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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"

31634 results found.

  1. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  2. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  3. LIGO/Virgo/KAGRA S241230bd: Updated Sky localization
  4. GRB 241229A: EP-FXT X-ray afterglow confirmation
  5. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  6. GRB 241229B: SVOM/GRM observation
  7. LIGO/Virgo/KAGRA S241231bg: Identification of a GW compact binary merger candidate
  8. EP241217A: J band upper limit by SYSU 80cm telescope
  9. LIGO/Virgo/KAGRA S241230ev: Identification of a GW compact binary merger candidate
  10. GRB 241229B: SAO RAS optical upper limit
  11. GRB 241228B: SAO RAS optical observations
  12. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  13. GRB 241229A: SAO RAS optical observations
  14. GRB 241229B: SVOM/VT optical candidate
  15. GRB 241229A: Swift-XRT observations
  16. Konus-Wind detection of GRB 241228A
  17. GRB 241229A: EP-FXT afterglow candidates
  18. EP240702a: 7DT Optical upper limits
  19. GRB 240606B: 7DT Optical upper limits
  20. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  21. GRB 241229B: Swift-BAT refined analysis
  22. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  23. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  24. GRB241229B: UVOT upper limits
  25. GRB 241228B: D50 optical detection
  26. GRB 241228B: Fermi GBM Observation
  27. GRB 241229B: Fermi GBM Observation
  28. GRB 241229A: Swift ToO observations
  29. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  30. GRB 241228A: Mondy optical afterglow observations
  31. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  32. Swift GRB 241229B: Global MASTER-Net observations report
  33. GRB 241229A: GOTO optical upper limits
  34. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  35. GRB 241228A: NOT optical upper limits
  36. GRB 241228B: LCO optical observation
  37. GRB 241228A: Swift-BAT refined analysis
  38. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  39. Fermi GRB 241228B: Global MASTER-Net observations report
  40. GRB 241228A: Fermi GBM Observation
  41. GRB241228B: GROWTH-India Telescope optical observations
  42. Swift GRB 241228A: Global MASTER-Net observations report
  43. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  44. GRB 241228B: GOTO24jmz optical follow-up observations
  45. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 241228A: GROWTH-India telescope optical upper limit
  47. GRB 241228B: Swift ToO observations
  48. GRB 241228B: TRT optical counterpart confirmation
  49. GRB 241228A: Swift/UVOT Upper Limits
  50. GRB 241228B: GOTO possible optical counterpart candidate
  51. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 241223A: GRBAlpha detection
  53. GRB 241212A: VZLUSAT-2 detection
  54. GRB 241217A/EP241217b: continued SOAR observations
  55. Fermi GRB 241226A: Global MASTER-Net observations report
  56. EP241223a: Mondy AZT-33IK optical observations
  57. GRB 241029A: LCO optical observation
  58. GRB 241223A: Swift-XRT observations
  59. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  60. GRB 241029A: AbAO AS-32 optical observations
  61. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  62. EP241223a
  63. EP241223a: Global MASTER-Net observations report
  64. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  65. GRB241113A: 7DT Optical upper limits
  66. Fermi GRB 241223A: Global MASTER-Net observations report
  67. GRB 241223A: GOTO optical observations summary
  68. GRB 241105A: JWST photometric observations of the host galaxy
  69. GRB 241223A: Swift ToO observations
  70. EP241217a: e-MERLIN radio observations
  71. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  72. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  73. Fermi GRB 241221A: Global MASTER-Net observations report
  74. GRB 241217A/EP241217b: SOAR afterglow detection
  75. EP241217a: Liverpool Telescope optical upper limit
  76. EP241021a: VLA radio detection
  77. GRB 241218A: Mondy AZT-33IK optical upper limit
  78. EP241217a : Leavitt Observatory optical upper limit
  79. GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
  80. EP241217a: 1.6m Mephisto multi-band optical observations
  81. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  82. GRB 241218A: Swift/UVOT Upper Limits
  83. EP241217a: optical upper limit with the Liverpool Telescope
  84. GRB 241209B: EP-FXT afterglow detection
  85. Konus-Wind detection of GRB 241204A (short/hard)
  86. GRB 241218A: NOT optical upper limits
  87. GRB 241218A: Swift-BAT refined analysis
  88. GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
  89. EP 241217a: NIR detection with P200/WIRC
  90. EP 241217a: Possible J-band detection with WINTER
  91. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  92. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  93. GRB 241217A / EP241217b: Nanshan/HMT optical upper limit
  94. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  95. GRB 241217A / EP241217b: NOT optical upper limits
  96. GRB 241218A: REM optical upper limit
  97. GRB 241217A/EP241217b: REM optical/NIR upper limits
  98. EP241217a: REM optical/NIR upper limits
  99. GRB 241218a: Liverpool Telescope optical follow-up
  100. GRB 241217a: Liverpool Telescope optical follow-up

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