Search

Start Over Subject optical astronomy
3041. RAVE J183013.5-455510 equivalent-width measurements
ID:
ivo://CDS.VizieR/J/ApJ/897/78
Title:
RAVE J183013.5-455510 equivalent-width measurements
Short Name:
J/ApJ/897/78
Date:
15 Mar 2022 04:12:46
Publisher:
CDS
Description:
We report on the spectroscopic analysis of RAVE-J183013.5-455510, an extremely metal-poor star, highly enhanced in CNO, and with discernible contributions from the rapid neutron-capture process. There is no evidence of binarity for this object. At [Fe/H]=-3.57, this star has one of the lowest metallicities currently observed, with 18 measured abundances of neutron-capture elements. The presence of Ba, La, and Ce abundances above the solar system r-process predictions suggests that there must have been a non-standard source of r-process elements operating at such low metallicities. One plausible explanation is that this enhancement originates from material ejected at unusually high velocities in a neutron star merger event. We also explore the possibility that the neutron-capture elements were produced during the evolution and explosion of a rotating massive star. In addition, based on comparisons with yields from zero-metallicity faint supernova, we speculate that RAVE-J1830-4555 was formed from a gas cloud pre-enriched by both progenitor types. From analysis based on Gaia DR2 measurements, we show that this star has orbital properties similar to the Galactic metal-weak thick-disk stellar population.
3042. R-band and polarimetry of the blazar S5 0716+71
ID:
ivo://CDS.VizieR/J/ApJ/768/40
Title:
R-band and polarimetry of the blazar S5 0716+71
Short Name:
J/ApJ/768/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5 0716+714 along with Fermi {gamma}-ray data during a multi-waveband outburst in 2011 October. We analyze total and polarized intensity images of the blazar obtained with the VLBA at 43GHz during and after the outburst. Monotonic rotation of the linear polarization vector at a rate of >~50{deg} per night coincided with a sharp maximum in {gamma}-ray and optical flux. At the same time, within the uncertainties, a new superluminal knot appeared with an apparent speed of 21+/-2c. The general multi-frequency behavior of the outburst can be explained within the framework of a shock wave propagating along a helical path in the blazar's jet.
3043. R-band K2 photometry of main-belt asteroids
ID:
ivo://CDS.VizieR/J/ApJS/234/37
Title:
R-band K2 photometry of main-belt asteroids
Short Name:
J/ApJS/234/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the K2 light curves of a large sample of untargeted main-belt asteroids (MBAs) detected with the Kepler Space Telescope. The asteroids were observed within the Uranus superstamp, a relatively large, continuous field with a low stellar background designed to cover the planet Uranus and its moons during Campaign 8 of the K2 mission. The superstamp offered the possibility of obtaining precise, uninterrupted light curves of a large number of MBAs and thus determining unambiguous rotation rates for them. We obtained photometry for 608 MBAs, and were able to determine or estimate rotation rates for 90 targets, of which 86 had no known values before. In an additional 16 targets we detected incomplete cycles and/or eclipse-like events. We found the median rotation rate to be significantly longer than that of the ground-based observations, indicating that the latter are biased toward shorter rotation rates. Our study highlights the need and benefits of further continuous photometry of asteroids.
3044. R-band light curve of Qatar-1
ID:
ivo://CDS.VizieR/J/AJ/161/108
Title:
R-band light curve of Qatar-1
Short Name:
J/AJ/161/108
Date:
21 Oct 2021
Publisher:
CDS
Description:
Motivated by the unsettled conclusion on whether there are any transit timing variations (TTVs) for the exoplanet Qatar-1b, 10 new transit light curves are presented and a TTV analysis with a baseline of 1400 epochs is performed. Because the linear model provides a good fit with a reduced chi-square of {chi}_red_^2^=2.59 and the false-alarm probabilities of the possible TTV frequencies are as large as 35%, our results are consistent with a null-TTV model. Nevertheless, a new ephemeris with a reference time of T0=2455647.63360{+/-}0.00008 (BJD) and a period of P=1.4200236{+/-}0.0000001day is obtained. In addition, the updated orbital semimajor axis and planetary radius in units of stellar radius are provided, and the lower limit of the modified stellar tidal quality factor is also determined.
