61 research outputs found
An ADA model of the AEGIS radar scheduler.
http://archive.org/details/adamodelofaegisr00purdN
Searching for late-time interaction signatures in Type Ia supernovae from the Zwicky Transient Facility
The nature of the progenitor systems and explosion mechanisms that give rise
to Type Ia supernovae (SNe Ia) are still debated. The interaction signature of
circumstellar material (CSM) being swept up by expanding ejecta can constrain
the type of system from which it was ejected. Most previous studies have
focused on finding CSM ejected shortly before the SN Ia explosion still
residing close to the explosion site, resulting in short delay times until the
interaction starts. We use a sample of 3627 SNe Ia from the Zwicky Transient
Facility discovered between 2018 and 2020 and search for interaction signatures
over 100 days after peak brightness. By binning the late-time light curve data
to push the detection limit as deep as possible, we identify potential
late-time rebrightening in 3 SNe Ia (SN 2018grt, SN 2019dlf, SN 2020tfc). The
late-time detections occur between 550 and 1450 d after peak brightness, have
mean absolute -band magnitudes of -16.4 to -16.8 mag and last up to a few
hundred days, significantly brighter than the late-time CSM interaction
discovered in the prototype SN 2015cp. The late-time detections all occur
within 0.8 kpc of the host nucleus and are not easily explained by nuclear
activity, another transient at a similar sky position, or data quality issues.
This suggests environment or specific progenitor characteristics playing a role
in producing potential CSM signatures in these SNe Ia. By simulating the ZTF
survey we estimate that <0.5 per cent of normal SNe Ia display late-time strong
H -dominated CSM interaction. This is equivalent to an absolute rate of
to Gpc yr assuming a constant SN
Ia rate of Mpc yr for . Weaker
interaction signatures, more similar to the strength seen in SN 2015cp, could
be more common but are difficult to constrain with our survey depth.Comment: 24 pages, 13 figures, 6 tables, A&A accepte
SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation
We present observations of SN 2022joj, a peculiar Type Ia supernova (SN Ia)
discovered by the Zwicky Transient Facility (ZTF). SN 2022joj exhibits an
unusually red color at early times and a rapid
blueward evolution afterwards. Around maximum brightness, SN 2022joj shows a
high luminosity ( mag), a blue
broadband color ( mag), and shallow Si
II absorption lines, consistent with those of overluminous, SN 1991T-like
events. The maximum-light spectrum also shows prominent absorption around 4200
\r{A}, which resembles the Ti II features in subluminous, SN 1991bg-like
events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red
ultraviolet optical colors at maximum luminosity ( mag and
mag), suggesting a suppression of flux between
2500--4000 \r{A}. Strong C II lines are also detected at peak. We show
that these unusual spectroscopic properties are broadly consistent with the
helium-shell double detonation of a sub-Chandrasekhar mass
() carbon/oxygen (C/O) white dwarf (WD) from a
relatively massive helium shell (--), if
observed along a line of sight roughly opposite to where the shell initially
detonates. None of the existing models could quantitatively explain all the
peculiarities observed in SN 2022joj. The low flux ratio of [Ni II]
7378 to [Fe II] 7155 emission in the late-time nebular
spectra indicates a low yield of stable Ni isotopes, favoring a
sub-Chandrasekhar mass progenitor. The significant blueshift measured in the
[Fe II] 7155 line is also consistent with an asymmetric chemical
distribution in the ejecta, as is predicted in double-detonation models.Comment: 24 pages, 11 figures, 6 tables. Submitted to Ap
A kilometer-scale asteroid inside Venus's orbit
Near-Earth asteroid population models predict the existence of asteroids located inside the orbit of Venus. However, despite searches up to the end of 2019, none have been found. Here we report the discovery by the Zwicky Transient Facility of the first known asteroid located inside of Venus' orbit, 2020 AVā, possessing an aphelion distance of 0.65 au and ā¼2 km in size. While it is possible that 2020 AVā is the largest of its kind, we find that its discovery is surprising in the context of population models where the expected count is close to zero. If this discovery is not a statistical fluke, then 2020 AVā may come from a yet undiscovered source population of asteroids interior to Venus, and currently favored asteroid population models may need to be adjusted
A kilometer-scale asteroid inside Venus's orbit
Near-Earth asteroid population models predict the existence of asteroids located inside the orbit of Venus. However, despite searches up to the end of 2019, none have been found. Here we report the discovery by the Zwicky Transient Facility of the first known asteroid located inside of Venus' orbit, 2020 AVā, possessing an aphelion distance of 0.65 au and ā¼2 km in size. While it is possible that 2020 AVā is the largest of its kind, we find that its discovery is surprising in the context of population models where the expected count is close to zero. If this discovery is not a statistical fluke, then 2020 AVā may come from a yet undiscovered source population of asteroids interior to Venus, and currently favored asteroid population models may need to be adjusted
Religious Diversity and Conceptual Schemes: Critically Appraising Internalist Pluralism
