-
S. Bradley Cenko, S. R. Kulkarni,
Assaf Horesh,
Alessandra Corsi,
Derek B. Fox,
John Carpenter,
Dale A. Frail,
Peter E. Nugent,
Daniel A. Perley,
D. Gruber, [......],
Mansi M. Kasliwal,
Nicholas M. Law,
Adam N. Morgan,
David Polishook,
Dovi Poznanski,
Robert M. Quimby,
Branimir Sesar,
Ken J. Shen,
Jeffrey M. Silverman,
Assaf Sternberg
[show abstract]
[hide abstract]
ABSTRACT: We report the discovery by the Palomar Transient Factory (PTF) of the
transient source PTF11agg, which is distinguished by three primary
characteristics: (1) bright, rapidly fading optical transient emission; (2) a
faint, blue quiescent optical counterpart; and (3) an associated year-long,
scintillating radio transient. We argue that these observed properties are
inconsistent with any known class of Galactic transients, and instead suggest a
cosmological origin. The detection of incoherent radio emission at such
distances implies a large emitting region, from which we infer the presence of
relativistic ejecta. The observed properties are all consistent with the
population of long-duration gamma-ray bursts (GRBs), marking the first time
such an outburst has been discovered in the distant universe independent of a
high-energy trigger. We searched for possible high-energy counterparts to
PTF11agg, but found no evidence for associated prompt emission. We therefore
consider three possible scenarios to account for a GRB-like afterglow without a
high-energy counterpart: an "untriggered" GRB (lack of satellite coverage), an
"orphan" afterglow (viewing-angle effects), and a "dirty fireball" (suppressed
high-energy emission). The observed optical and radio light curves appear
inconsistent with even the most basic predictions for off-axis afterglow
models. The simplest explanation, then, is that PTF11agg is a normal, on-axis
long-duration GRB for which the associated high-energy emission was simply
missed. However, we have calculated the likelihood of such a serendipitous
discovery by PTF and find that it is quite small (~ 2.6%). While not
definitive, we nonetheless speculate that PTF11agg may represent a new, more
common (> 4 times the on-axis GRB rate at 90% confidence) class of relativistic
outbursts lacking associated high-energy emission.
04/2013;
-
M. M. Kasliwal, S. R. Kulkarni,
R. Quimby,
P. E. Nugent,
D. A. Howell,
J. Cooke,
S. B. Cenko,
A. Gal-Yam,
N. Law,
D. Levitan,
E. O. Ofek,
D. Poznanski
Central Bureau Electronic Telegrams. 02/2013; 1819:1.
-
E O Ofek,
M Sullivan,
S B Cenko,
M M Kasliwal,
A Gal-Yam, S R Kulkarni,
I Arcavi,
L Bildsten,
J S Bloom,
A Horesh,
D A Howell,
A V Filippenko,
R Laher,
D Murray,
E Nakar,
P E Nugent,
J M Silverman,
N J Shaviv,
J Surace,
O Yaron
[show abstract]
[hide abstract]
ABSTRACT: Some observations suggest that very massive stars experience extreme mass-loss episodes shortly before they explode as supernovae, as do several models. Establishing a causal connection between these mass-loss episodes and the final explosion would provide a novel way to study pre-supernova massive-star evolution. Here we report observations of a mass-loss event detected 40 days before the explosion of the type IIn supernova SN 2010mc (also known as PTF 10tel). Our photometric and spectroscopic data suggest that this event is a result of an energetic outburst, radiating at least 6 × 10(47) erg of energy and releasing about 10(-2) solar masses of material at typical velocities of 2,000 km s(-1). The temporal proximity of the mass-loss outburst and the supernova explosion implies a causal connection between them. Moreover, we find that the outburst luminosity and velocity are consistent with the predictions of the wave-driven pulsation model, and disfavour alternative suggestions.
