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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"

3300 results found.

  1. GRB 260807A: EP-FXT follow-up observations
  2. GRB 260822A: EP/FXT follow-up observations
  3. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  4. EP260822a: EP-FXT non-detection and upper limit
  5. EP260822a: Einstein Probe detection of a fast X-ray transient
  6. The EP-WXT trigger 01709287395 is likely a flaring star
  7. GRB 260818B: SVOM/C-GFT optical upper limit
  8. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  9. The EP-WXT trigger 01709286204 is likely a flaring star
  10. EP detected a brightening of LMXB 1ES 1735-26.9
  11. GRB 260818B: EP-FXT follow-up observation
  12. GRB 260818A: J-band observations with WINTER
  13. GRB260818A: EP-FXT follow-up observation
  14. EP260806a: SAO RAS multicolor optical observations
  15. EP260806a: SVOM/ECLAIRs detection through targeted search
  16. The EP-WXT trigger 01709281429 is likely a flaring star
  17. EP260812a: AZT-22 optical upper limit
  18. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  19. EP260806a: WFST optical observations
  20. The EP-WXT trigger 01709280562 is likely a flaring star
  21. EP260812b: Optical upper limit with Kinder
  22. The EP-WXT trigger 01709279838 is likely a flaring star
  23. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  24. EP260812a: SVOM/C-GFT optical upper limit
  25. EP260812b: SVOM/VT optical observation
  26. EP260812b: Einstein Probe detection of an X-ray transient
  27. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  28. EP260812a: Einstein Probe detection of an X-ray transient
  29. GRB 260809A: SAO RAS optical observations
  30. GRB 260808B: SAO RAS optical observations
  31. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  32. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  33. The EP-WXT trigger 01709278015 is likely a flaring star
  34. EP260809a: J-band upper limit with WINTER
  35. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  36. EP260809a: LCO optical observation
  37. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  38. EP260809a: Einstein Probe detection of an X-ray transient
  39. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  40. EP260806a: SVOM/VT optical observation
  41. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  42. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  43. EP260806a: LCO likely optical counterpart
  44. EP260806a: Einstein Probe detection of an X-ray transient
  45. SN 2026stf / GRB 260708A: ATLAS forced photometry
  46. AT 2026wki: EP/FXT follow-up observations
  47. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  48. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  49. GRB 260802A: SVOM/VT optical upper limits from VHF data
  50. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. The EP-WXT trigger 01709277420 is likely a flaring star
  52. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  53. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  54. EP260731a: COLIBRÍ optical upper limit
  55. EP260731a: NOT optical upper limit
  56. EP260731a: Einstein Probe detection of an X-ray transient
  57. EP260728a: COLIBRÍ optical upper limit
  58. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  59. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  60. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  61. EP260729a: Einstein Probe detection of an X-ray transient
  62. EP260727a: SAO RAS optical observations
  63. GRB 260727A: AbAO and SAO RAS optical observations
  64. EP260728a: EP-FXT follow-up observation
  65. GRB 260726A: EP-FXT follow-up observations
  66. EP260728a: Einstein Probe detection of a fast X-ray transient
  67. GRB 260727A: SVOM/GRM observation
  68. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  69. Konus-Wind detection of GRB 260727A
  70. EP260727a: NUTTELA-TAO Early Optical Limits
  71. GRB 260727A: EP/FXT follow-up observations
  72. EP260727a: Einstein Probe detection of an X-ray transient
  73. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  74. EP260723a: SVOM/ECLAIRs Upper Limit
  75. EP260723a: further EP-FXT follow-up observation
  76. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  77. EP260725a: EP-WXT detection of an X-ray transient
  78. EP260723a: EP-FXT follow-up observation
  79. EP260723a: SVOM/VT optical observation
  80. EP260723a: NOT optical conterpart confirmation
  81. EP260723a: Liverpool Telescope likely optical counterpart
  82. EP260723a: EP-WXT detection of a fast X-ray transient
  83. Konus-Wind detection of GRB 260721A
  84. Konus-Wind detection of GRB 260714B
  85. GRB 260718A: EP-FXT follow-up observation
  86. GRB 260618B: EP-FXT follow-up observation upper limit
  87. EP260703a: SVOM/ECLAIRs Upper Limit
  88. GRB 260706A: ATCA detection of possible radio counterpart
  89. EP260713a: Einstein Probe detection of an X-ray transient
  90. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  91. EP260711a: EP-FXT follow-up observation
  92. EP260711a: Einstein Probe detection of an X-ray transient
  93. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg
  94. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  95. GRB 260704A: SVOM/ECLAIRs refined analysis
  96. GRB 260706A : GRANDMA Upper limits
  97. GRB 260706A: Further EP-FXT follow-up observation
  98. GRB 260706A: SVOM/VT optical upper limits
  99. EP260707a (by EP-FXT): NOT optical upper limit
  100. EP260707a is not a real source

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