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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').

22216 results found.

  1. GRB 240426A: VZLUSAT-2 detection
  2. GRB 240425A: VZLUSAT-2 detection
  3. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  4. GRB 240501B: AstroSat CZTI detection
  5. GRB 240501A: Fermi GBM Final Real-time Localization
  6. GRB 240408B: VZLUSAT-2 detection
  7. GRB 240407A: VZLUSAT-2 detection
  8. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  10. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  12. Additional DECam GW-MMADS Candidates from three nights of observations
  13. Fermi-LAT gamma-ray observations of IceCube-240424A
  14. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  15. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  16. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  17. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  18. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  19. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  21. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  22. EP240426b: AST3-2 optical upper limit
  23. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  24. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  25. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  26. EP240426b: EP-WXT detection of a new fast X-ray transient
  27. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  28. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  29. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  30. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  31. GRB 240426A: AstroSat CZTI detection
  32. XMM-Newton observation of EP240426a
  33. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  34. GRB 240414A: NOEMA detection
  35. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  36. EP240426a: GMG optical upper limit
  37. LVK S240422ed: Further Swift-XRT followup of three sources
  38. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  39. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  40. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  41. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  42. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  43. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  44. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  45. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  46. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  47. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  48. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  49. GRB 240419B: Swift-BAT refined analysis
  50. GRB 240421B: Swift-BAT refined analysis
  51. GRB 240422A: Glowbug gamma-ray detection
  52. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  53. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  54. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  55. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  56. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  57. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  58. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  59. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  60. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  61. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  62. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  63. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  64. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  65. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  66. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  67. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  68. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  69. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  70. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  71. GRB 240419A: Swift-BAT refined analysis
  72. GRB 240418A: Swift-BAT refined analysis
  73. LXT240402A/GRB240402B: Chandra X-ray detection
  74. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  75. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  76. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  77. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  78. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  79. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  80. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  81. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  82. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  83. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  84. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  86. GRB 240421A: Glowbug gamma-ray detection
  87. GRB 240414A: radio detection with the VLA
  88. Fermi-LAT gamma-ray observations of IceCube-240419A
  89. GRB 240414A: AMI-LA radio observations
  90. GRB 240414A: LBT optical detection
  91. GRB 240419B : MITSuME Akeno optical upper limits
  92. GRB 240415B: Swift-XRT observations
  93. GRB 240415A: Swift-XRT refined Analysis
  94. GRB240421B: Zadko Observations
  95. GRB 240421B: Fermi GBM Observation
  96. GRB 240421B: Swift-XRT refined Analysis
  97. GRB240421B: BOOTES-5/JGT optical upper limit
  98. GRB 240421B: J-band upper limits from WINTER
  99. GRB 240421B: Swift/UVOT Upper Limits
  100. GRB 240421B: Enhanced Swift-XRT position

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