49 research outputs found
Palomar discovery and initial characterization of naked-eye long period comet C/2022 E3 (ZTF)
Long-period comets are planetesimal remnants constraining the environment and
volatiles of the protoplanetary disc. We report the discovery of hyperbolic
long-period comet C/2022 E3 (ZTF), which has a perihelion 1.11 au, an
eccentricity 1 and an inclination 109, from images
taken with the Palomar 48-inch telescope during morning twilight on 2022 Mar 2.
Additionally, we report the characterization of C/2022 E3 (ZTF) from
observations taken with the Palomar 200-inch, the Palomar 60-inch, and the NASA
Infrared Telescope Facility in early 2023 February to 2023 March when the comet
passed within 0.28 au of the Earth and reached a visible magnitude of
5. We measure g-r = 0.700.01, r-i = 0.200.01, i-z =
0.060.01, z-J = 0.900.01, J-H = 0.380.01 and H-K = 0.150.01
colours for the comet from observations. We measure the A(0)f
(0.8~m) in a 6500~km radius from the nucleus of 148340~cm, and CN,
C, and C production of 5.4310~mol/s,
2.0110, and 3.0810~mol/s, similar to
other long period comets. We additionally observe the appearance of jet-like
structures at a scale of 4,000 km in wide-field g-band images, which may
be caused by the presence of CN gas in the near-nucleus coma.Comment: Accepted for publication in MNRAS:L, 9 pages, 6 figures, 2 table
SN 2020udy: a SN Iax with strict limits on interaction consistent with a helium-star companion
Early observations of transient explosions can provide vital clues to their
progenitor origins. In this paper we present the nearby Type Iax (02cx-like)
supernova (SN), SN 2020udy that was discovered within hours (7 hr) of
estimated first light. An extensive dataset of ultra-violet, optical, and
near-infrared observations was obtained, covering out to 150 d after
explosion. SN 2020udy peaked at -17.860.43 mag in the r band and evolved
similarly to other 'luminous' SNe Iax, such as SNe 2005hk and 2012Z. Its
well-sampled early light curve allows strict limits on companion interaction to
be placed. Main-sequence companion stars with masses of 2 and 6 M are
ruled out at all viewing angles, while a helium-star companion is allowed from
a narrow range of angles (140-180 away from the companion). The spectra
and light curves of SN2020udy are in good agreement with those of the 'N5def'
deflagration model of a near Chandrasekhar-mass carbon-oxygen white dwarf.
However, as has been seen in previous studies of similar luminosity events, SN
2020udy evolves slower than the model. Broad-band linear polarisation
measurements taken at and after peak are consistent with no polarisation, in
agreement with the predictions of the companion-star configuration from the
early light curve measurements. The host galaxy environment is low metallicity
and is consistent with a young stellar population. Overall, we find the most
plausible explosion scenario to be the incomplete disruption of a CO white
dwarf near the Chandrasekhar-mass limit, with a helium-star companion.Comment: 18 pages, 14 figures, submitted to MNRA
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 AV₂, possessing an aphelion distance of 0.65 au and ∼2 km in size. While it is possible that 2020 AV₂ 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 AV₂ 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 AV₂, possessing an aphelion distance of 0.65 au and ∼2 km in size. While it is possible that 2020 AV₂ 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 AV₂ may come from a yet undiscovered source population of asteroids interior to Venus, and currently favored asteroid population models may need to be adjusted
Dramatic rebrightening of the type-changing stripped-envelope supernova SN 2023aew
Multi-peaked supernovae with precursors, dramatic light-curve rebrightenings,
and spectral transformation are rare, but are being discovered in increasing
numbers by modern night-sky transient surveys like the Zwicky Transient
Facility (ZTF). Here, we present the observations and analysis of SN 2023aew,
which showed a dramatic increase in brightness following an initial luminous
(-17.4 mag) and long (~100 days) unusual first peak (possibly precursor). SN
2023aew was classified as a Type IIb supernova during the first peak but
changed its type to resemble a stripped-envelope supernova (SESN) after the
marked rebrightening. We present comparisons of SN 2023aew's spectral evolution
with SESN subtypes and argue that it is similar to SNe Ibc during its main
peak. P-Cygni Balmer lines are present during the first peak, but vanish during
the second peak's photospheric phase, before H resurfaces again during
the nebular phase. The nebular lines ([O I], [Ca II], Mg I], H) exhibit
a double-peaked structure which hints towards a clumpy or non-spherical ejecta.
We analyze the second peak in the light curve of SN 2023aew and find it to be
broader than normal SESNe as well as requiring a very high Ni mass to
power the peak luminosity. We discuss the possible origins of SN 2023aew
including an eruption scenario where a part of the envelope is ejected during
the first peak which also powers the second peak of the light curve through
SN-CSM interaction.Comment: 22 pages, 11 figures, 5 table
Initial Visible and Mid-IR Characterization of P/2019 LD₂ (ATLAS), an Active Transitioning Centaur Among the Trojans, with Hubble, Spitzer, ZTF, Keck, APO and GROWTH Imaging and Spectroscopy
We present visible and mid-infrared imagery and photometry of Jovian co-orbital comet P/2019 LD₂ (ATLAS) taken with Hubble Space Telescope/WFC3 on 2020 April 1, Spitzer Space Telescope/IRAC on 2020 January 25, Zwicky Transient Facility between 2019 April 9 and 2019 Nov 8 and the GROWTH telescope network from 2020 May to July, as well as visible spectroscopy from Keck/LRIS on 2020 August 19. Our observations indicate that LD₂ has a nucleus with radius 0.2-1.8 km assuming a 0.08 albedo and that the coma is dominated by ∼100 μ m-scale dust ejected at ∼1 m/s speeds with a ∼1" jet pointing in the SW direction. LD₂ experienced a total dust mass loss of ∼10⁸ kg and dust mass loss rate of ∼6 kg/s with Afρ/cross-section varying between ∼85 cm/125 km² and ∼200 cm/310 km² between 2019 April 9 and 2019 Nov 8. If the Afρ/cross-section increase remained constant, it implies that LD₂ has remained active since ∼2018 November when it came within 4.8 au of the Sun, a typical distance for comets to begin sublimation of H₂O. From our 4.5 μm Spitzer observations, we set a limit on CO/CO₂ gas production of ∼10²⁷/∼10²⁶ mol/s. Multiple bandpass photometry of LD₂ taken by the GROWTH network measured in a 10,000 km aperture provide color measurements of g-r = 0.59±0.03, r-i = 0.18±0.05, and i-z = 0.01±0.07, colors typical of comets. We set a spectroscopic upper limit to the production of H₂O gas of ∼80 kg/s. Improving the orbital solution for LD₂ with our observations, we determine that the long-term orbit of LD₂ is that of a typical Jupiter Family Comet having close encounters with Jupiter coming within ∼0.5 Hill radius in the last ∼3 y to within 0.8 Hill radius in ∼9 y and has a 95% chance of being ejected from the Solar System in < 10 Myr