3045. R-band light curve of QSO J0158-4325 images
ID:
ivo://CDS.VizieR/J/ApJ/756/52
Title:
R-band light curve of QSO J0158-4325 images
Short Name:
J/ApJ/756/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present four new seasons of optical monitoring data and six epochs of X-ray photometry for the doubly imaged lensed quasar Q J0158-4325. The high-amplitude, short-period microlensing variability for which this system is known has historically precluded a time delay measurement by conventional methods. We attempt to circumvent this limitation by the application of a Monte Carlo microlensing analysis technique, but we are only able to prove that the delay must have the expected sign (image A leads image B). Despite our failure to robustly measure the time delay, we successfully model the microlensing at optical and X-ray wavelengths to find a half-light radius for soft X-ray emission log (r_1/2,X,soft_/cm)=14.3^+0.4^_-0.5_, an upper limit on the half-light radius for hard X-ray emission log (r_1/2,X,hard_/cm)<=14.6, and a refined estimate of the inclination-corrected scale radius of the optical R-band (rest frame 3100{AA}) continuum emission region of log (r_s_/cm)=15.6+/-0.3.
3046. R-band light curves of type II supernovae
ID:
ivo://CDS.VizieR/J/ApJ/820/33
Title:
R-band light curves of type II supernovae
Short Name:
J/ApJ/820/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of 57 R-band SN II light curves that are well-monitored during their rise, with >5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 1-3 days. We show that the energy per unit mass (E/M) can be deduced to roughly a factor of five by comparing early-time optical data to the 2011 model of Rabinak & Waxman, while the progenitor radius cannot be determined based on R-band data alone. We find that SN II explosion energies span a range of E/M=(0.2-20)x10^51^erg/(10M_{sun}), and have a mean energy per unit mass of <E/M>=0.85x10^51^erg/(10M_{sun}), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, E/M is positively correlated with the amount of ^56^Ni produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate ({Delta}m_15_), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.
3047. R-band linear polarization of Gaia stars
ID:
ivo://CDS.VizieR/J/ApJ/872/56
Title:
R-band linear polarization of Gaia stars
Short Name:
J/ApJ/872/56
Date:
21 Oct 2021
Publisher:
CDS
Description:
The availability of large data sets with stellar distance and polarization information will enable a tomographic reconstruction of the (plane-of-the-sky-projected) interstellar magnetic field in the near future. We demonstrate the feasibility of such a decomposition within a small region of the diffuse interstellar medium (ISM). We combine measurements of starlight (R-band) linear polarization obtained using the RoboPol polarimeter with stellar distances from the second Gaia data release. The stellar sample is brighter than 17mag in the R-band and reaches out to several kiloparsecs from the Sun. HI emission spectra reveal the existence of two distinct clouds along the line of sight. We decompose the line-of-sight-integrated stellar polarizations to obtain the mean polarization properties of the two clouds. The two clouds exhibit significant differences in terms of column density and polarization properties. Their mean plane-of-the-sky magnetic field orientation differs by 60{deg}. We show how our tomographic decomposition can be used to constrain our estimates of the polarizing efficiency of the clouds as well as the frequency dependence of the polarization angle of polarized dust emission. We also demonstrate a new method to constrain cloud distances based on this decomposition. Our results represent a preview of the wealth of information that can be obtained from a tomographic map of the ISM magnetic field.
