
"given_name": "Brian",
"orcid": "0000-0002-1984-2932",
"clpid": "Grefenstette-Brian"
},
{
"family_name": "H\u00f6nig",
"given_name": "Sebastian F.",
"orcid": "0000-0002-6353-1111"
},
{
"family_name": "Hill",
"given_name": "Adam B.",
"orcid": "0000-0003-3470-4834"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X"
},
{
"family_name": "Lansbury",
"given_name": "George",
"orcid": "0000-0002-5328-9827"
},
{
"family_name": "Lanz",
"given_name": "Lauranne",
"orcid": "0000-0002-3249-8224"
},
{
"family_name": "LaMassa",
"given_name": "Stephanie",
"orcid": "0000-0002-5907-3330"
},
{
"family_name": "Madsen",
"given_name": "Kristin",
"orcid": "0000-0003-1252-4891"
},
{
"family_name": "Marchesi",
"given_name": "Stefano",
"orcid": "0000-0001-5544-0749"
},
{
"family_name": "Middleton",
"given_name": "Matthew",
"orcid": "0000-0002-8183-2970"
},
{
"family_name": "Mingo",
"given_name": "Beatriz",
"orcid": "0000-0001-5649-938X"
},
{
"family_name": "Parker",
"given_name": "Michael L.",
"orcid": "0000-0002-8466-7317"
},
{
"family_name": "Treister",
"given_name": "Ezequiel",
"orcid": "0000-0001-7568-6412"
},
{
"family_name": "Ueda",
"given_name": "Yoshihiro",
"orcid": "0000-0001-7821-6715"
},
{
"family_name": "Urry",
"given_name": "C. Megan",
"orcid": "0000-0002-0745-9792"
},
{
"family_name": "Zappacosta",
"given_name": "Luca",
"orcid": "0000-0002-4205-6884"
}
],
"abstract": "\n
Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of NH > 1024 cm−2. To tackle this issue, we present the NuSTAR Local AGN NH Distribution Survey (NuLANDS)—a legacy sample of 122 nearby (z < 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 μm. We show that optically classified Type 1 and 2 AGN in NuLANDS are indistinguishable in terms of optical [O iii] line flux and mid-to-far-infrared AGN continuum bolometric indicators, as expected from an isotropically selected AGN sample, while Type 2 AGN are deficient in terms of their observed hard X-ray flux. By testing many X-ray spectroscopic models, we show the measured line-of-sight column density varies on average by ∼1.4 orders of magnitude depending on the obscurer geometry. To circumvent such issues, we propagate the uncertainties per source into the parent column density distribution, finding a directly measured Compton-thick fraction of 35% ± 9%. By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration. This bias implies an even higher intrinsic obscured AGN fraction may be possible, although tests for additional biases arising from our infrared selection find no strong effects on the measured column density distribution. NuLANDS thus holds potential as an optimized sample for future follow-up with current and next-generation instruments aiming to study the local AGN population in an isotropic manner.
\n
Recent models suggest approximately half of all accreting supermassive black holes (SMBHs; MBH \u2273 105M\u2299) are expected to undergo intense growth phases behind Compton-thick (NH > 1.5 × 1024 cm−2) veils of obscuring gas. However, despite being a viable source for the seeding of SMBHs, there are currently no examples known of a Compton-thick accreting intermediate-mass black hole (IMBH; MBH ∼ 102–105M\u2299). We present a detailed X-ray spectral analysis of IC 750—the only active galactic nuclei (AGN) to date with a precise megamaser-based intermediate mass <105M\u2299. We find the equivalent width of neutral 6.4 keV Fe Kα to be 1.9_(−1.0)^(+2.2) keV via phenomenological modeling of the coadded 177 ks Chandra spectrum. Such large equivalent widths are seldom produced by processes other than fluorescence from dense obscuration. We fit three physically motivated X-ray spectral models to infer a range of possible intrinsic 2–10 keV luminosity posteriors that encompass the systematic uncertainties associated with a choice of model. Despite a wide range of predicted intrinsic 2–10 keV luminosities between ∼ 1041 and 1043 erg s−1, all three models agree that IC 750 has a Compton-thick line-of-sight column density to >99% confidence. Compton-thick obscuration is well-documented to impinge substantial bias on the pursuit of SMBH AGN. Our results thus provide the first indication that Compton-thick obscuration should also be properly considered to uncover and understand the IMBH population in an unbiased manner.