Nature 02/2013; 494(7435):65-7. · 36.28 Impact Factor
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Emil Terziev,
Nicholas M. Law,
Iair Arcavi,
Christoph Baranec,
Joshua S. Bloom,
Khanh Bui,
Mahesh P. Burse,
Pravin Chorida,
H. K. Das,
Richard G. Dekany,
Adam L. Kraus, S. R. Kulkarni,
Peter Nugent,
Eran O. Ofek,
Sujit Punnadi,
A. N. Ramaprakash,
Reed Riddle,
Shriharsh P. Tendulkar
[show abstract]
[hide abstract]
ABSTRACT: The direct detection of binary systems in wide-field surveys is limited by
the size of the stars' point-spread-functions (PSFs). A search for elongated
objects can find closer companions, but is limited by the precision to which
the PSF shape can be calibrated for individual stars. We have developed the
BinaryFinder algorithm to search for close binaries by using precision
measurements of PSF ellipticity across wide-field survey images. We show that
the algorithm is capable of reliably detecting binary systems down to
approximately 1/5 of the seeing limit, and can directly measure the systems'
position angles, separations and contrast ratios. To verify the algorithm's
performance we evaluated 100,000 objects in Palomar Transient Factory (PTF)
wide-field-survey data for signs of binarity, and then used the Robo-AO robotic
laser adaptive optics system to verify the parameters of 44 high-confidence
targets. We show that BinaryFinder correctly predicts the presence of close
companions with a <5% false-positive rate, measures the detected binaries'
position angles within 2 degrees and separations within 25%, and weakly
constrains their contrast ratios. When applied to the full PTF dataset, we
estimate that BinaryFinder will discover and characterize ~450,000
physically-associated binary systems with separations <2 arcseconds and
magnitudes brighter than R=18. New wide-field synoptic surveys with high
sensitivity and sub-arcsecond angular resolution, such as LSST, will allow
BinaryFinder to reliably detect millions of very faint binary systems with
separations as small as 0.1 arcseconds.
10/2012;
-
Assaf Horesh,
Christopher Stockdale,
Derek B. Fox,
Dale A. Frail,
John Carpenter, S. R. Kulkarni,
Eran O. Ofek,
Avishay Gal-Yam,
Mansi M. Kasliwal,
Iair Arcavi, [......],
David Polishook,
Ofer Yaron,
Stuart Ryder,
Kurt W. Weiler,
Franz Bauer,
Schuyler D. Van Dyk,
Stefan Immler,
Nino Panagia,
Dave Pooley,
Namir Kassim
[show abstract]
[hide abstract]
ABSTRACT: Only a handful of supernovae (SNe) have been studied in multi-wavelength from
radio to X-rays, starting a few days after explosion. The early detection and
classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a
unique opportunity to conduct such observations. We present detailed data
obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12
after explosion) in the radio, millimeter and X-rays; when combined with
optical data, this allows us to explore the early evolution of the SN blast
wave and its surroundings. Our analysis shows that the expanding supernova
shockwave does not exhibit equipartition (e_e/e_B ~ 1000), and is expanding
into circumstellar material that is consistent with a density profile falling
like R^-2. Within modeling uncertainties we find an average velocity of the
fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous
analysis. This velocity places SN 2011dh in an intermediate blast-wave regime
between the previously defined compact and extended SN IIb subtypes. Our
results highlight the importance of early (~ 1 day) high-frequency observations
of future events. Moreover, we show the importance of combined radio/X-ray
observations for determining the microphysics ratio e_e/e_B.
09/2012;
-
B Dilday,
D A Howell,
S B Cenko,
J M Silverman,
P E Nugent,
M Sullivan,
S Ben-Ami,
L Bildsten,
M Bolte,
M Endl, [......],
D R Tytler,
D Xu,
J S Bloom,
A Gal-Yam,
I M Hook, S R Kulkarni,
N M Law,
E O Ofek,
D Polishook,
D Poznanski
[show abstract]
[hide abstract]
ABSTRACT: There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.
