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J/ApJ/694/425        A Chandra X-ray observation of L1251B         (Simon, 2009)

A Chandra X-ray observation of L1251B. Simon T. <Astrophys. J., 694, 425-437 (2009)> =2009ApJ...694..425S
ADC_Keywords: Molecular clouds ; X-ray sources ; Photometry, infrared Keywords: ISM: Herbig-Haro objects - ISM: individual (L1251, HH 189) - stars: formation - stars: pre-main sequence - X-rays: stars Abstract: I report the results of a 60ks X-ray observation of the L1251 dark cloud in Cepheus, which was acquired with the ACIS-I camera on board the Chandra X-Ray Observatory. Forty-three compact X-ray sources were detected. The field of view was centered on the position of IRAS 22376+7455, an embedded Class 0/I protostar that is closely associated with the bright CO emission core, L1251B-Core E. A very intense impulsive X-ray flare was observed from a location within the formal error ellipse of the IRAS source and in close proximity (within ≲1") to a thermal continuum radio source, VLA 3. Given their small spatial offsets, the radio, far-infrared, and X-ray objects appear to be identical and consequently the likely origin and driving source of high-velocity gas flows that are observed in L1251B. Description: L1251 was observed with the imaging array of the ACIS CCD camera on Chandra (ACIS-I) on 2007 August 10 (obsID A8588) and 11 (obsID B7415). The observation was split into two exposure segments, each 29.6ks long and separated in time by a gap of 17.6hr. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 136 43 X-ray detections in L1251B
See also: B/chandra : The Chandra Archive Log (CXC, 1999-) J/A+A/272/235 : Stars in the dark cloud L1251 (Kun+ 1993) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 I2 --- CXO CXO source number (<[S2009b] CXO NN> in Simbad) 4- 5 I2 h RAh Hour of right ascension (J2000) 7- 8 I2 min RAm Minute of right ascension (J2000) 10- 14 F5.2 s RAs Second of right ascension (J2000) 16 A1 --- DE- Declination sign (J2000) 17- 18 I2 deg DEd Degree of declination (J2000) 20- 21 I2 arcmin DEm Arcminute of declination (J2000) 23- 26 F4.1 arcsec DEs Arcsecond of declination (J2000) 28- 30 F3.1 arcmin theta Off-axis angle (1) 32- 55 A24 --- OName Identification(s) 56- 57 I2 --- [S2006] ? Corresponding XMM source number from Table 1 of Paper I (Simon T., 2006AJ....131..501S) 59- 62 F4.2 arcsec off ? Angular offset between the position of each Chandra X-ray source and its XMM counterpart 64- 67 F4.2 arcsec Rad Radius of extraction cell (2) 69- 73 F5.2 ks Texp Effective exposure time (3) 75- 79 F5.2 ct/ks CR1 ? Background-corrected source count rate in the (0.3-10.0)keV energy band on August 10 (4) 81- 84 F4.2 ct/ks e_CR1 ? CR1 uncertainty 85 A1 --- f_CR1 [h] Source detected in combined observation (5) 87- 91 F5.2 ct/ks CR2 ? Background-corrected source count rate in the (0.3-10.0)keV energy band on August 11 (4) 93- 96 F4.2 ct/ks e_CR2 ? CR2 uncertainty 98-114 A17 --- 2MASS 2MASS identification (JHHMMSSss+DDMMSSs) 116 A1 --- f_2MASS [i] large offset from X-ray (6) 118-123 F6.3 mag Ksmag ? 2MASS Ks-band magnitude (7) 125 A1 --- l_J-H Limit flag on J-H 126-130 F5.3 mag J-H ? 2MASS J-H color index (7) 132-136 F5.3 mag H-Ks ? 2MASS H-Ks color index (7)
Note (1): From the aim point of the observation (J223839.42+751130.8). Note (2): Radius of extraction cell corresponding to 90% encircled energy fraction (EEF) in the PSF at the location of the source on the ACIS array. Note (3): Effective exposure time for each subexposure based on exposure maps computed for an energy of 1.5keV, which account for the change in camera sensitivity across the field of view. The effective exposure time is used to compute the source count rate. Note (4): Corrected to 100% encircled energy fraction. Background counts were typically measured through an annular aperture centered on the source, having inner and outer radii equal to four and eight times the 90% EEF radius, respectively. In a few cases, the background was determined from an adjacent circular extraction cell with a radius equal to eight times the size of the 90% EEF radius. The cited errors are statistical only. The count rates in the two subexposures were significantly different at the ≥5σ level for the following sources: 7, 8, 12, 19, 26, 32, and 41. Note (5): h = Source formally detected at ≥3σ level in the combined observation only. Count rate determined from the merged data set. Note (6): i = Large offset from X-ray position. See Section 4.1 and Table 4. Note (7): Broadband photometry converted to CIT system using the transformations given by Carpenter (2001).
History: From electronic version of the journal References: Simon T. Paper I. 2006AJ....131..501S
(End) Emmanuelle Perret [CDS] 18-Mar-2011
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