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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"

3757 results found.

  1. EP260104a: Global MASTER-Net observations report
  2. EP260105a: Global MASTER-Net observations report
  3. Fermi GRB 260104B: Global MASTER-Net observations report
  4. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  5. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  7. Fermi GRB 251228A: Global MASTER-Net observations report
  8. GRB 251228A: Fermi GBM Final Real-time Localization
  9. SVOM GRB251227.07: Global MASTER-Net observations report
  10. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  11. EP251222a: Global MASTER-Net observations report
  12. GRB 251222A: 1.3m DFOT optical detection
  13. GRB251221A: 7DT optical upper limits
  14. EP251222b/GRB 251222A: SVOM/GRM observation
  15. GRB 251221A: Fermi GBM Observation
  16. GRB 251221A: Fermi GBM Final Real-time Localization
  17. EP251220a: Global MASTER-Net observations report
  18. IceCube Alert 251218.85: Global MASTER-Net observations report
  19. Fermi GRB 251216A: Global MASTER-Net observations report
  20. GRB 251214B: Mondy optical upper limit
  21. Fermi GRB 251215A: Global MASTER-Net observations report
  22. EP251214b: Global MASTER-Net observations report
  23. GRB 251214B: COLIBRÍ observations of the afterglow
  24. Fermi trigger No 787396657: Global MASTER-Net observations report
  25. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  26. IPN triangulation of GRB 251129B (short/hard)
  27. GRB 251130B: AstroSat CZTI detection
  28. GRB 251201B: Swift detection of a burst with an optical counterpart
  29. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  30. Fermi GRB 251130B: Global MASTER-Net observations report
  31. EP251130a: COLIBRÍ optical counterpart candidate
  32. GRB 251128A: AstroSat CZTI detection
  33. GRB 251126A: SAO RAS optical observations
  34. GRB 251128A: Fermi GBM Observation
  35. Fermi GRB 251128A: Global MASTER-Net observations report
  36. GRB 251126A: further SAO RAS optical observations
  37. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  38. GRB 251128A: Fermi GBM Final Real-time Localization
  39. Fermi GRB 251125A: Global MASTER-Net observations report
  40. EP251118a: Xinglong-2.16m optical observation
  41. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  42. GRB 251018A: FRAM-Auger optical detection
  43. LAT GRB251118.86: Global MASTER-Net observations report
  44. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  45. GRB 251115A: Swift-XRT observations
  46. GRB 251116C: Swift-XRT observations
  47. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  48. GRB 251116C: SVOM/VT optical upper limit
  49. GRB 251025B: further Mondy optical observations
  50. Fermi GRB 251115A: Global MASTER-Net observations report
  51. GRB 251112A: Swift-BAT refined analysis
  52. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  53. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  54. Fermi GRB 251114A: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  56. Swift Trigger 1413695: a possible GRB 251112A
  57. GRB 251111A: SVOM/VT optical observations with X-band data
  58. GRB 251105A: AstroSat CZTI detection
  59. SVOM GRB251108.54: Global MASTER-Net observations report
  60. SVOM GRB251106.83: Global MASTER-Net observations report
  61. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 251104A: SVOM detection of a burst
  63. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  64. Fermi GRB 251103A: Global MASTER-Net observations report
  65. Fermi GRB 251102A: Global MASTER-Net observations report
  66. GRB 251028A: Fermi GBM Observation
  67. GRB 251026B: LBT near-infrared observations
  68. GRB 251028B: Fermi/GBM observation
  69. GRB 251028B: Glowbug gamma-ray detection
  70. GRB 251028A: Glowbug gamma-ray detection
  71. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  72. Fermi GRB 251028B: Global MASTER-Net observations report
  73. GRB 251028B: Fermi GBM Final Localization Correction
  74. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  75. GRB 251028A: MAXI/GSC detection
  76. GRB 251028A: Fermi GBM Final Real-time Localization
  77. The EP-WXT trigger 01709247525 is not a real source
  78. EP251023b: Global MASTER-Net observations report
  79. Fermi GRB 251023A: Global MASTER-Net observations report
  80. EP/WXT 01709247295: GOTO optical afterglow candidate.
  81. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  82. EP251021b: Einstein Probe detection of a fast X-ray transient
  83. IceCube-251018A: Global MASTER-Net observations report
  84. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  85. Fermi GRB 251016B: Global MASTER-Net observations report
  86. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  87. sb25101602: Swift-XRT counterpart detection
  88. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  89. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  90. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  91. GRB 251014A: Fermi GBM Observation
  92. GRB 251014A: Swift detection of a possibly-short burst
  93. GRB 251014A: Fermi GBM Final Real-time Localization
  94. Fermi GRB 251013C: Global MASTER-Net observations report
  95. Fermi GRB 251013B: Global MASTER-Net observations report
  96. Fermi GRB 251011A: Global MASTER-Net observations report
  97. GRB 250919A: TERI gamma-ray detection
  98. Fermi GRB 251006B: Global MASTER-Net observations report
  99. GRB 251005C: AstroSat CZTI detection
  100. GRB 251003A: Swift-BAT refined analysis

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