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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"

8293 results found.

  1. GRB 250103A: Swift ToO observations
  2. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 250103B: Swift detection of a burst
  4. GRB 250103A: Xinglong 2.16m Optical Candidate
  5. GRB 250103A: GOTO optical upper limit
  6. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  7. GRB 250103A: SVOM detection of a long burst
  8. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  9. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  10. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  11. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  12. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  13. GRB 250101A: Swift detection of a burst with an optical counterpart
  14. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  15. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  17. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  18. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  19. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume
  20. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  21. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  23. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  24. GRB 241229A: SAO RAS optical observations
  25. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 241229B: SVOM/VT optical candidate
  27. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  29. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  30. GRB 241229A: Swift ToO observations
  31. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  32. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  33. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  34. GRB 241228B: GOTO24jmz optical follow-up observations
  35. GRB 241228B: Swift ToO observations
  36. GRB 241228B: TRT optical counterpart confirmation
  37. GRB 241228B: GOTO possible optical counterpart candidate
  38. GRB 241228A: Swift detection of a burst
  39. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  40. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  41. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  42. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  43. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  44. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  45. GRB 241223A: Swift ToO observations
  46. EP241217a: 1.6m Mephisto multi-band optical observations
  47. EP241217a: optical upper limit with the Liverpool Telescope
  48. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  49. GRB 241218A: Swift detection of a burst
  50. GRB 241217A: LCO optical upper limit
  51. GRB 241217A: GRANDMA/TAROT optical upperlimits
  52. EP241217A: Non-detection from Fermi-GBM Observations
  53. GRB 241217A : SVOM/ECLAIRs,GRM,MXT detection of a long burst with a bright X-ray afterglow candidate
  54. EP241217a: Kinder optical follow-up observations
  55. GRB 241215A: Mondy AZT-33IK optical observations
  56. The EP-WXT trigger 01709128948 is likely a flaring star
  57. GRB 241215A: Montarrenti Observatory optical upper limit
  58. GRB 241213A: SVOM/VT optical candidate
  59. GRB 241213B: Tiled Swift observations
  60. GRB 241212A: Swift ToO observations
  61. LIGO/Virgo/KAGRA S241210fu: Updated Sky localization
  62. GRB 241213A: Swift detection of a burst
  63. GRB 241209B: GRANDMA/TRT upper limit
  64. GRB 241207A: TSHAO Zeiss-1000 optical observations
  65. GRB 241209A: Redshift of the likely host galaxy z = 0.784 from OSIRIS+/GTC
  66. LIGO/Virgo/KAGRA S241210cw: Updated Sky localization
  67. LIGO/Virgo/KAGRA S241210d: Updated Sky localization and EM Bright Classification
  68. LIGO/Virgo/KAGRA S241210fu: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
  71. GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
  72. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  73. GRB 241209A: GRANDMA/TAROT upper limit
  74. GRB 241209B: Swift ToO observations
  75. GRB 241209A: VLT/X-shooter spectroscopy
  76. GRB 241209B: SVOM/ECLAIRs and GRM detection of a long burst
  77. GRB 241209A: Swift detection of a short burst
  78. GRB 241207C: Tiled Swift observations
  79. EP241201a: 1.6m Mephisto Optical Upper Limits
  80. EP241202b: KAIT optical upper limit
  81. LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  82. EP241202b: Upper limits from Fermi-GBM Observations
  83. EP241202b: Kinder optical counterpart candidate
  84. Fermi-GBM Sub-Threshold Detection of GRB 241128A
  85. Konus-Wind detection of GRB 241130A
  86. EP241201a: NOT optical observations
  87. GRB 241130A: EIRSAT-1 GMOD Detection
  88. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  89. EP241201a: Kinder optical counterpart candidate
  90. LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
  91. LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
  92. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S241130be: Updated Sky localization
  94. LIGO/Virgo/KAGRA S241130n: Updated Sky localization
  95. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  96. LIGO/Virgo/KAGRA S241127aj: Updated Sky localization
  97. LIGO/Virgo/KAGRA S241130be: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S241129aa: Updated Sky localization
  99. LIGO/Virgo/KAGRA S241130n: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S241129aa: Identification of a GW compact binary merger candidate

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