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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"

3296 results found.

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

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