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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"

31737 results found.

  1. EP250108a: NOT optical observations
  2. GRB 250109a: GMG Optical Upper Limit
  3. EP250109a: Swift/UVOT non-detection
  4. Konus-Wind detection of GRB 250107D (short/hard)
  5. IPN triangulation of GRB 250107D (short/hard)
  6. IPN triangulation of GRB 250107C
  7. EP250108a: Liverpool Telescope likely optical counterpart
  8. GRB 250108B: Gemini-North likely redshift z = 2.197
  9. GRB 250108B: Swift-BAT refined analysis
  10. GRB 250108B: 1.3m DFOT upper limit
  11. GRB 250108B: REM optical/NIR upper limits
  12. GRB 250109A /EP250109a: Fermi GBM Final Localization
  13. EP250109a: SVOM/VT optical candidate
  14. EP250109a: Global MASTER-Net observations report
  15. GRB 250101A: Terskol K-800 optical observations
  16. EP250109a: GOTO optical upper limits
  17. EP250109a: Swift/XRT non-detection
  18. GRB 250108A: Swift/UVOT Upper Limits
  19. EP250108a: Global MASTER-Net observations report
  20. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  21. GRB 250108A: NOT optical upper limit
  22. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  23. Swift GRB 250108B: Global MASTER-Net observations report
  24. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  25. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  26. GRB 250103A: 1.6m Mephisto optical observations
  27. GRB 250108A:SVOM/VT optical candidate
  28. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  29. GRB 250108B: Swift/UVOT Upper Limits
  30. GRB 250108A: Swift ToO observations
  31. GRB 250107A: Fermi GBM Observation
  32. GRB 241228B: Fermi-LAT detection
  33. Fermi GRB 250107B: Global MASTER-Net observations report
  34. GRB 250107A: Swift ToO observations
  35. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  36. GRB 250106A: SVOM/VT 2nd optical deep observation
  37. GRB 250101A: J band upper limit by SYSU 80cm telescope
  38. GRB 250106A: NOT optical observations
  39. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  40. GRB 250103B: REM optical/NIR upper limits
  41. GRB 250101A: REM optical/NIR counterpart detection
  42. GRB 250106A: Swift-XRT observations
  43. GRB 250106A: SVOM/VT optical candidate
  44. GRB 250106A: Swift ToO observations
  45. GRB 241229A: SVOM/VT optical upperlimit
  46. GRB 250103B: LCO/1m optical afterglow candidate detection
  47. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  48. GRB 250103A: Swift-XRT observations
  49. GRB 250101A: 1.3m DFOT optical afterglow detection
  50. GRB 241229A: 1.3m DFOT upper limit
  51. GRB 241228B: 1.3m DFOT Optical observations
  52. GRB 241228A: 1.3m DFOT upper limit
  53. GRB 250103A: NOT spectroscopic redshift
  54. GRB 250103B：SVOM/VT optical counterpart
  55. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  56. GRB 250103A: Montarrenti Observatory optical detection
  57. GRB 250101A: further LCOGT optical afterglow observations
  58. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  59. GRB 250103A: NOT optical observations
  60. GRB 250103A: TSHAO optical upper limit
  61. GRB 250103A: Fermi GBM Observation
  62. GRB 250103B: LCOGT Optical Upper Limit
  63. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  64. Swift GRB 250103B: Global MASTER-Net observations report
  65. GRB 250103A: SVOM/VT optical counterpart confirmation
  66. EP250101a: Liverpool Telescope optical upper limit
  67. GRB 250103A: Swift ToO observations
  68. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 250101a: Liverpool Telescope optical follow-up
  70. GRB 250103B: SVOM detection of a long burst
  71. GRB 250103A: Xinglong 2.16m Optical Candidate
  72. Fermi GRB 250102A: Global MASTER-Net observations report
  73. GRB 250101B: SVOM/GRM observation
  74. GRB 250103A: GOTO optical upper limit
  75. GRB 250103A: SVOM/C-GFT optical upper limit
  76. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  77. EP241231b: optical upper limit with the Liverpool Telescope
  78. EP250101a: Xinglong optical upper limit
  79. GRB 250101A: Swift-BAT refined analysis
  80. GRB 250101A: further SAO RAS optical observations
  81. GRB 250101A: LCO optical counterpart detection
  82. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  83. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  84. GRB 250101A: Swift/UVOT Detection
  85. GRB 250101A: 1.6m Mephisto multi-band optical followup
  86. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  87. GRB 250101A: LCOGT optical afterglow detection
  88. GRB 250101A: OASDG optical observations
  89. Fermi GRB 250101B: Global MASTER-Net observations report
  90. GRB 250101A: SAO RAS observations of optical brightening
  91. GRB 250101A: AKO Optical Afterglow Detection
  92. GRB 250101A: SAO RAS optical observations
  93. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  94. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  95. GRB 250101A: SVOM/C-GFT early optical observations
  96. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  97. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  98. GRB 250101A: Nanshan/HMT optical observations
  99. GRB 250101A : GIT optical detection
  100. GRB 250101A: GMG Optical Observation

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