Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTwo Distant Halo Velocity Groups Discovered by the Palomar Transient Factory
141
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report the discovery of two new halo velocity groups (Cancer groups A and B) traced by 8 distant RR Lyrae stars and observed by the Palomar Transient Factory (PTF) survey at R.A.~129 deg, Dec~20 deg (l~205 deg, b~32 deg). Located at 92 kpc from the Galactic center (86 kpc from the Sun), these are some of the most distant substructures in the Galactic halo known to date. Follow-up spectroscopic observations with the Palomar Observatory 5.1-m Hale telescope and W. M. Keck Observatory 10-m Keck I telescope indicate that the two groups are moving away from the Galaxy at v_{gsr} = 78.0+-5.6 km/s (Cancer group A) and v_{gsr} = 16.3+-7.1 km/s (Cancer group B). The groups have velocity dispersions of sigma_{v_{gsr}}=12.4+-5.0 km/s and sigma_{v_{gsr}}=14.9+-6.2 km/s, and are spatially extended (about several kpc) making it very unlikely that they are bound systems, and are more likely to be debris of tidally disrupted dwarf galaxies or globular clusters. Both groups are metal-poor (median metallicities of [Fe/H] = -1.6 dex and [Fe/H] =-2.1 dex), and have a somewhat uncertain (due to small sample size) metallicity dispersion of ~0.4 dex, suggesting dwarf galaxies as progenitors. Two additional RR Lyrae stars with velocities consistent with those of the Cancer groups have been observed ~25 deg east, suggesting possible extension of the groups in that direction.
rate research
Read More
The Palomar Transient Factory proves to be a prolific source of Magnetic Cataclysmic Variables, selected by their distinctive photometric variability, and followed up spectroscopically. Here, we present six new candidate systems, together with preliminary photometric periods and spectra.
We present the discovery and follow-up observations of a broad-line type-Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient Factory (PTF) on 2010 February 23. The SN distance is cong 218 Mpc, greater than GRB 980425 / SN 1998bw and GRB 060218 / SN 2006aj, but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with Palomar-48 inch, Palomar 60-inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, CARMA, WSRT, and EVLA. Here we compare the properties of PTF 10bzf with those of SN 1998bw and other broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf suggest that this SN is intermediate, in kinetic energy and amount of 56Ni, between non GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe like 1998bw. No X-ray or radio counterpart to PTF 10bzf was detected. X-ray upper-limits allow us to exclude the presence of an underlying X-ray afterglow as luminous as that of other SN-associated GRBs like GRB 030329 or GRB 031203. Early-time radio upper-limits do not show evidence for mildly-relativistic ejecta. Late-time radio upper-limits rule out the presence of an underlying off-axis GRB, with energy and wind density similar to the SN-associated GRB 030329 and GRB 031203. Finally, by performing a search for a GRB in the time window and at the position of PTF 10bzf, we find that no GRB in the IPN catalog could be associated with this SN.
We present results of the Sky2Night project: a systematic, unbiased search for fast optical transients with the Palomar Transient Factory. We have observed 407 deg$^2$ in $R$-band for 8 nights at a cadence of 2 hours. During the entire duration of the project, the 4.2m William Herschel Telescope on La Palma was dedicated to obtaining identification spectra for the detected transients. During the search, we found 12 supernovae, 10 outbursting cataclysmic variables, 9 flaring M-stars, 3 flaring active Galactic nuclei and no extragalactic fast optical transients. Using this systematic survey for transients, we have calculated robust observed rates for the detected types of transients, and upper limits of the rate of extragalactic fast optical transients of $mathcal{R}<37times 10^{-4}$deg$^{-2}$d$^{-1}$ and $mathcal{R}<9.3times 10^{-4}$deg$^{-2}$d$^{-1}$ for timescales of 4h and 1d and a limiting magnitude of $Rapprox19.7$. We use the results of this project to determine what kind of and how many astrophysical false positives we can expect when following up gravitational wave detections in search for kilonovae.
We construct a photometrically calibrated catalog of non-variable sources from the Palomar Transient Factory (PTF) observations. The first version of this catalog presented here, the PTF photometric catalog 1.0, contains calibrated R_PTF-filter magnitudes for about 21 million sources brighter than magnitude 19, over an area of about 11233 deg^2. The magnitudes are provided in the PTF photometric system, and the color of a source is required in order to convert these magnitudes into other magnitude systems. We estimate that the magnitudes in this catalog have typical accuracy of about 0.02 mag with respect to magnitudes from the Sloan Digital Sky Survey. The median repeatability of our catalogs magnitudes for stars between 15 and 16 mag, is about 0.01 mag, and it is better than 0.03 mag for 95% of the sources in this magnitude range. The main goal of this catalog is to provide reference magnitudes for photometric calibration of visible light observations. Subseque
The Palomar Transient Factory (PTF) is a synoptic survey designed to explore the transient and variable sky in a wide variety of cadences. We use PTF observations of fields that were observed multiple times (>=10) per night, for several nights, to find asteroids, construct their lightcurves and measure their rotation periods. Here we describe the pipeline we use to achieve these goals and present the results from the first four (overlapping) PTF fields analyzed as part of this program. These fields, which cover an area of 21 deg^2, were observed on four nights with a cadence of ~20 min. Our pipeline was able to detect 624 asteroids, of which 145 (~20%) were previously unknown. We present high quality rotation periods for 88 main-belt asteroids and possible period or lower limit on the period for an additional 85 asteroids. For the remaining 451 asteroids, we present lower limits on their photometric amplitudes. Three of the asteroids have lightcurves that are characteristic of binary asteroids. We estimate that implementing our search for all existing high-cadence PTF data will provide rotation periods for about 10,000 asteroids mainly in the magnitude range ~14 to ~20.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