",
"doi": "10.3847/1538-4357/ad7f56",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2024-11-10",
"series_number": "2",
"volume": "975",
"issue": "2",
"pages": "230"
},
{
"id": "authors:0xd01-3zz12",
"collection": "authors",
"collection_id": "0xd01-3zz12",
"cite_using_url": "https://authors.library.caltech.edu/records/0xd01-3zz12",
"type": "article",
"title": "SDSS1335+0728: The awakening of a ~10\u2076 M\u2299 black hole",
"author": [
{
"family_name": "S\u00e1nchez-S\u00e1ez",
"given_name": "P.",
"orcid": "0000-0003-0820-4692",
"clpid": "S\u00e1nchez-S\u00e1ez-Paula"
},
{
"family_name": "Hernandez-Garcia",
"given_name": "L.",
"orcid": "0000-0002-8606-6961",
"clpid": "Hernandez-Garcia-Lorena"
},
{
"family_name": "Bernal",
"given_name": "S.",
"clpid": "Bernal-S"
},
{
"family_name": "Bayo",
"given_name": "A.",
"orcid": "0000-0001-7868-7031",
"clpid": "Bayo-Amelia"
},
{
"family_name": "Calistro Rivera",
"given_name": "G.",
"orcid": "0000-0003-0085-6346",
"clpid": "Calistro-Rivera-Gabriela"
},
{
"family_name": "Bauer",
"given_name": "F. E.",
"orcid": "0000-0002-8686-8737",
"clpid": "Bauer-Franz-Erik"
},
{
"family_name": "Ricci",
"given_name": "C.",
"orcid": "0000-0001-5231-2645",
"clpid": "Ricci-Claudio"
},
{
"family_name": "Merloni",
"given_name": "A.",
"orcid": "0000-0002-0761-0130",
"clpid": "Merloni-Andrea"
},
{
"family_name": "Graham",
"given_name": "M. J.",
"orcid": "0000-0002-3168-0139",
"clpid": "Graham-M-J"
},
{
"family_name": "Cartier",
"given_name": "R.",
"orcid": "0000-0003-4553-4033",
"clpid": "Cartier-Regis"
},
{
"family_name": "Ar\u00e9valo",
"given_name": "P.",
"orcid": "0000-0001-8503-9809",
"clpid": "Ar\u00e9valo-Patricia"
},
{
"family_name": "Assef",
"given_name": "R. J.",
"orcid": "0000-0002-9508-3667",
"clpid": "Assef-Roberto-J"
},
{
"family_name": "Concas",
"given_name": "A.",
"orcid": "0000-0003-3203-9818",
"clpid": "Concas-Alice"
},
{
"family_name": "Homan",
"given_name": "D.",
"orcid": "0000-0002-3243-874X",
"clpid": "Homan-David"
},
{
"family_name": "Krumpe",
"given_name": "M.",
"clpid": "Krumpe-M"
},
{
"family_name": "Lira",
"given_name": "P.",
"orcid": "0000-0003-1523-9164",
"clpid": "Lira-Paulina"
},
{
"family_name": "Malyali",
"given_name": "A.",
"orcid": "0000-0002-8851-4019",
"clpid": "Malyali-Adam"
},
{
"family_name": "Mart\u00ednez-Aldama",
"given_name": "M. L.",
"orcid": "0000-0002-7843-7689",
"clpid": "Mart\u00ednez-Aldama-Mary-Loli"
},
{
"family_name": "Mu\u00f1oz Arancibia",
"given_name": "A. M.",
"orcid": "0000-0002-8722-516X",
"clpid": "Mu\u00f1oz-Arancibia-Alejandra-M"
},
{
"family_name": "Rau",
"given_name": "A.",
"orcid": "0000-0001-5990-6243",
"clpid": "Rau-Arne"
},
{
"family_name": "Bruni",
"given_name": "G.",
"orcid": "0000-0002-5182-6289",
"clpid": "Bruni-Gabriele"
},
{
"family_name": "F\u00f6rster",
"given_name": "F.",
"orcid": "0000-0003-3459-2270",
"clpid": "F\u00f6rster-Francisco"
},
{
"family_name": "Pavez-Herrera",
"given_name": "M.",
"clpid": "Pavez-Herrera-M"
},
{
"family_name": "Tub\u00edn-Arenas",
"given_name": "D.",
"orcid": "0000-0002-2688-7960",
"clpid": "Tub\u00edn-Arenas-Dus\u00e1n"
},
{
"family_name": "Brightman",
"given_name": "M.",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
}
],
"abstract": "Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼106\u2006M\u2299 black hole (BH) that is currently in the process of “turning on”.
\nAims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728.
\nMethods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra.
\nResults. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1\u2005−\u2005W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region.
\nConclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼106\u2006M\u2299 AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGN observed in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour.