Is a philosophical theory needed to āunderwriteā attitudes of toleration and respect in a multicultural and religiously diverse world? Many philosophers of religion have thought so, including Victoria Harrison. This article interrogates Harrisonās theory of internalist pluralism, which, though offering a welcome alternative to other theories, such as John Hickās āpluralistic hypothesisā, nevertheless faces problems. Questioning the coherence of the theoryās account of how the existence of objects of worship can avoid being fully conceptual-scheme dependent, and raising doubts about its pretensions to promote interreligious harmony, I also critically discuss the common philosophical tendency to work with under-described and insufficiently analysed examples. What philosophy ought to be able to offer in relation to religious diversity, I propose, is attentiveness to nuances and particularities, thereby aiding religious understanding without the need for a general theory
SN 2022joj: A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation
We present observations of SN 2022joj, a peculiar Type Ia supernova discovered by the Zwicky Transient Facility. SN 2022joj exhibits an unusually red g ZTF ā r ZTF color at early times and a rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity ( M g ZTF , max ā ā 19.7 mag), a blue broadband color (g ZTF ā r ZTF ā ā0.2 mag), and shallow Si ii absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 Ć
, which resembles the Ti ii features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity (u ā v ā 0.6 mag and uvw1 ā v ā 2.5 mag), suggesting a suppression of flux at ā¼2500-4000 Ć
. Strong C ii lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass (M ā 1 M ā) carbon/oxygen white dwarf from a relatively massive helium shell (M s ā 0.04-0.1 M ā), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of [Ni ii] Ī»7378 to [Fe ii] Ī»7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the [Fe ii] Ī»7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models
Deliver us from Evil: The Effects of Mortality Salience and Reminders of 9/11 on Support for President George W. Bush
According to terror management theory, heightened concerns about mortality should intensify the appeal of charismatic leaders. To assess this idea, we investigated how thoughts about death and the 9/11 terrorist attacks influence Americansā attitudes toward current U.S. President George W. Bush. Study 1 found that reminding people of their own mortality (mortality salience) increased support for Bush and his counterterrorism policies. Study 2 demonstrated that subliminal exposure to 9/11-related stimuli brought death-related thoughts closer to consciousness. Study 3 showed that reminders of both mortality and 9/11 increased support for Bush. In Study 4, mortality salience led participants to become more favorable toward Bush and voting for him in the upcoming election but less favorable toward Presidential candidate John Kerry and voting for him. Discussion focused on the role of terror management processes in allegiance to charismatic leaders and political decision making.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Time-series and Phase-curve Photometry of the Episodically Active Asteroid (6478) Gault in a Quiescent State Using APO, GROWTH, P200, and ZTF
We observed the episodically active asteroid (6478) Gault in 2020 with multiple telescopes in Asia and North America and found that it is no longer active after its recent outbursts at the end of 2018 and the start of 2019. The inactivity during this apparition allowed us to measure the absolute magnitude of Gault of Hr = 14.63 Ā± 0.02, Gr = 0.21 Ā± 0.02 from our secular phase-curve observations. In addition, we were able to constrain Gault's rotation period using time-series photometric lightcurves taken over 17 hr on multiple days in 2020 August, September, and October. The photometric lightcurves have a repeating ā²0.05 mag feature suggesting that (6478) Gault has a rotation period of ā¼2.5 hr and may have a semispherical or top-like shape, much like the near-Earth asteroids Ryugu and Bennu. The rotation period of ā¼2.5 hr is near the expected critical rotation period for an asteroid with the physical properties of (6478) Gault, suggesting that its activity observed over multiple epochs is due to surface mass shedding from its fast rotation spin-up by the YarkovskyāO'KeefeāRadzievskiiāPaddack effect
Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy
We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ā¼100 Ī¼m-scale dust ejected at ā¼1 m sā1 speeds with a ā¼1ā² jet pointing in the southwest direction. LD2 experienced a total dust mass loss of ā¼108 kg at a loss rate of ā¼6 kg sā1 with AfĻ/cross section varying between ā¼85 cm/125 km2 and ā¼200 cm/310 km2 from 2019 April 9 to 2019 November 8. If the increase in AfĻ/cross section remained constant, it implies LD2's activity began ā¼2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of ā²1027 mol sā1/ā²1026 mol sā1 from our 4.5 Ī¼m Spitzer observations; gār = 0.59 Ā± 0.03, rāi = 0.18 Ā± 0.05, and iāz = 0.01 Ā± 0.07 from GROWTH observations; and H2O gas production of ā²80 kg sā1 scaling from our estimated C2 production of mol sā1 from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within ā¼0.5 Hill radius in the last ā¼3 y and within 0.8 Hill radius in ā¼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 Ć 106 yr, having a dynamical half-life of 3.4 Ć 105 yr
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