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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"

16997 results found.

  1. EP251030a: COLIBRÍ optical counterpart candidate
  2. EP251130a: Einstein Probe detection of an X-ray transient
  3. EP251129a/GRB 251129A: EP-FXT follow-up observations
  4. GRB 251129A / EP251129a: SAO RAS optical observations
  5. GRB 251126A: SAO RAS optical observations
  6. GRB 251128A: SVOM/GRM observation of a long burst
  7. SVOM GRB 251129A : MASTER optical counterpart detection
  8. GRB 251129A: Swift-XRT afterglow detection
  9. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  10. GRB 251129A: SVOM/VT optical fading
  11. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  12. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  13. GRB 251129A: SVOM detection of a burst
  14. SVOM GRB251129.11: Global MASTER-Net observations report
  15. GRB 251129A: SVOM detection of a burst
  16. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  17. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 251126A: further SAO RAS optical observations
  19. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  20. GRB251126A: MAO/AZT-22 optical observations
  21. GRB251126A: Continued optical observation from 1.3m DFOT
  22. GRB 251126A: Swift/UVOT Detection
  23. GRB 251126A: Mondy and SAO RAS optical observations
  24. GRB 251126A: Swift-XRT refined Analysis
  25. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  26. GRB 251126A: 1.3m DFOT optical afterglow detection
  27. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  28. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  29. GRB 251126A: Enhanced Swift-XRT position
  30. GRB 251126A: Kilonova-Catcher optical afterglow detection
  31. GRB 251126A: Nanshan/HMT optical afterglow detection
  32. GRB 251126A: GIT discovery of the likely optical afterglow
  33. GRB 251126A: Swift detection of a burst
  34. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  35. EP251124b follow-up observation by EP-FXT
  36. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  37. EP251124b: NOT r- and z-band optical upper limits
  38. EP251124b: EP-WXT detection of a fast X-ray transient
  39. EP251124a: Xinglong GWAC-F60A optical observation
  40. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  41. EP251124a: NOT r- and z-band optical upper limits
  42. EP251124a: Swift-XRT observations
  43. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  44. EP251124a: Optical upper limit with Kinder observations
  45. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  46. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  47. EP251124a: GROWTH-India Telescope optical upper limits
  48. EP251124a: Einstein Probe detection of an X-ray transient
  49. GRB 251116C: Swift-XRT confirmation of fading
  50. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  51. The EP-WXT trigger 01709248783 is likely a flaring star
  52. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  53. EP251118A: 3.6m DOT optical afterglow detection
  54. GRB 251122A / EP251122a: EP-FXT counterpart detection
  55. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 251122A / EP251122a: WFST optical observations
  57. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  58. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  59. GRB 251122A / EP251122a: LCO optical upper limits
  60. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  61. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  62. GRB 251122A / EP251122a: SVOM detection of a long burst
  63. EP251122a: Einstein Probe detection of an X-ray transient
  64. EP251118a: Continued Optical Detection with Kinder observations
  65. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  66. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  67. EP251118a: Xinglong-2.16m optical observation
  68. The EP-WXT trigger 01709248635 is likely a flaring star
  69. EP251118A: 1.3m DFOT optical afterglow detection
  70. GRB 251118A: Swift/UVOT Detection
  71. EP251118a / GRB 251118C: SAO RAS optical observations
  72. GRB 251118A: Swift-XRT afterglow detection
  73. EP251118a: Optical detection with Kinder observations
  74. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  75. The EP-WXT trigger 01709248403 is likely a flaring star
  76. GRB 251118A: NuSTAR detection of bright prompt emission
  77. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  78. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  79. GRB 251117A: Swift-XRT observations
  80. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  81. The EP-WXT trigger 01709248388 is likely a flaring star
  82. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  83. EP251118a: VLT near-infrared observation
  84. GRB 251116D: SVOM/GRM observation of a long GRB
  85. GRB 251119A: SVOM detection of a possible burst
  86. EP251118a: preliminary result of EP-FXT follow-up observation
  87. EP251118a: NOT candidate optical counterpart
  88. EP251118a: Einstein Probe detected of a fast X-ray transient
  89. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  90. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  91. GRB 251117A: SVOM/GRM observation of a short burst
  92. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  94. EP251023a: Assy AZT-20 optical observations
  95. EP251023a: UAFO and AbAO optical observations
  96. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  97. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  98. GRB 251025B: further Mondy optical observations
  99. GRB 251111A: Mondy optical upper limit
  100. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate

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