",
"doi": "10.1051/0004-6361/202347957",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2024-08",
"volume": "688",
"pages": "A157"
},
{
"id": "authors:88y42-wcd73",
"collection": "authors",
"collection_id": "88y42-wcd73",
"cite_using_url": "https://authors.library.caltech.edu/records/88y42-wcd73",
"type": "article",
"title": "Return to the Forgotten Ultraluminous X-Ray Source: A Broadband NICER+NuSTAR Study of NGC 4190 ULX-1",
"author": [
{
"family_name": "Earnshaw",
"given_name": "Hannah P.",
"orcid": "0000-0001-5857-5622",
"clpid": "Earnshaw-Hannah-P"
},
{
"family_name": "Bachetti",
"given_name": "Matteo",
"orcid": "0000-0002-4576-9337",
"clpid": "Bachetti-Matteo"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "F\u00fcrst",
"given_name": "Felix",
"orcid": "0000-0003-0388-0560",
"clpid": "F\u00fcrst-Felix"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0002-4226-8959"
},
{
"family_name": "Middleton",
"given_name": "Matthew",
"orcid": "0000-0002-8183-2970",
"clpid": "Middleton-Matthew"
},
{
"family_name": "Ludlam",
"given_name": "Renee",
"orcid": "0000-0002-8961-939X",
"clpid": "Ludlam-Renee"
},
{
"family_name": "Pike",
"given_name": "Sean N.",
"orcid": "0000-0002-8403-0041",
"clpid": "Pike-Sean-N"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Walton",
"given_name": "Dominic J.",
"orcid": "0000-0001-5819-3552",
"clpid": "Walton-Dominic-J"
}
],
"abstract": "\n
We observed the nearby and relatively understudied ultraluminous X-ray source (ULX) NGC 4190 ULX-1 jointly with Neutron Star Interior Composition Explorer (NICER) and NuSTAR to investigate its broadband spectrum, timing properties, and spectral variation over time. We found NGC 4190 ULX-1 to have a hard spectrum characterized by two thermal components (with temperatures ∼0.25 and ∼1.6 keV) and a high-energy excess typical of the ULX population although the spectrum turns over at an unusually low energy. While no pulsations were detected (with pulsed fraction 3σ upper limits of 16% for NICER and 35% for NuSTAR), the source shows significant stochastic variability, and the covariance spectrum indicates the presence of a high-energy cutoff power-law component, potentially indicative of an accretion column. Additionally, when fitting archival XMM-Newton data with a similar model, we find that the luminosity–temperature evolution of the hot thermal component follows the behavior of a super-Eddington slim disk though the expected spectral broadening for such a disk is not seen, suggesting that the inner accretion disk may be truncated by a magnetic field. Therefore, despite the lack of detected pulsations, there is tantalizing evidence for NGC 4190 ULX-1 being a candidate neutron star accretor although further broadband observations will be required to confirm this behavior.
\n
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ~10\u2076 M\u2299 black hole (BH) that is currently in the process of ‘turning on’.
\nAims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728.
\nMethods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra.
\nResults. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region.
\nConclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ~10\u2076 M\u2299 AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGN observed in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour.
",
"doi": "10.1051/0004-6361/202347957",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2024-06-18"
},
{
"id": "authors:h2012-2en81",
"collection": "authors",
"collection_id": "h2012-2en81",
"cite_using_url": "https://authors.library.caltech.edu/records/h2012-2en81",
"type": "article",
"title": "NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes",
"author": [
{
"family_name": "Saade",
"given_name": "M. Lynne",
"orcid": "0000-0001-7163-7015",
"clpid": "Saade-M-Lynne"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Connor",
"given_name": "Thomas",
"orcid": "0000-0002-7898-7664",
"clpid": "Connor-Thomas"
},
{
"family_name": "Djorgovski",
"given_name": "S. G.",
"orcid": "0000-0002-0603-3087",
"clpid": "Djorgovski-S-G"
},
{
"family_name": "D'Orazio",
"given_name": "Daniel J.",
"orcid": "0000-0002-1271-6247",
"clpid": "D'Orazio-Daniel-J"
},
{
"family_name": "Ford",
"given_name": "K. E. S.",
"orcid": "0000-0002-5956-851X",
"clpid": "Foord-K-E-Saavik"
},
{
"family_name": "Graham",
"given_name": "Matthew J.",
"orcid": "0000-0002-3168-0139",
"clpid": "Graham-M-J"
},
{
"family_name": "Haiman",
"given_name": "Zolt\u00e1n",
"orcid": "0000-0003-3633-5403",
"clpid": "Haiman-Zolt\u00e1n"
},
{
"family_name": "Jun",
"given_name": "Hyunsung D.",
"orcid": "0000-0003-1470-5901",
"clpid": "Jun-Hyunsung-D"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Kraft",
"given_name": "Ralph P.",
"orcid": "0000-0002-0765-0511",
"clpid": "Kraft-Ralph-P"
},
{
"family_name": "McKernan",
"given_name": "Barry",
"orcid": "0000-0002-9726-0508",
"clpid": "McKernan-Barry"
},
{
"family_name": "Vikhlinin",
"given_name": "Alexei",
"orcid": "0000-0001-8121-0234",
"clpid": "Vikhlinin-Alexei"
},
{
"family_name": "Walton",
"given_name": "Dominic J.",
"orcid": "0000-0001-5819-3552",
"clpid": "Walton-Dominic-J"
}
],
"abstract": "\n
We present an analysis of NuSTAR X-ray observations of three active galactic nuclei (AGN) that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs. We previously observed these AGN with Chandra and found no differences between their low-energy X-ray properties and the larger AGN population. However, some models predict differences to be more prominent at energies higher than probed by Chandra. We find that even at the higher energies probed by NuSTAR, the spectra of these AGN are indistinguishable from the larger AGN population. This could rule out models predicting large differences in the X-ray spectra in the NuSTAR bands. Alternatively, it might mean that these three AGN are not binary SMBHs.
