데이터셋 상세
미국
UV/X-Ray Data for M Dwarfs Within 10 Parsecs
M dwarfs are the most numerous stars in the galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual presence of life on them. The authors systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10 pc to obtain a nearly volume-limited sample (~90% completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of H-alpha emission and rotation to obtain a broad picture of stellar activity on M dwarfs. The authors make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. They also analyze the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (~10 Myr old). The authors find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the H-alpha, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. The authors present in the reference paper for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as the flux ratios between the activity diagnostics and the bolometric flux of the star in analogy to the Ca II R'(HK) index. For a given spectral type, these indices display a spread of 2-3 dex which is largest for M4-type stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and H-alpha, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TW Hya members shows a drop of nearly three orders of magnitude for the luminosity in these bands between ~10 Myr and a few Gyr age. A few young field dwarfs (<1 Gyr) in the 10-pc sample bridge the gap indicating that the drop in magnetic activity with age is a continuous process. The slope of the age decay is steeper for the X-ray than for the UV luminosity. This sample is based on the All-Sky Catalog of bright M dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/142/138">CDS Cat. J/AJ/142/138</a>, available at the HEASARC as the MDWARFASC table). The authors selected all 163 stars from this reference that are within 10pc. Four of these stars that were discovered to be actually late K-type stars were removed from this initial sample, leaving a final sample of 159 stars. This table was created by the HEASARC in July 2017 based upon <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/431/2063">CDS Catalog J/MNRAS/431/2063</a> files table1.dat and table2.dat. The positions of the stars were not explicitly given in these tables, but were taken by the HEASARC from the All-Sky Catalog of Bright M Dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/142/138">CDS Cat. J/AJ/142/138</a>, available at the HEASARC as the MDWARFASC table). The version of Table 2 used by the HEASARC is the corrected one given in the Erratum (Stelzer et al. 2014) rather than the version given in the original paper (Stelzer et al. 2013). This is a service provided by NASA HEASARC .
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연관 데이터
Joanna Berteaud - Parkes observations for project P1317 semester 2024OCTS 06
공공데이터포털
The existence of a population of millisecond pulsars (MSPs) in the Galactic bulge is supported, among others, by the Fermi GeV excess, a signal of gamma rays coming from the Galactic center (GC) direction and resembling the cumulative emission of known MSPs. A previous study showed that, while these MSPs are unresolved in gamma rays, some of them could have been detected in past X-ray observations. The authors also identified a large number of MSP candidates among unidentified X-ray sources. By analyzing unpublished radio images, we found interesting radio counterparts to 6 of those candidates, and were granted 20h of observations with the Green Bank Telescope to settle on their nature. We discovered two new MSPs, PSR J1740-2807 and PSR J1740-2805, towards one of our radio/X-ray targets, bringing to 4 the number of highly-dispersed MSPs in the GC direction and probably unveiling the first direct evidence of a bulge MSP population. We propose to carry out regular timing of these pulsar with Parkes, in order to reveal their properties and potentially claim association of PSR J1740-2807 with the original X-ray source. The follow up of these sources will have a major impact on our understanding of the Fermi GeV excess.
Joanne Dawson - Parkes observations for project P1321 semester 2024OCTS 02
공공데이터포털
We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. This project successfully observed in 2024APR and will be expanded to a Long Term Project when that scheme reopens for applications in 2025APR. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.
Joanne Dawson - Parkes observations for project P1321 semester 2024OCTS 07
공공데이터포털
We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. This project successfully observed in 2024APR and will be expanded to a Long Term Project when that scheme reopens for applications in 2025APR. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.
Joanne Dawson - Parkes observations for project P1321 semester 2024APRS 02
공공데이터포털
We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. Following the success of this pilot project, we plan to expand to a long-term monitoring programme. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.
Joanne Dawson - Parkes observations for project P1321 semester 2024APRS 01
공공데이터포털
We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. Following the success of this pilot project, we plan to expand to a long-term monitoring programme. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.
Megan DeCesar - Parkes observations for project P1347 semester 2024OCTS 05
공공데이터포털
A MeerKAT imaging survey of the Galactic Center and Bulge region yielded the detections of 39 known pulsars and 30 pulsar candidates. The candidates were identified primarily as steep-spectrum, circularly- and/or linearly-polarized sources, and to a lesser degree by the level of radio variability observed. We have chosen nine pulsar candidates to target in this proposal. These sources are the most pulsar-like of the MeerKAT point sources (based on their polarization, spectral index, and variability) that also have large enough flux densities to make a firm detection of pulsations if present. We propose to observe these nine candidates twice, for 1.5 hr each, in the 2024OCT semester.
