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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 251016B: Fermi GBM Final Real-time Localization
  2. GRB 251014D: Swift-BAT refined analysis
  3. GRB 251016A: BOOTES-6/DPRT optical upper limit
  4. GRB 251016A: Glowbug gamma-ray detection of a short burst
  5. GRB 251013C: VLA detection
  6. sb25101602: Swift-XRT counterpart detection
  7. Fermi GRB 251016A: Global MASTER-Net observations report
  8. GRB 251016A: Fermi GBM Final Localization
  9. GRB 251016A: SVOM detection of a short burst
  10. GRB 251014A: Swift-XRT observations
  11. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  12. GRB 251014B: PRIME J-band upper limit
  13. Upper limits from a search for additional neutrino events in IceCube
  14. IceCube Alert 251014.77: Global MASTER-Net observations report
  15. Swift GRB251015.60: Global MASTER-Net observations report
  16. GRB 251013C: Kilonova-Catcher optical afterglow detection
  17. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  18. GRB 251013D: Swift/UVOT Observations
  19. GRB 251013C: Swift/UVOT Detection
  20. Konus-Wind detection of GRB 251007A
  21. Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
  22. GRB 251013C, GCN Circular 42267, errata corrige
  23. GRB 251013C: detection of a radio counterpart at 15.5GHz
  24. GRB 251015A: Fermi GBM Final Real-time Localization
  25. GRB 251013C: SVOM/ECLAIRs refined analysis
  26. GRB 251013D: Swift-XRT observations
  27. Swift Trigger 1404295: possible GRB 251015A
  28. GRB 251014B: Swift-XRT observations
  29. GRB 251014B: Swift/UVOT Upper Limits
  30. GRB 251014B: VLT/FORS2 Optical Observation
  31. GRB 251014D: Swift/UVOT Upper Limits
  32. GRB 251014D: BOOTES-6/DPRT optical upper limit
  33. GRB 251014D: Swift-XRT afterglow detection
  34. GRB 251013C: MAO/AZT-22 optical observations
  35. GRB 251011B: SVOM/VT optical upper limit
  36. GRB 251013C: Swift ToO observations
  37. GRB 251013D: Fermi GBM Observation
  38. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  39. GRB 251014A: Swift-BAT refined analysis
  40. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  41. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  42. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  43. GRB 251014D: Swift detection of a burst
  44. GRB 251014A: PRIME near-infrared upper limits
  45. GRB 251014C: Fermi GBM Final Localization
  46. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  47. GRB 251014A: VLT/FORS2 Optical Observation
  48. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  49. GRB 251012A: Glowbug gamma-ray detection of a likely short burst
  50. GRB 251013C: MarSEC, optical afterglow photometry
  51. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  52. GRB 251014B: Swift ToO observations
  53. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  54. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  55. GRB 251013C: Bassano Bresciano Observatory optical observations
  56. GRB 251013C: Early and late-time optical counterpart detection by LCO
  57. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  58. GRB 251013C: Fermi GBM Observation
  59. GRB 251013D: Swift ToO observations
  60. GRB 251014A: DDOTI Upper Limit
  61. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  62. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  63. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  64. GRB 251013C: Asiago optical observations
  65. GRB 251013A: CALET Gamma-Ray Burst Monitor detection
  66. GRB 251013C: ABObservatory optical observations
  67. GRB 251014A: SAO RAS optical upper limit
  68. GRB 251014A: Fermi GBM Observation
  69. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  70. GRB 251013C: EP-FXT counterpart detection
  71. GRB 251013C: AstroSat CZTI detection
  72. GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
  73. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  74. GRB 251013C: ALMA detection
  75. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  76. GRB 251013C: DDOTI detection of the optical afterglow
  77. GRB 251013C: SLKT optical afterglow photometry
  78. Swift GRB 251014A: Global MASTER-Net observations report
  79. GRB 251014A: Swift detection of a possibly-short burst
  80. GRB 251014A: Fermi GBM Final Real-time Localization
  81. Fermi trigger No 782044789: Global MASTER-Net observations report
  82. Fermi GRB 251013C: Global MASTER-Net observations report
  83. Fermi GRB 251013B: Global MASTER-Net observations report
  84. Fermi GRB 251013D: Global MASTER-Net observations report
  85. GRB 251013C: Swift-XRT counterpart detection
  86. GRB 251013C: GOTO optical afterglow detection
  87. GRB 251013C: SAO RAS optical observations
  88. GRB 251013C: LCO optical afterglow detection
  89. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  90. GRB 251013C: NOT spectroscopic redshift z = 0.572
  91. GRB 251013C: LAST detection of optical counterpart
  92. GRB 251013C: BOOTES-6 early optical detection
  93. GRB 251013D: Fermi GBM Final Real-time Localization
  94. GRB 251013C: SVOM/VT optical observation
  95. GRB 251013C: SVOM detection of a burst
  96. GRB 251013C: Fermi GBM Final Real-time Localization
  97. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  98. GRB 251013B: SVOM/GRM observation
  99. GRB 251013A: SVOM/GRM observation
  100. GRB 251003A: Mondy optical upper limit

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