\n
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10′′ FWHM) and broad spectral coverage (0.2–80 keV) with an effective area superior to NuSTAR above 10 keV to enable revolutionary new insights into a variety of astrophysical problems, especially those related to compact objects, accretion and outflows. HEX-P will launch at a time when the sky is being routinely scanned for transient gravitational wave, electromagnetic and neutrino phenomena that will require the capabilities of a sensitive, broadband X-ray telescope for follow up studies. These include the merger of compact objects such as neutron stars and black holes, stellar explosions, and the birth of new compact objects. A response time to target of opportunity observation requests of <24 hours and a field of regard of 3π steradians will allow HEX-P to probe the accretion and ejecta from these transient phenomena through the study of relativistic outflows and reprocessed emission, provide unique capabilities for understanding jet physics, and potentially revealing the nature of the central engine.
",
"doi": "10.3389/fspas.2023.1292656",
"issn": "2296-987X",
"publisher": "Frontiers Media SA",
"publication": "Frontiers in Astronomy and Space Sciences",
"publication_date": "2024-01-09",
"volume": "10",
"pages": "1292656"
},
{
"id": "authors:qs1n3-0t817",
"collection": "authors",
"collection_id": "qs1n3-0t817",
"cite_using_url": "https://authors.library.caltech.edu/records/qs1n3-0t817",
"type": "article",
"title": "Early Hard X-Rays from the Nearby Core-collapse Supernova SN 2023ixf",
"author": [
{
"family_name": "Grefenstette",
"given_name": "Brian W.",
"orcid": "0000-0002-1984-2932",
"clpid": "Grefenstette-Brian-F"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Earnshaw",
"given_name": "Hannah P.",
"orcid": "0000-0001-5857-5622",
"clpid": "Earnshaw-Hannah-P"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0002-4226-8959",
"clpid": "Harrison-F-A"
},
{
"family_name": "Margutti",
"given_name": "R.",
"orcid": "0000-0003-4768-7586",
"clpid": "Margutti-Raffaella"
}
],
"abstract": "We present NuSTAR observations of the nearby SN 2023ixf in M101 (d = 6.9 Mpc) that provide the earliest hard X-ray detection of a nonrelativistic stellar explosion to date at δt ≈ 4 days and δt ≈ 11 days. The spectra are well described by a hot thermal bremsstrahlung continuum with T > 25 keV shining through a thick neutral medium with a neutral hydrogen column that decreases with time (initial NHint = 2.6 × 1023 cm−2). A prominent neutral Fe Kα emission line is clearly detected, similar to other strongly interacting supernovae (SNe) such as SN 2010jl. The rapidly decreasing intrinsic absorption with time suggests the presence of a dense but confined circumstellar medium (CSM). The absorbed broadband X-ray luminosity (0.3–79 keV) is LX ≈ 2.5 × 1040 erg s−1 during both epochs, with the increase in overall X-ray flux related to the decrease in the absorbing column. Interpreting these observations in the context of thermal bremsstrahlung radiation originating from the interaction of the SN shock with a dense medium we infer large particle densities in excess of nCSM ≈ 4 × 108 cm−3 at r < 1015 cm, corresponding to an enhanced progenitor mass-loss rate of \u1e40 ≈ 3 × 10\u207b\u2074 M\u2299 yr−1 for an assumed wind velocity of vw = 50 km s−1.
