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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24915 results found.

  1. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  2. GRB 251006A (short): Glowbug gamma-ray detection
  3. GRB 251005C: COLIBRÍ optical observations
  4. GRB 251005C: VLT/X-shooter Imaging
  5. GRB 251003A: LAST optical observations
  6. GRB 251002A: LAST optical observations
  7. GRB 251005​C: Swift/UVOT Upper Limits
  8. GRB 250902A: MSU cubesats detection
  9. GRB 251005C: Swift-XRT refined Analysis
  10. GRB 251005C: Fermi GBM Observation
  11. GRB 251005C: Enhanced Swift-XRT position
  12. GRB 251005C: Swift detection of a burst
  13. GRB 251002A: Mondy/AZT-33IK optical observations
  14. EP251003a: Einstein Probe detection of an X-ray transient
  15. GRB 251003A: J-band detection with WINTER
  16. GRB 251002A: NIR observations with WINTER
  17. GRB 251003A: Swift-BAT refined analysis
  18. GRB 251001B: NIR observations with WINTER
  19. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  20. GRB 251003A: Swift/UVOT Upper Limits
  21. GRB 251002A: Swift/UVOT detection
  22. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  23. GRB 251003A: Swift-XRT refined Analysis
  24. GRB 251002A: Fermi GBM Observation
  25. GRB 251002A: GOTO detection of optical counterpart
  26. GRB 251001C: SVOM/GRM observation
  27. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  28. GRB 251003A: Enhanced Swift-XRT position
  29. GRB 251002A: AKO Early Optical Afterglow Detection
  30. GRB 251003A: Kilonova-Catcher optical afterglow detection
  31. GRB 251002A: Swift-XRT afterglow detection
  32. GRB 251001B: AbAO optical upper limit
  33. GRB 251002A: Kilonova-Catcher optical afterglow detection
  34. GRB 251002A: AbAO optical observations
  35. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  36. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  37. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  38. GRB 251003A: LCOGT Optical Detection
  39. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  40. GRB 251003A: Swift detection of a burst
  41. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  42. GRB 251002A: BOOTES-6 early optical detection
  43. GRB 251002A: SAO RAS optical observations
  44. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  45. GRB 251002A: LCO optical observation
  46. GRB 251002A: SVOM/VT optical observation
  47. GRB 251002A: SVOM detection of a burst
  48. GRB 251001A: SVOM/GRM observation
  49. GRB 251001B: Swift/UVOT Detection
  50. GRB 251001B: COLIBRÍ optical observations
  51. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  52. GRB 251001B: Swift-XRT refined Analysis
  53. GRB 251001B: SVOM/VT optical observation
  54. GRB 251001B: NOT optical observations
  55. GRB 251001C: Glowbug gamma-ray detection
  56. GRB 251001B: Fermi GBM Observation
  57. GRB 251001B: Enhanced Swift-XRT position
  58. GRB 251001B: LCOGT Optical Observations
  59. GRB 250930A: SVOM/GRM observation
  60. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  61. GRB 251001B: Swift detection of a burst
  62. GRB 251001A: Fermi GBM Detection
  63. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  64. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  65. GRB 250925A: MAO/AZT-22 optical observations
  66. GRB 250925A: Mondy I-band optical observations
  67. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  68. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  69. GRB 250924A: SVOM/GRM observation
  70. GRB 250925A: Swift-XRT refined Analysis
  71. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  73. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  74. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  75. GRB 250925A: Mondy and AbAO optical observations
  76. GRB 250925A: SVOM/GWAC-F60A upper limit
  77. GRB 250925A/EP250925a: EP-WXT detection
  78. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  79. GRB 250925A : MITSuME Akeno optical upper limits
  80. GRB 250925A: JinShan optical observations
  81. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  82. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  83. GRB250925A: Liverpool Telescope optical observations
  84. GRB 250925A: NOT optical afterglow candidate
  85. GRB 250925A: Leavitt Observatory optical upper limit
  86. GRB 250925A: Enhanced Swift-XRT position
  87. GRB 250925A: GROWTH-India Telescope Upper Limits
  88. GRB 250922A: SVOM/GRM observation
  89. GRB 250924A: 1.6m Mephisto optical upper limits
  90. GRB 250924A: SAO RAS optical observations
  91. GRB 250914A: AstroSat CZTI detection
  92. GRB 250920B: AstroSat CZTI detection
  93. GRB 250924A: SVOM/VT optical observation
  94. GRB 250924A: Swift/UVOT Detection
  95. GRB 250924A: Swift-XRT refined Analysis
  96. GRB 250924A: Enhanced Swift-XRT position
  97. GRB 250924A: J-band detection with WINTER
  98. GRB 250924A: GROWTH-India Telescope Upper Limits
  99. GRB 250924A: Mondy optical observations, afterglow fading
  100. GRB 250924A: Kilonova-Catcher optical afterglow detection

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