Andreas Ritter

Dr. Andreas Ritter

The University of Hong Kong
orcid

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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17 January 2017 in The Astronomical Journal
Verified
Journal Article
Open access
PDF file
Andrea KunderAndrea Kunder
Andrea Kunder
GKGeorges Kordopatis
Georges Kordopatis
MSMatthias Steinmetz
Matthias Steinmetz
TZTomaž Zwitter
Tomaž Zwitter
PMPaul J. McMillan
Paul J. McMillan
BMB. Mosser
B. Mosser
Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is the fifth data release from a magnitude-limited ( ) survey of stars randomly selected in the Southern Hemisphere. The RAVE medium-resolution spectra ( ) covering the Ca-triplet region (8410–8795 Å) span the complete time frame from the start of RAVE observations in 2003 to their completion in 2013. Radial velocities from 520,781 spectra of 457,588 unique stars are presented, of which 255,922 stellar observations have parallaxes and proper motions from the Tycho-Gaia astrometric solution in Gaia DR1. For our main DR5 catalog, stellar parameters (effective temperature, surface gravity, and overall metallicity) are computed using the RAVE DR4 stellar pipeline, but calibrated using recent K2 Campaign 1 seismic gravities and Gaia benchmark stars, as well as results obtained from high-resolution studies. Also included are temperatures from the Infrared Flux Method, and we provide a catalog of red giant stars in the dereddened color interval (0.50, 0.85) for which the gravities were calibrated based only on seismology. Further data products for subsamples of the RAVE stars include individual abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni, and distances found using isochrones. Each RAVE spectrum is complemented by an error spectrum, which has been used to determine uncertainties on the parameters. The data can be accessed via the RAVE Web site or the VizieR database.

12 February 2018 in Publications of the Astronomical Society of the Pacific
Verified
Journal Article
Closed access
NBNadejda Blagorodnova
Nadejda Blagorodnova
JNJames D. Neill
James D. Neill
RWRichard Walters
Richard Walters
SKShrinivas R. Kulkarni
Shrinivas R. Kulkarni
CFChristoffer Fremling
Christoffer Fremling
KVKarl E. Vyhmeister
Karl E. Vyhmeister

27 July 2020 in The Astronomical Journal
Verified
Journal Article
Closed access
MSMatthias Steinmetz
Matthias Steinmetz
GGGuillaume Guiglion
Guillaume Guiglion
PMPaul J. McMillan
Paul J. McMillan
GMGal Matijevič
Gal Matijevič
HEHarry Enke
Harry Enke
(C(The Rave collaboration)
(The Rave collaboration)
We present part 2 of the sixth and final Data Release (DR6) of the Radial Velocity Experiment (Rave), a magnitude-limited ( ) spectroscopic survey of Galactic stars randomly selected in Earth’s southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca triplet region (8410–8795 Å) and span the complete time frame from the start of Rave observations on 2003 April 12 to their completion on 2013 April 4. In the second of two publications, we present the data products derived from 518,387 observations of 451,783 unique stars using a suite of advanced reduction pipelines focusing on stellar atmospheric parameters, in particular purely spectroscopically derived stellar atmospheric parameters ( , , and the overall metallicity), enhanced stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar atmospheric parameters for giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [α/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios. The Rave DR6 catalogs are cross-matched with relevant astrometric and photometric catalogs, and are complemented by orbital parameters and effective temperatures based on the infrared flux method. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database.

27 July 2020 in The Astronomical Journal
Verified
Journal Article
Closed access
MSMatthias Steinmetz
Matthias Steinmetz
GMGal Matijevič
Gal Matijevič
HEHarry Enke
Harry Enke
TZTomaž Zwitter
Tomaž Zwitter
GGGuillaume Guiglion
Guillaume Guiglion
(C(The Rave collaboration)
(The Rave collaboration)
The Radial Velocity Experiment (Rave) is a magnitude-limited (9 < I < 12) spectroscopic survey of Galactic stars randomly selected in Earth’s southern hemisphere. The Rave medium-resolution spectra (R ∼ 7500) cover the Ca-triplet region (8410–8795 Å). The sixth and final data release (DR6) is based on 518,387 observations of 451,783 unique stars. Rave observations were taken between 2003 April 12 and 2013 April 4. Here we present the genesis, setup, and data reduction of Rave as well as wavelength-calibrated and flux-normalized spectra and error spectra for all observations in Rave DR6. Furthermore, we present derived spectral classification and radial velocities for the Rave targets, complemented by cross-matches with Gaia DR2 and other relevant catalogs. A comparison between internal error estimates, variances derived from stars with more than one observing epoch, and a comparison with radial velocities of Gaia DR2 reveals consistently that 68% of the objects have a velocity accuracy better than 1.4 km s–1, while 95% of the objects have radial velocities better than 4.0 km s–1. Stellar atmospheric parameters, abundances and distances are presented in a subsequent publication. The data can be accessed via the Rave website (http://rave-survey.org) or the Vizier database.

9 August 2016
Verified
Conference Paper
Open access
PDF file
NTNaoyuki Tamura
Naoyuki Tamura
NTNaruhisa Takato
Naruhisa Takato
ASAtsushi Shimono
Atsushi Shimono
YMYuki Moritani
Yuki Moritani
KYKiyoto Yabe
Kiyoto Yabe
NYNaoki Yasuda
Naoki Yasuda
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~1.6 - 2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.

1 September 2021 in The Astrophysical Journal Letters
Verified
Journal Article
Open access
PDF file
Andreas RitterAndreas Ritter
Andreas Ritter
Quentin A.  ParkerQuentin A. Parker
Quentin A. Parker
FLFoteini Lykou
Foteini Lykou
AZAlbert Zijlstra
Albert Zijlstra
Martin A GuerreroMartin A Guerrero
Martin A Guerrero
PDPascal Le Dû
Pascal Le Dû
The guest star of AD 1181 is the only historical supernova of the past millennium that is without a definite counterpart. The previously proposed association with supernova remnant G130.7+3.1 (3C 58) is in strong doubt because of the inferred age of this remnant. Here we report a new identification of SN 1181 with our codiscovery of the hottest known Wolf–Rayet star of the oxygen sequence (IRAS 00500+6713 or 2MASS J00531123+6730023, here named by us as “Parker's star”) and its surrounding nebula Pa 30. Our spectroscopy of the nebula shows a fast shock with extreme velocities of ≈1100 km s−1. The derived expansion age of the nebula implies an explosive event ≈1000 yr ago that agrees with the 1181 event. The on-sky location also fits the historical Chinese and Japanese reports of SN 1181 to within 3.°5. Pa 30 and Parker’s star have previously been proposed to be the result of a double-degenerate merger, leading to a rare Type Iax supernova. The likely historical magnitude and the distance suggest the event was subluminous for normal supernova. This agrees with the proposed Type Iax association that would also be only the second of its kind in the Galaxy. Taken together, the age, location, event magnitude, and duration elevate Pa 30 to prime position as the counterpart of SN 1181. This source is the only Type Iax supernova where detailed studies of the remnant star and nebula are possible. It provides strong observational support for the double-degenerate merger scenario for Type Iax supernovae.