",
"doi": "10.3847/2041-8213/acdf4e",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-07-20",
"series_number": "1",
"volume": "952",
"issue": "1",
"pages": "L3"
},
{
"id": "authors:79w2q-rkc11",
"collection": "authors",
"collection_id": "79w2q-rkc11",
"cite_using_url": "https://authors.library.caltech.edu/records/79w2q-rkc11",
"type": "article",
"title": "SN2019wxt: An Ultrastripped Supernova Candidate Discovered in the Electromagnetic Follow-up of a Gravitational Wave Trigger",
"author": [
{
"family_name": "Shivkumar",
"given_name": "Hinna",
"orcid": "0000-0001-9289-0570",
"clpid": "Shivkumar-Hinna"
},
{
"family_name": "Jaodand",
"given_name": "Amruta D.",
"orcid": "0000-0002-3850-6651",
"clpid": "Jaodand-Amruta-D"
},
{
"family_name": "Balasubramanian",
"given_name": "Arvind",
"orcid": "0000-0003-0477-7645",
"clpid": "Balasubramanian-Arvind"
},
{
"family_name": "Fremling",
"given_name": "Christoffer",
"orcid": "0000-0002-4223-103X",
"clpid": "Fremling-Christoffer"
},
{
"family_name": "Corsi",
"given_name": "Alessandra",
"orcid": "0000-0001-8104-3536",
"clpid": "Corsi-Alessandra"
},
{
"family_name": "Tzanidakis",
"given_name": "Anastasios",
"orcid": "0000-0003-0484-3331",
"clpid": "Tzanidakis-Anastasios"
},
{
"family_name": "Nissanke",
"given_name": "Samaya",
"orcid": "0000-0001-6573-7773",
"clpid": "Nissanke-Samaya"
},
{
"family_name": "Kasliwal",
"given_name": "Mansi",
"orcid": "0000-0002-5619-4938",
"clpid": "Kasliwal-M-M"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Raaijmakers",
"given_name": "Geert",
"orcid": "0000-0002-9397-786X",
"clpid": "Raaijmakers-Geert"
},
{
"family_name": "Madsen",
"given_name": "Kristin Kruse",
"orcid": "0000-0003-1252-4891",
"clpid": "Madsen-Kristin-K"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0002-4226-8959",
"clpid": "Harrison-F-A"
},
{
"family_name": "Carbone",
"given_name": "Dario",
"orcid": "0000-0002-6575-4642",
"clpid": "Carbone-Dario"
},
{
"family_name": "A. J.",
"given_name": "Nayana",
"orcid": "0000-0002-8070-5400",
"clpid": "A-J-Nayana"
},
{
"family_name": "D\u00e9sert",
"given_name": "Jean-Michel",
"orcid": "0000-0002-0875-8401",
"clpid": "D\u00e9sert-Jean-Michel"
},
{
"family_name": "Andreoni",
"given_name": "Igor",
"orcid": "0000-0002-8977-1498",
"clpid": "Andreoni-Igor"
}
],
"abstract": "\n
We present optical, radio, and X-ray observations of a rapidly evolving transient SN2019wxt (PS19hgw), discovered during the search for an electromagnetic counterpart to the gravitational-wave (GW) trigger S191213g. Although S191213g was not confirmed as a significant GW event in the off-line analysis of LIGO-Virgo data, SN2019wxt remained an interesting transient due to its peculiar nature. The optical/near-infrared (NIR) light curve of SN2019wxt displayed a double-peaked structure evolving rapidly in a manner analogous to currently known ultrastripped supernovae (USSNe) candidates. This double-peaked structure suggests the presence of an extended envelope around the progenitor, best modeled with two components: (i) early-time shock-cooling emission and (ii) late-time radioactive 56Ni decay. We constrain the ejecta mass of SN2019wxt at Mej ≈ 0.20M\u2299, which indicates a significantly stripped progenitor that was possibly in a binary system. We also followed up SN2019wxt with long-term Chandra and Jansky Very Large Array observations spanning ∼260 days. We detected no definitive counterparts at the location of SN2019wxt in these long-term X-ray and radio observational campaigns. We establish the X-ray upper limit at 9.93 × 10−17 erg cm−2 s−1 and detect an excess radio emission from the region of SN2019wxt. However, there is little evidence for SN1993J- or GW170817-like variability of the radio flux over the course of our observations. A substantial host-galaxy contribution to the measured radio flux is likely. The discovery and early-time peak capture of SN2019wxt in optical/NIR observations during EMGW follow-up observations highlight the need for dedicated early, multiband photometric observations to identify USSNe.
\n