Science 08/2012; 337(6097):942-5. · 31.20 Impact Factor
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S. Hachinger,
P. A. Mazzali,
M. Sullivan,
R. Ellis,
K. Maguire,
A. Gal-Yam,
D. A. Howell,
P. E. Nugent,
E. Baron,
J. Cooke, [......],
B. Dilday,
P. A. James,
M. M. Kasliwal, S. R. Kulkarni,
E. O. Ofek,
R. R. Laher,
J. Parrent,
J. Surace,
O. Yaron,
E. S. Walker
[show abstract]
[hide abstract]
ABSTRACT: Radiative transfer studies of Type Ia supernovae (SNe Ia) hold the promise of
constraining both the time-dependent density profile of the SN ejecta and its
stratification by element abundance which, in turn, may discriminate between
different explosion mechanisms and progenitor classes. Here we present a
detailed analysis of Hubble Space Telescope ultraviolet (UV) and ground-based
optical spectra and light curves of the SN Ia SN 2010jn (PTF10ygu). SN 2010jn
was discovered by the Palomar Transient Factory (PTF) 15 days before maximum
light, allowing us to secure a time-series of four UV spectra at epochs from
-11 to +5 days relative to B-band maximum. The photospheric UV spectra are
excellent diagnostics of the iron-group abundances in the outer layers of the
ejecta, particularly those at very early times. Using the method of 'Abundance
Tomography' we have derived iron-group abundances in SN 2010jn with a precision
better than in any previously studied SN Ia. Optimum fits to the data can be
obtained if burned material is present even at high velocities, including
significant mass fractions of iron-group elements. This is consistent with the
slow decline rate (or high 'stretch') of the light curve of SN 2010jn, and
consistent with the results of delayed-detonation models. Early-phase UV
spectra and detailed time-dependent series of further SNe Ia offer a promising
probe of the nature of the SN Ia mechanism.
08/2012;
-
B. Dilday,
D. A. Howell,
S. B. Cenko,
J. M. Silverman,
P. E. Nugent,
M. Sullivan,
S. Ben-Ami,
L. Bildsten,
M. Bolte,
M. Endl, [......],
D. R. Tytler,
D. Xu,
J. S. Bloom,
A. Gal-Yam,
I. M. Hook, S. R. Kulkarni,
N. M. Law,
E. O. Ofek,
D. Polishook,
D. Poznanski
[show abstract]
[hide abstract]
ABSTRACT: There is a consensus that Type-Ia supernovae (SNe Ia) arise from the
thermonuclear explosion of white dwarf stars that accrete matter from a binary
companion. However, direct observation of SN Ia progenitors is lacking, and the
precise nature of the binary companion remains uncertain. A temporal series of
high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex
circumstellar environment that provides an unprecedentedly detailed view of the
progenitor system. Multiple shells of circumsteller are detected and the SN
ejecta are seen to interact with circumstellar material (CSM) starting 59 days
after the explosion. These features are best described by a symbiotic nova
progenitor, similar to RS Ophiuchi.
07/2012;
-
R ~R Laher,
L ~M Rebull,
V Gorjian,
F ~J Masci,
J ~W Fowler,
C Grillmair,
J Surace,
S Mattingly,
E Jackson,
E Hacopeans, [......],
R ~M Quimby,
E ~O Ofek,
M ~M Kasliwal,
J Zolkower,
V Velur,
R Walters,
J Henning,
K Bui,
D McKenna, S ~R Kulkarni
pasp. 07/2012; 124:764-781.
-
E. O. Ofek,
R. Laher,
J. Surace,
D. Levitan,
B. Sesar,
A. Horesh,
N. Law,
J. C. van Eyken, S. R. Kulkarni,
T. A. Prince, [......],
I. Arcavi,
L. Bildsten,
J. Bloom,
S. B. Cenko,
A. Gal-Yam,
C. Grillmair,
G. Helou,
M. M. Kasliwal,
D. Poznanski,
R. Quimby
[show abstract]
[hide abstract]
ABSTRACT: 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 catalog's 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. Subsequent versions of
this catalog, which will be published incrementally online, will be extended to
a larger sky area and will also include g_PTF-filter magnitudes, as well as
variability and proper motion information.
