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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"
  1. GRB 251014A: Swift-BAT refined analysis
  2. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  4. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  5. GRB 251014D: Swift detection of a burst
  6. GRB 251014A: PRIME near-infrared upper limits
  7. GRB 251014C: Fermi GBM Final Localization
  8. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  9. GRB 251014A: VLT/FORS2 Optical Observation
  10. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  11. GRB 251012A: Glowbug gamma-ray detection of a likely short burst
  12. GRB 251013C: MarSEC, optical afterglow photometry
  13. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  14. GRB 251014B: Swift ToO observations
  15. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  16. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  17. GRB 251013C: Bassano Bresciano Observatory optical observations
  18. GRB 251013C: Early and late-time optical counterpart detection by LCO
  19. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  20. GRB 251013C: Fermi GBM Observation
  21. GRB 251013D: Swift ToO observations
  22. GRB 251014A: DDOTI Upper Limit
  23. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  24. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  25. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  26. GRB 251013C: Asiago optical observations
  27. GRB 251013A: CALET Gamma-Ray Burst Monitor detection
  28. GRB 251013C: ABObservatory optical observations
  29. GRB 251014A: SAO RAS optical upper limit
  30. GRB 251014A: Fermi GBM Observation
  31. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  32. GRB 251013C: EP-FXT counterpart detection
  33. GRB 251013C: AstroSat CZTI detection
  34. GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
  35. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  36. GRB 251013C: ALMA detection
  37. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  38. GRB 251013C: DDOTI detection of the optical afterglow
  39. GRB 251013C: SLKT optical afterglow photometry
  40. Swift GRB 251014A: Global MASTER-Net observations report
  41. GRB 251014A: Swift detection of a possibly-short burst
  42. GRB 251014A: Fermi GBM Final Real-time Localization
  43. Fermi trigger No 782044789: Global MASTER-Net observations report
  44. Fermi GRB 251013C: Global MASTER-Net observations report
  45. Fermi GRB 251013B: Global MASTER-Net observations report
  46. Fermi GRB 251013D: Global MASTER-Net observations report
  47. GRB 251013C: Swift-XRT counterpart detection
  48. GRB 251013C: GOTO optical afterglow detection
  49. GRB 251013C: SAO RAS optical observations
  50. GRB 251013C: LCO optical afterglow detection
  51. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  52. GRB 251013C: NOT spectroscopic redshift z = 0.572
  53. GRB 251013C: LAST detection of optical counterpart
  54. GRB 251013C: BOOTES-6 early optical detection
  55. GRB 251013D: Fermi GBM Final Real-time Localization
  56. GRB 251013C: SVOM/VT optical observation
  57. GRB 251013C: SVOM detection of a burst
  58. GRB 251013C: Fermi GBM Final Real-time Localization
  59. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  60. GRB 251013B: SVOM/GRM observation
  61. GRB 251013A: SVOM/GRM observation
  62. GRB 251003A: Mondy optical upper limit
  63. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  64. GRB 251013B: Fermi GBM Final Real-time Localization
  65. Fermi GRB 251013A: Global MASTER-Net observations report
  66. GRB 251013A: Fermi GBM Final Real-time Localization
  67. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  68. GRB 251011B inspection: MASTER orphan GRB detection
  69. GRB 251011A: Insight-HXMT detection
  70. GRB 251011B: Swift/UVOT Upper Limits
  71. Fermi GRB 251011A: Global MASTER-Net observations report
  72. GRB 251012A: Fermi GBM Final Real-time Localization
  73. GRB 251011B: SVOM/GRM observation
  74. GRB 251011B: Swift-XRT refined Analysis
  75. GRB 251011B: Fermi GBM Observation
  76. GRB 251011B : MASTER optical observations
  77. GRB 251011C: Fermi GBM Final Real-time Localization
  78. GRB 251011B: Enhanced Swift-XRT position
  79. GRB 251010A: AstroSat CZTI detection
  80. GRB 251011A: AstroSat CZTI detection
  81. GRB 251009B: SVOM/GRM observation of short GRB
  82. GRB 251011B: Swift detection of a burst
  83. GRB 251011B: Fermi GBM Final Real-time Localization
  84. GRB 251011A: Fermi GBM Final Real-time Localization
  85. Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
  86. GRB 251007B: Swift/UVOT Upper Limits
  87. GRB 251010A: Fermi GBM Final Real-time Localization
  88. GRB251007A: Swift/UVOT Detection
  89. GRB 251009A: GECAM-B detection of a short burst
  90. GRB 251009A: Insight-HXMT detection of a short burst
  91. GRB 251009B (short): Glowbug gamma-ray detection
  92. GRB 251009B: Insight-HXMT detection of a short burst
  93. GRB 251007A: Swift-BAT refined analysis
  94. GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
  95. GRB 251007A: SVOM/GRM observation
  96. GRB 251007A: Insight-HXMT detection
  97. GRB 251006A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 251007B - SVOM/ECLAIRs refined analysis
  99. SVOM/sb25101004: SVOM detection of a stellar flare
  100. GRB 251009A: Fermi GBM Final Localization

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