Marlon Bause - Parkes observations for project P1356 semester 2025APRS 03
공공데이터포털
Magnetars are neutron stars with exceptionally high magnetic fields. From the 30 known magnetars, only six have had radio emission detected so far. The remaining 24 magnetars are generally only searched for radio emission after an X-ray outburst. This added a strong selection bias to whether magnetars are radio loud or not. From the known six radio loud magnetars, we know that the radio emission changes quickly with time and for the magnetar XTE J1810-197, it has been observed that the radio flux increases strongly without an enhancement in X-ray flux. Thus, it remains unclear whether the radio quiet magnetars are in fact radio quiet and the radio X-ray relation appears to be rather complex. In this proposal, we propose a regular monitoring campaign of 4 radio quiet magnetars with bi-weekly observations using the Parkes UWL receiver. For 3 of the sources, we will have accompanying X-ray observations and thus, this will give an unique data set to probe the relation between radio and X-ray independent outbursts. Any detection of radio emission, i.e. single pulses or folded profiles, would be a major discovery and help to constrain the emission mechanisms of magnetars. This will also help to improve the understanding of the emission mechanism of fast radio bursts. However, also a non-detection of radio emission will provide upper limits that serve as a baseline before any future outburst of the observed magnetars as well as allow to constrain the formation process of magnetars in contrast to pulsars.
Marlon Bause - Parkes observations for project P1356 semester 2025APRS 04
공공데이터포털
Magnetars are neutron stars with exceptionally high magnetic fields. From the 30 known magnetars, only six have had radio emission detected so far. The remaining 24 magnetars are generally only searched for radio emission after an X-ray outburst. This added a strong selection bias to whether magnetars are radio loud or not. From the known six radio loud magnetars, we know that the radio emission changes quickly with time and for the magnetar XTE J1810-197, it has been observed that the radio flux increases strongly without an enhancement in X-ray flux. Thus, it remains unclear whether the radio quiet magnetars are in fact radio quiet and the radio X-ray relation appears to be rather complex. In this proposal, we propose a regular monitoring campaign of 4 radio quiet magnetars with bi-weekly observations using the Parkes UWL receiver. For 3 of the sources, we will have accompanying X-ray observations and thus, this will give an unique data set to probe the relation between radio and X-ray independent outbursts. Any detection of radio emission, i.e. single pulses or folded profiles, would be a major discovery and help to constrain the emission mechanisms of magnetars. This will also help to improve the understanding of the emission mechanism of fast radio bursts. However, also a non-detection of radio emission will provide upper limits that serve as a baseline before any future outburst of the observed magnetars as well as allow to constrain the formation process of magnetars in contrast to pulsars.
Mengting Liu - Parkes observations for project P1219 semester 2025APRS 02
공공데이터포털
Magnetic fields are fundamental in regulating star formation and the evolution of molecular clouds. Zeeman splitting offers a unique method to directly measure line-of-sight magnetic field strengths in interstellar environments, from the diffuse ISM to dense cores. Observations of HI and OH absorption toward pulsars provide an unprecedented opportunity to measure magnetic fields with high precision, benefiting from pulsars' small angular sizes and reliable Stokes V spectra unaffected by instrumental effects. Our recent tentative Zeeman splitting detections in OH absorption toward PSR J1644-4559 with Parkes reveal magnetic field strengths that suggest magnetically subcritical states, where magnetic pressure counteracts gravity. This challenges conventional theories of subcritical cold neutral medium (CNM) transitioning to supercritical star-forming molecular clouds, emphasizing the need for detailed investigation. We propose a continuation of Zeeman splitting studies through high-sensitivity OH and HI absorption observations of pulsars PSR J1644-4559, J1721-3532, and J1852+0031 using Parkes. By employing an innovative phase-resolved spectral technique and extending integration times, we aim to enhance Zeeman detection sensitivity and study magnetic field transitions in the CNM and quiescent molecular clouds. This work will refine our understanding of subcritical-to-supercritical transitions in star formation, establish pulsar absorption as a robust probe of interstellar magnetic fields, and advance observational techniques critical to star formation studies.
Marlon Bause - Parkes observations for project P1356 semester 2025APRS 01
공공데이터포털
Magnetars are neutron stars with exceptionally high magnetic fields. From the 30 known magnetars, only six have had radio emission detected so far. The remaining 24 magnetars are generally only searched for radio emission after an X-ray outburst. This added a strong selection bias to whether magnetars are radio loud or not. From the known six radio loud magnetars, we know that the radio emission changes quickly with time and for the magnetar XTE J1810-197, it has been observed that the radio flux increases strongly without an enhancement in X-ray flux. Thus, it remains unclear whether the radio quiet magnetars are in fact radio quiet and the radio X-ray relation appears to be rather complex. In this proposal, we propose a regular monitoring campaign of 4 radio quiet magnetars with bi-weekly observations using the Parkes UWL receiver. For 3 of the sources, we will have accompanying X-ray observations and thus, this will give an unique data set to probe the relation between radio and X-ray independent outbursts. Any detection of radio emission, i.e. single pulses or folded profiles, would be a major discovery and help to constrain the emission mechanisms of magnetars. This will also help to improve the understanding of the emission mechanism of fast radio bursts. However, also a non-detection of radio emission will provide upper limits that serve as a baseline before any future outburst of the observed magnetars as well as allow to constrain the formation process of magnetars in contrast to pulsars.
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