06/2012;
-
E. O. Ofek,
D. Fox,
S. B. Cenko,
M. Sullivan,
O. Gnat,
D. A. Frail,
A. Horesh,
A. Corsi,
R. M. Quimby,
N. Gehrels, [......],
A. V. Filippenko,
M. M. Kasliwal,
L. Bildsten,
J. S. Bloom,
D. Poznanski,
I. Arcavi,
R. R. Laher,
D. Levitan,
B. Sesar,
J. Surace
[show abstract]
[hide abstract]
ABSTRACT: (Abridged). The optical light curve of some SNe may be powered by the outward
diffusion of the energy deposited by the explosion shock in optically thick
circumstellar matter (CSM). Recently, it was shown that the radiation-mediated
and -dominated shock in an optically thick wind must transform into a
collisionless shock and can produce hard X-rays. The X-rays are expected to
peak at late times, relative to maximum visible light. Here we report on a
search, using Swift and Chandra, for X-ray emission from 28 SNe that belong to
classes whose progenitors are suspected to be embedded in dense CSM
(IIn/Ibn/SLSN-I). Two SNe in our sample have X-ray properties that are roughly
consistent with the expectation for X-rays from a collisionless shock in
optically thick CSM. Therefore, we suggest that their optical light curves are
powered by shock breakout in CSM. We show that two other events were too X-ray
bright during the SN maximum optical light to be explained by the shock
breakout model. We conclude that the light curves of some, but not all,
type-IIn/Ibn SNe are powered by shock breakout in CSM. For the rest of the SNe
in our sample, including all the SLSN-I events, our X-ray limits are not deep
enough and were typically obtained at too early times to conclude about their
nature. We argue that the optical light curves of SNe, for which the X-ray
emission peaks at late times, are likely powered by the diffusion of shock
energy from a dense CSM. We comment about the possibility to detect some of
these events in radio.
06/2012;
-
B. Sesar,
J. G. Cohen,
D. Levitan,
C. J. Grillmair,
M. Juric,
E. N. Kirby,
R. R. Laher,
E. O. Ofek,
J. A. Surace, S. R. Kulkarni,
T. A. Prince
[show abstract]
[hide abstract]
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.
06/2012;
-
J. T. Parrent,
D. A. Howell,
B. Friesen,
R. C. Thomas,
R. A. Fesen,
D. Milisavljevic,
F. B. Bianco,
B. Dilday,
P. Nugent,
E. Baron, [......],
D. Polishook,
D. Poznanski,
R. M. Quimby,
J. M. Silverman,
A. Sternberg,
M. Sullivan,
E. S. Walker,
D. Xu,
C. Buton,
R. Pereira
[show abstract]
[hide abstract]
ABSTRACT: The nearby Type Ia supernova SN 2011fe in M101 (cz=241 km s^-1) provides a
unique opportunity to study the early evolution of a "normal" Type Ia
supernova, its compositional structure, and its elusive progenitor system. We
present 18 high signal-to-noise spectra of SN 2011fe during its first month
beginning 1.2 days post-explosion and with an average cadence of 1.8 days. This
gives a clear picture of how various line-forming species are distributed
within the outer layers of the ejecta, including that of unburned material
(C+O). We follow the evolution of C II absorption features until they diminish
near maximum light, showing overlapping regions of burned and unburned material
between ejection velocities of 10,000 and 16,000 km s^-1. This supports the
notion that incomplete burning, in addition to progenitor scenarios, is a
relevant source of spectroscopic diversity among SNe Ia. The observed evolution
of the highly Doppler-shifted O I 7774 absorption features detected within five
days post-explosion indicate the presence of O I with expansion velocities from
11,500 to 21,000 km s^-1. The fact that some O I is present above C II suggests
that SN 2011fe may have had an appreciable amount of unburned oxygen within the
outer layers of the ejecta.
05/2012;
-
S. R. Kulkarni
[show abstract]
[hide abstract]
ABSTRACT: This paper is an extended summary of the talk I gave at IAU Symposium "New
Horizons in Time Domain Astronomy" (Oxford, 2011). I first review the history
of transients (which is intimately related to the advent of wide-field
telescopic imaging; I then summarize wide field imaging projects. The
motivations that led to the design of the Palomar Transient Factory (PTF)
followed by a summary of the astronomical returns from PTF. I review the
lessons learnt from PTF. I conclude that, during this decade, optical transient
searches will continue to flourish and may even accelerate as surveys at other
wavelengths -- notably radio, UV and X-ray -- come on line. As a result, I
venture to suggest that specialized searches for transients will continue --
even into the LSST era. I end the article by discussing the importance of
follow-up telescopes for transient object studies -- a topical issue given that
in the US the Portfolio Review is under away.