3048. R-band observations of PTF 10vgv
ID:
ivo://CDS.VizieR/J/ApJ/747/L5
Title:
R-band observations of PTF 10vgv
Short Name:
J/ApJ/747/L5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of PTF 10vgv, a Type Ic supernova (SN) detected by the Palomar Transient Factory, using the Palomar 48 inch telescope (P48). R-band observations of the PTF 10vgv field with P48 probe the SN emission from its very early phases (about two weeks before R-band maximum) and set limits on its flux in the week prior to the discovery. Our sensitive upper limits and early detections constrain the post-shock-breakout luminosity of this event. Via comparison to numerical (analytical) models, we derive an upper-limit of R<~4.5R_{sun}_ (R<~1R_{sun}_) on the radius of the progenitor star, a direct indication in favor of a compact Wolf-Rayet star. Applying a similar analysis to the historical observations of SN 1994I yields R<~1/4R_{sun}_ for the progenitor radius of this SN.
3049. r'-band photometry of comet 96P/Machholz 1
ID:
ivo://CDS.VizieR/J/AJ/157/186
Title:
r'-band photometry of comet 96P/Machholz 1
Short Name:
J/AJ/157/186
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed comet 96P/Machholz 1 on a total of nine nights before and after perihelion during its 2017/2018 apparition. Both its unusually small perihelion distance and the observed fragmentation during multiple apparitions make 96P an object of great interest. Our observations show no evidence of a detectable dust coma, implying that we are observing a bare nucleus at distances ranging from 2.3 to 3.8 au. Based on this assumption, we calculated its color and found average values of g'-r'=0.50+/-0.04, r'-i'=0.17+/-0.03, and i'-z'=0.06+/-0.04. These are notably more blue than those of the nuclei of other Jupiter-family and long-period comets. Furthermore, assuming a bare nucleus, we found an equivalent nuclear radius of 3.4+/-0.2 km with an axial ratio of at least 1.6+/-0.1. The lightcurve clearly displays one large peak, one broad flat peak, and two distinct troughs, with a clear asymmetry that suggests that the shape of the nucleus deviates from that of a simple triaxial ellipsoid. This asymmetry in the lightcurve allowed us to constrain the nuclear rotation period to 4.10+/-0.03 hr and 4.096+/-0.002 hr before and after perihelion, respectively. Within the uncertainties, 96P's rotation period does not appear to have changed throughout the apparition, and we conclude a maximum possible change in rotation period of 130 s. The observed properties were compared to those of comet 322P and interstellar object 1I/'Oumuamua in an attempt to study the effects of close perihelion passages on cometary surfaces and their internal structure and the potential interstellar origin of 96P.
3050. R-band PTF observations of SNe IIb
ID:
ivo://CDS.VizieR/J/ApJ/811/117
Title:
R-band PTF observations of SNe IIb
Short Name:
J/ApJ/811/117
Date:
21 Oct 2021
Publisher:
CDS
Description:
The progenitor stars of several Type IIb supernovae (SNe) show indications of extended hydrogen envelopes. These envelopes might be the outcome of luminous energetic pre-explosion events, so-called precursor eruptions. We use the Palomar Transient Factory (PTF) pre-explosion observations of a sample of 27 nearby SNe IIb to look for such precursors during the final years prior to the SN explosion. No precursors are found when combining the observations in 15-day bins, and we calculate the absolute-magnitude-dependent upper limit on the precursor rate. At the 90% confidence level, SNe IIb have on average <0.86 precursors as bright as an absolute R-band magnitude of -14 in the final 3.5 years before the explosion and <0.56 events over the final year. In contrast, precursors among SNe IIn have a >~5 times higher rate. The kinetic energy required to unbind a low-mass stellar envelope is comparable to the radiated energy of a few-weeks-long precursor that would be detectable for the closest SNe in our sample. Therefore, mass ejections, if they are common in such SNe, are radiatively inefficient or have durations longer than months. Indeed, when using 60-day bins, a faint precursor candidate is detected prior to SN 2012cs (~2% false-alarm probability). We also report the detection of the progenitor of SN 2011dh that does not show detectable variability over the final two years before the explosion. The suggested progenitor of SN 2012P is still present, and hence is likely a compact star cluster or an unrelated object.