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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"

31635 results found.

  1. EP250223a: J band upper limit by SYSU 80cm telescope
  2. EP250228a: Swift/XRT localisation
  3. EP250228a: Global MASTER-Net observations report
  4. GRB 250226A / EP250226a: LCO detection of the afterglow
  5. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  6. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  7. GRB 250225B: VLT/Xshooter imaging
  8. GRB 250205A / EP250205A: further radio observations with the VLA
  9. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  10. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  11. GRB 250225B: INTEGRAL SPI-ACS detection
  12. EP250225a: NOT optical candidate counterpart
  13. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  14. EP250226a / GRB 250226A: SVOM/VT optical observations
  15. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  16. EP250225a: TRT optical upper limits
  17. EP250226a/GRB 250226A: 1.6m Mephisto observations
  18. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  19. EP250226a/GRB 250226A: Kinder optical follow-up observations
  20. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  21. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  22. Fermi GRB 250226B: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  24. GRB 250225B: Fermi GBM Observation
  25. GRB 250221A: ATCA Detections and Upper Limits
  26. GRB 250225B: REM NIR upper limits
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  28. Konus-Wind detection of GRB 250225B
  29. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  30. EP250223a: CrAO ZTSH optical observation
  31. GRB 250225B: VLT optical and near-infrared candidate counterpart
  32. GRB 250225B: VLT/FORS2 candidate optical afterglow
  33. GRB 250225B: SVOM/GRM observation of a long burst
  34. GRB 250226A: GECAM-B detection
  35. GRB 250221A: EP-FXT detection of the X-ray afterglow
  36. GRB 250214A: SVOM/GRM observation
  37. EP250226a/GRB 250226A: GSP detects optical counterpart
  38. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  39. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  40. EP250226a / GRB 250226A: TRT optical counterpart observation
  41. EP250226a: Global MASTER-Net observations report
  42. Swift GRB 250225B: Global MASTER-Net observations report
  43. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  44. Fermi GRB 250226A: Global MASTER-Net observations report
  45. EP250225a: Global MASTER-Net observations report
  46. EP250225a: GSP optical upper limit
  47. EP250223a: GMG Optical Observation
  48. Fermi GRB 250225A: Global MASTER-Net observations report
  49. EP250223a: GROWTH-India Telescope optical observations
  50. GRB 250221A: Swift-BAT refined analysis
  51. GRB 250223C: SVOM/GRM observation of a long burst
  52. EP250215A: J band upper limit by SYSU 80cm telescope
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  55. EP250223a: Kinder optical follow-up observations
  56. GRB 250207a: ATCA Radio Upper Limits
  57. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  58. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  59. GRB 250119B: VZLUSAT-2 detection
  60. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  61. GRB 250202B: VZLUSAT-2 detection
  62. GRB 250219A: EP-FXT afterglow detection
  63. EP250223a: GOTO optical afterglow detections
  64. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  65. GRB 250210A: VZLUSAT-2 detection
  66. GRB 250206A: VZLUSAT-2 detection
  67. EP250223a: REM NIR upper limit
  68. EP250223a: TRT optical afterglow observation
  69. EP250223a: refined analysis of the EP-WXT and FXT observations
  70. EP250223a: 1.6m Mephisto and 50cm array observations
  71. GRB 250221A: TNOT detection of the optical counterpart
  72. EP250223a: SVOM/VT optical observation
  73. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  75. EP250223a: OASDG optical observations
  76. EP250223a: LCO detection of the afterglow
  77. EP250223a: NOT redshift z = 2.756
  78. EP250223a: Swift/XRT localization
  79. EP250223a: NOT optical afterglow candidate
  80. EP250223a: Global MASTER-Net observations report
  81. GRB 250221A: VLA radio detection
  82. Fermi GRB 250223A: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  84. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  85. GRB 250221A: continued Mondy optical observations, brightening afterglow
  86. GRB 250221A: Optical counterpart detection by LCO.
  87. GRB 250221A: Mondy optical observations
  88. Konus-Wind detection of GRB 250221A
  89. GRB 250221A: Assy optical observations
  90. EP250220a: FTW optical and NIR observations and upper limits
  91. EP250220a: EP-FXT follow-up observations
  92. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  93. GRB 250221A: VLT/X-shooter redshift z = 0.768
  94. GRB 250221A: GRANDMA/TAROT Detection
  95. GRB 250221A: NOT optical observations
  96. GRB 250221A: 1.6m Mephisto optical detection
  97. GRB 250221A: AKO Optical Upper Limit
  98. GRB 250221A: Swift/UVOT Detection
  99. EP250220a: Liverpool Telescope upper limits
  100. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits

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