02/2012;
-
A. Corsi,
E. O. Ofek,
A. Gal-Yam,
D. A. Frail,
D. Poznanski,
P. A. Mazzali, S. R. Kulkarni,
M. M. Kasliwal,
I. Arcavi,
S. Ben-Ami, [......],
I. K. W. Kleiser,
E. Nakar,
I. Rabinak,
R. Sari,
J. M. Silverman,
D. Xu,
J. S. Bloom,
N. M. Law,
P. E. Nugent,
and R. M. Quimby
[show abstract]
[hide abstract]
ABSTRACT: 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 4.5 R ☉ (R 1 R ☉) 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 1/4 R ☉ for the progenitor radius of this SN.
The Astrophysical Journal Letters 02/2012; 747(1):L5. · 5.53 Impact Factor
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Assaf Horesh, S. R. Kulkarni,
Derek B. Fox,
John Carpenter,
Mansi M. Kasliwal,
Eran O. Ofek,
Robert Quimby,
Avishay Gal-Yam,
S. Bradley Cenko,
A. G. de Bruyn, [......],
Chryssa Kouveliotou,
Philipp Podsiadlowski,
Mark Sullivan,
Kate Maguire,
D. Andrew Howell,
Peter E. Nugent,
Neil Gehrels,
Nicholas M. Law,
Dovi Poznanski,
and Michael Shara
[show abstract]
[hide abstract]
ABSTRACT: On 2011 August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN 2011fe), the youngest and most nearby Type Ia supernova (SN Ia) in decades. We followed this event up in the radio (centimeter and millimeter bands) and X-ray bands, starting about a day after the estimated explosion time. We present our analysis of the radio and X-ray observations, yielding the tightest constraints yet placed on the pre-explosion mass-loss rate from the progenitor system of this supernova. We find a robust limit of from sensitive X-ray non-detections, as well as a similar limit from radio data, which depends, however, on assumptions about microphysical parameters. We discuss our results in the context of single-degenerate models for SNe Ia and find that our observations modestly disfavor symbiotic progenitor models involving a red giant donor, but cannot constrain systems accreting from main-sequence or sub-giant stars, including the popular supersoft channel. In view of the proximity of PTF11kly and the sensitivity of our prompt observations, we would have to wait for a long time (a decade or longer) in order to more meaningfully probe the circumstellar matter of SNe Ia.
The Astrophysical Journal 01/2012; 746(1):21. · 6.02 Impact Factor
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Yi Cao,
Mansi M. Kasliwal,
James D. Neill, S. R. Kulkarni,
Yu-Qing Lou,
Sagi Ben-Ami,
Joshua S. Bloom,
S. Bradley Cenko,
Nicholas M. Law,
Peter E. Nugent,
Eran O. Ofek,
Dovi Poznanski,
Robert M. Quimby
[show abstract]
[hide abstract]
ABSTRACT: We present optical light curves of twenty-nine novae in M31 during the 2009
and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic
and rapid cadences in PTF monitoring of M31, from one day to even ten minutes,
provide excellent temporal coverage of nova light curves, enabling us to record
the photometric evolution of M31 novae in unprecedented detail. We also detect
eight of these novae in the near ultraviolet (UV) band with the Galaxy
Evolution Explorer (GALEX) satellite. Novae M31N2009-10b and 2010-11a show
prominent UV emission peaking a few days prior to their optical maxima,
possibly implying aspherical outbursts. Additionally, our blue-shifted spectrum
of the recent outburst of PT And (M31N2010-12a) indicates that it is a
recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously
assumed. Finally, we systematically searched for novae in all confirmed
globular clusters of M31 and found only M31N 2010-10f associated with Bol 126.
