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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32689 results found.

  1. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  2. GRB 251125B: GECAM-B detection
  3. Fermi GRB 251127A: Global MASTER-Net observations report
  4. GRB 251126A: Kilonova-Catcher optical afterglow detection
  5. GRB 251126A: Asiago i-band detection
  6. GRB 251126A: Nanshan/HMT optical afterglow detection
  7. Swift GRB 251126A: Global MASTER-Net observations report
  8. GRB 251121A: Fermi GBM Observation
  9. GRB 251126A: GIT discovery of the likely optical afterglow
  10. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  11. EP251124b follow-up observation by EP-FXT
  12. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  13. EP251124b: NOT r- and z-band optical upper limits
  14. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  15. Fermi GRB 251125B: Global MASTER-Net observations report
  16. EP251124b: Global MASTER-Net observations report
  17. EP251124a: Xinglong GWAC-F60A optical observation
  18. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  19. Fermi GRB 251125A: Global MASTER-Net observations report
  20. EP251124a: NOT r- and z-band optical upper limits
  21. EP251124a: Global MASTER-Net observations report
  22. GRB 251124A: Fermi GBM Localization by automated pipeline
  23. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  24. EP251124a: Optical upper limit with Kinder observations
  25. EP251118A: 6 GHz VLA Detection
  26. Fermi GRB 251124a: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  28. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  29. EP251124a: GROWTH-India Telescope optical upper limits
  30. GRB 251116C: Swift-XRT confirmation of fading
  31. GRB 251122A/EP251122a: FTW optical and NIR observations
  32. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  33. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  34. EP251118A: 3.6m DOT optical afterglow detection
  35. GRB 251122A / EP251122a: EP-FXT counterpart detection
  36. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 251122A / EP251122a: WFST optical observations
  38. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  39. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  40. GRB 251122A / EP251122a: LCO optical upper limits
  41. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  42. EP251122a: Global MASTER-Net observations report
  43. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  44. GRB 251122A / EP251122a: SVOM detection of a long burst
  45. EP251118a: Continued Optical Detection with Kinder observations
  46. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  47. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  48. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  49. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  50. EP251118a: Xinglong-2.16m optical observation
  51. GRB 251115A: Fermi GBM Observation
  52. EP251118A: 1.3m DFOT optical afterglow detection
  53. GRB 251118A: Swift/UVOT Detection
  54. EP251118a / GRB 251118C: SAO RAS optical observations
  55. GRB 251118A: Glowbug gamma-ray detection
  56. GRB 251118A: Fermi GBM Observation
  57. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  58. EP251118a: Optical detection with Kinder observations
  59. GRB 251118A: GECAM-B detection
  60. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  61. EP251118a / GRB 251118C: SVOM/VT optical observation
  62. GRB 251118A: NuSTAR detection of bright prompt emission
  63. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  64. GRB 251116C: NOT optical observations
  65. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  66. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  67. EP251118A / GRB 251118C : MASTER optical counterpart observations
  68. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  69. Konus-Wind detection of GRB 251118C (EP251118a)
  70. EP251118a: FTW optical and NIR observations
  71. GRB 251117A: Insight-HXMT/HE detection
  72. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  73. EP251118a: VLT near-infrared observation
  74. GRB 251116D: SVOM/GRM observation of a long GRB
  75. EP251118a: GOTO optical afterglow detection
  76. EP251118a: NOT spectroscopic redshift of z = 1.216
  77. EP251118a: Global MASTER-Net observations report
  78. EP251118a: preliminary result of EP-FXT follow-up observation
  79. GRB 251118A: Fermi-LAT detection
  80. EP251118a: NOT candidate optical counterpart
  81. GRB 251118A: Swift ToO observations
  82. EP251118a: Einstein Probe detected of a fast X-ray transient
  83. Fermi GRB 251118B: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  85. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  86. GRB 251116C: SVOM/ECLAIRs refined analysis
  87. GRB 251116B: SVOM/ECLAIRs refined analysis
  88. GRB 251117A: AstroSat CZTI detection
  89. GRB 251114B: Insight-HXMT/HE detection
  90. GRB 251114B: GECAM-B detection of a short burst
  91. GRB 251117A: Fermi GBM observation
  92. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  93. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  94. GRB 251116D: Insight-HXMT/HE detection
  95. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  96. GRB 251117A: SVOM/GRM observation of a short burst
  97. GRB 251117A: Tiled Swift observations
  98. GRB 251117A: Fermi-LAT detection
  99. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  100. GRB 251116C: Swift/BAT arcminute localization of a burst

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