The specific nova rate in the M31 globular cluster system is thus about one per
year which is not enhanced relative to the rate outside the globular cluster
system.
01/2012;
-
D. Polishook,
E. O. Ofek,
A. Waszczak, S. R. Kulkarni,
A. Gal-Yam,
O. Aharonson,
R. Laher,
J. Surace,
C. Klein,
J. Bloom,
N. Brosch,
D. Prialnik,
C. Grillmair,
S. B. Cenko,
M. Kasliwal,
N. Law,
D. Levitan,
P. Nugent,
D. Poznanski,
R. Quimby
[show abstract]
[hide abstract]
ABSTRACT: 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.
01/2012;
-
E. O. Ofek,
R. Laher,
N. Law,
J. Surace,
D. Levitan,
B. Sesar,
A. Horesh,
D. Poznanski,
J. C. van Eyken, S. R. Kulkarni, [......],
M Sullivan,
M. Agueros,
L. Bildsten,
J. Bloom,
S. B. Cenko,
A. Gal-Yam,
C. Grillmair,
G. Helou,
M. M. Kasliwal,
R. Quimby
[show abstract]
[hide abstract]
ABSTRACT: The Palomar Transient Factory (PTF) provides multiple epoch imaging for a
large fraction of the sky. Here we describe the photometric calibration of the
PTF data products that relates the PTF magnitudes to other mag systems. The
calibration process utilizes SDSS r~16 mag point source objects as photometric
standards. During photometric conditions, this allows us to solve for the
extinction coefficients and color terms, and to estimate the camera
illumination correction. This also enables the calibration of fields that are
outside the SDSS footprint. We test the precision and repeatability of the PTF
photometric calibration. Given that PTF is observing in a single filter each
night, we define a PTF calibrated magnitude system for R-band and g-band. We
show that, in this system, 59% (47%) of the photometrically calibrated PTF
R-band (g-band) data achieve a photometric precision of 0.02-0.04 mag. Given
the objects' color, the PTF magnitude system can be converted to other systems.
A night-by-night comparison of the calibrated magnitudes of individual stars
observed on multiple nights shows that they are consistent to a level of ~0.02
mag. Most of the data that were taken under non-photometric conditions can be
calibrated relative to other epochs of the same sky footprint obtained during
photometric conditions. We provide a guide describing the use of the PTF
photometric calibration data products, as well as the transformations between
the PTF magnitude system and the SDSS and Johnson-Cousins systems. (abridged).
12/2011;
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Peter E Nugent,
Mark Sullivan,
S Bradley Cenko,
Rollin C Thomas,
Daniel Kasen,
D Andrew Howell,
David Bersier,
Joshua S Bloom, S R Kulkarni,
Michael T Kandrashoff, [......],
Mansi M Kasliwal,
Nicholas M Law,
Robert M Quimby,
Isobel M Hook,
Emma S Walker,
Paolo Mazzali,
Elena Pian,
Eran O Ofek,
Avishay Gal-Yam,
Dovi Poznanski
[show abstract]
[hide abstract]
ABSTRACT: Type Ia supernovae have been used empirically as 'standard candles' to demonstrate the acceleration of the expansion of the Universe even though fundamental details, such as the nature of their progenitor systems and how the stars explode, remain a mystery. There is consensus that a white dwarf star explodes after accreting matter in a binary system, but the secondary body could be anything from a main-sequence star to a red giant, or even another white dwarf. This uncertainty stems from the fact that no recent type Ia supernova has been discovered close enough to Earth to detect the stars before explosion. Here we report early observations of supernova SN 2011fe in the galaxy M101 at a distance from Earth of 6.4 megaparsecs. We find that the exploding star was probably a carbon-oxygen white dwarf, and from the lack of an early shock we conclude that the companion was probably a main-sequence star. Early spectroscopy shows high-velocity oxygen that slows rapidly, on a timescale of hours, and extensive mixing of newly synthesized intermediate-mass elements in the outermost layers of the supernova. A companion paper uses pre-explosion images to rule out luminous red giants and most helium stars as companions to the progenitor.
Nature 12/2011; 480(7377):344-7. · 36.28 Impact Factor